Acrylic Acid → Acrylic anhydride

Acrylic anhydride was synthesized in 70-80% yield as in the following example. Acryloyl chloride (2.7 g, 30 mmol) was added dropwise over 5 min to an ice-cooled solution of acrylic acid (2.0 g, 30 mmol) and triethylamine (2.8 g, 30 mmol) in THF (50 mL), and the solution was stirred at room temperature for 16 h. The NH4+Cl− precipitate was collected in a fritted glass filter, and the solvent was then removed from the filtrate by rotary evaporation. The residue was dissolved in CH2Cl2 (25 mL), washed twice with dilute aq. NaHCO3 (50 mL each) and once with satd. NaCl aq. soln. (50 mL), and dried over anhy. Na2SO4. After filtration and removing the solvent by rotary evaporation, 2.8 g (80%) of acrylic anhydride was obtained as a light yellow liquid. It was used without further purification. 1H NMR (CDCl3, 77.23 ppm): 6.04 (m, ═CH trans to CO2), 6.14 (m, ═CH gem to CO2), 6.50 (d, ═CH cis to CO2). 13C NMR (CDCl3/DMSO-d6): 127.4 (═CH), 134.7 (′CH2), 161.2 (C═O).