Efficient and Selective Formation of Phenylacetic Acids from Diketene

在镍催化剂存在下，双乙烯酮、炔烃和Me2Zn的三个组分顺利地结合在一起，以优异的产率提供了3-亚甲基-4-己烯酸。此外，在相似的催化条件下，Et2Al(OEt)促进了与双乙烯酮和2当量炔烃的[2+2+2]环加成反应，生成了取代苯乙酸。更有趣的是，在Et2Al(OEt)和膦配体的存在下，通过与双乙烯酮的形式[2+2+1+1]环加成反应以及伴随着双酮的亚甲基C=C双键的裂解反应，生成了对称的苯乙酸。这是由双乙烯酮选择性地生成不饱和羧酸和苯乙酸的第一个例子。本文介绍的反应可能是合成生理活性分子的有力工具，如异戊二烯类酸和非甾体抗炎药(NSAIDs)。

In the presence of Ni catalyst, three components of diketene, alkyne, and Me2Zn combine smoothly to provide 3-methylene-4-hexenoic acids in excellent yields. Furthermore, under similar catalytic conditions, Et2Al(OEt) promotes [2+2+2] cycloaddition reactions with diketene and 2 equivalents of alkyne to give rise to the substituted phenylacetic acids. More interestingly, in the presence of Et2Al(OEt) and phosphine ligand, symmetrical phenyl acetic acids are constructed via the formal [2+2+1+1] cycloaddition reactions with diketene and 2 equivalents of alkyne accompanying the cleavage reaction of methylene C=C double bond of diketene.This is the first example of the selective formation of unsaturated carboxylic acids and phenylacetic acids from diketene involving oxanickelacycles. The reaction presented here might be a powerful tool in the expedient synthesis of the physiologically active molecules, such as isoprenoid acids and non-steroidal anti-inflammatory drugs (NSAIDs).