Tricarbonyl(η6-Cycloheptatriene)manganese Hexafluorophosphate: Reactions with Enolate Nucleophiles and Decomplexation of the Product Dienyl Complexes

Reaction of tricarbonylcycloheptatrienemanganese hexafluorophosphate with a wide range of enolate nucleophiles derived from malonic esters, phenylsulfonylesters, β-ketoesters and cyclohexanones proceeds cleanly to give 6-substituted tricarbonyl(1–5-η-cycloheptadienyl)manganese complexes 3 . It was found that demetallation with concomitant stereospecific hydroxylation, to give substituted cycloheptadienes, could be accomplished by direct treatment of the dienyl complexes with ceric ammonium nitrate in buffered wet acetone. Complexes 3a–3c gave mixtures of hydroxy esters and gamma lactones 6 and 7 in proportions which depended on the nature of the substituent present. A novel and potentially useful demetallative cyclofunctionalization was found to occur on treatment of hydroxy ester 3m with excess iodine in acetonitrile, to give the cyclic ether 10 as the only observable product.