Iminophosphorane-mediated synthesis of fused uracils. A facile one-pot preparation of pyrimido[4,5-d]pyrimidine derivatives

Article abstract of DOI:10.1016/S0040-4020(01)90083-3

The aza Wittig-type reaction of iminophosphoranes 3, 5-[(N-Arylimino)methyl]-6- [(triphenylphosphoranylidene)amino]-1,3-dimethyl uracils, with aromatic isocyanates leads to the functionalized pyrimido[4,5-d]pyrimidines 4. Iminophosphoranes 5, prepared from 3 by selective reduction with sodium borohydride, undergo dihydropyrimido annelation by reaction with isocyanates to give 7-amino-6-aryl-1,3-dimethyl-1,2,3,4,5,6- hexahydropyrimido[4,5-d]pyrimidines 6.