Dimethylaluminum Complexes Supported By The Aryl Amide Bearing Intramolecular Ether Donors:Syntheses, Structures And Their Catalytic Activity For Ring-Opening Polymerization Of ε-Caprolactone

In my work, six imine compounds, [o-RiOC6H4CH=NAr] ( Ri = CH3OCH2CH2, Ar = 2,6-’Pr2C6H3, la; R, = CH3OCH2CH2, Ar = 2,4,6-Me3C6H2, lb; Ri = CH3OCH2CH2, Ar= C6H5, lc; R,= CH3, Ar = 2,6-’Pr2C6H3, Id; Ri= CH3, Ar=2,4,6-Me3C6H2, le; Ri= CH3, Ar=o-CH3OC6H4, If) were synthesized by the condensation reaction of 2-(2-methoxyethoxy) aldehyde with substituted aniline. Under nitrogen atmosphere, a series of products [oRiOCf^ClrhNHAr] (Ri = CH3OCH2CH2, Ar = 2,6-/Pr2C6H3, 2a; R. = CH3OCH2CH2, Ar = 2,4,6-Me3C6H2, 2b; Ri = CH3OCH2CH2, Ar= C6H5, 2c; R,= CH3, Ar = 2,6-’Pr2C6H3, 2d; Ri= CH3> Ai=2,4,6-Me3C6H2, 2e) were obtained by reducing with lithium aluminium hydride in ether solution at room temperature. Compounds 2g [o-RiOC6H4CH(CH3)NHAr] (Ri = CH3OCH2CH2, Ar = 2,6-’Pr2C6H3) was prepared by reacting of compound la with MeMgl in toluene refluxing condition. At nitrogen atmosphere, trimethylaluminium was added dropwise into compounds 2a or 2b under rapid stirring at 110℃ for 10 h. The final products dimethyl aluminum complexes 3a [o-RiOC6H4CH2N(Ar)AlMe2], (R1= CH3OCH2CH2, Ar= 2,6-’Pr2C6H3) and 3b [o-R1OC6H4CH2N(Ar)AlMe2], (R1= CH3OCH2CH2, Ar= 2,4,6-Me3C6H2) were prepared after the reaction mixtures above were degassed and recrystallized in n-hexane solution.Nuclear magnetic resonance measurements were carried out to characterize the structure of the as-prepared products. The molecular structure of compound 3a was characterized by single crystal diffraction measurement. Opening polymerization reaction of ε-caprolactone was carried out by utilizing compound 3a. All the experimental results showed that compound 3a had excellent catalytic activity. Polycaprolactone with conversion of 50% was obtained by ε-caprolactone polymerizations at 30℃. Meanwhile, the catalytic activity of 1c was increased with the increase of temperature, while at 100 ℃, the catalytic activity was the highest, where the conversion of ε-caprolactone was above 90% after twenty minutes.