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Ring-Opening Polymerization of Epoxides: Facile Pathway to Functional Polyethers via a Versatile Organoaluminum Initiator

“…As a first step toward combining the advantages of AROP and CROP, we sought to develop an initiator with the simplicity and efficiency of the Vandenberg catalyst, but with a well-defined structure providing control of molecular weight and chain-end functionality. The structure of the Vandenberg catalyst is unknown; however, new insight into compositionally homologous organoaluminum species over the intervening decades has provided new insight. − On the basis of this foundational work, we posited that a bis­(μ-alkoxo­alkylaluminum) ([R 2 Al­(μ-OCH 2 CH 2 OMe)] 2 , R = Me, Et, iBu) motif was likely homologous to the resting-state structure of the Vandenberg catalyst with respect to epoxide polymerizations. While synthesizing a series of bis­(μ-alkoxo­alkylaluminum)­s by tuning the stoichiometry between an N-substituted ethanolamine ligand and triethylaluminum (TEAl) at −78 °C in hexane, in one instance we isolated an asymmetric organoaluminum species that proved to be effective for epoxide polymerizations; the triethylaluminum adduct of (2-dibenzyl­amino)­ethoxydiethyl­aluminum, or TAxEDA, where x refers to the specific N-substitution (here x = 2-dibenzylamino-).…”

The Mechanism of Epoxide Carbonylation by [Lewis Acid]+[Co(CO)4]- Catalysts

“…The cationic [(salph)Al(THF)(EB)] + is converted to a neutral aluminum alkoxide upon the ring opening of epoxide. In both solid and solution phases, aluminum cations supported by ligands of the salen( t Bu) family (i.e., having the general form N , N ‘-alkylene (or arylene) bis(3,5-di- tert -butylsalicylideneimine)) are almost always six-coordinate; − the only reported exceptions cannot be prepared in the presence of donor solvents . Conversely, aluminum alkoxides and siloxides supported by these ligands are five-coordinate at room temperature in solution (C 6 D 6 and CDCl 3 ) and in the solid phase, even when crystallized from donor solvents. ,− Further, the binding of 4-( N , N -dimethylamino)pyridine, a strong donor, to the aluminum alkoxide (TPP)AlOR has been shown to be much weaker than to the related carbonate and carboxylate, (TPP)AlO 2 COR and (TPP)AlO 2 CR (TPP = tetraphenylporphyrin), respectively …”

Reactions of Trimethylaluminium: Modelling the Chemical Degradation of Synthetic Lubricants

“…[27] However, this has tended to focus not upon its synthesis as ab y-product of ketonization reactions but rather on the oxophilic derivatization of AlÀCbonds [28] by moisture [29] or oxygen. [30] From astructural point of view,a luminium organooxide formation [31] and di-/trimerization is welle stablished, [32] for example, the simple aluminium alkoxide Me 2 AlOMeh as been shown to be trimeric. [33,34] In this work we model the reaction of TMA with synthetic POEs and elucidate intermediates along the reaction pathway between TMA and esters in general for the first time.…”