In contrast, there are few reports on the use of asymmetric transfer hydrogenation, which can offer advantages in terms of practicality, in this particular application. Recently, Xiao et al. disclosed the use of Rh-based catalyst 2 in aqueous solution. 18 This gave impressive results and required careful control of pH for full reduction to occur. A racemic Ir(I)-catalysed transfer hydrogenation (using isopropanol as the hydrogen source) has been reported. 19 The closely related ...
