Nouveau mode de synthese des decalones—I

The action of sodium t-amyloxide on 3-(ω-bromobutyl) cyclohexanones (cycloalkylation) yields -decalones. When the 2-position of the initial cyclohexanone is unsubstituted, the reaction yields an equilibrium mixture of isomers (largely trans); but when the cyclohexanone bears a 2-alkyl group, the only product is the cis -decalone with an angular alkyl group. This cycloalkylation thus appears to be stereospecific.

The synthesis of the four -decalones (Va, Vb, V′a, V′b) is described.

The 3-(ω-bromobutyl) cyclohexanones were prepared by the action of the Grignard reagent from the tetrahydropyranyl ether of 4-chloro-1-butanol on the 1,3-cyclohexanedione enol ethers (I, I′), reduction of the resulting 3-(ω-hydroxybutyl) cyclohexenones (II, II′) to the cyclohexanones (III, III′), and finally treatment of the latter with phosphorus tribromide.

A variant is described in which the cycloalkylation is carried out on the 3-(ω-bromobutyl) cyclohex-2-enones (VI).