American Chemical Society
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Catalytic Asymmetric Petasis Reactions of Vinylboronates

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journal contribution
posted on 2016-02-18, 20:48 authored by Xianglin Shi, William F. Kiesman, Anna Levina, Zhili Xin
Binaphthol-catalyzed asymmetric Petasis reactions of salicylaldehydes with dibutyl vinylboronates and secondary amines in the presence of 4 Å molecular sieves (MS) afforded products with up to 99% ee in isolated yields of 39–94%. The 99% ee of the product indicated that the reaction by the binaphthol-catalyzed pathway was roughly 500 times faster than the uncatalyzed pathway. NMR experiments (1H and 11B) showed that the amine component played a role in triggering the reaction between the binaphthol catalyst and the vinylboronate in the catalytic reaction sequence. The 4 Å MS enhanced both the rate and enantioselectivity by effective removal of water from the reaction system. A novel rearrangement reaction of the unconjugated allylic amine Petasis reaction product to a conjugated allylic amine was also observed.