NOVELTY - Improved process for preparation of substantially pure 2-ethoxy-1-((2'-(2,5-dihydro-5-oxo-1,2,4-oxadiazol-3-yl)biphenyl-4-yl)methyl)benzimidazole-7-carboxylic acid (azilsartan) (I) comprises e.g. : (b) condensation of methyl-2-ethoxy-1-((2'-((hydroxycarbamimidoyl)biphenyl)-4-yl)methyl)-1H-benzimidazole-7-carboxylate (III) with ethyl chloroformate followed by cyclization in presence of e.g. low boiling organic solvent to get methyl 2-ethoxy-1-((2'-(2,5-dihydro-5-oxo-1,2,4-oxadiazol-3-yl)biphenyl-4-yl)methyl)benzimidazole-7-carboxylate (IV); and (c) hydrolysis of (IV) followed by pH adjustment.    USE - The process is useful for preparing (I) which is useful for preparing azilsartan medoxomil (claimed) and for treating hypertension. No biological data given.    ADVANTAGE - The process provides: (I) that has a purity of more than 99.93% (preferably 99.95%), desethyl impurity less than 0.05% (preferably 0.03%) measured as area percentage by HPLC (all claimed); and is efficient, commercially viable and facile synthesis for the preparation of pure intermediates of azilsartan using eco-friendly, cheaply available reagents and low boiling solvents.    DETAILED DESCRIPTION - Improved process for the preparation of substantially pure 2-ethoxy-1-((2'-(2,5-dihydro-5-oxo-1,2,4-oxadiazol-3-yl)biphenyl-4-yl)methyl)benzimidazole-7-carboxylic acid (azilsartan) of formula (I), comprises: (a) reacting 3-(2'-cyano-biphenyl-4-ylmethyl)-2-ethoxy-3H-benzoimidazole-4-carboxylic acid methyl ester of formula (II), with hydroxylamine or its salt in presence of a solvent and a phosphate salt followed by purification (optional) to produce methyl-2-ethoxy-1-((2'-((hydroxycarbamimidoyl)biphenyl)-4-yl)methyl)-1H-benzimidazole-7-carboxylate of formula (III); (b) condensation of (III) with ethyl chloroformate followed by cyclization in presence of a low boiling organic solvent and a base to give methyl 2-ethoxy-1-((2'-(2,5-dihydro-5-oxo-1,2,4-oxadiazol-3-yl)biphenyl-4-yl)methyl)benzimidazole-7-carboxylate of formula (IV); (c) hydrolysis of (IV) followed by pH adjustment of aqueous product layer with an organic acid; and (d) purification of obtained compound in a mixture of organic solvents followed by the treatment with an alcoholic solvent to yield pure (I). An INDEPENDENT CLAIM is also included for substantially pure compound of (I) having purity more than 99.9% and desethyl impurity less than 0.05% measured as area percentage by HPLC.