Synthesis of spiro-4H-pyrazole-oxindoles and fused 1H-pyrazoles via divergent, thermally induced tandem cyclization/migration of alkyne-tethered diazo compoundsElectronic supplementary information (ESI) available. CCDC 1506802 (2a), 1566162 (4a), and 1570779 (7). For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c7ob02802d

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. A thermally induced, substrate-dependent divergent outcome of alkynyl diazoamides for the synthesis of spiro-4 H -pyrazoles and fused 1 H -pyrazoles has been developed.