Academic literature on the topic 'Heteocycles'

In this paper, we introduce a novel and convenient method for the transformation of heterocyclic amides into heteocyclic thioamides. A two-step approach was applied for this transformation: Firstly, we applied a chlorination of the heterocyclic amides to afford the corresponding chloroheterocycles. Secondly, the chloroherocycles and N-cyclohexyl dithiocarbamate cyclohexylammonium salt were heated in chloroform for 12 h at 61 °C to afford heteocyclic thioamides in excellent yields.

The title compound, C26H38N5P, was synthesized by reacting 2-chloro-1,3-bis(2,6-diisopropylphenyl)-1,3,2-diazaphospholidine with sodium azide and a catalytic amount of lithium chloride in tetrahydrofuran. The title compound is the first structurally characterized 2-azido-1,3,2-diazaphospholidine and exhibits a P atom in a trigonal pyramidal geometry. The azide P—N bond length of 1.8547 (16) Å is significantly longer than the P—N separations for the chelating diamine [P—N = 1.6680 (15) and 1.6684 (14) Å]. The sterically hindered 2,6-diisopropylphenyl groups twist away from the central heterocycle, with dihedral angles between the central heteocyclic ring and benzene rings of 76.17 (10) and 79.74 (9)°. In the crystal, a weak C—H...N link to the terminal N atom of the azide group leads to [100] chains.

Four main series of novel heterocyclic compounds were successfully syniliesised. Two of these series were found to be post-emergence herbicides with the activities of each being based on a different mode of action. The (pyrazole-4-yl)alkanones are inhibitors of protoporphyrinogen oxidase, an enzyme in chlorophyll biosynthesis, whereas alkyl 3-arylsulfonylamino- 3-methyllhio-2-(pyrimidin-2-ylcarbamoyl)acrylates and pyrimidin-2-yl 3-(2- chlorophenyl)sulfonyl-amino-3-methylthio-2-cyanoacrylamides (collectively termed "vinylogous sulfonylureas") are inhibitors of acetohydroxy acid synthase (AHAS). an enzyme in branched-chain amino acid biosynthesis. Both these enzymes are established targets for current commercial herbicides. Studies of the utility of 2-(l-ethoxyalkylidene)-3-oxoaIkanenitriles (acrylonilriles) in heterocycle synthesis were facilitated by the recent development of a convenient route to these starting materials. Acrytonitriles were reacted with different hydrazines to give (pyrazol-4-yl)alkanones and pyrazole-4-carbonitriles in varying proportions depending on the reaction conditions and the substituents on the reactants. Although distinction between alternative 3- and 5-substituted pyrazoles is a perennial problem in pyrazole synthesis, in this case the products of these reactions were successfully characterised and identified using a range of n.m.r. spectroscopy techniques. Once the herbicidal mode of action of the (pyrazol-4-yl)alkanones had been confirmed, synthesis of a series of analogues allowed the structural elements contributing to biological activity to be identified. The reaction of acrylonitriles with bidetate nucleophiles such as thiourea gave novel pyrimidines. but these compounds were not herbicidal. The vinylogous sulfonylureas were synthesised using established procedures to obtain novel compounds structurally related to the commercial herbicide chlorsulfuron. The biological activity of the vinylogous sulfonylureas was found to be sensitive to apparently minor changes in structure, but x-ray crystallographically-generated structures of an active and an inactive member of the series revealed marked differences in conformation. Some of the vinylogous sulfonylureas were used as synthons for pyrazole and pyrazolopyrimidine derivatives. Although these compounds did not exhibit herbicidal activity, this synthesis provided the basis for some interesting chemistry. Unexpected elimination of the arylsulfonylamino group was observed when a vinylogous sulfonyurea was treated with methyl hydrazine. In order to confirm the identity of the 3-methylthiopyrazole product, model compounds were synthesised using alternative routes. The resulting pairs of 3- and 5-substituted pyrazoles were characterised using n.m.r spectroscopy.

Les tétrahydro-β-carbolines sont des motifs présents dans de nombreux produits naturels. La plupart de ces produits étant chiraux, il est particulièrement important de contrôler la stéréochimie absolue du carbone stéréogène des tétrahydro-β-carbolines. La catalyse énantiosélective à l’Au(I) est un domaine en pleine expansion. Nous décrivons dans cette thèse le développement d’une réaction de Pictet-Spengler énantiosélective catalysée par des complexes d’Au(I) chiraux. Nous avons pu synthétiser plus de 40 tétrahydro-β-carbolines à partir d’aldéhydes fonctionnalisés avec des excès énantiomériques associés allant jusqu’à 95 %. L’Au(I) n’étant pas un métal connu pour catalyser cette classe de réaction, celle-ci procède par un mécanisme original d’auration d’indole. Pour tenter de démontrer la vraisemblance du mécanisme réactionnel proposé, nous avons réalisé des études expérimentales et théoriques par calculs DFT. Nous avons par la suite étendu cette nouvelle réactivité de l’Au(I) à d’autres réactions de Pictet-Spengler en utilisant des analogues de tryptamines. Enfin, nous avons mis au point la synthèse de motifs indoloquinuclidines. Ces derniers ont été synthétisés de manière énantiosélective en combinant l’organocatalyse par des acides phosphoriques chiraux et la catalyse à l’Au(I)
Tetrahydro-β-carbolines are moieties commonly found in many natural products. Most of them being chiral compounds, it is of high importance to be able to control the stereochemistry of the chiral center of the tetrahydro-β-carbolines. Enantioselective gold catalysis has been developping for a few years. In this PhD work, we report the development of an enantioselective Pictet-Spengler reaction using chiral Au(I) complexes. We were able to synthesize more than 40 enantioenriched tetrahydro-β-carbolines with enantiomeric excesses up to 95 %. It is surprising that a Au(I) complex is able to catalyse such a reaction. It hence process via an original mechanism including an auration step of the indole. In order to solve the mechanism of this reaction, we performed both experimental and computational studies. We then extented this new Au(I) reactivity to other Pictet-Spengler like reactions using analogs of tryptamines. At last, we have developed the synthesis of new indoloquinuclidines scaffolds. Those molecules were synthesized in an enantioselective manner using the combination of organocatalysis with chiral phosphoric acids and gold catalysis