Asymmetric syntheses of 1,6-dialkyl-1,4-cyclohexadiene derivatives
摘要:
Ortho-lithiation-alkylation of tertiary benzamide 3 provides a series of 2-substituted chiral benzamides 3a-g (Scheme 1). Birch reduction of 3a-j followed by alkylation of the resulting chiral amide enolate with MeI at -78-degress-C gives 1,6-di-alkyl-1,4-cyclohexadiene derivatives 4a-j with excellent diastereoselectivities (Table I). Applications of this asymmetric synthesis are illustrated by conversions of 4g to enantiomerically pure bicyclic lactone 9 and octalone 11 (Scheme III) and 4j to hexahydro-9-anthracenone 14 (Scheme IV).
Synthesis of Enantiopure Bicyclic α,α-Disubstituted Spirolactams via Asymmetric Birch Reductive Alkylation
作者:Stéphanie M. Guéret、Patrick D. O’Connor、Margaret A. Brimble
DOI:10.1021/ol8029017
日期:2009.2.19
The synthesis of enantiopure bicyclic α,α-disubstituted spirolactams is described using a diastereoselective Birchreductive alkylation as the key step. Hydrogenation of the resultant alkylated cyclohexadienes followed by intramolecular cyclization provides access to enantiopure 8-azaspiro[5.6]dodecan-7-ones.