Azirines ring opening with nucleophiles

The conversion of epoxides to aziridines by nucleophilic ring-opening with azide ion or amines followed by cyclization was covered in Section 1.01.9.3. The conversion of azirines to aziridines by nucleophilic addition and the conversion of aziridines to azirines by elimination were covered in Sections 1.01.6 and 1.01.7, respectively. 

The reaction of 2-phenyl-l-azirine (201) with benzoic acid gaveN-benzoylphenacylamine (204) (67BCJ2938). The overall mechanism of the reaction involves initial protonation on nitrogen followed by addition of the nucleophile to the azirinium ion and finally ring opening. 

This chapter reviews the chemical literature of monocyclic aziridines and 2//-azirines from 1995 through 2007. It reveals that aziridines are well-behaved carbon electrophiles capable of reacting with various nucleophiles. The ability of aziridines to undergo regioselective ring-opening reactions contributes largely to their synthetic value. 

The foregoing reaction is probably initiated by nucleophilic addition of the iY-imines to the 2H-azirines to form 36 which may undergo homo-1,5-dipolar cyclization or ring opening followed by cyclization of 1,6-dipoles 37. This novel heterocyclic system was first prepared by the reaction of pyridine N-imines with a-chlorocinnamates, in which azirine intermediates were postulated.164 As a variation, use of azirine intermediates generated in situ from acetophenone oxime O-tosylate or dimethylhydrazone methiodide under the Neber reaction conditions also produces the pyrido[l,2-/>]triazines... 

Photo-triggered ring opening of 2//-azirines is a well-known reaction to produce pyrrolines [8, 71]. Padwa and co-workers showed that photoirradiation of azirines with a mercury arc lamp (450 W) equipped with Vycor filter generated the reactive nitrile ylide intermediate (72), which can be stabilized by the phenyl substituents. The nitrile ylide (72) then reacts with the electron-deficient olefins (73) such as acrylate and acrylonitrile in a cycloaddition reaction to form A -pyrrolines (74) (Scheme 10) [8]. Steenken and co-workers studied reaction kinetics of azirines with dipolarophiles as well as nucleophiles such as alcohols [72]. They showed that the reaction rate depends on the azirine substituents, the nucleophilicity of the reactant and the acidity of the alcohol. 

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