Insight into the copper-catalyzed borylation of strained alkenes

This document is the accepted manuscript version of a published work that appeared in final form in Synlett 2015; 26(04): 494-500, copyright © Georg Thieme Verlag Stuttgart · New York after peer review and technical editing by the publisher. To access the final online work see DOI: 10.1055/s-0034-1379882The copper-catalyzed hydro- and carboboration of strain alkenes is presented. The reaction is highly diastereoselective and affords boronic ester derivatives many of which are difficult to synthesize by known methods. Competition experiments with different alkenes show that high levels of chemoselectivity can be achieved. DFT calculations are in agreement with the observed chemoselectivityWe thank the European Research Council (ERC-337776) and MINECO (CTQ2012-35957 and CTQ2013-43698-P) for financial support. M. T. and S. D.-T thank MINECO for RyC contracts. A. P. thanks MINECO for JyC contrac

N,N′-Di-Boc-2H-Isoindole-2-carboxamidine—First Guanidine-Substituted Isoindole

Synthesis of N, N′-Di-Boc-2H-isoindole-2-carboxamidine, the first representative of isoindoles containing guanidine functionality, was carried out. The cycloaddition reactivity of this new Diels–Alder heterodiene was studied and the title compound was employed as a cycloaddition delivery reagent for guanidine functionality. Higher reactivity was found in comparison with the corresponding pyrrole derivative. Substitution with fluorine or guanidine functionality does not change the reactivities of isoindoles, and these findings are in good accord with computational results

Nickel-catalyzed cocyclotrimerization of oxa- and azabenzonorbornadienes with alkynes: reaction with multiple synthetic applications

[[abstract]]Oxa- and azabenzonorbornadienes react with alkynes in the presence of nickel complexes to give the corresponding [2 + 2 + 2] cycloadducts; these reactions can be applied to the construction of multiple fused rings, the preparation of precursors of isobenzofurans and isoindoles and aromatic compounds.[[fileno]]2010326010022[[department]]化學

Bio-orthogonal Fluorescent Labelling of Biopolymers through Inverse-Electron-Demand Diels–Alder Reactions

Bio-ort hogona llabellin gschemes based on inverse-elec tron- deman dDiels–Ald er (IEDDA) cycloa ddition have attracted much attention in chem ical biology recently .The appeal ing features of this reactio n, such as the fast reactio nkinetics, fully bio-ort hogonal nature and high selectiv ity,have helped chem i- cal biologists gain deeper understandi ng of biochemic al pro- cesses at the molecular level.Listing the compo nents and dis- cussing the possib ilities andlimitations of thesereagent s, we provid earecent snapshot of the field of IEDDA -based biomo- lecular manipulatio nwith special focus on fluores cent modula- tion approaches throug hthe use of bio-orthogon alized build- ing blocks. At the end, we discuss challenges that need to be addres sed for further develop ments in order to overcome recent limita tions and to enabl eresearchers to answer biomo - lecular quest ions in more detail

Beyond Carbon: Enantioselective and Enantiospecific Reactions with Catalytically Generated Boryl- and Silylcopper Intermediates

Catalytic asymmetric C-C bond formation with alkylcopper intermediates as carbon nucleophiles is now textbook chemistry. Related chemistry with boron and silicon nucleophiles where the boryl- and accordingly silylcopper intermediates are catalytically regenerated from bench-stable pronucleophiles had been underdeveloped for years or did not even exist until recently. Over the past decade, asymmetric copper catalysis employing those main-group elements as nucleophiles rapidly transformed into a huge field in its own right with an impressive breadth of enantioselective C-B and C-Si bond-forming reactions, respectively. Its current state of the art does not have to shy away from comparison with that of boron's and silicon's common neighbor in the periodic table, carbon. This Outlook is not meant to be a detailed summary of those manifold advances. It rather aims at providing a brief conceptual summary of what forms the basis of the latest exciting progress, especially in the area of three-component reactions and cross-coupling reactions

Design and Synthesis of Ruthenium based Olefin Metathesis Catalysts

The present Master thesis seeks to develop new unsymmetrical ruthenium-based olefin metathesis catalysts and therein a better understanding of olefin metathesis catalysis with unsymmetrical active complexes. Such catalysts have a potential for chemoselectivity and in best case, stereoselectivity. Two different classes of catalysts, coordinated by a hemilabile amine ligand and by a novel N-heterocyclic carbene (NHC) ligand respectively, have been investigated. Two new amine-based olefin metathesis catalysts have been synthesized and tested. In addition, quantum chemical calculations to study the catalysts were performed to give a better knowledge about their behaviour in catalytic olefin metathesis. Prior to the main calculations a validation study was performed to identify the most accurate and effective method of optimizing geometries. The catalysts are shown to be temperature dependent catalysts (latent catalysts) with high thermal stability, which makes them interesting for some industrial applications. The results from the experiments and the calculations are combined to give a better understanding of the catalyst and their properties. However, the analysis of the results for the amine-based catalysts, suggests a limited potential for E/Z-stereoselectivity. To explore a different potentially stereoselective design, a novel sterically demanding bidentate NHC ligand was synthesized. Unfortunately, any attempt to synthesize a corresponding olefin metathesis failed. Instead, we succeeded to synthesize a novel iridium(I) complex containing the novel bidentate NHC ligand. The iridium complex could have potential for catalytic hydrogenation by further adjustments.MAMN-KJEMKJEM39

Design and Synthesis of Ruthenium based Olefin Metathesis Catalysts

The present Master thesis seeks to develop new unsymmetrical ruthenium-based olefin metathesis catalysts and therein a better understanding of olefin metathesis catalysis with unsymmetrical active complexes. Such catalysts have a potential for chemoselectivity and in best case, stereoselectivity. Two different classes of catalysts, coordinated by a hemilabile amine ligand and by a novel N-heterocyclic carbene (NHC) ligand respectively, have been investigated. Two new amine-based olefin metathesis catalysts have been synthesized and tested. In addition, quantum chemical calculations to study the catalysts were performed to give a better knowledge about their behaviour in catalytic olefin metathesis. Prior to the main calculations a validation study was performed to identify the most accurate and effective method of optimizing geometries. The catalysts are shown to be temperature dependent catalysts (latent catalysts) with high thermal stability, which makes them interesting for some industrial applications. The results from the experiments and the calculations are combined to give a better understanding of the catalyst and their properties. However, the analysis of the results for the amine-based catalysts, suggests a limited potential for E/Z-stereoselectivity. To explore a different potentially stereoselective design, a novel sterically demanding bidentate NHC ligand was synthesized. Unfortunately, any attempt to synthesize a corresponding olefin metathesis failed. Instead, we succeeded to synthesize a novel iridium(I) complex containing the novel bidentate NHC ligand. The iridium complex could have potential for catalytic hydrogenation by further adjustments

Part 1: Towards the Synthesis of Pyrene Zigzag Cyclacenes, Part 2: New Methods for the Synthesis of Conjugated Polymers

Part 1: Carbon nanotubes (CNTs) are allotropes of carbon that have emerged as candidates for implementation in electronic devices ranging from transistors to solar cells. Unfortunately, the behavior of CNTs is highly dependent on their structure and modern synthetic methods for generating CNTs are not able to provide uniform samples for electronic applications. Recently, the synthesis of cycloparaphenylenes (CPPs), which closely resemble metallic CNTs, has been elucidated and has since been further expanded to allow for the CPPs of varying diameters and subunits. More importantly, CPPs were also shown to allow for the controlled bottom-up synthesis of CNTs, opening the door towards the concise synthesis of CNTs. Herein, we will outline our synthetic attempts towards the synthesis of zigzag cyclacenes and how the creation of a zigzag nanobelt could bring forth the defined synthesis of semiconducting zigzag nanotubes. Drawing inspiration from previous attempts at cyclacenes and the successful synthesis of CPPs, we set out to construct a zigzag macrocycle using a Diels-Alder approach with pyrene as the backbone of the cycle. We were able to successfully construct the cyclic precursor to the cyclacene following numerous attempts; however, isolation of the fully aromatized product was not accomplished because the strain exhibited by the cycle led to an over reduction. Our search to create cyclacenes led us towards phosphonium salts as a new method for the mild creation of benzyne. Unfortunately, the phosphonium benzyne performed poorly due to regioselectivity issues, but in trying to create the aryl phosphonium salts, we created a new route towards these compounds. Herein, we will describe our development of a metal free synthesis of aryl phosphonium salts. When aryl halides are irradiated with UV light in the presence of a phosphine, the two species can couple leading to the formation of the phosphonium salt. The reaction is amenable to a variety of phosphines and can proceed with aryl chlorides, iodides, bromides, and pseudohalides. Part 2: Conjugated polymers have gained a great deal of interest as these compounds can be used as active materials and enable the creation of lightweight, flexible, and low-cost electronic devices. Critical to the advancement of these technologies is the creation of new synthetic methods and facile access to material. Herein, we will outline the development of new synthetic techniques for the creating conjugated polymers. First, we will discuss the development of a new metal free dehydrative polymerization of thiazole N-oxides. Drawing inspiration from nature and from the industrial synthesis of commodity polymers, such as PET and nylon-6,6, we developed a new transformation that can dimerize thiazole N-oxides in the absence of a metal with the formal loss of water being the sole byproduct. This methodology was later extended onto bifunctional monomers and allowed for the synthesis of conjugated polymers in quantitative yield and good molecular weights. Secondly, we will discuss the design and synthesis of a new palladium precatalyst for the synthesis of conjugated polymers through direct arylation polymerization. Conjugated polymers are mostly synthesized using transition metal couplings such as Stille or Suzuki couplings; however, these methods require pre- functionalization and can leave behind toxic byproducts. Direct arylation polymerization has recently emerged as a new technique for synthesizing conjugated polymers; however, the nature of the propagating species means that conjugated polymers created this way are more prone to branching/crosslinking defects. We designed a palladium precatalyst specifically for direct arylation polymerization that can reduce unwanted functionalization while providing good molecular weights, high yields, lower loadings, and improved thermal properties