New Methods of Preparative Organic Chemistry . Transfer of Diazo Groups

When an arenesulfonyl azide, particularly p ‐toluenesulfonyl azide, reacts, in the presence of a base, with a compound containing an active methylene group, the two hydrogen atoms of the active methylene group are replaced by a diazo group to form a diazo compound and an arenesulfonamide. The method may be used for the synthesis of the diazo derivatives of cyclopentadienes, cyclohexadienes, 1,3‐dicarbonyl, 1,3‐disulfonyl, and 1,3‐ketosulfonyl compounds, ketones, carbonic acid esters, and β‐iminoketones. Secondary reactions can lead to azo compounds and heterocycles such as 1,2,3‐triazoles, 1,2,3‐thiadiazoles, and pyrazolin‐4‐ones. Azidinium salts react in the same way, but in this case an acidic reaction medium is necessary, a fact that is sometimes advantageous.