Reaction with aryl nitriles

Aryl halides reaction with metal cyanides, often with another transition metal catalyst, to give aryl nitriles (aryl cyanides). Aryl halides react with Zn(CN)2 and a palladium catalyst, for example, to give the aryl nitrile. Similarly, aryl iodides react with CuCN and a palladium catalyst to give the aryl nitrile. Potassium cyanide (KCN) reacts in a similar manner with a palladium catalyst. " Sodium cyanide has been used with a copper catalyst and 20% The reaction of aryl iodides... 

That the reaction occurs as expected between the HOMO of azide (which is, after all, an anion) and the LUMO of the electrophilic nitrile is confirmed by reactions with aryl nitriles ArCN with sodium azide. The yields are all close to quantitative but the reaction is faster when R is an electron-withdrawing group. Not everyone agrees that the reaction is concerted as the approach of the two linear molecules looks very hindered. However, a stepwise addition of azide ion 92 followed by cyclisation 93 looks, if anything, worse as two negatively charged atoms must attack each other in the cyclisation 93. However, this too is pericyclic (electrocyclic) and not ionic. 

One of the features of Diels-Alder reactions with most alkyl and aryl nitriles that has made them rather unattractive as dienophiles is the requirement of very high reaction temperatures Again, only when electron-withdrawing substituents are directly bonded to the nitnle function do [4+2] cycloaddition reactions occur at reasonably low temperatures [ 48, 231, 232] A high yield [4+2] cycloaddition was observed on reaction of 4,4-bis(trifluoromethyl) 1 thia-3-aza-l,3-butadienes with trifluoroacetonitrile at 150 °C [225]... 

A multitude of 1,4-dicarbonyls (1) undergo the Paal-Knorr reaction with and ranging from H to alkyl, aryl, carbonyl, nitrile, and phosphonate, while R and R vary between H, alkyl, aryl, trialkylsilyl, and O-alkyl. Protic acid catalysts are typically used with sulfuric, hydrochloric, and p-toluenesulfonic acids the most popular. Conversion to the furan takes place either at room temperature or upon heating with reaction times varying from five minutes to 24 hours and yields ranging from 17-100%. 

It was found that the reaction of 5-acetoxy- and 5-benzoyloxy-2(5//)-furanones 174 with aryl nitrile oxides afforded only one cycloadduct, the condensed isox-azoline 233 (88TL5317). In principle, there are four possible cycloadducts 233 and 234 resulting from the anti approach of the 1,3-dipolarophile to the acetoxy group (with exo configuration of the acetoxy substituent), and two further isomers... 

The reaction between aryl halides and cuprous cyanide is called the Rosenmund-von Braun reactionP Reactivity is in the order I > Br > Cl > F, indicating that the SnAt mechanism does not apply.Other cyanides (e.g., KCN and NaCN), do not react with aryl halides, even activated ones. However, alkali cyanides do convert aryl halides to nitrilesin dipolar aprotic solvents in the presence of Pd(II) salts or copper or nickel complexes. A nickel complex also catalyzes the reaction between aryl triflates and KCN to give aryl nitriles. Aromatic ethers ArOR have been photochemically converted to ArCN. 

A related reaction involves oe-substituted aryl nitriles having a sufficiently acidic a hydrogen, which can be converted to ketones by oxidation with air under phase-... 

Thallium(III), particularly as the trifluoroacetate salt, is also a reactive electrophilic metallating species, and a variety of synthetic schemes based on arylthallium intermediates have been devised.75 Arylthallium compounds are converted to chlorides or bromides by reaction with the appropriate cupric halide.76 Reaction with potassium iodide gives aryl iodides.77 Fluorides are prepared by successive treatment with potassium fluoride and boron trifluoride.78 Procedures for converting arylthallium compounds to nitriles and phenols have also been described.79... 

As noted in Section 11.2.2, nucleophilic substitution of aromatic halides lacking activating substituents is generally difficult. It has been known for a long time that the nucleophilic substitution of aromatic halides can be catalyzed by the presence of copper metal or copper salts.137 Synthetic procedures based on this observation are used to prepare aryl nitriles by reaction of aryl bromides with Cu(I)CN. The reactions are usually carried out at elevated temperature in DMF or a similar solvent. 

Application of the Ritter reaction conditions on y-hydroxy-a,P-alkynoic esters, 102, produced ethyl 5-oxazoleacetates 103 or y-A-acylamino-P-keto ester 104 by reaction with aryl or alkyl nitriles respectively. The y-A-acylamino-P-keto ester 104 can also be transformed into oxazole derivatives using an additional step involving POCI3 <06TL4385>. 

Aryl and vinyl nitriles have been prepared very efficiently from the corresponding bromides by palladium-catalyzed reactions under microwaves. This energy source has been employed for the conversion of these nitriles into aryl and vinyl tetrazoles by cycloaddition reactions with sodium azide (Scheme 9.66). The direct transformation of aryl halides to the aryl tetrazoles in a one pot procedure could be accomplished both in solution and on a solid support [115], The reactions were complete in a few minutes, a reaction time considerably shorter than those previously reported for the thermal reactions. The cydoadditions were performed with sodium azide and ammonium chloride in DMF and, although no explosion occurred in the development of this work, the authors point out the necessity of taking adequate precautions against this eventuality. 

Some features are characteristic of reactions of nitrile oxides with 2,4,6-cyclo-hep tatrien-l-imines (8-azaheptafulvenes). 1,3-Dipolar cycloaddition to the C=N double bond of N-aryl-2,4,6-cycloheptatrien-l-imines 142 (R = Ar), affording... 

Syntheses of l-aryl-3,3,3-trilluoro-l-propynes and their reactions with nitrile oxides to give 3,5-diaryl-4-tri(luoromethylisoxazoles have been carried out. In particular, l-(4-chlorophenyl)-3,3,3-trilluoro-l-propyne, on reaction with 4-chlorobenzohydroximoyl chloride in the presence of Et3N in PhMe, give a 45% mixture of 211 (R = R1 = 4-CIC6H4) and the regioisomer 212 in the ratio of 97 3, respectively (370). 

The carbon-nitrogen triple bond of aryl thiocyanates acts as a dipolarophile in 1,3-dipolar cycloadditions. Reactions with nitrile oxides yield 5-arylthio-1,2,4-oxadiazoles 227 (X = O Y = S). Aryl selenocyanates behave similarly forming 5-arylseleno-l,2,4-oxadiazoles 227 (X = 0 Y = Se). Reactions of 5-aryl-... 

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