作者:Lukas Hintermann、Antonio Togni
DOI:10.1002/1522-2675(20000906)83:9<2425::aid-hlca2425>3.0.co;2-v
日期:2000.9.6
3-dioxolane-4,5-dimethanolato(2−)-O,O′]titanium ((R)-1b) are efficient catalysts for the electrophilic enantioselective chlorination and bromination of β-keto esters with N-chlorosuccinimide (NCS) and N-bromosuccinimide (NBS), respectively. With 5 mol-% of catalyst at room temperature an enantioselectivity of up to 88% ee could be obtained for the chlorination reaction. Under comparable conditions, bromination
Ti(TADDOLato) 络合物二氯[(4R,5R)-2,2-二甲基-α,α,α',α'-四苯基-1,3-二氧戊环-4,5-二甲醇合(2-)-O, O']钛((R)-1a)和二氯[(4R,5R)-2,2-二甲基-α,α,α',α'-四(萘-1-基)-1,3-二氧戊环-4,5-二甲醇(2-)-O,O']钛((R)-1b)是β-酮酯与N-氯代琥珀酰亚胺(NCS)和N-溴代琥珀酰亚胺的亲电子对映选择性氯化和溴化的有效催化剂(国家统计局),分别。在室温下使用 5 mol-% 的催化剂,氯化反应可以获得高达 88% ee 的对映选择性。在可比较的条件下,溴化反应较慢且立体选择性较低。