Structure of products from reactions of phosphorus pentachloride with phenyl salicylate and 2-hydroxybenzophenone; related compounds. p31 N.M.R. and chemical studies

The compounds obtained from the reactions of phenyl salicylate and 2-hydroxybenzo-phenone with phosphorus pentachloride have been shown to have structures I A and II A, respectively, rather than alternative heterocyclic structures on the basis of the comparison of the P31 chemical shifts with appropriate reference compounds and additional chemical evidence. Compound I reacts with two equivalents of phenol in the presence of two equivalents of triethylamine to form mainly compound VIII (substitution on phosphorus). Structure VIII is confirmed via P31 n.m.r. and IR spectra and the fact that partial hydrolysis forms the same compound (VII) that is obtained from the reaction of compound III with phenol (only phosphorus substitution possible). A mechanism with initial reaction of phosphorus pentachloride (as tetrachlorophosphonium ion) on the phenolic hydroxyl is postulated on the basis of the available evidence. The P31 chemical shifts for compounds XIV A and XV A confirm these structures as heterocyclic in accord with previous chemical evidence. Structure XIV A is of historical importance as one of the first three cyclic structures ever published in the classical paper in which Couper announced his structural theory of organic chemistry.