A. K. Brel, S. V. Lisina, Yu. N. Budaeva
Oct 21, 2015
Citations
0
Influential Citations
3
Citations
Journal
Russian Journal of General Chemistry
Abstract
First, we prepared 4-hydroxybenzoyl chloride 2 from 4-hydroxybenzoic acid 1. Carboxylic acid chlorides are generally prepared via the reaction of thionyl chloride with the corresponding carboxylic acid. A serious drawback of this method is the requirement of high purity of thionyl chloride: it should always be additionally purified prior to use. Furthermore, the reaction should be carried out upon slight boiling at 30°C; overheating or cooling would reduce the product yield and purity. In the case of hydroxybenzoic acid, the excess of thionyl chloride is usually distilled off to afford the crude hydroxybenzoyl chloride that is introduced in further reactions without purification [8] to avoid the product decomposition. Isolation of pure hydroxybenzoyl chloride requires multiple purification stages, since the product as-prepared via the thionyl chloride method contains 1–2% of organosulfur compounds formed via the side reaction of thionyl chloride with phenolic hydroxy group of hydroxybenzoic acid [9]. Such product contamination is a serious problem as far as preparation of biologically active compounds and drugs is concerned [7]; moreover, it significantly reduces the yield of the target product in the case of multi-stage synthesis. The mentioned drawbacks could be overcome by using oxalyl chloride [10] instead of thionyl chloride. The latter method has afforded hydroxybenzoyl chloride in high yields (up to 91%) and free of the sulfur-containing admixtures.