Potassium nitrosodisulfonate, Fremy's salt, (KSO₃)₂NO (Aldrich)

4-(Methylmercapto)phenol (Aldrich)

KH₂PO₄

A solution of KH₂PO₄ (10 g) in water (200 cm³) was mechanically stirred in a 2L round bottom flask and ice (200 g) added. The flask was cooled in ice-ethanol mixture and (KSO₃)₂NO (6 g, 22.4 mmol) added followed by a solution of 4-(methylmercapto)phenol (1.0 g, 7.1 mmol) in diethyl ether (20 cm³). After 1 m the solution was orange and after 5 m dark red. After 1 h the mixture was rotoevaporated at 20 ºC to remove the diethyl ether and extracted with chloroform (3 x 50 cm³). Evaporation gave a crimson solid (0.95 g, 86% yield), m.p. 92 ºC.

No attempt was made to optimise yields. This methylsulfanyl product was more stable than the ethers which were unstable short-lived products and which were reduced (Na₂S₂O₄) without delay to give the corresponding catechols in 34-87% yields Page xxx. 

Using the same method, the following 4-substituted o-benzoquinones were prepared:

CH₃O

CH₃CH₂CH₂O

CH₃CH₂CH₂CH₂O

CH₃CH₂CH₂S

CH₃CH₂CH₂CH₂S

HOCH₂CH₂S

δ_H (CDCl₃) 6.82dd (10.1, 2.4), 6.42dq (10.1, 0.5), 6.19d of qui (2.4, 0.5), 2.51d (0.5)

λ_max/nm (log ε) (H₂O), 330(3.77), 460 (3.42)

Teuber HJ, Chem. Rev., 1971, 71, 229