Polymerization Reactions in an Al(OBus)3-(COOH)2 System

Reactions in an Al(OBu^s)₃-(COOH)₂ (OA)-tetrahydrofuran (THF)/(CD₃)₂SO (DMSO-d₆) system (Al(OBu^s)₃: THF : DMSO-d₆: OA = 1 : 5 : 5 : x, x = 0.01 –3) were studied, without the addition of water and the process was monitored by NMR. When x 0.3, homogeneous solutions were obtained, whereas white precipitates formed with x 0.7. The formation of sec-butyl alcohol was evident with x 0.6, indicating that oxalate groups coordinate to aluminum to release sec-butyl alcohol. ¹³C NMR spectra of the solutions after 1 day suggest the presence of polymeric species if 0.03 x 0.6. The addition of a small amount of water resulted in the formation of a white precipitate (Al(OBu^s)₃: THF : DMSO-d₆ : OA : H₂O = 1 : 5 : 5 : 0.3 : y,y = 0.03–0.3), indicating that water, possibly formed by esterification in the Al(OBu^s)₃-OA-THF/DMSO-d₆ system, does not take a major role in the present system.