Ring-opening reaction of aziridines

The ring-opening reactions of aziridines 16 with amines deserve special attention. Unlike ring-openings with the other nucleophiles examined, they do not require added base, and they do not produce stoichiometric byproducts (as with azide). In certain cases, they do not even require a solvent, as exemplified by the ring-opening of aziridine 18 (Table 12.12, entries 1-3). In addition, the reactions... 

Reductive ring-opening reaction of aziridine ester constitutes a convenient access to amino acids a typical example is given in Scheme 27 [37]. 

Typically in ring-opening reactions of aziridines, the amine functional group is retained in the product molecule. An example of such a reaction where the amine group has been lost has recently been reported <06TL977>. An intramolecular Friedel-Craft reaction of aziridine 91 leads to the expected product as an intermediate. Under the rather drastic reaction conditions, the sulfonamide is lost leading to formation of the naphthalene ring. 

Scheme 9 Ring-Opening Reaction of Aziridines with Cysteines Yielding Lanthionines1301...

Most of the ring-opening reactions of aziridines may be formulated -.as nucleophilic substitution reactions, in which one of the oarbon- nitrogen bonds is broken and a new bond with carbon is formed. In this section, ring-opening reactions are classified ou the basis of the element which is joined to the carbon atom in the newly formed bond of the reaction product. ... 

Finally, the substituent effects on the geometry of the -substituted aziridine ring, the -inversion energy barriers, and the ring opening reactions of aziridines by cyanide ion53 have been discussed... 

Compound 46 and benzaldehyde are considered to be most likely formed by the ring-opening reaction of aziridine 44, giving an azomethine ylide, followed by hydrolysis. Thermolysis of 32 also affords 44-46, and benzaldehyde in 79%, 100%, 15%, and 16% NMR yield, respectively. This is the first example of aziridine formation from heterocyclobutanes with high coordinate main-group elements. 

Sun X, Ye S, Wu J (2006) A-Heterocyclic carbene an efficient catalyst for the ring-opening reaction of aziridine with acid anhydride. Eur J Org Chem 2006(21 ) 4787 1790... 

Nitrogen-based nucleophiles continue to remain popular in ring-opening reactions of aziridines. a-Substituted-a-methoxycarbonyl-V-nosylaziridines were opened with a variety of functionalized amines to provide access to enantiopure a,a -disubstituted (3-lactam scaffolds for ditopic peptidomimetics <07OL101>. A related intramolecular regioselective 3,Y-aziridine ring opening with an a-amino functionality was reported in the synthesis of... 

Sometimes, especially when fluoride sails are used as the reagents for the ring opening of aziridines, the substrate can be activated by quaternization to the corresponding A/.A-dialkyl-aziridinium compound, which reacts more readily with the fluoride anion than the aziridine itself. Thus, the tV.A -diallylaziridinium mesylate salts 23 have been employed in ring opening reactions of aziridine derivatives of pyranosides. " " ... 

The ring-opening reaction of aziridines with external or internal nucleophiles was easily accomplished and proceeds with inversion of configuration, e.g., 1251. 

Table 7 Ring-opening reactions of aziridines with haiogen...

Diamines are another highly useful class of molecules with potent biological activity and use as synthetic intermediates and metal ligands. The ring-opening reactions of aziridines with amines and azide provides a facile route for the synthesis of 1,2-diamines. 

Ring-opening reactions of aziridines (and epoxides) typically require the use of a Lewis acid to catalyze the reaction. P-Cyclodextrins (Ji-CD) are very useful in creating microenvironments in which aziridines can be opened using mild conditions. The reaction of aziridines with (3-CD and sulfur nucleophiles such as thiocyanate <05SL489> or thiophenols <05TL6437> provides a mild route to such ring-opened compounds. 

Ring-opening reactions of aziridines with nucleophiles proceed in a similar manner, but are slower than those of their aziridinium counterparts (Montgomery et al. 1970). 

Carbon-based nucleophiles continue to be examined in ring-opening reactions of aziridines. Select examples from the year 2014 include employment of indole derivatives in Friedel-Crafts-type reactions (14T4512, 14MI16478), utilization of malonate-type nucleophiles (14JA9190, 14EJ0767), and arylation reactions involving the use of N-heterocyclic... 

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