This is very useful to go from substituted chloromethyl compounds, to the easily reduced acetonitriles. What SWIM liked was that it didn't use any DMF, as most acetonitrile syntheses describe, and the yields are usually higher.
From JOC, vol. 25, pp.877 (1960):
Reaction of primary and secondary chlorides with NaCN in DMSO occurs rapidly and efficiently to result in an improved general method for preparing nitriles. Advantages are also realized in conversion of primary and secondary bromides to their corresponding nitriles...
It is now reported that typical primary chloroalkanes react rapidly and exothermically with sodium cyanide in partial solution in dimethyl sulfoxide to give the corresponding nitriles in excellent yields. The nitriles are conveniently isolated from the reaction mixture by dilution with water followed by suitable extraction. At the preferred reaction temperatures of 120-140 C the conversion of primary
chlorides to nitriles may usually be completed in one half to two hours... Secondary chloro compounds react relatively slowly (ca. three hours) to give the corresponding nitriles in moderate yields (65-70%).
Experimental
Reaction of 1-chlorobutane and sodium or potassium cyanide. Valeronitrile. 1-Chlorobutane (93 g., 1 mole) was added in 10-15 min. to a rapidly stirred partially-soluble mixture of sodium cyanide (53 g., 1.08 moles, Reagent) in dimethyl sulfoxide (250 ml., technical; ) at 80 C. The temperature of the mixture rose rapidly and was kept at 140 +- 5 C by cooling with water when necessary. During the reaction the mixture became more fluid, and the insoluble salts more crystalline. After the 1-chlorobutane had been added, the temperature dropped rapidly, and the reaction was apparently complete. The brown reaction mixture was cooled, diluted with water to a volume of ca. 1000 ml., and extracted with ether (3 X 150 ml.). The pale yellow ether extracts were washed with 6N HCl (to hydrolyze the small amount of noxious isocyanide) and water, and dried over CaCl2. After removal of ether, the residue was rectified over P2O5 to give forerun (6.0 ml.), b.p. 110-138 C (747 mm.), and valeronitrile (77g., 0.93 mole, 93%), b.p. 138-139 C (747 mm.)
Now for the good stuff, from JOC, vol. 29, pp.2860 (1964):
2,5-Dimethoxybenzyl Chloride, yield 60%... see
Post 384897
(Rhodium: "Chloromethylation of p-dimethoxybenzene - 61%!", Methods Discourse)2,5-Dimethoxyacetonitrile, m.p. 52-53 C, was obtained in 98% yield from the reaction of the dimethoxybenzyl chloride with NaCN in DMSO according to the procedure of Friedman and Schechter
above. Yields of 30% were obtained by the earlier procedure using aqueous ethanol.
A good read for solvent effects of DMSO, read JOC, vol. 29 pp. 3262 (1964) - it is informative.