Nitric Acid Mediated Oxidative Transformation of Thiols to Disulfides

Abstract

Oxidation of thiols to disulfides are reported using nitric acid/methylene chloride. Environmentally benign, economically convenient and simple reaction condition represents an attractive alternative to the existing approaches on both the laboratory and the industrial scale.

^#C.D.R.I. Communication No: 6412.

Keywords:

• Nitric acid
• Oxidation
• Thiols
• Disulfides

Acknowledgments

The authors thank Director, Central Drug Research Institute (CDRI) for his constant encouragement and support.

Notes

^#C.D.R.I. Communication No: 6412.

^aAll compounds were characterized by their spectral analysis (NMR, MS and IR). ¹H NMR of unknown disulfides: 2,2′‐Dimethylcarbonyldiphenyl‐disulfide (entry 6): δ 8.04 (d, 2H), 7.76 (d, 2H), 7.40 (t, 2H), 7.19 (t, 2H), 3.98 (s, 6H); FABMS [M + 1] for C₁₆H₁₄O₄S₂: 335.0 (calcd), 335.0 (found). Di‐(3,4‐dimethylbenzyl)disulfide (entry 7): δ 7.65‐7.35 (m, 6H), 3.79 (2s, 4H), 2.35 (2s, 12H); FABMS [M + 1] for C₁₈H₂₂S₂: 303.0 (calcd), 303.0 (found). Di‐(4‐nitrobenzyl) disulfide (entry 8): δ 8.21 (d, 4H), 7.55 (d, 4H), 3.70 (s, 4H); FABMS [M + 1] for C₁₄H₁₂N₂O₄S₂: 337.0 (calcd), 337.0 (found). Bis‐(1‐phenyl‐1H‐tetrazolyl‐5,5′)‐disulfide (entry 9): δ 7.77 (m, 4H), 7.31 (m, 6H); FABMS [M + 1] for C₁₄H₁₀N₈S₂: 355.0 (calcd), 355.0 (found). Di‐(4‐methoxybenzyl)disulfide (entry 11): δ 7.0‐7.3 (m, 8H), 3.78 (2S, 6H, 2OCH ₃), 3.72 (2s, 4H, 2CH ₂Ph); FABMS [M + 1] for C₁₆H₁₈O₂S₂: 307.0 (calcd), 307.0 (found). Dioctyldisulfide (entry 14): δ 2.52 (bt, 4H), 1.30 (m, 24H), 0.90 (t, 6H); FABMS [M + 1] for C₁₆H₃₄S₂: 291.0 (calcd), 291.0 (found).