Synthesis of Tris‐ and Pentakis(triarylmethane) Compounds Bearing Perfluoropyridine Moieties from Functionalized Triarylmethane Precursors

Under controlled conditions, the S_NAr reactions of 4,4′-(((p-tolylmethylene)bis(2,6-dimethyl-1,4-phenylene))bis(oxy))bis(2,3,5,6-tetrafluoropyridine) with hydroxybenzaldehydes are employed to synthesize bis(oxy)benzaldehydes and tetrakis(oxy)benzaldehyde as the major reaction products. Moreover, a new class of highly triarylmethane-branched perfluoropyridines is synthesized through the Friedel–Crafts arylation reaction of the derived (oxy)benzaldehydes with veratrole under silicotungstic acid catalysis.

Abstract

The S_NAr reactions of 4,4′-(((p-tolylmethylene)bis(2,6-dimethyl-1,4-phenylene))bis(oxy))bis(2,3,5,6-tetrafluoropyridine) 4 with hydroxybenzaldehydes 2a-c were evaluated. Parameters such as reaction conditions, the molar ratio of reactants, and the nucleophilicity of hydroxybenzaldehydes played a crucial role in determining the selectivity of the reactions. The substitution of fluorines in precursor 4 occurred under harsh conditions, and the highest selectivity was observed for 3-hydroxybenzaldehyde and 2-hydroxybenzaldehyde, respectively. By optimizing the molar ratio of reactants and leveraging the higher nucleophilicity of the resulting potassium 3-formylphenolates, along with the steric hindrance from potassium 2-formylphenoxide, we successfully synthesized bis(oxy)benzaldehyde 9a′ and tetrakis(oxy)benzaldehyde 9c as the major products. Additionally, a new class of perfluorinated tris- and pentakis(triarylmethanes) 7a–c was synthesized through Friedel–Crafts arylation reaction of the derived (oxy)benzaldehydes 9 with veratrole 10a under silicotungstic acid catalysis. On the other hand, employing compound 4 as a triarylmethane spacer for the synthesis of novel (oxy)benzaldehydes and related triarylmethanes expands the synthetic utility of TRAMs. This approach not only provides a new application for TRAMs but also opens up the possibility of indirect fluorination of triarylmethanes.

Zum Volltext