Friedel-Crafts alkylation and acylation of aromatic compounds under solvent free conditions using solid acid catalysts

Abstract

Solid acid catalysts, M(IV) Phosphotungstates [M(IV)PWs], mixed materials of the class of TMBA (Tetravalent Metal Bianionic Acid) salts and 12-Tungstophosphoric acid (12-TPA) supported onto M(IV) Oxides [M(IV) = Zr, Ti, Sn] have been synthesized and their utility towards Friedel–Crafts alkylation and acylation reactions has been explored and compared. The catalysts have been characterized for elemental analysis by ICP-AES, TGA, FTIR, SEM, EDX, XRD, surface area (BET) and surface acidity (NH3TPD). Friedel-Crafts alkylation and acylation have been studied as model reactions under solvent free conditions wherein acetyl chloride is used for acylation of anisole/veratrole and benzyl chloride is used for alkylation of toluene. Reaction conditions have been optimized by varying parameters such as reaction time, reaction temperature, catalyst amount and mole ratio of the reagents. Highlighting features are selectivity of products under solvent free conditions and regeneration/reuse of catalysts without much loss in % yields.