Synthesis of Phosphalilolidine and Phosphajulolidine

Article abstract of DOI:10.1021/jo00315a026

The successful syntheses and characterizations of the novel bicyclic C-P heterocycles 1,1,5,5,8-pentamethylphosphalilolidine (3) and 1,1,6,6,8-pentamethylphosphajulolidine (4) are described.Cyclization of 1-(methyl-p-tolylphosphinoyl)-3-methylbutan-2-ol (7) by using polyphosphoric acid at 120 deg C produced an inseparable, isomeric mixture (83percent yield) of 1,4,4,7- and 1,4,4,6-tetramethylphosphinoline oxides (8 and 9) in ratio of ca. 3:1.This isomerization is rationalized by a mechanism which involves the cationic ipso cyclization followed by migration of the phosphinoyl group.Cyclic voltammetric and UV spectroscopic data suggest that both phosphajulolidine and phosphalilolidine have essentially no n-? interaction between the lone-pair electrons on the phosphorus and the adjacent aromatic ? system.