Regio- and stereo-chemical outcomes in the nucleophilic ring cleavage reactions of mono-epoxides derived from cis-1,2-dihydrocatechols

Abstract

Reactions of the mono-epoxy derivatives, 4–7, of the cis-1,2-dihydrocatechols 1 and 2 with various oxygen-, nitrogen-, carbon- and halogen-centred nucleophiles have been studied. In both direct and acid-catalysed processes these epoxides react exclusively by the pathway involving nucleophilic attack at 5a-C of the substrate and such regioselectivity has been exploited in a synthesis of the fluoro-deoxy-conduritol 32. Palladium-catalysed nucleophilic additions to epoxide 4 proceed in the same regiochemical sense (attack at 5a-C) but with overall retention of configuration. A competing process associated with palladium-catalysed addition of phthalimide to epoxide 4 is isomerisation of the substrate to cyclohexenone 41. Product structures have been established by single-crystal X-ray analyses and chemical correlation studies.