Facile and Selective Mono Benzylation of Naphthalene Using Atom Efficient Chloroaluminate Ionic Liquid

Benzyl naphthalenes are versatile compounds having multiple applications in dyes, fine chemicals, and pharmaceuticals etc. Herein, we present benzylation of naphthalene with benzyl chloride using a chloroaluminate ionic liquid which we have reported recently. The catalyst is highly active, selective and required in very low quantity i.e., 0.5% w/w to drive the reaction. The reaction was carried out at ambient temperature and pressure which has an edge over other existing catalysts that requires elevated temperature. The conversion of benzyl chloride and selectivity toward mono-benzylated product was found to be more than 95% and 90%, respectively. The formation of the product was confirmed by GC-MS. Various reaction parameters like temperature, catalyst concentration, mole ratio of benzyl chloride and naphthalene were investigated to optimize the best operating conditions to obtain the mono benzylated naphthalene. The catalyst was efficiently recyclized up to 5 times. The easy single-step synthesis of the catalysts, use of hydrophobic neutral ligand, better atom economy, makes the process more attractive for its application in benzylation reaction of naphthalene.

Automated summary

This paper presents a method for the benzylation of naphthalene using a chloroaluminate ionic liquid as a catalyst. The method offers a highly active catalyst, low temperature and pressure reaction conditions, and high selectivity, making it significant for the synthesis of mono-benzylated naphthalenes.