Regioselective deacylation of 2,4-diacylaminopyrimidine derivatives by Lewis acids and crystal structures of two products

Abstract

Deacylation of 2,4-diacylamino derivatives of pyrimethamine and related diaminopyrimidines with tin(II) chloride or zinc chloride, in ethanol or propan-2-ol, affords 2-acyl-4-aminopyrimidines exclusively. Regioselective 4-deacylation was observed by ¹H NMR spectroscopy and established by crystallographic analysis of the 2,4-dipropionylpyrimidine 11 and the corresponding 4-amino-2-propionylpyrimidine deacylation product 17. The latter exists in the solid state as an unusual base-pair dimer linked by two pairs of equivalent hydrogen bonds.