Morpholine Radical in the Electrochemical Reaction with Quinoline <i>N</i>-Oxide

Abstract

An electrochemical reaction between quinoline N-oxides and morpholine was developed by using Cu(OAc)2 as a catalyst, generating products of 4-aminoquinoline N-oxides in CH2Cl2 or 2-aminoquinoline N-oxides in CH3CN in good yields. With an increase in the amount of electricity passed, the product deoxygenates with the formation of aminoquinolines. The advantages of the reaction are mild conditions, room temperature, the use of morpholine rather than its derivatives, and the ability to control the process when the electrolysis conditions change. Bisubstituted quinoline has also been obtained. The redox properties of both individual participants of C–H/N–H cross-coupling and multicomponent systems were established by voltammetry and EPR methods. For the first time, the EPR spectrum of the morpholine radical was recorded at room temperature, and its magnetic resonance parameters were determined in CH2Cl2. Mechanisms for the catalytic reaction have been proposed. This is a simple and easy-to-perform method for introducing a morpholine substituent, important in medicinal chemistry and other fields, by C–H/N–H cross-coupling.

Keywords

• copper
• catalysis
• radical
• morpholine
• <i>N</i>-oxides
• electrochemistry