Diastereoselective deprotonative metalation of chiral ferrocene derived acetals and esters using mixed lithium–cadmium and lithium–zinc combinations
作者:Gandrath Dayaker、Aare Sreeshailam、D. Venkata Ramana、Floris Chevallier、Thierry Roisnel、Shinsuke Komagawa、Ryo Takita、Masanobu Uchiyama、Palakodety Radha Krishna、Florence Mongin
DOI:10.1016/j.tet.2014.02.010
日期:2014.3
derivative in 74% yield with 90% de (SP diastereoisomer) using the base generated from CdCl2 and Li(TMP) (3 equiv), and in 85% yield with 91% de (SP diastereoisomer) through a double asymmetric induction using a chiral lithium–zinc base generated from ZnCl2·TMEDA and lithium (R)-bis(1-phenylethyl)amide (4 equiv). In contrast, using a combination prepared from ZnCl2 and Li(TMP) (4 equiv) with the ferrocene carboxylate
原位双金属组合,尤其是由MCl 2(TMEDA)(M = Zn,Cd; TMEDA = N,N,N',N'-四甲基乙二胺)和Li(TMP)(3或4当量,TMP = 2筛选了(2,6,6-四甲基哌啶子基)具有手性基团的非对映选择性去质子化二茂铁的能力。使用由CdCl 2和Li(TMP)(3当量)生成的碱,由双丙酮d-葡萄糖生成的二茂铁羧酸盐以74%的产率提供90%的de(S P非对映异构体)相应的2-碘衍生物。收率91%de(S P非对映异构体)通过使用由ZnCl 2 ·TMEDA和锂(R)-双(1-苯乙基)酰胺(4当量)生成的手性锂锌基双不对称诱导。相比之下,使用由ZnCl 2和Li(TMP)(4当量)制备的组合物与由6-(叔丁氧羰基氨基)-6-脱氧-3- O-甲基-1,2- O-异亚丙基获得的二茂铁羧酸盐-α- d -glucofuranose导致ř P分离之后碘在57%衍生物的产率。在分离的S