A synthetic strategy toward isosorbide polycarbonate with a high molecular weight: the effect of intermolecular hydrogen bonding between isosorbide and metal chlorides

Abstract

Isosorbide polycarbonate (ISB-PC) was prepared by melt transesterification and polycondensation reaction by employing ISB and diphenyl carbonate (DPC) as monomers.

Regiodivergent Isosorbide Acylation by Oxidative N-Heterocyclic Carbene Catalysis in Batch and Continuous Flow

“…Gratifyingly, the solvent change to polar aprotic DMSO resulted in a satisfactory level of endo-selectivity (endo/exo = 5.2) and reduced diester formation ( 3a / 4a = 15:78, 6a = 5%, entry 13). Although a complete rationalization of the origin of regioselectivity is premature at this stage of our study, it can be envisaged that an intermolecular hydrogen bonding between the more nucleophilic 5-OH and the acyl azolium salt generated from D might play a central role in promoting the endo - selectivity of entry 13, in analogy with an earlier study reporting IS acylations in the presence of metal chlorides . Additional experimental evidences consist in the loss of regioselectivity when using CaCl 2 as an additive in combination with D (entry 14) and the switch back to preferential endo - selectivity with triazolium salt E that displays the same azolium structure of the exo - selective C and BF 4 – in place of I – as the counterion (entry 15 vs entry 5).…”

“…Although a complete rationalization of the origin of regioselectivity is premature at this stage of our study, it can be envisaged that an intermolecular hydrogen bonding between the more nucleophilic 5-OH and the acyl azolium salt generated from D might play a central role in promoting the endo - selectivity of entry 13, in analogy with an earlier study reporting IS acylations in the presence of metal chlorides . Additional experimental evidences consist in the loss of regioselectivity when using CaCl 2 as an additive in combination with D (entry 14) and the switch back to preferential endo - selectivity with triazolium salt E that displays the same azolium structure of the exo - selective C and BF 4 – in place of I – as the counterion (entry 15 vs entry 5). These latter results further confirm the importance of counterions in directing NHC catalysis and, in this specific study, strengthen our hypothesis that the endo - selectivity of the disclosed IS esterification is mainly controlled by electronic factors, which are responsible for 5-OH nucleophilicity enhancement by intermolecular hydrogen-bonding interactions .…”

“…Additional experimental evidences consist in the loss of regioselectivity when using CaCl 2 as an additive in combination with D (entry 14) and the switch back to preferential endo - selectivity with triazolium salt E that displays the same azolium structure of the exo - selective C and BF 4 – in place of I – as the counterion (entry 15 vs entry 5). These latter results further confirm the importance of counterions in directing NHC catalysis and, in this specific study, strengthen our hypothesis that the endo - selectivity of the disclosed IS esterification is mainly controlled by electronic factors, which are responsible for 5-OH nucleophilicity enhancement by intermolecular hydrogen-bonding interactions . This appears evident with the precatalyst D , which is highly endo-selective in DMSO having a strong hydrogen-bond-accepting (HBA) character (entry 13) and moderately exo-selective in noncoordinating DCM (entry 11).…”

En Route to CO2-Based (a)Cyclic Carbonates and Polycarbonates from Alcohols Substrates by Direct and Indirect Approaches

“…In this regard, a large range of catalysts was tested to selectively activate the endo or exo alcohol moieties and to prevent reactivity disparities that would considerably limit the molar mass of the PC. Among them, metal salts [202], metal alkoxides [203,204], inorganic carbonates [205], ionic liquids [206][207][208][209][210][211][212][213], organic bases [214] and others [215][216][217][218] enabled the facile construction of defect-free PCs derived from isosorbide with Mn values in the range of 14,000 to 55,000 g/mol. Carbonate metathesis polymerization principle catalyzed by K 2 CO 3 .…”

Acylamido-based anion-functionalized ionic liquids for efficient synthesis of poly(isosorbide carbonate)

“…[14][15][16][17] These characteristics make ISB the preferred alternative monomer for BPA. [18][19][20] Compared with traditional BPA-PC, poly(isosorbide carbonate) (PIC) has good scratch resistance, strong UV resistance, and innocuous character, which enable PIC to be used in a broader range of applications, especially in food packaging and medical equipment. [21][22][23] Usually, diphenyl carbonate (DPC) is used instead of phosgene in an attempt to design a phosgene-free route for preparing PIC.…”