in this way by treating methyl phenylacetate with p-acetamidobenzenesulfonyl azide in the presence of base. The mechanism involves attack of the enolate at the terminal nitrogen, proton transfer, and expulsion of the anion of the sulfonamide. Use of the β-carbonyl aldehyde leads to a deformylative variant of the Regitz transfer, which is useful for the preparation of diazo compounds stabilized by only one carbonyl group. From N-alkyl-N-nitroso compounds Diazo compounds can be obtained in an elimination reaction of N-alkyl-N-nitroso compounds, such as in the synthesis of diazomethane from Diazald or MNNG: (The mechanism shown here is one possibility. For an alternative mechanism for the analogous formation of diazomethane from an N-nitrososulfonamide, see the page on Diazald.) From hydrazones Hydrazones are oxidized (dehydrogenation) for example with silver oxide or mercury oxide for example the synthesis of 2-diazopropane from acetone hydrazone. Other oxidizing reagents are lead tetraacetate, manganese dioxide and the Swern reagent. Tosyl hydrazones RRC=N-NHTs are reacted with base for example triethylamine in the synthesis of crotyl diazoacetate and in the synthesis of phenyldiazomethane from PhCHNHTs and sodium methoxide. Reaction of a carbonyl group with the hydrazine 1,2-bis(tert-butyldimethylsilyl)hydrazine to form the hydrazone is followed by reaction with the iodane difluoroiodobenzene yields the diazo compound: From azides One method is described for the synthesis of diazo compounds from azides using phosphines: Reactions In cycloadditions Diazo compounds react as 1,3-dipoles in diazoalkane 1,3-dipolar cycloadditions. As carbene precursors Diazo compounds are used as precursors to carbenes, which are generated by thermolysis or photolysis, for example in the Wolff rearrangement. As such they are used in cyclopropanation for example in the reaction of ethyl diazoacetate with styrene. Certain diazo compounds can couple to form alkenes in a formal carbene dimerization reaction. Diazo compounds are intermediates in the Bamford-Stevens reaction of tosylhydrazones to alkenes, again with a carbene intermediate: In the Doyle-Kirmse reaction certain diazo compounds react with allyl sulfides to the homoallyl sulfide. Intramolecular reactions of diazocarbonyl compounds provide access to cyclopropanes. In the Buchner ring expansion diazo compounds react with aromatic rings with ring-expansion. As nucleophile The Buchner-Curtius-Schlotterbeck reaction yields ketones from aldehydes and aliphatic diazo compounds: The reaction type is nucleophilic addition. Occurrence in nature Two families of naturally occurring products feature the diazo group: kinamycin and lomaiviticin. These molecules are DNA-intercalators, with diazo functionality as their "warheads". Loss of N2, induced reductively, generates a DNA-cleaving fluorenyl radical. See also Azo compound Diazoalkane