A Novel,Selective,and Efficient Route to Carotenoids and related Natural Products via Zr-Catalyzed Carboalumination and Pd- and Zn-catalyzed Cross Coupling

摘要

A highly efficient and stereoselective protocol for the syntheses of symmetrical and unsymmetrical carotenoids involving Zr-catalyzed carboalumination of conjugated oligoenynes and Pd- and Zn-catalyzed alkenyl-alkenyl coupling has been developed and applied to the syntheses of #beta#- and #gamma#-carotene and vitamin A.#gamma#-Carotene of >=99% isomeric purity was prepared in three linear steps (five steps overall) from #beta#-ionone,enyne 8,(E)-ICH = CHBr,and (E)-Me_3SiC ident to CCH=CHBr in 32% overall yield.