Selective Iron-Catalyzed Deaminative Hydrogenation of Amides

Abstract

The five-coordinate iron(II) hydride complex (iPrPNP)Fe(H)CO (iPrPNP = N[CH2CH2(PiPr2)]2) was found to selectively catalyze deaminative hydrogenation of amides to the corresponding amines and primary alcohols. It is one of the most active amide hydrogenation catalysts reported to date, with turnover numbers (TONs) in excess of 1000 observed for multiple substrates and TONs greater than 4000 obtained for activated formanilides. The amide C–N cleavage reactions occur with a preference for electron-withdrawing substituents and with greater activity for formamides compared with acetamides and benzamides. Stoichiometric reactions between (iPrPNP)Fe(H)CO and formanilide afforded the new iron(II) complex (iPrPNHP)Fe(H)CO(N(Ph)HCO) resulting from N–H addition across the Fe–N bond. Complexes of this type were identified as the resting state during catalytic hydrogenation reactions containing secondary amides. Addition of a Lewis acid cocatalyst provided further enhancement of the productivity of catalytic amide hy...