282 ISSN 1070-3632, Russian Journal of General Chemistry, 2007, Vol. 77, No. 2, pp. 282 284. Pleiades Publishing, Ltd., 2007. Original Russian Text H. Imanieh, S. Ghamami, M.K. Mohammadi, A. Jangjoo, 2007, published in Zhurnal Obshchei Khimii, 2007, Vol. 77, No. 2, pp. 310 312. Oxidation of Some Organic Thiols with Tetramethylammonium Fluorochromate(VI) H. Imanieh a , S. Ghamami a , M. K. Mohammadi b , and A. Jangjoo c a Department of Chemistry, Faculty of Science, Imam Khomeini International University, Qazvin, Iran b Department of Chemistry, Faculty of Science, Islamic Azad University of Sciences & Researching, P.O. Box 14155/775, Tehran, Iran; e-mail: m_k_mohammadi@yahoo.com c Firouzabad Branch, Islamic Azad University, Firouzabad, Iran Received February 20, 2006 Abstract Tetramethylammonium fluorochromate oxidizes alcohols to the corresponding aldehydes and ketones without polymerization of double bonds, overoxidation, and other side reactions. This reagent is effective for oxidation of thiols to disulfides. DOI: 10.1134/S1070363207020156 The oxidation of thiols to disulfides [1] or to sul- fonic acids [2] in the absence and presence of catalysts has been the subject of several recent studies. Atten- tion has been focused primarily on the range of pro- ducts that can be obtained depending on the reaction conditions. In general, the reaction seems to lead to the almost exclusive formation of disulfides when oxidation occurs in aqueous solution, and to a variety of disulfides and sulfenic, sulfinic, and sulfonic acids when carried out in nonaqueous solutions [3]. In both cases, the reaction has been suggested [4] to involve initial formation of a disulfide, followed by its hydrolysis to yield sulfur-containing acids. Much attention was given recently to chromium-based oxi- dizing agents. Some of which have become quite popular and effective, e.g., the Collins reagent [5], chromium trioxide 3,5-dimethylpyrazole complex [6], pyridinium chlorochromate [7], pyridinium fluoro- chromate [8], and quinolinium bromochromate [9]. As a part of our effort to develop [10] new methodo- logies in economically viable and environmentally benign conditions, we report here a very simple oxi- dative protocol using tetramethylammonium fluoro- chromate at room temperature in acetonitrile as a solvent. Tetramethylammonium fluorochromate has a number of advantages over the conventional oxidation reagents in various organic solvents. A number of aliphatic, aromatic, and allylic thiols were subjected to oxidative transformation with tetra- methylammonium fluorochromate in a solvent. Quite interestingly, both aliphatic [11] and allylic primary thiols gave the corresponding disulfides under mild conditions without detectable (by 300 MHz 1 H NMR) amounts of the sulfones or sulfonic acids. As seen from the table, saturated aliphatic acyclic and allylic thiols underwent clean oxidation with tetramethylammonium fluorochromate to the corres- ponding disulfides at ambient temperature within a reasonable period of time in the presence of aceto- nitrile as a solvent in good yield and with high prod- uct purity. This can be attributed mainly to the im- mobilization of the Cr-containing by-products in the solvent [12]. The overall reaction can be represented as R S H + (CH 3 ) 4 N + CrO 3 F R S S R + (CH 3 ) 4 N + CrO 2 F. Tetramethylammonium fluorochromate undergoes two-electron reduction. This is in agreement with our previous observations with other halochromates. No overoxidation was noted even with an excess of the reagent. The reaction of aromatic thiols was essentially insensitive to substitution of the aromatic ring, but possibly depended on the solvent used. The reaction conditions have the advantages of leaving unchanged a chiral amino acid group. The notable feature of our procedure is elimination of several side reactions typical of various conven- tional oxidative methods using high-valence metals as oxidants [13]. 1,2-Diols and -hydroxy ketones have been reported to undergo oxidative cleavage of the CC bond with tetramethylammonium fluoro- chromate in dichloromethane, but under solvent- free conditions these substrates cleanly produce the desired oxidation products, namely, 1,2-diketones in reasonable yield without appreciable formation of by- products. Allylic primary thiols smoothly underwent