The Reduction of Triazolium and Tetrazolium Iodides with Sodium Borohydride

Abstract

Abstract The sodium borohydride reduction of azolium iodides containing two, three, or four nitrogen atoms in the ring was studied. 1,4,5-Trisubstituted tetrazolium iodides gave Δ2-tetrazolines, whereas 1,3,5-trisubstituted tetrazolium iodide yielded no reduction product. 1,3,4,5-Tetrasubstituted 1,2,4-triazolium iodides and 1,2-disubstituted 1,2,3-triazolium fluorosulfonate were reduced to Δ2-1,2,4-triazolines and Δ2-1,2,3-triazoline respectively, but 1,3,4,5-tetrasubstituted 1,2,3-triazolium iodides were not reduced at all. Both pyrazolium and imidazolium salts gave the corresponding azolidines. These results can be explained in terms of the characteristics of sodium borohydride, which reduces selectively the immonium moiety in azolium salts.