插羰反应制备醛

醛可以通过卤化物在不同氢源中的钯催化的插羰反应制备。芳基和烯基碘化物和溴化物在惰性溶剂中，三级胺存在的条件下与CO和H2（1:1）发生插羰反应生成醛。而芳基氯化物要先生成碳酸铬的衍生物后，才能在130oC的温度下转化成醛。甲酸钠可以代替H2被用作氢源来合成醛。氯苯在150oC的温度下，用dippp作为配体，与CO和甲酸钠反应制得苯甲醛。

用锡的氢化物作为氢源，Pd(Ph3P)4作为催化剂，芳基、烯基卤化物或三氟甲磺酸酯和苄基、烯丙基氯化物的羰基反应也能制备醛。

硅的氢化物也能被用作氢源。重氮盐6-1通过用Et3SiH或PHMS作为氢源，可以高收率快速的转化成邻甲基苯甲醛。

插羰反应制备醛实验操作

To the 45 mL-Parr bombwere added 3.95 g(25.0 mmol) of 3-bromopyridine, 10 mL of triethylamine, 10 mL of benzene, and0.30 g (0.375 mmol) of dibromobis(triphenylphosphine)palladium (II). The bombwas then flushed with argon, sealed, and pressurized to 600 Psi with carbonmonoxide. After the pressure was released, the bomb was re-pressurized to 600Psi with carbon monoxide and finally pressurized to 1200 Psi with hydrogen. Thereaction vessel was heated in an oil bath with stirring at 145oC.After 20 min, the pressure reached a maximum of 1350 Psi. Times and pressurewere periodically recorded until gas absorption stopped (26 hr), and thepressure in the reaction vessel had decreased to 1025 Psi. The reaction vesselwas cooled, and the gases were slowly released. After addition of anhydrousether, the reaction mixture was filtered to remove the triethylaminehydrochloride, concentrated in vacuo to remove ether, benzene, andtriethylamine, and finally distilled to give 2.15 g of (80% yield) of product.

The 75-mLreaction bomb was charged with 5.9 g (25.0mmol) of 1,4-dibromobenzene, 11.2 g (60.0 mmol) of tri-n-butylamine, 15 mLofbenzene, and 0.4 g (0.5 mmol) of dibromobis(triphenylphosphine)palladium (II).The bomb was then flushed with argon, sealed, and pressurized to 600 Psi withcarbon monoxide. After the pressure was released, the bomb was re-pressurizedto 600 Psi with carbon monoxide and finally pressurized to 1200 Psi withhydrogen. After 15 min, the pressure reached 1375 Psi at 140oC anddecreased to 600 Psi after 24 hr of treaction. The vessel was then cooled toroom temperature and the pressure released. After addition of anhydrous ether,the reaction mixture was filtered to remove the triethylamine hydrochloride,concentrated in vacuo to remove ether, benzene, and triethylamine. Afterevaporation of the ether, the resulting solids were sublimed (100oC, 8 mm) togive 3.79 g of a mixture of the terephthalaldehyde and 1,4-dibromobenzene. Themixture was separated by chromatography on silica gel. There were obtained 0.66g (2.8 mmol) of 1,4-dibromobenzene and 2.47 g (18.4 mmol) of1,4-benzenedicarboxaldehyde (83% yield). Recrystallization from hexane yielded2.21 g of pure dialdehyde.

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