A new synthesis of substituted butenolides via cation-initiated ring expansion/elimination of β-lactones
摘要:
When treated with silver ion, gamma-bromo beta-lactones, available via bromolactonization, undergo a ring expansion/elimination reaction to afford substituted butenolides.
Experimental and Computation Studies on<i>Candida antarctica</i>Lipase B-Catalyzed Enantioselective Alcoholysis of 4-Bromomethyl-β-lactone Leading to Enantiopure 4-Bromo-3-hydroxybutanoate
作者:Jung Yun Lim、Nan Young Jeon、A-Reum Park、Bora Min、Bum Tae Kim、Seongsoon Park、Hyuk Lee
DOI:10.1002/adsc.201200901
日期:2013.6.17
including statins, were synthesized from rac‐4‐bromomethyl‐β‐lactone through kinetic resolution. Candida antarctica lipase B (CAL‐B) enantioselectively catalyzes the ring opening of the β‐lactone with ethanol to yield ethyl (R)‐4‐bromo‐3‐hydroxybutanoate with high enantioselectivity (E>200). The unreacted (S)‐4‐bromomethyl‐β‐lactone was converted to ethyl (S)‐4‐bromo‐3‐hydroxybutanoate (>99% ee), which can
the first time, telluronium cations demonstrated impressive catalytic properties at low loadings in three benchmark reactions: the Friedel–Crafts bromination of anisole, the bromolactonization of ω-unsaturated carboxylic acids and the aza-Diels–Alder between Danishefsky'sdiene and imines. The ability of telluronium cations to interact with a Lewis base through chalcogen bonding was demonstrated on the
硫属元素键合是由缺乏电极的硫属元素原子和路易斯碱之间发生的非共价相互作用引起的。在硫属元素中,碲是最强的路易斯酸,但 Te 基化合物很少用作有机催化剂。碲阳离子首次在三个基准反应中在低负载量下表现出令人印象深刻的催化性能:苯甲醚的 Friedel-Crafts 溴化、ω-不饱和羧酸的溴内酯化以及丹麦谢夫斯基二烯和亚胺之间的 aza-Diels-Alder。基于多核(17 O、31 P 和125 Te)NMR 分析和 DFT 计算证明了碲阳离子通过硫属元素键合与路易斯碱相互作用的能力。
A Convenient Method for Bromolactonization
作者:Richard C. Cambie、Peter S. Rutledge、Robyn F. Somerville、Paul D. Woodgate
DOI:10.1055/s-1988-27790
日期:——
Bromolactones are conveniently obtained from unsaturated acids, bromine, and thallium(I) carbonate.
Selenium-Catalyzed Halolactonization: Nucleophilic Activation of Electrophilic Halogenating Reagents
作者:Shelli R. Mellegaard、Jon A. Tunge
DOI:10.1021/jo048460o
日期:2004.12.1
Diphenyl diselenide catalyzes the halolactonization of unsaturated acids with N-halosuccinimides under mild conditions. The diselenide not only accelerates the reactions, but in some cases affords regiocontrol in favor of gamma-lactone products. Experiments show that the regioselectivity in favor of gamma-lactones is a result of kinetic rather than thermodynamic control.