Nitrenes review

Nltrenes (s. a. Sulfonylnitrenes) N-heterocyclics via review 18,338 suppl. 27 review 26, 630 N-Nitrenes, review 23, 381 suppl. 27... 

The preparation and properties of these tertiary aminimides, as weU as suggested uses as adhesives (qv), antistatic agents (qv), photographic products, surface coatings, and pharmaceuticals, have been reviewed (76). Thermolysis of aminimides causes N—N bond mpture foUowed by a Curtius rearrangement of the transient nitrene (17) intermediate to the corresponding isocyanate ... 

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). 

In 1999, Bob Atkinson wrote [1] that aziridination reactions were epoxida-tion s poor relation , and this was undoubtedly true at that time the scope of the synthetic methods available for preparation of aziridines was rather narrow when compared to the diversity of the procedures used for the preparation of the analogous oxygenated heterocycles. The preparation of aziridines has formed the basis of several reviews [2] and the reader is directed towards those works for a comprehensive analysis of the area this chapter presents a concise overview of classical methods and focuses on modern advances in the area of aziridine synthesis, with particular attention to stereoselective reactions between nitrenes and al-kenes on the one hand, and carbenes and imines on the other. 

The synthesis of sulfoximides and sulfimides has attracted considerable attention in recent years due to the potential utility of these compounds as efficient auxiliaries and chiral ligands in asymmetric synthesis (reviews [86-88]). Transition metal-catalyzed nitrene transfer to sulfoxides and sulfides is an efficient and straightforward way to synthesize sulfoximides and sulfimides, respectively. Bach and coworkers reported the first iron-catalyzed imination of sulfur compounds with FeCl2 as catalyst and B0CN3 as nitrene source. Various sulfoxides and sulfides were... 

Several reviews on the synthesis of aziridines have been published in the previous year. These publications include a review on the silver catalyzed addition of nitrenes (among other intermediates such as carbene) across a double bond <06EJOC4313> a review on sulfur ylide addition to imines to form aziridines <06SL181> a review on nitrogen addition across double bonds <06ACR194> a general review on functionalization of a,p-unsaturated esters with some discussion of aziridination <06TA1465>... 

These indices have been used to study the reactivity for a series of chlorobenzenes and a good correlation is observed, for example, between W and toxicity of chlorobenzene [41]. For a detail discussion of this concept and its applications, we refer the readers to a recent review [41,42]. For studying intramolecular reactivity, these philicity indices and local softness contain the same information as obtained from the Fukui functions, because they simply scale the Fukui functions. In some cases the relative electrophilicity and relative nucleophilicity may be used although they provide similar trends as s(r) and co(r) in most cases [43]. In the same vein, the spin-donicity and spin-philicity, which refer to the philicity of open-shell systems [44], could also be utilized to unravel the reactivity of high-spin species, such as the carbenes, nitrenes, and phosphinidenes [45]. 

Besides the applications of the electrophilicity index mentioned in the review article [40], following recent applications and developments have been observed, including relationship between basicity and nucleophilicity [64], 3D-quantitative structure activity analysis [65], Quantitative Structure-Toxicity Relationship (QSTR) [66], redox potential [67,68], Woodward-Hoffmann rules [69], Michael-type reactions [70], Sn2 reactions [71], multiphilic descriptions [72], etc. Molecular systems include silylenes [73], heterocyclohexanones [74], pyrido-di-indoles [65], bipyridine [75], aromatic and heterocyclic sulfonamides [76], substituted nitrenes and phosphi-nidenes [77], first-row transition metal ions [67], triruthenium ring core structures [78], benzhydryl derivatives [79], multivalent superatoms [80], nitrobenzodifuroxan [70], dialkylpyridinium ions [81], dioxins [82], arsenosugars and thioarsenicals [83], dynamic properties of clusters and nanostructures [84], porphyrin compounds [85-87], and so on. 

Although the Sharpless catalyst was extremely useful and efficient for allylic alcohols, the results with ordinary alkenes were very poor. Therefore the search for catalysts that would be enantioselective for non-alcoholic substrates continued. In 1990, the groups of Jacobsen and Katsuki reported on the enantioselective epoxidation of simple alkenes both using catalysts based on chiral manganese salen complexes [8,9], Since then the use of chiral salen complexes has been explored in a large number of reactions, which all utilise the Lewis acid character or the capacity of oxene, nitrene, or carbene transfer of the salen complexes (for a review see [10]). 

However, in the ground state, the main contributions to the resonance hybrid are due to forms 3a,b. Their importance increases going from diazopyrroles to the diazotetrazole, so that the diazo structure with cumulated double bonds, which has been extensively employed as a shortened form for the diazoazoles, does not seem to depict them correctly any more. Therefore, in continuation of this review, the diazoazoles will be represented by structure 3a unless other limiting forms better account for the observed reactivity. In fact, even the nitrene-like form, a heteroanalogue of 17, which is the one with highest energy, has been invoked to explain the reactivity in some cycloaddition reactions (86CC1127). 

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>. 

Nitrenium ions (or imidonium ions in the contemporaneous nomenclature) were described in a 1964 review of nitrene chemistry by Abramovitch and Davis. A later review by Lansbury in 1970 focused primarily on vinylidine nitrenium ions. Gassmann s ° 1970 review was particularly influential in that it described the application of detailed mechanistic methods to the question of the formation of nitrenium ions as discrete intermediates. McClelland" reviewed kinetic and lifetime properties of nitrenium ions, with a particular emphasis on those studied by laser flash photolysis (LFP). The role of singlet and triplet states in the reactions of nitrenium ions was reviewed in 1999. Photochemical routes to nitrenium ions were discussed in a 2000 review. Finally, a noteworthy review of arylnitrenium ion chemistry by Novak and Rajagopal " has recently appeared. 

Once the spectroscopy and dynamics of parent singlet phenylnitrene were understood, we began a systematic study of the effect of substitution on the kinetics of singlet phenylnitrenes. For most of the aryl azides of interest " the rate constants of singlet nitrene decay and product formation (triplet nitrene and/or ketenimine) are the same (Fig. 9). With these nitrenes, cyclization to substituted benzazirines is the rate-limiting step of the process of nitrene isomerization to ketenimine in a manner similar to the parent phenylnitrene. The only exception, o-fluorophenylnitrene, will be examined in detail in the last section of this review. 

For monographs, see Jones Moss Carbenes, 2 vols. Wiley New York, 1973-1975 Kirmse Carbene Chemistry, 2nd ed. Academic Press New York, 1971 Rees Gilchrist Carbenes, Nitrenes, and Arynes Nelson London, 1969. For reviews, see Minkin Simkin Glukhovtsev Russ. Chem. Rev. 1989, 58, 622-635 Moss Jones React. Intermed. (Wiley) 1985, 3, 45-108,1981,2, 59-133,1978, /, 69-115 Isaacs, Ref. 1, pp. 375-407 Bethell Adv. Phys. Org. Chem. 1969, 7, 153-209 Bethell, in McManus, Ref. 1, pp, 61-126 Closs Top. Stereochem. 1968, 3, 193-235 Herold Caspar Fortschr. Chem. Forsch. 1966, 5, 89-146 Rozantsev Fainzil berg Novikov Russ. Chem. Rev. 1965,34, 69-88. For a theoretical study, see Liebman Simons Mol. Struct. Energ. 1986, /, 51-99. 

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). 

JFor a review of arylnitrenes, sec Scriven Azides and Nitrenes Academic Press New York. 1984. pp. 95-204. 

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