Total synthesis of (±)-seychellene

Abstract

The total synthesis of (±)-seychellene (4,7,8-trimethyl-11-methylenetricyclo[5.3.1.0^3,8]undecane)(I) from2,3-di-methylcyclohex-2-en-1-one (XIV) is described. The ketone (XIV) was converted into 2-methyl-2-(3-methyl-5-iodopentyl)-3-methylenecyclohexan-1-one (XV), which gave 2-methyl-2-(3-methyl-5-iodopentyl)-3-bromo-methylcyclohexa-3,5-dien-1-one (XIX) with N-bromosuccinimide. Treatment of bromo-ketone (XIX) with chromium(II) chloride followed by acid gave 2,3-dimethyl-2-(3-methyl-5-iodopentyl)cyclohexa-3,5-dien-1-one (XXI). 2,3-Dimethyl-2-(3-methyl-5-dimethylaminopentyl)cyclohexa-3,5-dien-1-one (XXII) was obtained from the dienone (XXI) and was oxidised; pyrolysis of the resulting N-oxide yielded 4,7,8-trimethyltricyclo-[5.3.1.0^3,8]undec-9-en-11-one (VII). The adduct (VII) was hydrogenated to (±)-norseychellanone (4,7,8-trimethyltricyclo[5.3.1.0^3,8]undecan-11 -one), whose transformation into (±)-seychellene is known.