Diazomethane chain extension with

An interesting report has been made of methylene insertion into the P-C linkage of a-(acyloxy)iminoalkylphosphonates derived from carbohydrates.181 This reaction system, using diazomethane, allows extension of the chain by a single carbon atom, with that atom (methylene group) attached directly to the phosphorus. 

This strategy did not appeal to Ruppert and White9 who preferred to make 36 by a chain extension route. A Reformatsky reagent gave 39 and dehydration and alkylation of malonate gave 36. Treatment with oxalyl chloride (COCl)2 followed by reaction with diazomethane gave... 

One important application of this reaction is the chain extension of acyl chlorides to their homologous esters, known as the Amdt-Eistert reaction. Notice that the starting material for the Wolff rearrangement is easily made from RCO2H by reaction of the acyl chloride with diazomethane the product is RCH2CO2H—the carboxylic acid with one more carbon atom in the chain. A CH2 group, marked in black, comes from diazomethane and is inserted into the C-C bond between R and the carbonyl group. 

This ester is one carbon atom short of the full side chain of grandisol, so an Arndt-Eistert reaction was used to lengthen the chain by one atom. First, the ester was converted into the diazoketone with diazomethane and, then, the Wolff rearrangement was initiated by formation of the carbene with a Amdt-Eistert chain extension of ester silver compound at the Ag(II) oxidation state. 

A useful reaction of acyl chlorides is with diazomethane. The initial product, a diazo ketone, undergoes a rearrangement with the expulsion of nitrogen and the insertion of a methylene group. This Arndt-Eistert reaction is a useful chain-extension procedure (Scheme 3.69). 

An interesting synthesis of silyl enol ethers involves chain extension of an aldehyde. Aldehydes are converted to the silyl enol ether of a ketone upon reaction with lithium (trimethylsilyl)diazomethane and then a drrhodium catalyst. Initial reaction of lithium(trimethylsilyl)diazomethane [LTMSD, prepared in situ by reaction of butyllithium with (trimethylsilyl)diazomethane] to the aldehyde (e.g., 37) gave the alkoxide addition product. Protonation, and then capture by a transition-metal catalyst, and a 1,2-hydride migration gave the silyl enol ether, 38. 

The Wolff rearrangement classical method for the chain extension of acids via rearrangement of an a-diazoketone intermediate. This technique has been used to conversion a-amino acids to P-amino acids. When S-2-aminobutanoic acid (5.110) was first converted to the phthalimido derivative, the acid moiety was treated with thionyl chloride and then diazomethane to give diazoketone 5.111. Wolff rearrangement and esterification generated methyl ester 5.112, which was converted to 3-aminopentanoic acid, 5.773.54... 

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. 

In an earlier chapter, we saw how to reduce the carbon chain by one methylene unit using the Hunsdiecker reaction. The opposite of this, namely the extension of the carbon chain by one unit, may be achieved with the Amdt-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. Suggest what is the pathway for this reaction. 

While the preceding malonic ester synthesis enables elongation of the labeled acetyl carbon chain by two carbon atoms, extension by one carbon is achieved when [ C]acetyl chloride is treated with diazomethane followed by quenching of the resulting diazoketone with gaseous HCl. The product in this example, l-chloro[2- C]propan-2-one (3), may... 

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