Five-membered Rings with Two Nonadjacent Heteroatoms with at least One Phosphorus, Arsenic, or Antimony

Abstract

This chapter deals with the characterization (chiefly by X-ray crystallography and 1 H, 13 C, and 31 P spectroscopy) of compounds with 1,3-azaphosphole, 1,3-oxaphosphole, 1,3-thiaphosphole, 1,3-selenaphosphole, 1,3-diphosphole, 1,3-diphospholyl anion, 1,3-azarsole, 1,3-thiarsole, 1,3-selenarsole, and 1,3-phospharsole rings. The synthesis of the unsubstituted 1,3-thiarsole and 1,3-thiaphosphole heterocycles has been achieved. Phosphaindolizines ([1,3]azaphospholo[1,5- a ]pyridines) can be efficiently prepared from pyridinium salts. Metal vapor reactions at 77 K with phosphalkynes produce sandwich compounds containing 1,3-diphospholyl anions. 1,3-Azaphospholes tend to react with electrophiles (or metal centers) at the phosphorus either as neutral heterocycles or as anions formed by N-deprotonation. Lithiation of N-substituted 1,3-benzazaphospholes takes place at C-2 to generate synthetically useful carbanionic nucleophiles. 2,4,6-Trisubstituted-1,3,5-triphosphabenzenes can be converted into 2,4,5-trisubstituted-1,3-diphospholyl anions which react with electrophiles to give 1-substituted-1,3-diphospholes. Phosphalkynes react with mesoionic compounds (e.g., münchnones) to give 1,3-oxa-, 1,3-thia-, or 1,3-azaphospholes.