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Oxidative Ring‐Opening of 1 H ‐Pyrazol‐5‐amines and Its Application in Constructing Pyrazolo–Pyrrolo–Pyrazine Scaffolds by Domino Cyclization
Author(s) -
Pan Lei,
Jin Feng,
Fu Rui,
Gao Ke,
Zhou Shaofang,
Bao Xiaoguang
Publication year - 2020
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.202000265
Subject(s) - chemistry , pyrazine , domino , moiety , ring (chemistry) , deprotonation , pyrrole , hydroxylamine , medicinal chemistry , cascade reaction , nucleophile , nucleophilic addition , combinatorial chemistry , stereochemistry , organic chemistry , catalysis , ion
Herein, an oxidative ring‐opening of 1 H ‐pyrazol‐5‐amines to form 3‐diazenylacrylonitrile derivatives under mild and transition‐metal‐free conditions is described. In addition, the nucleophilic addition of deprotonated 1 H ‐pyrrole‐2‐carbaldehydes to the vinyl moiety of the yielded 3‐diazenylacrylonitriles could trigger domino cyclization to afford the 3 H ‐pyrazolo[3,4‐ e ]pyrrolo[1,2‐ a ]pyrazine derivatives. Computational studies suggest that the oxidation of 1 H ‐pyrazol‐5‐amines in the presence of PhIO is through the formation of a hydroxylamine intermediate followed by elimination of H 2 O to result in the ring‐opening product. The detailed domino cyclization pathway leading to the pyrazolo–pyrrolo–pyrazine scaffolds is revealed.