Salicylaldehyde → 2-(4-Chloro-trans-2-butenyloxy)-benzaldehyde

To 2 lt of refluxing water, 3 ml of 40% aqueous tetrabutylammonium hydroxide, 250 ml of salicylaldehyde and 280 ml of trans-1,4-dichloro-2-butene are added while vigorously stirring, followed by the dropwise addition of the solution of 83 g of sodium hydroxide in 400 ml of water at such a rate that the pH of the mixture is kept between 7 and 8 (ca 25 minutes). Thereafter the mixture is refluxed for about 6 minutes until the pH is about 7, cooled to 20° and the aqueous layer is extracted with diethyl ether. The extract is combined with the organic layer, washed with 5% aqueous sodium hydroxide, dried, evaporated, the residue distilled and the fraction boiling at 141°-147°/0.7 mmHg collected, to yield the 2-(4-chloro-trans-2-butenyloxy)-benzaldehyde.