Korean J. Chem. Eng., 20(2), 235-238 (2003) 235 † To whom correspondence should be addressed. E-mail: wei_xianyong@yahoo.com.cn ‡ This paper is dedicated to Professor Baik-Hyon Ha on the occasion of his retirement from Hanyang University. Convenient Synthesis of N-Methylpyrrolidine-2-thione and Some Thioamides Zhi-Min Zong, Yao-Li Peng, Zhi-Gang Liu, Shi-Lu Zhou, Lin Wu, Xiao-Hua Wang, Xian-Yong Wei † and Chul Wee Lee* Department of Applied Chemistry, School of Chemical Engineering, China University of Mining and Technology, Xuzhou 221008, Jiangsu, China *Advanced Chemical Technology Division, Korea Research Institute of Chemical Technology, P.O. Box 107, Yusung, Daejeon 305-600, Korea (Received 2 October 2002 • accepted 14 November 2002) Abstract -The synthesis of thioamides and thiolactams, which are used as important organic intermediates, has at- tracted great attention. However, expensive reagents, severe reaction conditions and low yields of the target products made conventional methods inconvenient and economically infeasible. To overcome these disadvantages, we investi- gated a new process for synthesizing thioamides and thiolactams. We examined thermal reactions of CS 2 with N- methyl-2-pyrrolidinone, formylamide, acetamide and N,N-dimethylformylamide, respectively. The results show that under optimum conditions N-methylpyrrolidine-2-thione and the corresponding thioamides can be obtained in good to excellent yields by the above thionation reactions. Key words: CS 2 , Amides, Thionation, N-Methylpyrrolidine-2-thione, Thioamides INTRODUCTION Much work has been directed towards the synthesis of thioam- ides and thiolactams because of their importance as synthetic inter- mediates [Lubosch and Seebach, 1980; Borthakur and Goswami, 1995], a medium in CO 2 sensor [Yamaguchi et al., 1986] and ligands for a variety of complexes [Rechberger and Gritzner, 1978; Senyel and Kurkcuoglu, 2001; Dunstan, 2002]. P 4 S 10 was widely used as a thionating reagent for the synthesis of thioamides [Hurd and DeLaMeter, 1961] from amides. Conven- tional experiments were conducted by refluxing an amide with ex- cess P 4 S 10 in a solvent, usually requiring a large excess of P 4 S 10 and prolonged time. Raucher and Klein improved the procedure by ul- trasonic irradiation [Raucher and Klein, 1981]. Harpp and Mac- Donald investigated the reactions of 1,1’-thiocarbonyldiimidazole and 1,1’-thiocarbonylbis(1,2,4-triazole) with some aldonitrones [Harpp and MacDonald, 1983]. Although thioamides can be obtained in good yields (67-75%), use of expensive heterocyclic thiocarbonyl transfer reagents makes the reaction difficult in practical applica- tions. Thioamides and thiolactams were also synthesized by using Lawesson reagents [Thomsen et al., 1984; Xie and Lightner, 1991; Sakamoto et al., 2000; Olsson et al., 2000] and by the reactions of thiuram monosulfides with organolithium derivatives [Gronowitz et al., 1993] and of carboxylic acids and amines with O, O-diethyl di- thiophosphoric acid [Borthakur and Goswami, 1995]. These meth- ods, however, still require expensive thionating reagents. Taking the disadvantages of previous synthetic procedures into account, we used CS 2 as a thionating reagent for the synthesis of thioamides and thiolactams from amides and lactams. Here we re- port our results about the synthesis of N-methylpyrrolidine-2-thione (MPT), thioformamide (TFA), thioacetamide (TAA) and N, N-di- methylthioformamide (DMTFA) by thermal reactions of CS 2 with N-methyl-2-pyrrolidinone (MP), formamide (FA), acetamide (AA) and N, N-dimethylformamide (DMFA), respectively. EXPERIMENTAL 1. Chemicals CS 2 , MP, FA, AA and DMFA were reagent grade and purchased from Aldrich Chemical Company, Inc. 2. Reactor and Analytical Instruments A 100 mL stainless steel, magnetically stirred autoclave was used as a reactor for all the reactions. Analytical instruments included a Hewlett Packard 6890/5973 GC/MS, a Hewlett Packard 6890/Ni- colet Magna IR-560 GC/FTIR and a Hewlett Packard 6890 GC with FID. 3. Reaction and Analysis Procedures Prescribed amounts of CS 2 and MP (5 mL) or an amide (5 mL) were put into an autoclave. After being pressurized with nitrogen to 5 MPa at room temperature, the autoclave was heated to an in- dicated temperature within 10 min and kept at the temperature for a prescribed period of time. Then the autoclave was immediately cooled to room temperature in an ice-water bath. After being taken out from the autoclave, the reactants and products were identified with GC/MS and GC/FTIR and quantified with GC. Scheme 1. Mechanism for MPT formation from thermal reaction of MP with CS 2 .