Interaction of oxygen functionalized alkenes with a methylaluminoxane-zirconocene catalyst studied by NMR

Reactions of hydroxyl, ether and carbonyl functionalized alkenes with methy laluminoxane prepared in toluene-d(8) (MAO) and zirconocenedichloride (Cp2Z rCl2) were investigated by H-1- and C-13-NMR spectroscopy at 27 degrees C. The 11 alkenes studied bear a terminal C=C bond separated by 7-9 (-CH2-) un its from the heteroatom moiety. Intramolecular connectivities in mono (alke ne), bi (alkene and MAO) and tri (alkene, MAO and Cp2ZrCl2) component mixtu res were determined by 2D HSQC, HMBC, ROESY and NOESY NMR techniques. The f ive studied alkenols formed aluminium alkoxides with MAO even in the case o f a substantial steric hindrance around the OH group. Zirconocene enhanced the formation of aluminium alkoxides. Decomposition to free alkenol was obs erved only for the straight chain alkenol (10-undecen-1-ol). The OTMS deriv atives formed dimers of the type CH2=CR1R2 along with methyl derivatives, C H2=C(Me)(R) and (Me)CH-CH(R), in the presence of MAO and Cp2ZrCl2. 10-Undec enyl methyl ether and methyl decenoate remained mainly as a free comonomer in the presence of MAO or MAO/Cp2ZrCl2, though a transient coordination of the former to MAO was deduced. Unsaturated species Me2C=CH-Al-X and CH2-CH( CH2)(5)CH2CH=C(t-Bu)O-Al-X (X=MAO oligomer) were formed in thr reaction of t-butyl undecenoate or 2,2-dimethyl-11-dodecen-3-one with MAO or MAO/Cp2ZrC l2. Interaction of the CH2=CH part of the functionalized alkenes with zirco nocene was not observed. A possible coordination of the C=C bond to MAO was observed only for the sec alkenols. (C) 1999 Elsevier Science S.A. All rig hts reserved.