A Cs2CO3-mediated simple and selective method for the alkylation and acylation of 3,4-dihydropyrimidin-2(1H)-thiones

Alkyl and acyl derivatives of 3,4-dihydropyrimidin-2(1H)-thiones were synthesized in good to excellent yields in the presence of Cs2CO3, a mild base. The method evidences a selective S-alkylation when using acyl chlorides as efficient acylating agents at room temperature on the 2-thioxo-dihydropyrimidone moiety. A possible mechanistic interpretation of the different selectivities in case of alkylation and acylation was done with the help of a geometry optimization process.