Chiral α,ω-dioxy-carbanions from 1,3-propanediol and 1,4-butanediol by sparteine-assisted deprotonation. Enantioselective synthesis of 1,3- and 1,4-diols, (R)-pantolactone, and a cyclopropane.
摘要:
Prostereogenic mono- and dicarbamates of 1,3-propanediol and 1,4-butanediol are deprotonated by the sec-butyllithium/(-)-sparteine system with high enantiotopic differentiation. The electrophilic substitution of the intermediate chiral carbanions furnishes the title compounds with >95% ee.
Enantioselective α-Arylation of O-Carbamates via Sparteine-Mediated Lithiation and Negishi Cross-Coupling
摘要:
A general and enantioselective arylation of carbamates derived from primary alcohols was developed by combining Hoppe's sparteine-mediated asymmetric lithiation with Negishi cross-coupling. Coupled with Aggarwal's lithiation-borylation sequence, the current method provides a short and divergent access to a variety of enantioenriched secondary and tertiary benzylic alcohols.