Synthesis of Highly Functionalized Pyrrolidines via a Selective Iodide-Mediated Ring Expansion of Methylenecyclopropyl Amides
作者:Mark E. Scott、Mark Lautens
DOI:10.1021/jo802049u
日期:2008.11.7
iodide-mediated, tandem Mannich/cyclization to afford trans-2,3-disubstituted pyrrolidines from methylenecyclopropyl amides in good to excellent yields and selectivities. The reaction scope has been drastically expanded to include a wide array of aromatic, heteroaromatic and alpha,beta-unsaturated imines, as well as a variety of methylenecyclopropyl amides. Additionally, mechanistic studies were carried out
SN-sulfinyl imines) afforded N-sulfinyl alkoxydienyl amines 4 with high diastereoselectivity. Functionalized enantiopure alkoxydienyl amines 5 were then easily obtained upon the selective removal of the chiral auxiliary under mild conditions. Moreover, the further hydrolysis of the alkoxydienyl moiety gave access to protected enantiopure β-keto amines 7.
Stereoselective Control of Planar α-Dimethylsulfonium Benzyl Carbanions. Synthesis of Optically Pure <i>trans</i>-Aziridines
作者:Yolanda Arroyo、Ángela Meana、J. Félix Rodríguez、M. Ascensión Sanz-Tejedor、Inés Alonso、José L. García Ruano
DOI:10.1021/jo900381b
日期:2009.6.5
(R)-N-Sulfinylimine and (S)-N-sulfinylimine react with the ylide derived from (S)-dimethyl-[2-(p-toluenesulfinyl)phenyl]sulfonium salt, affording trans-2,3-disubstituted aziridines. A complete trans selectivity in low facial diastereoselectivity is observed when the configuration at the sulfur atoms of the reagents is the same. Otherwise, when their configurations are different, the reaction evolved
Zinc-mediated Coupling Reaction of 2-Bromo-2,3,3,3-tetrafluoropropanoate with Various Chiral Imines. Simple and Effective Access to Optically Active α-Fluoro-α-(trifluoromethyl)-β-amino Esters
The reactions of benzyl 2-bromo-2,3,3,3-tetrafluoropropanoate with various types of chiral imines in the presence of zinc in THF at room temperature were revealed to afford the threo- and erythro-isomers of α-fluoro-α-(trifluoromethyl)-β-amino esters with high diasteremeric excesses in fair to good chemical yields.
Domino Imino-Aldol−Aza-Michael Reaction: One-Pot Diastereo- and Enantioselective Synthesis of Piperidines
作者:Manas K. Ghorai、Sandipan Halder、Raj Kumar Das
DOI:10.1021/jo101680f
日期:2010.11.5
Addition of alpha-arylmethylidene- or alpha-alkylidene-beta-keto ester enolate to N-activated aldimines via the imino aldol pathway followed by intramolecular aza-Michael reaction in a domino fashion has been developed, and a highly diastereoselective route to substituted piperidines is reported. Enantiopure piperidines are synthesized from chiral sulfinyl imines. Formation and the observed stereoselectivity of the products have been rationalized by mechanistic and computational studies.