Diazomethane reaction with 1,2-dicarbonyl compounds

The reactions of heterocyclic 1,2-dicarbonyl compounds with diazomethane, which were studied by Eistert and his co-workers in... 

With a range of methods available for the formation of 1,3-dicarbonyl compounds, the dicarbonyl diazomethanes can be readily prepared via a simple diazo transfer reaction with sulfonyl azide. This has made a vast array of dicarbonyl diazomethanes available, which enhances the versatility in organic synthesis. A selection of examples from recent literature to illustrate the versatility of the cyclopropanation using dicarbonyl diazomethane in the construction of natural products as well as other biologically active compounds is described below. 

Compared to diazonium salts, diazo compounds are generally much less reactive towards nucleophiles than towards electrophiles. As a result of this azo coupling reactions of diazo compounds are the exception rather than the rule. Electron withdrawing substituents on the diazo carbon increase the reactivity towards nucleophiles. Consequently the ability to undergo azo coupling reactions increases from diazomethane to diazocarbonyl- and 2-diazo-l, 3-dicarbonyl compounds. Among the earliest reactions known were those with cyanide and sulfite ions Tertiary phosphines, as opposed to amines, can form stable addition complexes with diazoalkanes probably due to the ability of phosphorus to stabilize the betaine with its empty d orbitals (6). 

Substituted 2-diazopentane-l,3,5-triones have been transformed into 3,5-disubstituted-4-hydroxypyrazoles <2003RJ01644>. Disubstituted pyrazoles were obtained by the reaction of 4-aryl-2,4-oxobutanoic acid aryl amides with diazomethane or diazoethane <2002RJ0840>. The reaction of 2-methylene-l,3-dicarbonyl compounds with ethyl diazoacetate gave 4,5-dihydro-l//-pyrazole derivatives in good yields, which were stable for several months at room temperature <2001CPB1638>. 

Eistert, B. and Bock, G., Reactions of a-dicarbonyl compounds and quinones with diazoalkanes. II. The reaction of some substituted p-benzoquinones with diazomethane to p-epoxymethylcyclo-... 

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