Use of group 13 aryloxides for the synthesis of green chemicals and oxide materials

Abstract

In this work, group 13 metal aryloxides [Al(MesalO)₃] (1), [Me₂Ga(MesalO)]₂ (2), [AlLi₃(MesalO)₆] (3) and [Me₂GaLi(MesalO)₂(THF)] (4) were obtained by the reaction of methyl salicylate (MesalOH) with group-13 alkyls MMe₃ (for M = Al, Ga) or their combination with BuLi in a THF/alcohol solution. The direct reaction of MMe₃ (for M = Al, Ga) and MesalOH (1 : 3) led to compound 1 or 2, respectively. When the same reactions were carried out with additional BuLi, the heterometallic compound 3 or the mixture of 4 and [Li₆(MesalO)₆] (5) was obtained. Compounds 1–5 were used for the chemical conversion of glycerol to α-hydroxy acid glyceryl esters by alcoholysis of L-lactide (L-LA), glycolide (GA), and ε-caprolactone (ε-CL). Compounds 1–5 were also efficient initiators for the ring-opening polymerization (ROP) of L-LA, GA, and ε-CL using glycerol as a branching agent to synthesize 3-arm polyesters. Heterometallic compounds 3 and 4 were attractive molecular precursors for the preparation of group 13-lithium ceramics, i.e. γ-LiAlO₂ and β-LiGaO₂.