Reactions of benzyl compounds with synthesis gas in the presence of ruthenium carbonyl iodides

Abstract

Benzyl compounds, PhCH₂X (X = OH, OCH₂Ph, OMe, OAc), react with CO/H₂ mixtures at 9-10 MPa and 220ºC in the presence of aqueous HI and [RU(CO)₃I₂]₂ to afford toluene, HX and polymers of the type H(C₇H₆)_nH(n = 2-6). The mechanism involves the initial dehydration of PhCH₂OH to (PhCH₂)₂O which disproportionates to toluene and benzaldehyde. Ruthenium, present mainly as [Ru(CO)₃I₃]^- and cis-Ru(CO)₄I₂, catalyses reduction of benzaldehyde back to benzyl alcohol or the production of polymers. The significance of these results to toluene formation in benzyl alcohol homologation reactions is discussed.