Nitriles as solvents

Cu(II) EPR signal in nitriles as solvent as well as by polarographic measurements 144>. Similarly, the EPR signal disappeared when Cu(OTf)2 was used for catalytic cyclo-propanation of olefins with diazoesters 64). In these cases, no evidence for radical-chain reactions has been reported, however. The Cu(acac)2- or Cu(hfacac)2-eatalyzed decomposition of N2CHCOOEt, N2C(COOEt)2, MeCOC(N2)COOEt and N2CHCOCOOEt in the presence of cyclopropyl-substituted ethylenes did not furnish any products derived from a cyclopropylcarbinyl - butenyl rearrangement128. These results rule out the possible participation of electron-transfer processes and radical intermediates which would arise from interaction between the olefin and a radical species derived from the diazocarbonyl compound. 

R. R. Schmidt, M. Behrendt, and A. Toepfer, Nitriles as solvents in glycosylation reactions Highly selective (3-glycoside synthesis, Synleti p. 694 (1990). 

Amidomercuration using nitriles has received the most attention. This reaction commonly employs mercury(II) nitrate with the nitrile as solvent. Acetonitrile is the most widely used nitrile, but RSCN and R2NCN can also be employed.243... 

The electrochemical reduction of CO yields squaric acid. The use of nitriles as solvents allows to increase the current efficiencies substantially 530> ... 

When the reactions of benzenetellurinyl acetate or trifluoroacetate to olefins were carried out with nitriles as solvents and boron trifluoride diethyl etherate as catalyst, 2-acylamino-1-alkyl phenyl telluroxides were obtained. Telluroxide elimination produces 4,5-dihydrooxazoles2. 

If we dissolve f-butanol in a nitrile as solvent and add strong acid, a reaction does take place. The acid does not proton ate the nitrile, but does protonate the alcohol to produce the t-butyl cation in the usual way. This cation is reactive enough to combine with even such a weak nucleophile as the nitrile. 

If the reactions are carried out in a nitrile as solvent, rather than dichloromethane, using triflic acid as catalyst, a modified Ritter reaction takes place, and the intermediate nitrilium ion traps the liberated amine, forming an amidine (Scheme 67). In an earlier reaction cf. Scheme 67) the lithium perchlorate catalyzed reaction of sulfenyl chlorides with alkenes in the presence of nitriles had also given l-amido-2-sulfenyl adducts. Ritter products are also obtained in good yields by anodic oxidation (Pt or C, 1.2-1.4 V) of disulfides in acetonitrile, in the presence of excess alkene, using B114NBF4 as supporting electrolyte (Scheme 68). ... 

Oxazolines. These heterocycles have been prepared by the reaction of epoxides with nitriles in the presence of sulfuric acid or stannic chloride. However, yields are in the range 10-40%. They are considerably improved when BF3 etherate (1 eq.) is used with an excess of nitrile as solvent. ... 

Wang and Zhu reported a general synthesis of 5-(perfluoroaIkyl)-2-substi-tuted 4-oxazolecarboxylic acid ethyl esters 1601 from decomposition of ethyl 2-diazoperfluoroalkylacetoacetates 1600 in the presence of a nitrile as solvent (Scheme 1.408). Rhodium(II) acetate was the preferred catalyst for this reaction. The yields of 1601 varied considerably. 

An interesting result of the unimportance of the nucleophile to the rate (and therefore the usefulness) of an S l reaction is that very poor nucleophiles indeed may react in the absence of anything better. Nitriles, for example, are very poorly basic and nucleophilic because the lone pair of electrons on the nitrogen atom is in a low-energy sp orbital. However, if t-butanol is dissolved in a nitrile as solvent and strong acid is added, a reaction does take place. The acid does not protonate the nitrile, but does protonate the alcohol to produce the t-butyl cation in the usual first step of an Sj l reaction. This cation is reactive enough to combine with even such a weak nucleophile as the nitrile. 

Coned. H2SO4 added with stirring to ice-cooled phenylacetonitrile, allowed to warm to room temp., then a soln. of trans-2-huiene episulfide added slowly with vigorous stirring during 1 hr. crs-2-benzyl-4,5-dimethyl-Z 2-thiazoline. Y 76%. — Use of excess nitrile as solvent has been found to produce the best yields. F. e. s. G. K. Helmkamp et al., Am. Soc. 88, 1030 (1966). 

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