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Synlett 2010(15): 2285-2288  
DOI: 10.1055/s-0030-1258030
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Synthesis of Tetrahydropyrrolo[1,2-a]quinoxalines and Tetrahydro­pyrido[1,2-a]quinoxalines via a One-Pot CuI-Catalyzed Aryl Amination-Hydrolysis-Condensation Process

Lanting Xua, Yongwen Jiangb, Dawei Ma*b
a Department of Chemistry, Fudan University, Shanghai 200433, P. R. of China
b State Key Laboratory of Bioorganic and Natural Products Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Lu, Shanghai 200032, P. R. of China
Fax: +86(21)64166128; e-Mail: madw@mail.sioc.ac.cn;
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Received 27 May 2010
Publikationsdatum:
19. August 2010 (online)

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Abstract

CuI-catalyzed coupling of 2-halotrifluoroacetanilides with l-proline or pipecolinic acid in DMSO at 90-110 ˚C followed by in situ hydrolysis at 100 ˚C afforded tetrahydropyrrolo[1,2-a]quinoxalines or tetrahydropyrido[1,2-a]quinoxalines.

Key words

catalysis - coupling - heterocycle - quinoxaline - one-pot process

9

General Procedure for the Synthesis of Quinoxaline Derivatives: A Schlenk tube was charged with 2-iodo-trifluoroacetanilide (0.5 mmol), CuI (10 mg, 0.02 mmol), l-proline (or pipecolinic acid) (1.5 mmol), and K2CO3 (1.0 mmol) (for bromide, Cs2CO3 was used). The tube was evacuated and backfilled with argon. DMSO (4 mL) was added into the tube. The reaction mixture was stirred at 90 ˚C (for bromide, 110 ˚C) for 10-24 h. Then H2O (3 mL) was added and the reaction mixture was stirred at 100 ˚C for 8-12 h. After the reaction mixture was cooled, sat. NH4Cl (10 mL) solution was added. The mixture was extracted with EtOAc and the organic layer was washed with H2O, brine and dried over Na2SO4. After concentration in vacuo, the residue was purified by column chromatography on silica gel (eluting with 6:1 → 4:1 PE-EtOAc) to provide the desired product.