4,5-Dihydrocyclopenta[b]thiophen-6-one

Synthesis

To a suspension of phosphorus pentoxide (P2O5, 25.4 g, 179.0 mmol) in methanesulfonic acid (100 mL) was added 3-(thiophen-3-yl)propionic acid (5.0 g, 32.0 mmol) and the reaction mixture was stirred for 1 hour at room temperature. Upon completion of the reaction, the reaction mixture was concentrated under reduced pressure and the residue was purified by fast column chromatography (eluent: 20-30% ethyl acetate/hexane) to afford 4,5-dihydropenta[B]thiophen-6-one (1.34 g, 30% yield) as a brown solid. The structure of the product was confirmed by 1H NMR (300 MHz, MeOH): δ 8.14 (d, J = 4.8 Hz, 1H), 7.17 (d, J = 4.8 Hz, 1H), 2.94-3.15 (m, 4H); mass spectra (EI) m/z = 139.2 [M + 1]+.

References

[1] European Journal of Organic Chemistry, 2004, # 21, p. 4442 - 4451
[2] Tetrahedron, 1997, vol. 53, # 12, p. 4239 - 4246
[3] Patent: US2012/225857, 2012, A1. Location in patent: Page/Page column 16
[4] Journal of Organic Chemistry, 1997, vol. 62, # 8, p. 2401 - 2408
[5] Journal of the Chemical Society, Chemical Communications, 1994, # 19, p. 2249 - 2250