The nucleophilic addition of a cyanide anion to a carbonyl group is the basis for several cyanide-catalyzed organic reactions, which are summarized in this review. Since cyanide is also a good leaving group, it is an excellent catalyst for transacylation reactions. As an electron-withdrawing group, it also stabilizes a negative charge in its α-position, thus allowing the umpolung of aldehydes to formyl anion equivalents. The two leading examples are the benzoin condensation and the Michael–Stetter reaction furnishing α-hydroxy ketones and 1,4-dicarbonyl compounds, which are both catalyzed by cyanides. The review also covers variants like the silyl-benzoin coupling, the aldimine coupling and the imino-Stetter reaction. Moreover, some cyanide-catalyzed heterocyclic syntheses are reviewed.1 Introduction2 Nucleophilic Additions2.1 Cyanohydrin Formation2.2 Corey–Gilman–Ganem and Related Oxidation Reactions2.3 Conjugate Addition2.4 Intramolecular Carbocyanation3 Transacylation Reactions3.1 Ester Hydrolysis and Transesterification3.2 Formation of Amides3.3 Ketones from Esters3.4 Esters from Ketones4 Transformations Involving an Umpolung4.1 Benzoin Condensation4.2 Aldimine Coupling4.3 Michael–Stetter Reaction4.4 Imino-Stetter Reaction5 Formation of Heterocycles5.1 Oxazolines from Isocyanoacetates5.2 Imidazoles from TosMIC via Oxazolines5.3 Bargellini Reaction6 Conclusion

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The Front Cover shows a branch and some fruits of Terminalia chebula, a tropical tree. Chebulic acid (the formula in the magnifying glass) is the aglycon of several antioxidant ingredients of the fruit. The artwork is based on a graphic from 1874 (reproduced from www.biolib.de published by Kurt Stüber). The first total synthesis of chebulic acid was accomplished. Key steps were a cerium‐catalyzed α‐hydroxylation of an β‐oxoester and a cyanide‐catalyzed ring‐transformation of the respective intermediate product to the δ‐lactone structure. More information can be found in the Research Article by D. Kieslich and J. Christoffers.

The first total synthesis of racemic chebulic acid is reported, which is the aglycon of several antioxidant ingredients of the fruit of the Terminalia chebula tree. The route started with the straightforward preparation of an indanone‐based β‐oxoester from a benzaldehyde derivative (84 % over the first five steps). The side chain of the target compound was then introduced by conjugated addition of a cuprate reagent derived from dimethyl succinate, which was followed by the first key step of the synthesis: a cerium‐catalyzed α‐hydroxylation of an β‐oxoester. The second key step was the cyanide‐catalyzed ring transformation of the cyclic α‐hydroxy‐β‐oxoester to a δ‐lactone. Finally, chebulic acid was obtained after six‐fold demethylation of three methyl ester moieties and three phenolic ether functions. The overall synthetic route consists of nine consecutive steps and was accomplished in 15 % overall yield.