Nickel-Catalyzed Cyclizations of Enoate Equivalents: Application to the Synthesis of Angular Triquinanes
作者:Jeongbeob Seo、Hélène Fain、Jean-Baptiste Blanc、John Montgomery
DOI:10.1021/jo9908389
日期:1999.8.1
Unsaturated acyloxazolidinones and alpha'-silyloxy enones were found to be effective substrates in nickel-catalyzed organozinc-promoted cyclizations. Both groups served as convenient enoate equivalents, whereas methyl enoates themselves were inefficient substrates. A five-step procedure for the conversion of dimethylcyclopentenone into a highly functionalized angular triquinane was developed utilizing this observation. The key step of the procedure involves a nickel-catalyzed reductive cyclization/Dieckmann condensation sequence involving a cyclic enone tethered to an unsaturated acyloxazolidinone or alpha'-silyloxy enone. The method was applied ina formal synthesis of pentalenene, pentalenic acid, and deoxypentalenic acid.