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.

2,4,5-Trisubstituted imidazoles have many pharmaceutical properties and can be prepared via reaction of 1, 2-diketones with aldehydes in the presence of an acidic catalyst. In this work, we have prepared 2,4,5-trisubstituted imidazoles in the presence of trichloromelamine as a source of positive chlorine. Short reaction times, high yield, simplicity of operation and easy work-up are some advantages of this method.

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.?