Azides tosyl, reaction with active methylene

The reaction of activated methylene groups with tosyl azide to yield the corresponding diazo derivatives proceeds in high yield [23]. The phase-transfer catalysed reaction is sensitive to the strength of base used the reaction of acetoacetic esters requires relatively mild conditions, otherwise diazoacetic esters are produced (Table 5.41). 

Diazo compounds have previously been prepared by a variety of methods. Some of these methods Include hydrazone oxidations, the reaction of diazomethane with acid chlorides,4 the reaction of activated methylene compounds with tosyl azide, decomposition of N-nitroso compounds, ... 

When active methylene compounds in basic medium react with tosyl azide, triazoles are never formed (Section IV,A,4), but the unstable triazoline intermediate undergoes a diazo transfer reaction in a Dimroth-type rearrangement.447 A typical example is the addition of tosyl azide to a 1,3-diketone... 

Diazo transfer.1 p-Toluenesulfonyl azide (which see) is commonly used for diazo-transfer reactions however, it has the disadvantage that the p-toluenesul-fonamide formed as one product is difficult to separate from the diazo compound. Hendrickson and Wolf1 found that the lithium and triethylarnine salts of p-carboxy-benzenesulfonyl azide are soluble in THF and acetonitrile, respectively, and that the triethylarnine salt of p-carboxybenzenesulfonamide is essentially insoluble in acetonitrile. In a standard procedure a solution of the carboxy azide is prepared in acetonitrile by addition of triethylarnine. The active methylene reactant is added and the carboxyamide salt separates within an hour. It is removed by filtration and the diazo product isolated by usual procedures. 2-Diazodimedone (2) was obtained by this procedure in 86% yield (the yield with tosyl azide is 42%). Several varia-... 

Methylene compounds activated by cyano or nitro groups (e. g., malonodinitrile, see Keller et al., 1975, and Stadler et al., 1975) exhibit a complex product pattern in classical diazo transfer reactions with tosyl azide. It seems, however, that ben-zothiazolium salts (Balli et al., 1978a), or such salts in combination with NaN3 in CH3OH-H2O (Kolobov et al., 1987) can be used for the synthesis of 2-diazo-nitriles. 

Although the direct transfer of a diazo-group to certain activated methylene compounds from tosyl azide under phase-transfer conditions has been reported, the method has not found general applicability with simple ketones. However, the replacement of tosyl azide with 2,4,6-tri-isopropylphenylsulphonyl azide now allows this reaction to proceed under phase-transfer conditions in the presence of 18-crown-6. Although the method may not offer significant advantages over established procedures for simple ketones, it is especially useful for cyclic and for hindered ketones. 

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