The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform
David J. Procter - One of the best experts on this subject based on the ideXlab platform.
-
metal free synthesis of benzothiophenes by twofold c h functionalization direct access to materials oriented heteroaromatics
Angewandte Chemie, 2019Co-Authors: Alexander P Pulis, Gregory J P Perry, David J. ProcterAbstract:: Due to their ubiquity in nature and frequent use in organic electronic materials, benzothiophenes are highly sought after. Here we set out an unprecedented procedure for the formation of benzothiophenes by the twofold vicinal C-H functionalization of arenes that does not require metal catalysis. This one-pot annulation proceeds through an interrupted Pummerer Reaction/[3,3]-sigmatropic rearrangement/cyclization sequence to deliver various benzothiophene products. The procedure is particularly effective for the rapid synthesis of benzothiophenes from non-prefunctionalized polyaromatic hydrocarbons (PAHs).
-
Metal-Free Synthesis of Benzothiophenes by Twofold C–H Functionalization: Direct Access to Materials-Oriented Heteroaromatics
Angewandte Chemie (International ed. in English), 2019Co-Authors: Jiajie Yan, Alexander P Pulis, Gregory J P Perry, David J. ProcterAbstract:Due to their ubiquity in nature and frequent use in organic electronic materials, benzothiophenes are highly sought after. Here we set out an unprecedented procedure for the formation of benzothiophenes by the twofold vicinal C-H functionalization of arenes that does not require metal catalysis. This one-pot annulation proceeds through an interrupted Pummerer Reaction/[3,3]-sigmatropic rearrangement/cyclization sequence to deliver various benzothiophene products. The procedure is particularly effective for the rapid synthesis of benzothiophenes from non-prefunctionalized polyaromatic hydrocarbons (PAHs).
-
transition metal free cross coupling of benzothiophenes and styrenes in a stereoselective synthesis of substituted e z 1 3 dienes
Angewandte Chemie, 2019Co-Authors: Mindaugas Siauciulis, Alexander P Pulis, Nanna Ahlsten, David J. ProcterAbstract:: A transition metal-free one-pot stereoselective approach to substituted (E,Z)-1,3-dienes was developed by using an interrupted Pummerer Reaction/ligand-coupling strategy. Readily available benzothiophene S-oxides, which can be conveniently prepared by oxidation of the parent benzothiophenes, undergo Pummerer coupling with styrenes. Reaction of the resultant sulfonium salts with alkyllithium/magnesium reagents generates underexploited hypervalent sulfurane intermediates that undergo selective ligand coupling, resulting in dismantling of the benzothiophene motif and the formation of decorated (E,Z)-1,3-dienes.
-
the interrupted Pummerer Reaction in a sulfoxide catalyzed oxidative coupling of 2 naphthols
Angewandte Chemie, 2019Co-Authors: Zhen He, Alexander P Pulis, David J. ProcterAbstract:: A benzothiophene S-oxide catalyst, generated in situ by sulfur oxidation with H2 O2 , mediates the oxidative coupling of 2-naphthols. Key to the catalytic process is the capture and inversion of reactivity of a 2-naphthol partner, using an interrupted Pummerer Reaction of an unusual benzothiophene S-oxide, followed by subsequent coupling with a second partner. The new catalytic manifold has been showcased in the synthesis of the bioactive natural products, (±)-nigerone and (±)-isonigerone. Although Pummerer Reactions are used widely, their application in catalysis is rare, and our approach represents a new catalytic manifold for metal-free C-C bond formation.
-
The interrupted Pummerer Reaction in a sulfoxide‐catalyzed oxidative coupling of 2‐naphthols
2019Co-Authors: Alexander P Pulis, David J. ProcterAbstract:A benzothiophene S‐oxide catalyst, generated in situ by sulfur oxidation with H2O2, mediates the oxidative coupling of 2‐naphthols. Key to the catalytic process is the capture and inversion of reactivity of a 2‐naphthol partner, using an interrupted Pummerer Reaction of an unusual benzothiophene S‐oxide, followed by subsequent coupling with a second partner. The new catalytic manifold has been showcased in the synthesis of the bioactive natural products, (±)‐nigerone and (±)‐isonigerone. Although Pummerer Reactions are used widely, their application in catalysis is rare, and our approach represents a new catalytic manifold for metal‐free C−C bond formation
Ken S Feldman - One of the best experts on this subject based on the ideXlab platform.
-
Extending Pummerer Reaction chemistry: studies in the palau'amine synthesis area.
The Journal of organic chemistry, 2011Co-Authors: Ken S Feldman, Ahmed Yimam NuriyeAbstract:Exploratory oxidative cyclization studies on cyclopentanelated and cyclohexenelated oroidin derivatives utilized Pummerer chemistry to generate pentacyclic structures related to the palau’amine family of sponge metabolites. Stereochemical issues were paramount, and appropriate choice of annelated ring size led to formation of the pentacyclic framework with complete diastereoselectivity for all of the core bonds.
-
extending Pummerer Reaction chemistry application to the assembly of the pentacyclic core of dibromopalau amine
Organic Letters, 2010Co-Authors: Ken S Feldman, Ahmed Yimam NuriyeAbstract:A pentacyclic model system featuring the trans azabicyclo[3.3.0]octane unit of dibromopalau’amine was prepared with complete diastereoselectivity in the polycyclic core from a tricyclic precursor. The key transformations of this sequence include (a) a Pummerer Reaction-mediated oxidative bicyclization, and (b) a Wolff rearrangement-based ring contraction to deliver the strained azabicyclo[3.3.0]octane core.
-
extending Pummerer Reaction chemistry dibromoagelaspongin synthesis and related studies
Journal of Organic Chemistry, 2009Co-Authors: Ken S Feldman, Matthew D FodorAbstract:The sponge-derived alkaloid dibromoagelaspongin was prepared from a dihydrooroidin derivative by exploiting the Pummerer Reaction twice in succession. Oxidative cyclization of the substrate's pyrrole-2-carboxamide function into the imidazole moiety was achieved in a regiospecific manner to establish both C-N bonds to C(6) of the target.
-
extending Pummerer Reaction chemistry examination of the prospects for forming vicinal quaternary carbon centers
Tetrahedron Letters, 2009Co-Authors: Ken S Feldman, Ahmed Yimam NuriyeAbstract:Pummerer chemistry applied to 2-sulfinyl indoles promotes oxidative cyclization of pendant nucleophiles to furnish C(3) spirocyclic indolenine products. Use of tetrasubstituted silyl enol ether nucleophiles in this transform yields spirocycles featuring vicinal all-carbon quaternary centers in two cases, but fails when a nearby amine can intervene.
-
extending Pummerer Reaction chemistry application to the total synthesis of dibromoagelaspongin
Journal of the American Chemical Society, 2008Co-Authors: Ken S Feldman, Matthew D FodorAbstract:The sponge metabolite dibromoagelaspongin was synthesized in 16 steps from imidazole. The route features two successive oxidative cyclizations with complete control of regiochemistry to deliver the unusual triaminomethane core of the target. These oxidative cyclizations likely resulted from Pummerer-like processes on the imidazole-2-sulfoxide (sulfide) precursors.
Hideki Yorimitsu - One of the best experts on this subject based on the ideXlab platform.
-
c f arylation of polyfluorophenols by means of sigmatropic dearomatization defluorination sequence
Chemistry: A European Journal, 2020Co-Authors: Koichi Okamoto, Keisuke Nogi, Jun Shimokawa, Hideki YorimitsuAbstract:Selective C-F arylation of polyfluorophenols with aryl sulfoxides has been accomplished by means of a sigmatropic dearomatization/defluorination sequence. This sequence consists of three processes: 1) interrupted Pummerer Reaction to form S-O-tethered sulfonium salt; 2) C-C-forming [3,3] sigmatropic rearrangement with dearomatization; and 3) Zn-mediated defluorinative rearomatization. The present biaryl construction provides a facile access to polyfluorinated biaryls that is difficult to synthesize by other methods. The synthetic utility of the strategy is clearly demonstrated by the synthesis of a fluorinated analogue of Maxipost, a potassium channel modulator.
-
sigmatropic dearomatization defluorination strategy for c f transformation synthesis of fluorinated benzofurans from polyfluorophenols
Angewandte Chemie, 2018Co-Authors: Koichi Okamoto, Kei Murakami, Mitsuki Hori, Tomoyuki Yanagi, Keisuke Nogi, Hideki YorimitsuAbstract:Facile synthesis of fluorinated benzofurans from polyfluorophenols has been accomplished by means of a sigmatropic dearomatization/defluorination strategy composed of three processes: (1) interrupted Pummerer Reaction of ketene dithioacetal monoxides with polyfluorophenols followed by [3,3] sigmatropic rearrangement, (2) Zn-mediated smooth reductive removal of fluoride from the dearomatized intermediate, and (3) acid-promoted cyclization/aromatization. Mechanistic investigations revealed important characteristic reactivity of polyfluorophenols in the present system. Some of the fluorinated benzofuran products were transformed by utilizing the 2-methylsulfanyl moieties.
-
cascades of interrupted Pummerer Reaction sigmatropic rearrangement
Chemical Record, 2017Co-Authors: Hideki YorimitsuAbstract:A new class of Pummerer chemistry has emerged as a powerful tool in organic synthesis. The new technology consists of a beautiful cascade of an interrupted Pummerer Reaction and the subsequent [3,3] sigmatropic rearrangement. The interrupted Pummerer Reactions of alkenyl or aryl sulfoxides with unsaturated nucleophiles such as allylic silanes, ketones, and phenols provide sulfonium intermediates, which are ready to undergo smooth charge-accelerated [3,3] sigmatropic rearrangement with excellent to exclusive regioselectivity. Some of the transformations proceed with transient loss of aromaticity. The Reactions afforded five-membered heterocycles, benzofurans, and biaryls of importance, depending on the sulfoxides and nucleophiles used. The Reactions are unique and game-changing because they are efficient, robust, redox-neutral, regioselective, and metal-free, which perfectly fits the need of modern organic synthesis. This chemistry also underscores the synthetic potential of organosulfur chemistry.
-
metal free approach to biaryls from phenols and aryl sulfoxides by temporarily sulfur tethered regioselective c h c h coupling
Journal of the American Chemical Society, 2016Co-Authors: Tomoyuki Yanagi, Kei Murakami, Hideki Yorimitsu, Keisuke Nogi, Shinya Otsuka, Yuko Kasuga, Keisuke Fujimoto, Atsuhiro OsukaAbstract:We have developed metal-free regiocontrolled dehydrogenative C–H/C–H cross-coupling of aryl sulfoxides with phenols by means of trifluoroacetic anhydride. Because the Reaction would proceed through an interrupted Pummerer Reaction followed by sulfonium-tethered [3,3]-sigmatropic rearrangement, the C–H/C–H coupling takes place exclusively between the ortho positions of both substrates. Various functional groups including carbonyl, halo, siloxy, and even boryl moieties are compatible. The biaryl products naturally possess hydroxy and sulfanyl groups, which allows the products to be useful synthetic intermediates, as evidenced by the syntheses of π-expanded heteroarenes such as unprecedented 7,12-dioxa[8]helicene.
-
Metal-Free Approach to Biaryls from Phenols and Aryl Sulfoxides by Temporarily Sulfur-Tethered Regioselective C–H/C–H Coupling
2016Co-Authors: Tomoyuki Yanagi, Kei Murakami, Hideki Yorimitsu, Keisuke Nogi, Shinya Otsuka, Yuko Kasuga, Keisuke Fujimoto, Atsuhiro OsukaAbstract:We have developed metal-free regiocontrolled dehydrogenative C–H/C–H cross-coupling of aryl sulfoxides with phenols by means of trifluoroacetic anhydride. Because the Reaction would proceed through an interrupted Pummerer Reaction followed by sulfonium-tethered [3,3]-sigmatropic rearrangement, the C–H/C–H coupling takes place exclusively between the ortho positions of both substrates. Various functional groups including carbonyl, halo, siloxy, and even boryl moieties are compatible. The biaryl products naturally possess hydroxy and sulfanyl groups, which allows the products to be useful synthetic intermediates, as evidenced by the syntheses of π-expanded heteroarenes such as unprecedented 7,12-dioxa[8]helicene
Alexander P Pulis - One of the best experts on this subject based on the ideXlab platform.
-
metal free synthesis of benzothiophenes by twofold c h functionalization direct access to materials oriented heteroaromatics
Angewandte Chemie, 2019Co-Authors: Alexander P Pulis, Gregory J P Perry, David J. ProcterAbstract:: Due to their ubiquity in nature and frequent use in organic electronic materials, benzothiophenes are highly sought after. Here we set out an unprecedented procedure for the formation of benzothiophenes by the twofold vicinal C-H functionalization of arenes that does not require metal catalysis. This one-pot annulation proceeds through an interrupted Pummerer Reaction/[3,3]-sigmatropic rearrangement/cyclization sequence to deliver various benzothiophene products. The procedure is particularly effective for the rapid synthesis of benzothiophenes from non-prefunctionalized polyaromatic hydrocarbons (PAHs).
-
Metal-Free Synthesis of Benzothiophenes by Twofold C–H Functionalization: Direct Access to Materials-Oriented Heteroaromatics
Angewandte Chemie (International ed. in English), 2019Co-Authors: Jiajie Yan, Alexander P Pulis, Gregory J P Perry, David J. ProcterAbstract:Due to their ubiquity in nature and frequent use in organic electronic materials, benzothiophenes are highly sought after. Here we set out an unprecedented procedure for the formation of benzothiophenes by the twofold vicinal C-H functionalization of arenes that does not require metal catalysis. This one-pot annulation proceeds through an interrupted Pummerer Reaction/[3,3]-sigmatropic rearrangement/cyclization sequence to deliver various benzothiophene products. The procedure is particularly effective for the rapid synthesis of benzothiophenes from non-prefunctionalized polyaromatic hydrocarbons (PAHs).
-
transition metal free cross coupling of benzothiophenes and styrenes in a stereoselective synthesis of substituted e z 1 3 dienes
Angewandte Chemie, 2019Co-Authors: Mindaugas Siauciulis, Alexander P Pulis, Nanna Ahlsten, David J. ProcterAbstract:: A transition metal-free one-pot stereoselective approach to substituted (E,Z)-1,3-dienes was developed by using an interrupted Pummerer Reaction/ligand-coupling strategy. Readily available benzothiophene S-oxides, which can be conveniently prepared by oxidation of the parent benzothiophenes, undergo Pummerer coupling with styrenes. Reaction of the resultant sulfonium salts with alkyllithium/magnesium reagents generates underexploited hypervalent sulfurane intermediates that undergo selective ligand coupling, resulting in dismantling of the benzothiophene motif and the formation of decorated (E,Z)-1,3-dienes.
-
the interrupted Pummerer Reaction in a sulfoxide catalyzed oxidative coupling of 2 naphthols
Angewandte Chemie, 2019Co-Authors: Zhen He, Alexander P Pulis, David J. ProcterAbstract:: A benzothiophene S-oxide catalyst, generated in situ by sulfur oxidation with H2 O2 , mediates the oxidative coupling of 2-naphthols. Key to the catalytic process is the capture and inversion of reactivity of a 2-naphthol partner, using an interrupted Pummerer Reaction of an unusual benzothiophene S-oxide, followed by subsequent coupling with a second partner. The new catalytic manifold has been showcased in the synthesis of the bioactive natural products, (±)-nigerone and (±)-isonigerone. Although Pummerer Reactions are used widely, their application in catalysis is rare, and our approach represents a new catalytic manifold for metal-free C-C bond formation.
-
The interrupted Pummerer Reaction in a sulfoxide‐catalyzed oxidative coupling of 2‐naphthols
2019Co-Authors: Alexander P Pulis, David J. ProcterAbstract:A benzothiophene S‐oxide catalyst, generated in situ by sulfur oxidation with H2O2, mediates the oxidative coupling of 2‐naphthols. Key to the catalytic process is the capture and inversion of reactivity of a 2‐naphthol partner, using an interrupted Pummerer Reaction of an unusual benzothiophene S‐oxide, followed by subsequent coupling with a second partner. The new catalytic manifold has been showcased in the synthesis of the bioactive natural products, (±)‐nigerone and (±)‐isonigerone. Although Pummerer Reactions are used widely, their application in catalysis is rare, and our approach represents a new catalytic manifold for metal‐free C−C bond formation
Matteo Zanda - One of the best experts on this subject based on the ideXlab platform.
-
the non oxidative chloro Pummerer Reaction novel stereospecific entry to vicinal chloroamines and aziridines
ChemInform, 2003Co-Authors: Alessandro Volonterio, Pierfrancesco Bravo, Cristina Pesenti, Walter Panzeri, Matteo ZandaAbstract:This article describes a new, useful synthetic tool, the “Non-Oxidative” Chloro-Pummerer Reaction (NOCPR), which allows for the use of enantiomerically pure α-Li alkylsulfoxides as chiral α-chloroalkyl carbanions with N-protected imines. In this Reaction the sulfinyl group of N-alkoxycarbonyl-β-sulfinylamines derived from aryl-, fluoroalkyl- and alkylimines is displaced by a chlorine atom in a one-pot Reaction with clean stereoinversion at carbon. Several 1,2-chloroamines produced via NOCPR were transformed into the corresponding aziridines. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)
-
the non oxidative chloro Pummerer Reaction a highly stereoselective entry to β chloro amines and aziridines
Tetrahedron Letters, 2001Co-Authors: Alessandro Volonterio, Pierfrancesco Bravo, Cristina Pesenti, Matteo ZandaAbstract:Abstract Enantiomerically pure α-Li alkyl-sulfoxides can be used as chiral α-chloroalkyl carbanions with N -protected imines by means of the ‘non-oxidative’ chloro-Pummerer Reaction (NOCPR). This novel methodology allows for a one-pot displacement of a sulfinyl group by chlorine from N -alkoxycarbonyl β-sulfinylamines derived from aryl, fluoroalkyl and alkyl imines, with clean stereoinversion at carbon. Several 1,2-chloroamines produced via NOCPR were transformed into the corresponding aziridines.
-
the non oxidative Pummerer Reaction conclusive evidence for s n 2 type stereoselectivity mechanistic insight and synthesis of enantiopure l alpha trifluoromethylthreoninate and d alpha trifluoromethyl allo threoninate 1
Journal of Organic Chemistry, 2000Co-Authors: Marcello Crucianelli, Pierfrancesco Bravo, Eleonora Corradi, Alberto Arnone, Stefano Valdo Meille, Matteo ZandaAbstract:Enantiopure methyl d-α-trifluoromethyl-allo-threoninate 18 and l-α-trifluoromethylthreoninate 19 were synthesized using (R)-ethyl p-tolylsulfoxide as chiral α-hydroxyethyl anion equivalent. The key step was the SN2-type replacement of the sulfinyl auxiliary with a hydroxy group, via trifluoroacetic anhydride promoted “non-oxidative” Pummerer Reaction (NOPR) of the diastereomeric intermediate β-sulfinyl amines 14 and 15, obtained by condensation of (R)-ethyl p-tolylsulfoxide 13 with the N-Cbz imine of methyl trifluoropyruvate 12. The conclusive evidence for SN2-type stereoselectivity of the NOPR was achieved by X-ray diffraction of both the starting diastereomer 14 and the p-bromobenzoate 25, obtained from the threoninate 19. NMR monitoring of the NOPR performed on 15 allowed the detection of a transient intermediate, which was identified as the four membered cyclic σ-sulfurane 27. This intermediate spontaneously rearranged (40 min, rt) into the corresponding sulfenamide 17, probably via an intramolecular ...
-
asymmetric synthesis of α arylglycinols via additions of lithium methyl p tolyl sulfoxide to n pmp arylaldimines followed by non oxidative Pummerer Reaction
ChemInform, 1999Co-Authors: Pierfrancesco Bravo, Fiorenza Viani, Marcello Crucianelli, Stefano Valdo Meille, Silvia Capelli, Maurizia Guidetti, Andrey L Markovsky, Vadim A Soloshonok, Alexander E Sorochinsky, Matteo ZandaAbstract:Abstract The results presented in this paper demonstrate that the stereochemical outcome of the reversible additions of lithium (R)-methyl p-tolyl sulfoxide to N-arylidene-p-anisidines (N-PMP imines) is a function of a) the Reaction conditions used and b) the electronic properties of the arylidene moiety on the starting imine. High kinetically controlled (2S,RS) diastereoselectivity (−70 °C) was achieved for additions of imines bearing relatively electron-rich N-arylidene groups, while an electron-deficient nature of this group was found to favor the opposite stereochemical outcome. On the other hand, the Reactions run under thermodynamically controlled conditions (0 °C) afforded equimolar mixtures of the diastereomeric products regardless of the pattern of substitution on the starting imines. Enantiopure α-arylglycinols were readily synthesized by “non-oxidative” Pummerer rearrangement of diastereomerically pure β-aryl-β-N-(acyl)aminoalkyl sulfoxides, prepared from the corresponding N-PMP derivatives.
-
asymmetric synthesis of α arylglycinols via additions of lithium methyl p tolyl sulfoxide to n pmp arylaldimines followed by non oxidative Pummerer Reaction
Tetrahedron, 1999Co-Authors: Pierfrancesco Bravo, Fiorenza Viani, Marcello Crucianelli, Stefano Valdo Meille, Silvia Capelli, Maurizia Guidetti, Andrey L Markovsky, Vadim A Soloshonok, Alexander E Sorochinsky, Matteo ZandaAbstract:Abstract The results presented in this paper demonstrate that the stereochemical outcome of the reversible additions of lithium (R)-methyl p-tolyl sulfoxide to N-arylidene-p-anisidines (N-PMP imines) is a function of a) the Reaction conditions used and b) the electronic properties of the arylidene moiety on the starting imine. High kinetically controlled (2S,RS) diastereoselectivity (−70 °C) was achieved for additions of imines bearing relatively electron-rich N-arylidene groups, while an electron-deficient nature of this group was found to favor the opposite stereochemical outcome. On the other hand, the Reactions run under thermodynamically controlled conditions (0 °C) afforded equimolar mixtures of the diastereomeric products regardless of the pattern of substitution on the starting imines. Enantiopure α-arylglycinols were readily synthesized by “non-oxidative” Pummerer rearrangement of diastereomerically pure β-aryl-β-N-(acyl)aminoalkyl sulfoxides, prepared from the corresponding N-PMP derivatives.
