Nickel cyanates

It can also be prepared by passing carbon monoxide through alkahne suspensions of nickel sulphide or nickel cyanate. 

In the presence of a trace of iron or nickel oxide, rapid oxidation occurs when cyanide is heated in air, first to cyanate and then to carbonate ... 

This is a problem that has been reported by several researchers in other cya-nation methods on heteroaromatic halides. (Hetero)aryl chlorides have also been tackled via in situ halogen exchange to (hetero)aryl bromides followed by sequential cyanation (Scheme 71). For this microwave-assisted process an equimolar amount of NiBr2 and a two-fold excess of NaCN were used. The only heteroaromatic chloride tested was 2-chloropyridine. Although the procedures described involve the use of significant amounts of nickel salts, a clear advantage is that the reactions can be performed in air. Moreover, the cyanat-ing reagents are easily removed since they are water soluble. 

Vinylic copper reagents react with CICN to give vinyl cyanides, though BrCN and ICN give the vinylic halide instead." Vinylic cyanides have also been prepared by the reaction between vinylic lithium compounds and phenyl cyanate PhOCN." Alkyl cyanides (RCN) have been prepared, in varying yields, by treatment of sodium trialkylcyanoborates with NaCN and lead tetraacetate." Vinyl bromides reacted with KCN, in the presence of a nickel complex and zinc metal to give the vinyl nitrile. Vinyl triflates react with LiCN, in the presence of a palladium catalyst, to give the vinyl nitrile." ... 

Nickel-catalyzed carbonylation of a-ketoalkynes has also been reported by Arzoumanian et al. under phase-transfer conditions.94 The carbonylation gave either furanone or unsaturated carboxylic acids depending on the substituents of substrates (Eq. 4.53). A similar reaction, nickel-catalyzed cyanation of a-ketoalkynes with KCN in water, was also reported to afford unsaturated hydroxylactams (Eq. 4.54).95... 

Later, a nickel-catalyzed cascade conversion of propargyl halides and propargyl alcohol into a pyrone in water was reported. The reaction involved a carbonylation by CO and a cyanation by KCN (Eq. 4.55).96 Recently, Gabriele et al. explored a facile synthesis of maleic acids by palladium catalyzed-oxidative carbonylation of terminal alkynes in aqueous DME (1,2-dimethoxyethane) (Eq. 4.56).97... 

Another interesting cyanation reaction, also brought about by nickel(0)... 

NO, Nitrosyls, molybdenum and tungsten, 26 132, 133 NOC, Cyanate tungsten complex, 26 42 NOC4H7, 3-Butenamide nickel complex, 26 206 NOC4H , 2-Propenamide, 2-methyl-nickel complex, 26 205 NOC H, Benzoyl isocyanide chromium complex, 26 32, 34, 35 N04ReC16H, Perrhenate, tetrabutylam-monium, 26 391... 

Table 57 Selected Nickel(II) Complexes with Cyanate, Isothiocyanate and Isoselenocyanate Anions...

The nickel-catalyzed transformation of aromatic halides into the corresponding nitriles by reaction with cyanide ions is reported. Both tris(triarylphosphine)nickel(0) complexes and tY2ins-chloro( aryl )bis( triarylphosphine )nickel(II) complexes catalyze the reaction. The influence of solvents, organophos-phines, and substituents on the aromatic nucleus on catalytic cyanation is studied. A mechanism of the catalytic process is suggested based on the study of stoichiometric cyanation of ti3ins-chloro(aryl)bis(triphenylphosphine)nickel-(II) complexes with NaCN and the oxidative addition reaction of Ni[P(C6H5)3]s with substituted aryl halides. 

Cyanation of 1-Chloronaphthalene in the Presence of Tris(tri-phenylphosphine) nickel. 1-Chloronaphthalene (3.6 grams, 22.3 mmole), Ni[P(C6H5)3]3 (0.75 gram, 0.89 mmole), and ethanol (40 ml) were stirred and warmed up to 60°C. NaCN (1.1 grams, 22.3 mmole) was added, and the mixture was stirred for 3 hrs at 60 °C. The reaction mixture was partitioned between water and diethyl ether. The ether extract contained 1-cyanonaphthalene (3.06 grams, 90% ). The yield was determined by GLC with acetophenone as internal standard. 

Catalyst of the Cyanation Reaction. The reaction was studied in the presence of Ni(0) complexes or aryl(chloro)nickel complexes. For a clearer interpretation the corresponding results are considered separately. A variant of the process consisting in the use of acetone cyanohydrin as source of cyanide ions is also reported. 

Table I. Cyanation of l-Chloronaphthalene° Catalyzed by Nickel(0) Complexes in Ethanol6 at 60°C...

Cyanation Catalyzed by Nickel(O) Complexes. Results of cyanation of 1-chloronaphthalene with NaCN in ethanol using various nickel(O) complexes as catalysts are shown in Table I. 

Tris (triphenylphosphine) nickel, tris (tri-p-tolylphosphine) nickel, and bis (1,3-diphenylphosphinepropane) nickel proved to be good catalysts, the first being slightly more effective. The tricyclohexylphosphine complex was a very poor catalyst, and bis (cyclooctadiene) nickel did not catalyze cyanation. Cyanation of several substituted aromatic halides in the presence of Ni[P(C6H5)3]3 prepared by reducing dichlorobis (triphenylphosphine) nickel (II) 2 with a powdered manganese iron (80 20) alloy (Reaction 3) is reported in Table II. 

Table II. Cyanation of Aromatic Halides in the Presence of a Catalyst Prepared in situ from Nickel(II) Salt6 and Manganese—Iron Alloy...

Cyanation Catalyzed by trans-CHLORO ( aryl ) bis ( triphenylphos-phine) nickel (II) Complexes. In Table III cyanation of aryl halides catalyzed by the Ni(II) complexes obtained by reaction between aryl halides and Ni[P(C6H5)3]3 (Reaction 2) is shown. In general the trans-chloro (1-naphthyl) bis (triphenylphosphine) nickel (II) complex was used. Ortho substituted aryl halides were allowed to react in dimethylformamide... 

The reactions were carried out by using trans-chloro( 1-naphthyl)-bis(triphenylphosphine)nickel(II) (l, Ar = Ci0H7) complex as catalyst in the presence of various phosphorus ligands. We observed that aromatic phosphines in arylnickel(II) complexes 1 are easily replaced by aliphatic phosphines. In fact in the presence of alkylphosphines, such as P( C6Hn )3 and P(C4H9)3, cyanation did not occur. Moreover phosphites such as... 

Stoichiometric Cyanation Reaction. To elucidate the mechanism, the stoichiometric cyanation reaction of tram-chloro (aryl) bis (triphenylphos-phine) nickel (II) complexes 1 was studied. Arylnickel (II) complexes... 

Table IX. Cyanation of trans-Chloro(aryl)bis(triphenylphosphine)-nickel(II) Complexes, IR Absorptions...

Therefore it seems reasonable to assume that cyanation of aryl halides involves two fundamental processes oxidative addition of the tris(triphenylphosphine)nickel complex on the aromatic halide (Reaction 2) and cyanation of the arylnickel(II) complex 1 (Reaction 8). A further proof of the validity of this scheme is that both Ni[P(C6H5)3]3 and arylnickel (II) complexes 1 have an equal catalytic activity, these latter being intermediates of the catalytic process. Recent studies (22) on the influence of substituents on the aromatic halide in the oxidative addition reaction with Ni[P(C6H5)3]3 have given the results shown in Figure 4. 

Sodium cyanide solution dissolves certain metals (I) with absorption of oxygen, e.g.. gold, silver, mercury, lead, and (2) with evolution of hydrogen, e.g.. copper, nickel, iron. zinc, aluminum, magnesium and solid sodium cyanide, when heated with certain oxides, e.g.. lead monoxide PhO. stannic oxide SnO.. yields the metal of the oxide, e.g.. lead. tin. respectively. and sodium cyanate NaCNO. Two classes of esters arc known, cyanides or nitriles, and isocyanides, isonitriles or carbylatnincs. the latter being very poisonous and of marked nauseating odor... 

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