Proline-mediated formation of novel chroman-4-one tetrahydropyrimidines

Abstract Novel tricyclic N -benzylated chroman-4-one tetrahydropyrimidine derivatives have been prepared through a multi-component reaction between various 2-substituted chroman-4-one derivatives, N -methylenebenzylamine and a catalytic amount of proline under mild reaction conditions. The tricyclic structure of 1a was determined by NMR spectroscopy and confirmed by X-ray crystallography. An additional product, 2a , was isolated from the reaction mixture and its structure and conformation were determined by a combination of theoretical (Monte Carlo conformational search) and NMR-based (NOE and 3 J HH couplings) conformational analysis. The NMR analysis revealed one preferred geometry for 1a and 2a in CHCl 3 solution.