Fig. 1: Comparison of methods for the reductive coupling of aldehydes and ketones.

a Conventional routes involving the use of a metal salt as catalyst (M: = MgCl2, SmI2, NiCl2) and more than stoichiometric amounts of co-reducing metals (M = Mg, Al, Mn, Sm). 1–2 equivalents of SiR3Cl is also required to prevent catalyst inhibition through the coordination of diol60. b Current state-of-the-art photoreductive route catalysed by organometallic complexes based upon Ir(I) and Ru(II) in homogenous systems9. c Heterogeneous photoreductive route catalysed by MFM-300(Cr) described herein.