Taming of superacids: PVP-triflic acid as an effective solid triflic acid equivalent for Friedel–Crafts hydroxyalkylation and acylation

• Published in: Journal of fluorine chemistry 2015-03, Vol.171, p.102-112
• Main Authors: Prakash, G.K. Surya, Paknia, Farzaneh, Kulkarni, Aditya, Narayanan, Arjun, Wang, Fang, Rasul, Golam, Mathew, Thomas, Olah, George A.
• Format: Article
• Language: English
• Subjects: Acylation; Hydroxyalkylation; PVP:triflic acid; Solid superacid; Trifluoromethanesulfonic acid
• ISSN: 0022-1139; 1873-3328
• DOI: 10.1016/j.jfluchem.2014.08.020

PVP-TfOH, prepared from poly(4-vinylpyridine) and triflic acid, acts as a covenient solid equivalent of triflic acid and used efficiently as superacid catalyst in the Friedel–Crafts hydroxyalkylation and acetylation of arenes as well as Fries rearrangement. Direct synthesis of a wide variety of diarylacetic acid derivatives was achieved by the hydroxyalkylation of arenes with glyoxylic acid under mild conditions. •Poly(4-vinylpyridine)-triflic acid complex, a solid triflic acid equivalent was prepared.•Friedel–Crafts hydroxyalkylation and acetylation of arenes were investigated.•Facile synthesis of diary acetic acid derivatives in high yields was achieved. The application of poly(4-vinylpyridine) supported trifluoromethanesulfonic acid (PVP-TfOH, 1:10) as a convenient solid superacid catalyst system in Friedel–Crafts reactions is described. In the presence of PVP-TfOH, one pot solvent-free synthesis of a wide variety of diarylacetic acid derivatives was achieved by Friedel–Crafts hydroxyalkylation reaction of glyoxylic acid with arenes under mild conditions. Acylation of both activated and deactivated aromatic compounds with acetyl chloride was also achieved using PVP-TfOH complex under solvent-free conditions at room temperature. As the polymer supported triflic acid was found to be a very efficient and an easy-to-handle solid acid, it can be a useful addition to environmentally more adaptable strong acid catalyst systems.