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:——
Lithiumdi-isopropylamide at –70 °C can remove the α-proton frombenzofuran 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-dimethylchromoneβ-deprotonation is kinetically favoured allowing 3-acylation to be