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La Montmorillonite-sodium est une argile gonflante de la famille des Smectites qui presente la propriete de pouvoir echanger les cations sodium, situes dans ses espaces interlamellaires. Grace a cette propriete, nous avons pu concevoir des argiles organiques, par association entre de la Montmorillonite-sodium avec des cations organiques derives d'acides amines et fonctionnalises par esterification. Ces nouveaux materiaux ont ete caracterises par determination des isothermes d'adsorption et de desorption des cations organiques et sodium, respectivement, ainsi que par mesure des espaces interlamellaires des argiles organiques par diffraction de rayons. X. Parmi les applications possibles de ces nouveaux materiaux, on peut citer la resolution de melanges de gaz par chromatographie en phase gazeuse. Une etude menee sur la separation de melanges CO$\sb2$, CH$\sb4$, O$\sb2$, N$\sb2$, en utilisant differents supports, a ete interpretee en termes de taille et forme de cavites creees au niveau de l'argile, comparees aux molecules de gaz. Autre application, la resolution de melanges racemiques d'acides amines a ete investiguee en chromatographie en phase liquide.

General Organization. This thesis contains a brief introduction to the area of $\beta$-lactam antibiotics and four other Chapters dealing with the syntheses of various 6-methoxy $\beta$-lactams. Due to the tremendous level of activity in this area the introductory literature material is presented in an illustrative approach rather than a comprehensive approach. Literature surveys were carried out using Chemical Abstracts from 1982 to February 1992. Experimental details are given at the end of each Chapter. Compounds in the schemes which did not lead to desired conclusion were not completely characterized; $\sp1$H NMR and other spectral data whenever available are given in the Experimental section. IR was not recorded in most of these cases. Elemental analyses were not performed at all, since the data from such experiments do not always represent the purity of product. Chapter 1. This section describes the development of various $\beta$-lactam antibiotics, major representative structures, mode of action and overall objectives of the research undertaken. Chapter 2. 7-Methoxy-7-ethyl and 7-methoxy-7-hydroxyethylisocephem analogs were prepared from 4-cinnamyl-3-methoxyazetidinone which was prepared in a multigram scale. This precursor can be purified simply by trituration with ether. The transformation of this monocyclic starting material to the cyclization precursor involved introduction of an additional side-chain at C-3 via. generation of anion using lithium diisopropylamide and quenching of the anion with either ethyl iodide or acetaldehyde. In the case of the hydroxyethyl side-chain oxidation with pyridinium chlorochromate, reduction with L-Selectride and silylation with tert-butyldimethylsilyl triflate was required before carrying out further manipulations. The cinnamyl group was converted to a methylene bearing a leaving group and the p-methoxyphenyl moiety on nitrogen was cleaved and a suitable acetate side-chain was introduced. The anionic annulation with CS$\sb2$ gave the desired bicyclic compounds. An optically active isocephem having a thienamycin type side-chain at C-7 and and a racemic isocephem having a methoxy group at C-7 were prepared by similar method. Chapter 3. 7-Ethyl-7-methoxycarbacephem was prepared using a rhodium carbenoid reaction starting from 4-cinnamyl-3-methoxyazetidinone. A similar method was applied to prepare an advanced intermediate for 7-hydroxyethyl-7-methoxycarbacephem. Chapter 4. 6-Methoxy-PS 5 synthesis was attempted which was found to be unstable. The cyclization was carried out applying the rhodium carbenoid methodology. The cyclization precursor was obtained using nitroaldol condensation starting from an aldehyde which was prepared from 4-cinnamyl-3-methoxyazetidinone. Chapter 5. Syntheses of 6-methoxy-1-methyl-PS 5 analogs were attempted starting from 3-ethyl-3-methoxy-4-methylcinnamylazetidinone. The introduction of 1-methyl group involved the reduction of a suitable $\alpha,\beta$-unsaturated ester obtained via. palladium catalyzed carbonylation reaction.

Part A. Several optically active thiolanes were synthesized and converted into sulfonium salts. These were subsequently transformed into the corresponding sulfur ylides which in turn reacted with carbonyl compounds to produce optically active epoxides. trans-2,3-Diaryloxiranes have been obtained in up to 83% enantiomeric excess via the reaction of S-benzyl ylides prepared from optically active trans-2,5-disubstituted thiolanes. The complete stereofacial transfer of a benzylidene group to a substituted benzaldehyde was successfully accomplished using S-benzyl ylide derived from (1R,2S,3R,5S)-2,3-dibenzyl-1,8,8-trimethyl-3-thianiumbicyclo (3.2.1) octane perchlorate 123 (prepared from 1R,3S-(+)-camphoric acid). trans-Stilbene oxides were produced with ee's approaching enantiomeric purity. These results represent the first example of the preparation of epoxides in nearly enantiomerically pure form by a sequence which involves both a carbon-carbon and a carbon-oxygen bond rather than only carbon-oxygen bond formation. A rationale for the high chiral induction in the latter case based on the control of facial selectivity at the ylide will be discussed. The facial selectivity at the carbonyl is believed to play a minor role. The design of potentially more efficient chiral sulfide auxiliaries and their use in the synthesis of epoxide is also presented. Part B. Erythro- and threo-1,2-diphenyl-2-butylsulfinylethanol 154 and 158 were prepared from the condensation of the $\alpha$-lithio derivative of benzyl-t-butyl sulfoxide with benzaldehyde. The reaction of the erythro-isomer with sulfuryl chloride gave an unknown substance whose structure was established by X-ray difractometry as (2R$\sp*$, 3S$\sp*$, 4R$\sp*$, 6R$\sp*$)-3,4-diphenyl-6-(diphenylmethyl)-1,5-dioxa-2-thiane-2-oxide 156, the first representative of a new heterocyclic ring system. Similar treatment of the threo-isomer 158 resulted in the formation of 157, a stereoisomer of 156.

N-alkylated anilines can be obtained in moderate yields from aniline and methyl formate in the presence of Rh$\sb6$(CO)$\sb $ and KI after 72 hours at 180-200$\sp\circ$C. Ru$\sb3$(CO)$\sb $ gave similar results to the unpromoted rhodium carbonyl system. Formanilide and N-methylformanilide were also formed in the reaction. The (HCr(CO)$\sb5$) -anion in the form of its PPN$\sp+$ and Et$\sb4$N$\sp+$ salts also catalysed this reaction (under hydrogen) but was selective to the formanilide products. The presence of an electron donating group on the aromatic ring favoured the formation of alkylated products in the presence of bis(triphenylphosphine)iminium (PPN$\sp+$) hydridochromiumpenta-carbonyl. Several possible mechanisms were tested and the nature of the polynuclear catalysts investigated.

The fragmentation mechanism of ionized neopentanol, (CH$\sb3$)$\sb3$CCH$\sb2$OH$\sp{+-}$, has been studied in great detail along with other C$\sb5$H$\sb $H$\sp{+-}$ isomers. The use of $\sp $C and D labelling was found an essential tool to establish the relation between the other species involved in the dissociation of neopentanol. The involvement of (CH$\sb3$)$\sb2$C$\sp{\cdot}$CH$\sb2\sp+$(O)HCH$\sb3$, (CH$\sb3$)$\sb3$C$\sp+$(O)HCH$\sb2$ and (CH$\sb3$)$\sb2$($\sp\cdot$CH$\sb2$)CCH$\sb2\sp+$OH$\sb2$ was essential to explain the H/D label exchange occurring upon fragmentation of neopentyl alcohol. An ion-dipole complex between methanol and ionized methyl propene is proposed as the final intermediate which leads directly to the products, methanol and ionized methyl propene. The results of the investigation of C$\sb7$H$\sb5\sp+$ ions from various precursor molecules are also described. The following compounds, which all produce C$\sb7$H$\sb5\sp+$ ions, were studied: benzyl acetate, benzyl formate, benzyl alcohol, 2-bromocyclopropabenzene, 1,6-heptadiyne and 1,5-decadiyne. According to the metastable ion (MI) mass spectra and the He collision induced dissociation (CID) of m/z 89 ions, it is suggested that four structures exist. (Abstract shortened by UMI.)

(1.1.1) Propopellane, I, is the ultimate propellane in terms of its small size and the inversion of the tetrahedral geometry about its bridgehead carbons. As such I is reactive towards radicals and carbenes. We have studied the kinetics and mechanisms of reaction of various carbon and heteroatom centered free radicals with I by nanosecond flash photolysis and product studies techniques.(DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI) The addition of diphenylcarbene (DPC) and phenylchlorocarbene (PCC) to I have also been investigated. Addition of DPC proceeds via a 1,4-biradical intermediate, II, whereas with PCC it appears that the final product, III, is formed directly upon reaction. The implications of the apparent concerted addition of the singlet carbene to I are discussed.(DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI) The role of I as a quencher of electronic excited states is also reported.

The silanol distributions on "as received" aerosil and precipitated silica have been studied (1) by using time-resolved infrared spectroscopy in order to follow a reaction with AlMe$\sb3$, TiCl$\sb4$, or BCl$\sb3$, (2) by spectroscopically comparing the accessibility of probe molecules having different steric dimensions, that react with surface silanols (SiOH) either by chemisorption or H/D exchange, and (3) by gravimetrically measuring surface silanol densities using vacuum microbalance techniques. The results have been used to compare and characterize these non-porous silicas of similar surface area. Initially, H-bonded silanols are relatively more reactive than isolated silanols in the order of reagents, BCl$\sb3$ $>$ TiCl$\sb4$ $>$ AlMe$\sb3$. In the fully hydroxylated "as received" state, the number of silanol groups on either silica which react with various hydrogen sequestering (HS) agents decreases as the size of the agent increases (ZnMe$\sb2$, BCl$\sb3$, TiCl$\sb4$, AlMe$\sb3$ and Me$\sb3$SiNHSiMe$\sb3$ (HMDS) in increasing size). The number of silanols that undergo H/D exchange also decreases as the size of the probe molecule increases (D$\sb2$O, ND$\sb3$, and deuterated methanol, i-propanol and t-butanol). The reaction between HMDS and H-bonded silanols occurs preferentially with the terminal silanols of a chain, and we propose that these silanols occupy sites which are inherently more accessible to this bulky reactant. By following the evolution of the SiOH bands on both silicas in all three spectral regions for 450, 600, and 800$\sp\circ$C activation, we have assigned bands to two types of isolated silanols. The type I silanols are preferentially eliminated between 450 and 800$\sp\circ$C activation and are more abundant on precipitated silica than on aerosil. Type II silanols (isolated single silanols) dominate the surface of highly activated aerosil or precipitated silica. The vibrational spectra are reported for the physically adsorbed complexes, SiOH...X (X = CO, N$\sb2$, and CH$\sb4$) and the nature of their specific interaction with surface SiOH is discussed. Mechanisms are proposed for the room-temperature reaction between SiOH and TMP to produce DMP, and the SiOH catalyzed isomerization of TMP to DMMP. (Abstract shortened by UMI.)