A Dehydrogenative Homocoupling Reaction for the Direct Synthesis of Hydrazines from N-Alkylanilines in Air

Abstract

A copper-catalyzed N-N bond-forming reaction was performed by a dehydrogenative homocoupling of N-alkylanilines, affording N,N′-dialkyl-N,N′-diphenylhydrazines in 72-88% yields. This new strategy has the advantages of direct synthesis from N-alkylanilines, using air as the oxidant, convenient manipulations, mild reaction conditions and moderate to good yields. A possible mechanism by coordination and reductive elimination has been proposed.

homocoupling - oxidative dehydrogenation - copper catalyst - direct synthesis - hydrazine

References and Notes

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14

General Experimental Procedure: To a solution of N-alkylaniline 1 (0.107 g, 1.0 mmol) in DMF (2 mL) were added CuBr (0.029 g, 0.2 mmol), TMEDA (0.232 g, 2.0 mmol), CuO (0.016 g, 0.2 mmol), K₂CO₃ (0.276 g, 2.0 equiv) and 4 Å MS (0.1 g) successively, and the reaction mixture was stirred at 70 ˚C or 95 ˚C for 12-24 h in air. After the reaction was completed, the mixture was filtered, and the residue was washed with EtOAc (3 × 5 mL). Then, the combined filtrates were concentrated in vacuum, and the residue was purified by column chromatography (silica gel, PE-EtOAc as eluent) to afford the desired hydrazine 2.

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