Allene formation by gold catalyzed cross-coupling of masked carbenes and vinylidenes.
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(eta(2)-toluene)](+)[B(C(6)F(5))(4)](-) complex. This cationic Au(I) complex efficiently mediates the catalytic coupling of enamines and terminal alkynes to yield allenes and not propargyl amines as observed with other catalysts. Mono-, di-, and tri-substituted enamines can be used, as well as aryl-, alkyl-, and trimethylsilyl-substituted terminal alkynes. The reaction tolerates sterically hindered substrates and is diastereoselective. This general catalytic protocol directly couples two unsaturated carbon centers to form the three-carbon allenic core. The reaction most probably proceeds through an unprecedented "carbene/vinylidene cross-coupling."
Lavallo
Vincent
V
University of California Riverside-Centre National de la Recherche Scientifique Joint Research Chemistry Laboratory (Unité Mixte Internationale 2957), Department of Chemistry, University of California, Riverside, CA 92521-0403, USA.
Frey
Guido D
GD
Kousar
Shazia
S
Donnadieu
Bruno
B
Bertrand
Guy
G
D000466:Alkadienes / Q000138:chemical synthesis / Q000737:chemistry*; D002384:Catalysis; D003432:Cross-Linking Reagents / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D006838:Hydrocarbons / Q000737:chemistry; D008697:Methane / Q000031:analogs & derivatives* / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D014753:Vinyl Compounds / Q000737:chemistry*
D000466:Alkadienes; D003432:Cross-Linking Reagents; D006838:Hydrocarbons; D014753:Vinyl Compounds; C030011:carbene; D006046:Gold; D008697:Methane
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