Search results for "Pyrrole"

Electrochemical oxidation of 2,4,5-triaryl-substituted pyrroles.II. Oxidative dimerization of 4,5-diphenyl-2-mesitylylpyrrole

1989

2,4,5-Triaryl-substituted pyrroles lead, upon chemical or electrochemical oxidation, to an intermediate β-β'-dimer, which, in the course of the reaction, undergoes further oxidation to a tetracyclic derivative. To improve the selectivity towards the uncyclized dimer the oxidation of a triarylpyrrole in which the ortho positions of the phenyl group in position 2 are hindered by the presence of methyl groups was attempted. The cyclization was hindered, but an α-β'-dimer was obtained as the major product. An unexspected isomeric α-β'-dimer, in which the mesitylyl group is shifted into the β position of the pyrrole ring which undergoes the oxidation, was obtained in minor amounts. Electroanalyt…

ChemInform Abstract: Palladium-Polypyrrole Nanocomposites Pd@PPy for Direct C-H Functionalization of Pyrroles and Imidazoles with Bromoarenes.

2016

Palladium–polypyrrole nanocomposites (Pd@PPy) with unique combination of high palladium dispersion (nanoparticle size 2.4 nm) and high palladium content (35 wt%) are efficient catalysts for the selective arylation of substituted pyrroles and imidazoles with either activated or deactivated aryl bromides. The performances of the recoverable supported palladium catalyst matches the best performances of homogeneous systems based on Pd(OAc)2 at 0.5–0.2 mol%, and largely overwhelm the classical Pd/C catalyst.

Self-Assembly of M24L48 Polyhedra Based on Empirical Prediction

2012

Cycloadditions in the pyrrole series

1972

3-(1H-Indol-3-yl)-4-(3,4,5-trimethoxyphenyl)-2,5-dihydro-1H-pyrrole-2,5-dione

2005

The crystal structure of the title compound, C21H18N2O5, was determined in order to study the electrocyclic reactivity of 3,4-di­aryl-1H-pyrrole-2,5-dione derivatives. Intermolecular hydrogen bonds form sheets.

ChemInform Abstract: A New Tandem Cross Metathesis-Intramolecular Aza-Michael Reaction for the Synthesis of α,α-Difluorinated Lactams.

2012

Difluorinated amides are treated with methyl vinyl ketone or analogous esters to produce the desired γ- and δ-lactam units including optically active versions.

ChemInform Abstract: First Reactions of Dialkoxycarbenium Tetrafluoroborates with Pyrroles, 5H-Dibenz(b,f)azepines, and Electron-Rich Arenes.

1990

Pyrrole (2a) and 2,5-dimethylpyrrole (2b) react with the dialkoxycarbenium tetrafluoroborates 1a-1c under kinetic control to yield the corresponding acylpyrrole derivatives. 5H-Dibenz[b,f]azepine (9a) and the 10,11-dihydro derivative 9b react only with the most electrophilic of the series of electrophiles tested, namely, diethoxycarbenium tetrafluoroborate (1a), to furnish the corresponding formyl derivatives. Similarly, in arene chemistry, the highly electron-rich N,N-dimethylaniline (13a) and 1,3,5-trimethoxybenzene (13b) are formylated by reaction with 1a.

ChemInform Abstract: Enantioselective Zirconium-Catalyzed Friedel-Crafts Alkylation of Pyrrole with Trifluoromethyl Ketones.

2009

The first catalytic enantioselective Friedel−Crafts alkylation of pyrrole with 2,2,2-trifluoroacetophenones to give pyrroles with a trifluoromethyl-substituted tertiary alcohol moiety bearing a quaternary stereogenic center is described. The reaction is achieved in the presence of a 3,3′-dibromo-BINOL-Zr(IV) complex to give the expected products with high yields (up to 98%) and good enantioselectivities (up to 93% ee). The absolute stereochemistry of the products has been determined by chemical correlation.

ChemInform Abstract: A Versatile Palladium/Triphosphane System for Direct Arylation of Heteroarenes with Chloroarenes at Low Catalyst Loading.

2010

The present new catalyst system can be used for the direct arylation of various heteroaromatic compounds at low palladium loadings.

Why Do Five-Membered Heterocyclic Compounds Sometimes Not Participate in Polar Diels–Alder Reactions?

2013

The reactions of bicyclic enone (BCE, 1) with cyclopentadiene (Cp, 2) and the five-membered heterocyclic compounds (FHCs) furan 3 and N-methyl pyrrole 4 for the construction of polycyclic heterocyclic compounds have been studied at the B3LYP/6-31G* level. No reaction takes place in the absence of Lewis acid (LA) catalysts as a consequence of the high activation energy associated with these reactions. Electrophilic activation of BCE 1 by formation of a complex with the BF3 LA, 1-BF3, and solvent effects favor the reactions. However, a different reactivity is manifested by Cp 2 and FHCs 3 and 4. Thus, while the reaction of 1-BF3 with Cp 2 yields the expected exo [4 + 2] cycloadduct, the react…