Acceptorless dehydrogenation of alcohols and N-heterocycles was accomplished with well-defined and inexpensive iron-based catalysts supported by a cooperating PNP pincer ligand. Benzylic and aliphatic secondary alcohols were dehydrogenated to the corresponding ketones in good isolated yields upon release of dihydrogen. Primary alcohols were dehydrogenated to esters and lactones, respectively. Mixed primary/secondary diols were oxidized at the secondary alcohol moiety with good chemoselectivity. Cyclic amines are dehydrogenated to give quinolines. The reverse hydrogenation reactions were also observed under mild conditions. The active catalytic species in the dehydrogenation reaction, is independently synthesized, characterized, and its structure is confirmed by X-ray crystallography. A <i>trans</i>-dihydride intermediate is proposed to be involved in the hydrogenation reaction and its existence is verified by NMR and trapping experiments. The mechanism of the reaction was investigated using both experiment and DFT calculations and the crucial role of metal-ligand cooperativity in the reaction was elucidated.

Well-defined iron catalysts for the acceptorless reversible dehydrogenation of alcohols and N-heterocycles

249th National Meeting (2015)

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