Development of the Formation of Enolate Controlled by Acid-base Bifunctional Organochalcogenide Catalysts

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Asymmetric cyclopropanation, epoxidation and aziridination catalyzed by chiral chalcogenides are described. A novel Lewis acid/Bronsted base catalysts formed by a C2 symmetric chiral chalcogenide bearing isoborneol or camphor skeletons were readily prepared from (1S)-10-camphorsulfonic acid. Di-exo-2-hydroxy-10- bornyl selenide and LiH promoted the reaction of phenacyl bromide with methyl vinyl ketone to afford the desired trans cyclopropane with up to 50% ee. The reaction of phenacyl bromide with N-benzylidene-4-methylbenzenesulfonamide was also catalyzed by the selenide to produce the cis aziridine with up to 60% ee. Although the good yields and moderate enantioselectivities for oxirane formations were obtained from the reaction of phenacyl bromide with aromatic aldehydes, the reactions with aliphatic aldehydes afforded the desired epoxides in good yields and poor enantioselectivities.