Claisen, Ludwig

Ludwig Claisen was a Ger man chemist who worked during the last two decades of the nineteenth century and the first two decades of the twentieth His name is associated with three reac tions The Claisen-Schmidt reaction was presented in Section 18 10 the Claisen condensation is discussed in this section and the C/a/sen rearrangement will be intro duced in Section 24 13... 

Claisen, R. L. Lowman, O. Ber. Dtsch. Chem. Ges. 1887, 20, 651. Rainer Ludwig Claisen (1851—1930), bom in Cologne, Germany, probably had the best pedigree in the history of organic chemistry. He apprenticed under Kekule, Wohler, von Baeyer, and Fischer before embarking on his own independent research. 

Fig. 14.46. Preparation of an allyl aryl ether and subsequent Claisen rearrangement. (The rearrangement is named after the German chemist Ludwig Claisen. Basically, the name is pronounced the German way but it is known that the family preferred the pronunciation /klaezn/.)...

ArCUO + CHfCO CJI , CtfliCHiCN. In 1890 Ludwig Claisen, who three years earlier had proposed use of sodium ethoxide as a condensing agent, explored the possibility of condensing benzaldehyde with ethyl acetate to produce ethyl cinnamate (3), in possible rivalry with the Perkin reaction. First trials with a... 

One of the earliest accounts of the tetrahedral intermediate came from Rainer Ludwig Claisen in 1887. In the reaction of benzyl benzoate with sodium methoxide and methyl benzoate with sodium benzyl oxide, he observed a white precipitate which under acidic conditions yields benzyl benzoate, methyl benzoate, methanol, and benzyl alcohol (Scheme 7.69). 

Ludwig Claisen was a German chemist who worked during the last two decades of the nineteenth century and the first two decades of the twentieth. His name is associated with three reactions. 

CH3COOR CH3COCH2COOR -I ROH The reaction is catalysed by sodium ethox-ide, the mechanism being similar to that of the aldol reaction, it is named after Ludwig Claisen (1851-1930). 

Ludwig Claisen (Cologne, 14 January 1851-Godesberg, 5 January 1930) studied in Bonn and Gottingen, was assistant in Bonn (1875), professor in Kiel (1897-1904) and from 1904 honorary professor in Berlin. ... 

In this section, we examine the formation of an enolate anion from one ester, followed by the nucleophilic acyl substitution of the enolate anion at the carbonyl carbon of another ester. One of the first of these reactions discovered was the Claisen condensation, named after its discoverer, German chemist Ludwig Qaisen (1851—1930). We illustrate a Claisen condensation by the reaction between two molecules of ethyl acetate in the presence of sodium ethoxide, followed by acidification, to give ethyl acetoacetate (note that, in this and many of the equations that follow, we abbreviate the ethyl group as Et) ... 

The ability of aldehydes, ketones and esters to react with themselves or similar compounds under basic conditions was being investigated at this time by Ludwig Claisen. Here the carbon bearing the reactive hydrogen becomes joined to the carbonyl carbon of the other molecule. This provides a convenient route to ethyl acetoacetate ... 

In the late nineteenth century, Ludwig Claisen (Germany 1851-1930) treated an ester with a base the isolated product was a P-keto ester. This product results from the enolate anion of one molecule of the ester condensing with a second molecule via an acyl substitution reaction (Chapter 16, Section 16.8). In a typical experiment, ethyl 2-methyl propionate (60) is treated with a specialized base (sodium triphenylmethide, 19) in diethyl ether and stirred at room temperature for 60 hours. This reaction mixture is then acidified with glacial acetic acid (i.e., 100% acetic acid) the final isolated product is ethyl 2,2,4-tri-methyl-3-oxopentanone (61) in 74% yield. It is clear that when an ester enolate reacts with another ester, the product is a -keto ester and the reaction is now called the Claisen condensation. 

The crossed aldol reaction is important enough to have been given its own name, the Claisen-Schmidt condensation (Ludwig Claisen, 1851—1930). 

Professor Rainer Ludwig Claisen (1851-1930), University of Berlin, Germany. 

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