反应详情

The starting aldehyde was obtained as follows: Diethyl 3-pyridylborane (1.51 g), powdered potassium hydroxide (1.71 g) and teteramethylammonium bromide (330 mg) were added to a solution of tetrakistriphenylphosphine palladium [0] (528 mg) and 4-bromobenzaldehyde dimethyl acetal (3.55 g) in anhydrous tetrahydrofuran (60 ml). The mixture was heated at reflux for 2 hours, the THF evaporated and the residue dissolved in ether (200 ml). The ether solution was washed with saturated brine (2×100 ml), dried (Na2SO4) and evaporated to an oil. The oil was purified by column chromatography on alumina, eluting with 10% ethyl acetate in hexane to give 4-(3-pyridyl)benzaldehyde dimethyl acetal (1.72 g). NMR(CDCl3): 3.37(6H,s), 5.45(1H,s), 7.45(1H,m), 7.58(4H,m), 7.89(1H,m), 8.59(1H,dd) and 8.85(1H,d). This diacetal (5.0 g) was stirred in 1M aqueous hydrochloric acid (30 ml) for 45 minutes and the mixture neutralised with 1M aqueous sodium hydroxide solution (30 ml) and extracted with ether (3×60 ml). The ether extracts were combined, washed with saturated brine, dried (Na2SO4) and evaporated to give 4-(3-pyridyl)benzaldehyde (3.41 g) as an oil which gave a solid on standing, m.p 48°-51° C.; NMR(CDCl3): 7.43(1H,q), 7.76(2H,m), 7.92(1H,m), 8.01(2H,m), 8.65(1H,dd), 8.90(1H,d) and 10.09(1H,s).

1. temperatureThe mixture was heated
2. temperatureat reflux for 2 hours
3. customthe THF evaporated
4. dissolutionthe residue dissolved in ether (200 ml)
5. washThe ether solution was washed with saturated brine (2×100 ml)
6. dry with materialdried (Na2SO4)
7. customevaporated to an oil
8. customThe oil was purified by column chromatography on alumina
9. washeluting with 10% ethyl acetate in hexane