. 67,1523 (1989).1,4-Di-0-methyl-L-threitol and 1,2,5,6-tetra-0-methyl-L-mannitol were prepared by new, more convenient, and higher yielding routes. These and 1 ,2;5,6-di-0-isopropylidene-D-mannitol formed 2:2 complexes with Ti(OiPr),, but did not readily form 1:2 complexes in the presence of excess ~i~+ .'H and I3C nuclear magnetic resonance spectra showed that the structures in solution of the 2:2 complexes were analogous to solid-state structures of tartaric acid derivatives, i.e., possessing bridging diolate oxygens. In contrast, R,R-and meso-diisopropyl tartrates, N,N1-dibenzyl tartramide, and N,N1-di(2-pheny1)ethyl tartramide behaved very differently. The tartramides formed mixtures of complexes that became dominated by 2:3 complexes in the presence of excess T i ( 0 '~r )~. Two tertiary tartramides failed to provide well-defined complexes. The R,R-tartrate formed a monocyclic (nonbridged) 2:2 complex, but an equilibrating mixture of 1:2 and 2:2 complexes with excess ~i~+ .The equilibrium shifted upon cooling toward a 1:2 complex possessing a bridging diolate oxygen, as did the meso 1:2 complex. Other temperature-dependent phenomena were also studied.
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