4-Hydroxycyclopent-2-en-1-one and derivatives as chiral synthetic equivalents of cyclopentadienone in asymmetric Diels-Alder reactions

Article abstract of DOI:10.1016/S0040-4020(01)85571-X

Endo-tricyclodecadienone 8a and related annelated-cyclopentenones (8b, 20, 21a-c and 22) are synthesized in good chemical yield by a Diels-Alder reaction of 4-hydroxycyclo-pent-2-en-1-one 12a and derivatives 12b-h with an appropriate diene. These additions are considerably accelerated by Lewis catalysts, high pressure and by using water as solvent. Due to opposing steric and electronic effects the diastereofacial selectivity of the asymmetric cycloadditions is moderate. By carefully choosing the substrate and reaction conditions an acceptable π-facial selectivity can be achieved.