In Situ-Generated Iodonium Ylides as Safe Carbene Precursors for the Chemoselective Intramolecular Buchner Reaction

A chemoselective intramolecular Buchner reaction employing iodonium ylides as safe carbene precursors has been developed. Iodonium ylides are generated in situ from N-benzyl-2-cyanoacetamides and PhI(OAc)2 in the presence of base and undergo intramolecular Buchner reaction under catalysis from Cu(OAc)2·H2O, affording fused cyclohepta-1,3,5-triene derivatives in up to 85% yield. The N,N-dibenzyl-2-cyanoacetamides with two different benzyl groups undergo intramolecular Buchner reaction on their electron-rich benzyl groups selectively. The reaction is not sensitive to air and moisture and uses a safe alternative version of the corresponding diazo starting materials. The overall transformation involving the carbene pathway has been verified.