THE REACTION OF DEACTIVATED NAPHTHALENE D ERIVATIVES WITH SULFUR-TRIOXIDE

The reaction of sulfur trioxide with deactivated naphthalene derivativ es containing an electron withdrawing substituent, viz. -CHO, -COPh, - CO2H, and -CO(2)Me, in dichloromethane as the solvent has been studied by analysis of the resulting mixtures of the sulfo derivatives with H -1 NMR. Monosulfonation of 1-formylnaphthalene yields 5-S, 6-S, 7-S an d 8-S, in a 55 : 9 : 6 : 30 ratio, that of 1-benzoylnaphthalene 5-S, 6 -S and 7-S in a ratio of 83 : 11 : 6, and 1-nitronaphthalene only 5-S. 1-Naphthoic acid and its methyl ester upon SO, sulfonation and aqueou s work-up both yield 5- and 8-sulfonaphthoic acid in a ratio of 65 : 3 5 and 77 : 21 respectively. The initially formed peri substituted prod uct is the intramolecular anhydride of 8-sulfo-1-naphthoic acid. All t he 2-substituted naphthalenes upon SO3 sulfonation yield 5-S and 8-S.