Substitution of 2‐phosphaindolizines by bromine and by chlorophosphines

Abstract

Abstract Bromine does not add to phosphorus in a 2‐phosphaindolizine 1 but substitutes its 1‐position. The 1‐bromo derivatives 2 are best prepared with Br 2 /NEt 3 or N‐bromosuccinimide. Their hydrolysis is remarkable; it involves a debromination of C‐1, an oxidation of P and a selective opening of the P/C‐3 bond. PCl 3 also causes a substitution of the 1‐position. The resulting 1‐dichlorophosphino derivatives 5 easily undergo a substituent exchange at the exocyclic phosphorus. More 1‐phosphino derivatives are formed in the reaction of 1 with phenyl and diazaphospholyl dichlorophosphine.