Dissolving metals nitriles

In conclusion, nitriles may be reduced electrochemically or with dissolving metal to produce amines. Nonetheless, such reactions must be used with caution. In addition to competitive decyanation, aldehyde or 2,4,6-trialkyIhexahydro-l,3,5-triazine formation and reductive dimerization are waiting to overwhelm the unwary. 

Many other examples of chemoselective enone reduction in the presence of other reducible functionalities have been reported. For instance, the C—S bonds of many sulfides and thioketals are readily cleaved by dissolving metals. " Yet, there are examples of conjugate reduction of enones in the presence of a thioalkyl ether group." " Selective enone reduction in the presence of a reducible nitrile group was illustrated with another steroidal enone. While carboxylic acids, because of salt formation, are not reduced by dissolving metals, esters" and amides are easily reduced to saturated alcohols and aldehydes or alcohols, respectively. However, metal-ammonia reduction of enones is faster than that of either esters or amides. This allows selective enone reduction in the presence of esters"" and amides - -" using short reaction times and limited amounts of lithium in ammonia. 

Mesylates, which tend to undergo O—S scission with dissolving metals, were reduced electrochemi-cally in DMF. Yields of 70-85% were reported under conditions which left esters, nitriles and epoxides unchanged. The conversion of (30) to (31) again indicated a carbanionic intermediate. 

One of die most popular reactions in organic chemistry is dissolving metal reductions [1-3], Two systems are frequently used - sodium dissolved in ammonia with alcohol and lithium dissolved in alkylamines [4]. Although calcium is seldom used, it has been successfully applied to the reduction of a variety of compounds and functional groups [5], including aromatic hydrocarbons, carbon-carbon double and triple bonds, benzyl ethers, allyl ethers, epoxides, esters, aliphatic nitriles, dithianes, als well as thiophenyl and sulfonyl groups. 

The procedure developed for the decyanation of secondary nitriles has been extended to a,P-unsaturated nitriles. The reaction of a-unsubstitutcd a,p-unsaturatcd nitriles with LDA in THF/HMPA results in the abstraction of a y-hydrogen from a methylene site to afford a delocalized anion. Trapping this anion at the a-position by dimethylation ° ° followed by reduction-elimination with dissolving metals leads to tetrasubstituted alkenes (Scheme 6.56). ° Epoxidation of the... 

P,Y-unsaturated nitrile- before reductive decyanation with dissolving metals leads to allylic alcohols (Scheme 6.56)... 

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... 

Nitrile complexes are obtained by dissolving a metal halide in the nitrile or by replacing CO from carbonyl complexes. A kinetic investigation of the reaction of acetonitrile on Group VI hexa-carbonyls22 showed that substitution by the first acetonitrile leads to increased replacement rates for the next two molecules. The second MeCN is built in cis to the first one, and replacement of the third CO gives /ac-Mo(CO)3(MeCN)3. Further substitution does not occur. The rate law comprises two terms and is of the form22 of equation (1). 

The photochemical alkylation of olefins by nitriles and ketones is not straightforward, due mainly to the inefficient abstraction of hydrogen from an electron-withdrawing-substituted carbon by an electrophile such as the photocatalyst excited state. Nevertheless, various methyl ketones have been synthesized by the irradiation of a ketone/oleftn mixture dissolved in aqueous acetone. The mechanism of the reaction remains to be clarified, but a water-assisted C—C coupling between an acetonyl radical and the olefin has been postulated (Scheme 3.12). The reaction has several advantages, as it is cheap (an acetone/water mixture is used as the solvent) and occurs under mild metal-free conditions with no need for a photocatalyst [28],... 

Rare earth nitrates can be prepared using nitric acid to react with a corresponding oxide, hydroxide, carbonate or metal. These nitrates dissolve easily in polar solvents such as water, alcohols, esters or nitriles. They are unstable to heat as the decomposition temperature for the nitrates of scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, and samarium are 510,480, 780,450, 505, 830, and 750 °C, respectively. 

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