Synthesis of $β$-carbonyl phosphonates using ozonolysis

Abstract

β-Carbonyl phosphonates were prepared by the ozonolysis of the corresponding allylic phosphonate. Alkylation of the allylic phosphonate was performed by treatment of the allylic phosphonate with butyllithium, followed by addition of alkyl halide. The α-alkylated β-carbonyl phosphonates were obtained by the ozonolysis of the corresponding α-alkylated allylic phosphonates. The availability of allylic phosphonate permitted us a new, easy, and efficient multigram preparation of β-carbonyl phosphonates by reductive ozonolysis. Mono- and spirocyclic β-ketovinyl phosphonates were prepared by domino ozonolysis-aldol sequence. The γ-alkylated β-keto phosphonates were prepared by γ-alkylation with allyl or homoallyl halide via α,γ-dianion in good yields. Ozonolysis of β-keto-w-alkenyl phosphonates afford to the mixture of acyclic dicarbonyl compound and the corresponding cyclized β-ketovinyl phosphonates were accomplished by the addition of TsOH and $Et_3N$ as catalyst. The domino ozonolysis-aldol cyclization is a rapid and efficient method for preparing cyclic five-, six-membered cyclic β-ketovinyl phosphonates with various substituted patterns.