The possibility of generating azomethine ylides from 11H-benzo[4,5]imidazo[1,2-a]indol-11-one and amino acids is shown for the first time. Based on the cycloaddition reactions of these azomethine ylides with cyclopropenes and maleimides, cyclopropa[a]pyrrolizines, 3-azabicyclo[3.1.0]hexanes, and pyrrolo[3,4-a]pyrrolizines spiro-fused with a benzo[4,5]imidazo[1,2-a]indole fragment were synthesized. Spirocyclic compounds were obtained in moderate to good yields, albeit with poor diastereoselectivity. Density functional theory calculations were performed to obtain an insight into the mechanism of the 1,3-dipolar cycloaddition of 11H-benzo[4,5]imidazo[1,2-a]indol-11-one-derived azomethine ylides to cyclopropenes. The cytotoxic activity of some of the obtained cycloadducts against the human erythroleukemia (K562) cell line was evaluated in vitro by MTS-assay.

The oxidative cycloaddition of 3-subsituted quinazoline-2,4(1H,3H)-diones and alkynes has been developed. The reaction is Pd(II)-catalyzed and successfully occurs in the presence of Ag(I) oxidants. This transformation is assumed to proceed by N-H palladation of the quinazoline-2,4(1H,3H)-dione followed by ortho C-H activation. Using this methodology, a series of 5,6,7,8-tetraaryl-1H-azepino[3,2,1-ij]quinazoline-1,3(2H)-diones were obtained in moderate to good yields. The resulting tricyclic heterocycles can be converted by alkaline hydrolysis into 1H-benzo[b]azepine-9-carboxamide derivatives. DFT calculations have been carried out to shed light on the reaction mechanism.

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