2‐Methylene‐2H‐azirines by Photolysis of 1‐Azidoallenes

New Way to Methylene‐2H‐azirines and Their Use as Powerful Intermediates for the Stereo‐ and Regioselective Synthesis of Compounds with Vinylamine Substructure

“…The formation of 23 and 24 can be rationalized by the well-known photochemical fragmentation of methylene-2H-azirines. [7] Scheme 4.…”

“…[8] However, the only known example of such reactions (49 Ǟ 50) [7] afforded exclusively a normal 2H-azirine as product of simple 1,4-addition.…”

“…[7,8] Thereby, the difficult access to considerable amounts of these first heterocyclic triafulvenes was attributed to their thermal and photochemical sensitivity as well as the difficult handling of the allenyl azides which served as precursors. Fortunately, we recently developed a new synthetic strategy that allows us to isolate some relatively stable allenyl azides.…”

First Propargyl Azides Bearing Strong Acceptor Substituents and Their Effective Conversion into Allenyl Azides: Influence of the Electronic Effects of Substituents on the Reactivity of Propargyl Azides

“…[19,20] Moreover, we wanted to perform a rational comparison between the reactivity of the propargyl azides bearing acceptor substituents with the reactivity of those propargyl azides connected with electron-donating groups. Finally, we assume that a convenient access to allenyl azides will open the door to long-sought [14][15][16] methylene-2H-azirines which were unknown [21][22][23] until recently when they were generated by photolysis of allenyl azides [24,25] or other azides. [26] Results and Discussion…”

Small Rings by Azide Chemistry

“…33 relatively stable 2 H -azirine 17 was obtained by the interception of the methyleneazirine 16 (R 1 = CH 2 OMe) by HCN (Scheme 6.8 ). 33 The photolysis of the halo substituted vinyl azides 18 produced the azirines 19 ; these were then thermally isomerized to the more stable 2 H -azirines 20 (Scheme 6.9 ). 36 This type of isomerization has also been observed with fl uoro substituted azirines.…”