Ring-Opening Reactions of Donor–Acceptor Cyclopropanes with Some Enolizable Azaheterocyclic Thiones: S- versus N-Attack

Abstract We report ring-opening reactions of donor–acceptor (D–A) cyclopropanes with a variety of five- and six-membered enolizable azaheterocyclic thiones, using Sc(OTf)3 as catalyst in dichloromethane. The majority of these systems reacted through nucleophilic S-attack at the donor position of the cyclopropane. 5-Mercapto-1,3,4-triazoles were shown to give the products of formal N-attack, and systems bearing two external C-S bonds could react with two equivalents of D–A cyclopropane to generate difunctionalized azaheterocycles.