To a solution of 3-bromo-5-isopropoxy-benzoic acid (2.0 g, 8.26 mmol) in THF (30 ml) was added 1.6 M nBuLi (10.6 ml, 16.94 mmol) at −78° C. The reaction was stirred at −78° C. for 1 h and treated with a solution of (5-formyl-thiophen-2-yl)-phosphonic acid diethyl ester (2.5 g, 9.91 mmol) in THF. After stirring at −78° C. for 30 min, the reaction mixture was warmed up to r.t. and quenched by water, diluted with EtOAc. The aqueous layer was separated, acidified with 2N HCl to pH<1, and extracted with EtOAc (3×). The combined EtOAc layers were dried over MgSO4, filtrated, concentrated to give the crude product 3-{[5-(diethoxy-phosphoryl)-thiophen-2-yl]-hydroxy-methyl}-5-isopropoxy-benzoic acid.
