Sustainable process for preparing polyesters having high glass transition temperature

A process for preparing a polyester co-polymer (III) comprising reacting an aromatic anhydride (I) and an epoxide (II):

• wherein
• R1, R2, and R5 are independently hydrogen or a C1 to C3 alkyl;
• R3 is hydrogen;
• R4 is selected from the group consisting of hydrogen, 1-methyl-ethen-1-yl, and 1-methyl-oxa-cyclopropyl;
• or R3 and R4 together with the carbon atoms that they are bound to form a three-membered cyclic ring, optionally substituted with one or two methyl groups;
• R6, R7, R8, and R9 are independently selected from the group consisting of hydrogen, (C1-C6)alkyl, halo, (C1-C6)alkyloxy, (C1-C6)haloalkyl, cyano and nitro;
• or
• one of the pairs R6 and R7, R7 and R8, or R8 and R9 together form an aromatic ring optionally substituted with one or more substituents selected from the group consisting of (C1-C6)alkyl, halo, (C1-C6)alkyloxy, (C1-C6)haloalkyl, cyano and nitro;
• a dashed line means that a bond is absent or present;
• and wherein the reaction is catalysed by a nucleophile selected from the group consisting of nitrogen-containing heterocycles, such as 4-(dimethylamino)pyridine (DMAP), 1,5,7-triazabicyclodecene (TBD) or N-methylimidazole (N-MeIm), tertiary phosphines, such as tris(2,4,6-trimethoxyphenyl)phosphine (TMPP), tricyclohexylphosphine (PCy3), or triphenylphosphine (PPh3), a halide salt, such as a bis-triphenylphosphine iminium halide salt, and mixtures thereof together with an amino-triphenolate co-catalyst having the formula:
• wherein M is Al or Fe, R10, R11, R12, R13, R14, and R15 are independently selected from the group consisting of hydrogen, C1-C6 alkyl, such as methyl, C1-C6 haloalkyl, C1-C6 alkyloxy, halogen, cyano, and nitro, and L is selected from the group consisting of H2O, tetrahydrofuran, and R—O—R′, R and R′ independently being C1-C6 alkyl.