Aziridines reaction with ammonia

The reaction of 2 -benzyloxychalcone dibromides (605) with ammonia gives a chalcone aziridine (606). Following conversion to the (V-benzoyl derivative, acid hydrolysis removed the protecting group at C-2 and a 3-aminoflavanone results (Scheme 230) (73ACH(76>95). 

Calculations at the MP2(Full)/6-31++G(d,p)//MP2(Full)/6-31+G(d) level of theory were used to investigate the SN reactions between ammonia and aziridine, aze-tidine, methylethylamine, and four fluorinated derivatives of aziridine.52 The results show that aziridine and azetidine have strain energies of 27.3 and 25.2 kcalmol-1, respectively, and that as a consequence they react 7.76 x 1023 and 2.30 x 1017 times faster with ammonia than does the methylene group of methylethylamine. However, even after subtracting the effect due to the release of ring strain, aziridine still reacts much faster than the other two substrates. This is because the electrostatic attraction of the charges in the product-like dipolar transition state are much greater for aziridine. 

An interesting example of heterocyclization involving both the aziridine fragment and the carbonyl group is a reaction of aziridinyl ketones with ammonia and carbonyl compounds, giving rise to 3,5a-dihydro-l//-azireno[l,2-c]imidazoles. This reaction will be considered in more detail in Sects. 1.2 and 1.3. 

One of the initial findings about bicyclic aziridines is reported in [88] the authors carried out the synthesis of 3,5a-dihydro-l//-azireno[l,2-c]imidazoles by reacting trwith carbonyl compounds in methanol saturated with ammonia in the presence of ammonium bromide. In particular, 2,2-dimethyl-6-(4-nitrophenyl)-4-phenyl-l,3-diazabicyclo[3.1.0]hex-3-ene 72 was obtained in the reaction of ketone 70 with ammonia and acetone 71 (Scheme 1.19). 

The reaction of 3-tosyloxy or 3-mesyloxy flavones (e.g., 361) with ammonia or primary amines has been shown to yield the corresponding 3-amino flavones (e.g., 362) in high yields (Scheme 55). The results can be rationalized through a hetero-Michael addition of the ammonia or primary amine followed by cyclization to form the aziridine... 

Carboxylic acid dianions have also been alkylated by reaction with aziridines to give novel y-amino substituted acids in good yields508. Methoxybenzoic acids have also been alkylated in a reductive process by reaction with lithium in ammonia followed by treatment with an alkyl halide. The product formed in this one-pot reaction is an alkylated cyclohexa-2,5-diene carboxylic acid507. 

The reaction of a-bromo-a, -enones with ammonia or amines proved to be a more universal synthetic method, permitting a wide variation of substituents at the nitrogen atom of the aziridine ring (94IZV282). 

The reaction of 2-bromoallylamine with sodium amide in liquid ammonia forms a cyclic anion that reacts with trimethylchlorosilane to provide 1-trimethylsily 1-2-methylene aziridine.131... 

A A -Disulfonamides are decomposed with sodium hydrogencaibonate in DMSO to give ketones. Imines formed from the reaction of primary amines with carbonyl compounds can be oxidized to ox-aziridines with MCPBA which hydrolyze to aldehydes or ketones with acid. When acetone is used, the final by-products are ammonia and acetone (equation 37). The use of 2-pyridinecarbaldehyde is preferred since it gives an acid-soluble by-product which aids work-up (equation 38)." ... 

The conjugate addition reaction of x,/ -enc-3 -phenylselenone 11 with aqueous ammonia in dimethylformamide, aqueous methylamine in dimethylformamide or benzylamine in tetrahy-drofuran at room temperature smoothly gives 2, 3 -ribo-aziridine 12 (R2 = H) and its 2, 3 -(./V-substituted)-ribo-aziridine derivatives (R2 = CH3, Bn) in moderate yield105. 

Aziridines have been obtained from chloroallylamines by treatment with NaNH2 in liquid ammonia (Fig. 11). These reactions are highly dependent on the ratio amine-NaNH2 and in some cases the acetylenic amine becomes the major product (refs. 63, 64). 

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