Abstract: Singlet carbenes add preferentially to the more substituted bond of 1, I- dimethylallene (1). to give methylenecyclopropanes 3 as the major product. In contrast, many triplet carbenes add with differing regioselectivity, giving the thermodynamically preferred isopropylidenecyclopropanes, 10. A mechanism involving an intermediate trimethylenemethane, 8, has been suggested for this product. This regioselectivity probe ...
