Potassium cyanide, with Lewis acids

Halides can be converted into cyanides. Thus, the reaction of benzyl bromide in toluene with potassium cyanide, catalysed by alumina, on sonication gives the substitution product, viz. benzyl cyanide in 76% yield. In the absence of ultrasound alkylation is the preferred pathway (Scheme 4). The difference is because ultrasound forces cyanide into the surface of alumina, enhancing cyanide nucleophilicity and reducing the lewis acid character. 

Reactions with Oxiranes, Oxetanes, and Aziridines. Lewis acids, lanthanide salts, and titanium tetraisopropoxide or aluminum isopropoxide catalyze the reactions of cyanotri-methylsilane with oxiranes, oxetanes, and aziridines, yielding ring-opened products. The nature of the products and the regio-selectivity of the reaction are primarily dependent on the nature of the Lewis acid, the substitution pattern in the substrate, and the reaction conditions. Monosubstituted oxiranes undergo regiospe-cific cleavage to form 3-(trimethylsiloxy)nitriles when refluxed with a slight excess of cyanotrimethylsilane in the presence of a catalytic amount of potassium cyanide-18-crown-6 complex (eqs 8-10). The addition of cyanide occurs exclusively at the least-substituted carbon. 

The cyclic carbonate can then be copolymerized with cyclic anhydride to yield, with loss of carbon dioxide, a polyester of relatively high molecular weight. This copolymerization is initiated by a number of inorganic salts including sodium cyanide and potassium chloride, bases such as potassium hydroxide or sodium amide, and Lewis acids at 200°C. Presumably, the initiation begins with nucleophilic attack of an anion on the cyclic carbonate... 

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