Lui, Nathan Mancheun2024-04-052024-04-052023-08Lui_cornellgrad_0058F_13793http://dissertations.umi.com/cornellgrad:13793https://hdl.handle.net/1813/114693913 pagesCamphorsultam-based enolates, referred to colloquially as Oppolzer enolates, are examined spectroscopically, crystallographically, kinetically, and computationally to ascertain the mechanism of alkylation and the origin of stereoselectivity. Solvent- and substrate-dependent structures of lithium Oppolzer enolates include tetramers for alkyl-substituted enolates in toluene, spirocyclic dimers for aryl-substituted enolates in toluene, substrate-independent symmetric dimers in tetrahydrofuran (THF) and THF/toluene mixtures, hexamethylphosphoramide-bridged (HMPA) trisolvated dimers at low HMPA concentrations, and disolvated monomers for the aryl-substituted enolates at elevated HMPA concentrations. Their sodium counterparts, however, reside as monomers in neat THF and THF/HMPA solutions and as dimers in toluene when solvated by N,N,N’N’-tetramethylethylenediamine (TMEDA) and N,N,N’,N’’N’’-pentamethyldiethylenediamine (PMDTA). Aided by density functional theory (DFT) extensive analyses of the stereochemistry of aggregation and solvation are included. Rate studies of allylation implicate analogous transition structures, namely an HMPA-solvated ion pair with a +Li(HMPA)4 or +Na(HMPA)5 counterion. Curious dependencies on toluene and THF are attributed to exclusively secondary-shell (medium) effects. Sparse reports detailing an analogous HMPA–free methylation are also explored, revealing a similar reaction pathway (via the THF-solvated E–//+Na(THF)6 ion pair). Aided by DFT calculations, a stereochemical model is presented in which the alkylating agent is guided to the exo–face of the camphor owing to stereoelectronic preferences imparted by the sultam sulfonyl moiety, rather than chelate directed endo–facial approach. Consequently, counter to decades of reasoning, the origins of stereoselectivity stem not from steric effects enforced by the chelation of the metal cation, but rather from chirality within the sultam ring imparted by the rigidity of the camphor skeletal core.enAttribution-NoDerivatives 4.0 InternationalCamphorsultamDFT calculationsEnolatesKineticsMechanismOrganic chemistrydissertation or thesishttps://doi.org/10.7298/2pn4-cq46