Chemo- and Diastereoselective Synthesis of Spirooxindole-pyrazolines and Pyrazolones via P(NMe2)3-Mediated Substrate-Controlled Annulations of Azoalkenes with α-Dicarbonyl Compounds

P(NMe2)(3)-mediated substrate-controlledannulationsof azoalkenes with & alpha;-dicarbonyl compounds are reported, wherethe azoalkenes serve as either four or five-atom synthons chemoselectively.The azoalkene participates in annulation with isatins as a four-atomsynthon to furnish the spirooxindole-pyrazolines, whereas it functionsas a novel five-atom synthon in annulation with aroylformates, therebyleading to chemo- and stereoselective formation of pyrazolones. Thesynthetic utilities of the annulations have been demonstrated, anda novel TEMPO-mediated decarbonylation reaction is unveiled.

Automated summary

P(NMe2)(3)-mediated substrate-controlled annulations of azoalkenes with α-dicarbonyl compounds were studied. The azoalkenes can selectively act as either four or five-atom synthons. The reaction with isatins resulted in the formation of spirooxindole-pyrazolines as four-atom synthons, while the reaction with aroylformates led to chemo- and stereoselective formation of pyrazolones as five-atom synthons. The synthetic utilities of the annulations were demonstrated, and a novel TEMPO-mediated decarbonylation reaction was discovered.