The order of addition of the reagents of the Mitsunobu reaction can be important. Typically, one dissolves the alcohol, the carboxylic acid, and triphenylphosphine in tetrahydrofuran or other suitable solvent (e.g. diethyl ether), cool to 0 °C using an ice-bath, slowly add the DEAD dissolved in THF, then stir at room temperature for several hours. If this is unsuccessful, then preforming the betaine may give better results. To preform the betaine, add DEAD to triphenylphosphine in tetrahydrofuran at 0 °C, followed by the addition of the alcohol and finally the acid.
