Nitrenes sulfonyl

Sulfonic acid hydrazides, RSO2NHNH2, are prepared by the reaction of hydraziae and sulfonyl haUdes, generally the chloride RSO2CI. Some of these have commercial appHcations as blowiag agents. As is typical of hydrazides generally, these compounds react with nitrous acid to form azides (26), which decompose thermally to the very reactive, electron-deficient nitrenes (27). The chemistry of sulfonic acid hydrazides and their azides has been reviewed (87). 

Sulfonyl nitrenes react with benzene to produce appreciable yields of aromatic substitution products. The nitrene thermally generated in benzene from 229 gives a monosubstitution product. When the reaction is carried out in mesitylene as a solvent, the two sulfonylnitrenes react with mesitylene to afford 230 (equation 140)135. 

Insertion (see 12-12). Nitrenes, especially acyl nitrenes and sulfonyl nitrenes, can insert into C—H and certain other bonds, for example. 

V. ADDITION OF SULFONYL CARBENES AND SULFONYL NITRENES A. Sulfonyl Carbenes... 

Recently, Scott et al. have reported that a Cu complex bearing an axially chiral ligand (49) is an excellent catalyst for aziridination of 2,2-dimethylchromene and cinnamate esters (Scheme 36), though it is also less efficient for the reactions of simple olefins.157,158 On the basis of DFT investigation of the nitrenoid intermediate (50), one of the oxygen atoms of the A -sulfonyl group has been proposed to be interacting with the nitrene N-atom.158... 

Treatment of sulfonylamide tetrabutylanmionium salts RS02NH Bu4N+ in benzene with Xep2 gives the corresponding At-sulfonylazepines (68) via a proposed sulfonyl nitrene intermediate." ... 

A very reactive nitrogen atom is required to convert benzenes or naphthalenes into pyridines, and there are a number of such reactions which involve nitrenes or nitrenoid species. A number of substituted benzenes have been treated with sulfonyl diazide or carbonyl diazide and moderate yields of pyridines recorded (27CB1717). Thus p-xylene gives 2,5-dimethylpyridine there is no indication of the fate of the carbon atom which is lost. More controlled reaction is possible in intramolecular insertions. The examples in which o-nitrotoluene is converted into a derivative (759) of 2-acetylpyridine, and where 2,3-diazidonaphthalenes give 3-cyanoisoquinolines (760) are quoted in a review (81 AHC(28)231>. 

However, product smdies indicate that the chemistry of sulfonyl azides and nitrenes is complicated by rearrangement to form intermediates, such as 21. ... 

For monographs, sec Scriven Azides and Nitrenes-, Academic Press New York, 1984 Lwowski Nitrenes. Wiley New York. 1970. For reviews, see Scriven React. Interned. (Plenum) 1962,2, 1-54 Lwowski React. Interned. (Wiley) 1985, 3. 305-332.1981, 2, 315-334. 1978, 1. 197-227, Angew. Chem. Ini. Ed. Engl. 1967, 6. 897-906 [Angew. Chem. 79. 922-931) Abramovitch, in McManus. Ref. 1. pp. 127-192 Hiinig Helv. Chim. Acta 1971, 54, 1721-1747 Belloli J. Chem. Educ. 1971, 48, 422-426 Kuznetsov Ioffe Russ. Chem. Rev. 1989, 58, 732-746 (N- and O-nitrenes) Mcth-Cohn Acc. Chem. Res. 1987,20,18-27 (oxycarbonylnitrenes) Abramovitch Sutherland Fortsch. Chem. Forsch. 1970, 16. 1-33 (sulfonyl nitrenes) Ioffe Kuznetsov Russ. Chem. Rev. 1972, 41, 131-146 (N-nitrenes). 

Sulfonyl azides react with pyridine to give pyridine 1-sulfonylimides (e.g. 367). However, the analogous reaction with 2,4,6-trimethylpyridine gives some 3-(phenylsulfonylamino) derivative together with the 1-sulfonylimide. Nitrenes derived from photolysis of acyl azides also add to the nitrogen atom to form the corresponding pyridine A-imines (74AHC(17)220). 

Relative reactivity studies with primary, secondary, and tertiary C-H bonds have revealed the following order of selectivity phenylnitrene > carbethoxynitrene > sulfonyl-nitrene > car bene.88 ... 

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. 

Kwart and Kahn have found that benzenesulfonyl azide forms a complex with freshly reduced copper powder.189 190 This copper azide complex decomposes at a lower temperature than the pure sulfonyl azide. In refluxing methanol, benzene-sulfonamide (27) is isolated as the major product. In the presence of dimethyl sulfoxide, N-benzenesulfonyldimethyl-sulfoximine (28) is obtained in almost quantitative yield. In cyclohexene solution benzenesulfonamide (29), N-benzenesul-fonyl-7-azabicyclo[4.1.0]heptane (30), and 1-cyclohexenylben-zenesulfonamide (31) are isolated as the main reaction products. According to the authors, Schemes VII and VIII represent an acceptable interpretation of the experimental data.189 190 In pure alcohol, the decomposition should occur by two competitive reactions (Scheme VII) producing benzenesulfonamide together with a ketone and oxidized copper. These last two products have indeed been observed in the reaction mixture. In the presence of DMSO, it seems that a copper-nitrene intermediate is formed which is trapped by DMSO. In cyclohexene solution, the authors have observed that the aziridine (30) disappears from the product composition when DMSO is added. The yield of enamine 31, however, is... 

Bolm and coworkers discovered that inexpensive and easy to handle iron(III) acetylacetonate [Fe(acac)3] was also capable of catalyzing nitrene transfer to sulfides and sulfoxides using various sulfonyl amides in combination with iodosylbenzene (Scheme 3.58) [174]. 

Using / -nitrobenzene sulfonyl carbamates as the source of nitrene, the reaction needs to be activated either by a carbonate in the presence of phase-transfer reagent or by sonication. Yields are only moderate and this reaction cannot be regarded as being preparatively useful.101,102... 

Acyl nitrenes are highly reactive but unfortunately their precursors, acyl azides, are chemically reactive, e.g. they acylate amino groups. While sulfonyl- and alkoxycarbonyl azides are somewhat less reactive than acyla-zides, and the nitrenes derived from them are highly reactive (Lwowski, 1970 and for sulfonyl nitrenes see Abramovitch et al., 1981 and references therein), the azides must be irradiated in the UV, below 300 nm. Phos-phorylnitrenes are the most reactive nitrenes known and will insert into CH bonds in the presence of hydroxyl groups (Breslow et al., 1974). Again, photolysis occurs at ultraviolet wavelengths. 

The lifetime of the nitrene is governed by its stability this in turn governs its reactivity with respect to added substrates. The most reactive nitrenes, i.e., those having electron acceptor substituents such as sulfonyl and acyl nitrenes are extremely short-lived [6b], In contrast, amino nitrenes that are stabilized by resonance can be stored for several hours at —78 °C [11]. 

More recently, Tardella and co-workers disclosed the use of this reagent in the synthesis of Af-(ethoxycarbonyl)-a-amino ketones from enamines and nitrene 18 [12b]. Their attempts to obtain asymmetric induction started with the use of proline-derived optically active enamines of cyclohexanone. Slow addition of sulfonyl-oxycarbamate 6e (1 equiv.) to a stirred solution of the enamine 19 and triethylamine (1 equiv.) in dichloromethane at room temperature, followed by work-up with petroleum ether and silica gel chromatographic purification afforded the aminated product 20 in low yield and good enantiomeric excess [12c] (Scheme 8). 

Among other convenient nitrene precursors are chloramine-T (A-chloro-A-sodio-p-toluenesulfonamide), bromamine-T, sulfonamides in the presence of (diacetoxyiodo)benzene and various transition metal catalysts, and sulfonyl azides in the presence of ruthenium complexes . 

The reaction of ethoxycarbonyl nitrene, generated by decomposition of the azide or by the a-elimination method, with enamines gave mixtures of aminimides and a-amino ketone derivatives30.. V-Methoxycarbonyl. A -cyano and N-sulfonyl azides reacted with 1,2-31 and 1,4-dihy-dropyridines32 to afford directly the corresponding aziridines 9 and 10. The configuration of the aziridine 10, relative to the R substituent, was not determined. 

The chiral sulfur(vi) reagent, A -[[J-(/i-toluenesulfonimido)-6 -(/i-tolyl)]sulfonyl]amide 431 upon reaction with iodosylbenzene 426 affords in situ the chiral iminoiodane 432. In the presence of Cu(MeCN)4PF6 as catalyst, iminoiodane 432 forms the complex 433 that very efficiently transfers the nitrene moiety together with the stereogenic information under stoichiometric conditions to a variety of alkenes 414 the corresponding aziridines 434 were obtained with diastereoselectivities up to 60% (Scheme 112) <20040L4503>. 

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