Cycloaddition reactions aziridines

Sulfonium ylides may be added to C N double bonds to yield aziridines in a formal [1 -t-2]-cycloaddition. Alkyl azides are decomposed upon heating or irradiating to yield ni-trenes, which may also undergo [ 1 + 2 -cycloaddition reactions to yield highly strained hetero-cycles (A.G. Hortmann, 1972). 

More recently, Cheeseman and coworkers have investigated cycloaddition reactions of 2,6-dioxypyrazines (80jCS(Pl)1603). 2,6-Dihydroxy-3,5-diphenylpyrazine (77) reacts with electron deficient dienophiles such as iV-phenylmaleimide, diethyl maleate and diethyl fumarate (Scheme 26) to yield adducts of the 3,8-diazabicyclo[3.2.1]octane class such as (78). This reaction is believed to proceed by way of the betaine (79) and has precedent (69AG(E)604) in that photolysis of the bicyclic aziridine (80) generates analogous betaines which have been trapped in cycloaddition reactions. 

Cycloaddition reactions of aziridines with a wide assortment of dipolarophiles have been studied. The reaction of dialkyl azodicarboxylates with the cf5-aziridine (27) is stereospecific... 

Cycloaddition reactions of aziridine-2-carboxylic esters have also been used... 

The highly strained and reactive 2iT-azirines have been extensively studied for various synthetic purposes, such as ring expansion reactions, cycloaddition reactions, preparation of functionalized amines and substituted aziridines. The older literature on azirines in synthesis has extensively been reviewed [69]. Concerning azirines with defined chirality only scarce information is available. Practically all reactions of azirines take place at the activated imine bond. Reduction with sodium borohydride leads to cz5-substituted aziridines as is shown in Scheme 48 [26,28]. 

The 1,3-dipolar cycloaddition reactions to unsaturated carbon-carbon bonds have been known for quite some time and have become an important part of strategies for organic synthesis of many compounds (Smith and March, 2007). The 1,3-dipolar compounds that participate in this reaction include many of those that can be drawn having charged resonance hybrid structures, such as azides, diazoalkanes, nitriles, azomethine ylides, and aziridines, among others. The heterocyclic ring structures formed as the result of this reaction typically are triazoline, triazole, or pyrrolidine derivatives. In all cases, the product is a 5-membered heterocycle that contains components of both reactants and occurs with a reduction in the total bond unsaturation. In addition, this type of cycloaddition reaction can be done using carbon-carbon double bonds or triple bonds (alkynes). 

Cycloaddition reactions of dimethyl benzylidenemalonate 262 with azides provide triazolines 263. All compounds 263, except one with R = Ph, are stable in xylene at 110 °C. The phenyl derivative eliminates molecular nitrogen to give dimethyl l,3-diphenylaziridine-2,2-dicarboxylate 264. At elevated temperature, the aziridine system is not... 

The ring opening of an aziridine can also occur in an intramolecular fashion, as observed in the formal [3+2] azitidine-allylsilane cycloaddition reaction of 142. These substrates were used for the preparation of both 5-5 and 6-5 fused ring systems <99T8025>. 

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