Synthesis of spiro-4 H -pyrazole-oxindoles and fused 1 H -pyrazoles via divergent, thermally induced tandem cyclization/migration of alkyne-tethered diazo compounds

A thermally induced, substrate-dependent reaction of alkynyl diazo compounds has been developed. This transformation produces spiro-4 H -pyrazole-oxindoles and fused 1 H -pyrazoles in good to high yields from the corresponding alpha-cyano and alpha-sulfonyl diazo compounds. The salient features of this reaction include excellent chemoselectivity and atom-economy, mild reaction conditions, simple purification and potential for large scale production.