New Facile Synthesis of 2-Alkylthiopyrimidin-4(3H)-ones by Tandem Aza-Wittig Reaction Starting from the Baylis–Hillman Adducts

Iminophosphoranes reacted with CS 2 at –5 °C to produce the isothiocyanates, which were treated with primary amine to give thioureas in 73–91% yields. The subsequent reaction of thioureas with alkyl bromides in the presence of solid K 2 CO 3 produced 2-alkylthiopyrimidin-4(3 H )-ones in 68–88% yield via tandem intramolecular cyclization–isomerization–S-alkylation.