Chain homologated ketones, synthesis

A straight chain diazomethyl ketone will also undergo Wolff rearrangement on irradiation. Such diazomethyl ketones are readily prepared from the corresponding acid chloride (150) by exposure to diazomethane or, more conveniently, trimethylsilyldiazomethane (Petrarch). Tlie net one-carbon homologation so effected is known as the Amdt-Eistert synthesis. 

The Henry reaction, or nitroaldo reaction, is one of the classic carbon-chain formation methods utilized in organic synthesis. It involves the condensation of nitroalkanes with aldehydes or ketones in the presence of bases (often catalytic amount) to afford the mixtures of diastereomeric 2-nitroalcohols, which in turn can be converted into other useful synthetic intermediates, such as 2-aminoalcohols, a-hydroxyketones, homologous ketones, and perhaps most importantly, nitroalkenes through various functional transformations. 

SN2 reactions of primary organolithium compounds on PMMA in dilute homogeneous solution may be considered as a model system where all the important reaction parameters may be controlled they allow both a quantitative analysis of PMMA chain reactivity and the synthesis of well defined ketonic copolymers within a wide range of possible structural variations. The two homologous series of organolithium compounds and the corresponding reaction conditions we selected are given below ... 

Arndt, F. Eistert, B. Ber. Dtsch. Chem. Ges. 1935, 68, 200. Fritz Arndt (1885—1969) was bom in Hamburg, Germany. He discovered the Arndt—Eistert homologation at the University of Breslau where he extensively investigated the synthesis of diazomethane and its reactions with aldehydes, ketones, and acid chlorides. Fritz Arndt s chain-smoking of cigars ensured that his presence in the laboratories was always well advertised. Bernd Eistert (1902-1978), bom in Ohlau, Silesia, was Arndt s Ph.D. student. Eistert later joined I. G. Earbenindustrie, which became BASE after the Allies broke the conglomerate up after WWII. 

Hi) Carboxylic acids and derivatives. The haloform reaction on thienyl methyl ketones leads to thiophenecarboxylic acids, which can be treated with Raney nickel to produce the open-chain acids. This method has been used for the five-carbon homologation of carboxylic acids and to produce dicarboxylic acids (Scheme 51). Long-chain carboxylic acids may also be prepared by using dicarboxylic acid derivatives for the acylation of thiophenes (Scheme 52). In the synthesis of Queen substance, the precursor (213) has been generated by Raney nickel desulfurization of the appropriate thiophene-2-acetic acid derivative (79T329). 

A carbon chain may be extended by one unit by using the Arndt-Eistert synthesis. In the first step, an acyl halide is treated with diazomethane to form the a-diazo ketone. This is then treated with water and silver oxide. The resultant product is the free acid. If an alcohol is used instead of water, then the related ester is formed. This is the best way of extending a chain by one unit if the carboxylic acid is available. The process of extension in this manner is called homologation. 

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