Hemilabile ligands in organolithium chemistry: Substituent effects on lithium ion chelation

ORGN 31

Antonio Ramirez and David B. Collum. Department of Chemistry and Chemical Biology, Cornell University, Baker Laboratory, Ithaca, NY 14853
The lithium diisopropylamide-mediated elimination of 1-bromocyclooctene to provide cyclooctyne is investigated using approximately 50 potentially hemilabile polyethers and amino ethers. Rate laws for selected ligands reveal the chelated monomer-based pathways. The dependence of the rates on the substitution patterns shows that anticipated rate accelerations based on the gem-dimethyl effect are nonexistent and that substituents generally retard the reaction. With the aid of computational studies, the factors influencing chelation are discussed.

 

Physical Organic Chemistry: Calculations, Mechanisms, Photochemistry and High Energy Species
8:00 AM-12:00 PM, Sunday, September 7, 2003 Sheraton New York -- Royal Ballroom A, Oral

Division of Organic Chemistry
The 226th ACS National Meeting, New York, NY, September 7-11, 2003