Unexpected reaction of (Z)-1,2-bis(benzylseleno)-ethene: The formation of 1,4-diselenin

Abstract

Heating (Z)-1,2-bis(benzylseleno)ethene at 140–180 °C leads to 1,4-diselenin (79% yield) and dibenzyl selenide. This unusual reaction represents a convenient method for preparing 1,4-diselenin.

Keywords:

• (Z)-1,2-bis(Benzylseleno)ethane
• Dibenzyl selenide
• 1,4-Diselenin
• Selenophene

Acknowledgement

The authors gratefully acknowledge support of this work by the U.S. National Science Foundation (CHE-0201555).

Notes

¹A mixture of Bn₂Se₂ (6.8 g), KOH (8 g), DMSO (40 ml) and water (4 ml) was rotated at room temperature in a 1 l rotating autoclave under an atmosphere of acetylene (12 atm) for 5 h. The mixture was then diluted with water and extracted with ether. The organic phase was washed with water and dried over CaCl₂. The ether was distilled off by heating on a warm water bath at ordinary pressure and then in vacuum at room temperature. The residue is crude 3a (6.98 g, 95%), which was used to prepare 1b without further purification. ¹H NMR of the crude 3a (CDCl₃, δ, ppm): 7.23 (m, 10H, C₆H₅), 6.75 (s, 2H, SeCH˭), 3.93 (s, 4H, SeCH₂). MS, m/z (rel. int., %): 368 (50), 291 (19), 210 (100), 184 (30), 160 (17), 105 (44), 80 (17). Attempted distillation of 3a at 1 mmHg gave crude 1b, which was distilled in vacuo.

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²1,4-Diselenin 1b, bp 60–62 °C/1 mmHg. ¹H NMR (CDCl₃, δ, ppm): 7.02 (s). ¹³C NMR (CDCl₃, δ, ppm): 120.11. MS, m/z (rel. int., %): 212 (55), 186 (19), 160 (100), 132 (60), 105 (33), 80 (43). Anal. Calcd for C₄H₄Se₂: C, 22.88; H, 1.92; Se 75.20. Found: C, 23.21; H, 1.98; Se, 74.65.

³The 9-Se-3 label signifies a selenium-centered species in which the selenium formally has nine valence shell electrons and has three ligands attached: Perkins, C. W., Martin, J. C., Arduengo, A. J., Lau, W., Alegria, A. and Kochi, J. K., J. Am. Chem. Soc., 102, 7753 (1980).

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