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Pyrazoles and C ‐Imidoylaziridines through [4+1] Annulation and [2+1] Cycloaddition of 1‐Azabuta‐1,3‐dienes with a Synthetic Equivalent of Phthalimidonitrene
Author(s) -
Stukalov Aleksandr,
Sokolov Viktor V.,
Suslonov Vitalii V.,
Kuznetsov Mikhail A.
Publication year - 2017
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201700172
Subject(s) - chemistry , annulation , imine , cycloaddition , aromatization , lone pair , medicinal chemistry , nitrogen atom , pyrazoline , stereochemistry , photochemistry , organic chemistry , molecule , catalysis , ring (chemistry)
Oxidative addition of N ‐aminophthalimide to 1,2,4‐triaryl‐1‐azabuta‐1,3‐dienes leads, in most cases, to the regiodefined formation of 1,3,5‐triarylpyrazoles in moderate to good yields through [4+1] annulation. This transformation is supposed to proceed by nitrenoid attack onto a lone pair of electrons of the imine nitrogen atom to give the vinylazomethine imine, followed by its 1,5‐electrocyclization into pyrazoline and further aromatization into pyrazole. Rare examples of 2‐imidoyl‐1‐phthalimidoaziridines that are formed by competitive [2+1] cycloaddition onto the C=C bond were isolated in low yields for 1‐azadienes with electron‐deficient aryl substituents at the imine nitrogen atom.