A new method for the ring expansion of 1,3-dithiolanes and 1,3-dithianes to dihydro-1,4-dithiins and dihydro-1,4-dithiepines, respectively, using tert-butyl hypochlorite at room temperature is described. The salient features of the protocol include mild reaction conditions, very short reaction time, and high yield.The ring-expansion annelation reactions of 1,3-dithiolanes and 1,3-dithianes are very useful tools for the construction of larger rings bearing sulfur atoms and also for the 1,2 transposition of carbonyl compounds. 1 It has been reported that some 1,4-dithiins and 1,4-dithiepines show activity as non-peptidic antagonists of the human Galanin hGAL-1 receptor. 2 A review of the literature revealed a number of methods for the synthesis of 1,4-dithiin and 1,4-dithiepines. These methods include neutral or acid-catalyzed thermal rearrangement of 1,3-dithiolan-1-oxide 3 and reactions of 1,3-dithiolanes with ethyl N-chlorocarbamate. 4 In addition, ring expansion of 1,3-dithiolanes and 1,3-dithianes to the corresponding dihydro-1,4-dithiins and dihydro-1,4-dithiepines using reagents like 2,4,6-trichloro-1,3,5-triazine, 5 WCl 6 in the presence of DMSO, 6 TeCl 4 , 7 Br 2 /Cl 2 in anhydrous CCl 4 , 8 SO 2 Cl 2 , 9 and 1,3-dibromo-5,5-dimethylhydantoin 10 are also reported. Phenyl selenyl chloride has been employed for the ring expansion of some steroidal compounds. 11 Iranpoor et al. have reported extensive studies on the reaction of mono-substituted 1,3-dithiolanes and 1,3-dithianes with N-substituted succinimide resulting in ring enlargement. 11 Recently our research group also reported a ring expansion with IBX in the presence of TEAB. 13 Furthermore, almost all of the present protocols involve expensive, very toxic reagents and the yields are not satisfactory. In spite of the many reagents available, there is still scope for new reagents. Therefore the present tert-butyl hypochlorite based protocol is the first example that approaches the problem from the point of view of mild reaction conditions, inexpensive reagents, and also the absence of toxic waste disposal.tert-Butyl hypochlorite is a versatile reagent which has been applied to various transformation like oxidation of alcohols 14 and sulfides. 15 It can be easily prepared and is very cheap. Recently it has been applied to the regeneration of carbonyl compounds in the presence of iodine. 16 The initial reaction was carried with 2-(4-chlorophenyl)-2-methyl-1,3-dithiolane as a model substrate, which was treated with tert-butyl hypochlorite in CCl 4 at room temperature. The reaction proceeded smoothly with one equivalent of tert-butyl hypochlorite to produce the corresponding 1,4-dithiins in excellent yield as the only isolated product from the reaction mixture.The reaction was also carried out in other solvents and the results are given in Table 1.To study the generality of the reaction a variety of dithiolanes and dithianes were prepared using the standard literature procedure developed by Ong. 17 The 1,3-dithiolanes and 1,3-dithianes synthesized were then...