Thesis advisor: Amir H. Hoveyda / General and efficient methods for catalytic enantioselective synthesis of tertiary alcohols prepared by the addition of C-Metal nucleophiles to ketones. / Thesis (MS) — Boston College, 2008. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

H.R. Johnson [and] M.W.P. Strandberg. / "March 14, 1951." / Bibliography: p. 20. / Army Signal Corps Contract No. DA36-039 sc-100 Project No. 8-102B-0 Dept. of the Army Project No. 3-99-10-022

Thesis (Ph. D.)--University of Chicago, Department of Chemistry, 2002. / Includes bibliographical references. Also available on the Internet.

The investigation presented here is in two parts: a mechanistic study of the triethylamine dehydrohalogenation of ac-haloacid halides to form halogenated ketenes and a study of steric influence upon ketene lifetimes. The first part of this research deals with the mechanism of the dehydrohalogenation reaction. Two acid halides, isobutyryl chloride and a-chloropropionyl chloride, appeared to represent two mechanistic extremes for this reaction with triethylamine. Isobutyryl chloride reacted with triethylamine to form an acylammonium salt while a-chloropropionyl chloride produced the enolate salt. These salts were detected in chloroform solution by both nuclear magnetic resonance spectra and infrared spectra. The results of the investigation into the mechanism of dehydrohalogenation and ketene lifetime were complemented by CNDO/2 calculations of the acid halides and ketenes studied. It was concluded that the mechanism of dehydrohalogenation of acid halides involves a complex series of equilibria,and it has become increasingly apparent that halogenated ketenes are produced through the acylammonium salt. The enolate salt appears to be a dead end in the reaction to form ketenes. It was also demonstrated that increasing steric bulk has a stabilizing effect on ketene lifetimes.

The objective of this study was to develop new synthetical routes to natural and industrial products utilizing ketene cycioaddition reactions. The cycioaddition of diphenylketene with α,β-unsaturated imines yields (2+2) cycioaddition products, g-lactams. However, electron donating groups, such as dimethylamine, in the 4-position of the α,β-unsaturated imines result in (4+2) cycloaddition products, ∂-lactams. Dichloroketene reacted with α,β-unsaturated imines to yield (4+2) cycloaddition products, g-lactams. Large substituents in the 4-position of a, ^-unsaturated imines resulted in a (2+2) cycioaddition product, β-lactam. The ∂-lactams derived from dichloroketene are easily dehydrochlorinated to the corresponding 2-pyridornes.

No description available.

L’objectif de cette étude est de synthétiser de nouveaux polymères aux propriétés spécifiques, en utilisant pour la première fois comme monomère un aldocétène : l’éthylcétène. La synthèse de l’éthylcétène a été entreprise en utilisant deux procédés distincts :d’une part la méthode de McCarney, qui a permis de le préparer dans un solvant par entraînement à la vapeur, et d’autre part le craquage de l’anhydride butyrique à 575°C sous 40mbar.La polymérisation ionique de l’éthylcétène a ensuite été réalisée, dans différentes conditions de solvant, de température et avec plusieurs amorceurs. La polymérisation anionique a abouti uniquement à la formation d’un polyester amorphe, tandis que la polymérisation cationique a conduit exclusivement à un polymère de structure polycétone,d’une grande stéréorégularité avec une cristallinité moyenne de 0,34. Une caractérisation fine de ces polymères a été effectuée par IRTF-ATR, RMN, TGA, DSC, GPC et diffraction desRX. / The aim of this study is to synthesize new polymers with specific properties, using for the first time an aldoketene as monomer, namely ethylketene.The synthesis of ethylketene was carried out by using two distinct processes: on the one hand the method of McCarney, which led to its synthesis in a solvent by co-distillation, and on the other hand the pyrolysis of butyric anhydride at 575°C under 40 mbar.The ionic polymerization of ethylketene was then carried out, using different solvents, temperatures and initiators. The anionic polymerization gave only amorphous polyesters,while the cationic polymerization led exclusively to a polyketonic polymer, highly stereoregular with an average cristallinity of 0.34. A precise characterization of thesepolymers was undertaken by FTIR-ATR, NMR, TGA, DSC, GPC and X-ray diffraction.

A new synthetic route to natural and novel pyrethroid acids was developed utilizing ketene cycloaddition which is a significant improvement over existing syntheses. The newly synthesized pyrethroid acids were converted to pyrethroid esters and used to study structure-activity relationships. The cycloaddition of dichloroketene with 2,5-dimethyl-2,4-hexadiene yields (2+2) cycloaddition products, 2,2-dichlorocyclobutanones. The reductive removal of one chlorine atom from these cycloaddition products gave monochlorocyclobutanones which underwent a Favorskii-type ring contraction to yield cis- and trans-chrysanthemic acids. 4-Methyl-1,3-pentadiene was also used as a precursor in this synthetic scheme to yield an analogue of the chrysanthemic acid. These results are consistent with a concerted cycloaddition process involving a dipolar transition state. The zinc reduction is not a regiospecific reaction which accounts for the two regioisomers of the monochlorocyclobutanones. The Favorskii-type ring contraction is a regiospecific reaction. A variety of different bicyclo(3.1.0)alkenecarboxylates and bicyclo(4.1.0)heptenecarboxylates were synthesized from alkylcyclopentadiene and fulvene derivatives. These new bicyclo pyrethroid acids are structurally similar to the natural chrysanthemic acid but are rigid and locked in a single conformation which is likely the least stable conformer of the natural acid. The acids were converted to pyrethroid esters and tested against the housefly and cockroach. The test results indicate that the bicyclo pyrethroids synthesized are not as active as the natural pyrethroid. Apparently, these bicyclo pyrethroids with structures similar to the less stable conformer of the natural pyrethroids are of little consequence as it binds to the target site in the insect. In an effort to learn more about the conformational requirements of the pyrethroid acid, a new bicyclo-spiro pyrethroid system with a structure similar to the most stable conformation of the natural pyrethroid was designed and synthesized. These bicyclo-spiro pyrethroids were derived from a new isopropylidenecyclobutane derivatives as a starting compound instead of a conjugated diene. The test results of these bicyclo-spiro pyrethroid esters revealed a much greater activity against the housefly and cockroach. This study establishes that the more stable conformer of the natural pyrethroid acid provides a much higher toxicity against the insects tested.

Thesis (Ph.D.)--Mississippi State University. Department of Chemistry. / Title from title screen. Includes bibliographical references.

L’objectif de cette étude est de synthétiser de nouvelles architectures de polycétones aliphatiques à base de cétènes, possédant une température de fusion plus basse que le polydiméthylcétène, tout en conservant une température de dégradation élevée, afin d’élargir sa fenêtre de mise en œuvre.La synthèse du diméthylcétène et / ou de l’éthylcétène a été réalisée par pyrolyse de l’anhydride isobutyrique et/ou butyrique à 625°C sous 40 mbar. Un copolymère statistique a été d’abord synthétisé par copolymérisation entre le diméthylcétène et l’éthylcétène, par voie cationique à -78°C ; ensuite en utilisant un amorceur de Friedel-Craft, un polydiméthylcétène possédant une architecture étoilée a été obtenu. Ces deux polymères ont permis d’atteindre l’objectif initialement fixé : ils présentent un endotherme de fusion à environ 180°C, une bonne stabilité thermique similaire à celle du polydiméthylcétène (Tdégradation = 300°C), et en particulier, de très bonnes propriétés barrières à l’oxygène en milieu humide (jusqu’à 95% HR). / The objective of this study is to synthesize new architectures of ketene-based aliphaticpolyketones, having a lower melting temperature than polydimethylketene, while maintaining a high degradation temperature, in order to widen the processing window. The synthesis of dimethylketene and / or ethylketene was succeeded by the pyrolysis of isobutyric and / or butyric anhydride at 625°C under 40 mbar. A random copolymer was first synthesized by the cationic copolymerization between dimethylketene and ethylketene, at -78 ° C; then using a Friedel-Craft initiator, a star-shaped polydimethylketene was obtained. These two polymers have reached the initial goal of this study: they possess a melting endotherm at about 180°C, a good thermal stability similar to polydimethylketene (Tdegradation = 300°C), and in particular, excellent oxygen barrier properties in wet atmosphere (up to 95% RH).