Formation of Aziridines

Bicker and Fischer incubated ephedrine isomer 127 with a rat liver homogenate to which ATP and sulfate were added [191]. Formation of aziridine 128, requiring... 

Figure 11.22 Biochemical formation of aziridines in rat liver homogenate.

Formation of aziridine by direct reaction of phenylnitrene with 3-methyl-1-butene... 

Diazoesters 22 have an electronically unique a-carbon atom. (Scheme 9) They are commonly used for the formation of aziridines 23 from imines 24. The intermediate (25) resulting from the addition of a-diazoesters 22 to the latter (24) can undergo elimination of the proton at the a-position prior to extrusion of molecular nitrogen. This interrupted aza-Darzens reaction allows for the direct alkylation of diazoesters 22 via cleavage of a carbon-hydrogen bond. 

There are a few reports on the use of oximes as electrophilic amination reagents. Since 1984, ketone O-sulfonyloxknes have found applicability as amino transfer reagents to car-banions. In the reaction of organometaUic compounds with oximes, carbanions attack the carbonyl carbon of the oxime, giving Af-substituted hydroxylamines as addition products (Scheme 53, path a). However, a number of scattered reports have been also published on the formation of aziridines by a-deprotonation, followed by addition (path b) or formation of azirines by a-deprotonation before addition (path c). Addition of carbanions to azirines also yields aziridines, which are hydrolyzed to a-aminoalcohols. 

Formation of Aziridines (Addition of Nitrogen, Nitrogen) epr-Arylimino-addition, etc... 

Simple carbon-carbon double bonds react slowly with azides and frequently take more than a week to react at 25 C. Increasing the reaction temperature is restricted by the thermal lability of most triazolines. In fact, some classes of triazolines decompose spontaneously at room temperature with the extrusion of nitrogen.189 The principal decomposition modes involve the formation of aziridines and imines and are outlined in Scheme 55. Usually, just a few of these modes operate in any particular system.190... 

When electron-withdrawing groups are present on the 4-carbon, triazoline thermolysis is insensitive to solvent polarity a homolytic decomposition to a singlet diradical similar to that formed in photolysis is proposed to account for the selective formation of aziridine in these cases (Scheme 162).67,172,454 The lower thermolysis temperatures of N-aryltriazolines ( 25°C)6 7,322 as compared to those for the N-alkyl compounds ( 90° C)6 7 are consistent with the stabilization of the diradical by aryl groups. 

The nitrene transfer from PhI=NTos to alkenes catalyzed by the CpFe(CO)2+ fragment gave better results (85% for styrene) [25], but the characteristics of the chemistry of the cationic intermediates as postulated by the reaction mechanism are closely connected to the alternative formation of aziridines by a carbene transfer... 

Synthesis of annelated diazepines based on unsaturated aromatic diazepines may involve the preliminary transformation of ketones into the corresponding l,3-diaryl-2,3-dibromopropane-3-ones (chalcone dibromides). The interaction between o-PDA or some of its substituted analogues with chalcone dibromides leads to the formation of aziridine derivatives [64] (see Chap. 1). However, in the case of 4-nitro-o-PDA, either azirenoquinoxalynes 53 or benzodiazepine derivatives 54 may be obtained depending on the reaction conditions [65] (Scheme 4.15). Diazepine derivatives 56 are obtained by the condensation of chalcone dibromides 51 with 5,6-diamino-1,3-dimethyluracil 55 [66], but aziridine derivatives are not isolated in this reaction. It should be noted that compounds 54 and 56 are formed owing to cyclization of the intermediate (3-enaminoketones [65, 66, 67] and are easily isolated from the reaction mixture. 

The formation of aziridines using bromamine-T was catalysed by cobalt porphyrins.77 Yields range from the mid-50% level to >90% with aliphatic and aromatic alkenes. Sulfonimidamide also yielded aziridines when treated with iodosylbenzene diacetate in the presence of dirhodium tetraacetate.78... 

Diazoacetates are commonly used for the formation of aziridines from imines under Lewis or Bronsted acidic conditions - a process known as the aza-Darzens reaction. A useful twist on the reaction is achieved if the 1,2-addition intermediate undergoes deprotonation of the a proton prior to intramolecular aziridine formation with N2 extrusion. Such an interrupted aza-Darzens reaction accomplishes a... 

Among these, a variety of oxygen atom transfer reactions have been described [la,b] and highly stereoselective reactions have been reported [2]. Although the formation of aziridines by the reaction of nitrenes with olefins is well known, the efficiency is moderate, because of the competition between hydrogen abstraction and insertion processes [3]. A typical example is shown (Eq. 2) [3d]. 

Oxidation of methoxylamine and some other O-substituted hydroxylamines by lead tetraacetate in the presence of alkenes can also lead to the formation of aziridines. The oxidation of 2,4-dinitrobenzenesul-fenamide is analogous.In view of the results reported widi aminolactams, these reactions do not necessarily establish the intomediacy of nitrenes in the oxidations. 

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