Zugl.: Aachen, Techn. Hochsch., Diss., 2005.

Amides are one of the most common functional groups in biological systems and in bioactive molecules. Arguably the most direct way to form amides is via the condensation of an amine onto a carboxylic acid. This reaction is notoriously difficult and has stimulated much development, including the developments of new reagents and catalysts to perform this transformation under milder conditions. More broadly, amide formation continues to be of high importance and the incorporation of emerging transformations utilizing new disconnections are complimentary to existing routes. Isocyanates are the simplest electrophiles containing the desired NCO motif and have a large presence in the polymer (e.g. polyurethane) and paint industries. In addition, isocyanates have been utilized for amide formation with various nucleophiles in a stoichiometric and catalytic fashion, but the inherent functional group intolerance associated with the high reactivity of isocyanate largely remains. Efforts have been made to address such limitations of isocyanates, including the use of a blocking group which allow for in situ release of the isocyanate while using a bench stable masked (blocked) isocyanate precursor. Changes to the blocking group structure have direct correlations to the stability and reactivity of the precursor, which helps in suppressing common side reactions observed with free isocyanates such as polymerization or oligomerization. Incorporation of a blocking group strategy in catalytic amide forming reactions has the power to unlock the potential of isocyanates with reactivity that would not be attainable with free isocyanates. Reports imparting this strategy exemplify the power of a blocking group with increased applicability and functional group tolerance compared to reactions with the free isocyanate counterpart. The implementation of this strategy for catalytic amide formation is sparse including only two reports with a rhodium catalyst. Utilization of different metals could broaden the scope of reactivity allowing for extensions that the rhodium (I) catalyst cannot do. The development of a palladium-catalyzed amide synthesis via masked isocyanates was targeted (Chapter 2). Indeed, implementation of a blocking group strategy with alkyl and aryl isocyanates allowed for efficient synthesis of amides with electron rich and mildly deficient aryl boroxine nucleophiles. Catalysis was achieved with 1 mol% of Pd(OAc)2 and 2 mol% of SPhos at 50 ℃ with Et3N to aid in the deblocking of the isocyanate. Several control experiments were iii conducted to obtain mechanistic insight including what mechanism may be operative as well as the necessity of this blocking group strategy. Kinetic studies were performed using the variable time normalization analysis method and have yielded the following information: 1) the presence of catalyst decomposition, 2) that the rate determining step involved the catalyst, boroxine, and masked isocyanate, and 3) that the rate determining step is likely the insertion into the isocyanate. In summary, palladium catalysts can achieve catalysis with masked isocyanates to facilitate amide formation under appropriate conditions. With limited reports of masked isocyanates in catalysis, this reactivity could act as a steppingstone for developments of reactivity that are held back with the use of free isocyanates.

La nature regorge de composés chimiques, biologiquement actifs, possédant des propriétés thérapeutiques intéressantes. Parmi ces produits naturels, ceux constitués d'un noyau cyclique azoté sont particulièrement abondants. Les nouvelles méthodologies, permettant un accès rapide et efficace à des composes azotés hautement fonctionnalisés, sont donc de première importance en synthèse organique. Dans ce contexte, nous avons étudié une nouvelle approche reposant sur une séquence de polycyclisation anionique utilisant une fonction cétone comme agent d'activation et un groupement isocyanate en tant qu'agent de terminaison. Afin d'être efficace, cette méthodologie nécessite la résolution de deux importants challenges. Tout d'abord, il est essentiel de trouver les conditions idéales permettant de générer un énolate en présence d'un isocyanate, sans activer la polymérisation et sans addition nucléophile de la base sur l'isocyanate. Ceci nous a conduit à étudier en détail la génération d'énolates dérivés de cétones et leur condensation avec des isocyanates non activés, conduisant à des ¦Â-cétoamides. Deux stratégies, utilisant des éthers d'énols silylés et des cétones avec différents types de bases, ont été évaluées. Alors que les éthers d'énols silylés se sont révélés être des partenaires efficaces, les meilleurs résultats ont été obtenus en utilisant les cétones correspondantes en présence de trityl lithium.Le second challenge implique la synthèse des précurseurs pour la cyclisation anionique. En effet, les composés contenant à la fois les fonctionnalités cétone et isocyanate sont rares. Malgré cela, en utilisant la procédure de Lantzsch (afin d'éviter la O-alkylation), nous avons pu obtenir différents céto-isocyanates qui ont ensuite pu être engagés dans l'étape de cyclisation. Lorsque la 4-isocyanato-4-méthyl-pentan-2-one est traitée par du trityl lithium, la pipéridine fonctionnalisée correspondante est obtenue avec un rendement quantitatif, démontrant ainsi la viabilité de cette approche. Ces résultats nous ont ensuite permis de nous orienter vers la synthèse de substrats plus complexes pour l'étude de la polycyclisation.

The pseudo-first-order reaction kinetics of the reaction of phenyl isocyanate with water in 80 percent acetone and 20 percent water were studied using carbon dioxide evolution as a function of time as the reaction rate measurement. The activation parameters were determined from studies of the reaction rate at several different temperatures. Additionally, some catalytic and deuterium isotope effects were determined. From the results of these studies, a detailed mechanism of the reaction was proposed. The first step of the mechanism involves the formation of a cyclic intermediate and is the rate determining step.

Isocyanates have a broad spectrum of uses and they are used in the production of many products including polyurethane polymers, coatings, adhesives, paints and foams. While isocyanates are widely studied and well represented in the literature, nitrogen substituted isocyanates are quite rare. Amino and imino-isocyanates are examples of nitrogen substituted isocyanates. Previous work within the group studied the reactivity of these intermediates in the alkene aminocarbonylation reaction, and used hydrazones and hydrazides as precursors of nitrogen substituted isocyanates. From there, a second reaction pathway was studied. This involved the reactivity of hydrazones with nucleophiles to develop a simple exchange reaction. In this work, the substitution reactivity involving imino-isocyanates will be presented. This will include the scope of nucleophiles and hydrazones as well as a discussion on the formation of the imino-isocyanates. This reactivity allows for the facile formation of a variety of hydrazones with the flexibility to start from common hydrazone precursors.

The synthesis route for the preparation of polyurethane using 100% sustainable materials was proposed. Lignin, one of the most abundance biomass on Earth, was used as one raw material, while the other one used is soybean oil. The reaction occurs in 3 steps, and is done in 2 different pot reactions. Briefly, purchased epoxidized soybean oil is carbonated to synthesize carbonated soybean oil. Then carbonated soybean oil was reacted with coupling agent, 3-aminopropyltriethoxysilane to produce urethane monomers. Finally, prepared urethane monomers were polymerized with lignin to produce sustainable polyurethane. Molecular structures were intensively analyzed using Fourier-Transform Infrared Spectroscopy and Nuclear Magnetic Resonance Spectroscopy. In addition, mechanical properties of prepared polyurethane were analyzed in order to evaluate its performance and compare with the polyurethanes available commercially. Our results indicated that the highest tensile strength achieved was 1.4 MPa, which is slightly below the typical tensile strengths of processible polyurethane. Chemical properties of all the intermediates and products and implications for future research are discussed.

Thesis (Doctoral)--Ruhr-Universität Bochum, 1983.

München, Techn. Univ., Diss., 2004.

Isocyanates have a broad spectrum of uses and they are used in the production of many products including polyurethane polymers, coatings, adhesives, paints and foams. While isocyanates are widely studied and well represented in the literature, nitrogen substituted isocyanates are quite rare. Amino and imino-isocyanates are examples of nitrogen substituted isocyanates. Previous work within the group studied the reactivity of these intermediates in the alkene aminocarbonylation reaction, and used hydrazones and hydrazides as precursors of nitrogen substituted isocyanates. From there, a second reaction pathway was studied. This involved the reactivity of hydrazones with nucleophiles to develop a simple exchange reaction. In this work, the substitution reactivity involving imino-isocyanates will be presented. This will include the scope of nucleophiles and hydrazones as well as a discussion on the formation of the imino-isocyanates. This reactivity allows for the facile formation of a variety of hydrazones with the flexibility to start from common hydrazone precursors.

Parmi tous les plastiques, les polyuréthanes (PUs) représentent la sixième classe de polymères la plus utilisée au monde. Ils sont synthétisés industriellement par réaction entre un diol et un diisocyanate, en présence d'un catalyseur métallique et d’un solvant organique.Néanmoins, cette synthèse présente d’importants problèmes environnementaux et de santé.Afin de s’affranchir de ces composés toxiques, les progrès dans ce domaine ont conduit à un certain nombre de procédés sans isocyanates. Néanmoins, ces procédés doivent faire face à de nombreux défis (propriétés physiques, masses molaires, réactions secondaires, etc.), afin de concurrencer les polyuréthanes classiques. Par conséquent, une partie de ce manuscrit est dédiée à une étude rationnelle de l'influence de catalyseurs organiques, tels que le TBDou P4, non seulement sur la cinétique de polymérisation de l’aminolyse de carbonates biscycliques,mais aussi sur la structure et les propriétés des PUs résultants. Par la suite, et afin de limiter l’utilisation de composés organiques volatiles, des dispersions aqueuses de polyuréthanes sans isocyanates ont été obtenues en adaptant : 1) le procédé acétone à l’aminolysis de carbonates bis-cycliques et 2) la polymérisation interfaciale à la polycondensation de dicarbonates linéaires avec des diamines. / Among all plastic materials, polyurethanes (PUs) represent the 6th most popularly usedpolymers in the World. They are industrially synthesized by the reaction between a diol and adiisocyanate, in the presence of a metal catalyst and an organic solvent. Nevertheless, thissynthesis presents important environmental and health problems. In order to replace thesetoxic compounds, advances in this field have led to a number of isocyanate-free processes.However, these processes have to face many challenges (physical properties, molarmasses, side reactions, etc.), in order to compete with conventional polyurethanes.Therefore, part of this manuscript is dedicated to a rational study of the influence oforganocatalysts, such as TBD or P4, not only on the polymerization kinetics of the aminolysisof bis-cyclic carbonates, but also on the structure and properties of the resulting PUs.Subsequently, and in order to limit the use of volatile organic compounds, aqueousdispersions of non-isocyanate PUs were obtained by adapting: 1) the acetone process to theaminolysis of bis-cyclic carbonates and 2) the interfacial polymerization to thepolycondensation of linear dicarbonates with diamines.