Toluene → 5,6,7,8-tetrahydro-4H-cyclohepta[b]thiophen-4-one

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Reaction Steps

A mixture of 5-(2-thienyl)pentanoic acid (8.9 g, 48.0 mmol), phosphorus pentoxide (24.7 g, 86.9 mmol) and celite (16.0 g) in toluene (338 mL, 3170 mmol) was heated to reflux for 2 hr. The resulting black mixture was allowed to cool to rt and filtered. The solid cake was washed thoroughly with ethyl acetate then the filtrate was washed with saturated NaHCO3, dried over MgSO4, concentrated and dried under high vacuum to afford 6.0 g product as a brown oil (74.0% yield). LCMS: (FA) ES+ , 167. 1H NMR (400 MHz, CDCl3) δ: 7.40-7.42 (d, J=5.3, 2H), 6.98-7.00 (d, J=5.3, 2H), 3.0-3.12 (m, 2H), 2.72-2.76 (m, 2H), 1.85-2.0 (m, 4H).

Provenance & Evidence