Friday, 6 October 2006 - 1:45 PM
Binghamton Ballroom (Holiday Inn Binghamton - Arena)
282

Determination of lithium enolate solution structures via 6Li NMR spectroscopy

Lara R. Liou, Anne J. McNeil, Antonio Ramirez, and David B. Collum. Cornell University, Ithaca, NY

Despite the utility of lithium enolates in synthesis, their solution structures and, consequently, their affiliated reaction mechanisms remain ill defined. NMR spectroscopy has offered little insight into enolate structure because the Li-O linkages are spectroscopically opaque and the common structural forms are highly symmetric, until now. We report the application of Job's Method of Continuous Variations via 6Li NMR spectroscopy to a variety of enolates to assign their aggregation state in solution. The inherent symmetry of the enolate aggregate is disrupted by using pairs of enolates to generate an ensemble of homo- and heteroaggregates. Development of the technique has allowed for solution structure determination for a number of enolates which is the first step in elucidating the mechanisms of reactions involving lithium enolate intermediates.


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