MICROWAVE-ASSISTED SYNTHESIS OF BENZOFURAN ANALOGS OF FENAMATES AS NON STEROIDAL ANTI-INFLAMMATORY AGENTS

Abstract

A series of benzofuran analogs of anthranilic acid derivatives were easily synthesized by microwave irradiation and conventional heating method. The microwave irradiation method gives the comparable yield as that of conventional heating with a shorter reaction time. All the new compounds have been characterized by spectral data and screened for anti-inflammatory activity. Compounds containing benzofuran nucleus are widely distributed in nature amongst the plant kingdom. Such compounds are often associated with useful biological activities. This stimulated our interest in the synthesis of benzofuran analogs of anthranilic acid derivatives in which the benzene moiety of anthranilic acid is replaced by benzofuran moiety. Ethyl 3-hydroxybenzofuran-2-carboxylate was prepared by single pot synthesis15 from methyl salicylate and diethylbromo malonate served as key starting material for the synthesis of target molecules. The reaction of this with various aromatic amines in presence of catalytic amount of hydrochloric acid produced ethyl-3-arylaminobenzofuran-2-carboxylates. This needs heating of the reaction mixture for 90-950C for 9 hrs. This is a very time consuming reaction. The same reaction mixture when irradiated in microwave for different period of time at 500 W power gives the desired product. As compared to conventional heating method the microwave irradiation method for synthesis of ethyl -3-arylaminobenzofuran-2-carboxylates is simple and less time consuming. As this reaction does not involve use of any solvents so there is no any risk of explosion of the solvents during microwave irradiation. EXPERIMENTAL Melting points were determined in open capillary tubes and are uncorrected. The FT-IR spectra were recorded in KBr on SHIMADZU FTIR-8400S spectrophotometer. 1H NMR spectra were recorded in CDCI 3 on a Varian Mercury YH-300, using TMS as an internal standard. Microwave irradiations were carried out in a LG intellocook MS-1921HE with RF output of 700W. SCHEME