No description available.

The ring-opening polymerization of octamethylcyclotetrasiloxane, D₄ , in the presence of bis(α,ω-aminopropyl)-1,3-tetramethyldisiloxane using potassium siloxanolate and tetramethylammonium siloxanolate catalysts has been investigated. The use of reversed-phase high performance liquid chromatography (HPLC) and capillary gas chromatography (GC) allowed the disappearance of the starting materials to be monitored as a function of reaction temperature, time, targeted molecular weight, catalyst type and concentration. Due to electronegativity differences, the cyclic tetramer was found to react more quickly than the disiloxane under all conditions studied. This work was extended to the study of polydimethyl-co-diphenylsiloxane oligomers, prepared by the ring-opening copolymerization of D₄ with octaphenylcyclotetrasiloxane, D₄". Reversed-phase HPLC was used to study the disappearance of the cyclic starting materials. Due to volatility considerations these oligomers were not analyzed by capillary GC. ²⁹Si NMR was used to determine the number-average sequence length of each type of siloxane unit as a function of reaction conditions. The co-oligomer composition played the greatest role in determining the average sequence lengths. Oligomers with close to a 50/50 molar composition of dimethyl and diphenyl units showed a tendency towards an alternating distribution, while oligomers with an ≃27/83 molar composition displayed a tendency towards blockiness. A series of polyester-siloxanes was prepared using both bulk and solution polycondensation techniques. Copolymers based on polybutylene terephthalate were highly insoluble, due to the presence of crystallinity in the systems. The incorporation of some isophthalate linkages increased the solubility of the polymer products, making the solution polymerization technique possible. / Ph. D.

The previously unreported 3-methyltetrahydrothiophene I-oxide (<u>1</u>) and 3-methyl-2, 5-dihydrothiophene I-oxide (<u>2</u>) have been prepared by oxidation of the corresponding sulfides. The structure of these unsymmetric sulfoxides was established by chemical and physical methods. Nuclear magnetic resonance analyses have provided significant information concerning some stereochemical aspects of these molecules. In the case of <u>1</u>. which has four possible configurations, both <u>cis</u> and <u>trans</u> isomers were shown to exist in the synthetic material. A study on the temperature dependence of the nuclear magnetic resonance spectrum of <u>2</u> between -34° and 100°, suggested little or no association of a dimeric nature between molecules of this unsaturated sulfoxide. The rapid and clean reduction of <u>2</u> to the corresponding sulfide was carried out using hydriodic acid and detected by gas chromatographic analysis. The partial base catalyzed isomerization of <u>2</u> to 3-methyl-4, 5- dihydrothiophene 1-oxide (<u>13</u>) was carried out in sodium hydroxide solution and detected by gas chromatographic analysis of the reduced products. Maximum isomerization occurred after 96 hours when <u>2</u> and <u>13</u> were present in a ratio of 1.78:1 respectively. This finding is similar to the previously observed isomerization of the corresponding sulfone, but is in contrast to the lack of isomerization of the olefinic bond of the related 2, 5-dihydrothiophene l-oxide. A plausible mechanism has been proposed for this interesting isomerization of <u>2</u>. Sulfoxide <u>1</u> was reacted with various Grignard reagents and shown to undergo a substitution reaction at the α-carbon atoms. Predominant reaction occurred at position-5 of <u>1</u> and binary sulfide mixtures composed of 2-substituted-4-methyl- and 2-substituted-3-methyltetrahydrothiophenes were obtained in yields ranging from 17-31%. The ratio of isomeric sulfides ranged from 1.50:1, in the case of phenylmagnesium bromide, to 8.09:1 when using neopentylmagnesium chloride. The binary sulfide mixtures were desulfurized and the hydrocarbon products were identified. In this manner, the structure and composition of the components of the sulfide mixtures was established. Preparative-scale gas chromatography was used to separate two binary sulfide mixtures. Desulfurization of the individual sulfides led to the discovery of isomerization reactions which occurred during desulfurization. By-products of the Grignard reaction were identified as 3-methyltetrahydrothiophene, 3-methyl-2, 3- and 3-methyl-4, 5-dihydrothiophene, and, in some cases the alkene and alcohol derived from the Grignard reagent. A reaction pathway, by which these products and by-products may conceivably be formed has been proposed. Results of the reaction of the unsaturated sulfoxide <u>2</u> with Grignard reagents were quite different than with sulfoxide <u>1</u>. Sulfoxide <u>2</u> underwent reaction at the sulfur atom with a subsequent cleavage of the ring yielding single dienyl sulfides. These novel compounds were formed by a stereospecific ring cleavage of <u>2</u>, a reaction similar to that previously observed with the corresponding sulfone. The dienyl sulfides, 1-phenylthio- and 1-n-propylthio-2-methyl-1, 3-butadiene, were isolated in good yield and characterized by their spectral properties and by conversion to known compounds. The only detectable by-product of this reaction was a trace amount of 3-methyltetrahydrothiophene. A mechanism, consistant with the data obtained, has been suggested. / Ph. D.

Ph. D.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

A novel cryptand was synthesized which contained a 3,5-disubstituted-4- oxahexacyclo[5.4.1.02,6.03,10.05,9.08,11] dodecane "cage" moiety. In alkali metal picrate extraction experiments the cryptand exhibited high avidity towards Rb+ and Cs+, when compared with the corresponding model compound. A computational study of a series of cage-functionalized cryptands and their alkali metal-complexes was performed. The X-ray crystal structure of a K+-complexed bis-cage-annulated 20-crown-6 was obtained. The associated picrate anion was found to be intimately involved in stabilization of the host-guest complex. The interaction energy between the host-guest complex and picrate anion has been calculated, and the energy thereby obtained has been corrected for basis set superposition error.

Esta tese consiste do estudo de reações de ciclofuncionalização de compostos &#946;-enamino carbonílicos e &#946;-dicarbonílicos, contendo uma cadeia alquenílica nas posições &#945; ou &#947;. Os eletrófilos empregados para este fim foram: iodo, brometo de fenilselenenila e tricloreto de p-metóxifeniltelurio. Os iodo-&#946;-enamino ésteres e cetonas cíclicas, após desidroiodação mediada por base, levaram à formação dos correspondentes pirróis, indóis e aminobenzofuranos. A ciclização dos &#946;-ceto ésteres e &#946;-dicetonas levou a enol éteres e benzofuranos funcionalizados. Estes resultados, juntamente com outros obtidos em nosso grupo de pesquisa, foram utilizados em um estudo comparativo entre reagentes de iodo, selênio e telúrio frente a reações de ciclização eletrofílica de substratos &#946;-dicarbonílicos. / This thesis presents a study of the cyclofunctionalization of &#946;-enamino carbonyl and &#946;-dicarbonyl compounds, substituted by an alkenyl group at the &#945; or &#947; positions. Iodine, phenyl-selenenyl bromide and p-methoxyphenyltellurium trichloride were employed as the electrophilic reagent. The cyclic iodo-&#946;-enamino esters and ketones, after base-promoted dehydroiodination, led to the corresponding pyrroles, indoles and aminobenzofurans. The cyclization of the &#946;-keto esters and &#946;-diketones afforded five- and six-membered enol ethers and benzofuranones. These results, together with others previously obtained in our research group, allowed us to compare the behavior of the three above mentioned electrophiles toward the cyclofunctionalization of &#946;-dicarbonyl substrates.

Uma série de &#946;-enamino ésteres foi submetida a reações de iodociclização ou lactonização mediada por iodo, fornecendo como produtos iodo-&#946;-enamino ésteres cíclicos ou &#946;-enamino lactonas, respectivamente. Os iodo-&#946;-enamino ésteres cíclicos obtidos foram submetidos a reações de desidroiodação, fornecendo os correspondentes produtos de eliminação de HI a partir de iodociclos de cinco membros, e ciclopentanos trissubstituídos, a partir de anéis de seis membros. Esta última reação ocorreu por substituição nucleofílica intramolecular, em vez da esperada reação de desidroiodação. O efeito do N-substituinte, nestas reações, foi estudado para uma série de N-alquil e N-aril derivados, fornecendo dados que possibilitaram uma melhor compreensão dos mecanismos envolvidos. As &#946;-enamino lactonas foram obtidas em baixos rendimentos, devido à formação de subprodutos decorrentes da poliiodação do substrato, e mostraram-se resistentes à redução da dupla ligação carbono-carbono por uma série de métodos testados. Um estudo de análise conformacional dos compostos bicíclicos nitrogenados também foi efetuado, através de dados espectroscópicos de RMN-1H e RMN-13C, com o auxílio de cálculos de mecânica molecular e semi-empíricos. Concluiu-se que em função do N-substituinte os biciclos adotam diferentes conformações preferenciais, o que altera significativamente seus perfis espectroscópicos. / A series of acyclic &#946;-enamino esters was submitted to iodocyclization reactions or to iodine-mediated lactonization, leading to the corresponding cyclic iodo-&#946;-enamino esters or &#946;-enamino lactones. Dehydroiodination of the five-membered ring enamino esters furnished pyrrole, tetrahydroindole and hexahydroindole derivatives, under basic or neutral conditions. The six-membered ring enamino esters, when submitled to treatment with triethylamine, gave rise to trisubstituted cyclopentanes. This transformation occurred through an intramolecular nucleophilic substitution, instead of the expected dehydroiodination reaction. The effect of the N-substituent in these reactions was studied for a series for N-alkyl and N-aryl derivatives. The &#946;-enamino lactones were obtained in poor yields, due to the poliiodination of the substrates, and showed to be resistent to reduction of the carbon-carbon double bond under several conditions. A study of conformational analysis of the bicyclic &#946;-enamino esters was undertaken, using 1H-NMR and13C-NMR data, molecular mechanics and semi-empirical methods. From this study, it was observed that the bicyclic compounds adopt different conformations depending upon the N-substituent.

Abstract not available

A new method for running the Knoevenagel condensation in high yields has been developed and tested in eleven reactions with malononitrile. The dimer from cyclopentylidenemalononitrile was characterized and its structure was deduced from spectroscopy data. Reactions of the monomers with isoprene were carried out in sealed tubes and the ratio and yields of the isomeric products were determined by gas liquid partition chromatography. A para relationship of the cyano and methyl groups is favored in the products.Ball State UniversityMuncie, IN 47306