A ONE-STEP SYNTHESIS OF 5-HYDROXY-1,3-BENZOXATHIOL-2-ONES FROM QUINONES AND THIOUREA

A wide variety of 5-hydroxy-1,3-benzoxathiol-2-ones were prepared in excellent yields by a one-step synthesis from readily available quinones and thiourea. Depending on the nature of the substituents and the reaction conditions, the intermediate S-(2,5-dihydroxyaryl)thiouronium salts and 5-hydroxy-2-imino-1,3-benzoxathioles could also be readily isolated. Reactions of thiourea with unsubstituted, disubstituted, or trisubstituted quinone gave only one end product. However, monosubstituted quinones gave one or more of the three possible isomeric end products, the 4-, 6-, and 7-substituted 5-hydroxy-1,3-benzoxathiol-2-ones. The directive influence of the substituent groups on the addition of thiourea and their effect on the ease of cyclization of the resulting thiouronium salts are described. © 1968, American Chemical Society. All rights reserved.