α′-Benzoyloxy and α′-methoxymethoxy lithium enolates giving opposite diastereofacial selectivities in aldol reactions. Use of (probable) extended chelation for reversal of stereoselectivities
作者:Anusuya Choudhury、Edward R. Thornton
DOI:10.1016/s0040-4039(00)77578-2
日期:1993.4
The Li enolates of α-benzoyloxy and α-methoxymethoxy ketones 1a and 1c afford nonchelation and chelation aldol products, respectively, both with usefully high diastereofacial selectivities. Evidence suggests that transition state chelation of the benzoyl C=O is responsible for the observed “nonchelation” stereoselectivity of 1a.
α苯甲酰和α-甲氧基甲氧基酮的烯醇化物锂1A和1C分别得到nonchelation和螯合羟醛产品,都是具有有用地高diastereofacial选择性。有证据表明,苯甲酰基C = O的过渡态螯合是观察到的1a “非螯合”立体选择性的原因。