A novel, selective, and efficient route to carotenoids and related naturalproducts via Zr-catalyzed carboalumination and Pd- and Zn-catalyzed cross coupling
F. Zeng et E. Negishi, A novel, selective, and efficient route to carotenoids and related naturalproducts via Zr-catalyzed carboalumination and Pd- and Zn-catalyzed cross coupling, ORG LETT, 3(5), 2001, pp. 719-722
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A highly efficient and stereoselective protocol for the syntheses of symmet
rical and unsymmetrical carotenoids involving Zr-catalyzed carboalumination
of conjugated oligoenynes and Pd- and Zn-catalyzed alkenyl-alkenyl couplin
g has been developed and applied to the syntheses of beta- and gamma -carot
ene and vitamin A. gamma -Carotene of greater than or equal to 99% isomeric
purity was prepared in three linear steps (five steps overall) from beta -
ionone, enyne 8, (E)-ICH=CHBr, and (E)-Me3SiC=CCH=CHBr in 32% overall yield
.