Enantio- and Diastereoselective Aldol-Reaction of 2,6-Dimethylphenyl Propionate Using Titanium-Carbohydrate Complexes
作者:Rudolf O. Duthaler、Peter Herold、Susanne Wyler-Helfer、Martin Riediker
DOI:10.1002/hlca.19900730315
日期:1990.5.2
Chloro(cyclopentadienyl)bis(1,2:5,6-di-O-isopropylidene-α-D-glucofuranos-3-O-yl)titanium (1) is used for the transmetallation of Li-enolates obtained from propionyl derivatives. While such Ti-enolates of ketones and hydrazones appear to be unreactive, the (E)enolate 13 of 2,6-dimethylphenyl propionate (11) adds to the re-side of aldehydes, affording various syn-aldols 14 with high dia- and enantioselectivity
氯(环戊二烯基)双(1,2:5,6-二-O-异亚丙基-α-D-葡糖呋喃基-3- O-基)钛(1)用于从丙酰基衍生物获得的锂烯酸酯的金属转移。虽然酮和腙的这样的Ti-烯醇化物似乎是不反应的,所述(ê)烯醇化物13丙酸2,6-二甲基苯基的(11)增加了重新醛的侧的,得到各种顺-aldols 14具有高直径-和对映选择性(92-97%DS,91-97%ee的,比照。方案2和表1)。外消旋顺式-aldols(±) - 14类似地从非手性双(2-丙氧基)-Ti-烯酸酯15(方案2和表2)获得。与此相反的不稳定锂烯醇化物10,在Ti-烯醇化物13和15在-30℃,大概是为了在热力学上更稳定(异构化Ž)-enolates(方案4),虽然非手性烯醇化物的非对映选择性15被丢失时在这种平衡下,手性(Z)-烯酸酯27出乎意料地提供了抗羟醛12光学纯度高(94-98%ec),在大多数情况下,具有良好的非对映选择