Search

The 1,2,3-triazole scaffold is an important pharmacophore and a versatile, increasingly leveraged, substructure in biochemical, materials, polymer, and metal-coordinating applications. Continuing advances in 1,2,3-triazole construction, by either non-catalyzed or metal-catalyzed azide/alkyne cycloaddition, foster further creative use. The work reported here establishes a general protocol for the synthesis of 4,5-bis(trimethylsilyl)-1H-1,2,3-triazoles via thermal Huisgen cycloaddition between azides and bis(trimethylsilyl)acetylene.

A method is described for a mild and efficient synthesis of azulenone skeletons via the addition reactions of 2-phenyl-2-acylketenes with 1-alkynyl ethers. A mechanism is presented to account for both azulenone formation as well as the solvent and substrate dependency of a competitive pyrone formation. The azulenone rings have been subsequently transformed into both substituted azulenes or hydroazulenes by derivatization and/or decarboxylation of an angular carboxyl substituent or by hydrogenation.

A general protocol is reported for the synthesis of the title triazoles (III) via 1,3-dipolar cycloaddition of azides and bis(trimethylsilyl)acetylene.

The acquisition of water and nutrients by plant roots is a fundamental aspect of agriculture and strongly depends on root architecture. Root branching and expansion of the root system is achieved through the development of lateral roots and is to a large extent controlled by the plant hormone auxin. However, the pleiotropic effects of auxin or auxin-like molecules on root systems complicate the study of lateral root development. Here we describe a small-molecule screen in Arabidopsis thaliana that identified naxillin as what is to our knowledge the first non-auxin-like molecule that promotes root branching. By using naxillin as a chemical tool, we identified a new function for root cap-specific conversion of the auxin precursor indole-3-butyric acid into the active auxin indole-3-acetic acid and uncovered the involvement of the root cap in root branching. Delivery of an auxin precursor in peripheral tissues such as the root cap might represent an important mechanism shaping root architecture.

A general strategy for the synthesis of highly substituted polycyclic aromatic and heteroaromatic compounds has been developed. The new aromatic annulation is achieved simply by the irradiation of a dichloroethane solution of an acetylene derivative and a vinyl or aryl α-diazo ketone. Mechanistically, the reaction proceeds via the photochemical Wolff rearrangement of the diazo ketone to generate an aryl- or vinylketene, followed by a cascade of three pericyclic reactions. A variety of substituted phenols, naphthalenes, benzofurans, benzothiophenes, indoles, and carbazoles can be prepared by using the method

Auxins, typified by IAA, are a class of plant hormones involved in a wide array of processes including cell division, cell elongation, tissue patterning, phototropism, gravitropism and root development. Despite recent descriptions of the machinery involved in auxin transport and perception, additional regulatory mechanisms and components remain to be identified and characterized. Chemical genetics has proven to be a valuable means by which to investigate the auxin response pathway in Arabidopsis thaliana. A screen for small molecules that block auxin signaling was performed previously, leading to the characterization of four compounds with this inhibitory activity. Here, we have synthesized various analogs of one of these molecules, compound A, a furyl acrylate ester of a thiadiazole heterocycle. The biological activity of these derivatives was initially assessed based on their ability to inhibit the auxin-inducible expression of the BA3-GUS reporter gene and indicated that the active portion of the molecule was 2-furylacrylic acid (2-FAA). In the micromolar range, 2-FAA attenuates the auxin-inducible expression of IAA5, fails to alter the interaction of IAA7/AXR2 with the SCF TIR1 complex and inhibits both root and hypocotyl elongation of wild-type seedlings. Based on our structure-function analysis of compound A, we conclude that 2-furylacrylic acid is liberated by hydrolysis of an ester linkage. Identification of the cellular target of this molecule will add to our understanding of auxin-mediated events.

Detrifluoroacetylative diazo group transfer: (E)-1-diazo-4-phenyl-3-buten-2-one product: (E)-1-diazo-4-phenyl-3-buten-2-one product: α-diazoacetophenone Keywords: acylation; acylation; condensation, ester-active methylene condensation; deacylation; diazo transfer; acetonitrile; assay methods, for butyllithium, with 2-butanol, menthol, 2-pentanol, or 2-propanol, 1,10-phenanthroline indicator; 1,1,1,3,3,3-hexamethyldisilazane; tetrahydrofuran; triethylamine; acetonitrile; diazo compounds; methanesulfonyl azide, shock sensitive

A modification of the Sonogoshira coupling reaction employing an amidine base and a substoichiometric amount of water generates symmetrical and unsymmetrical bisarylethynylenes in one pot through in situ deprotection of trimethylsilylethynylene-added intermediates.

(I2) [7553-56-2] I2 (MW 253.80) InChI = 1S/I2/c1-2 InChIKey = PNDPGZBMCMUPRI-UHFFFAOYSA-N (AgF) [7775-41-9] AgF (MW 126.87) InChI = 1S/Ag.FH/h;1H/q+1;/p-1 InChIKey = REYHXKZHIMGNSE-UHFFFAOYSA-M (source of electrophilic iodine, I+, in electrophilic aromatic substitution reactions;1 ‘IF’ addition reagent across double bonds;2 mild oxidant which fluoridates selected polycyclic aromatic hydrocarbons via radical cationic intermediates3) Physical Data: AgF: mp 435 °C; bp 1150 °C; d 5.85 g cm−3. Solubility: AgF: sol acetonitrile; sparingly sol aromatic and halogenated solvents. Form Supplied in: AgF: orange and brown chunks. Handling, Storage, and Precautions: AgF: corrosive, harmful dust, hygroscopic, light sensitive. This reagent should be handled in a fume hood.

A general strategy for the synthesis of highly substituted polycyclic aromatic and heteroaromatic compounds has been developed. The new aromatic annulation is achieved simply by the irradiation of a dichloroethane solution of an acetylene derivative and a vinyl or aryl α-diazo ketone. Mechanistically, the reaction proceeds via the photochemical Wolff rearrangement of the diazo ketone to generate an aryl- or vinylketene, followed by a cascade of three pericyclic reactions. A variety of substituted phenols, naphthalenes, benzofurans, benzothiophenes, indoles, and carbazoles can be prepared by using the method

Once faced with structure–reactivity relationships in the context of nucleophilic substitution at sp3 carbon, introductory organic chemistry students must compare and contrast the various attributes and ramifications of SN2 versus SN1 reaction pathways. The dramatic (even melodramatic) way in which some students ask such comparative questions inspired a parody of Hamlet's famous to be or not to be soliloquy. Herein, Hamlet (the son of an organic chemist of Denmark) is the surrogate of any and every student as he uses a thoroughly Shakespearian approach to sorting out some of the key distinguishing features of SN2 versus SN1 reactions.

A procedure for the preparation and purification of 4-nitro-1-pentynylbenzene is reported for use as an introductory organic laboratory exercise. Synthesis of the target compound exemplifies contemporary Pd-mediated cross-coupling methodologies. In this regard, several fundamental mechanistic aspects of catalytic organometallic chemistry are illustrated, including oxidative addition, transmetallation, and reductive elimination. Purification of the target compound via flash column chromatography exposes students to a central technique of modern synthetic methodology. Spectroscopic characterization of the target compound reinforces fundamental skills in 1H NMR, 13C NMR, and IR analysis and interpretation.

A procedure for the preparation and purification of tetrahydro-2-(2-propynyloxy)-2H-pyran is reported for use as an introductory organic laboratory exercise. Synthesis of the target compound illustrates Markownikov Addition and formation of a THP-ether protecting group, produces an acetal functional group, and models a recently developed resin used in combinatorial chemistry. Purification of the target compound via flash column chromatography exposes students to a central technique of modern synthetic methodology. Analysis of the target compound via 1H NMR introduces non-first order coupling (i.e. AB quartet) and long range (i.e. 4-bond) coupling.

A version of the dead‐layer model, originally developed for single crystals, is derived to describe the luminescence behavior of a metallized Zn(Cd)S:Ag phosphor powder. Electron‐hole separation occurs only with excitation events capable of leading to free photoelectrons. The potential for the electrons in the deposited ‘‘metal’’ layer may deviate from the metal work function, when chemical modification, e.g., oxidation, of the metal occurs subsequent to deposition. We call particular attention to the dramatic difference in photoluminescence lifetime in the Zn(Cd)S under laser exposure conditions compared with lower intensity xenon flash exposure. Both this observation and the incomplete quenching are rationalized in terms of a double minimum potential surface for hole trapping at the Ag(I) centers.