Optimization of Palladium-Catalyzed Polyene Cyclizations: Suppression of Competing Hydride Transfer from Tertiary Amines with Dabco and an Unexpected Hydride Transfer from 1,4-Dioxane
journal contributionposted on 03.01.2001, 00:00 by Stephen Y. W. Lau, Neil G. Andersen, Brian A. Keay
This paper demonstrates that both 1,2,2,6,6-pentamethylpiperidine (PMP) and 1,4-dioxane can act as hydride donors in palladium-catalyzed polyene cyclizations of 2 and 3. Studies using PMP-d3 and dioxane-d8 either incorporate a deuterium atom into the monosubstituted product or completely inhibit the hydride transfer so that the second ring closure occurs in high yield. Dabco is the best substitute for PMP.