- Palladium-catalyzed intramolecular allylic alkylation of α-sulfinyl carbanions: a new asymmetric route to enantiopure γ-lactams
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Asymmetric intramolecular palladium-catalyzed allylic alkylation allowing access to disubstituted sulfinyl γ-lactams is described. The use of unsaturated amides bearing a sulfinyl group of defined absolute configuration together with enantiopure BINAP as
- Vogel, Sophie,Bantreil, Xavier,Maitro, Guillaume,Prestat, Guillaume,Madec, David,Poli, Giovanni
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scheme or table
p. 1459 - 1461
(2010/04/29)
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- Nitrilase-catalysed hydrolysis of cyanomethyl p-tolyl sulfoxide: stereochemistry and mechanism
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Several commercially available nitrilases have been used for the enantioselective hydrolysis of cyanomethyl p-tolyl sulfoxide into the corresponding amide and acid, which are formed in different proportions and with varying stereoselectivities, depending on the nitrilase involved. It was shown that the externally added amide is not transformed into the acid, which can be explained by assuming that both products must be produced in concurrent reactions. It was also demonstrated that the absolute configuration of the substrate exerts substantial influence on the product ratio. Two alternative explanations of the stereochemical course are presented.
- Kielbasinski, Piotr,Rachwalski, Michal,Mikolajczyk, Marian,Rutjes, Floris P.J.T.
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p. 562 - 567
(2008/09/20)
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- Highly stereoselective asymmetric pummerer reactions that incorporate intermolecular and intramolecular nonbonded S...O interactions
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New chiral sulfoxides (RS,S)-3, (SS,S)-3, (R S,S)-4, and (SS,S)-4 and known chiral sulfoxides (R S)-5, (RS)-6, and (RS)-7 were synthesized, and the stereochemistry of the new sulfoxides (RS,S)-3 and (R S,S)-4 was determined by X-ray crystallographic analysis. In their crystallographic structures, the intramolecular nonbonded S...O close contacts were recognized. Analyses of several sulfoxide complexes including rac-11 with N,N-dimethylacetamide (DMAC) or N-methyl-2-pyrrolidone (NMP) in a MeOH solution utilizing cold-spray ionization mass spectrometry provided, for the first time, direct information for intermolecular nonbonded S...O interactions between sulfoxides and amide (or lactam) in a solution. Highly diastereoselective and enantioselective Pummerer reactions based on the concept of intermolecular and intramolecular nonbonded S...O interactions were performed by treatment of several chiral sulfoxides (RS, S)-3, (SS, S)-3, (RS, S)-4, (SS, S)-4, (R S)-5, (RS)-6, and (RS)-7 with acetic anhydride and trimethylsilyl triflate (TMSOTf) in DMAC, NMP, N,N-dimethylformamide, and N-formylpiperidine. Mechanistic studies on these facile stereoselective Pummerer reactions revealed the necessity for the amide/TMSOTf complex, such as 26 or 27, to be an efficient activation reagent for Ac2O and a trapping reagent for the released acetate ion, and that DMAC and NMP had a positive effect on this highly stereoselective chiral transfer reaction.
- Nagao, Yoshimitsu,Miyamoto, Satoshi,Miyamoto, Motoyuki,Takeshige, Hiroe,Hayashi, Kazuhiko,Sano, Shigeki,Shiro, Motoo,Yamaguchi, Kentaro,Sei, Yoshihisa
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p. 9722 - 9729
(2007/10/03)
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- Synthesis of (+/-)-10,22-Dioxokopsane and (+/-)-Kopsanone, Heptacyclic Indole Alkaloids. Synthetic and Mechanistic Studies
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The total synthesis of the heptacyclic indole alkaloids (+/-)-10,22-dioxokopsane (2) and (+/-)-kopsanone (3, X=O) is described.The imine 20 was condensed with β,β,β-trichloroethyl chloroformate to give the tetracyclic carbamate 21.Removal of the carbamate
- Magnus, Philip,Gallagher, Timothy,Brown, Peter,Huffman, John C.
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p. 2105 - 2114
(2007/10/02)
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