Reactions of sulfur trioxide with benzene derivatives containing a deactivating oxy substituent

✍ Scribed by Harold R. W. Ansink; Hans Cerfontain

• Book ID: 104589413
• Publisher: Elsevier Science
• Year: 2010
• Tongue: English
• Weight: 587 KB
• Volume: 111
• Category: Article
• ISSN: 0165-0513
• DOI: 10.1002/recl.19921110503

✦ Synopsis

Abstract

The reactions of phenyl acetate (2), (trifluoromethoxy)benzene (3), (difluoromethoxy)‐benzene (4), 4‐(trifluoromethoxy)phenol (5), 4‐(trifluoromethoxy)phenyl methanesulfonate (6), 4‐(trifluoromethoxy)anisole (7) and 3‐(trifluoromethoxy)anisole (8) with SO~3~, in nitromethane have been studied. Upon reaction with SO~3~, 2 yields 2‐4‐sulfonic acid (2‐4‐S); subsequently, transfer of the acetyl group takes place to yield the mixed anhydride of phenol‐4‐pyrosulfonic acid and acetic acid (9) or the corresponding hydrogen sulfate 10, depending on the amount of SO~3~, used. Reaction of the α‐fluorinated anisoles 3 and 4 with SO~3~ leads to sulfonation at the 4‐position only; however, on using both a high substrate concentration and an excess of SO~3~, some 2,4‐S~2~, is formed with 4 but not with 3.

On reaction of 5 with 0.8 mol‐equiv of SO~3~, in C~2~H~3~NO~2~, the hydrogen sulfate derivative (5‐O‐S) is formed; at 100°C, some isomerization to 5‐2‐S occurs. Upon reaction with 4.0 mol‐equiv of SO~3~, the initially formed hydrogen sulfate slowly yields the corresponding 2‐sulfophenyl hydrogen sulfate (5‐O,2‐S~2~). On using 6.0 mol‐equiv of SO~3~, the 5‐O,2‐S~2~ is slowly converted into 6‐(trifluoro‐methoxy)benzo‐1,3,2,4‐dioxadithiin 2,2,4,4‐tetraoxide (11). Reaction of 6 with either 0.9 or 3.0 mol‐equiv of SO~3~, initially leads to insertion of sulfur trioxide in between the SO~2~CH~3~, and the adjacent O, yielding the 4‐(trifluoromethoxy)phenyl methanepyrosulfonate 12. This species subsequently yields 13 and 14. Reaction of 7 with SO~3~ leads to sulfonation only at the 2‐position; eventually some sulfodemethylation to yield 5‐2‐S takes place. Reaction of 8 with 1.0 mol‐equiv of SO~3~, yields a 68: 32 mixture of 8‐4‐S and 8‐6‐S.