A Simple Approach to Pyrimiaine and Quinazoline Derivatines by [4+2] Cycloaddition of 1,3-Diazadienes and Enamines
摘要:
The reaction of 2-trimethylsilyloxy- (1) and 2-trimethylsilylthio-1,3-diazabutadienes (2) with enamines derived from aliphatic aldehydes leads regio-and stereoselectively to substituted tetrahydropyrimidin-2(1H)-ones (3) and thiones (4) in high yields. Extension of this cycloaddition to cyclic enamines, e.g. derived from cyclohexanone, leading to quinazoline derivatives (9-10) is also described. These heterocycles undergo hydrolysis and dehydration to 3,4-dihydropyrimidine (7-8) and 3,4,5,6,7,8-hexahydroquinazoline (11-12) derivatives.