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One-Pot Synthesis of 4-Substituted 3,4-Dihydro-3-methoxyisocoumarins via Carboxylation of α-Substituted 2-Lithio-β-methoxystyrenes with Carbon Dioxide

✍ Scribed by Kazuhiro Kobayashi; Toshiyuki Nagaoka; Yuu Shirai; Wataru Miyatani; Yuki Yokoi; Hisatoshi Konishi

Publisher
John Wiley and Sons
Year
2012
Tongue
German
Weight
177 KB
Volume
95
Category
Article
ISSN
0018-019X

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✦ Synopsis

Abstract

A new type of isocoumarins (=1__H__‐isochromen‐1‐ones=1__H__‐2‐benzopyran‐1‐ones), 4‐substituted 3,4‐dihydro‐3‐methoxyisocoumarins 2, can be obtained by a one‐pot process from α‐substituted 2‐bromo‐β‐methoxystyrenes 1. Thus, lithium 2‐(1‐aryl(or methyl)‐2‐methoxyethenyl)benzoates are conveniently generated via the Br/Li exchange between 1 and BuLi, followed by the action of CO~2~ on the resulting α‐substituted 2‐lithio‐β‐methoxystyrenes. Upon treating with concentrated HCl at room temperature, these lithium benzoates undergo lactonization to provide the desired 3,4‐dihydroisocoumarins 2 in relatively good yields.

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