Efficient Activation of Acetals, Aldehydes, and Imines toward Silylated Nucleophiles by the Combined Use of Catalytic Amounts of [Rh(COD)Cl]2and TMS-CN under Almost Neutral Conditions
甲二聚4-羟基苯乙酮肟衍生钯化合物已被用作一种非常有效的预催化剂用于通过反应条件的适当选择丙烯醛缩二乙醇,得到任一肉桂醛衍生物或3- arylpropanoate酯的化学选择性芳基化。肉桂醛衍生物的合成可以通过丙烯醛缩二乙醇与碘,在溴-或氯代芳烃的Heck反应进行Ñ,Ñ用k二甲基乙酰胺(DMA)2 CO 3作为在120℃下和四-碱Ñ-醋酸丁丁基铵(TBAA)和氯化钾作为添加剂,然后进行酸处理。对于3-芳基丙酸酯,相应的丙烯醛二乙缩醛与碘芳烃的芳基化反应可以在90°C的DMA水溶液中使用(二(己基己基)甲胺)碱进行,而溴芳烃的反应则必须在120°C的条件下使用四芳基进行。 -溴化正丁基铵(TBAB)作为添加剂。或者,该过程可以在微波辐射下进行。与乙酸钯(II)相比,这些偶联以高收率和较低的催化剂负载量发生,并且反应时间较短且丙烯醛二乙基缩醛过量的发生率较低。
The reaction of aryl iodides and bromides with acrolein diethyl acetal in the presence of Pd(OAc)(2), (n)()Bu(4)NOAc, K(2)CO(3), KCl, and DMF, at 90 degrees C until the disappearance of the acetal followed by the addition of 2 N HCl to the crude reaction mixture, affords cinnamaldehydes in good to high yields. A variety of functional groups are tolerated in the aryl halides, including ether, aldehyde
芳基碘化物和溴化物与丙烯醛二乙缩醛在Pd(OAc)(2),(n)()Bu(4)NOAc,K(2)CO(3),KCl和DMF存在下的反应,于90直至乙缩醛消失,然后向粗制反应混合物中加入2 N HCl,可以得到高至高收率的肉桂醛。芳基卤化物中可耐受多种官能团,包括醚,醛,酮,酯,二烷基氨基,腈基和硝基。靠近氧化加成位点的取代基的存在不妨碍反应。
Highly-functionalized arene synthesis based on palladium on carbon-catalyzed aqueous dehydrogenation of cyclohexadienes and cyclohexenes
Transition metal-catalyzed dehydrogenation is a clean oxidation method requiring no additional oxidants. We have accomplished a heterogeneous Pd/C-catalyzed aqueous dehydrogenation of 1,4-cyclohexadienes and cyclohexenes to give the corresponding highly-functionalized arenes. Furthermore, various arenes could be efficiently constructed in a one-pot manner via a Diels–Alder reaction and the following
synthesizing the target molecules. The perfect chemoselectivity between aromatic and aliphatic aldehydes is difficult to achieve by the previous methods. The aromatic aldehyde-selective nucleophilic addition in the presence of aliphatic aldehydes was newly accomplished. Namely, the aromatic aldehyde-selective nucleophilic addition using arenes and allyl silanes proceeded in the presence of trialkylsilyl
1-Tributylstannyl-3,3-diethoxyprop-1-ene has proved to be a readily available β-formylvinyl anion equivalent which under mild experimental conditions gives ready access to cinnamic skeletons and 4-oxo- or 6-oxo-α,β-enals.
enolates as nucleophiles with aromatic aldehydes chemoselectively proceeded in the presence of silyl triflate and 2,2′-bipyridyl to produce β-siloxy aldehydes, while the aliphaticaldehydes were completely recovered. The unprecedented chemoselectivities depend on the reactivities of the pyridinium-type intermediatesderivedfrom the aromatic and aliphaticaldehydes.