Efficient synthesis of quinoxaline derivatives from the reaction of ?-diketones and o-phenylenediamines in the presence of Keggin-type heteropolyacids (HPA) such as H3PMo12O40, H4SiW12O40, K7PMo2W9O40, H3PW12O40.SiO2 and H3PW12O40 in high yields and short reaction times, and at room temperature is introduced.

Nano silica phosphoric acid (nano SPA) was applied as a catalyst for synthesis of 14-aryl/alkyl-14H-dibenzo[a,j]xanthenes and tetrahydrobenzo[a]xanthen-11-ones in microwave oven under solvent free conditions. High efficiency, easy availability and reusability are some advantages of this catalyst.

A rapid one-pot method has been developed for the synthesis of azo dyes via ?sequential diazotization–diazo coupling of aromatic amines with coupling agents at room ?temperature in the presence of BF3.SiO2 as acidic catalyst. The obtained aryl diazonium salts bearing silica supported boron tri-flouride counter ion? was sufficiently stable to be kept at room ?temperature in the dry state.?