Norbomene aziridination

It has been reported by R.Scheiner that phenylazide forms triazoline compounds by 1,3-cyclic addition to unsaturated olefines such as n-butylethylene and norbornen(9 ). These triazolines are decomposed photochemically or thermally to give imine compounds and aziridine as is shown in scheme 1. These facts suggest that phenylazide may react with 3-methyl-1-butene to give triazoline in a similar reaction to that with norbomen. 

Numerous aziridines have been prepared by triazoline photolysis it is the principal route to the synthesis of N-arylaziridines. Photolysis of triazolines derived from simple79,113,144 and cyclic79,87,113 olefins as well as norbomene... 

Norbomene adds to photolytically produced ethoxycarbonylnitrene specifically at the exo face the same aziridine is produced in the thermal addition of ethoxycarbonyl azide, but via the triazoline rather than the nitrene, with much imine by-product. There can be problems of selectivity and rearrangements when one reacts ethoxycarbonylnitrene with more complex substrates, e.g. alkenic steroids. Ethoxycarbonylnitrene via a-elimination) adds to vinyl chlorides to give 2-chloroaziridines, which can be rearranged thermally to yield 2-chloroallyl carbamates. This nitrene also adds to enamines, giving an array of rearranged products. A modem discussion of the reactivities of ethoxycarbonylnitrene (electrophilic) in comparison with phthalimidonitrene (nucleophilic) towards alkenes of different electronic properties has tqipeared. ... 

By reaction of ethoxycarbonyl azide with norbomene, norbornadiene, benzonorbornadiene, and substituted derivatives the ew-4,5-dihydro-l,2,3-triazoles were isolated42,48-52 and successively converted to exo-aziridines either thermally, in methanol49, or photochemically, e.g., II42,52. 

Sulphonyl azides react with strained olefins, at temperatures below those required for the formation of the corresponding nitrenes, to give aziridines and anils. These reactions have been reviev ed recently . Benzenesulphonyl azide reacts with norbomene in acetonitrile solution at 55-60° to give the aziridine (282) (64%) in 2—3 hr ° ° . It was found, however, that when benzene was the solvent, a quantitative yield of 282 was obtained at room temperature in about 1-5 hr ° . 

Although thermolysis of triazoline can also, in certain cases , lead to aziridines, mixtures with azomethines usually result, and the photochemical process is preferable. The triazolines formed from acyl ° or sulphonyl azides are unstable and the corresponding aziridines can be obtained directly. The reaction of norbomene and benzoyl azide at 40° yielded the aziridine (128) directly... 

Fascinating rearrangements of aziridines have been applied to the synthesis of diterpene alkaloids by Wiesner and co-workers (Scheme 40). For example, the ester 217, prepared from cyclopentadiene carboxylate (215) and the benzyne precursor 216 by a Diels-Alder reaction, was converted to the aziridine 218 by treatment with benzenesulfonyl azide in 83% yield. When the aziridine 218 was heated with water for 24 h, the hydroxy ester 219 was obtained in 97% yield subsequent oxidation with the Jones reagent afforded the ketone 220. This rearrangement is analogous to that of the benzenesulfonylaziridine of norbomene. ... 

Note, however, that the reaction of methyl azidoformate with the strained olefin norbornene (11 proceeds by a 1,3-cycloaddition to give the unstable triuzoline adduct (2), which decomposes in refluxing toluene to give the aziridine (3,40%) theimide (4, S3%),gndjtyn-2>norbomene-7-methylcurbamBte (5). ... 

Photolysis is sometimes superior to thermolysis as a means of converting triazolines into aziridines. The cycloadduct 40 formed from azidobenzene and norbomene provides an example it is cleanly photolyzed to give the aziridine 41 (Scheme 6.20) but its thermal decomposition leads to a mixture of products. ... 

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