Enantioselective Synthesis of Chiral 1,4-Enynes via Palladium-Catalyzed Branch-Selective Allylic C–H Alkylation

We
herein present the construction of a chiral 1,4-enyne featuring
tertiary or quaternary stereogenic center via Pd-catalyzed branch-,
enantio-, and diastereo­selective allylic C–H alkylation.
Alkynyl carbon bearing bulky substituents appeared to exhibit competitive
reaction performance, and the desired chiral 1,4-enynes were obtained
in up to 93% yield and with up to >20:1 b/l, >20:1 dr, and 98%
ee.
A gram-scale experiment, the feasible operation of benzothiazole ring,
and the preparation of the key intermediate to access (+)-Breynolide
and prostaglandin are represented as a demonstration of multifarious
synthetic utility in chemical synthesis.