Indium Tribromide: A Novel and Highly Efficient Reagent for the Conversion of Oxiranes to Thiiranes

Abstract

Epoxides react smoothly with potassium thiocyanate in the presence of 5 mol% of indium tribromide under mild and convenient reaction conditions to afford the corresponding thiiranes in high yields. This method is compatible with a wide range of protecting groups and functional groups such as alkenes, alkynes, esters, THP, TBDMS, and PMB ethers present in the molecule.

indium reagents - oxiranes - thiocyanate - thiiranes

References

1a Bonini C. Righi G. Synthesis  1994,  225 

1b Shimizu M. Yoshida A. Fujisawa T. Synlett  1992,  204 

1c Smith JG. Synthesis  1984,  629 

2a Sander M. Chem. Rev.  1966,  66:  297 

2b Vedejs E. Krafft GA. Tetrahedron  1982,  38:  2857 

3a Jankowski K. Harvey R. Synthesis  1972,  627 

3b Iranpoor N. Kazemi F. Synthesis  1996,  821 

3c Tamami B. Kiasat AR. Synth. Commun.  1996,  26:  3953 

3d Brimeyer MO. Mehrota A. Quici S. Nigam A. Regen SL. J. Org. Chem.  1980,  45:  4254 

3e Sharghi H. Nasseri MA. Niknam K. J. Org. Chem.  2001,  66:  7287 

4 Doyle FP. Holland DO. Hunter WH. Mayer JHC. Queen AJ. J. Chem. Soc.  1960,  2665 

5 Chan TH. Finkenbine JR. J. Am. Chem. Soc.  1972,  2880 

6a Calo V. Lopez L. Marchese L. Pesce G. J. Chem. Soc., Chem. Commun.  1975,  62 

6b Cambie RC. Mayer GD. Rutledge PS. Woodgate PD. J. Chem. Soc., Perkin Trans. 1  1975,  52 

7 Takido T. Kobayashi Y. Itabashi K. Synthesis  1986,  779 

8a Li C.-J. Chan T.-H. Tetrahedron  1999,  55:  11149 

8b Babu G. Perumal PT. Aldrichima Acta  2000,  33:  16 

8c Ghosh R. Indian J. Chem., Sect. B  2001,  40:  550 

9a Bandini M. Giorgio Cozzi P. Melchiorre P. Umani-Ronchi A. Tetrahedron Lett.  2001,  42:  3041 

9b Ceschi MA. Felix LA. Peppe C. Tetrahedron Lett.  2000,  41:  9695 

9c Bandini M. Giorgio Cozzi P. Giocomini M. Melchiorre P. Selva S. Umani-Ronchi A. J. Org. Chem.  2002,  67:  3700 

10a Yadav JS. Reddy BVS. Raju AK. Rao CV. Tetrahedron Lett.  2002,  43:  5437 

10b Yadav JS. Reddy BVS. Synthesis  2002,  511 

11

Experimental Procedure: A mixture of epoxide (5 mmol), potassium thiocyanate (5 mmol) and InBr₃ (5 mol%) or InCl₃ (10 mol%) in acetonitrile (10 mL) was stirred at 60 °C temperature for an appropriate time (Table). After completion of the reaction, as indicated by TLC, the reaction mixture was diluted with water (2 × 10 mL) and extracted with diethyl ether (2 × 15 mL). The combined organic layers were dried over anhydrous Na₂SO₄, concentrated in vacuo and purified by column chromatography on silica gel (Merck, 100-200 mesh, ethyl acetate-hexane 1:9) to afford pure thiirane after removal of solvent. The aqueous layer was concentrated in vacuo to recover the catalyst. Spectroscopic data for selected products: 2a: 2-phenyl-thiirane: Liquid. IR (KBr): 2922, 1628, 1457, 1216, 1031, 767 cm^-1. ¹H NMR (CDCl₃): δ 2.60 (dd, 1 H, J = 1.4 Hz, 6.0 Hz), 2.85 (d, 1 H, J = 6.0 Hz), 3.85 (t, 1 H, J = 6.0 Hz), 7.20-7.88 (m, 5 H). EIMS (m/z): 136 (M⁺), 104, 91, 69, 43.
2l: 2-[2-(4-methoxybenzyloxy)ethyl]thiirane: Liquid. IR (KBr): 2925, 1629, 1451, 1217, 1182, 1045, 760 cm^-1.
¹H NMR (CDCl₃): δ 1.58-1.67 (m, 1 H), 2.05-2.25 (m, 2 H), 2.50 (dd, 1 H, J = 1.5, 6.0 Hz), 1.95-3.05 (m, 1 H), 3.60 (t, 2 H, J = 6.0 Hz), 3.80 (s, 3 H), 4.45 (s, 2 H), 6.80 (d, 2 H, J = 8.0 Hz), 7.25 (d, 2 H, J = 8.0 Hz). EIMS (m/z): 224 (M⁺), 191, 137, 121, 78, 55. 2o: 2-(2-naphthyloxymethyl)thiir-ane: Solid, mp 74 °C. IR (KBr): 2927, 1628, 1596, 1465, 1257, 1217, 1182, 1006, 839, 742 cm^-1. ¹H NMR (CDCl₃): δ 2.28 (dd, 1 H, J = 1.4, 5.2 Hz), 2.60 (d, 1 H, J = 5.9 Hz), 3.20-3.25 (m, 1 H), 3.90 (dd, 1 H, J = 7.0 Hz, 10.5 Hz), 4.38 (dd, 1 H, J = 5.2 Hz, 10.5 Hz), 7.0-7.18 (m, 2 H), 7.25-7.40 (m, 2 H), 7.60-7.80 (m, 4 H). EIMS (m/z): 216 (M⁺), 145, 116, 73, 45.