β-Deprotonation by lithium di-isopropylamide. Vinyl carbanions from oxygen heterocycles in the synthesis of carboxylic acids in the benzofuran, flavone, and coumarin series and in the regiospecific acylation of 2,6-dimethylchromone
作者:Ana M. B. S. R. C. S. Costa、Francis M. Dean、Michael A. Jones、Dennis A. Smith、Rajender S. Varma
DOI:10.1039/c39800001224
日期:——
Lithium di-isopropylamide at –70 °C can remove the α-proton from benzofuran in the absence of activating groups and the β-proton if such groups are present; in flavone and 4-methoxycoumarin β-deprotonation occurs readily and the carbanions are easily carboxylated giving acids not previously accessible, while in 2,6-dimethylchromone β-deprotonation is kinetically favoured allowing 3-acylation to be
在不存在活化基团的情况下,–70°C的二异丙基氨基化锂可从苯并呋喃中去除α-质子;如果存在此类基团,则可去除β-质子;黄酮和4-甲氧基香豆素中的β-去质子化很容易发生,碳负离子容易被羧化,产生以前无法获得的酸,而2,6-二甲基色酮中β-去质子化在动力学上是有利的,从而使3-酰化与传统的酰化反应分开进行。 2-甲基。