Diazo acetaldehyde

Methyl-l-nitroso urea was subsequently shown to be a potent carcinogen (see Sect. 4.2), and its use is now discouraged. For the synthesis of diazoalkanes, for which no other route is described in the literature, N-alkyl-N-nitroso ureas may still be the reagent of choice. This is the case, for example, for diazo acetaldehyde (2.48), which was obtained (2-18) by Abdallah et al. (1983) by cleavage of A-(2,2-dimethoxy-ethyl)-AT-nitroso urea (2.47). The corresponding iV-nitroso urea was also used successfully for the preparation of 4-(2-diazoethyl)-2,3,3-trimethylcyclopentene (2.49) by Adam et al. (1985). Various other methods failed to lead to this diazoalkane. 

The carbon dioxide anion-radical was used for one-electron reductions of nitrobenzene diazo-nium cations, nitrobenzene itself, quinones, aliphatic nitro compounds, acetaldehyde, acetone and other carbonyl compounds, maleimide, riboflavin, and certain dyes (Morkovnik and Okhlobystin 1979). The double bonds in maleate and fumarate are reduced by CO2. The reduced products, on being protonated, give rise to succinate (Schutz and Meyerstein 2006). The carbon dioxide anion-radical reduces organic complexes of Co and Ru into appropriate complexes of the metals(II) (Morkovnik and Okhlobystin 1979). In particular, after the electron transfer from this anion radical to the pentammino-p-nitrobenzoato-cobalt(III) complex, the Co(III) complex with thep-nitrophenyl anion-radical fragment is initially formed. The intermediate complex transforms into the final Co(II) complex with the p-nitrobenzoate ligand. 

Photolysis of 59a in alcohols (ethanol or isopropanol) gave the corresponding indole 62 (R = H), by reductive diazo cleavage, together with acetaldehyde or acetone (66LA17). 

Conversion of stabilized diazo compounds to hydrocarbons does not depend upon the reducing action of ethyl alcohol, for the reaction takes place smoothly in acetone, ether, nitrobenzene, benzene, chloroform, apd carbon tetrachloride. No acetaldehyde is produced when ethanol is the solvent. In the absence of metals, however, when the stabilized salts of diazotized a-naphthylamine are treated with ethyl alcohol, acetaldehyde, naphthalene, a-ethoxynaphthalene, and tar are obtained. 

A similar change of mechanism is observed in the reaction of silyl-substituted diazo esters 559 with acetaldehyde and benzaldehyde. The Rh2(pfb)4-induced decomposition of allyl ester 559 (n = 1) in the presence of a carbonyl compound yields 1 1 adducts 560, whereas homoallyl ester 559 ( = 2) under the same conditions produces only 1 2 adducts 561 (94CB1537). 

Diazo transfer onto p-imino ketone (249) generally leads directly to 1,2,3-triazole (250). Benzoyl acetaldehyde anil produces 1-phenyl-4-benzoyl- 1,2,3-triazole (250) in 90% yield.1... 

---