Aryl sulfonyl azide

Diazo transfer to pyrazolidone (39) using azidinium salt (38) affords diazo pyrazolidone (41) and imine 40 this method has proved superior to the aryl sulfonyl azide reactions in cases where azo coupling occurs. 

Scheme 5.34 Proline-catalysed sulfamidation of hydratropaldehyde with an aryl-sulfonyl azide.

Substituted aryl sulfonyl azides decompose at elevated temperatures to nitrenes and add to natural rubber ... 

Fig. 3. The reaction of aryl sulfonyl azides with polyisoprene...

The objectives of the chemical modification of natural rubber include the enhancement of chemical and physical properties. It is possible to predict both the conditions (reaction in latex or in dry rubber) and the scale of such modification (usually 1 mole and, from these criteria, to define possible modifying reagents. The thermal ene reaction is shown to be particularly valuable. A new cycloaddition reaction of aryl sulfonyl azides to natural rubber is also promising. 

A CuI/DMEDA-catalyzed intramolecular coupling of A-unprotective amidines 181 has been used for assembling 1,2,4-Benzothiadiazine 1,1-dioxides 182, another important class of heterocycles for pharmaceutical design (Scheme 63) [108]. Because the preparation of the amidines 181 could be achieved via a Cul-catalyzed three-component reaction of 1-alkynes, ammonium salts and aryl sulfonyl azides, a more efficient one-pot sequential process has been developed for the synthesis of 182 from these reagents. 

When 2-alkyl-3-keto esters or 2-aryl-3-keto esters are treated with sulfonyl azides under basic conditions, nucleophilic deacylation occurs to yield 2-alkyl/aryl-2-diazo esters [960-963]. Nucleophilic deacylation can also be used to convert acceptor-substituted diazoketones into the corresponding acceptor-substituted diazomethanes [964,965]. In all these deacylation reactions it is the most electrophilic carbonyl group which is attacked by the nucleophile and cleaved off. 

Aryl azide, acyl azide, sulfonyl azides, and azidoformate add to olefins by a 1,3-dipolar cycloaddition mechanism to yield triazoline. This addition also occurs with other unsaturated systems such as a,/S-unsaturated olefins, enam-ines, and cynamines [48]. 

Nitrene intermediates are formed in the thermal decomposition reactions of most alkyl azides, aryl azides, sulfonyl azides, and azidoformates. Some decompositions, however, must be regarded as proceeding by a synchronous mechanism. They are discussed in this section. 

To compare the reactivity of different classes of organic azides, the region is determined in which the rate constant for the decomposition reaction is of the order 10 to 10 min.-1 Table IIUI>-1M shows the results. The decomposition temperature decreases in the order alkyl and aryl azides > azidofor-mates and sulfonyl azides > acyl azides. The difference in reactivity between acid azides and alkyl or aryl azides can be explained easily in terms of resonance stabilization in the azide... 

Whereas aryl, acyl, and sulfonyl azides decompose in the presence of aluminum trichloride in benzene solution only with evolution of N , alkyl azides also split oif significant amounts of N,-.1 -18 At 50° alkylbenzenes and azomethines are obtained. In order to explain these results, Kreher and Jager suggested that two intermediate complexes may be formed (Scheme IV). According to Goubeau, Allenstein, and... 

Mattay et al. synthesized triazolinofullerenes 180 by the thermal [3 + 2] cycloaddition of aryl and sulfonyl azides 179 with C6o [263,291], Thermal extrusion of N2 predominantly leads to the formation to the opened [5,6]-bridged aza-fulleroids 182, whereas the major products formed by photolysis of triazolinofullerenes are the closed [6,6]-bridged aziridinofullerenes 181 (Scheme 67) [292,293],... 

The synthesis of novel azetidine derivatives remains the subject of intensive study. New procedures for the preparation of this class of compounds include, e.g., rearrangement of /3,7-aziridino-a-amino esters <2007OL4399>, copper-catalyzed multicomponent reactions of terminal alkynes, sulfonyl azides, and carbodiimides <20070L1585>, regioselective addition of 1,3-dicarbonyl dianions to iV-sulfonyl aldimines <2007T4779>, elaboration of a-amino acids <2007TL2471>, palladium-catalyzed iV-arylation of azetidines <2007S243> and... 

Aryl azides (such as 13) can be easily prepared from their corresponding amines (12) in one or two steps. Three examples are given in Scheme 2a. The most common method is the diazotization of the amine with sodium nitrite under acidic conditions (giving diazonium species 14), followed by addition of sodium azide in an aqueous medium (route i in Scheme 2a) [44], In 2003, the synthetic method was improved by application of triflyl azide (TfN3), which allowed a one-step conversion and gave improved yields (route ii in Scheme 2a) [45]. Recently, the development of sulfonyl azides 15 (with R = imidazole [46] or R = benzotriazole [47]) was reported these proved to be more stable reagents and allowed a conversion under mild conditions (route iii in Scheme 2a). 

Scheme 2 Preparation and examples of aryl azides, (a) Three possible routes for the conversion of an aryl amine into its aryl azide (i) via diazotization [44], (ii) by the use of triflyl azide [45], and (iii) with sulfonyl azides 15 (R = imidazole [46] or R = benzotriazole [55]). (b) Examples of substituted aryl azides...

Sulfonyl azides 3 allow the introduction of an NH2+ synthon, and alkyl or aryl azides prepared with these reagents can be reduced or hydrolyzed to primary amines, [Id, 2],... 

Sulfonyl Azides. Alkyl- and arylmagnesium halides,305 306 as well as alkyl-307, aryl- (see Eq. 70),308-312 and heteroaryllithium313 reagents add to sulfonyl azides to give triazene salts which may be reduced to amines 305 310 312 Gr converted into azides. The latter reaction has been accomplished by an aqueous workup with the highly hindered 2,6-dimesitylphenyl azide,314 whereas quenching with aqueous potassium hydroxide (see Eq. 72)305,315 sodium bicarbonate,313 or sodium pyrophosphate305,316 (see Eqs. 67 and 74) is necessary with other arenesulfonyl azide adducts. Thermolysis of the dry triazene salts also leads to azides,307,308 but because of the hazards involved, this procedure is not recommended. 

Based upon their previous studies with DEAD prompted dehydrogenation of tertiary amines and tandem reaction with sulfonyl azides, [37] Li believed that DEAD would provide the desired iminium ion intermediate 32 without the need for an aryl substituent (Scheme 19). 

The influence of the organic moiety of the azide in cylcoadditions to enol ethers is analogous to that in additions to enamines. Comparative cycloadditions of 4-(methoxyphenyl)-, 4-(nitrophenyl)-, and 4-toluene-sulfonyl azide to 2,3-dihydro-furan show that the rate of cycloaddition increases dramatically in the sequence mentioned (Huisgen et al., 1965). Yet, the dihydrotriazoles formed (2.174) are stable only in the case of the first aryl azide mentioned. With 4-toluenesulfonyl azide the product of dediazoniation (2.175) was the only compound detected (96% yield). Analogous results were obtained with 3,4-dihydro-2//-pyran. 

A-Sulfonylamidines can be prepared by three-component coupling [31] of alkynes (R = alkyl, aryl or silyl), sulfonyl azide and amine, which is known as click chemistry. [32] The use of alkyl azides in place of sulfonyl azide without a copper catalyst results in the formation of 1,2,3-triazoles (Scheme 3.18). This reaction shows substrate tolerance to each component. Reaction with an optically active amino ester is performed without racemiza-tion. A-Boc-ynamide (R = NPhBoc) can act as the alkyne component in the synthesis of N-Boc-aminoamidines [33]. 

Apart from the utilization of aryl- and vinyl-diazoacetates that can achieve the moderate to high chemo-, regio-, and enantioselectivity in intermolecular asymmetric C—H bond insertion reactions, Af-sulfonyl-l,2,3-triazole 11 was found to be able to function as an alternative carbene precursor for diverse transformations (Scheme 1.4). One advantage for using the N-sulfonyl-1,2,3-triazole is that it could be easily prepared by the Cu -catalyzed azide-alkyne cycloaddition (CuAAC) reaction, and in some cases, delicately designed reactions can be conducted in a one-pot procedure starting from alkynes and sulfonyl azides. Moreover, since there exists an inherent equilibrium... 

The reaction of sulfonyl azides with terminal alkynes is an interesting exception. Whereas aryl and alkyl azides react with activated alkynes to give the corresponding 1,2,3-triazoles, intermediate sulfonyltriazoles result in the formation of different products. In the presence of amines, N-sulfonyl azides are converted to M-sulfonyl amidines, whereas under aqueous conditions, M-acylsulfonamides are the major products [76-78]. Nevertheless, Fokin et al. reported conditions for the successful formation of N -sulfonyl-1,2,3-triazoles 105 shown in Scheme 22 [79]. 

Although azide reagents have been utilized in a number of chemical transformations, to date PS-TsA has only been utilized for the direct transfer of a diazo function to methylene groups flanked by either two carbonyls (eq 2), a carbonyl and an aryl sulfonyl (eq 3), or the methylene of lO/ anthracen-9-one. Diazodicarbonyl compounds such as 5-diazo-2,2-dimethyl-[l,3]dioxane-4,6-dione, 2-diazo-3-oxo-butyric acid ethyl ester, lO-diazo-lO/ anthracen-9-one, 2-diazo malonic acid diethyl ester, and 2-diazo-3-oxo-butyric acid ter/-butyl ester, as well as... 

Related Reagents, p-toluenesulfonyl azide and methane-sulfonyl azide have been used widely for diazo transfer to stabilized enolates. The latter reagent simplifies isolation of the desired product, but is potentially explosive and must be handled with care. Relative to other aryl analogs, the electron-deficient p-nitrobenzenesulfonyl analog favors diazo transfer to imide enolates. ... 

N-[6-dimethylamino)-5-aryl(alkyl)-2-(trichloromethyl)pyrimidin-4-yl]-4-aryl(alkyl)sulfonamides 63 in moderate-to-good yields starting from terminal alkynes, sulfonyl azides, trichloroacetonitrile, and 1,1,3,3-tetramethylguanidine (Scheme 27) (13SL165). 

A facile access to A-sulfonylimidates and their synthetic utility for the transformation to amidines and amides, (b) E. J. Yoo, S. H. Park, S. H. Lee, S. Chang, Org. Lett. 2009, 11, 1155-1158. A new entry of copper-catalyzed four-component reaction facile access to a-aryl P-hydroxy imidates. (c) R. Husmann, Y. S. Na, C. Bohn, S. Chang, Chem. Commun. 2010, 46, 5494—5496. Copper-catalyzed one-pot synthesis of a-functionalized imidates. (d) W. Song, W. Lu, J. Wang, P. Lu, Y. Wang, J. Org. Chem. 2010, 75, 3481-3483. A facile route to y-nitro imidates via four-component reaction of alkynes with sulfonyl azides, alcohols, and nitroolefins. (e) G. Murugavel, T. Punniyamurthy, Org. Lett. 2013, 15, 3828—3831. Novel copper-catalyzed multicomponent cascade synthesis of iminocoumarin aryl methyl ethers. 

The types of reaction open to a nitrene are broadly similar to those undergone by carbenes, but the reactivity of nitrenes is considerably lower. Nitrenes are less indiscriminate than carbenes in their reactions with primary, secondary, and tertiary carbon-hydrogen bonds, for instance, and nitrenes are also somewhat electrophilic, preferring an 0-H over a C-H bond. By far the most frequently used nitrene source is an aryl azide (see Table IV). The derived aryl nitrenes are much less reactive than a-keto, a-sulfonyl, or a-phosphoryl nitrenes, but the use of these acyl nitrenes is ruled out by the high chemical reactivity of the precursor species acyl azides, sulfonyl azides, and phosphoryl azides. 

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