37 u00b0 c see fig2 one equivalent of 1n naoh is added to an ethanolic solution of montelukast 1a obtained in the previous step c the solvent is evaporated and water is added to the resulting residue till a solution is obtained the resulting solution is concentrated to dryness with a rotatory evaporator at 50 u00b0 c resulting in the isolation of compound 1b ethyldiisopropylamine 45 09 ml was added to a stirred solution of 2 2 3 s 3 1e 2 7 chloroquinoline 2 yl ethenyl phenyl 3 hydroxypropyl phenyl 2 propanol 2 100 42 g 99 58 purity 218 mmol in tetrahydrofurane 200 ml kept at room temperature under nitrogen the resulting brown solution was cooled at u2212 22 5 u00b1 2 5 u00b0 c with an acetone dry ice bath methanesulfonyl chloride 19 65 ml was slowly added over 15 min using an addition funnel while the temperature of the solution was kept at u2212 22 5 u00b1 2 5 u00b0 c the resulting viscous dark brown solution was kept at this temperature for an additional hour acetonitrile 600 ml was slowly added over 1 hour and 25 min while the temperature was kept at u2212 22 5 u00b1 2 5 u00b0 c resulting in the precipitation of a solid the resulting suspension was kept at u2212 22 5 u00b1 2 5 u00b0 c for 2 additional hours and the mixture was filtered under nitrogen the solid was washed with a small amount of cold acetonitrile.