Copper(II) Hydroxide


[20427-59-2]  · CuH2O2  · Copper(II) Hydroxide  · (MW 97.56)

(catalyst for the Ullmann condensation;1 mediates conversion of acid hydrazides to carboxylic acids2)

Physical Data: d 3.37 g cm-3.

Solubility: sol acids, conc alkali, NH4OH, and ethylenediamine; insol water.

Form Supplied in: blue to blue-green gel or light blue crystalline powder.

Handling, Storage, and Precautions: may decompose to CuII oxide at 60-80 °C, although the stability is dependent on the method of preparation. Hygroscopic.

Aryl Amine Synthesis.

CuII hydroxide catalyzes the Ullmann condensation reaction of 1-bromoanthraquinone or 1-amino-4-bromoanthraquinone with a large excess of ethylenediamine (eq 1).1 The hydroxo-bridged CuI-CuII mixed valence complex formed by the reduction of CuII hydroxide has been proposed as an active species. Copper(II) Chloride and Copper(II) Bromide are ineffective. The combination catalyst of Copper(I) Chloride/Cu(OH)2 (2:1) shows a higher activity in the reaction of 1-amino-4-bromoanthraquinone than with CuCl2 alone, but still lower than with Cu(OH)2 alone.

Conversion of Acid Hydrazides to Carboxylic Acids.

A stoichiometric amount of CuII hydroxide, prepared in situ from CuCl2 and Potassium Hydroxide, effects conversion of acid hydrazides to carboxylic acids at room temperature (eq 2).2 Under similar reaction conditions, Cu(OAc)2.H2O and CuCO3 react slowly and CuCl2, Cu(NO3)2, CuSO4, and CuO are ineffective. Cu(OAc)2.H2O and CuCO3 are effective at 70 °C. In the presence of oxygen, Copper(II) Acetate acts as a catalyst at room temperature to afford carboxylic acids in excellent yields. An acyl cation intermediate generated by the oxidation of acid hydrazides with CuII hydroxide has been proposed. The copper-promoted conversion of acid hydrazides to carboxylic acids may provide a convenient method of protecting carboxylic acids bearing labile functional groups.

1. Arai, S.; Hashimoto, Y.; Yamagishi, T.; Hida, M. BCJ 1989, 62, 3143.
2. Tsuji, J.; Nagashima, T.; Qui, N. T.; Takayanagi, H. T 1980, 36, 1311.

Tetsuo Tsuda

Kyoto University, Japan

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