ON THE POSITIONAL REACTIVITY ORDER IN THE SULFONATION OF PHENYL-SUBSTITUTED AND NAPHTHYL-SUBSTITUTED NAPHTHALENES WITH SO3

Abstract

The sulfonation of 1- and 2-phenylnaphthalene, 1,1'- and 2,2'-binaphthyl, and that of the 2,2'-dihydroxy, 2,2'-dimethoxy and 2,2'-dimesyloxy derivatives of 1,1'-binaphthyl with SO3 in dichloromethane as solvent was studied at 22 +/- 2-degrees-C. Sulfonation of 1-phenylnaphthalene and 1,1'-binaphthyl leads to substitution at (each of) the alpha-naphthyl moieties, initially at the 4-position and subsequently at the 6- and 7-position, in a ratio of approximately 8:92 and 14:86, respectively. Upon sulfonation the more planar 2-phenylnaphthalene and 2,2'-binaphthyl both give initially the 8-sulfonic acid derivative (8-S) and subsequently a mixture of 8,4'-S2 and 8,8'-S2, respectively; their further sulfonation affords mixtures of the 4,8,4'-S3 + 6,8,4'-S3 and of the 4,8,8'-S3 + 6,8,8'-S3, respectively, both in an isomer ratio of approximately 19:81. Sulfonation of 2,2'-dimethoxy-1,1'-binaphthyl gives initially the 3-S and 6-S derivatives in an isomer ratio of approximately 13:87 subsequently the 3,6'-S2 and 6,6'-S2 derivatives and eventually the 3,6,4',6'-S4 and 4,6,4'6'-S4 derivatives. Monosulfonation of 2,2'-dimesyloxy-1,1'-binaphthyl gives the 5-S and 6-S in a ratio of 58:42. With a large excess of SO3, 4,6,4',6'-S4, 4,6,5',7'-S4 and 5,7,5',7'-S4 are eventually formed. Sulfonation of 2,2'-dihydroxy-1,1'-binaphthyl gives initially the 5-S and 6-S, the ratio of which increases upon increasing the amount of SO3 employed from approximately 35:65 on using less-than-or-equal-to 1.0 mol-equiv. of SO3 to approximately 62:38 on using > 6.0 mol-equiv. of SO3. Under the latter conditions the substrate species undergoing sulfonation is proposed to be the di-sulfated species 3.