The borrowing hydrogen strategy has been applied to the ethylation of imines with an air-stable iron complex as precatalyst. This approach opens new perspectives in this area as it enables the synthesis of unsymmetric tertiary amines from readily available substrates and ethanol as a C2 building block. A variety of imines bearing electron-rich aryl or alkyl groups at the nitrogen atom could be efficiently reductively alkylated without the need for molecular hydrogen. The mechanism of this reaction, which shows complete selectivity for ethanol over other alcohols, has been studied experimentally and by means of DFT computations.
Keywords: amines; borrowing hydrogen; catalysis; ethylation; iron.
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