Citation: Pd. Dey et al., REGIOSELECTIVE [4-ARYLAMINO SUBSTITUTED 1,3-DIAZA-1,3-BUTADIENES WITHKETENES - SYNTHESIS OF PYRIMIDINONE AND FUSED PYRIMIDINONE DERIVATIVES .2.(2]CYCLOADDITION VERSUS NUCLEOPHILIC REACTIONS OF N), Tetrahedron, 53(40), 1997, pp. 13829-13840