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26.1.5.2 Method 2: Addition of Diazoalkanes to Aldehydes

DOI: 10.1055/sos-SD-026-00198

Figadère, B.; Franck, X.Science of Synthesis, (200526294.

The reaction of diazo compounds with aldehydes is an old reaction, but has not been extensively developed, probably due to the instability and toxicity of diazo compounds. The first report of such a reaction is the addition of the stabilized ethyl diazoacetate to benzaldehyde to give the corresponding β-oxo ester; reports of the addition of diazomethane and homologues appeared several years later.[‌9‌,‌10‌] The major products obtained in the reaction of aldehydes with diazomethane are the methyl ketone or the corresponding epoxide, a mixture of both is usually obtained (Scheme 3). The use of higher diazoalkanes with aliphatic aldehydes gives mainly the ketones, with yields ranging from 51 to 78%.[‌11‌] Aluminum trichloride catalyzes the reaction and prevents the formation of the epoxide ­product by forming an aluminum alcoholate which is less likely to attack the methyldiazonium site.[‌12‌] Other organoaluminum reagents (e.g., trimethylaluminum or aluminum triphenoxide) are highly effective for the transformation of aldehydes into the homologous ketones.[‌13‌]

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