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Access to α-Arylglycines via Umpolung Carboxylation of Aromatic Imines with Carbon Dioxide.

Research paper by Chun-Xiao CX Guo, Wen-Zhen WZ Zhang, Hui H Zhou, Ning N Zhang, Xiao-Bing XB Lu

Indexed on: 05 Oct '16Published on: 05 Oct '16Published in: Chemistry - A European Journal



Abstract

A straightforward and transition-metal-free approach for the efficient synthesis of α-arylglycine derivatives from aromatic imines and carbon dioxide was enabled by umpolung carboxylation reaction. Various substituted diphenylmethimines underwent the carboxylation smoothly with carbon dioxide in the presence of potassium tert-butoxide and 18-crown-6 to give the corresponding carboxylated products in good to high yields. Besides the enhancement of solubility of potassium tert-butoxide in THF, 18-crown-6 also plays key roles in suppressing reverse protonation or 1, 3-proton shift isomerization as well as stabilizing the carboxylated intermediate.