Contrasting Regiochemistry in Thermal and Photochemical Allylstannations of 1,2Naphthoquinone

1,2-Naphthoquinone with (gamma)-substituted allyltin reagents undergoes both thermal and photochemical reactions, which show the opposite regioselectivities to each other. The both reactions are supposed to proceed via the initial 1,2-addition, which occurs at the (gamma)-position of the allyltin in the thermal reaction and at the less hindered (alpha)-position in the photoreaction, followed by the [3,3] allylic migration.