Photoactive EDA complexes in visible light driven aerobic oxidations

Organic synthesis driven by photochemical activation has been proven very promising in a range of scenarios within academia and industry. The emergence of photoredox catalysis has fueled an ever-growing interest in the use of visible light as a convenient energy source for a variety of radical reactions otherwise difficult to achieve. However, the use of homogeneous catalysts, based on transition metals or complicated organic dyes as the light harvesting moiety, does not come without drawbacks. Problems include the price and availability of ruthenium and iridium, and the separation and re-use of the catalysts from the products. Photochemical transformations that use simpler systems, such as catalyst-free versions or small organic molecules as photocatalysts, are therefore attractive to develop. For certain systems, one potential solution to these problems is the use of electron donor-acceptor (EDA) complexes. These complexes can form between a molecule of high electron affinity (acceptor) and a molecule of low ionization potential (donor). A key feature of the EDA complex is that it can be excited with light of a lower energy than that needed to excite the reactants on their own. The excitation of the complex can result in the formation of reactive radical species that can be harvested for further chemical reactions. EDA complexes can, with other words, be used as a convenient light-absorbing moiety to drive chemical reactions without the need of an external photocatalyst.\ua0Oxidation reactions are a universal part of organic chemistry. The oxidants commonly used are however associated with certain drawbacks such as troublesome waste production. Oxygen obtained from the air around us is a potentially ideal alternative. The use of aerobic conditions in the combination with photoactive EDA complexes poses an interesting and underdeveloped part of photochemical transformations. In this thesis, an EDA complex approach to the synthesis of N-heterocycles has been investigated. The developed methods use alkylated anilines as donors and activated alkenes as acceptors to form different EDA complexes. Visible light is used to activate the complexes, and aerobic oxygen is used as the terminal oxidant to furnish the target compounds. In the first part of the thesis, new EDA complexes between dialkyl anilines and 1,2-dibenzoyl ethylenes are identified. The results show that upon excitation of the EDA complexes, 3,4-disubstituted tetrahydroquinolines can be formed in excellent diastereoselectivity and in high yields. In the second part, the identified EDA complexes are used as part of a catalytic system for the generation of α-amino alkyl radicals under aerobic conditions and under visible light irradiation. Lastly, in the third part, new EDA complexes between arylated amino acids and maleimides are identified. The photoactivation of these complexes was shown to be an efficient way of generating secondary α-amino alkyl radicals to furnish N-H-tetrahydroquinolines

Aerobic Oxidative EDA Catalysis: Synthesis of Tetrahydroquinolines Using an Organocatalytic EDA Active Acceptor

A catalytic electron donor-acceptor (EDA) complex for the visible-light-driven annulation reaction between activated alkenes and N,N-substituted dialkyl anilines is reported. The key photoactive complex is formed in situ between dialkylated anilines as donors and 1,2-dibenzoylethylene as a catalytic acceptor. The catalytic acceptor is regenerated by aerobic oxidation. Investigations into the mechanism are provided, revealing a rare example of a catalytic acceptor in photoactive EDA complexes that can give access to selective functionalization of aromatic amines under mild photochemical conditions

Overcoming Back Electron Transfer in the Electron Donor-Acceptor Complex-Mediated Visible Light-Driven Generation of α-Aminoalkyl Radicals from Secondary Anilines

An additive-free, visible light-driven annulation between N-aryl amino acids and maleimide to form tetrahydroquinolines (THQs) is disclosed. Photochemical activation of an electron donor-acceptor (EDA) complex between amino acids and maleimides drives the reaction, and aerobic oxygen acts as the terminal oxidant in the net oxidative process. A range of N-aryl amino acids and maleimides have been investigated as substrates to furnish the target THQ in good to excellent yield. Mechanistic investigations, including titration and UV-vis studies, demonstrate the key role of the EDA complex as the photoactive species

The effects of historical fragmentation on major histocompatibility complex class II β and microsatellite variation in the Aegean island reptile, Podarcis erhardii

The major histocompatibility complex (MHC) plays a key role in disease resistance and is the most polymorphic gene region in vertebrates. Although habitat fragmentation is predicted to lead to a loss in MHC variation through drift, the impact of other evolutionary forces may counter this effect. Here we assess the impact of selection, drift, migration, and recombination on MHC class II and microsatellite variability in 14 island populations of the Aegean wall lizard Podarcis erhardii. Lizards were sampled from islands within the Cyclades (Greece) formed by rising sea levels as the last glacial maximum approximately 20,000 before present. Bathymetric data were used to determine the area and age of each island, allowing us to infer the corresponding magnitude and timing of genetic bottlenecks associated with island formation. Both MHC and microsatellite variation were positively associated with island area, supporting the hypothesis that drift governs neutral and adaptive variation in this system. However, MHC but not microsatellite variability declined significantly with island age. This discrepancy is likely due to the fact that microsatellites attain mutation-drift equilibrium more rapidly than MHC. Although we detected signals of balancing selection, recombination and migration, the effects of these evolutionary processes appeared negligible relative to drift. This study demonstrates how land bridge islands can provide novel insights into the impact of historical fragmentation on genetic diversity as well as help disentangle the effects of different evolutionary forces on neutral and adaptive diversity

Hybridization and gene expression : Beyond differentially expressed genes

Gene expression has a key role in reproductive isolation, and studies of hybrid gene expression have identified mechanisms causing hybrid sterility. Here, we review the evidence for altered gene expression following hybridization and outline the mechanisms shown to contribute to altered gene expression in hybrids. Transgressive gene expression, transcending that of both parental species, is pervasive in early generation sterile hybrids, but also frequently observed in viable, fertile hybrids. We highlight studies showing that hybridization can result in transgressive gene expression, also in established hybrid lineages or species. Such extreme patterns of gene expression in stabilized hybrid taxa suggest that altered hybrid gene expression may result in hybridization-derived evolutionary novelty. We also conclude that while patterns of misexpression in hybrids are well documented, the understanding of the mechanisms causing misexpression is lagging. We argue that jointly assessing differences in cell composition and cell-specific changes in gene expression in hybrids, in addition to assessing changes in chromatin and methylation, will significantly advance our understanding of the basis of altered gene expression. Moreover, uncovering to what extent evolution of gene expression results in altered expression for individual genes, or entire networks of genes, will advance our understanding of how selection moulds gene expression. Finally, we argue that jointly studying the dual roles of altered hybrid gene expression, serving both as a mechanism for reproductive isolation and as a substrate for hybrid ecological adaptation, will lead to significant advances in our understanding of the evolution of gene expression

Hybridization and gene expression: Beyond differentially expressed genes

Gene expression has a key role in reproductive isolation, and studies of hybrid gene expression have identified mechanisms causing hybrid sterility. Here, we review the evidence for altered gene expression following hybridization and outline the mechanisms shown to contribute to altered gene expression in hybrids. Transgressive gene expression, transcending that of both parental species, is pervasive in early generation sterile hybrids, but also frequently observed in viable, fertile hybrids. We highlight studies showing that hybridization can result in transgressive gene expression, also in established hybrid lineages or species. Such extreme patterns of gene expression in stabilized hybrid taxa suggest that altered hybrid gene expression may result in hybridization-derived evolutionary novelty. We also conclude that while patterns of misexpression in hybrids are well documented, the understanding of the mechanisms causing misexpression is lagging. We argue that jointly assessing differences in cell composition and cell-specific changes in gene expression in hybrids, in addition to assessing changes in chromatin and methylation, will significantly advance our understanding of the basis of altered gene expression. Moreover, uncovering to what extent evolution of gene expression results in altered expression for individual genes, or entire networks of genes, will advance our understanding of how selection moulds gene expression. Finally, we argue that jointly studying the dual roles of altered hybrid gene expression, serving both as a mechanism for reproductive isolation and as a substrate for hybrid ecological adaptation, will lead to significant advances in our understanding of the evolution of gene expression

Visible-Light-Driven Stereoselective Annulation of Alkyl Anilines and Dibenzoylethylenes via Electron Donor-Acceptor Complexes

A catalyst-free, stereoselective visible-light-driven annulation reaction between alkenes and N,N-substituted dialkyl anilines for the synthesis of substituted tetrahydroquinolines is presented. The reaction is driven by the photoexcitation of an electron donor-acceptor (EDA) complex, and the resulting products are obtained in good to high yields with complete diastereoselectivity. Mechanistic rationale and photochemical characterization of the EDA-complex are provided

Rare Events in Remote Dark-Field Spectroscopy: An Ecological Case Study of Insects

In this paper, a novel detection scheme for the monitoring of insect ecosystems is presented. Our method is based on the remote acquisition of passive sunlight scattering by two insect species. Procedures to identify rare events in remote dark-field spectroscopy are explained. We further demonstrate how to reduce the spectral representation, and how to discriminate between sexes, using a hierarchical clustering analysis. One-day cycle showing the temporal activities of the two sexes as well as data on activity patterns in relation to temperature and wind is presented. We also give a few examples of the potential use of the technique for studying interactions between sexes on a time scale of milliseconds

Interpopulational and seasonal variation in the chemical signals of the lizard Gallotia galloti

Communicative traits are strikingly diverse and may vary among populations of the same species. Within a population, these traits may also display seasonal variation. Chemical signals play a key role in the communication of many taxa. However, we still know far too little about chemical communication in some vertebrate groups. In lizards, only a few studies have examined interpopulational variation in the composition of chemical cues and signals and only one study has explored the seasonal effects. Here we sampled three subspecies of the Tenerife lizards (Gallotia galloti) and analyze the lipophilic fraction of their femoral gland secretions to characterize the potential interpopulational variation in the chemical signals. In addition, we assessed whether composition of these secretions differed between the reproductive and the non-reproductive season. We analyzed variations in both the overall chemical profile and the abundance of the two main compounds (cholesterol and vitamin E). Our results show interpopulational and seasonal differences in G. gallotia chemical profiles. These findings are in accordance with the high interpopulational variability of compounds observed in lizard chemical signals and show that their composition is not only shaped by selective factors linked to reproductive season

Sexual selection and population divergence I. the influence of socially flexible cuticular hydrocarbon expression in male field crickets (Teleogryllus oceanicus).

This is the peer reviewed version of the article which has been published in final form at DOI: 10.1111/evo.12839.© 2015 The Author(s). Evolution © 2015 The Society for the Study of Evolution.Debates about how coevolution of sexual traits and preferences might promote evolutionary diversification have permeated speciation research for over a century. Recent work demonstrates that the expression of such traits can be sensitive to variation in the social environment. Here we examined social flexibility in a sexually selected male trait - cuticular hydrocarbon (CHC) profiles - in the field cricket Teleogryllus oceanicus and tested whether population genetic divergence predicts the extent or direction of social flexibility in allopatric populations. We manipulated male crickets' social environments during rearing and then characterised CHC profiles. CHC signatures varied considerably across populations and also in response to the social environment, but our prediction that increased social flexibility would be selected in more recently founded populations exposed to fluctuating demographic environments was unsupported. Furthermore, models examining the influence of drift and selection failed to support a role of sexual selection in driving population divergence in CHC profiles. Variation in social environments might alter the dynamics of sexual selection, but our results align with theoretical predictions that the role social flexibility plays in modulating evolutionary divergence depends critically on whether responses to variation in the social environment are homogeneous across populations, or whether gene-by-social-environment interactions occur. This article is protected by copyright. All rights reserved.Natural Environment Research Council (NERC)University of California Pacific Rim Research GrantRoyal SocietyBiotechnology and Biological Sciences Research Council (BBSRC)Erasmus Exchang