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Hydrazone Radical Promoted Vicinal Difunctionalization of Alkenes and Trifunctionalization of Allyls: Synthesis of Pyrazolines and Tetrahydropyridazines

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posted on 01.11.2013, 00:00 by Xiao-Yong Duan, Xiu-Long Yang, Ran Fang, Xie-Xue Peng, Wei Yu, Bing Han
The intramolecular addition of hydrazone radicals to carbon–carbon double bonds was achieved by using TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) or DIAD (diisopropyl azodicarboxylate) as the hydrazone radical initiator as well as the carbon radical scavenger. Consequently, alkenes were difunctionalized to afford pyrazolines and tetrahydropyridazines via C–N forming 5-exo-trig and 6-exo-trig cyclizations, respectively, and allyls were trifunctionalized to afford pyrazolines via C–N forming tandem 1,5-H-shift/5-exo-trig cyclizations under metal-free neutral conditions.