Aromatic nitriles table

The physical properties of some typical aromatic nitriles are collected in Table IV, 195. 

Table 6. Catalytic hydrosilylation of aromatic nitriles promoted by catalyst B and catalyst C .

Microwave irradiation of a reaction mixture containing aromatic nitriles, hydrazine hydrate, hydrazine dihydrochloride, and ethylene glycol as solvent in a one-pot process gave 3,5-disubstituted 4-amino-l,2,4-triazoles 98a-i in excellent yields (Equation 35 and Table 14) <2000TL1539>. 

A common and effective direct approach to unsubstituted or multiply substituted oxazolines is the Lewis acid catalyzed reaction of nitriles with amino alcohols in an alcoholic or aromatic solvent (chlorobenzene) at reflux. The most common Lewis acids employed include ZnCl2, ZnBr2, NiBr2, CuCl2, and kaolinitic clay. Microwave irradiation has also been reported to facilitate the transformation. Alternatively, the condensation can be carried out in the presence of catalytic amounts of potassium carbonate. The method works well for both aliphatic and aromatic nitriles, with retention of stereochemistry. Some representative examples from the recent literature are listed in Table 8.16 (Scheme 3 40),2 35.2oi-2i3... 

Aliphatic and aromatic nitriles are often converted to the corresponding imidates that then react with amino alcohols to provide oxazolines. This two-step process offers milder conditions. Generally, a mixture of the imidate (free base or hydrochloride) is allowed to react with the amino alcohol in a solvent (alcohols, CH2CI2, CHCI3) with or without a tertiary base. As expected, the cylization proceeds with retention of stereochemistry when chiral amino alcohols are used. Representative examples are shown in Table g 17 33,62,63,139,216-225 ready availability of benzimidates and trimethyl orthobenzoates make them ideal surrogates for benzonitrile. ... 

Physical data for aliphatic and aromatic nitriles are collected in Tables 10.30 and 10.31 respectively. 

Table 3.4 Transition temperatures (°C) and dielectric anisotropy for the aromatic nitriles (28-40)...

The Stephen reduction has been applied to a variety of nitriles, but is genuinely useful only for aromatic substrates. Table 11 gives a number of representative examples, and more are available elsewhere. The failure with o-toluonitrile is untypical, and was attributed to steric hindrance. A variant employing tin(II) bromide was successful in synthesizing cinnamaldehyde and its vinylog (45) in 65% and 50% yields, respectively. ... 

Table 11 Yields of Aldehydes Prepared by the Stephen Reduction of Aromatic Nitriles ...

The ability of boranes to coordinate and activate an incoming substrate was also proposed recently by Lu and Williams.The di(pyrazolyl)borohydride was first coordinated to mthenium. Chloride abstraction in acetonitrile then afforded the imido complex 46c as a result of intramolecular hydroborafion of the CN triple bond (Scheme 15). The process is amenable to catalysis using excess of NaBH and 1 equiv. of NaOfBu (Table 1). A broad variety of electron-poor and electron rich-aromatic nitriles were thereby reduced into primary amines using 5 mol% of 46c. With electron-rich heterocycles, hydration instead of hydrogenation is observed and amides are obtained. 

The key to the success of this process is a combination of specific catalysts and optimum reaction conditions. Effective catalysts for trimerization of aromatic nitriles are listed in Table I (4 ). Optimum reaction conditions for processing the aromatic nitrile-modified imide precursors depend on the chemical structure and characteristic property of the individual precursor of concern. In general, yield of the polymeric products increases with the increase of reaction temperature, pressure, time, and concentration of catalyst within the range of practical experimental limits (5 ). 

Table I. EFFECTIVE CATALYSTS FOR TRIMERIZING AROMATIC NITRILES CATALYST FORMULA...

Aromatic nitriles are strong oxidants in their excited states (see Table I). Since they fluoresce strongly, the involvement of the singlet states can be easily proved by application of fluorescence quenching techniques. In all of the tested cases, it has been found that the Stern Volmer constant obtained from fluorescence analysis and that obtained from the double reciprocal plots of reaction quantum yield vs. quencher concentration are nearly equal, thus proving that the singlet stale is actually involved In the photochemical reaction. Actually it has been observed that a AG < 0 and polar solvents are necessary (although not sufficient, see Section 3) conditions for the photochemical proc-... 

Results of preparative nitration arenes, haloarenes, and nitroarenes are summarized in Tables XV XVII. Since HF and BF3 are the only by-products of the reaction, nitration with nitronium salts can be carried out under anhydrous conditions. This is advantageous in nitration of aromatics containing functional groups sensitive to hydrolysis. Thus aromatic nitriles, acid halides, and esters can be nitrated in high yield without difficulty (Tables XVIII-XIX). 

Estimation methods for the hydrolysis rates of several types of carboxylic acid esters, carbamates, aromatic nitriles and phosphoric acid esters have been reported. Hydrolysis rates are subject to substituent effects, and consequently linear free-energy relationships (LFERs), as represented by Hammett or Taft correlations, have hence been applied to their estimations. Reviews (e.g. Harris, 1990 Peijnenburg, 1991) reveal that QSARs are available for only a few compound classes (Table 4.8) and are mostly based on limited sets of experimental data. 

The agent K 9-sec-Am-BBNH reduces aromatic nitriles to the corresponding aldehydes in excellent yields [16]. The reagent tolerates some of the functional groups as p-carboxybenzonitrile is reduced to p-carboxybenzaldehyde in almost quantitative yield (Table 7.6) [16]. 

Table 7.6 Yields of aldehydes in the reduction of representative aromatic nitriles with potassium-9-sec-amyl-9-boratabicyclo[3.3.1]nonane in tetrahydrofuran at room temperature [16]...

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