Asymmetric Synthesis via Acetal Templates. 14.1 Preparation of Enantiomerically Pure (3S,4S)- and (3S,4R)-Statine Derivatives

Cyanide Anions as Nucleophilic Catalysts in Organic Synthesis

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 Introduction

2 Nucleophilic Additions

2.1 Cyanohydrin Formation

2.2 Corey–Gilman–Ganem and Related Oxidation Reactions

2.3 Conjugate Addition

2.4 Intramolecular Carbocyanation

3 Transacylation Reactions

3.1 Ester Hydrolysis and Transesterification

3.2 Formation of Amides

3.3 Ketones from Esters

3.4 Esters from Ketones

4 Transformations Involving an Umpolung

4.1 Benzoin Condensation

4.2 Aldimine Coupling

4.3 Michael–Stetter Reaction

4.4 Imino-Stetter Reaction

5 Formation of Heterocycles

5.1 Oxazolines from Isocyanoacetates

5.2 Imidazoles from TosMIC via Oxazolines

5.3 Bargellini Reaction

6 Conclusion

An efficient approach to trans-4-hydroxy-5-substituted 2-pyrrolidinones through a stereoselective tandem Barbier process: divergent syntheses of (3R,4S)-statines, (+)-preussin and (−)-hapalosin

Natural products of (+)-preussin and (−)-hapalosin have been asymmetrically synthesized through the stereoselective tandem Barbier process.

Asymmetric syntheses of epohelmins A and B by In-mediated allylation

A diastereoselective new approach for the synthesis of trans-4-hydroxy-5-allyl-2-pyrrolidinone 9 has been developed through In-mediated allylation of α-chiral aldimine 8 with allyl bromide. The stereochemistry at the C-2 stereogenic center of 9 was controlled by both the α-OTBS substitution and the sulfinamide moiety. The utility of this asymmetric allylation is demonstrated by the asymmetric syntheses of epohelmins A (4) and B (10).

Stereoselective formation of chiral trans-4-hydroxy-5-substituted 2-pyrrolidinones: syntheses of streptopyrrolidine and 3-epi-epohelmin A

A highly diastereoselective approach for synthesis of trans-4-hydroxy-5-substituted 2-pyrrolidinones has been developed. The streptopyrrolidine and 3-epi-epohelmin A were synthesized by this one-pot cascade protocol.