Metal complex formation in carbonyl and imine additions

Metal Complex Formation in Carbonyl and Imine Additions 

The neighborhood of heteroatoms can increase the acidity of vicinal CH-bonds so that carbanions may be created by metalation. 

For instance, the metalation-alkylation of cyclic formamidines such as 425 can be used for introducing two on-ring methyl groups with high bis-equatorial selectivity to form 427 via 426 [133]. If, however, urethanes 428 are used for activation, the 

The diastereofaciality of organometal additions to carbonyl bonds is strongly influenced by precomplexation with suitable Lewis acids (chelate-Cram mechanism) [134]. 

The formation of a complex with the reagent is another possibility for stereochemical control, strongly depending on the solvent 

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See also in sourсe #XX -- [ , , , ]

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