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David M. Hodgson - One of the best experts on this subject based on the ideXlab platform.
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intramolecular Oxonium Ylide formation 2 3 sigmatropic rearrangement of diazocarbonyl substituted cyclic unsaturated acetals a formal synthesis of hyperolactone c
Journal of Organic Chemistry, 2014Co-Authors: David M. Hodgson, Elena Morenoclavijo, Ziga Perko, Minxiang Zeng, Amber L. Thompson, Kimberley J Powell, Michael D. MooreAbstract:Rh(II)-catalyzed Oxonium Ylide formation–[2,3] sigmatropic rearrangement of α-diazo-β-ketoesters possessing γ-cyclic unsaturated acetal substitution, followed by acid-catalyzed elimination–lactonization, provides a concise approach to 1,7-dioxaspiro[4.4]non-2-ene-4,6-diones. The process creates adjacent quaternary stereocenters with full control of the relative stereochemistry. An unsymmetrical monomethylated cyclic unsaturated acetal leads to hyperolactone C, where Ylide formation–rearrangement proceeds with high selectivity between subtly nonequivalent acetal oxygen atoms.
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Intramolecular Oxonium Ylide Formation–[2,3] Sigmatropic Rearrangement of Diazocarbonyl-Substituted Cyclic Unsaturated Acetals: A Formal Synthesis of Hyperolactone C
2014Co-Authors: David M. Hodgson, Stanislav Man, Kimberley J. Powell, Ziga Perko, Minxiang Zeng, Elena Moreno-clavijo, Amber L. Thompson, Michael D. MooreAbstract:Rh(II)-catalyzed Oxonium Ylide formation–[2,3] sigmatropic rearrangement of α-diazo-β-ketoesters possessing γ-cyclic unsaturated acetal substitution, followed by acid-catalyzed elimination–lactonization, provides a concise approach to 1,7-dioxaspiro[4.4]non-2-ene-4,6-diones. The process creates adjacent quaternary stereocenters with full control of the relative stereochemistry. An unsymmetrical monomethylated cyclic unsaturated acetal leads to hyperolactone C, where Ylide formation–rearrangement proceeds with high selectivity between subtly nonequivalent acetal oxygen atoms
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an approach to hyperolactone c and analogues using late stage conjugate addition on an Oxonium Ylide derived spirofuranone
Organic and Biomolecular Chemistry, 2013Co-Authors: David M. Hodgson, Elena MorenoclavijoAbstract:A stereocontrolled synthesis of norphenyl hyperolactone C together with its utility as a direct precursor to the anti-HIV agent hyperolactone C and analogues by addition of organolithiums, are described. Preliminary studies to access this key building block in a catalytic enantioselective manner are also reported.
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synthesis of the anti hiv agent hyperolactone c by using Oxonium Ylide formation rearrangement
Chemistry: A European Journal, 2011Co-Authors: David M. HodgsonAbstract:: Starting from readily available (S)-styrene oxide an asymmetric synthesis is described of the naturally occurring anti-HIV spirolactone (-)-hyperolactone C, which possesses adjacent fully substituted stereocenters. The key step involves a stereocontrolled Rh(II) -catalysed Oxonium Ylide formation-[2,3] sigmatropic rearrangement of an α-diazo-β-ketoester bearing allylic ether functionality. From the resulting furanone, an acid-catalysed lactonisation and dehydrogenation gives the natural product.
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Consecutive alkene cross-metathesis/Oxonium Ylide formation-rearrangement: synthesis of the anti-HIV agent hyperolactone C.
Organic letters, 2008Co-Authors: David M. Hodgson, Deepshikha Angrish, Stephanie P Erickson, Johannes Kloesges, Caroline H LeeAbstract:Alpha-diazo-beta-ketoesters bearing allylic ether functionality undergo highly stereoselective Ru-carbene-catalyzed alkene cross-metathesis followed by Rh(2)(OAc)(4)-catalyzed Oxonium Ylide formation/[2,3] sigmatropic rearrangement in a one-flask operation and in a highly diastereoselective manner. The methodology has been demonstrated in a concise synthesis of the anti-HIV agent hyperolactone C.
Takayuki Yakura - One of the best experts on this subject based on the ideXlab platform.
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chemo and stereoselective six membered Oxonium Ylide formation 2 3 sigmatropic rearrangement of 2 diazo 3 ketoesters with dirhodium ii catalyst and its application to the synthesis of tanikolide
Tetrahedron, 2019Co-Authors: Hikari Jinnouchi, Hisanori Nambu, Tomoya Fujiwara, Kanae Takahashi, Takayuki YakuraAbstract:Abstract Dirhodium(II)-catalyzed Oxonium Ylide formation–[2,3]-sigmatropic rearrangement of 6-allyloxy-2-diazo-3-ketoesters possessing a C-6 substituent is described. The reaction of 6-alkyl- or 6-aryl-substituted 6-allyloxy-2-diazo-3-ketoesters with a catalytic amount of Rh2(S-PTTL)4 proceeded in a chemoselective and stereoselective manner to provide 6-substituted 2-allyl-3-oxotetrahydropyran-2-carboxylates in good yields and with high diastereoselectivities. To demonstrate the utility of this sequential reaction, we conducted the total synthesis of (+)-tanikolide, in which the construction of the δ-lactone skeleton was achieved by employing a 2-iodobenzamide-catalyzed oxidative cleavage of tetrahydropyran-2-methanol.
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total synthesis of tanikolide by a traceless stereoinduction method using rhodium ii catalyzed Oxonium Ylide formation 2 3 sigmatropic rearrangement and nhc catalyzed ring expansion lactonization
Synlett, 2016Co-Authors: Hisanori Nambu, Hikari Jinnouchi, Tomoya Fujiwara, Takayuki YakuraAbstract:The total synthesis of (+)-tanikolide was accomplished by a traceless stereoinduction method using the key steps of a Rh(II)-catalyzed Oxonium Ylide formation–[2,3]-sigmatropic rearrangement and an N-heterocyclic carbene-catalyzed ring-expansion lactonization of tetrahydrofurfural. This synthetic route is applicable to the divergent synthesis of tanikolide analogues.
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application of a stereoselective rhodium ii catalyzed Oxonium Ylide formation 2 3 sigmatropic rearrangement of an α diazo β keto ester to the synthesis of 2 epi cinatrin c1 dimethyl ester
Synlett, 2012Co-Authors: Takayuki Yakura, Ayaka Ozono, Katsuaki Matsui, Masayuki Yamashita, Tomoya FujiwaraAbstract:The Rh2(OAc)4-catalyzed Oxonium Ylide formation–[2,3]-sigmatropic rearrangement of a highly functionalized α-diazo-β-keto ester derived from d -glucose proceeded stereoselectively to give the corresponding tetrahydrofuran-3-one as a single diastereomer in high yield. This reaction was applied to the synthesis of 2-epi-cinatrin C1 dimethyl ester as a key step.
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stereoselective synthesis of c3 c12 dihydropyran portion of antitumor laulimalide using copper catalyzed Oxonium Ylide formation 2 3 shift
Chemical & Pharmaceutical Bulletin, 2005Co-Authors: Takayuki Yakura, Wataru Muramatsu, Junichi UenishiAbstract:Copper-catalyzed Oxonium Ylide formation–[2,3] shift of (5S,7R)-5-allyloxy-1-diazo-8-(p-methoxybenzyloxy)-7-methyl-2-octanone (3) proceeded in tetrahydrofuran-dichloromethane (4 : 1) under reflux with an excellent stereoselectivity (97 : 3) to give (2R,6S)-2-allyl-6-[(2R)-3-(p-methoxybenzyloxy)-2-methylpropyl]-3-dihydropyranone (2) as a major isomer in 82% yield. The resultant pyranone (2) was converted to the key intermediate (1) of the Mulzer's laulimalide synthesis and its derivatives (14, 15).
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Stereoselective synthesis of cyclopentanones using dirhodium(II)-catalyzed intramolecular C-H insertion reaction
Yakugaku zasshi : Journal of the Pharmaceutical Society of Japan, 2000Co-Authors: Takayuki YakuraAbstract:This review summarizes novel stereoselective syntheses of 3,4-cis- and 3,4-trans-3-alkyl-4-silyloxycyclopentanones using a dirhodium(II)-catalyzed intramolecular C-H insertion reaction as a key reaction. Treatment of diazoketoesters (20a-e) with 1 mol % of dirhodium(II) tetraacetate gave 2,3-trans-3,4-cis-cyclopentanones (21a-e) as major products. The presence of both the keto and ester groups in the precursors was found to be essential for this chemo- and stereoselective intramolecular C-H insertion reaction to take place. A possible interpretation for the observed stereoselectivity is presented. Optically active Corey lactone (38) was synthesized using a similar reaction of chiral alpha-diazo-beta-ketoester (33). Next, reactions of 5,6-bisoxygenated diazoketones with Rh2(OAc)4 were investigated. An acetonide derivative (39), upon treatment with Rh2(OAc)4, gave 3,8-dioxabicyclo[3.2.1]octane (42) via Oxonium Ylide formation/1,2-shift. On the other hand, similar treatment of 5,6-bis(tert-butyldimethylsilyloxy) derivative (47) gave a C-H insertion product (51) which was purified by silica gel column chromatography to give 4-silyloxycyclopentenone (48). Direct reduction of 51 with lithium aluminum hydride gave stereoselectively diol (52) in 52% yield from 47. Reaction of 2-methoxycarbonylcyclopentenone (48) and a 2-benzenesulfonyl congener (50) with R2CuLi or RMgBr-CuI stereoselectively gave 2,3-trans-3,4-trans-cyclopentanones (22, 57) as a major diastereoisomer. On the other hand, reaction with R3 Al in toluene exclusively gave the corresponding 3,4-cis-adducts (21 and 58).
Caroline H Lee - One of the best experts on this subject based on the ideXlab platform.
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Consecutive alkene cross-metathesis/Oxonium Ylide formation-rearrangement: synthesis of the anti-HIV agent hyperolactone C.
Organic letters, 2008Co-Authors: David M. Hodgson, Deepshikha Angrish, Stephanie P Erickson, Johannes Kloesges, Caroline H LeeAbstract:Alpha-diazo-beta-ketoesters bearing allylic ether functionality undergo highly stereoselective Ru-carbene-catalyzed alkene cross-metathesis followed by Rh(2)(OAc)(4)-catalyzed Oxonium Ylide formation/[2,3] sigmatropic rearrangement in a one-flask operation and in a highly diastereoselective manner. The methodology has been demonstrated in a concise synthesis of the anti-HIV agent hyperolactone C.
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consecutive alkene cross metathesis Oxonium Ylide formation rearrangement synthesis of the anti hiv agent hyperolactone c
Organic Letters, 2008Co-Authors: David M. Hodgson, Deepshikha Angrish, Stephanie P Erickson, Johannes Kloesges, Caroline H LeeAbstract:Alpha-diazo-beta-ketoesters bearing allylic ether functionality undergo highly stereoselective Ru-carbene-catalyzed alkene cross-metathesis followed by Rh(2)(OAc)(4)-catalyzed Oxonium Ylide formation/[2,3] sigmatropic rearrangement in a one-flask operation and in a highly diastereoselective manner. The methodology has been demonstrated in a concise synthesis of the anti-HIV agent hyperolactone C.
Johannes Kloesges - One of the best experts on this subject based on the ideXlab platform.
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Consecutive alkene cross-metathesis/Oxonium Ylide formation-rearrangement: synthesis of the anti-HIV agent hyperolactone C.
Organic letters, 2008Co-Authors: David M. Hodgson, Deepshikha Angrish, Stephanie P Erickson, Johannes Kloesges, Caroline H LeeAbstract:Alpha-diazo-beta-ketoesters bearing allylic ether functionality undergo highly stereoselective Ru-carbene-catalyzed alkene cross-metathesis followed by Rh(2)(OAc)(4)-catalyzed Oxonium Ylide formation/[2,3] sigmatropic rearrangement in a one-flask operation and in a highly diastereoselective manner. The methodology has been demonstrated in a concise synthesis of the anti-HIV agent hyperolactone C.
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consecutive alkene cross metathesis Oxonium Ylide formation rearrangement synthesis of the anti hiv agent hyperolactone c
Organic Letters, 2008Co-Authors: David M. Hodgson, Deepshikha Angrish, Stephanie P Erickson, Johannes KloesgesAbstract:α-Diazo-β-ketoesters bearing allylic ether functionality undergo highly stereoselective Ru-carbene-catalyzed alkene cross-metathesis followed by Rh2(OAc)4-catalyzed Oxonium Ylide formation/[2,3] sigmatropic rearrangement in a one-flask operation and in a highly diastereoselective manner. The methodology has been demonstrated in a concise synthesis of the anti-HIV agent hyperolactone C.
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consecutive alkene cross metathesis Oxonium Ylide formation rearrangement synthesis of the anti hiv agent hyperolactone c
Organic Letters, 2008Co-Authors: David M. Hodgson, Deepshikha Angrish, Stephanie P Erickson, Johannes Kloesges, Caroline H LeeAbstract:Alpha-diazo-beta-ketoesters bearing allylic ether functionality undergo highly stereoselective Ru-carbene-catalyzed alkene cross-metathesis followed by Rh(2)(OAc)(4)-catalyzed Oxonium Ylide formation/[2,3] sigmatropic rearrangement in a one-flask operation and in a highly diastereoselective manner. The methodology has been demonstrated in a concise synthesis of the anti-HIV agent hyperolactone C.
Huw M L Davies - One of the best experts on this subject based on the ideXlab platform.
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Highly Stereoselective Synthesis of Cyclopentanes bearing Four Stereocenters by a Rhodium Carbene–Initiated Domino Sequence
2016Co-Authors: Brendan T. Parr, Huw M L DaviesAbstract:Stereoselective synthesis of a cyclopentane nucleus by convergent annulations constitutes a significant challenge for synthetic chemists. Though a number of biologically relevant cyclopentane natural products are known, more often than not, the cyclopentane core is assembled in a stepwise fashion due to lack of efficient annulation strategies. Herein, we report the rhodium-catalyzed reactions of vinyldiazoacetates with (E)-1,3-disubstituted 2-butenols generate cyclopentanes, containing four new stereogenic centers with very high levels of stereoselectivity (99 % ee,>97: 3 dr). The reaction proceeds by a carbene–initiated domino sequence consisting of five distinct steps: rhodium–bound Oxonium Ylide formation, [2,3]-sigmatropic rearrangement, oxy-Cope rearrangement, enol–keto tautomerization, and finally an intramolecular carbonyl ene reaction. A systematic study is presented detailing how to control chirality transfer in each of the four stereo-defining steps of the cascade, consummating in the development of a highly stereoselective process
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Scope and Mechanistic Analysis of the Enantioselective Synthesis of Allenes by Rhodium-Catalyzed Tandem Ylide Formation/[2,3]-Sigmatropic Rearrangement between Donor/Acceptor Carbenoids and Propargylic Alcohols
2016Co-Authors: Vyacheslav Boyarskikh, Jorn H Hansen, Jochen Autschbach, Djamaladdin G Musaev, Huw M L DaviesAbstract:Rhodium-catalyzed reactions of tertiary propargylic alcohols with methyl aryl- and styryldiazoacetates result in tandem reactions, consisting of Oxonium Ylide formation followed by [2,3]-sigmatropic rearrangement. This process competes favorably with the standard O–H insertion reaction of carbenoids. The resulting allenes are produced with high enantioselectivity (88–98% ee) when the reaction is catalyzed by the dirhodium tetraprolinate complex, Rh2(S-DOSP)4. Kinetic resolution is possible when racemic tertiary propargylic alcohols are used as substrates. Under the kinetic resolution conditions, the allenes are formed with good diastereoselectivity and enantioselectivity (up to 6.1:1 dr, 88–93% ee), and the unreacted alcohols are enantioenriched to 65–95% ee. Computational studies reveal that the high asymmetric induction is obtained via an organized transition state involving a two-point attachment: Ylide formation between the alcohol oxygen and the carbenoid and hydrogen bonding of the alcohol to a carboxylate ligand. The 2,3-sigmatropic rearrangement proceeds through initial cleavage of the O–H bond to generate an intermediate with close-lying open-shell singlet, triplet, and closed-shell singlet electronic states. This intermediate would have significant diradical character, which is consistent with the observation that the 2,3-sigmatropic rearrangement is favored with donor/acceptor carbenoids and more highly functionalized propargylic alcohols
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scope and mechanistic analysis of the enantioselective synthesis of allenes by rhodium catalyzed tandem Ylide formation 2 3 sigmatropic rearrangement between donor acceptor carbenoids and propargylic alcohols
ChemInform, 2013Co-Authors: Vyacheslav Boyarskikh, Jorn H Hansen, Jochen Autschbach, Djamaladdin G Musaev, Huw M L DaviesAbstract:Reaction of carbenoids with propargylic alcohols results in tandem Oxonium Ylide formation/[2,3]-sigmatropic rearrangement to yield allenes with high enantioselectivity.
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scope and mechanistic analysis of the enantioselective synthesis of allenes by rhodium catalyzed tandem Ylide formation 2 3 sigmatropic rearrangement between donor acceptor carbenoids and propargylic alcohols
Journal of the American Chemical Society, 2012Co-Authors: Vyacheslav Boyarskikh, Jorn H Hansen, Jochen Autschbach, Djamaladdin G Musaev, Huw M L DaviesAbstract:Rhodium-catalyzed reactions of tertiary propargylic alcohols with methyl aryl- and styryldiazoacetates result in tandem reactions, consisting of Oxonium Ylide formation followed by [2,3]-sigmatropic rearrangement. This process competes favorably with the standard O–H insertion reaction of carbenoids. The resulting allenes are produced with high enantioselectivity (88–98% ee) when the reaction is catalyzed by the dirhodium tetraprolinate complex, Rh2(S-DOSP)4. Kinetic resolution is possible when racemic tertiary propargylic alcohols are used as substrates. Under the kinetic resolution conditions, the allenes are formed with good diastereoselectivity and enantioselectivity (up to 6.1:1 dr, 88–93% ee), and the unreacted alcohols are enantioenriched to 65–95% ee. Computational studies reveal that the high asymmetric induction is obtained via an organized transition state involving a two-point attachment: Ylide formation between the alcohol oxygen and the carbenoid and hydrogen bonding of the alcohol to a carb...
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enantioselective c c bond formation by rhodium catalyzed tandem Ylide formation 2 3 sigmatropic rearrangement between donor acceptor carbenoids and allylic alcohols
Journal of the American Chemical Society, 2010Co-Authors: Huw M L DaviesAbstract:The rhodium-catalyzed reaction of racemic allyl alcohols with methyl phenyldiazoacetate or methyl styryldiazoacetate results in a two-step process, an initial Oxonium Ylide formation followed by a [2,3]-sigmatropic rearrangement. This process competes favorably with the more conventional O−H insertion chemistry as long as donor/acceptor carbenoids and highly substituted allyl alcohols are used as substrates. When the reactions are catalyzed by Rh2(S-DOSP)4, tertiary α-hydroxycarboxylate derivatives with two adjacent quaternary centers are produced with high enantioselectivity (85−98% ee).
