Organomagnesium compounds asymmetric addition

Similar acryloyl imidazolidinones have been used for the asymmetric 1,4-addition of organomagnesium compounds in the presence of a Lewis acid. The diastereoselectivity is variable and was found to be highly depending on the nature of all substrates. ... 

The asymmetric addition of organomagnesium and organolithium reagents to a,P-unsaturated carbonyl compounds and especially imines can be achieved in situations where rigid chelation controls the geometry of the transition state. Stereospecific alkyl addition occurs in the case of a chiral leucine-derived imine to provide overall asymmetric alkyl addition to an a,P-unsaturated aldehyde (Scheme 107).380 381... 

The stereochemistry of addition of organomagnesium compounds to ketones is governed by similar factors to those influencing their addition to aldehydes (see Section 6.1.1). For addition of achiral organomagnesium compounds to a-chiral ketones, steric approach control is commonly observed, but chelation control may also operate [63, 64], It is noteworthy that a pioneering asymmetric synthesis — one of the first which could be regarded as virtually stereospecific, was of this type [65] ... 

Until recently, attempts to achieve asymmetric syntheses by reactions of achiral carbonyl compounds with achiral organomagnesium compounds in the presence of chiral ligands had met with only limited success (see p. 119). Recently, however, very promising results have been reported involving additions to ketones [52, 68] TADDOLs (a,a,a, a -tetraaryl-2,2-dimethyl-l,3-dioxolane-4,5-dimethanols, where the aryl groups are phenyl or 2-naphthyl) are particularly effective, as in the following example [52] ... 

Organoberyllium compounds react with aldehydes and ketones in a fashion similar to organomagnesium compounds. Reduction competes with addition, and (32) is quite effective for asymmetric reductions. ... 

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