REGIOCONTROLLED AND STEREOCONTROLLED FUNCTIONALIZATION OF ACYCLIC MOLYBDENUM ETA-3-ALLYL COMPLEXES

Chemical transformation of the ester CpMo(Co)2(syn-eta-3-1-C3H4COOMe) to its eta-3-allyl alcohol, acid, acid chloride, and amide has been achieved. Treatment of CpMo(CO)2(syn-eta-3-1-C3H4CHR(OH)) (R = H (2f), CH3 (2g) with (CF3SO2)2O in ether at -78-degrees-C stereoselectively generates, the air-stable s-trans-eta-4-diene cations, which have been characterized by appropriate physical methods. The ionization process proceeds via an intramolecular S(N)2 mode. The s-trans-eta-4-cis-pentadiene cation reacts with water, alcohol, thiol, and amine to give eta-3-allyl derivatives, which retain the same configuration as that of 2g. The enolate CpMo(CO)2(syn-eta-3-1-C3H4COCH2Li) condenses with aldehyde at -78-degrees-C to yield the aldol products CpMo(CO)2(syn-eta-3-1-C3H4COCH2CHR(OH)) (R = Ph (6a), CH3 (6b) (CH3)2CH (6c)) with good diastereoselectivity. The major diastereomer has been isolated and characterized by X-ray diffraction. Further reduction of this diastereomer with NaBH4 produces the corresponding 1,3-diol as a single diastereomer. Utilization of 2g and 6e in synthesis of acyclic 1,3-diol and 1,3,5-triol has been achieved, with excellent stereoselectivity; a mechanism is been proposed.