Ring Expansions of Azirines and Azetines

Asymmetric Neber Reaction in the Synthesis of Chiral 2-(Tetrazol-5-yl)-2H-Azirines

“…Due to their unique structural features, 2H-azirines have been widely used as valuable synthetic intermediates in the synthesis of a plethora of nitrogen-containing compounds. [1][2][3][4][5][6][7] In fact, the high ring-strain along with the activated iminic bond and the Nlone pair on the azirine, make these heterocycles highly reactive and enable them to participate in organic reactions not only as nucleophiles and electrophiles, but also as dienophiles and dipolarophiles. Moreover, under the appropriate reaction conditions, highly reactive intermediates such as vinylnitrenes, nitrile ylides and iminocarbenes, can be generated from selective bond cleavage, broadening the reactivity of these small molecules.…”

“…The isolation of chiral naturally occurring 2H-azirines, such as azirinomycin (1), dysidazirine (2) and antazirine (3), with promising biological properties, has raised the interest in the development of efficient asymmetric synthetic methodologies towards chiral 2H-azirine-2-carboxylates and their analogues (Figure 1). [8][9] In fact, the synthesis of chiral 2H-azirine-2carboxylates using alkaloid-promoted Neber reactions 10 as well as asymmetric Neber reaction using bifunctional chiral thioureas as catalysts have been described.…”

Synthesis of New 2-Halo-2-(1H-tetrazol-5-yl)-2H-azirines via a Non-Classical Wittig Reaction

“…It is well established that some 2-halo-2 H -azirines undergo thermal rearrangement to their azirine isomers through a [1,2]-halogen shift [32,33]. Recently, Banert et al .…”

“…They can act as nucleophiles, electrophiles, dienophiles, and dipolarophiles in a variety of organic reactions. Furthermore, selective cleavage of each of the three bonds can be achieved, and this leads to highly reactive intermediates such as vinylnitrenes, nitrile ylides, and iminocarbenes [1,2,3,4,5,6].…”

Isomerization of 5-(2H-Azirin-2-yl)oxazoles: An Atom-Economic Approach to 4H-Pyrrolo[2,3-d]oxazoles

“…1 H-NMR spectra were calibrated according to the residual peak of CDCl 3 (7.26 Compound 2 was prepared following the slightly modified published procedure [27]. A portion of Rh 2 (oct) 4 (1 mol%) was added to a mixture of azirine 1 (1 mmol) and appropriate nitrile (50-200 mmol) in DCE (500 mL per 1 mmol. of azirine).…”