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Electron-rich Arenes (electron-rich + arene)
Selected AbstractsOptimization of the Azobenzene Scaffold for Reductive Cleavage by Dithionite; Development of an Azobenzene Cleavable Linker for Proteomic ApplicationsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 23 2010Geoffray Leriche Abstract In this paper we conducted an extensive reactivity study to determine the key structural features that favour the dithionite-triggered reductive cleavage of the azo,arene group. Our stepwise investigation allowed identification of a highly reactive azo,arene structure 25 bearing a carboxylic acid at the ortho position of the electron-poor arene and an ortho - O -alkyl-resorcinol as the electron-rich arene. Based on this 2-(2,-alkoxy-4,-hydroxyphenylazo)benzoic acid (HAZA) scaffold, the orthogonally protected difunctional azo,arene cleavable linker 26 was designed and synthesized. Selective linker deprotection and derivatization was performed by introducing an alkyne reactive group and a biotin affinity tag. This optimized azo,arene cleavable linker led to a total cleavage in less than 10 s with only 1 mM dithionite. Similar results were obtained in biological media. [source] Enantioselective Organocatalytic Synthesis of Arylglycines via Friedel,Crafts Alkylation of Arenes with a Glyoxylate ImineADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2010Dieter Enders Abstract The enantioselective organocatalytic synthesis of arylglycines has been developed employing 1,mol% of an enantiopure N -triflyl phosphoramide Brønsted acid as organocatalyst. Various differently substituted phenylglycine derivatives can be synthesized in good to excellent yields and enantiomeric excesses based on a Friedel,Crafts alkylation of electron-rich arenes with a glyoxylate imine. A novel protocol for the deprotection of the N - tert -butylsulfonyl (Bus) group has also been developed. [source] One-Pot, Regioselective Synthesis of Substituted Arylglycines for Kinetic Resolution by Penicillin G AcylaseADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2008Peter Grundmann Abstract Amido-alkylation of electron-rich arenes with phenylacetamide and glyoxylic acid offers an inexpensive route to a large variety of N -phenylacetylated arylglycines that are suited for immediate enzymatic resolution by penicillin G acylase. When performed under mild conditions at 5,°C in acetic acid/HCl, this simple one-pot operation resulted in the formation of single regioisomers only (,98%). Subsequent kinetic resolution of the amino acid derivatives by penicillin G acylase at pH,8.0 occurred generally with E values>100 and thus furnished free (S)-configurated arylglycines with high enantiomeric purity. The corresponding enantiopure (R)-substrates, easily separable by a phase-selective extraction process, provided the corresponding (R)-enantiomers upon conventional hydrolysis. This one-pot, two-step procedure for arylglycine synthesis, resolution and work-up requires a minimum of equipment and grants rapid access to both enantiopure (S)- and (R)-antipodes of non-natural ,-amino acids in small- to large-scale quantities. [source] Gold(III) Chloride-Catalyzed Addition Reactions of Electron-Rich Arenes to Methyl Vinyl KetoneADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11 2003Gerald Dyker Abstract For the reaction of ,,,-unsaturated ketones with electron-rich arenes catalyzed by gold(III) chloride both, a Friedel,Crafts-type mechanism and an initial metallation, are evaluated. Gold(III) chloride has proven to be an efficient catalyst under very moderate reaction conditions, however, in the case of sterically demanding products HBF4 turned out to be the superior catalyst. [source] The Reaction of o -Alkynylarene and Heteroarene Carboxaldehyde Derivatives with Iodonium Ions and Nucleophiles: A Versatile and Regioselective Synthesis of 1H -Isochromene, Naphthalene, Indole, Benzofuran, and Benzothiophene CompoundsCHEMISTRY - A EUROPEAN JOURNAL, Issue 22 2006José Barluenga Prof. Dr. Abstract The reaction of o -alkynylbenzaldehydes 1 with different alcohols, silylated nucleophiles 5, electron-rich arenes 10, and heteroarenes 12 in the presence of the reagent IPy2BF4, at room temperature, gave functionalized 4-iodo-1H -isochromenes 2, 6, 11, and 13 in a regioselective manner. When alkynes 16 and alkenes 19 and 20 were used as nucleophiles, a regioselective benzannulation reaction took place to form 1-iodonaphthalenes 17 and 1-naphthyl ketones 18, respectively. Moreover, the latter process has been adapted to accomplish the synthesis of indole, benzofuran, and benzothiophene derivatives (23, 27, and 28, respectively). The three patterns of reactivity observed for the o -alkynylbenzaldehyde derivatives with IPy2BF4 stem from a common iodinated isobenzopyrylium ion intermediate, A, that evolves in a different way depending on the nucleophile present in the reaction medium. A mechanism is proposed and the different reaction pathways observed as a function of the type of nucleophile are discussed. Furthermore, the reaction of the o -hexynylbenzaldehyde 1,b with styrene was monitored by NMR spectroscopy. Compound III, a resting state for the common intermediate in the absence of acid, has been isolated. Its evolution in acid media has been also tested, thereby providing support to the proposed mechanism. [source] | ||||||||||