Sodium ethoxide

2,6-Dimethyl-γ-pyrone
(2.00 g, 16.1 mmol) and 4-(N,N-dimethylamino)benzaldehyde
(4.81 g, 32.2 mmol) were added into a 100 mL two-neck round-bottom
flask. Anhydrous ethanol (60 mL) was delivered into the flask using
a glass syringe under an Ar atmosphere. Sodium ethoxide (18 mL, 48
mmol; 21 wt % in ethanol, Sigma-Aldrich) was added slowly into the
solution using a disposable syringe. The reaction mixture was refluxed
for 48 h under an Ar atmosphere. After cooling to room temperature,
the solution was concentrated under a reduced pressure. Silica gel
column purification was performed with increasing polarity of eluents
from 100% CH₂Cl₂ to 19:1 v/v CH₂Cl₂/CH₃OH. An orange solid was obtained with a yield
of 56%. R_f = 0.2 (19:1 v/v EtOAc/CH₃OH). ¹H NMR (300 MHz, CDCl₃) δ
(ppm): 3.04 (s, 12H), 6.16 (s, 2H), 6.52 (d, J =
15.9 Hz, 2H), 6.72 (d, J = 8.7 Hz, 4H), 7.41 (d, J = 15.9 Hz, 2H), 7.47 (d, J = 9.0 Hz,
4H). ¹³C{¹H} NMR (126 MHz, CD₂Cl₂) δ (ppm): 40.50, 112.46, 112.52, 115.23, 123.44, 129.48,
136.28, 151.96, 162.53, 180.34. HR MS (FAB, m-NBA):
calcd for C₂₅H₂₇N₂O₂ ([M
+ H]⁺), 387.2073; found: 387.2069. Anal. calcd for C₂₅H₂₆N₂O₂: C, 77.69; H, 6.78;
N, 7.25. Found: C, 77.49; H, 6.72; N, 7.29.