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Efficient Use of 1,2‐Dihaloazine Synthons in Transition‐Metal‐Free Preparation of Diverse Heterocycle‐Fused 1,4‐Oxazepines
Author(s) -
Sapegin Alexander V.,
Kalinin Stanislav A.,
Smirnov Alexey V.,
Dorogov Mikhail V.,
Krasavin Mikhail
Publication year - 2015
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.201403397
Subject(s) - synthon , chemistry , intramolecular force , pyridine , electrophile , transition metal , combinatorial chemistry , ring (chemistry) , thio , intermolecular force , stereochemistry , medicinal chemistry , substitution reaction , organic chemistry , molecule , catalysis
A previously reported condensation reaction of ambiphilic 2‐(1 H ‐pyrazol‐5‐yl)phenols with various o ‐chloro‐substituted nitroaromatic synthons to provide medicinally important tetracyclic pyrazolo[1,5‐ d ][1,4]oxazepines was extended to more readily available and convenient‐to‐use 1,2‐dihaloazines. Although 4,5‐dichloropyridazin‐3(2 H )‐ones and 2,3‐dichloropyrazine are popular bis(electrophilic) partners in various S N Ar‐type condensations and also were efficiently used in the reaction reported herein, the facility with which various 3‐bromo‐2‐chloropyridines underwent the same cyclization was unexpected. These reactions are presumed to occur as sequential intermolecular S N Ar/Smiles rearrangement/intramolecular S N Ar tandem reactions and provide a rare example of the transition‐metal‐free substitution of a bromine atom at the 3‐position of a pyridine ring.