Synthesis of Pyrimido[6,1-a]isoquinolines by the Reaction of Thriethyl Orthoformate with Enamines of 3,3-dialkyl-1,2,3,4-tetrahydroisoquinoline series

Abstract

Boiling (Z)-2-[3,3-dimethyl-3,4-dihydroisoquinolin-1(2H)-ylidene]acetamides in AcOEt/Ac₂O leads involves annelation of the pyrimidine ring to form 6,6-dimethyl-6,7-dihydro-2H-pyrimido[6,1-a]-isoquinolin-2-ones. Similarly, benzo[f]isoquinoline amides form in this reaction 12,12-dialkyl-11,12-dihydro-3H-benzo[f]pyrimido[6,1-a]isoquinolin-3-ones.