Oxidative Cross-Coupling through Double Transmetallation: Surprisingly High Selectivity for Palladium-Catalyzed Cross-Coupling of Alkylzinc and Alkynylstannanes
Two different organometallic reagents now can cross-couple together with the oxidative cross-coupling strategy. Palladium catalyzed oxidative cross-couplings of alkylzinc and alkynylstannane reagents using desyl chloride as the oxidant have been explored, which produce the desired Csp-Csp3 cross-coupling product in surprisingly high selectivity and yields. The current catalytic system tolerates the presence of beta-H, and the reactions using long chain alkyl zinc reagents gave the cross-coupling product in excellent yields and selectivities.
A novel bond formation through oxidative cross-coupling with desyl chloride as the oxidant has been investigated. The coupling can be carried out under mild conditions. The Csp3-center carbon was involved even in the presence of a β-H, and up to 90% of the desired cross-coupling product was obtained with the secondary Csp3-center substrate.