proved to be detrimental (e.r. 58:42, entry 2). Moreover, substituting the cyclohexyl backbone with a diphenyl ethane motif (Al-3, entry 3) also resulted in a lower e.r. (80:20), relative to the parent catalyst Al-1. Finally, the impact of varying the X-ligand at the Al-center was studied. Whilst oxygen bridged dimer Al-4 was unselective under these reaction conditions (e.r. 48:52, entry 4), replacing the chloro ligand by fluorine preserved efficiency, resulting in only a minor drop in selectivity (e.r. 88:12, entry 5). Altering the reaction medium (e.g. to CH2Cl2 or MeCN) resulted in lowered reaction efficiency and therefore acetone was utilized for the remainder of this study (entries 6 and 7, for details see ESI). Interestingly, the reaction showed a significant concentration dependence (entry 8, for details see ESI) and running the reaction at c = 0.066 M was found to be ideal to furnish (+)-1 in e.r. 97:3 and 84% isolated yield. The loading of the n-Bu4Cl additive could also be lowered to 1.5 eq. without any significant loss to the yield or selectivity (entry 9). Under these optimized conditions, rapid deracemization of rac-1, with depletion of (-)-1, was observed by reaction monitoring and completion was reached after 100 min (Fig. ). An assessment of the effect of temperature on the enantioselectivity revealed a classical temperature dependence in the form of ln(e.r.) ∝ 1/T (Fig. ).