Titanium tetraisopropoxide methanol reaction

Eastman have patented a range of techniques for recovering monomers from aromatic polyesters. Initial intellectual property dealt with generalised schemes for methanolysis catalysed by zinc acetate, tin salts or titanium tetraisopropoxide [157, 158]. A major effort was made to develop a process which may be described as high-pressure methanolysis, in which superheated methanol is passed through a solution of scrap PET in oligomers of the same material [159-166]. Various refinements have also been made to the basic process, including addition of trace amounts of base to the reaction to prevent formation of dioxin [167], and recovery of additional aliquots of DMT from the EG stream and purification of the latter product [168-171]. 

In 2004, Walsh and coworkers demonstrated that titanium complexes of tra s-l,2-bis(hydroxy-camphorsulfonylamino) cyclohexane were excellent catEilysts for asymmetric ZnPh additions to ketones. The reactions showed excellent enantioselectivities (Scheme 7.49) [79]. The reaction employs the readily available bis(sulfonamide) diol ligand (Scheme 7.49), a sub-stoichiometric amount of titanium tetraisopropoxide, and commercially available diphenylzinc. The reactions were clean, affording high yields of tertiary alcohol in less than 24 h at room temperature. This, in fact, was an improvement over the results reported previously by Dosa and Fu [78]. Additionally, there was no need for methanol as an additive. 

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