The use of a [(ethylenediamine)(dppe)Ru(OCOtBu) 2 ] [dppe = 1,2-bis(diphenylphosphino)ethane] complex under base-free conditions allowed highly efficient and selective hydrogenation of aldehydes in the presence of ketones in addition to olefins. Even in the case of highly sensitive 1,6-ketoaldehydes, the desired ketoalcohols were obtained in high yields with 94-99 % overall selectivity at complete aldehyde conversion with a TON up to 30 000. The lack of requirement for strong basic co-catalysts and polar protic solvents also allowed efficient and highly chemoselective reduction of aldehydes bearing other functional groups, such as epoxides, carboxylic acids, esters, amides, and nitriles emphasizing the potential synthetic utility of the catalyst.The search for highly enantioselective chemical processes has been the main driving force towards the development of new synthetic catalytic methodologies for many years, probably related to the ever-growing number of optically pure drugs produced in the pharmaceutical industry.[1] Nevertheless, if astonishingly high enantiocontrol was achieved for a large number of chemical transformations, it was quite often done at the expense of process efficiency in terms of catalyst loadings and reaction scope. Initially introduced and further developed as a concept by Trost, [2] chemoselectivity was more recently claimed by Baran and co-workers [3] to be the key for further synthetic efficiency, especially to access highly complex molecules. Discovery of new chemoselective transformations should indeed allow some traditional retrosynthetic approaches to be reconsidered and avoid some tedious protection/deprotection sequences. New transformations should also be able to efficiently meet some increasing industrial requirements related to the environment with the potential to decrease the E-factor.Research towards highly efficient chemoselective processes has been nicely illustrated by recent developments in the reduction of carbonyl groups into alcohols. Noyori-type catalysts are widely used for the hydrogenation of ketones in the presence of olefins, even in the case of achiral transformations, thanks to their amazingly high catalytic activity.[4] Nevertheless, such catalysts were never reported for selective reduction of aldehydes in the presence of ketones, such a transformation represents a step further in chemoselectivity. This could be related to the general requirement for a strongly basic co-catalyst to achieve high catalytic efficiency, such conditions favoring the aldol side reaction. In addition to this, if aldehydes are known to be more reactive than ketones, some with only a slight difference in bond energy (about 5 kcal mol À1 ), it is a true obstacle to achieve high chemoselectivity results at complete aldehyde conversion. Also, several homogeneous catalysts, such as [Ir(H 3 )(PPh 3 ) 3 ], [RuCl 2 (PPh 3 ) 3 ], [Rh(cod)Cl] 2 / TPPTS (cod = 1,5-cyclooctadiene; TPPTS = tris(3-sulfophenyl)-phosphine trisodium salt), developed earlier were reported to exhibit some decent a...
