Preparation of Perfluoroalkylated 1,2-Dihydropyrimidines and Pyrimidines

Significance

Reported is a preparation of 3-perfluorosubstituted 1,2-dihydropyrimidines from the simple starting materials ammonia, 2,2-dihydropolyfluoroalkylaldehydes and carbonyl compounds (or enol ethers) in the presence of zinc chloride. Both aliphatic aldehydes and ketones underwent the reaction readily, affording low to good yields, but their aromatic counterparts gave either no or very low yields of products. Reaction with the trimethylsilyl enol ether of cyclohexanone gave the corresponding spiro product. The substrate scope was relatively well studied and the product dihydropyrimidines were dehydrogenated to afford the corresponding pyrimidines, albeit only two cases were tested. A possible mechanism was proposed although no clear role for ZnCl₂ was assigned.