Formation of Enolates by Transmetallation

M2Y L , inter alia-. MgBr2, CIB(OMe)2, CIAIEt2, Sn(OTf)2, SnCl2, RsSnCI, CITI(0/Pr)3, CI2TICP2, ZnCl2 

Transmetallation is also a highly important concept to obtain enolates of the late transition metals rhodium, palladium, and nickel, not only for their preparation and isolation, but also for their intermediate generation in catalytic cycles. When 2 equiv. of the potassium enolates 166 of acetophenone and pinacolone 

Mukaiyama aldol reactions of silyl enol ethers are generally rationalized by a Lewis acid activation of the carbonyl group by in situ formation of a complex that reacts with the silyl enol ether or the silyl ketene acetal [99,167]. Transmetallation mechanisms according to which silicon is replaced under formation of a metal enolate have been discussed as well for catalytic versions of the reaction [168], in particular for late transition metals [169]. 

The formation of palladium enolates by cleavage of silyl enol ethers is a key step in palladium-catalyzed aldol reactions [170]. When, within the catalytic cycle, palladium diaquo complex 175 with chiral bis-phosphane ligands is allowed to react 

To a 20-ml vial were added as solids palladium complex 183 (250 mg, 0.345 mmol) tmd CHjClO-tBulOK (54 mg, 0.35 mmol), preptired from t-butylacetate and potassium hydride. The mixture was suspended in 5 ml of toluene tind stirred at room temperature for 30 min. When the reaction was complete, as indicated by P( H) NMR spectroscopy, the solution was filtered through Celite to remove residual salts. The resulting solution was concentrated. After crystallization from toluene, layer with pentane at —35°C, 

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