Catalytic Enantioselective Protonation of Nitronates Utilizing an Organocatalyst Chiral Only at Sulfur
作者:Kyle L. Kimmel、Jimmie D. Weaver、Melissa Lee、Jonathan A. Ellman
DOI:10.1021/ja3026196
日期:2012.6.6
highly enantioselectiveprotonation of nitronates formed upon the addition of α-substituted Meldrum's acids to terminally unsubstituted nitroalkenes is described. This work represents the firstenantioselectivecatalytic addition of any type of nucleophile to this class of nitroalkenes. Moreover, for the successful implementation of this method, a new type of N-sulfinyl urea catalyst with chirality residing
An Efficient Method for Generation of α-Oxoketenes: Cycloreversion of Enolized Meldrum's Acid Derivatives
作者:Masayuki Sato、Hitoshi Ban、Chikara Kaneko
DOI:10.1016/s0040-4039(97)01566-9
日期:1997.9
synthesized from Meldrum'sacids. These dioxinones underwent 4+2 cycloreversion to methoxy- or siloxycarbonylketenes and ketones quantitatively at 20–50 °C. The ketenes were characterized by IR spectroscopy as well as by trapping with t-butanol. The ready cycloreversion of these enolized Meldrum'sacid derivatives strongly indicates that the anomalouslyhigh susceptibility of Meldrum'sacids to nucleophilic