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Divergent Access to Imidazopyrazinones and Imidazodiazepinones by Regioswitchable Post‐Ugi Heteroannulation
Author(s) -
Wu Danjun,
Zhang Xueling,
Li Yi,
Ying Sanjun,
Zhu Lixi,
Li Zhenghua,
Yang Gensheng,
Van der Eycken Erik V.
Publication year - 2019
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.201901511
Subject(s) - chemistry , umpolung , intramolecular force , bicyclic molecule , pyrazine , combinatorial chemistry , stereochemistry , divergent synthesis , ugi reaction , selectivity , intramolecular reaction , isocyanide , organic chemistry , catalysis , nucleophile
A metal‐free expeditious strategy for the divergent synthesis of structurally diverse bicyclic imidazo[1,5‐ a ]pyrazine and imidazo[1,5‐ a ][1,4]diazepine scaffolds is disclosed by combining an Ugi four‐component reaction of easily available building blocks and an exo/endo selectivity‐switchable post‐Ugi intramolecular heterocyclization. Using PPh 3 , the intramolecular umpolung aza ‐Michael addition is mediated to selectively generate imidazopyrazinones through a 6‐ exo ‐ dig cyclization, while without PPh 3 fused imidazodiazepinones are obtained through a thermal 7‐ endo ‐ dig cyclization in moderate yields.