Arylation of [6,6]-spiroacetal enol ethers: reactivity and rearrangement

Attempts to selectively arylate [6,6]-spiroacetal enol ethers at the 2-position delivered unexpected results. Palladium-mediated arylation conditions afforded the double-Heck product, whereas reaction with benzenesulfinic acid resulted in a facile rearrangement into the corresponding 5-phenylsulfonyl-3,4,5,6-tetrahydrochromans, providing access to 5-aryl-3,4,5,6-tetrahydrochroman and hexahydrochroman derivatives.