Clean catalysis with clean solvents - phosphonium tosylates for transfer hydrogenation reactions

Molten salts have been applied for the first time as solvents in rhodium-ca talysed transfer hydrogenation reactions. The salts are tetraalkyl/aryl pho sphonium tosylates; they are liquid at the reaction temperature and solid a t room temperature, thereby facilitating catalyst recovery. In certain case s they can give rise to favourable enantioselectivities.