Alkyle | EPFL Graph Search

Les alkyles dérivent des alcanes par la perte d'un atome d'hydrogène. Ils peuvent désigner des radicaux ou des substituants sur des molécules organiques complexes. Les alkyles ne sont pas considérés comme des groupes fonctionnels. Radicaux Les alkyles sont des radicaux hautement instables qui ne sont pas isolables à température ambiante. Substituants de molécules complexes Les chaînes hydrocarbonées sont le squelette de base en chimie organique. Dans de nombreux cas, selon les règles de nomenclature de l'IUPAC, un composé organique peut être considéré comme une chaîne ou un cycle prioritaire dans lequel certains des atomes d'hydrogène sont substitués par des groupes d'atomes. Les groupements alkyles peuvent jouer le rôle de substituant. Au sein d'une molécule organique, ces groupements sont peu réactifs (absence de groupes fonctionnels) et sont souvent associés au symbole « R » dans les représentations simplifiées. Nomenclature Les alkyles sont nommé

Simultaneous Generation of Methyl Esters and CO in Lignin Transformation

Paul Joseph Dyson, Mingyang Liu

Lignin is an abundant renewable carbon source. Due to its complex structure, utilization of lignin is very challenging. Herein, we describe an efficient strategy for the simultaneous utilization of lignin, in which the methoxy groups in lignin react with carboxylic acids to generate methyl carboxylates and the other alkyl and phenyl carbons react with oxygen to predominantly form CO that can be used directly in carbonylation reactions. The method was applied to the methylation of various functionalized aryl and alkyl carboxylic acids, including natural compounds, to produce valuable chemicals, including pharmaceuticals. No solid or liquid residues remain after the reaction. Mechanistic studies demonstrate that a well-ordered C-C and C-O bond activation sequence takes place to realize total transformation of lignin. This work opens a way for transformation of the entire lignin polymer into valuable products, exemplified by the synthesis of the pharmaceutical, Ramipril, on a gram scale.

WILEY-V C H VERLAG GMBH2022

Synthetic methodologies for C-C and C-N bond formation involving alkyl radicals

Guido Barzanò

C-C and C-N bonds are some of the most common structures in molecules ranging from drugs to catalysts and to food additives. Many coupling reactions were developed to form these types of bonds with excellent selectivity and good performance. Still, the synthesis of some of those species either depends on traditional methods or requires expensive and rare reagents and catalysts. The use of precious metals in chemistry, and particularly in the industry, can make molecular synthesis expensive and energy-intensive since the extraction of those materials is costly. Moreover, in homogeneous catalysis, the recovery of metal-based catalysts is almost impossible, making these processes unsustainable for the future. Thus, the discovery of chemical reactions that donât involve precious materials is indispensable. This thesis concentrates on the development of two chemical transformations, one performing an sp2-sp3 radical reductive coupling, one performing a photocatalyzed alkyl amination, involving inexpensive reagents and catalysts. The first chapter reviews the existing methodologies which use alkyl radicals to form carbon-carbon and carbon-nitrogen bonds. Alkyl radicals are formed from alkyl halides and pseudo-halides (Acids, esters, tosylates, etc.) via oxidation or reduction performed by metal or photoredox catalyst. The wide variety of available methodologies was illustrated, highlighting the advantages and weaknesses of each reaction. The second chapter of this dissertation is devoted to the development of a new iron-based catalytic method to form stereoselectively Z-alkene boron species from the corresponding boron-alkyne. This novel stereoselective method opens a new way to obtain these types of molecules with cheap reagents, in high yields, with excellent stereoselectivity (Z:E ratio >10:1), and with good tolerance of functional group. The reaction is radical based, avoiding the problem of beta-hydride elimination, which usually occurs in ionic reactions involving metal centers. In order to prove the versatility of this method, the vinyl boron compound formed from this reaction was used for further functionalizations. The formal total synthesis of a 5-HT2c receptor agonist was successfully performed, improving the overall yield of the process, and avoiding the use of expensive and polluting chemicals. The third chapter of this thesis is concentrated on the development of a tandem photoredox/metal base catalyzed functionalization of anilines and imines with alkyl carboxylic esters. In this reaction, no late transition metal is used, and the traditional metal-based photocatalyst is substituted with an inexpensive and more efficient organic dye. The alkylation of amines is a challenging topic in organic chemistry and classical nucleophilic substitution lacks selectivity and scope. Harvesting visible light with a photoredox catalyst opens the possibility to a radical pathway, making this coupling easy and with high tolerance for functional groups. In order to understand the catalytic cycle of the reaction, additional mechanistic studies were conducted, leading to some insight on how this reaction works.

EPFL2020

Structure-activity relationships of synthetic cannabinoid designer drug RCS-4 and its regioisomers and C4 homologues

Trent Michael Conroy

RCS-4 [(4-methoxyphenyl)-1-yl-(1-pentyl-1H-indol-3-yl)methanone] represents the first of several N-alkyl-3-(methoxybenzoyl)indoles identified by forensic scientists as synthetic cannabinoid (SC) designer drugs. Despite the detection of RCS-4 and several analogues (RCS-2, RCS-3, RCS-2-C4, RCS-3-C4, and RCS-4-C4) in products intended for human consumption, relatively little is known about this class of cannabinoids. The synthesis of all regioisomers of RCS-4 and their C4 homologues is described. This study also systematically explored the structure-activity relationships of this class of SCs at human CB1 and CB2 receptors using an in vitro fluorometric imaging plate reader membrane potential assay. All compounds demonstrated agonist activity at CB1 (EC50 = 54-574 nM) and CB2 (EC50 = 4.5-46 nM) receptors, with the C4 homologues showing a preference for CB2 receptors over CB1 receptors (31-42 times). Since most of the analogues (RCS-2, RCS-3, RCS-2-C4, RCS-3-C4 and RCS-4-C4) are not subject to regulation in much of the world, despite their activities towards CB1 and CB2 receptors, there is a possibility that these analogues will emerge on the black market.

Springer2015

Synthetic methodologies for C-C and C-N bond formation involving alkyl radicals

Guido Barzanò

EPFL2020