Preparation of Macrocyclic

The first examples of catalyst-controlled stereoselective macrocyclic ring-closing metathesis reactions that generate Z-enoates as well as (E,Z)- or (Z,E)-dienoates are disclosed. Reactions promoted by 3.0–10 mol % of a Mo-based monoaryloxide pyrrolide complex proceed to completion within 2–6 h at room temperature. The desired macrocycles are formed in 79:21 to >98:2 Z/E selectivity; stereoisomerically pure products can be obtained in 43–75% yield after chromatography. Utility is demonstrated by application to a concise formal synthesis of the natural product (+)-aspicilin.United States. National Institutes of Health (GM-59426

Toward a simulation approach for alkene ring-closing metathesis : scope and limitations of a model for RCM

A published model for revealing solvent effects on the ring-closing metathesis (RCM) reaction of di-Et diallylmalonate 7 has been evaluated over a wider range of conditions, to assess its suitability for new applications. Unfortunately, the model is too flexible and the published rate consts. do not agree with exptl. studies in the literature. However, by fixing the values of important rate consts. and restricting the concn. ranges studied, useful conclusions can be drawn about the relative rates of RCM of different substrates, precatalyst concn. can be simulated accurately and the effect of precatalyst loading can be anticipated. Progress has also been made toward applying the model to precatalyst evaluation, but further modifications to the model are necessary to achieve much broader aims

The influence of structure on reactivity in alkene metathesis

Abstract Alkene metathesis has grown from a niche technique to a common component of the synthetic organic chemistry toolbox, driven in part by the development of more active catalyst systems, or those optimized for particular purposes. While the range of synthetic chemistry achieved has been exciting, the effects of structure on reactivity have not always been particularly clear, and rarely quantified. Understanding these relationships is important when designing new catalysts, reactions, and syntheses. Here, we examine what is known about the effect of structure on reactivity from two perspectives: the catalyst, and the substrate. The initiation of the precatalyst determines the rate at which active catalyst enters the catalytic cycle; the rate and selectivity of the alkene metathesis reaction is dependent on how the substrate and active catalyst interact. The tools deployed in modern studies of mechanism and structure/activity relationships in alkene metathesis are discussed

Gesellschaft mit beschränkter Haftung

EXIT-Klauseln ermöglichen es den Ausstieg eines Gesellschaftersbestmöglich zu kontrollieren und auszugestalten, bzw. den Ausstieg zu erzwingen. Shoot-Out-Klauseln stellen eine Möglichkeit dar Gesellschafterstreitigkeiten zu lösen und einen Mitgesellschafter aus der Gesellschaft zu verdrängen. In der Masterarbeit werden insbesondere die Russian-Roulette und die Texas-Shoot-Out Klausel analysiert und in das österreichische Rechtssystem eingeordnet. Zudem wird das GesAusG als gesetzlich normierte Möglichkeit des Gesellschafterausschlusses betrachtet und des Weiteren Bezug auf Aufgriffsrechte und Mitverkauftrechte- und Pflichten genommen.Stefan Torker, BSc.Masterarbeit Universität Klagenfurt 202

Mechanistically designed dual-site catalysts for the alternating ROMP of norbornene and cyclooctene

A chelating P,O ligand, designed according to recently worked-out mechanistic concepts, converts an unselective first-generation ruthenium carbene complex into a chemoselective ROMP catalyst that assembles an alternating copolymer from a mixture of norbornene and cyclooctene

Mechanistically designed dual-site catalysts for the alternating ROMP of norbornene and cyclooctene

A chelating P,O ligand, designed according to recently worked-out mechanistic concepts, converts an unselective first-generation ruthenium carbene complex into a chemoselective ROMP catalyst that assembles an alternating copolymer from a mixture of norbornene and cyclooctene