Hydroformylation of unsaturated esters and 2,3-dihydrofuran under solventless conditions at room temperature catalysed by rhodium N-pyrrolyl phosphine catalysts

Rhodium complexes of the type HRh(CO)L-3 (where L is an N-pyrrolyl phosphine, such as P(NC4H4)(3), PPh(NC4H4)(2), or PPh2(NC4H4)) were applied in the hydroformylation of less reactive unsaturated substrates, namely allyl acetate, butyl acrylate, methyl acrylate, 2,3-dihydrofuran and vinyl acetate. Even at room temperature, these catalysts enabled complete substrate conversion and high chemoselectivity towards the corresponding aldehydes. High conversion of vinyl acetate (88% in 6 h) to the branched aldehyde was obtained with HRh(CO)[P(NC4H4)(3)](3) at 25 degrees C. An increase of the turnover frequency, TOF, up to 2000 mol mol(-1) h(-1) was achieved in this reaction under 20 bar of syngas (H-2/CO = 1) at 80 degrees C. The introduction of chiral phosphines, BINAP or Ph-BPE, to this system resulted in the production of a branched aldehyde with enantioselectivity, ee, up to 44 and 81%, respectively. High activity combined with high enantioselectivity was achieved due to the formation of the mixed rhodium hydrides HRh(CO)[P(NC4H4)(3)](BINAP) and HRh(CO)[P(NC4H4)(3)](Ph-BPE), identified by the NMR method.