48 J. CHEM. RESEARCH (S), 1998 J. Chem. Research (S), 1998, 48–49† Reductive Cleavage of the S–Si Bond in Arylsulfanyltrimethylsilanes: a Novel Method for the Synthesis of Unsymmetrical Sulfides† Songlin Zhang and Yongmin M. Zhang* Department of Chemistry, Hangzhou University, Hangzhou, 310028, P. R. China Arylsulfanyltrimethylsilanes are reduced by samarium diiodide to yield samarium arylthiolates which react with alkyl halides to give unsymmetrical sulfides. The application of samarium diiodide in organic synthesis has received increasing attention in the last decade.1–3 It is a powerful one-electron transfer reductant. We have reported the reductive cleavage of S–S bonds with SmI2.4 Recently, we have considered that the S–Si bond might be also reduced with samarium diiodide.Since organic sulfur compounds have become increasingly useful and important in organic synthesis,5,6 convenient preparations of appropriate sulfides have been developed continuously7–11 For example, sulfoxides are reduced to sul- fides with the Cp2TiCl2/Sm or TiCl4/Sm7,8 system, while the reaction between benzyl chloride and thiols in the presence of a modified montmorillonite clay containing 3-aminopropyltriethoxysilane has also been reported.10 Here we report that SmI2 reduces arylsulfanyltrimethylsilanes to samarium arylthiolates under a nitrogen atmosphere.This new thiolate anion species reacts with akyl halides to give unsymmetrical sulfides in good yield under neutral conditions (Scheme 1).Experimental General Procedure.·A solution of arylsulfanyltrimethylsilane (1 mmol) in THF (1 ml) was added by syringe to a deep blue solution of SmI2 (2.2 mmol) in THF (10 ml) at reflux temperature under an inert atmosphere of nitrogen. The deep blue colour of the solution gradually became brown within 5 h, which showed that the S–Si bond had been reductively cleaved by SmI2 and that the samarium arylthiolate (ArSmI2) had been generated.An alkyl halide (1 mmol) in THF (1 ml) was then added by syringe to the mixture and stirred under reflux for 4 h; a dilute solution of HCl and diethyl ether were added. The organic layer was washed with water (20 mlÅ2) and dried over anhydrous Na2SO4. The solvent was removed in vacuo. The crude product was purified by preparative TLC on silica gel (light petroleum:ethyl acetate=100:1 as eluent). Some results are summarized in Table 1. Data of Products.·1: mp 38–39 °C; dH (CCl4) 3.97 (2 H, s), 7.00–7.28 (10 H, m); vmax/cmµ1 3080, 3040, 2940, 1595, 1500, 1488, 1460, 1445, 1250, 1090, 1070, 1025, 735, 690. 2: oil; dH 0.83 (3 H, t), 1.0–1.67 (16 H, m), 2.80 (2 H, t), 7.03–7.23 (5 H, m); vmax/cmµ1 3090, 3080, 2960–2920, 2860, 1595, 1495, 1470, 1445, 1022, 730, 682. 3: oil; dH 0.87 (3 H, t), 1.02–1.70 (8 H, m), 2.80 (2 H, t), 7.03–7.22 (5 H, m); vmax/cmµ1 3090, 3080, 2970–2940, 2860, 1600, 1496, 1470, 1446, 1022, 728, 680. 4: mp 45–46 °C; dH 0.86 (3 H, t), 1.03–1.72 (28 H, m), 2.83 (2 H, t), 7.03–7.24 (5 H, m); vmax/cmµ1 3092, 3080, 2960–2920, 2860, 1600, 1469, 1470, 1447, 1021, 729, 678. 5: mp 47–49 °C; dH 3.46 (4 H, s), 7.17 (10 H, s); vmax/cmµ1 3080, 3060, 3019, 1585, 1480, 1450, 1240, 1185, 900, 760, 682. 6: oil; dH 0.84 (3 H, t), 1.07–1.43 (16 H, m), 2.23 (2 H, t), 3.54 (2 H, s), 7.20 (5 H, s); vmax/cmµ1 3100, 3080, 3040, 2970–2930, 2860, 1610, 1500, 1470, 1460, 1380, 1070, 1030, 760, 690. 7: oil; dH 0.84 (3 H, t), 1.07–1.43 (20 H, m), 2.23 (2 H, t), 3.54 (2 H, s), 7.20 (5 H, s); vmax/ cmµ1 3100, 2080, 3040, 2980–2940, 2864, 1610, 1500, 1472, 1465, 1460, 1380, 1070, 1029, 760, 690. 8: oil; dH 0.86 (3 H, t), 1.02–1.70 (8 H, m), 2.23 (2 H, t), 3.53 (2 H, s), 7.17 (5 H, s); vmax/cmµ1 3100, 3080, 3040, 2982–2940, 2860, 1610, 1500, 1470, 1460, 1380, 1070, 1030, 760, 690. 9: oil; dH 0.87 (3 H, t), 1.10–1.60 (8 H, m), 2.77 (2 H, t), 7.13–7.23 (4 H, m); vmax/cmµ1 3090, 3085, 2900–2800, 1585, 1490–1480, 1400, 1100–1090, 1010, 810, 740, 720. 10: oil; dH 0.87 (3 H, t), 1.13–1.40 (20 H, m), 2.76 (2 H, t), 7.14-7.23 (4 H, m); vmax/ cmµ1 3090, 3085, 2920–2800, 1585, 1490–1480, 1395, 1100–1090, 1010, 810, 740, 720. 11: oil; dH 0.87 (3 H, t), 1.15–1.42 (16 H, m), 2.76 (2 H, t), 7.14–7.23 (4 H, m); vmax/cmµ1 3090, 3085, 2920–2800, 1585, 1490–1480, 1395, 1100–1095, 1010, 810, 740, 720. 1H NMR spectra were recorded on a PMX-60 MHz instrument, and IR spectra were determined on a PE-683 spectrometer.We are grateful to the National Natural Science Foundation of China and Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, for financial support. Received, 21st July 1997; Accepted, 12th September 1997 Paper E/7/05190E *To receive any correspondence. †This is a Short Paper as defined in the Instructions for Authors, Section 5.0 [see J. Chem. Research (S), 1998, Issue 1]; there is therefore no corresponding material in J.Chem. Research (M). Table 1 Sulfide products from arylsulfanyltrimethylsilanes (ArSSiMe3) and alkyl halides (RX) Entry Ar R–X Product Yieldc(%) 123456789 10 11 12 Ph Ph Ph Ph Ph PhCH2 PhCH2 PhCH2 PhCH2 4-ClC6H4 4-ClC6H4 4-ClC6H4 PhCH2Cla PhCH2Clb Me[CH2]9Br Me[CH2]5Br Me[CH2]15Br PhCH2Cla Me[CH2[9Br Me[CH2]11Br Me[CH2]5Br Me[CH2]5Br Me[CH2]11Br Me[CH2]9Br PhSCH2Ph (1) PhSCH2Ph (1) PhS[CH2]9Me (2) PhS[CH2]5Me (3) PhS[CH2]15Me (4) PhCH2SCH2Ph (5) PhCH2S[CH2]9Me (6) PhCH2S[CH2]11Me (7) PhCH2S[CH2]5Me (8) 4-ClC6H4[CH2]5Me (9) 4-ClC6H4[CH2]11Me (10) 4-ClC6H4[CH2]9Me (11) 85 80 89 83 78 84 78 77 77 78 80 82 aAlkylation at room temp.for 4 h; breduction at room temp. for 10 h, alkylation at room temp. for 4 h; cyields of isolated products. SmI2/THF R–X ArS–SiMe3hArSSmI2hArS–R reflux 5 h reflux 4 h Scheme 1J. CHEM. RESEARCH (S), 1998 49 References 1 P. Girard, J. L. Namy and H. B. Kagan, J. Am. Chem. Soc., 1980, 102, 2693. 2 G. A. Molander, Chem. Rev., 1992, 92, 29. 3 G. A. Molander and C. R. Harris, Chem. Rev., 1996, 96, 307. 4 X. S. Jia and Y. M. Zhang, Synth. Commun., 1994, 24, 787. 5 G. Solladie, in Comprehensive Organic Synthesis, ed. B. M. Trost and I. Fleming, Pergamon Press, Oxford, 1991, vol. 6, pp. 133–170. 6 K. Ogura, in Comprehensive Organic Synthesis, ed. B. M. Trost and I. Fleming, Pergamon Press, Oxford, 1991, vol. 1, pp. 505–539. 7 Y. M. Zhang, Y. P. Yu and W. L. Bao, Synth. Commun., 1995, 25, 1825. 8 J. Q. Wang and Y. M. Zhang, Synth. Commun., 1995, 25, 3545. 9 N. M. Yoon, J. Chei and J. H. Ahn, J. Org. Chem., 1994, 59, 3490. 10 P. Kannan, K. Pitchumani, S. Rajagopal and C. Srinivasan, Chem. Commun., 1996, 369. 11 G. H. Lee, E. B. Choi and C. S. Dak, Tetrahedron Lett., 1994, 35, 2195.