Oxidation of thiols to disulfides with monochloro poly(styrenehydantoin) beads Akin Akdag, Thomas Webb and S. D. Worley * Auburn University, Department of Chemistry and Biochemistry, Auburn, AL 36849, United States Received 1 March 2006; accepted 15 March 2006 Available online 5 April 2006 Abstract—Various thiols were converted to symmetrical disulfides. This facile and reproducible method uses water as a solvent, and monochloro poly(styrenehydantoin) beads as an oxidizing agent. Ó 2006 Elsevier Ltd. All rights reserved. Disulfide bonds play crucial roles in biology and chemis- try. 1 Disulfides are primarily produced from thiols, which are readily available and facile to prepare. 2 How- ever, synthesis of disulfides from thiols sometimes can be problematic due to the overoxidation of thiols, that is, the reaction not terminating at the disulfide stage and proceeding further to sulfoxides and sulfones. 3 On the other hand, many successful reagents have been devel- oped for the synthesis of disulfides from thiols; for exam- ple, 1,3-dibromo-5,5-dimethylhydantoin, cerium (IV) salts, permanganates, transition metal oxides, sodium chlorite, peroxides, and halogens are examples of reagents used in disulfide bond formation from thiols. 4 In this study, which was prompted by the need to iden- tify products from the use of a convenient oxidizing agent to remove noxious odor from cutting oil fluids, we have employed monochloro poly(styrenehydantoin) beads 5 in water to form disulfides from thiols. 6 Previ- ously, Sun and Worley had reported that an amorphous form of the dichloro derivative oxidized aryl sulfides to the sulfoxides and the sulfones. 5d The beads did not over- oxidize the thiols; the sole product isolated from these experiments was disulfides. This was because the dis- sociation constant for amide N-halamine in water to produce free chlorine is very low. 7 Presumably, the reactions proceed through halogen transfer from amide N-halamine to thiols to yield sulfenyl chlorides, which react with thiolate anion to yield disulfides and hydro- chloric acid (see Scheme 1). The proposed mechanism is in agreement with the experimental observation that water becomes acidic at the end of the reaction, as well 0040-4039/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.tetlet.2006.03.105 * Corresponding author. Tel.: +1 334 844 6944; fax: +1 334 844 6959; e-mail: worlesd@auburn.edu N N O O H Cl n RS-H + N N O O H H n RS-Cl + RS-H + H + RS-Cl RS-SR + + RS - RS - Cl - Scheme 1. Proposed mechanism for formation of a disulfide from a thiol. Tetrahedron Letters 47 (2006) 3509–3510