Asymmetric autocatalysis with organozinc complexes; Elucidation of the reaction pathway

This review describes the development of mechanistic understanding of amplifying asymmetricautocatalysis. After a brief description of kinetics, the main body of the work discusses theapplication of a variety of NMR techniques to the structure of the resting state in solution.The results are consistent with a dominant square Zn-O bonded dimer at ambient temperature.Furthermore, the energies of homo-and heterochiral dimers is comparable; they exchange slowly onthe NMR timescale but fast enough for the lifetime of an individual molecule to be established. Theassociation of alkylzinc with this dimer can be quantified and located, and dynamic alkyl exchangesdefined. DFT calculations have been carried out, which underpin the dimer structure and provide furtherinsight into the steric control of autocatalysis by the bulk of diisopropylzinc. NMR, kinetics andcomputation converge in supporting the role of dimers of the indicated structure, and in pointingto a mechanism whereby the unique reactivity of the homochiral dimer is the driving force, atleast at ambient temperature.