This review provides insights into the in situ generated radicals triggered carbon–carbon bond cleavage reactions.

A silver-mediated [3 + 2] cycloaddition of "CNN" and "CC" for constructing pyrazoles has been described. The "CNN" building block used is N-isocyanoiminotriphenylphosphorane, which is a stable, safe, easy-to-handle, and odorless solid isocyanide. The reaction is characterized by its mild conditions, broad substrate scope, and excellent functional group tolerance.

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A novel Cu(II)-catalyzed cyclization of α-diazo-β-oxoamides with amines has been developed, constituting a straightforward method to construct pyrrol-3(2H)-one rings. The intramolecular hydrogen bonding effect in α-diazo-β-oxoamides plays an essential role in this reaction. A plausible reaction mechanism involving divergent generation and subsequent [2 + 3] cyclization of ketene and α-diazoimine intermediates was proposed.