Syntheses of 1,2‐Oxaphospholane 2‐Oxides and 1,2‐Oxaphosphole 2‐Oxides

Abstract 1,2‐Oxaphospholane and 1,2‐oxaphosphole 2‐oxides, γ‐phosphonolactones and γ‐phosphinolactones, also called γ‐phostones and γ‐phostines, are important five‐membered 1,2‐oxaphosphaheterocycles and crucial motifs of some biologically active compounds. Various synthetic methods of these 1,2‐oxaphosphaheterocycles have been developed till now. They can be divided as cyclization, annulation, cycloaddition, ring expansion and contractions. The cyclizations mainly include intramolecular nucleophilic substitution of 3‐haloalkylphosphonic and phosphinic acid derivatives, esterification of 3‐hydroxyalkylphosphonic/phosphinic acids, transesterification of alkyl 3‐hydroxyalkylphosphonates/phosphinates, halocyclization of alkyl alk‐2/3‐enylphosphonates, halocyclization of allenylphosphonic acid derivatives, the transition metal‐catalyzed oxidative cyclizations of benzyl/2‐methylphenylphosphonic/phosphinic acids, and the Pd‐catalyzed cyclization of γ‐bromoalkyl phosphonates/phosphinates. The annulations covers [4+1] and [3+2] annulations. In this review, we have described various strategies and further development for the synthesis of 1,2‐oxaphospholane and 1,2‐oxaphosphole 2‐oxides.