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Synthesis of pyrrolo[1,2‐ a ]quinoxalines by 1,3‐dipolar cycloaddition reaction. An additional reaction mechanism via an aziridine intermediate
Author(s) -
Kim Ho Sik,
Kurasawa Yoshihisa,
Yoshii Chiemi,
Masuyama Minako,
Takada Atsushi,
Okamoto Yoshihisa
Publication year - 1990
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570270457
Subject(s) - quinoxaline , chemistry , cycloaddition , aziridine , medicinal chemistry , 1,3 dipolar cycloaddition , stereochemistry , reaction mechanism , ring (chemistry) , organic chemistry , catalysis
The reaction of the 2‐substituted 6‐chloroquinoxaline 4‐oxides 1a or 1b with 2‐fold molar amount of methyl propiolate resulted in the 1,3‐dipolar cycloaddition reaction to give 8‐chloro‐1,3‐bismethoxycarbonyl‐4‐(piperidin‐1‐yl)pyrrolo[1,2‐ a ]quinoxaline 4a or 8‐chloro‐1,3‐bismethoxycarbonyl‐4‐(morpholin‐4‐yl)pyrrolo‐[1,2‐ a ]quinoxaline 4b , respectively. Compound 4a or 4b was transformed into 8‐chloro‐3‐methoxycarbonyl‐4‐(piperidin‐1‐yl)pyrrolo[1,2‐ a ]quinoxaline 5a or 8‐chloro‐3‐methoxycarbonyl‐4‐(morpholin‐4‐yl)pyrrolo[1,2‐ a ]‐quinoxaline 5b , respectively. The structure of 4a,b was confirmed by the NOE measurement among the C 1 ‐H , C 2 ‐H and C 9 ‐H proton signals of 5a,b . An additional reaction mechanism was proposed for the ring transformation of isoxazolo[2,3‐ a ]quinoxalines into pyrrolo[1,2‐ a ]quinoxalines.