Base-induced Rearrangement of γ-Diketones. I. The Rearrangement of 1,2,2-Triphenyl-1,4-pentanedione to 1,3,3-Triphenyl-1,4-pentanedione

Abstract

Treatment of 4-hydroxy-2,2-diphenyl-3-pentenoic acid lactone (3) with phenyllithium gives 1,2,2-triphenyl-1,4-pentanedione (2), 1,3,3-triphenyl-1,4-pentanedione (7), and 3,3-diphenylpropiophenone (16). The γ-diketone 7 is shown to arise via rearrangement of an anion of the γ-diketone 2. The formation of 1,2,3-triphenyl-1,4-pentanedione (27) is not observed, nor is 27 converted to 7 on treatment with base. It is concluded that the rearrangement proceeds via two homoenolate anion intermediates rather than via two 1,2 phenyl shifts.