Trifluoroacetic anhydride → 7-Methylthiochroman-4-one

Participants

Reaction Steps

3-(3-Methylphenylthio)propanoic acid from Step 1 (10.12 g, 52 mmol) was dissolved in trifluoroacetic acid (20 mL), treated with trifluoroacetic anhydride (10 mL) and stirred at room temperature for 1.9 hours. The reaction was poured into 10% Na2CO3 (100 mL), extracted with ether, washed with brine, dried over MgSO4, and concentrated in vacuo to give an orange oil which was passed through a column of silica gel eluting with 8% ether/hexane to give 7-methylthiochroman-4-one (2.97 g, 32%) as a yellow oil: 1H NMR (CDCl3) 300 MHz 7.97 (d, J=8.1 Hz, 1H) 7.06 (s, 1H) 6.97 (d, J=7.7 Hz, 1H) 3.17 (m, 2H) 2.95 (m, 2H) 2.31 (s, 3H). Mass spectrum: M+H=179.

Provenance & Evidence