Simple syntheses of the atlantones, the ocimenones, the tagetones, and filifolone from isoprene

Abstract

Details of the syntheses of a range of terpenes by stepwise addition of isoprene units are reported. The cis- and trans-atlantones [2-methyl-6-(4-methylcyclohex-3-enyl)hepta-2,5-dien-4-ones](1) and (2), cis- and trans-tagetones (2,6-dimethylocta-5,7-dien-4-ones)(3) and (4), and cis- and trans-ocimenones (2,6-dimethylocta-2,5,7-trien-4-ones)(5) and (6) have been synthesised by acylation at low temperature and subsequent dehydrochlorination. The atlantones (1) and (2) have also been synthesised from ocimenone by acid-catalysed Diels–Alder addition of isoprene, and filifolone (4,7,7-trimethylbicyclo[3.2.0]hept-3-en-6-one)(8) has been obtained by cyclisation of ocimenone with aluminium chloride.