Selective carbon-carbon bond formation: Catalysis, mechanism, and asymmetric induction

One of the most significant challenges faced by synthetic organic chemists is the selective formation of carbon-carbon bonds. The following work describes the selectivity of carbon-carbon bond formation from three different perspectives. Catalysis and regioselectivity of bond formation is examined through the 3-aza-Cope rearrangement. Ziegler-Natta polymerization models are used as tools for investigation of the activation of transition-metal-carbon bonds toward olefin insertion in the formation of five- and six-membered carbocycles. Lastly, the extent of asymmetric induction in the formation of quaternary carbon centers was determined for the aza-annulation of {dollar}beta{dollar}-enamino esters with acrylate derivatives.; The (3,3) sigmatropic rearrangement of N-alkyl-N-allyl enamines was accelerated through the use of a number of Lewis acids. Organoaluminum reagents provided the most efficient rearrangement, and the yields of the rearranged and reduced {dollar}delta,epsilon{dollar}-unsaturated amines ranged from 59 to 99%. The rearrangement of both phenyl and alkyl substituted N-alkyl-N-allyl enamines occurred exclusively through a (3,3) sigmatropic shift for either protic or Lewis acid catalysis.; Intramolecular olefin insertion in the selective formation of five- and six-membered rings was used as a model for Ziegler-Natta polymerization of {dollar}alpha{dollar}-olefins. Both {dollar}alpha{dollar}- and {dollar}beta{dollar}-deuterium isotope effects were shown for the first time in a titanium system modeling {dollar}alpha{dollar}-olefin polymerization. Promotion of the intramolecular olefin insertions with methylaluminoxane resulted in inverse alpha kinetic isotope effects ({dollar}ksb{lcub}rm H{rcub}{dollar}/{dollar}ksb{lcub}rm D{rcub}{dollar} = 0.88 and 0.95 {dollar}pm{dollar} 0.03) and normal isotope effects for the beta position ({dollar}ksb{lcub}rm H{rcub}{dollar}/{dollar}ksb{lcub}rm D{rcub}{dollar} = 1.06 {dollar}pm{dollar} 0.03). These findings were compared with the MgX{dollar}sb2{dollar} promoted cyclizations which resulted in alpha effects of {dollar}ksb{lcub}rm H{rcub}{dollar}/{dollar}ksb{lcub}rm D{rcub}{dollar} = 1.22 and 1.28 {dollar}pm{dollar} 0.03 and beta effects of {dollar}ksb{lcub}rm H{rcub}{dollar}/{dollar}ksb{lcub}rm D{rcub}{dollar} = 1.09 and 1.10 {dollar}pm{dollar} 0.03. The intramolecular olefin insertion reaction was also utilized to show the existence of chain transfer/ligand transposition processes, and to provide evidence for the intramolecular nature of these processes in titanium systems.; Stereoselective carbon-carbon bond formation was effectively illustrated through the aza-annulation of {dollar}beta{dollar}-keto esters with a variety of acrylate derivatives. Annulated products were obtained in yields ranging from 43 to 87% with 84-96% de, and the effects of solvent, temperature, reaction time and chiral auxiliary were examined.