Oxidation of Thiols to Disulfides
43
filtration and dried at 135ꢀC for 4 hours after which it can be reused (Table 2). The
greatest advantages of this procedure arise from the employment of molecular
oxygen or air and from reusability of the catalyst.
Experimental
Products were characterized by comparison of their physical and spectroscopic data with those of
authentic samples. All yields refer to isolated products after column chromatography. IR and NMR
spectra were recorded on Perkin Elmer 781 and Bruker DPX500 instruments. The progress of the
reaction was monitored by TLC. Co(II) and Mn(II) salts of 4-aminobenzoic acid supported on silica
gel were prepared according to Hashemi et al. [15–19].
Typical Procedure for the Oxidation of Thiols to Disulfides
To a stirred solution of 110 mg of thiophenol (1mmol) in 25cm3 of n-hexane was added 0.46g of
supported Co salt (0.5mmol Co) and 0.45 g of Mn salt (0.5mmol Mn). The reaction mixture was
refluxed for 1 h while oxygen was bubbled through the solution at a rate of 15cm3=min. The reaction
mixture was cooled to room temperature and then filtered to recover the solid material (Co and Mn
salts). The solid material was washed with 20cm3 of n-hexane. The solvent was evaporated and the
product was purified by column chromatography (n-hexane) on silica gel. The pure diphenyl disulfide
was obtained in 96% yield (105mg, mp 59–61ꢀC, Ref. [10] 58–61ꢀC). This experiment was also
repeated using air instead of oxygen at a rate of 40cm3=min (see Table 1).
References
[1] Jocelyn PC (1977) Biochemistry of the Thiol Groups. Academic Press, New York
[2] Firouzabadi H, Iranpoor N, Parham HA (1984) Synth Commun 14: 717
[3] a) Firouzabadi H, Naderi M, Sardarian A, Vessal M (1983) Synth Commun 13: 611; b) Noureldin
NA, Caldwell M, Hendry J, Lee DG (1998) Synthesis 1587
[4] Wallace TJ (1966) J Org Chem 31: 1217
[5] Firouzabadi H, Iranpoor N, Kiaeezadeh F, Toofan J (1986) Tetrahedron 42: 719
[6] Mc Killop A, Koyuncu D (1990) Tetrahedron Lett 31: 5007
[7] Ramesha AR, Chandrasekaran S (1994) J Org Chem 59: 1354
[8] Ramadas K, Srinivasan N (1995) Synth Commun 25: 227
[9] Pryor WA, Church DF, Gorindan CK, Crank G (1982) J Org Chem 47: 156
[10] Iranpoor N, Firouzabadi H, Zolfigol MA (1998) Synth Commun 28: 367
[11] a) Wu X, Rieke RD (1996) Synth Commun 26: 191; b) Ali MH, McDermott M (2002)
Tetrahedron Lett 43: 6271
[12] Liu KT, Tong YC (1978) Synthesis 664
[13] Iranpoor N, Zeynizadeh B (1994) Synthesis 49
[14] Rao TV, Rao KN, Jain SL, Sain B (2002) Synth Commun 32: 1151
[15] Hashemi MM, Ghazanfari D (1995) Iran J Chem Chem Eng 13: 77
[16] Hashemi MM, Beni YA (1998) J Sci I R I 9: 237
[17] Hashemi MM, Beni YA (1998) J Chem Research (S) 138
[18] Hashemi MM, Kalantari F (2000) Synth Commun 30: 1857
[19] Hashemi MM, Ahmadibeni Y (2003) Monatsh Chem 134: 411