Allene formation by gold catalyzed cross-coupling of masked carbenes and vinylidenes

• DOI: 10.1073/pnas.0705809104
• Publication Date: 2007-08-14T00:54:28Z
• Authors: Vincent Lavallo; Guido D. Frey; Shazia Kousar; Bruno Donnadieu; Guy Bertrand
• Keywords: Allene; Propargyl; Trimethylsilyl; Cationic polymerization

Addition of a sterically demanding cyclic (alkyl)(amino)carbene (CAAC) to AuCl(SMe 2 ) followed by treatment with [Et 3 Si(Tol)] + [B(C 6 F 5 4 ] − in toluene affords the isolable [(CAAC)Au(η -toluene)] complex. This cationic Au(I) complex efficiently mediates catalytic coupling enamines and terminal alkynes yield allenes not propargyl amines as observed other catalysts. Mono-, di-, tri-substituted can be used, well aryl-, alkyl-, trimethylsilyl-substituted alkynes. The reaction tolerates hindered substrates is diastereoselective. general protocol directly couples two unsaturated carbon centers form three-carbon allenic core. most probably proceeds through an unprecedented “carbene/vinylidene cross-coupling.”