研究發(fā)現(xiàn)，對(duì)某些碘代物，一些無(wú)磷配體催化劑可以在較為溫和的條件下高效的催化反應(yīng)，如PdCl2、Pd(OAc)2、Pd/C等。同時(shí)，也可以避免反應(yīng)中配體所形成的雜質(zhì)對(duì)產(chǎn)品分離過(guò)程產(chǎn)生的困擾。
Hiroa【Sakurai, H. J. Org. Chem. 2002, 67, 2721】等以水作溶劑，室溫下Pd/C 催化碘代苯酚與芳基硼酸的Suzuki 偶聯(lián)反應(yīng)取得了非常好的結(jié)果。這個(gè)方法因?yàn)樘?hào)稱(chēng)清潔生產(chǎn)，對(duì)大規(guī)模生產(chǎn)具有很大意義。
D. S. Ennis【D. S. Ennis，Org. Process Res. Dev. 1999, 3,248】等用Pd /C 做催化劑大批量的進(jìn)行Suzuki-coupling反應(yīng)，以生產(chǎn)抗抑郁藥物，SB-245570。
直接Pd(OAc)2用于 Suzuki偶聯(lián)反應(yīng)【Felix E. Goodson, Organic syntheses, Coll. Vol. 10, p.501; Vol.75,p.61】
4-Methoxy-2'-methylbiphenyl . o-Tolylboronic acid,10.0 g(73.6 mmol),16.8 g(71.8 mmol) of 4-iodoanisole, and 200 mL of acetoneare combined in a 1-L, three-necked flask equipped with an efficient stirbar, two stoppers, and a reflux condenser attached to a gas-flow adapter with a stopcock. Potassium carbonate,25.0 g(0.180 mol), is dissolved in 200 mL of water in a separate 250-mL Schlenk flask. In a third flask (25-mL Schlenk flask) 3.30 mg (0.02 mmol, 0.2%) of palladium acetate is dissolved in 10 mL of acetone. All three flasks are then thoroughly degassed by four freeze-pump-thaw cycles. Under an argonback flow, one of the stoppers on the three-necked flask is replaced with a rubber septum, and the carbonate and catalyst solutions are added via cannula to form a biphasic mixture. The top layer turns brown upon addition of the catalyst. The septum is replaced with the glass stopper and three additional freeze-pump-thaw cycles are applied. The flask is then backfilled with argon, and the reaction is brought to reflux under a positive argonpressure. After 2 hr at reflux the heat source is removed and the reaction is allowed to cool. By this time the brown color has faded and the reaction is a triphasic mixture with copious amounts of palladiumblack floating between the layers. The reaction is transferred to a 1-L separatory funnel and extracted into diethyl ether(3 × 100 mL). The organic layers are combined, washed with water (1 × 100 mL) saturated with sodium chloride , and dried over magnesium sulfate . Solvent is removed with a rotary evaporator to yield a yellow oil which is distilled (125-130°C,0.10 mm) to give12.8 gof 4-methoxy-2'-methylbiphenylas a colorless oil (90.3% yield).
本文非原創(chuàng)內(nèi)容，版權(quán)歸原作者所有，如涉及版權(quán)問(wèn)題，請(qǐng)聯(lián)系刪除。
