Photoinduced Double 1,2-Carbon Migration toward All-Carbon Tetrasubstituted Olefins

A photochemical double 1,2-carbon migration approach was achieved as an efficient entry into all-carbon tetrasubstituted olefins from allenols. Key to the success is the use of FSO₂Cl, which plays a crucial triple role as an effective Cl⁺ synthon to facilitate semipinacol rearrangement, an electron acceptor to form electron donor-acceptor complexes, and a FSO₂^• precursor to trigger 1,2-carbonyl migration. The synthetic utility is further showcased by extending it to other radical precursors and diverse follow-up reactions.