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Abstract:
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The present work reports the synthesis of
2-ary1—3—oxo-3—pyrazolino[3,4-b]quinoxalines for the first
time. These compounds have been prepared by the reaction
of ethyl 2-chloroquinoxaline—3—carboxylate with different
phenylhydrazines. 2-Aryl—3-oxo—3—pyrazolino[3,4—b]quinoxalines
are generally light yellow in either neutral or acid solutions
but changed the colour to deep violet or green in
basic media. The change in colour appears to be sharp and
therefore these compounds may be used as acid base indicators.
Their UV absorption maxima under acidic and basic media
are also very different. However, the actual conditions
under which these compounds may be used as indicators have
not been worked out. The synthesis and reactions of a new heterocyclic
system, lH—l,5—benzodiazepino[2,3—b]quinoxaline is also
reported here. This novel nitrogen heterocycke was prepared
by the condensation of ethyl 2-chloroquinoxaline-3—carboxylate
with o-phenylene diamine and subsequent manipulationsa to
give the parent compound. Several derivatives which are
expected tx> have valuable biological properties have also
beenlreported. The structures of all new compounds have been
established by elemental analysis and also by analysing
their spectral data smch as ultraviolet, infrared, nuclear
magnetic resonance and mass spectrometry. Compounds obtained
from this work will be submitted for screening their biological
properties. |