Lewis Acid-catalyzed Decarboxylative Cyanation of Cyclic Enol Carbonates — Access to Multi-substituted β-Ketonitriles —

A Lewis acid-catalyzed decarboxylative substitution reaction of cyclic enol carbonates with a cyanation reagent was developed to give β-ketonitriles in good yield. It is proposed that the reaction proceeds through an oxyallyl cation intermediate or its equivalent. Interestingly, cyanation selectively took place at the more hindered site of the intermediate to afford a multi-substituted β-ketonitrile. This regioselectivity was observed by the cyanation of a wide range of substrates and is discussed in terms of the reaction mechanism. A trityl salt-catalyzed decarboxylative substitution reaction of cyclic enol carbonates with a silyl cyanide was developed to give β-ketonitriles in good yield. It is proposed that the reaction proceeds through an oxyallyl cation intermediate or its equivalent. Interestingly, cyanation selectively took place at the more hindered site of the intermediate to afford a multi-substituted β-ketonitrile.