1,2-aryl and 1,2-hydride migration in transition metal complex catalyzed diazo decomposition:: A novel approach to α-aryl-β-enamino esters

[GRAPHICS] N-Tosyl diazoketamines were prepared by addition of the ethyl alpha -diazoacetate anion to N-sulfonylimines. The diazo decomposition of the diazoketamines with Rh-2(OAc)(4) complex resulted in aryl migration to give alpha -aryl-beta -enamino esters in good yields and high stereoselectivity. The effect of the catalysts on the migratory aptitude of 1,2-aryl over 1,2-hydride migration was studied. A reaction mechanism involving a bridged phenonium ion is proposed.