Diisopropylamine (dried over CaH₂, degassed)
ⁿBuLi (2.5 M in hexanes)
2,3-dihydro-1,4-dithiin synthesis
Selenium powder
Titanocene dichloride
THF (refluxed over potassium, degassed)

A solution of LDA was prepared in situ thus: diisopropylamine (1.54 ml, 0.011 mol) was dissolved in dry THF (5 ml) under argon, and cooled to -78°C (dry ice/acetone bath). 2.5 M solution of ⁿBuLi in hexanes (4.4 ml, 0.011 mol) was added dropwise. The mixture was allowed to warm up to the ambient temperature and was stirred for 2 h. In another vessel, 2,3-dihydro-1,4-dithiin (2.0 g, 16.9 mmol) was dissolved in dry THF (100 ml) under argon and cooled to -78°C. The solution of LDA was added dropwise and the mixture was stirred for 0.5 h at -78°C. Selenium powder (2.94 g, 37.2 mmol) was suspended in dry THF (100 ml) and cooled to -40°C (dry ice/acetonitrile bath). The solution of lithiated thiine was added dropwise and the mixture was stirred for 4 h at -40°C before cooling to -78°C. Solid titanocene dichloride (4.63 g, 18.6 mmol) was added and the mixture was stirred for 1 h at -78°C. Dry ice/acetone cooling bath was replaced with dry ice/acetonitrile bath and the mixture was allowed to warm slowly overnight. The solvents were removed under reduced pressure and the residue was redissolved in DCM and filtered through celite. The product was purified on silica using DCM:hexane (1:1) as eluent. Green solid obtained. Yield 3.01 g (39%).

This is an intermediate in the synthesis of BEDT-TSF (BETS).

This procedure has been published in outline by Kato et al. and Courcet et al., to our knowledge however this is the first detailed synthetic procedure for this reaction. We would like to thank prof. Hiroki Akutsu for help with this procedure.

¹H NMR (400 MHz, 298K, CDCl₃) δ_H 6.14 (s, 5H, Cp), 5.93 (s, 5H, Cp), 3.33 (d, J = 15.6 Hz, 4H, CH₂)

¹³C NMR (101 MHz, 298K, CDCl3) δ_C 111.4 (Cp), 109.4 (Cp), 31.6 (CH₂)