STEREOCONTROLLED FUNCTIONALIZATION IN THE CYCLOHEXANE RING USING ORGANOMOLYBDENUM CHEMISTRY

Article abstract of DOI:10.1021/ja00295a030

The reaction betwen (η⁴-cyclohexadiene)Mo(CO)2Cp(1) or(η⁴-5-methylcyclohexadiene)Mo(CO)2Cp(3) cations and a range stable enolate nucleophiles has been studied and was found to occur with high regio- and stereoselectivity togive (?-allyl)Mo(CO)2Cp complexes.The C-C bond formation between 1 and unsymmetrrical enolates was diastereoselective: reaction with methyl 1-oxo-2-sodiocyclopentanecarboxylate gave a single diastereomer, the relative stereochemistry of which was determined by X-ray methods.Decomplexation of the products (?-allyl)Mo(CO)2Cp complexes was accomplished by treatment with iodine.Complexes containing a pendant carboxylic acid produced lactones with high regio- and stereocontrol, while complexes lacking a nucleophilic group gave substituted iodocyclohexenes which could be further manipulated.The value of this method for stereocontrol is illustrated by the preparation of an acyclic fragment having relative stereochemistry corresponding to the C(4), C(5), and C(6) centers in the-macrolide antibiotics tylosin and magnamycin B.