Metal cyanides hydrolysis

The complications which result from the hydrolysis of alkali metal cyanides in aqueous media may be avoided by the use of non-aqueous solvents. The one most often employed is liquid ammonia, in which derivatives of some of the lanthanides and of titanium(III) may be obtained from the metal halides and cyanide.13 By addition of potassium as reductant, complexes of cobalt(O), nickel(O), titanium(II) and titanium(III) may be prepared and a complex of zirconium(0) has been obtained in a remarkable disproportion of zirconium(III) into zirconium(IV) and zirconium(0).14 Other solvents which have been shown to be suitable for halide-cyanide exchange reactions include ethanol, methanol, tetrahydrofuran, dimethyl sulfoxide and dimethylformamide. With their aid, species of different stoichiometry from those isolated from aqueous media can sometimes be made [Hg(CN)3], for example, is obtained as its cesium salt form CsF, KCN and Hg(CN)2 in ethanol.15... 

The preparation of cyanomethylbenzo[6]thiophenes by reaction of halomethylbenzo[6]thiophenes with alkali metal cyanides is discussed in Section VI,D, 4. Reduction of cyanomethylbenzo[6]thiophenes affords (2-aminoethyl)benzo[6]thiophenes (Section VI, H, 2), and they give the corresponding benzo[6]thienylacetic acid on alkaline hydrolysis (Section VI,M, 3). 

WARNING Synthetic work involving cyanides requires great caution because of the extreme toxicity of gaseous HCN. This is readily released from any alkali-metal cyanide or labile metal-cyano complex by even very weak acids, including salts that are acidic due to hydrolysis. 

Ethylene chlorohydrin vapors form an explosive mixture with air the LEE and UEL values are 4.9% and 15.9% by volume of air, respectively. Among the hazardous reaction products are ethylene oxide, formed by internal displacement of the chlorine atom by the alkoxide ion, ethylene glycol formed by hydrolysis with sodium bicarbonate at 105°C (221°F), and ethylene cyanohydrin resulting from the reaction with alkali metal cyanides. 

J,V-Unsaturated carboxylic acids and their derivatives are valuable synthetic intermediates for various natural products. Two typical multi-step processes for the synthesis of p.y-unsaturated acids, Knoevenagel reaction/isomerization with base and allylic cyanide/hydrolysis,3 are those most commonly used. Other new methods have been developed 4-7 however, there is a problem with E/Z stereoselectivity. One straightforward way to obtain p,y-unsaturated acids is by the carboxylation of an allyl metal Intermediate. In the substituted allylic series, the reaction usually occurs at the more sterically hindered terminus. A stereospecific route for the synthesis of homogeranlo acid and homoneric acid by carboxylation of the lithiated allylic sulfone... 

Beryllium, calcium, boron, and aluminum act in a similar manner. Malonic acid is made from monochloroacetic acid by reaction with potassium cyanide followed by hydrolysis. The acid and the intermediate cyanoacetic acid are used for the synthesis of polymethine dyes, synthetic caffeine, and for the manufacture of diethyl malonate, which is used in the synthesis of barbiturates. Most metals dissolve in aqueous potassium cyanide solutions in the presence of oxygen to form complex cyanides (see Coordination compounds). 

Hydration reactions between metal ions and water affect mobility and adsorption but not toxicity. Hydrolysis is particularly important in the chemistry of cyanide. 

Alkaline nitration with alkoxide bases and nitrate esters was first explored by Endres and Wislicenus who synthesized phenylnitromethane by treating ethyl phenylacetate with potassium ethoxide in ethanol, followed by addition of ethyl nitrate and hydrolysis-decarboxylation of the resulting a-nitroester with aqueous acid. Phenylnitromethane is synthesized in a similar way via alkaline nitration of benzyl cyanide, followed by treatment of the resulting a -nitronitrile with aqueous base. ° Wieland and co-workers used alkali metal alkoxides and nitrate esters for the nitration of cyclic ketones but the yields and purity of product are often poor. ° ... 

Metalated aminomethyl cyanides are widely used as reagents for nucleophilic acylation64. There are few reports of the stereoselective alkylation of these reagents because upon hydrolysis, which is carried out to give the carbonyl compound, the stereocenter previously created is destroyed. A stereoselective alkylation would be valuable, of course, if in the following step the cyano group was modified or replaced in a stereoselective manner by another group. Examples of both processes have been reported. 

H. Berger (Koninklijke/Shell Laboratorium, Amsterdam) Concerning the effect of cyanides on metal catalysis (deactivation and formation of oxygenated products), what are your arguments against the explanation that the metal ion becomes completely inactive, while the products arise from a mechanism analogous to that proposed by Berger [Rec. Trav. Chim. 82, 733 (1963)] for the oxidation in tert-butyl alcohol with excess mercaptan relative to base, Did you check that no hydrolysis of disulfide occurs in the presence of cyanide ... 

---