Dehydrogenation of Aromatic Alcohols, Aldehydes, and Ketones Catalyzed by Cu(I) Complexes.

Herein, we report that binuclear copper complexes used as dehydrogenative catalysts, combined with oxygen as an oxidant and 2,2,6,6-tetramethylpiperidinyl-1-oxide (TEMPO) as an additive, are capable of effectively catalyzing the successive dehydrogenation of aromatic propanols to produce α,β-unsaturated aldehydes. This method has the advantages of high efficiency, simple operation, and oxygen as an oxidant. The reaction mechanism of continuous dehydrogenation of aromatic propanols was investigated by in situ infrared spectroscopy and control experiments. The dehydrogenation process suggested that phenylpropanol was first oxidized to arylpropanals and then underwent α,β-selective dehydrogenation of the carbonyl group to yield α,β-unsaturated aldehydes. This protocol provides insights into the design and synthesis of efficient catalysts for the preparation of α,β-unsaturated aldehydes by continuous dehydrogenation of aromatic propanols.