| Abstract
| - The kinetics of the Al-catalyzed asymmetric Meerwein−Schmidt−Ponndorf−Verley (MSPV) reductionare presented. Structural identification of the catalytic precursor formed in situ between (S)-2,2‘-dihydroxy-1,1‘-binapthyl ((S)-BINOL), AlMe3, and 2-propanol was established through 1H and 27Al NMRspectroscopies, and APCIMS. All experimental evidence points toward the formation of a BINOL-chelated,pentacoordinate aluminum species in solution. Ligand-accelerated catalysis was confirmed for thephenolate/AlMe3/2-propanol system. The rate law for the catalytic reaction was determined to be nearlyunimolecular dependent on aluminum, zero-order dependent on substrate, and inversely dependent on2-propanol. At the low catalyst loading employed in the BINOL/AlMe3 system, the inherent reversibilityof the MSPV reaction does not affect product yield or enantiomeric excess over time. Systematic ligandstudies imply that while a tetrahedral geometry around the aluminum center may result in the most activeMSPV reduction catalysts, the enantioselectivity of the reaction is enhanced when the aluminum centerallows for a 2-point coordination of the substrate to achieve a pentacoordinate geometry with the fifthligand weakly coordinated to the axial site of a pseudo square pyramid.
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