Diazo transfer reagent

Balli and Felder (1978) and Balli and Ritter (1981) showed that diazo transfer can be applied advantageously to the diazotization of sufficiently nucleophilic heteroaromatic compounds such as 5-hydroxy- and 5-amino-3-methyl-l-phenyl-pyrazole if 3-ethyl-2-azido-benzthiazolium tetrafluoroborate (2.50) is used as diazo transfer reagent (for other applications of this diazo transfer reagent see Zollinger, 1995, Secs. 2.6-2.8). The diazonio group is introduced in the 4-position (2.51). 

What happens to that second molecule of diazomethane By collecting a proton it turns into the very reactive diazonium salt, which collects a chloride ion, and MeCl is given off as a gas. The second method uses tosyl azide, which is known as a diazo transfer reagent—it s just N2 attached to a good leaving fcroup. 

Caution Although the mixture of dodecylbenzenesulfonyl azides is the safest of a group of diazo transfer reagents,2 one should keep in mind the inherent instability, shock sensitivity, and explosive power of azides. All users should exercise appropriate caution. 

McGuiness, M., Schechter, H. Azidotris(diethylamino)phosphonium bromide a self-catalyzing diazo transfer reagent. Tetrahedron Lett. 

Green, G. M., Peet, N. P., Metz, W. A. Polystyrene-Supported Benzenesulfonyl Azide A Diazo Transfer Reagent That Is Both Efficient and Safe. J. Org. Chem. 2001, 66, 2509-2511. 

Naphthalenylsulphonyl azide has been advocated as a diazo transfer reagent of a capability superior to that of/ -toluenesulphonyl azide s. 

There are two reactive methylene groups in a,y,e-trioxo compounds of the type 2.123. With one equivalent of diazo-transfer reagent, 2//-3,4-dihydropyrazol-4-one... 

Very recently, Sezer and Anag (1994) found that 2-azido-l-ethylpyridinium tetra-fluoroborate is a suitable diazo transfer reagent for the introduction of diazo groups... 

Polymer-bound arylsulfonyl azides have been tested as diazo transfer reagents (Roush et al., 1974 Diirr et al., 1981). Yields with diethyl malonate and acetylace-tone are slightly lower than those with 4-toluenesulfonyl azide. In contrast to these compounds with two neighboring activating groups, yields with monoactivated methylenes (ethyl propionate and cyclohexanone) are much lower. This method is therefore, not recommended in the described form. 

As mentioned at the beginning of this section, diazo compounds may act as diazo transfer reagents. Nevertheless, few cases are known (see however, the addition of diazomethane to alkynes in Sect. 2.8). A lucid example within the framework of this section is the formation of ethyl diazoacetate (2.161) and 4-nitroaniline from the triazene 2.160, which is the A-azo-coupling product of the aromatic diazonium ion... 

If cyanogen azide or 2-azido-3-ethylbenzothiazolium tetrafluoroborate is used as diazo transfer reagent, only the diazoamidines are detected (Regitz et al., 1981a). This is consistent with the interpretation of the results of Table 2-3. 

The synthesis of S-N-azido derivatives of N-acetylneuraminic acid has been accomplished by both enzymatic and chemical methods. In particular, SchmidP and Wong described the introduction of the azido group from known sialosyl donors 11a and 11b respectively by using trifluoromethanesulfonyl azide (triflic azide, TfNs) as the diazo transferring reagent (Scheme 3). 

The direct diazo transfer from sulfonyl azides to methyl ketones is usually not a practicable process, with the exception of the a-diazotization of ketones with 2,4,6-triisopropylbenzenesulfonyl azide under phase-transfer conditions. However, diazomethyl ketones amenable to the Arndt-Eistert reaction can be easily prepared in two steps by a formylation-deformylation diazo-transfer sequence (Regitz procedure ). A related practical method advantageously applies the detrifluoroacetylation of a-trifluoroacetyl ketones tScheme 3 a). The preparation of 2-diazo-1,3-dicarbonyl compounds is commonly best performed with p-toluenesulfonyl azide (TsNg) as the diazo-transfer reagent tScheme 3.9h). > An issue... 

Reagent for Diazo-function Transfer. The title reagent has heen called a safer diazo-transfer reagent, and is a mixture of 12 or more isomeric p-dodecylhenzenesulfonyl azides, ranging hy HPLC from 24% to 1% in area and giving essentially a single spot hy TLC. ... 

Another advantage of PS-TsA as a diazo transfer reagent is that the polystyrene-supported reagent is thermally stable and is... 

Transformation of Primary Amines into Azides. Since its introduction by Ruff in 1965, TfNs has been widely used as a diazo transfer reagent that converts primary amines into azides. Recently, Wong further popularized this reaction with addition of various metal catalysts (e.g., Cu +, Zn +, and Ni +), which dramatically increase the efficiency of this transformation with shortened reaction times.Neomycin, for example, with six primary amino groups, can be converted to its per-azido counterpart in 82% yield using CUSO4 as a catalyst (eq 17). The same reaction proceeds in merely 20% yield in the absence of catalysts under the same conditions. ... 

A polymeric tosyl azide has been prepared (Roush et al., 1974) and used as a diazo transfer reagent (Scheme 12-18). With its help, j8-diketones can be converted into diazodiketones. The polymeric reagent, unlike its low-molecular-weight analog, is not explosive. 

Recently the use of imidazole-1-sulfonyl azide hydrochloride (185) as a diazo transfer reagent has been reported (Scheme 3.25). This compound is a crystalline, shelf-stable... 

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