Reactivity of Diaziridines

Diaziridines, discovered in 1958, six years after the oxaziridines, were almost immediately realized to be structural analogs of oxaziridines. Like these they showed oxidizing properties unexpected for other classes of organic nitrogen compound. Properties in common with oxaziridines include the rearrangement to open chain isomers on heating above 100 °C (for several diaziridines), and their hydrolytic behavior in acidic media, which leads to carbonyl compounds with conservation of the hetero-hetero bond. 

There are differences in the high temperature behavior. While oxaziridines almost always isomerize to acid amides, a similar reaction of diaziridines, which should lead to amidines, has not been observed. Sensitivity towards bases, often encountered in oxaziridines, is observed only in some special substituted diaziridines. The tendency of some classes of oxaziridines to transfer the nitrogen function also lacks in the diaziridine field. On homolytic reactions of diaziridines there are only a few observations. 

Substitution with conservation of the three-membered ring is more versatile in diaziridine chemistry, because the ring is somewhat more stable and because of the presence of two nitrogen atoms. 

Diaziridinones and diaziridinimines, discovered about 10 years later, add much to the versatility of the diaziridine field, especially due to valence isomerizations. 

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Dehydrogenation of diaziridines.2 The Swern reagent is more effective than Ag20 or NBS for oxidation of the diaziridines 1 to the diazirines 2, of interest because they are photolyzed to reactive carbenes. 

Photolysis of azirine (297), or thermolysis of the oxazaphosphole (298), affords reactive azomethines (299) and (300), respectively. These react with azodicarboxylates to give triazolines (301) and (302) as in Scheme 132 (74HCA1382, 73CB3421). The use of diaziridine (303) to afford the triazolidinone (304) in Scheme 133 (74JOC3198) may be compared with the reaction shown in Scheme 131. Thermal decomposition of the aziridine (305) proceeds via an ylide (306) which reacts with azodicarboxylate to afford the triazolidine (307) in very good yield (Scheme 134) (66JOC3924). For similar uses of ylides see (81HC(37)1, p. 516). 

In the diaziridine field many compounds are known bearing N-YL, A/-alkyl and A-acyl groups, but here no dramatic changes in reactivity are caused by A-substituents. N-Aryldiaziridines are underrepresented. The ring carbon is in the oxidation state of a carbonyl compound or, in the diaziridinones (5) and the diaziridinimines (6) that of carbonic acid. In single cases, diaziridine carbon bears chlorine or fluorine. 

It was not their reactivity but their chemical inertness that was the true surprise when diazirines were discovered in 1960. Thus they are in marked contrast to the known linear diazo compounds which are characterized by the multiplicity of their reactions. For example, cycloadditions were never observed with the diazirines. Especially surprising is the inertness of diazirines towards electrophiles. Strong oxidants used in their synthesis like dichromate, bromine, chlorine or hypochlorite are without action on diazirines. Diazirine formation may even proceed by oxidative dealkylation of a diaziridine nitrogen in (186) without destruction of the diazirine ring (75ZOR2221). The diazirine ring is inert towards ozone simple diazirines are decomposed only by more than 80% sulfuric acid (B-67MI50800). 

An interesting collection of reactive intermediates are involved in the decomposition of the diazo compound (35) or the diaziridine (36). The resulting carbene (37) in part rearranges to the silene (38) which is trapped as the silole (39), and in part rearranges to the silabenzene (40) which gives rise to the adducts (41) and (42) <83TL4245, 850M584>. 

Most of the work concerning the modification of carbene reactivity has been performed on cyclodextrins (CD) with reactive alkyl carbenes. Diazirines have proven to be the most convenient precursors due to the small size of the three-membered ring and the volatility of the leaving group, molecular nitrogen. Diazirines are usually obtained from the corresponding ketone in two steps in a methanolic solution of ammonia, hydroxylamine-0-sulfonic acid (HOSA) is added yielding a diaziridine which then is oxidized to the diazirine, most conveniently with iodine. 

Strict intermolecular diamination of alkenes remains a difficult process in transition-metal catalysis. Still, some interesting reactivity has recently been uncovered for terminal alkenes [122-124]. First, Shi reported the development of diamination of styrenes 18 and 179 under copper catalysis (Scheme 16.49). These protocols make use of three diaziridine derivatives 180-182, which were used as... 

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