Mixed aggregation effects: Mechanistic changes in the course of a LDA-mediated enolization

ORGN 269

Antonio Ramirez, ar70@cornell.edu and David B. Collum. Department of Chemistry and Chemical Biology, Cornell University, Baker Laboratory, Ithaca, NY 14853
During a lithium diisopropylamide (LDA)-mediated enolization a lithium enolate is generated while LDA is consumed. Spectroscopic studies show the formation of (i-Pr2NLi)n/Li-enolate mixed aggregates. The new species inhibit enolization rates and change the reaction mechanism. In conditions that minimize the concentration of mixed aggregates, rate studies demonstrate that the enolizations occur via LDA dimers. In contrast, enolizations effected by i-Pr2NLi/Li-enolate complexes proceed primarily via LDA monomers. The factors influencing mixed aggregation along the reaction coordinate are explored using DFT computations.

 

Metal-Mediated Reactions and Syntheses
1:00 PM-5:00 PM, Monday, 29 August 2005 Washington DC Convention Center -- 202B, Oral

Division of Organic Chemistry

The 230th ACS National Meeting, in Washington, DC, Aug 28-Sept 1, 2005