Enol silanes, stereogenic diastereoselectivity

In the addition of an achiral enolate to an aldehyde bearing a stereogenic center at Ca, the jr-facial selectivity can usually be predicted by the Felkin-Anh model (158 see also Chapter 2) [83]. However, simple 1,2-diastereoin-duction with enolates derived from typical metals such as lithium, boron, and titanium is often insufficient to be synthetically useful [16, 20). Higher levels of diastereoselectivity are generally obtained by use of enol silanes [34], as reported by Heathcock (Equation 14) [84]. 

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