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Synlett 2009(20): 3283-3286  
DOI: 10.1055/s-0029-1218380
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

First Use of HEH in Oxazine Synthesis: Hydroxy-Substituted 2H-1,4-Benzoxazine Derivatives

Qing-yuan Meng, Qiang Liu*, Jing Li, Rui-Guang Xing, Xiao-Xia Shen, Bo Zhou
State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, P. R. of China
Fax: +86(931)8625657; e-Mail: liuqiang@lzu.edu.cn;
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Publication History

Received 29 July 2009
Publication Date:
18 November 2009 (online)

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Abstract

The synthesis of 2H-1,4-benzoxazine derivatives from 1,2-epoxy-3-(2-nitroaryloxy)propanes in the presence of Hantzsch 1,4-dihydropyridine (HEH) and Pd/C as a catalyst was achieved. The nitro group was reduced before the epoxide functionality, leading to attack of the amino group on the epoxide moiety in a 6-exo-fashion. By introducing a methyl group at the 1-position, the 7-endo ring-closed product could also be formed.

Key words

Hantzsch 1,4-dihydropyridine ester - organic reductant - hydrogen transfer - benzoxazine derivatives - domino reaction

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General procedure for the synthesis of 2,3-dihydro-1,4-benzoxazine derivatives: To a stirred solution of substrate (0.5 mmol) in ethanol (30 mL) was added HEH (0.468 g, 1.85 mmol), and 10% Pd/C (18 mg), and the reaction mixture was refluxed for 12 h under N2. The mixture was filtered through Celite and the filtrate was evaporated in vacuo. The residue was purified by column chromatography on silica gel to give the corresponding product.