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Philip Wai Hong Chan - One of the best experts on this subject based on the ideXlab platform.
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synthesis of z 1 2 dihydro 1 tosylbenzo b azepin 3 ones by two step one pot gold catalyzed tandem heterocyclization petasis ferrier Rearrangement of 2 n prop 2 ynyl n tosylamino benzaldehydes
Tetrahedron, 2013Co-Authors: Ella Min Ling Sze, Ming Joo Koh, Yen Min Tjia, Weidong Rao, Philip Wai Hong ChanAbstract:Abstract A two-step, one-pot synthetic method that relies on gold(I)-catalyzed tandem heterocyclization/Petasis–Ferrier Rearrangement and Bronsted acid-assisted debenzoxylation of 2-(N-(prop-2-ynyl)-N-tosylamino)benzaldehydes to prepare (Z)-1,2-dihydro-1-tosylbenzo[b]azepin-3-ones efficiently is reported. The reactions proceed rapidly under mild and operationally straightforward conditions for a wide variety of aldehyde substrates containing electron-withdrawing, electron-donating, and sterically demanding functional groups and afforded the corresponding benzo-fused azaheterocyclic products in moderate to excellent yields.
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Synthesis of (Z)-1,2-dihydro-1-tosylbenzo[b]azepin-3-ones by two-step, one-pot gold-catalyzed tandem heterocyclization/Petasis–Ferrier Rearrangement of 2-(N-(prop-2-ynyl)-N-tosylamino)benzaldehydes
Tetrahedron, 2013Co-Authors: Ella Min Ling Sze, Ming Joo Koh, Yen Min Tjia, Weidong Rao, Philip Wai Hong ChanAbstract:Abstract A two-step, one-pot synthetic method that relies on gold(I)-catalyzed tandem heterocyclization/Petasis–Ferrier Rearrangement and Bronsted acid-assisted debenzoxylation of 2-(N-(prop-2-ynyl)-N-tosylamino)benzaldehydes to prepare (Z)-1,2-dihydro-1-tosylbenzo[b]azepin-3-ones efficiently is reported. The reactions proceed rapidly under mild and operationally straightforward conditions for a wide variety of aldehyde substrates containing electron-withdrawing, electron-donating, and sterically demanding functional groups and afforded the corresponding benzo-fused azaheterocyclic products in moderate to excellent yields.
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gold catalyzed tandem intramolecular heterocyclization petasis ferrier Rearrangement of 2 prop 2 ynyloxy benzaldehydes as an expedient route to benzo b oxepin 3 2 h ones
Chemistry: A European Journal, 2011Co-Authors: Ella Min Ling Sze, Ming Joo Koh, Weidong Rao, Philip Wai Hong ChanAbstract:Partially or fully hydrogenated benzo[b]oxepines are common ring motifs found in many pharmaceutically interesting and potentially bioactive natural compounds. Representative examples range from the structurally simple and bioactive heliannuol A, pterulone, and radulanin A to the architecturally challenging compounds edulisone A and ovafolinin B. For this reason, the establishment of new synthetic methods to construct this biologically important class of compounds has received an immense amount of attention. The synthetic strategies toward functionalized benzo[b]oxepines can be divided into two groups: manipulation of a pre-existing oxygen-containing cyclic core or assembly from acyclic precursors. Despite the advances made through both these approaches, the development of new synthetic methods to prepare this class of oxygen heterocycles from readily available substrates and catalysts with selective control of substitution patterns under mild and operationally simplistic conditions remains desirable. The emergence of gold complexes as powerful and versatile Lewis acid catalysts that can mediate a plethora of C X (X=C, N, O, S) bond formations has been well documented in recent years. Among this myriad of works, one notable innovation has been the formation of carbocycles and heterocycles from cyclization of a carbonyl compound tethered to an alkyne in the presence of a gold catalyst. For example, Yamamoto and Jin recently reported an efficient synthetic route to fused triand tetracyclic enones based on the AuCl3/AgSbF6-catalyzed tandem heteroenyne metathesis/Nazarov cyclization of 1,3-enynyl ketones. On the basis of this and other previous studies on carbonyl metathesis, we reasoned that a strategy that made use of Opropargylated salicylaldehydes in the presence of a Lewis acid gold catalyst would hold promise as a new method for benzo[b]oxepin-3 ACHTUNGTRENNUNG(2H)-one synthesis. As part of an ongoing program exploring the scope of gold catalysis in heterocyclic synthesis, our discovery that Au complex 3 can effect tandem intramolecular heterocyclization/Petasis–Ferrier Rearrangement of 2-(prop-2-ynyloxy)benzaldehydes is reported herein (Scheme 1). This process provides a convenient synthetic route to benzo[b]oxepin-3ACHTUNGTRENNUNG(2H)-ones in 21– 99% yield for a wide variety of substrates under mild and operationally simplistic conditions that did not require the exclusion of air or moisture. A study that delineates the influence on reactivity of a substituent at the ortho position to the ethereal moiety on the salicylaldehyde is also presented. To the best of our knowledge, synthetic methods involving metal-mediated cyclizations of propargylic aldehydes of type 1 have thus far been reported to typically give the benzopyran product. We began by examining the cyclization of 1a by a variety of Lewis and Bronsted acids to establish the optimal reaction conditions (Table 1 and Table S1 in the Supporting In[a] E. M. L. Sze, Dr. W. Rao, M. J. Koh, Prof. Dr. P. W. H. Chan Division of Chemistry and Biological Chemistry School of Physical and Mathematical Sciences Nanyang Technological University Singapore 637371 (Singapore) Fax: (+65)6791-1961 E-mail : waihong@ntu.edu.sg Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201003096. Scheme 1. Gold(I)-catalyzed synthesis of benzo[b]oxepin-3 ACHTUNGTRENNUNG(2H)-ones from 2-(prop-2-ynyloxy)benzaldehydes. R=H, alkyl, aryl, halide, or NO2; R , R=H or alkyl.
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Gold‐Catalyzed Tandem Intramolecular Heterocyclization/Petasis–Ferrier Rearrangement of 2‐(Prop‐2‐ynyloxy)benzaldehydes as an Expedient Route to Benzo[b]oxepin‐3(2 H)‐ones
Chemistry (Weinheim an der Bergstrasse Germany), 2011Co-Authors: Ella Min Ling Sze, Ming Joo Koh, Weidong Rao, Philip Wai Hong ChanAbstract:Partially or fully hydrogenated benzo[b]oxepines are common ring motifs found in many pharmaceutically interesting and potentially bioactive natural compounds. Representative examples range from the structurally simple and bioactive heliannuol A, pterulone, and radulanin A to the architecturally challenging compounds edulisone A and ovafolinin B. For this reason, the establishment of new synthetic methods to construct this biologically important class of compounds has received an immense amount of attention. The synthetic strategies toward functionalized benzo[b]oxepines can be divided into two groups: manipulation of a pre-existing oxygen-containing cyclic core or assembly from acyclic precursors. Despite the advances made through both these approaches, the development of new synthetic methods to prepare this class of oxygen heterocycles from readily available substrates and catalysts with selective control of substitution patterns under mild and operationally simplistic conditions remains desirable. The emergence of gold complexes as powerful and versatile Lewis acid catalysts that can mediate a plethora of C X (X=C, N, O, S) bond formations has been well documented in recent years. Among this myriad of works, one notable innovation has been the formation of carbocycles and heterocycles from cyclization of a carbonyl compound tethered to an alkyne in the presence of a gold catalyst. For example, Yamamoto and Jin recently reported an efficient synthetic route to fused triand tetracyclic enones based on the AuCl3/AgSbF6-catalyzed tandem heteroenyne metathesis/Nazarov cyclization of 1,3-enynyl ketones. On the basis of this and other previous studies on carbonyl metathesis, we reasoned that a strategy that made use of Opropargylated salicylaldehydes in the presence of a Lewis acid gold catalyst would hold promise as a new method for benzo[b]oxepin-3 ACHTUNGTRENNUNG(2H)-one synthesis. As part of an ongoing program exploring the scope of gold catalysis in heterocyclic synthesis, our discovery that Au complex 3 can effect tandem intramolecular heterocyclization/Petasis–Ferrier Rearrangement of 2-(prop-2-ynyloxy)benzaldehydes is reported herein (Scheme 1). This process provides a convenient synthetic route to benzo[b]oxepin-3ACHTUNGTRENNUNG(2H)-ones in 21– 99% yield for a wide variety of substrates under mild and operationally simplistic conditions that did not require the exclusion of air or moisture. A study that delineates the influence on reactivity of a substituent at the ortho position to the ethereal moiety on the salicylaldehyde is also presented. To the best of our knowledge, synthetic methods involving metal-mediated cyclizations of propargylic aldehydes of type 1 have thus far been reported to typically give the benzopyran product. We began by examining the cyclization of 1a by a variety of Lewis and Bronsted acids to establish the optimal reaction conditions (Table 1 and Table S1 in the Supporting In[a] E. M. L. Sze, Dr. W. Rao, M. J. Koh, Prof. Dr. P. W. H. Chan Division of Chemistry and Biological Chemistry School of Physical and Mathematical Sciences Nanyang Technological University Singapore 637371 (Singapore) Fax: (+65)6791-1961 E-mail : waihong@ntu.edu.sg Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201003096. Scheme 1. Gold(I)-catalyzed synthesis of benzo[b]oxepin-3 ACHTUNGTRENNUNG(2H)-ones from 2-(prop-2-ynyloxy)benzaldehydes. R=H, alkyl, aryl, halide, or NO2; R , R=H or alkyl.
Ella Min Ling Sze - One of the best experts on this subject based on the ideXlab platform.
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synthesis of z 1 2 dihydro 1 tosylbenzo b azepin 3 ones by two step one pot gold catalyzed tandem heterocyclization petasis ferrier Rearrangement of 2 n prop 2 ynyl n tosylamino benzaldehydes
Tetrahedron, 2013Co-Authors: Ella Min Ling Sze, Ming Joo Koh, Yen Min Tjia, Weidong Rao, Philip Wai Hong ChanAbstract:Abstract A two-step, one-pot synthetic method that relies on gold(I)-catalyzed tandem heterocyclization/Petasis–Ferrier Rearrangement and Bronsted acid-assisted debenzoxylation of 2-(N-(prop-2-ynyl)-N-tosylamino)benzaldehydes to prepare (Z)-1,2-dihydro-1-tosylbenzo[b]azepin-3-ones efficiently is reported. The reactions proceed rapidly under mild and operationally straightforward conditions for a wide variety of aldehyde substrates containing electron-withdrawing, electron-donating, and sterically demanding functional groups and afforded the corresponding benzo-fused azaheterocyclic products in moderate to excellent yields.
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Synthesis of (Z)-1,2-dihydro-1-tosylbenzo[b]azepin-3-ones by two-step, one-pot gold-catalyzed tandem heterocyclization/Petasis–Ferrier Rearrangement of 2-(N-(prop-2-ynyl)-N-tosylamino)benzaldehydes
Tetrahedron, 2013Co-Authors: Ella Min Ling Sze, Ming Joo Koh, Yen Min Tjia, Weidong Rao, Philip Wai Hong ChanAbstract:Abstract A two-step, one-pot synthetic method that relies on gold(I)-catalyzed tandem heterocyclization/Petasis–Ferrier Rearrangement and Bronsted acid-assisted debenzoxylation of 2-(N-(prop-2-ynyl)-N-tosylamino)benzaldehydes to prepare (Z)-1,2-dihydro-1-tosylbenzo[b]azepin-3-ones efficiently is reported. The reactions proceed rapidly under mild and operationally straightforward conditions for a wide variety of aldehyde substrates containing electron-withdrawing, electron-donating, and sterically demanding functional groups and afforded the corresponding benzo-fused azaheterocyclic products in moderate to excellent yields.
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gold catalyzed tandem intramolecular heterocyclization petasis ferrier Rearrangement of 2 prop 2 ynyloxy benzaldehydes as an expedient route to benzo b oxepin 3 2 h ones
Chemistry: A European Journal, 2011Co-Authors: Ella Min Ling Sze, Ming Joo Koh, Weidong Rao, Philip Wai Hong ChanAbstract:Partially or fully hydrogenated benzo[b]oxepines are common ring motifs found in many pharmaceutically interesting and potentially bioactive natural compounds. Representative examples range from the structurally simple and bioactive heliannuol A, pterulone, and radulanin A to the architecturally challenging compounds edulisone A and ovafolinin B. For this reason, the establishment of new synthetic methods to construct this biologically important class of compounds has received an immense amount of attention. The synthetic strategies toward functionalized benzo[b]oxepines can be divided into two groups: manipulation of a pre-existing oxygen-containing cyclic core or assembly from acyclic precursors. Despite the advances made through both these approaches, the development of new synthetic methods to prepare this class of oxygen heterocycles from readily available substrates and catalysts with selective control of substitution patterns under mild and operationally simplistic conditions remains desirable. The emergence of gold complexes as powerful and versatile Lewis acid catalysts that can mediate a plethora of C X (X=C, N, O, S) bond formations has been well documented in recent years. Among this myriad of works, one notable innovation has been the formation of carbocycles and heterocycles from cyclization of a carbonyl compound tethered to an alkyne in the presence of a gold catalyst. For example, Yamamoto and Jin recently reported an efficient synthetic route to fused triand tetracyclic enones based on the AuCl3/AgSbF6-catalyzed tandem heteroenyne metathesis/Nazarov cyclization of 1,3-enynyl ketones. On the basis of this and other previous studies on carbonyl metathesis, we reasoned that a strategy that made use of Opropargylated salicylaldehydes in the presence of a Lewis acid gold catalyst would hold promise as a new method for benzo[b]oxepin-3 ACHTUNGTRENNUNG(2H)-one synthesis. As part of an ongoing program exploring the scope of gold catalysis in heterocyclic synthesis, our discovery that Au complex 3 can effect tandem intramolecular heterocyclization/Petasis–Ferrier Rearrangement of 2-(prop-2-ynyloxy)benzaldehydes is reported herein (Scheme 1). This process provides a convenient synthetic route to benzo[b]oxepin-3ACHTUNGTRENNUNG(2H)-ones in 21– 99% yield for a wide variety of substrates under mild and operationally simplistic conditions that did not require the exclusion of air or moisture. A study that delineates the influence on reactivity of a substituent at the ortho position to the ethereal moiety on the salicylaldehyde is also presented. To the best of our knowledge, synthetic methods involving metal-mediated cyclizations of propargylic aldehydes of type 1 have thus far been reported to typically give the benzopyran product. We began by examining the cyclization of 1a by a variety of Lewis and Bronsted acids to establish the optimal reaction conditions (Table 1 and Table S1 in the Supporting In[a] E. M. L. Sze, Dr. W. Rao, M. J. Koh, Prof. Dr. P. W. H. Chan Division of Chemistry and Biological Chemistry School of Physical and Mathematical Sciences Nanyang Technological University Singapore 637371 (Singapore) Fax: (+65)6791-1961 E-mail : waihong@ntu.edu.sg Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201003096. Scheme 1. Gold(I)-catalyzed synthesis of benzo[b]oxepin-3 ACHTUNGTRENNUNG(2H)-ones from 2-(prop-2-ynyloxy)benzaldehydes. R=H, alkyl, aryl, halide, or NO2; R , R=H or alkyl.
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Gold‐Catalyzed Tandem Intramolecular Heterocyclization/Petasis–Ferrier Rearrangement of 2‐(Prop‐2‐ynyloxy)benzaldehydes as an Expedient Route to Benzo[b]oxepin‐3(2 H)‐ones
Chemistry (Weinheim an der Bergstrasse Germany), 2011Co-Authors: Ella Min Ling Sze, Ming Joo Koh, Weidong Rao, Philip Wai Hong ChanAbstract:Partially or fully hydrogenated benzo[b]oxepines are common ring motifs found in many pharmaceutically interesting and potentially bioactive natural compounds. Representative examples range from the structurally simple and bioactive heliannuol A, pterulone, and radulanin A to the architecturally challenging compounds edulisone A and ovafolinin B. For this reason, the establishment of new synthetic methods to construct this biologically important class of compounds has received an immense amount of attention. The synthetic strategies toward functionalized benzo[b]oxepines can be divided into two groups: manipulation of a pre-existing oxygen-containing cyclic core or assembly from acyclic precursors. Despite the advances made through both these approaches, the development of new synthetic methods to prepare this class of oxygen heterocycles from readily available substrates and catalysts with selective control of substitution patterns under mild and operationally simplistic conditions remains desirable. The emergence of gold complexes as powerful and versatile Lewis acid catalysts that can mediate a plethora of C X (X=C, N, O, S) bond formations has been well documented in recent years. Among this myriad of works, one notable innovation has been the formation of carbocycles and heterocycles from cyclization of a carbonyl compound tethered to an alkyne in the presence of a gold catalyst. For example, Yamamoto and Jin recently reported an efficient synthetic route to fused triand tetracyclic enones based on the AuCl3/AgSbF6-catalyzed tandem heteroenyne metathesis/Nazarov cyclization of 1,3-enynyl ketones. On the basis of this and other previous studies on carbonyl metathesis, we reasoned that a strategy that made use of Opropargylated salicylaldehydes in the presence of a Lewis acid gold catalyst would hold promise as a new method for benzo[b]oxepin-3 ACHTUNGTRENNUNG(2H)-one synthesis. As part of an ongoing program exploring the scope of gold catalysis in heterocyclic synthesis, our discovery that Au complex 3 can effect tandem intramolecular heterocyclization/Petasis–Ferrier Rearrangement of 2-(prop-2-ynyloxy)benzaldehydes is reported herein (Scheme 1). This process provides a convenient synthetic route to benzo[b]oxepin-3ACHTUNGTRENNUNG(2H)-ones in 21– 99% yield for a wide variety of substrates under mild and operationally simplistic conditions that did not require the exclusion of air or moisture. A study that delineates the influence on reactivity of a substituent at the ortho position to the ethereal moiety on the salicylaldehyde is also presented. To the best of our knowledge, synthetic methods involving metal-mediated cyclizations of propargylic aldehydes of type 1 have thus far been reported to typically give the benzopyran product. We began by examining the cyclization of 1a by a variety of Lewis and Bronsted acids to establish the optimal reaction conditions (Table 1 and Table S1 in the Supporting In[a] E. M. L. Sze, Dr. W. Rao, M. J. Koh, Prof. Dr. P. W. H. Chan Division of Chemistry and Biological Chemistry School of Physical and Mathematical Sciences Nanyang Technological University Singapore 637371 (Singapore) Fax: (+65)6791-1961 E-mail : waihong@ntu.edu.sg Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201003096. Scheme 1. Gold(I)-catalyzed synthesis of benzo[b]oxepin-3 ACHTUNGTRENNUNG(2H)-ones from 2-(prop-2-ynyloxy)benzaldehydes. R=H, alkyl, aryl, halide, or NO2; R , R=H or alkyl.
Amos B. Smith - One of the best experts on this subject based on the ideXlab platform.
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Evolution of a Total Synthesis of (−)-Kendomycin Exploiting a Petasis−Ferrier Rearrangement/Ring-Closing Olefin Metathesis Strategy
Journal of the American Chemical Society, 2006Co-Authors: Amos B. Smith, Eugen F. Mesaros, Emmanuel A. MeyerAbstract:A convergent stereocontrolled total synthesis of (−)-kendomycin (1) has been achieved. The synthesis proceeds with a longest linear sequence of 21 steps, beginning with commercially available 2,4-dimethoxy-3-methylbenzaldehyde (12). Highlights of the synthesis include an effective Petasis−Ferrier union/Rearrangement tactic to construct the sterically encumbered tetrahydropyran ring, a ring-closing metathesis to generate the C(4a−13−20a) macrocycle, an effective epoxidation/deoxygenation sequence to isomerize the C(13,14) olefin, and a biomimetic quinone−methide−lactol assembly to complete the synthesis.
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Total Synthesis of (−)-Kendomycin Exploiting a Petasis−Ferrier Rearrangement/Ring-Closing Olefin Metathesis Synthetic Strategy
Journal of the American Chemical Society, 2005Co-Authors: Amos B. Smith, Eugen F. Mesaros, Emmanuel A. MeyerAbstract:The total synthesis of (−)-kendomycin (1), a novel macrocyclic polyketide with antibacterial and antitumor activity, was achieved in 21 steps (longest linear sequence) exploiting an effective Petasis−Ferrier union/Rearrangement tactic to construct the tetrahydropyran ring, a ring-closing metathesis to generate the macrocycle, and a biomimetic quinone−methide−lactol assembly.
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Total Syntheses of (+)-Zampanolide and (+)-Dactylolide Exploiting a Unified Strategy
Journal of the American Chemical Society, 2002Co-Authors: Amos B. Smith, Igor G. Safonov, R. Michael CorbettAbstract:The first total syntheses of (+)-zampanolide (1) and (+)-dactylolide (2), members of a new class of tumor cell growth inhibitory macrolides, have been achieved. Key features of the unified synthetic scheme included the stereocontrolled construction of the cis-2,6-disubstituted tetrahydropyran via a modified Petasis-Ferrier Rearrangement, a highly convergent assembly of the macrocyclic domain, and, in the case of zampanolide, a Curtius Rearrangement/acylation tactic to install the N-acyl hemiaminal. The complete relative and absolute stereochemistries for both (+)-zampanolide and (+)-dactylolide were also assigned, albeit tentatively in the case of (+)-zampanolide (1).
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Total synthesis of (+)-phorboxazole A exploiting the Petasis-Ferrier Rearrangement.
Journal of the American Chemical Society, 2001Co-Authors: Amos B. Smith, Kevin P C Minbiole, And Patrick R. Verhoest, Michael SchelhaasAbstract:A highly convergent, stereocontrolled total synthesis of the potent antiproliferative agent (+)-phorboxazole A (1) has been achieved. Highlights of the synthesis include: modified Petasis−Ferrier Rearrangements for assembly of both the C(11−15) and C(22−26) cis-tetrahydropyran rings; extension of the Julia olefination to the synthesis of enol ethers; the design, synthesis, and application of a novel bifunctional oxazole linchpin; and Stille coupling of a C(28) trimethyl stannane with a C(29) oxazole triflate. The longest linear sequence leading to (+)-phorboxazole A (1) was 27 steps, with an overall yield of 3%.
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Phorboxazole Synthetic Studies. 2. Construction of a C(20−28) Subtarget, a Further Extension of the Petasis−Ferrier Rearrangement
Organic letters, 1999Co-Authors: Amos B. Smith, Kevin P C Minbiole, Patrick R. Verhoest, Thomas J. BeauchampAbstract:In this, the second of two Letters, we describe the efficient assembly of (+)-4, a C(20−28) subtarget for the total synthesis of phorboxazoles A (1) and B (2). The synthesis was achieved in 12 linear steps (20% overall yield) via Petasis−Ferrier Rearrangement of an E/Z mixture of trisubstituted enol ethers (15) to assemble the C(22−26) cis-tetrahydropyran. A mechanism for the observed diastereoconvergence of 15 is proposed. In addition, a new tactic for the synthesis of enol ethers (e.g., 15) based on the elegant work of Julia is described.
Weidong Rao - One of the best experts on this subject based on the ideXlab platform.
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synthesis of z 1 2 dihydro 1 tosylbenzo b azepin 3 ones by two step one pot gold catalyzed tandem heterocyclization petasis ferrier Rearrangement of 2 n prop 2 ynyl n tosylamino benzaldehydes
Tetrahedron, 2013Co-Authors: Ella Min Ling Sze, Ming Joo Koh, Yen Min Tjia, Weidong Rao, Philip Wai Hong ChanAbstract:Abstract A two-step, one-pot synthetic method that relies on gold(I)-catalyzed tandem heterocyclization/Petasis–Ferrier Rearrangement and Bronsted acid-assisted debenzoxylation of 2-(N-(prop-2-ynyl)-N-tosylamino)benzaldehydes to prepare (Z)-1,2-dihydro-1-tosylbenzo[b]azepin-3-ones efficiently is reported. The reactions proceed rapidly under mild and operationally straightforward conditions for a wide variety of aldehyde substrates containing electron-withdrawing, electron-donating, and sterically demanding functional groups and afforded the corresponding benzo-fused azaheterocyclic products in moderate to excellent yields.
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Synthesis of (Z)-1,2-dihydro-1-tosylbenzo[b]azepin-3-ones by two-step, one-pot gold-catalyzed tandem heterocyclization/Petasis–Ferrier Rearrangement of 2-(N-(prop-2-ynyl)-N-tosylamino)benzaldehydes
Tetrahedron, 2013Co-Authors: Ella Min Ling Sze, Ming Joo Koh, Yen Min Tjia, Weidong Rao, Philip Wai Hong ChanAbstract:Abstract A two-step, one-pot synthetic method that relies on gold(I)-catalyzed tandem heterocyclization/Petasis–Ferrier Rearrangement and Bronsted acid-assisted debenzoxylation of 2-(N-(prop-2-ynyl)-N-tosylamino)benzaldehydes to prepare (Z)-1,2-dihydro-1-tosylbenzo[b]azepin-3-ones efficiently is reported. The reactions proceed rapidly under mild and operationally straightforward conditions for a wide variety of aldehyde substrates containing electron-withdrawing, electron-donating, and sterically demanding functional groups and afforded the corresponding benzo-fused azaheterocyclic products in moderate to excellent yields.
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gold catalyzed tandem intramolecular heterocyclization petasis ferrier Rearrangement of 2 prop 2 ynyloxy benzaldehydes as an expedient route to benzo b oxepin 3 2 h ones
Chemistry: A European Journal, 2011Co-Authors: Ella Min Ling Sze, Ming Joo Koh, Weidong Rao, Philip Wai Hong ChanAbstract:Partially or fully hydrogenated benzo[b]oxepines are common ring motifs found in many pharmaceutically interesting and potentially bioactive natural compounds. Representative examples range from the structurally simple and bioactive heliannuol A, pterulone, and radulanin A to the architecturally challenging compounds edulisone A and ovafolinin B. For this reason, the establishment of new synthetic methods to construct this biologically important class of compounds has received an immense amount of attention. The synthetic strategies toward functionalized benzo[b]oxepines can be divided into two groups: manipulation of a pre-existing oxygen-containing cyclic core or assembly from acyclic precursors. Despite the advances made through both these approaches, the development of new synthetic methods to prepare this class of oxygen heterocycles from readily available substrates and catalysts with selective control of substitution patterns under mild and operationally simplistic conditions remains desirable. The emergence of gold complexes as powerful and versatile Lewis acid catalysts that can mediate a plethora of C X (X=C, N, O, S) bond formations has been well documented in recent years. Among this myriad of works, one notable innovation has been the formation of carbocycles and heterocycles from cyclization of a carbonyl compound tethered to an alkyne in the presence of a gold catalyst. For example, Yamamoto and Jin recently reported an efficient synthetic route to fused triand tetracyclic enones based on the AuCl3/AgSbF6-catalyzed tandem heteroenyne metathesis/Nazarov cyclization of 1,3-enynyl ketones. On the basis of this and other previous studies on carbonyl metathesis, we reasoned that a strategy that made use of Opropargylated salicylaldehydes in the presence of a Lewis acid gold catalyst would hold promise as a new method for benzo[b]oxepin-3 ACHTUNGTRENNUNG(2H)-one synthesis. As part of an ongoing program exploring the scope of gold catalysis in heterocyclic synthesis, our discovery that Au complex 3 can effect tandem intramolecular heterocyclization/Petasis–Ferrier Rearrangement of 2-(prop-2-ynyloxy)benzaldehydes is reported herein (Scheme 1). This process provides a convenient synthetic route to benzo[b]oxepin-3ACHTUNGTRENNUNG(2H)-ones in 21– 99% yield for a wide variety of substrates under mild and operationally simplistic conditions that did not require the exclusion of air or moisture. A study that delineates the influence on reactivity of a substituent at the ortho position to the ethereal moiety on the salicylaldehyde is also presented. To the best of our knowledge, synthetic methods involving metal-mediated cyclizations of propargylic aldehydes of type 1 have thus far been reported to typically give the benzopyran product. We began by examining the cyclization of 1a by a variety of Lewis and Bronsted acids to establish the optimal reaction conditions (Table 1 and Table S1 in the Supporting In[a] E. M. L. Sze, Dr. W. Rao, M. J. Koh, Prof. Dr. P. W. H. Chan Division of Chemistry and Biological Chemistry School of Physical and Mathematical Sciences Nanyang Technological University Singapore 637371 (Singapore) Fax: (+65)6791-1961 E-mail : waihong@ntu.edu.sg Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201003096. Scheme 1. Gold(I)-catalyzed synthesis of benzo[b]oxepin-3 ACHTUNGTRENNUNG(2H)-ones from 2-(prop-2-ynyloxy)benzaldehydes. R=H, alkyl, aryl, halide, or NO2; R , R=H or alkyl.
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Gold‐Catalyzed Tandem Intramolecular Heterocyclization/Petasis–Ferrier Rearrangement of 2‐(Prop‐2‐ynyloxy)benzaldehydes as an Expedient Route to Benzo[b]oxepin‐3(2 H)‐ones
Chemistry (Weinheim an der Bergstrasse Germany), 2011Co-Authors: Ella Min Ling Sze, Ming Joo Koh, Weidong Rao, Philip Wai Hong ChanAbstract:Partially or fully hydrogenated benzo[b]oxepines are common ring motifs found in many pharmaceutically interesting and potentially bioactive natural compounds. Representative examples range from the structurally simple and bioactive heliannuol A, pterulone, and radulanin A to the architecturally challenging compounds edulisone A and ovafolinin B. For this reason, the establishment of new synthetic methods to construct this biologically important class of compounds has received an immense amount of attention. The synthetic strategies toward functionalized benzo[b]oxepines can be divided into two groups: manipulation of a pre-existing oxygen-containing cyclic core or assembly from acyclic precursors. Despite the advances made through both these approaches, the development of new synthetic methods to prepare this class of oxygen heterocycles from readily available substrates and catalysts with selective control of substitution patterns under mild and operationally simplistic conditions remains desirable. The emergence of gold complexes as powerful and versatile Lewis acid catalysts that can mediate a plethora of C X (X=C, N, O, S) bond formations has been well documented in recent years. Among this myriad of works, one notable innovation has been the formation of carbocycles and heterocycles from cyclization of a carbonyl compound tethered to an alkyne in the presence of a gold catalyst. For example, Yamamoto and Jin recently reported an efficient synthetic route to fused triand tetracyclic enones based on the AuCl3/AgSbF6-catalyzed tandem heteroenyne metathesis/Nazarov cyclization of 1,3-enynyl ketones. On the basis of this and other previous studies on carbonyl metathesis, we reasoned that a strategy that made use of Opropargylated salicylaldehydes in the presence of a Lewis acid gold catalyst would hold promise as a new method for benzo[b]oxepin-3 ACHTUNGTRENNUNG(2H)-one synthesis. As part of an ongoing program exploring the scope of gold catalysis in heterocyclic synthesis, our discovery that Au complex 3 can effect tandem intramolecular heterocyclization/Petasis–Ferrier Rearrangement of 2-(prop-2-ynyloxy)benzaldehydes is reported herein (Scheme 1). This process provides a convenient synthetic route to benzo[b]oxepin-3ACHTUNGTRENNUNG(2H)-ones in 21– 99% yield for a wide variety of substrates under mild and operationally simplistic conditions that did not require the exclusion of air or moisture. A study that delineates the influence on reactivity of a substituent at the ortho position to the ethereal moiety on the salicylaldehyde is also presented. To the best of our knowledge, synthetic methods involving metal-mediated cyclizations of propargylic aldehydes of type 1 have thus far been reported to typically give the benzopyran product. We began by examining the cyclization of 1a by a variety of Lewis and Bronsted acids to establish the optimal reaction conditions (Table 1 and Table S1 in the Supporting In[a] E. M. L. Sze, Dr. W. Rao, M. J. Koh, Prof. Dr. P. W. H. Chan Division of Chemistry and Biological Chemistry School of Physical and Mathematical Sciences Nanyang Technological University Singapore 637371 (Singapore) Fax: (+65)6791-1961 E-mail : waihong@ntu.edu.sg Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201003096. Scheme 1. Gold(I)-catalyzed synthesis of benzo[b]oxepin-3 ACHTUNGTRENNUNG(2H)-ones from 2-(prop-2-ynyloxy)benzaldehydes. R=H, alkyl, aryl, halide, or NO2; R , R=H or alkyl.
Ming Joo Koh - One of the best experts on this subject based on the ideXlab platform.
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synthesis of z 1 2 dihydro 1 tosylbenzo b azepin 3 ones by two step one pot gold catalyzed tandem heterocyclization petasis ferrier Rearrangement of 2 n prop 2 ynyl n tosylamino benzaldehydes
Tetrahedron, 2013Co-Authors: Ella Min Ling Sze, Ming Joo Koh, Yen Min Tjia, Weidong Rao, Philip Wai Hong ChanAbstract:Abstract A two-step, one-pot synthetic method that relies on gold(I)-catalyzed tandem heterocyclization/Petasis–Ferrier Rearrangement and Bronsted acid-assisted debenzoxylation of 2-(N-(prop-2-ynyl)-N-tosylamino)benzaldehydes to prepare (Z)-1,2-dihydro-1-tosylbenzo[b]azepin-3-ones efficiently is reported. The reactions proceed rapidly under mild and operationally straightforward conditions for a wide variety of aldehyde substrates containing electron-withdrawing, electron-donating, and sterically demanding functional groups and afforded the corresponding benzo-fused azaheterocyclic products in moderate to excellent yields.
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Synthesis of (Z)-1,2-dihydro-1-tosylbenzo[b]azepin-3-ones by two-step, one-pot gold-catalyzed tandem heterocyclization/Petasis–Ferrier Rearrangement of 2-(N-(prop-2-ynyl)-N-tosylamino)benzaldehydes
Tetrahedron, 2013Co-Authors: Ella Min Ling Sze, Ming Joo Koh, Yen Min Tjia, Weidong Rao, Philip Wai Hong ChanAbstract:Abstract A two-step, one-pot synthetic method that relies on gold(I)-catalyzed tandem heterocyclization/Petasis–Ferrier Rearrangement and Bronsted acid-assisted debenzoxylation of 2-(N-(prop-2-ynyl)-N-tosylamino)benzaldehydes to prepare (Z)-1,2-dihydro-1-tosylbenzo[b]azepin-3-ones efficiently is reported. The reactions proceed rapidly under mild and operationally straightforward conditions for a wide variety of aldehyde substrates containing electron-withdrawing, electron-donating, and sterically demanding functional groups and afforded the corresponding benzo-fused azaheterocyclic products in moderate to excellent yields.
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gold catalyzed tandem intramolecular heterocyclization petasis ferrier Rearrangement of 2 prop 2 ynyloxy benzaldehydes as an expedient route to benzo b oxepin 3 2 h ones
Chemistry: A European Journal, 2011Co-Authors: Ella Min Ling Sze, Ming Joo Koh, Weidong Rao, Philip Wai Hong ChanAbstract:Partially or fully hydrogenated benzo[b]oxepines are common ring motifs found in many pharmaceutically interesting and potentially bioactive natural compounds. Representative examples range from the structurally simple and bioactive heliannuol A, pterulone, and radulanin A to the architecturally challenging compounds edulisone A and ovafolinin B. For this reason, the establishment of new synthetic methods to construct this biologically important class of compounds has received an immense amount of attention. The synthetic strategies toward functionalized benzo[b]oxepines can be divided into two groups: manipulation of a pre-existing oxygen-containing cyclic core or assembly from acyclic precursors. Despite the advances made through both these approaches, the development of new synthetic methods to prepare this class of oxygen heterocycles from readily available substrates and catalysts with selective control of substitution patterns under mild and operationally simplistic conditions remains desirable. The emergence of gold complexes as powerful and versatile Lewis acid catalysts that can mediate a plethora of C X (X=C, N, O, S) bond formations has been well documented in recent years. Among this myriad of works, one notable innovation has been the formation of carbocycles and heterocycles from cyclization of a carbonyl compound tethered to an alkyne in the presence of a gold catalyst. For example, Yamamoto and Jin recently reported an efficient synthetic route to fused triand tetracyclic enones based on the AuCl3/AgSbF6-catalyzed tandem heteroenyne metathesis/Nazarov cyclization of 1,3-enynyl ketones. On the basis of this and other previous studies on carbonyl metathesis, we reasoned that a strategy that made use of Opropargylated salicylaldehydes in the presence of a Lewis acid gold catalyst would hold promise as a new method for benzo[b]oxepin-3 ACHTUNGTRENNUNG(2H)-one synthesis. As part of an ongoing program exploring the scope of gold catalysis in heterocyclic synthesis, our discovery that Au complex 3 can effect tandem intramolecular heterocyclization/Petasis–Ferrier Rearrangement of 2-(prop-2-ynyloxy)benzaldehydes is reported herein (Scheme 1). This process provides a convenient synthetic route to benzo[b]oxepin-3ACHTUNGTRENNUNG(2H)-ones in 21– 99% yield for a wide variety of substrates under mild and operationally simplistic conditions that did not require the exclusion of air or moisture. A study that delineates the influence on reactivity of a substituent at the ortho position to the ethereal moiety on the salicylaldehyde is also presented. To the best of our knowledge, synthetic methods involving metal-mediated cyclizations of propargylic aldehydes of type 1 have thus far been reported to typically give the benzopyran product. We began by examining the cyclization of 1a by a variety of Lewis and Bronsted acids to establish the optimal reaction conditions (Table 1 and Table S1 in the Supporting In[a] E. M. L. Sze, Dr. W. Rao, M. J. Koh, Prof. Dr. P. W. H. Chan Division of Chemistry and Biological Chemistry School of Physical and Mathematical Sciences Nanyang Technological University Singapore 637371 (Singapore) Fax: (+65)6791-1961 E-mail : waihong@ntu.edu.sg Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201003096. Scheme 1. Gold(I)-catalyzed synthesis of benzo[b]oxepin-3 ACHTUNGTRENNUNG(2H)-ones from 2-(prop-2-ynyloxy)benzaldehydes. R=H, alkyl, aryl, halide, or NO2; R , R=H or alkyl.
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Gold‐Catalyzed Tandem Intramolecular Heterocyclization/Petasis–Ferrier Rearrangement of 2‐(Prop‐2‐ynyloxy)benzaldehydes as an Expedient Route to Benzo[b]oxepin‐3(2 H)‐ones
Chemistry (Weinheim an der Bergstrasse Germany), 2011Co-Authors: Ella Min Ling Sze, Ming Joo Koh, Weidong Rao, Philip Wai Hong ChanAbstract:Partially or fully hydrogenated benzo[b]oxepines are common ring motifs found in many pharmaceutically interesting and potentially bioactive natural compounds. Representative examples range from the structurally simple and bioactive heliannuol A, pterulone, and radulanin A to the architecturally challenging compounds edulisone A and ovafolinin B. For this reason, the establishment of new synthetic methods to construct this biologically important class of compounds has received an immense amount of attention. The synthetic strategies toward functionalized benzo[b]oxepines can be divided into two groups: manipulation of a pre-existing oxygen-containing cyclic core or assembly from acyclic precursors. Despite the advances made through both these approaches, the development of new synthetic methods to prepare this class of oxygen heterocycles from readily available substrates and catalysts with selective control of substitution patterns under mild and operationally simplistic conditions remains desirable. The emergence of gold complexes as powerful and versatile Lewis acid catalysts that can mediate a plethora of C X (X=C, N, O, S) bond formations has been well documented in recent years. Among this myriad of works, one notable innovation has been the formation of carbocycles and heterocycles from cyclization of a carbonyl compound tethered to an alkyne in the presence of a gold catalyst. For example, Yamamoto and Jin recently reported an efficient synthetic route to fused triand tetracyclic enones based on the AuCl3/AgSbF6-catalyzed tandem heteroenyne metathesis/Nazarov cyclization of 1,3-enynyl ketones. On the basis of this and other previous studies on carbonyl metathesis, we reasoned that a strategy that made use of Opropargylated salicylaldehydes in the presence of a Lewis acid gold catalyst would hold promise as a new method for benzo[b]oxepin-3 ACHTUNGTRENNUNG(2H)-one synthesis. As part of an ongoing program exploring the scope of gold catalysis in heterocyclic synthesis, our discovery that Au complex 3 can effect tandem intramolecular heterocyclization/Petasis–Ferrier Rearrangement of 2-(prop-2-ynyloxy)benzaldehydes is reported herein (Scheme 1). This process provides a convenient synthetic route to benzo[b]oxepin-3ACHTUNGTRENNUNG(2H)-ones in 21– 99% yield for a wide variety of substrates under mild and operationally simplistic conditions that did not require the exclusion of air or moisture. A study that delineates the influence on reactivity of a substituent at the ortho position to the ethereal moiety on the salicylaldehyde is also presented. To the best of our knowledge, synthetic methods involving metal-mediated cyclizations of propargylic aldehydes of type 1 have thus far been reported to typically give the benzopyran product. We began by examining the cyclization of 1a by a variety of Lewis and Bronsted acids to establish the optimal reaction conditions (Table 1 and Table S1 in the Supporting In[a] E. M. L. Sze, Dr. W. Rao, M. J. Koh, Prof. Dr. P. W. H. Chan Division of Chemistry and Biological Chemistry School of Physical and Mathematical Sciences Nanyang Technological University Singapore 637371 (Singapore) Fax: (+65)6791-1961 E-mail : waihong@ntu.edu.sg Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201003096. Scheme 1. Gold(I)-catalyzed synthesis of benzo[b]oxepin-3 ACHTUNGTRENNUNG(2H)-ones from 2-(prop-2-ynyloxy)benzaldehydes. R=H, alkyl, aryl, halide, or NO2; R , R=H or alkyl.