Thesis (doctoral)--Ludwig-Maximilians-Universität, 1983.

Yes / Fused cyclobutanes are found in a range of natural products and formation of these motifs in a straightforward and easy manner represents an interesting synthetic challenge. To this end we investigated an intramolecular variant of the thermal enamine [2 + 2] cyclisation, developing a diastereoselective intramolecular enamine [2 + 2] cyclisation furnishing δ lactone and lactam fused cyclobutenes in good yield and excellent diastereoselectivity. / The work was funded by Yorkshire Cancer Research

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Universiẗat-Gesamthochsch., Diss.--Paderborn, 1996.

Design and development of novel one-step reactions that produce nitrogen-containing scaffolds is an invaluable area of chemistry due to the abundance of these moieties in natural products and biologically active molecules. Discovering novel methods using uncommon substrates and rare earth metals to access these significant scaffolds present a challenge. Over the course of my doctoral studies, I have designed, developed and optimized novel reactions by using rarely known substrates and rare earth metals that have afforded important nitrogen-containing scaffolds. The products obtained allow access to otherwise long-to-synthesize molecules and expeditious construction of biologically active molecules.

No description available.

Nesta tese foi empregada a iodociclofuncionalização de β-enamino ésteres para obtenção de análogos conformacionalmente restritos do ácido γ-aminobutírico (GABA) e de 4-aril-1,4-di-hidropiridinas (DHP\'s). Foram preparados ciclopentanos trissubstituídos a partir de b-enamino ésteres cíclicos, com o objetivo de investigar o mecanismo desta reação. Utilizando ESI(+)-MS/MS, foi possível identificar e caracterizar os intermediários bicíclicos catiônicos, confirmando que a reação se processa através de uma SN2 intramolecular. A biorredução do grupo acetila existente nos ciclopentanos, utilizando raízes de Daucus carota e células íntegras de Aspergillus terreus CCT 3320 e Rhizopus oryzae CCT 4964, forneceu novos análogos oticamente ativos do GABA, com excelente enantiosseletividade. Também foram preparados iodo-β-enamino ésteres cíclicos de seis membros, contendo um grupo arila na posição 4 do anel tetra-hidropiridínico, cuja desidroiodação forneceu os respectivos derivados 1,4-di-hidropiridínicos. / This thesis presents a study of iodo-cyclization of β-enamino esters in order to obtain conformationally restricted analogues of γ-amino butiric acid (GABA) and of 1,4-dihydropyridines (DHP\'s). Trisubstituted cyclopentanes were obtained from iodo-β-enamino esters and the mechanism of their formation was proposed and corroborated by (+)-ESI-MS/MS through the interception and structural characterization of the key bicyclic iminium ion intermediates. Optically active GABA analogues have been prepared in high enantiomeric excesses (up to >99%) by bioreduction of the keto group in cyclopentane derivatives using whole fungal cells of Aspergillus terreus CCT 3320, Rhizopus oryzae CCT 4964 and Daucus carota root. 4-aryl-1,4,5,6-tetrahydropyridine derivatives were synthesized by iodo-cyclization of a-alkenyl-b-enamino esters and 4-phenyl-1,4-dihydropyridine derivatives were obtained after base-promoted dehydroiodination of the corresponding cyclic iodo-b-enamino esters.

The use of enamines continues to be an important tool in organic syntheses as both a catalyst and reactant. The addition of metal catalysts coupled with enamine catalysis has generated many reactions that normally would not occur separately. However, catalysts' incompatibility is an issue that we wish to solve allowing new chemistry to occur without hindrance. The use of enamines has continued to be a well-studied area of organic chemistry, but the field is ripe for different types of enamines to gain the spotlight. Enaminones are enamines with both nucleophilic and electrophilic properties. They allow reactions that are normally not possible with enamines to become obtainable. Chapter 1 is a brief introduction on enamines and the reason they gained so much attention. Then ends with enaminones and what makes them interesting reactants. Chapter 2 described a new synthesis for the tricyclic synthesis of chromanes using a novel bifunctional catalyst system of enamine-metal Lewis acid giving great yields (up to 87 %yield) and excellent stereoselectivity (up to 99 % ee). Chapter 3 covered new reactions for ring-open cyclopropane (up to 94% yield), tetrahydroquinolinones (up to 84% yield) and enantiospecific tetrahydroquinolinones (up to 84% yield and 97% ee) using α-enaminone and donor-acceptor cyclopropanes. Finally, Chapter 4 focused a new method for synthesizing benzobicyclo[3.2.1]octanes with an added sterically bulky quaternary center and imine functionalization giving yields between 36-73% yield using α-enaminone with alkylidene malonates.

Nesta tese foi empregada a iodociclofuncionalização de β-enamino ésteres para obtenção de análogos conformacionalmente restritos do ácido γ-aminobutírico (GABA) e de 4-aril-1,4-di-hidropiridinas (DHP\'s). Foram preparados ciclopentanos trissubstituídos a partir de b-enamino ésteres cíclicos, com o objetivo de investigar o mecanismo desta reação. Utilizando ESI(+)-MS/MS, foi possível identificar e caracterizar os intermediários bicíclicos catiônicos, confirmando que a reação se processa através de uma SN2 intramolecular. A biorredução do grupo acetila existente nos ciclopentanos, utilizando raízes de Daucus carota e células íntegras de Aspergillus terreus CCT 3320 e Rhizopus oryzae CCT 4964, forneceu novos análogos oticamente ativos do GABA, com excelente enantiosseletividade. Também foram preparados iodo-β-enamino ésteres cíclicos de seis membros, contendo um grupo arila na posição 4 do anel tetra-hidropiridínico, cuja desidroiodação forneceu os respectivos derivados 1,4-di-hidropiridínicos. / This thesis presents a study of iodo-cyclization of β-enamino esters in order to obtain conformationally restricted analogues of γ-amino butiric acid (GABA) and of 1,4-dihydropyridines (DHP\'s). Trisubstituted cyclopentanes were obtained from iodo-β-enamino esters and the mechanism of their formation was proposed and corroborated by (+)-ESI-MS/MS through the interception and structural characterization of the key bicyclic iminium ion intermediates. Optically active GABA analogues have been prepared in high enantiomeric excesses (up to >99%) by bioreduction of the keto group in cyclopentane derivatives using whole fungal cells of Aspergillus terreus CCT 3320, Rhizopus oryzae CCT 4964 and Daucus carota root. 4-aryl-1,4,5,6-tetrahydropyridine derivatives were synthesized by iodo-cyclization of a-alkenyl-b-enamino esters and 4-phenyl-1,4-dihydropyridine derivatives were obtained after base-promoted dehydroiodination of the corresponding cyclic iodo-b-enamino esters.

No description available.