1, 3‐azaphospholo[5, 1‐<i>b</i>]thiazolines and benzothiazoles

Abstract

Abstract The title compounds 3 and 7 are novel heterocyclic systems incorporating two‐coordinate phosphorus. They are obtained in reasonable to good yields from the condensation of suitable 2‐ethyl‐3‐alkylthiazolinium and ‐benzothiazolium bromides 2 and 6 with phosphorus trichloride in the presence of triethylamine in an aprotic solvent. Intermediate dichlorophosphino‐substituted N‐ylides can be observed or isolated in some cases. From a 2‐methyl‐3‐alkylthiazolinium bromide ( 2a ), a 1‐(dichlorophosphino) substituted 1, 3‐azaphospholo[5,1‐b]thiazoline ( 4 ) was obtained. The chemical shift of the two‐coordinate phosphorus in 1,3‐azaphosphole derivatives clearly reflects the influence of the heterocyclic system annulated to its 1,5‐bond and of the substituents in its 2‐and 4‐positions.