Bidirectional Hiyama-Denmark cros-coupling reactions of bissilyldeca-1,3,5,7,9-pentaenes for the synthesis of symmetrical and non-symmetrical carotenoids

Abstract

The construction of the carotenoid skeleton by Pd‐catalyzed Csp2−Csp2 cross‐coupling reactions of symmetrical and non‐symmetrical 1,10‐bissilyldeca‐1,3,5,7,9‐pentaenes and the corresponding complementary alkenyl iodides has been developed. Reaction conditions for these bidirectional and orthogonal Hiyama–Denmark cross‐coupling reactions of bisfunctionalized pentaenes are mild and the carotenoid products preserve the stereochemical information of the corresponding oligoene partners. The carotenoids synthesized in this manner include β,β‐carotene and (3R,3′R)‐zeaxanthin (symmetrical) as well as 9‐cis‐β,β‐carotene, 7,8‐dihydro‐β,β‐carotene and β‐cryptoxanthin (non‐symmetrical).