Synthesis of α-allenic aldehydes/ketones from homopropargylic alcohols using a visible-light irradiation system.

A visible-light irradiation tandem oxidative aryl migration/carbonyl formation reaction, mediated by K 2 S 2 O 8 and visible-light photoredox catalysis, has been discovered. The presented transformation provides a straightforward access to important α-allenic aldehyde/ketone derivatives from readily available homopropargylic alcohol derivatives in a regioselective manner of 1,4-aryl shift concomitant with carbonyl formation. The operational simplicity and broad substrate scope demonstrate the great potential of this method for the synthesis of highly functional α-allenic aldehyde/ketone derivatives.