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Synlett 2012(6): 903-906  
DOI: 10.1055/s-0031-1290615
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Copper-Catalyzed Domino Reaction of 2-Haloanilines with Hydrazides: A New Route for the Synthesis of Benzo[e][1,2,4]triazine Derivatives

Han Guoa,b,, Jin Liua,b,, Xianxue Wanga,b, Guosheng Huang*a,b
a State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou 730000, P. R. of China
Fax: +86(931)8912582; e-Mail: hgs@lzu.edu.cn;
b Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province, Lanzhou 730000, P. R. of China
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Publication History

Received 30 November 2011
Publication Date:
15 March 2012 (online)

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Abstract

A copper-catalyzed domino reaction for the synthesis of benzo[e][1,2,4]triazine derivatives has been developed using readily available substituted 2-haloanilines and hydrazides as the starting materials. The procedure of the present method is mild, facile, and efficient.

Key words

benzo[e][1,2,4]triazine derivatives - 2-haloanilines - ­hydrazides - copper catalyst - domino reaction

1

These authors contributed equally to this work.

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Typical Procedure for the Synthesis of Benzo[ e ][1,2,4]triazine An oven-dried Schlenk tube was charged with Cu2O (2.9 mg, 0.02 mmol), Cs2CO3 (130.4 mg, 0.4 mmol), 1a (44 mg, 0.20 mmol) and 2a (41 mg, 0.3 mmol). The Schlenk tube was sealed, evacuated, and backfilled with nitrogen (3 cycles). Then DMF (0.5 mL) and 1,4-dioxane (0.5 mL) were added to the reaction tube. The reaction was stirred at 90 ˚C under N2 for 6 h. After cooling to r.t. the solvent was diluted with EtOAc (3 × 10 mL), washed with brine (3 × 10 mL), and dried over anhyd Na2SO4. After the solvent was evaporated in vacuo, the residues were purified by column chromatography, eluting with PE-EtOAc (20:1) to afford 31 mg (75%) of 3-phenylbenzo[e][1,2,4]triazine (3aa) as a yellow solid, mp 119-121 ˚C. ¹H NMR (400 MHz, CDCl3): δ = 8.77-8.74 (m, 2 H), 8.51 (dd, J = 8.4, 0.8 Hz, 1 H), 8.07 (d, J = 8.8 Hz, 1 H), 7.96-7.92 (m, 1 H), 7.83-7.78 (m, 1 H), 7.59-7.57 (m, 3 H). ¹³C NMR (100 MHz, CDCl3): δ = 160.0, 146.6, 141.2, 135.8, 135.6, 131.6, 130.3, 129.7, 129.3, 129.1, 128.9. IR (neat): 3368, 3060, 1506, 1329, 1016, 771, 699 cm-¹. HRMS: m/z calcd for C13H10N3 [M + H]+: 208.0870; found: 208.0871.