Synthesis of pyrrolo[1,2- d] [1,4]diazecines through an alkyne-trigged sequence of cleavage/cyclization in 1-phenylethynyl substituted pyrrolo[1,2- a] pyrazines

Transformations of 2-methyl-1-R-1-phenylethynyl-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazines under the action of electron-deficient alkynes in aprotic and protic solvents were studied. 1-Phenyl-1-phenylethynyl substituted pyrrolopyrazine did not react with alkynes or gave complex reaction mixtures. 1-Alkyl substituted 1-phenylethynyl-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazines in protic solvents underwent expansion to 8-alkylidene-6-phenyl-1,2,3,8-tetrahydropyrrolo[1,2-d][1,4]diazecines. © 2022 Author(s).