Oxidative rearrangement of internal alkynes to give one-carbon-shorter ketones via manganese porphyrins catalysis.

Oxidative rearrangement of internal alkynes catalyzed by manganese(III) porphyrin is described, which opens a new access to one-carbon-shorter ketones using molecular oxygen. Under the standard conditions, a variety of alkynes including diarylalkynes and arylalkylalkynes rearranged smoothly to the corresponding ketones in high yields. Based upon experimental observations, a plausible reaction mechanism is proposed.