Trifluoroacetic anhydride → 7,8-Dichlorothiochroman-4-one

Participants

Reaction Steps

The 3-(2,3-dichlorophenylthio)propanoic acid from Step 1 (3.88 g, 15 mmol) was dissolved in trifluoroacetic acid (10 mL), treated with trifluoroacetic anhydride (5 mL) and stirred at room temperature for 68.2 hours. The reaction mixture was poured into 10% Na2CO3 (100 mL), extracted with ethyl acetate, washed with brine, dried over MgSO4, and concentrated in vacuo to give a yellow oil. The crude material was passed through a column of silica gel eluting with 40% ethyl acetate/hexane to give 7,8-dichlorothiochroman-4-one as a white solid (0.46 g, 13%): mp 93°-102° C.; 1H NMR (CDCl3) 300 MHz 7.99 (d, J=8.7 Hz, 1H) 7.27 (d, J=8.7 Hz, 1H) 3.25 (m, 2H) 2.97 (m, 2H). Mass spectrum: M+=233.

Provenance & Evidence