The acidifying effects of chlorine and bromine: Little difference
摘要:
Lithium diisopropylamide deprotonates ortho- and para-bromochlorobenzene randomly at the two halogen adjacent positions. Obviously for steric reasons, the bulkier base lithium 2,2,6,6-tetramethylpiperidide favors the attack in the vicinity of the chlorine rather than the bromine atom to the extent of 2 : 1. - At -75 degrees C, both 2-bromo-3-chlorophenyllithium and 3-bromo-2-chlorophenyllithium isomerize to give 2-bromo-6-chlorophenyllithium. The latter species can be directly generated from 1-bromo-3-chlorobenzene. (C) 1997 Elsevier Science Ltd.
作者:Jeffery A. Gladding、James P. Bacci、Scott A. Shaw、Amos B. Smith
DOI:10.1016/j.tet.2011.04.094
日期:2011.9
Studies directed toward the synthesis of the architecturally complex marine natural product sporolide B are described. Synthetic analysis suggested advanced hydroquinone and benzodiquinane fragments, which upon elaboration were successfully united via an ester linkage. Macrocyclization studies were then carried out, and although a novel macrocyclization product was obtained, subsequent studies revealed
描述了针对结构复杂的海洋天然产物孢子内酯 B 合成的研究。合成分析表明,先进的氢醌和苯二喹烷碎片在精心设计后通过酯键成功结合。然后进行了大环化研究,虽然获得了一种新的大环化产品,但随后的研究表明,C(6) 和 C(10) 处的叔羟基在空间上受阻,无法参与成功的大环化以提供孢子内酯 B。
Direct C–H Carboxylation Forming Polyfunctionalized Aromatic Carboxylic Acids by Combined Brønsted Bases
CO2 fixation into electron-deficient aromatic C–H bonds proceeds with the combined Brønsted bases LiO-t-Bu and LiO-t-Am/CsF/18-crown-6 (t-Am = CEtMe2) under a CO2 atmosphere to afford a variety of polyfunctionalized aromatic carboxylic acids.
在 CO 2气氛下,通过组合的布朗斯台德碱 LiO- t -Bu 和 LiO- t -Am/CsF/18-crown-6 ( t -Am = CEtMe 2 ) 将CO 2固定成缺电子芳族 C-H 键以提供多种多官能化芳族羧酸。