Addition sulfonyl azides

Sulfonylnitrenes are formed by thermal decomposition of sulfonyl azides. Insertion reactions occur with saturated hydrocarbons.255 With aromatic compounds the main products are formally insertion products, but they are believed to be formed through addition intermediates. 

A reaction known as diazo group transfer produces diazo barbituric acid from barbituric acid and p-toluene sulfonyl azide. Additional barbituric acid affords azo barbituric acid [7]. Subsequent complexation with a nickel (II) salt yields a greenish yellow pigment. 

In addition to previously described syntheses4-5 by diazo group transfer with deformylation,6 2-diazocyclohexanone has been prepared by two variants of this method. In one, the reaction of 2-(hydroxymethylene)cyclohexanone with -toluene-sulfonyl azide is carried out in ether/diethylamine, and an enamine is assumed to be formed as an intermediate 7 in the other, the sodium salt of the hydroxymethylene compound was treated with the lithium salt of p-carboxybenzenesulfonyl azide... 

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]. 

Addition of sulfonamides to olefins 9-39 Reduction of acyl sulfonamides 9-53 Reduction of sulfonyl azides... 

Sulfonyl azides react with olefins at a temperature which is much lower than the decomposition temperature of the azides (120-150°). The isolated products are aziridines and anils. The addition can be conceived as a result of two consecutive reactions, namely a 1,3-dipolar cycloaddition of the azide to the olefin immediately followed by decomposition of the formed unstable triazoline. As no triazolines can be detected, these reactions can also be regarded as a concerted addition with concomitant loss of nitrogen. 

The addition of aromatic sulfonyl azides to simple acyclic and cyclic dienes in a 1 2 molar ratio has been investigated.184 In no case was the triazoline... 

Amidines are also formed from less stable 1-hetaryl-220 and l-styryl-5-aminotriazolines.222,492,493 Thermolysis of the latter provides a method of synthesis of novel l-amino-2-azabutadienes (Scheme 176)492,493 Whereas cyanogen azide addition to dihydropyridines leads to bicycloazir-idines,241-243 addition of ethyl azidoformate yields the corresponding amidine 494 Likewise, indoles (103) react with picryl and sulfonyl azides to give... 

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). 

Iminocoumarins are formed in high yield from the Cu-catalysed multicomponent reaction of salicylaldehyde, alkynes and sulfonyl azides. It is considered that an initially formed ketimine reacts with the salicylaldehyde hydroxy function and an intramolecular nucleophilic addition to the aldehyde moiety completes the sequence (Scheme 29) <06OL4517>. 

Aromatic sulfonyl azides react with enol ethers of cyclic ketones to form arenesulfonyl imidate esters (96) with ring contraction, the addition-rearrangement process is very stereospecific (Scheme 63). 

The most widely used application of sulfonyl azides is in the azidation of enolates and other stabilized carbanions. The main challenge here is the avoidance of the diazo transfer reaction, which leads to diazo compounds and thus makes a diastereoselective animation impossible. Addition of the enolates to the sulfonyl azide proceeds rapidly at low temperatures (—78° or lower) to give the mesomeric ion 42 (Eq. 30).318 Reagents 41, the counter ion M+, the solvent, and the quenching reagent all influence the subsequent partition between azide and diazo compound. For enolates of esters (39) and N-acyloxazolidinoncs (40) the preferred reagent is trisyl azide (41a) 4-nitrobenzenesulfonyl azide (41c) promotes diazo transfer, and tosyl azide (41b) usually leads to mixtures of the two types of products. For ester enolates 39, either lithium or potassium as the... 

Nitrenes undergo addition reactions to neutral nucleophiles.60 51 Accordingly, they add to the nitrogen atom of pyridines, forming iV-imines. This method of preparation was described first by Curtius et a/.62-66 They heated aromatic sulfonyl azides in pyridine and obtained various A-sul-fonylimines [Eq. (5) ] the structures of which were not at that time recognized. They formulated sulfonyl nitrenes as intermediates in this reaction. 

Sulfonyl azides can be obtained smoothly by stirring an anhydrous methyl-alcoholic solution of the sulfonyl chloride for 1-2 hours with sodium azide and precipitating the product by addition of ice-water.706... 

As the formylation of a methyl ketone is usually highly selective for the methyl group, such formylated methyl ketones easily give the a-diazomethyl ketones by addition of a sulfonyl azide (LeBlanc and Sheridan, 1988). 

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. 

Sulfonyl azides participate in unique CuAAC reactions with terminal alkynes. Depending on the conditions and reagents, products other than the expected triazole 20 [118] can be obtained, as shown in Scheme 7.9. For example, N-sulfonyl azides are converted to N-sulfonyl amidines 21 when the reaction is conducted in the presence of amines [119]. In the aqueous conditions, N-acyl sulfonamides 22 are the major products [120,121]. In addition to amines and water, the latter can be trapped with imines, furnishing N-sulfonyl azetidinimines 23 [122]. 

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