插羰反應(yīng)制備醛

醛可以通過鹵化物在不同氫源中的鈀催化的插羰反應(yīng)制備。芳基和烯基碘化物和溴化物在惰性溶劑中，三級(jí)胺存在的條件下與CO和H2（1:1）發(fā)生插羰反應(yīng)生成醛。而芳基氯化物要先生成碳酸鉻的衍生物后，才能在130oC的溫度下轉(zhuǎn)化成醛。甲酸鈉可以代替H2被用作氫源來合成醛。氯苯在150oC的溫度下，用dippp作為配體，與CO和甲酸鈉反應(yīng)制得苯甲醛。

用錫的氫化物作為氫源，Pd(Ph3P)4作為催化劑，芳基、烯基鹵化物或三氟甲磺酸酯和芐基、烯丙基氯化物的羰基反應(yīng)也能制備醛。

硅的氫化物也能被用作氫源。重氮鹽6-1通過用Et3SiH或PHMS作為氫源，可以高收率快速的轉(zhuǎn)化成鄰甲基苯甲醛。

插羰反應(yīng)制備醛實(shí)驗(yàn)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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