Dimethylformamide → 4-Vinylbenzaldehyde

온도

20 °C

A solution of 17.06 mL (0.220 moles) of anhydrous N,N′-dimethylformamide in 100 mL of anhydrous tetrahydrofuran was cannula transferred into the 125 mL addition funnel and then added dropwise over a period of 1 hour to the previously prepared solution of p-vinylphenylmagnesium chloride (0.199 moles). The temperature was maintained at 20° C. during the addition (higher temperatures resulted in polymer formation and lower yields). The reaction mixture was stirred for 2 hours and then allowed to remain overnight under a nitrogen atmosphere. The reaction mixture was quenched with 200 mL saturated aqueous ammonium chloride solution causing an initial exotherm (up to 45° C.) and then the precipitation of a voluminous “gelatinous” white solid (magnesium hydroxides). The resultant emulsion was broken by centrifuging aliquots of the mixture at 4000 rpm for 3 minutes and the resultant clarified two phase mixture poured into a 500 mL separating funnel and the organic layer partitioned and collected. The remaining aqueous layer was extracted twice with 100 mL of Et2O; the organic extracts were then combined and dried over anhydrous MgSO4. The drying mixture was filtered and the collected solid washed with 2×50 mL portions of Et2O. The filtrate and washings were combined and the solvent was stripped off in vacuo using a rotary evaporator and the residue was distilled in vacuo in the presence of a heaped spatula measure of phenothiazine with two fractions coming over: Fraction 1 (53° C. at 0.425 torr; v. pale yellow liquid), Fraction 2 (48-50° C. at 0.350 torr; v. pale yellow liquid). Fraction 1 was discarded and fraction 2 retained and a yield taken. Yield: 18.325 g (70%, very pale yellow liquid). 1H NMR (CDCl3) δ 5.46 (d, 1H, ═C—H), 5.93 (d, 1H, ═C—H), 6.79 (dd, 1H, ═C—H), 7.57 (d, 2H, ArH), 7.86 (d, 2H, ArH), 10.01 (s, 1H, —CH═O).