N-Trifluoromethanesulfonyl-heteroarylium salts give the C4-or C2-substituted products 4 or 5. 1 react with phosphanes 2 to By means of a similar procedure, bisphosphonium salts a and 1. are formed: Tht reaction of sodium azide (si, and 5 yields the iminophosphorane 10 via the intermediate 9.--