In a process for the accelerated reduction of organic substrates, selected from the group consisting of esters, amides, nitriles, acids, ketones, imines or mixtures thereof, they are reacted with an amine borane, sulfide borane or ether borane complex as a borane source in the presence of organic accelerator compounds containing either Lewis acidic or Lewis basic sites in their structure, of which the Lewis acidic site can coordinate with the carbonyl or nitrile or imine group of the substrate or the Lewis basic site can coordinate with the borane.