High pressure Diels-Alder reactions of (+)-nopadiene with cycloalkenones

Cycloadditions between (+)-nopadiene and 2-cyclopenten-1-one, 2-cyclohexen-1-one, 4-oxo-2-cyclopentenyl-acetate and two indenone derivatives, prepared in situ from the corresponding bromoindanones, have been studied. All cycloadditions are regioselective and endo-anti diastereoselective. The best yields were obtained when the Diets-Alder reactions were carried out under high pressure conditions. All new compounds were characterized by their spectroscopic data, in particular by extensive NMR investigations. (C) 2004 Elsevier Ltd. All rights reserved.