Aryls cyanides

Aromatic nitriles (or aryl cyanides) can be obtained by methods (1) and (3). but not by method (2). In addition, aromatic nitriles can be prepared by two other methods, (a) from the corresponding diazo compound by Sandmeyer s Reaction (p. 189), (b) by fusing the corresponding sulphonic acid (or its salts)... 

R—N=N Aryl diazonium 10ns are formed by treatment of primary aromatic amines with nitrous acid They are ex tremely useful in the preparation of aryl halides phenols and aryl cyanides... 

Nitrile (Section 20 1) A compound of the type RC=N R may be alkyl or aryl Also known as alkyl or aryl cyanides... 

Sandmeyer reaction (Section 22 17) Reaction of an aryl dia zonium ion with CuCl CuBr or CuCN to give respec tively an aryl chloride aryl bromide or aryl cyanide (nitrile)... 

Dehalogenation of monochlorotoluenes can be readily effected with hydrogen and noble metal catalysts (34). Conversion of -chlorotoluene to Ncyanotoluene is accompHshed by reaction with tetraethyl ammonium cyanide and zero-valent Group (VIII) metal complexes, such as those of nickel or palladium (35). The reaction proceeds by initial oxidative addition of the aryl haHde to the zerovalent metal complex, followed by attack of cyanide ion on the metal and reductive elimination of the aryl cyanide. Methylstyrene is prepared from -chlorotoluene by a vinylation reaction using ethylene as the reagent and a catalyst derived from zinc, a triarylphosphine, and a nickel salt (36). 

The mechanism of action of the cyanation reaction is considered to progress as follows an oxidative addition reaction occurs between the aryl halide and a palladium(O) species to form an arylpalladium halide complex which then undergoes a ligand exchange reaction with CuCN thus transforming to an arylpalladium cyanide. Reductive elimination of the arylpalladium cyanide then gives the aryl cyanide. 

The synthesis of (hetero)aryl cyanides from (hetero)aryl halides via transition-metal catalysis is a very valuable reaction since a nitrile can be easily transformed into several other functional groups. Not until 2000 were the first examples on microwave-assisted cyanation reported in the literature. Alter-man and Hallberg found that 3-bromopyridine and 3-bromothiophene were... 

The reactions of tetraorganotins with ICl, EBr, and CICN have been investigated as synthetic routes to aryl cyanides (111) and alkyltin bromides and chlorides (112,113). 

Mercuration of aromatic compounds can be accomplished with mercuric salts, most often Hg(OAc)2 ° to give ArHgOAc. This is ordinary electrophilic aromatic substitution and takes place by the arenium ion mechanism (p. 675). ° Aromatic compounds can also be converted to arylthallium bis(trifluoroacetates), ArTl(OOCCF3)2, by treatment with thallium(III) trifluoroacetate in trifluoroace-tic acid. ° These arylthallium compounds can be converted to phenols, aryl iodides or fluorides (12-28), aryl cyanides (12-31), aryl nitro compounds, or aryl esters (12-30). The mechanism of thallation appears to be complex, with electrophilic and electron-transfer mechanisms both taking place. 

Wilkinson s catalyst has also been reported to decarbonylate aromatic acyl halides at 180°C (ArCOX ArX). This reaction has been carried out with acyl iodides, bromides, and chlorides. Aliphatic acyl halides that lack an a hydrogen also give this reaction, but if an a hydrogen is present, elimination takes place instead (17-16). Aromatic acyl cyanides give aryl cyanides (ArCOCN—> ArCN). Aromatic acyl chlorides and cyanides can also be decarbonylated with palladium catalysts. °... 

Reaction of 1-tetralone with aryl cyanides or methyl thiocyanate, followed by aromatisation with DDQ gave good yields of benzoquinazolines. The further transformation of the methylthio product 31, via oxidation and selective sequential nucleophilic substitution of the resulting sulfones, illustrates the utility of this substituent. 2-Tetralone reacted similarly but substantial amounts of by-products were formed <06T2799>. 

Other approaches to tetrazoles were also recently published. Primary and secondary amines 195 were reacted with isothiocyanates to afford thioureas 196, which underwent mercury(II)-promoted attack of azide anion, to provide 5-aminotetrazoles 197 . A modified Ugi reaction of substituted methylisocyanoacetates 198, ketones, primary amines, and trimethylsilyldiazomethane afforded the one-pot solution phase preparation of fused tetrazole-ketopiperazines 200 via intermediate 199 <00TL8729>. Microwave-assisted preparation of aryl cyanides, prepared from aryl bromides 201, with sodium azide afforded aryl tetrazoles 202 . 

Di-2-pyridyl sulphite (343) (from 2-pyridone and thionyl chloride in the presence of triethylamine) transforms primary aliphatic and aromatic amines RNH2 into N-sulphinylamines RN=S=0 and it dehydrates amides ArCONH2 to aryl cyanides, aldehyde oximes RCH=NOH (R = Cxlf 7. 4-MeOCgH4 or PhCH=CH) to the cyanides RCN and A-alkyl- and TV-ary Iformamides RNHCHO to isocyanides RNC. Aliphatic and aromatic... 

Addition of a suspected intermediate. If a certain intermediate is suspected, and if it can be obtained by other means, then under the same reaction conditions it should give the same products. This kind of experiment can provide conclusive negative evidence if the correct products are not obtained, the suspected compound is not an intermediate. However, if the correct products are obtained, this is not conclusive since they may arise by coincidence. The von Richter reaction (3-25) provides us with a good example here too. For many years it had been assumed that an aryl cyanide was an intermediate, since cyanides are easily hydrolyzed to carboxylic acids (6-5). In fact, in 1954, p-chlorobenzonitrile was shown to give p-chlorobenzoic acid under normal von Richter conditions.29 However, when the experiment was repeated with 1-cyanonaphthalene, no 1-naphthoic acid was obtained, although... 

Aryl-l, 2,4-triazolo[l, 5-a]pyrimidines (17) were prepared by oxidative cyclization, by the action of lead tetraacetate (LTA), of 2-pyrimidylary-lamidines (16), first prepared by the reaction of 2-aminopyrimidines (15) with aryl cyanides in the presence of A1C13 (90SC2617) (Scheme 6). 

Table 14 Formation of Symmetrical 1,3,5-Triazines (RCN)3 by Cyclotrimerization of Alkyl and Aryl Cyanides...

Phenylsodium is formed initially in the reaction between benzonitrile and sodium (Scheme 79) (59JOC208). Trimerizations of aryl or heterocyclic nitriles catalyzed by amines or alkoxides resemble the reactions of the perfluoronitriles described above (Schemes 77 and 78 respectively). Kurabayashi et al. (71BCJ3413) studied the trimerization of benzonitrile under pressure in methanol, and have shown that the rate determining step is the reaction of the benzimino ether with benzonitrile. Steric factors exert an important influence in the trimerizations of aryl cyanides. The cyclizations of ort/zo-substituted aryl cyanides need more severe conditions than either the corresponding meta or para derivatives (Table 14). 

Aryl cyanides react with the anion of urea (or thiourea) to give the 2,4-diaryl-l,3,5-triazinone (164) in good to excellent yields except when o-chloroaryl isocyanates are used (76JHC917). 

Diaryl-l,2,3,5-oxathiadiazine 2,2-dioxides (187) are valuable starting reagents which are readily prepared by treatment of the aryl cyanide with sulfur trioxide. Amidines, imidates and trichloroacetonitrile react with (187) to give a wide range of 4,6-diaryl-l,3 5-triazines in 50-90% yields under acidic conditions (equation 108) (63CB2070). 

Photolysis of thiatriazoles was first described by Kirmse,25 who found that aryl cyanides, aryl isothiocyanates, and sulfur are formed on irradition of 5-arylthiatriazoles with UV light. Recently Okazaki et al.n reported the formation of sulfur atoms on irradiation of thiatriazoles. Photolysis of 5-phenylthiatriazole (A lax= 280 nm, e — 10800)25 in the presence of cyclohexene yielded cyclohexene episulfide. Cyclohexene thiols were not formed this was taken as an indication that the reactive species is a triplet sulfur atom. Tetramethylethylene behaves similarly.22... 

Cuprous Cyanide, Cu-(CN), while monnclinic crystals, insoluble in H 0, soluble in HCI. NHjOH. and potassium cyanide. Used in Sandmeyer s reaction to synthesize aryl cyanides. 

Aryl cyanides add to norbornene and norbornadiene under nickel catalysis to give (2/U,35 )-3-aryl-2-cyanobicyclo[2.2.11heptanes and (2/U,3.S )-3-aryl-2-cyanobicy-clo[2.2.1]hept-5-enes in good yields with a broad substrate scope. On the other hand, the reaction of an aryl cyanide with triethoxy(vinyl)silane gives a Heck-type arylation product, suggesting the arylnickelation pathway in the catalytic cycle.68... 

Aryl crown ethers, in hexaruthenium carbido clusters, 6, 1008 Aryl cyanides, with Ni(0) complexes, 8, 47 Aryldiazoalkanes, with bis-Gp Ti, 4, 580-581 a-Arylenamides, asymmetric hydrogenation, 10, 28 Arylenes, with platinum(II), 8, 491 Aryl ethers, via cross-coupling with copper, 10, 650 with palladium, 10, 654 Aryl fluorides... 

Me3SiCN is a convenient, reactive cyanide donor in transition metal-catalyzed processes. The Pd-catalyzed reaction of aryl iodides with Me3SiCN is useful for the synthesis of aryl cyanides.257 Me3SiCN works also as an effective co-catalyst for the Pd-catalyzed cyanation of aryl iodides with KCN.258 Allylic acetates, carbonates, and the related compounds undergo the Pd-catalyzed cyanation with Me3SiCN.259-261 The tandem cyclization-cyanation reaction of 2-bromo-l,6-heptadienes with Me3SiCN proceeds under catalysis by an Ni complex (Equation (68)).262... 

Diaryl tellurium dichlorides, obtainable from aromatic compounds and tellurium tetrachloride, react with excess bromine or iodine in refluxing DMF or acetonitrile in the presence of a metal fluoride to give aryl halides in low yields. The reactions with chlorinating agents are very sluggish. The reaction of bromine and bis[4-methoxyphenyl] tellurium dichloride formed 2,4-dibromomethoxybenzene in 76% yield. Reactions of these tellurium dichlorides with copper(I) cyanide in DMF produced aryl cyanides in yields of less than 8%3. 

Replacement of the Diazonium Group by Chloride, Bromide, and Cyanide The Sandmeyer Reaction Copper salts (cuprous salts) have a special affinity for diazonium salts. Cuprous chloride, cuprous bromide, and cuprous cyanide react with arenediazonium salts to give aryl chlorides, aryl bromides, and aryl cyanides. The use of cuprous salts to replace arenediazonium groups is called the Sandmeyer reaction. The Sandmeyer reaction (using cuprous cyanide) is also an excellent method for attaching another carbon substituent to an aromatic ring. 

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