Chloroacetone → 5-Bromo-3-methyl-1-benzothiophene

Participants

Reaction Steps

A mixture of 4-bromothiophenol (3.9 g, 20 mmol), K2CO3 (5.5 g, 40 mmol) and chloroacetone (6.6 mL, 82 mmol) in acetone (50 mL) was heated at reflux over night. The reaction mixture was filtered and the solvent was evaporated giving 5.0 g crude product. The intermediate thioether was dissolved in chlorobenzene (50 mL) and polyphosphoric acid (PPA, 2.5 g) was added (Plé et al., (1988) J. Heterocyclic Chem. 25, 1271-1272). After reflux for 24 h, the solvent was decanted and the PPA residue was treated with CH2Cl2. The combined organic extracts were washed with water and dried. Evaporation of the solvents afforded the crude product which was purified on silica (heptane as eluent) to give the title compound (2.36 g, 50% over two steps). 1H NMR (400 MHz, CDCl3) δ ppm 2.41 (d, J=1.20 Hz, 3 H) 7.11 (qd, J=1.20, 0.54 Hz, 1 H) 7.44 (ddd, J=8.53, 1.90, 0.54 Hz, 1 H) 7.70 (dd, J=8.53, 0.54 Hz, 1 H) 7.85 (dd, J=1.90, 0.54 Hz, 1 H).

Provenance & Evidence