Transition Metal‐Catalyzed Synthesis of 3‐Coumaranone‐Containing NH‐Aziridines from 2 H ‐Azirines: Nickel(II) versus Gold(I)

A catalytic nucleophilic addition reaction of 3‐hydroxybenzofuran‐2‐carboxylic acid derivatives to 2H‐azirines for the high‐yield synthesis of NH‐aziridines with a 3‐coumaranone substituent has been developed. The Ph₃PAuNTf₂‐catalyzed reaction is diastereoselective to give predominantly (RS,SR)‐isomer of aziridine in good yield. The Ni(hfacac)₂‐catalyzed reaction affords aziridines in up to 98% yield and low or moderate diastereoselectivity, which in some cases is opposite to that observed for the gold(I)‐catalyzed reaction. The Ph₃PAuNTf₂ works well for sterically hindered azirines as well as benzofurans bearing electron‐withdrawing groups, whereas Ni(hfacac)₂ is the catalyst of choice for the preparation of aziridines having diazoacetyl substituent. The latter compounds can serve as substrates for the synthesis of fused aziridines via Buchner ring expansion reaction.

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