2,3-Dihydrothieno[3,4-b][1,4]dioxine-5,7-dicarbaldehyde

68-12-2

126213-50-1

211235-87-9

Under nitrogen protection, 3,4-ethylenedioxythiophene (EDOT, 3 g, 0.021 mol) was dissolved in anhydrous tetrahydrofuran (THF, 50 mL) and cooled to -78 °C. Subsequently, a solution of 1.6 M n-butyllithium (n-BuLi, 29 mL) was slowly added dropwise. After the dropwise addition, the reaction system was slowly warmed to 0 °C and stirred continuously at this temperature for 30 min. The reaction mixture was again cooled to -78 °C and quenched by the addition of dry N,N-dimethylformamide (DMF, 3.5 mL). The reaction mixture was transferred to room temperature conditions and stirring was continued for 2 hours. Upon completion of the reaction, the mixture was poured into crushed ice containing hydrochloric acid (pH=4) and a brown solid was precipitated. The solid was collected by filtration, washed with plenty of water and dried under vacuum. The crude product was recrystallized by cold methanol to afford the target compound 2,3-dihydrobenzo[3,4-b][1,4]dioxane-5,7-dibenzaldehyde (brown solid) in 75% yield. The product characterization data were as follows: IR (film) υmax: 2955, 2924, 2854, 1666, 1614, 1504, 1454, 1375 cm-1; 1H NMR (500 MHz, CDCl3): δ = 10.04 (s, 2H), 4.46 (s, 4H); 13C NMR (500 MHz, CDCl3): δ = 180.94, 147.15, 124.16, 65.15; Elemental analysis (C8H6O4S): Calculated values (%) C 48.48, H 3.04, S 16.14; Measured values: C 48.51, H 3.06, S 16.14.