Synthesis of spiro-4<i>H</i>-pyrazole-oxindoles and fused 1<i>H</i>-pyrazoles <i>via</i> divergent, thermally induced tandem cyclization/migration of alkyne-tethered diazo compounds
A thermally induced, substrate-dependent reaction of alkynyl diazocompounds has been developed. This transformation produces spiro-4H-pyrazole-oxindoles and fused 1H-pyrazoles in good to high yields from the corresponding alpha-cyano and alpha-sulfonyl diazocompounds. The salient features of this reaction include excellent chemoselectivity and atom-economy, mild reaction conditions, simple purification