Heterocyclic rings are important structural scaffolds encountered in both natural and synthetic compounds, and their biological activity often depends on these motifs. We have found that direct photolysis of vinyldiazo compounds selectively leads to cyclopropenes, which contrasts with the same reactions under thermal conditions that favors the formation of pyrazoles. Once formed, these reactive cyclopropene intermediates undergo [3+2]-cycloaddition with diverse dipolar species to yield these highly prized heterocyclic scaffolds.
M. Bao, K. Łuczak, W. Chaładaj, M. Baird, D. Gryko, M. P. Doyle, „Photo-cycloaddition reactions of vinyldiazo compounds”, Nat. Commun.