Palladium(II)-catalyzed ring enlargement of 2-(arylmethylene)cyclopropylcarbinols: strong effect of substituent electronic nature on the reaction pathway.

In the presence of Pd(II) catalyst and copper(II) bromide, 2-(arylmethylene)cyclopropylcarbinols undergo ring enlargement to deliver (arylcyclobutenyl)carbinols or hydrogenated furans in good yields under mild conditions; mechanisms accounting for the distinct products have been proposed on the basis of control and deuterium labeling experiments.