Regioselective Synthesis of Multisubstituted Furans via Metalloradical Cyclization of Alkynes with α-Diazocarbonyls: Construction of Functionalized α-Oligofurans

摘要

Co(III)-carbene radicals generated from activation of α-diazocarbonyls by Co(II) porphyrin complexes have been shown to undergo a new type of tandem radical addition reaction with alkynes to construct 5-membered furan structures. Cobalt(II) complex of 3,5-Di^tBu-IbuPhyrin, [Co(>P1)], has proven to be effective in catalyzing the metalloradical cyclization reaction under neutral and mild conditions. The [Co(>P1)]-catalyzed process is suitable to a wide range of α-diazocarbonyls and terminal alkynes with varied steric and electronic properties, producing polyfunctionalized furans with complete regioselectivity. The catalytic synthesis features a high degree of functional group tolerance and can be applied for construction of functionalized α-oligofurans through an iterative radical cyclization procedure.