Helical Chiral 2-Aminopyridinium Ions: A New Class of Hydrogen Bond Donor Catalysts
摘要:
Helical chiral 2-aminopyridinium ions were designed as a significantly more acidic (active) dual hydrogen-bonding catalyst than commonly used (thio)urea-based systems. The heticene framework was specifically utilized to position an inherently chiral barrier on the hydrogen-bonding side of the catalyst. The catalyst reactivity and enantioselectivity were successfully demonstrated in additions of 4,7-dihydroindoles to nitroalkenes (0.5-2 mol % catalyst loadings, up to 98:2 er).
Helical Chiral 2,2′-Bipyridine <i>N-</i> Monoxides as Catalysts in the Enantioselective Propargylation of Aldehydes with Allenyltrichlorosilane
作者:Jinshui Chen、Burjor Captain、Norito Takenaka
DOI:10.1021/ol200102c
日期:2011.4.1
A highly enantioselective synthesis of homopropargylic alcohols is achieved by using the new helical chiral 2,2'-bipyridine N-monoxide catalyst and allenyltrichlorosilane. This method can be further extended to the enantio- and regioselective propargylation of N-acylhydrazones.