3-Methyl-1,4,2-dioxazol-5-one

• (S)-(+)-2-(6-Methoxy-2-naphthyl)propionic Acid [M1021]
• 3-Methyl-1,4,2-dioxazol-5-one [M3998]
• 1,8-Diazabicyclo[5.4.0]-7-undecene (= DBU) [D1270]
• Ethyl Acetate

3-Methyl-1,4,2-dioxazol-5-one (0.88 g, 8.7 mmol, 2.0 eq.)　was added to a solution of (S)-(+)-2-(6-methoxy-2-naphthyl)propionic acid (1.0 g, 4.3 mmol, 1.0 eq) and DBU (0.99 g, 6.5 mmol, 1.5 eq.) in ethyl acetate (8.7 mL) at room temperature and the mixture was stirred at room temperature for 4 h. The reaction mixture was quenched with 2 mol/L HCl (4.3 mL) and the aqueous layer was extracted with Ethyl Acetate (8.7 mL x 3). The combined organic layer was washed with brine, dried over magnesium sulfate and filtered. The solvent was removed under reduced pressure, and the residue was washed with ethyl acetate to give (S)-N-[1-(6-methoxynapthalen-2-yl)ethyl]acetamide as a white solid (0.66 g, 62% yield, e.r. >99:1).

• The reaction was operated under ambient atmosphere and monitored by GC.
• The bubbling of CO₂, a byproduct of the reaction, was observed as it proceeded.
• The enantiomeric ratio was determined by LC.

(S)-N-[1-(6-Methoxynapthalen-2-yl)ethyl]acetamide

¹H NMR (400 MHz, CDCl₃); δ 7.69 – 7.66 (m, 3H), 7.40 (d, 1H), 7.14 – 7.11 (m, 2H), 5.94 (brs, 1H), 5.25 (m, 1H), 3.90 (s, 3H), 1.98 (s, 3H), 1.55 (d, 3H).

¹³C NMR (400 MHz, CDCl₃); δ 169.1, 157.6, 138.2, 133.8, 129.3, 128.7, 127.3, 125.3, 124.4, 119.0, 105.6, 55.2, 48.6, 23.4, 21.5.

• Enhancing the Sustainability and Scalability of Transition-Metal-Free Stereoretentive Decarboxylative Amidation with Dioxazolones
  • J. Kweon, M. Lee, D. Kim, S. Chang, Org. Process Res. Dev. 2024, 28, 3691.