Selective Hydrosilylation of Esters to Aldehydes Catalysed by Iridium(III) Metallacycles through Trapping of Transient Silyl Cations.

The combination of an iridium(III) metallacycle and 1,3,5-trimethoxybenzene catalyses rapidly and selectively the reduction of esters to aldehydes at room temperature with high yields through hydrosilylation followed by hydrolysis. The ester reduction involves the trapping of transient silyl cations by the 1,3,5-trimethoxybenzene co-catalyst, supposedly by formation of an arenium intermediate whose role was addressed by DFT calculations.