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Visible-light-catalyzed synthesis of 1,3-benzoxazines via formal [4 + 2] cycloaddition of oximes with o-hydroxybenzyl alcohols†
Zhenjie Qi,Zhenyu An,Bingbing Huang,Mingzhong Wu,Quansen Wu,Dongfang Jiang
Organic & Biomolecular Chemistry Pub Date : 07/25/2023 00:00:00 , DOI:10.1039/D3OB00882G
Abstract

A formal [4 + 2] cycloaddition of oximes with o-hydroxybenzyl alcohols was developed to easily synthesize diverse 1,3-benzoxazine derivatives. This synthesis was achieved under visible light-based organocatalytic and TsOH conditions. The reaction proceeds through the photoisomerization of oximes via visible light-mediated energy transfer, followed by the nucleophilic attack of o-QMs to oximes as a 1,2-dipole synthon, cyclization, and isomerization. The reaction exhibits a broad substrate scope and can be carried out under mild conditions. To demonstrate its synthetic usefulness, a gram-scale reaction was conducted, and the resulting 1,3-benzoxazine products were further transformed into other valuable compounds.

Graphical abstract: Visible-light-catalyzed synthesis of 1,3-benzoxazines via formal [4 + 2] cycloaddition of oximes with o-hydroxybenzyl alcohols
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