A new route to keto and alkyl derivatives of (R)-carvone via diastereoselective conjugate addition of nitronate ions

Abstract

A reatividade e diastereosseletividade da adição conjugada de íons nitronatos representativos à (R)-carvona foi estudada. Os adutos de Michael 2a-e foram obtidos em bom rendimento e boa 3,2-cis-3,5-trans-seletividade. Os nitroadutos 2b e 2c foram transformados via uma reação de Nef nos ceto-derivados 9 e 10 ao passo que uma reação de desnitração transformou 2b e 2d nos derivados alquilados da carvona 11 e 12.The reactivity and diastereoselectivity of conjugate addition of different nitronates ions to (R)-carvone was systematically studied. The Michael adducts 2a-e were obtained in good yield and 3,2-cis-3,5-trans selectivity. The nitroadducts 2b,c were transformed via Nef reaction into (R)-carvone ketone derivatives 9,10 and nitroadducts 2b,d led to (R)-carvone alkylated derivatives 11,12, via a denitration reaction.A New Route to Keto and Alkyl Derivatives of (R)-Carvone J. Braz. Chem. Soc.

The Nitro to Carbonyl Conversion (Nef Reaction): New Perspectives for a Classical Transformation

“…[35] This procedure has been used for the preparation of keto derivatives of optically active (R)-carvone by as equential conjugate addition-Nef reaction. [36] Recently this oxidant has also been employed to convert tricyclic nitro derivative 49 into ketone 50 en route to the total synthesis of the sesquiterpenoids echinopines Aa nd B (Scheme 15). [37] Dimethyldioxirane is an oxidizing agent that can be prepared by reactiono fo xone with acetone.S imilarly to oxone,t his reagent is able to convert the nitronate anion obtainedfrom secondary nitroalkane 51 into cyclopentenone derivative 52 at low temperature (Scheme 16).…”