Reazioni di cicloaddizione tra 1,3-diazabuta-1,3-dieni e cheteni:sintesi di diidropirimidinoni e 4-immino-azetidinoni

The work of this Ph.D. thesis is an in depth study on [4+2] and [2+2] cycloaddition reactions of 1-(4-methylphenyl) and 1-benzyl-1,3-diaza-1,3-butadienes with different ketenes, usually generated from the corresponding acid halide in the presence of a base. Reaction with phenyl, diphenyl, chloro and ethoxycarbonylketenes are described and the mechanism involved is discussed. Moreover, thermal and photochemical ring expansion reactions of azetidinones to 5,6-dihydro-3H-pyrimidin-4-ones are studied. Finally, the [2+2] cycloaddition reactions of 1-benzyl-2,4-diphenyl-1,3-diaza-1,3-butadiene with some chiral ketenes, such as beta-(dimethylphenylsilyl)ketene, beta-menthoxyketene and Evans-Sjögren ketene are investigated. The results are analysed and rationalized also on the basis of computational calculations.