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Electrophile‐Induced Cyclization of 3‐Alkynyl‐2‐arylquinoxalines: A Method for Benzo‐ and Naphthophenazine Synthesis
Author(s) -
Gulevskaya Anna V.
Publication year - 2016
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.201600660
Subject(s) - chemistry , alkyne , sonogashira coupling , moiety , regioselectivity , substituent , electrophile , derivative (finance) , stereochemistry , dig , aryl , medicinal chemistry , organic chemistry , palladium , catalysis , alkyl , computer security , computer science , financial economics , economics
A facile synthesis of benzo[ a ]‐, naphtho[1,2‐ a ]‐ and naphtho[2,1‐ a ]phenazines by ICl‐promoted 6‐ endo ‐ dig cyclization of 3‐alkynyl‐2‐arylquinoxalines has been developed. The starting 3‐alkynyl‐2‐arylquinoxalines were synthesized from 2,3‐dichloroquinoxaline by two successive Sonogashira and Suzuki–Miyaura reactions. The method works well for 3‐alkynyl‐2‐arylquinoxalines bearing various functional groups at the alkyne moiety. The arrangement and nature of the substituent in the 2‐aryl fragment affect the regioselectivity of the cyclization. For the substrate of one particular type, namely 2‐(4‐methoxyphenyl)‐3‐( p ‐tolylethynyl)quinoxaline, the treatment with ICl leads to the alternative 5‐ endo ‐ dig cyclization followed by demethylation of the methoxy group to give a spirocyclohexadienone derivative.