Fluorine⋅⋅⋅ and π⋅⋅⋅Alkali Metal Interactions Control in the Stereoselective Amide Enolate Alkylation with Fluorinated Oxazolidines (Fox) as a Chiral Auxiliary: An Experimental and Theoretical Study
作者:Gjergji Sini、Arnaud Tessier、Julien Pytkowicz、Thierry Brigaud
DOI:10.1002/chem.200701604
日期:2008.4.7
alpha-alkylation of amide enolates by using a pseudo-C(2) symmetry trans 4-phenyl-2-trifluoromethyloxazolidine (trans-Fox) as a chiral auxiliary occurs with an extremely high diastereoselectivity (>99 % de). The origin of this excellent stereocontrol was investigated by an experimental and theoretical (DFT) study. With this trans chiral auxiliary, both F...metal and pi...metal interactions compete to give
通过使用伪C(2)对称反式4-苯基-2-三氟甲基恶唑烷(trans-Fox)作为手性助剂,酰胺烯醇的α-烷基化会以极高的非对映选择性(> 99%de)发生。通过实验和理论(DFT)研究来研究这种出色的立体声控制的起源。借助这种手性助剂,F。金属和pi ...金属之间的相互作用通过烯醇盐的Reface烷基化竞争而得到相同的非对映异构体。在Re面和Si面侵蚀过渡态之间发现的5.5 kcal mol(-1)能量差与通过实验获得的完整非对映选择性是一致的。另一方面,在顺式手性助剂(cis-Fox)的情况下,F。金属和pi ...金属相互作用之间的竞争不利于非对映选择性。