Reetz-Grignard compound

Table 10.3 shows how the Cram selectivity of the least Cram-selective addition reaction in Table 10.2 can be increased considerably by using Reetz-Grignard compounds. 

In the alkylation of a-chiral aldehydes with no ability to chelate with organometal-lic compounds such as Grignard reagents, erythro alcohols are usually obtained preferentially according to the Cram s rule [127], and high Cram selectivity can be achieved with alkyltitanium reagents developed by Reetz [128]. In contrast, application of amphiphilic alkylation to a-chiral aldehydes enables one to achieve the hitherto difficult anti-Cram selectivity, affording threo alcohols selectively as shown in Sch. 91 [125]. 

A number of other examples have been reported which involve highly selective Grignard or organolithium additions to carbohydrates. Unfortunately, no general trends for these complex systems have been observed. Hie selectivities reported are often specific for one substrate under a particular set of reaction conditions. Reetz has reviewed the chelation and nonchelation control addition reactions (not confined to organolithium or organomagnesium reagents) of a- and 3-aUcoxycarbonyl compounds. ... 

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