Stereoselective reduction of (R)-()-carvone with sodium dithionite in the presence of cyclomaltoheptaose (β-cyclodextrin) and its heptakis(2,6-di-O-methyl) derivative

✍ Scribed by Roberto Fornasier; Franco Marcuzzi; Michele Parmagnani; Umberto Tonellato

• Publisher: Elsevier Science
• Year: 1991
• Tongue: English
• Weight: 289 KB
• Volume: 217
• Category: Article
• ISSN: 0008-6215
• DOI: 10.1016/0008-6215(91)84135-2

✦ Synopsis

Regio-and stereo-selective reduction of the double bonds in conjugated ketones with numerous reducing agents under various conditions have been studied'. The reactions usually afford mixtures of products, the compositions of which depend on the reagent, the catalyst, the solvent, the pH of the medium, and the structure of, and steric hindrance associated with, the substrate.

In principle, the reduction of unsaturated ketones in aqueous alkaline solutions by sodium dithionite may afford a mixture of isomeric dihydroketones and saturated alcohols, depending on the experimental conditions. The reduction of unsaturated conjugated ketones in polar solvents' or under phase-transfer conditions' results in different yields (25-90%) and selectivities. We have studied the competition between 1,4-and 1,2-reduction of the conjugated enone (R)-( -)-carvone (1) in the presence of cyclomaltoheptaose (4, @-cyclodextrin, /ED) and its heptakis(2,6-di-O-methyl) derivative (5, DM-PCD), using sodium dithionite (Na,S,O,) as reducing agent in aqueous