An Efficient Vinyl Sulfonium Salt Precursor for the Synthesis of Imidazolinium Salts

(2-Bromoethyl)diphenylsulfonium Trifluoromethanesulfonate (1) is a precursor of a vinyl sulfonium salt (2) which can be easily prepared by treatment with a base. 2 shows high electrophilicity and reacts with various nucleophiles,¹⁾ especially, in a case using formamidines as a nucleophile, imidazolinium triflates are given.²⁾ The remarkable point of this reaction is that even when bulky formamidines are used, the reaction rapidly proceeds to afford the desired products in high yields. Thus, this reaction is one of the efficient methods for the synthesis of NHC ligands.