Crushed potassium hydroxide (1.15 g) and tetrabutyl ammonium chloride (0.61 g) are added to a solution of the product obtained in Step 3. (4.8 g) in 1,3-dibromopropane (21 ml). The reaction mixture is stirred under nitrogen at RT for 48 hours, diluted with diethyl ether, washed with water and extracted into 5% aq. HCl. The aqueous solution is washed with ether and made alkaline yielding a yellow oil which is taken up in ether, washed, dried, filtered and evaporated to give the desired product as an oil.
