Nomenclature des dérivés benzéniques

La nomenclature des dérivés benzéniques est la partie de nomenclature IUPAC en chimie organique permettant de désigner la position des substituants autres que l'hydrogène sur un hydrocarbure aromatique. ortho, méta, para Les préfixes grecs ortho (ὀρθός = "droit", "juste"), méta (μετά = "après", "au-delà") et para (παρά = "à côté", "malgré", "contre") désignent la position des substituants secondaires par rapport au substituant principal dans un cycle benzénique polysubstitué. En nomenclature IUPAC, on donne au substituant principal la position « 1 » sur le cycle (R sur le schéma ci-contre).

Un substituant secondaire en position ortho sera sur l'atome immédiatement voisin de ce dernier, c'est-à-dire en position « 2 ». L'isomère ortho est donc l'isomère 1,2.
Un substituant secondaire en position méta sera sur l'atome d'après, c'est-à-dire en position « 3 ». L'isomère méta est donc l'isomère 1,3.
Un substituant secondaire en position para sera sur l'atome opposé su

Catalytic Friedel-Crafts Reaction of Aminocyclopropanes

Florian Patrick Marie Daniel De la Barre De Nanteuil, Joachim Loup, Jérôme Waser

A Lewis acid catalyzed Friedel-Crafts reaction between donor-acceptor aminocyclopropanes and indoles and other electron-rich aromatic compounds is reported. Indole alkylation at the C3 position was generally obtained for a broad range of functional groups and substitution patterns. In the case of C3-substituted indoles, C2 alkylation was observed. The reaction gives a rapid access to gamma amino acid derivatives present in numerous bioactive molecules.

American Chemical Society2013

In vitro and in vivo photocytotoxicity of boron dipyrromethene derivatives for photodynamic therapy

Siang Hui Lim, Patrycja Nowak-Sliwinska, Hubert van den Bergh, Georges Wagnières

To understand the effects of substitution patterns on photosensitizing the ability of boron dipyrromethene (BODIPY), two structural variations that either investigate the effectiveness of various iodinated derivatives to maximize the "heavy atom effect" or focus on the effect of extended conjugation at the 4-pyrrolic position to red-shift their activation wavelengths were investigated. Compounds with conjugation at the 4-pyrrolic position were less photocytotoxic than the parent unconjugated compound, while those with an iodinated BODIPY core presented better photocytotoxicity than compounds with iodoaryl groups at the meso-positions. The potency of the derivatives generally correlated well with their singlet oxygen generation level. Further studies of compound 5 on HSC-2 cells showed almost exclusive localization to mitochondria, induction of G(2)/M-phase cell cycle block, and onset of apoptosis. Compound 5 also extensively occluded the vasculature of the chick chorioallantoic membrane. Iodinated BODIPY structures such as compound 5 may have potential as new photodynamic therapy agents for cancer.

American Chemical Society2010

Selective three-phase hydrogenation of aromatic nitro-compounds over beta-molybdenum nitride

Fernando Cardenas Lizana, Lioubov Kiwi, Daniel André Samuel Lamey

A tetragonal molybdenum nitride (beta-Mo2N) has been prepared by temperature programmed treatment of MoO3 in flowing N-2 + H-2 and for the first time shown to catalyze the liquid phase selective hydrogenation (T = 423 K; P-H2 = 11 bar) of a series of para-substituted (-H, -OH, -O-CH3, -CH3, -Cl, -I and -NO2) nitrobenzenes to give the corresponding aromatic amine. Reaction over Pd/Al2O3, as a benchmark catalyst (Pd particle size ca. 18 nm), resulted in a composite hydrodechlorination/hydrogenation of p-chloronitrobenzene (as a representative nitroarene) to generate nitrobenzene and aniline. beta-Mo2N has been characterized in terms of temperature-programmed reduction (TPR), H-2 chemisorption/temperature programmed desorption (TPD), BET surface area/pore volume, elemental analysis, powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning (SEM) and transmission (TEM) electronic microscopy. Elemental analysis, XRD, SEM and TEM have confirmed the formation of tetragonal beta-Mo2N, characterized by an agglomeration of flake-like crystallites. Post-synthesis, the nitride was passivated by contact with 1% (v/v) O-2/He at ambient temperature and XPS analysis has demonstrated the formation of a superficial passivating oxide overlayer without bulk oxidation. Pre-reaction, activation by TPR to 673 K was necessary to remove the passivating film. Hydrogen TPD has revealed significant hydrogen uptake (0.7 mu mol m(-2)) associated with beta-Mo2N. Nitro group reduction kinetics have been subjected to a Hammett treatment where the reaction constant (p = 0 4) is diagnostic of an increase in rate due to the presence of electron-withdrawing substituents on the aromatic ring, consistent with a nucleophilic mechanism. The results presented in this study establish the viability of beta-Mo2N to promote selective nitroarene hydrogenation. (C) 2011 Elsevier B.V. All rights reserved.

2011

Selective three-phase hydrogenation of aromatic nitro-compounds over beta-molybdenum nitride

Fernando Cardenas Lizana, Lioubov Kiwi, Daniel André Samuel Lamey

2011