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Organic & Biomolecular Chemistry
Page 6 of 7
ARTICLE
Journal Name
molecules in Table S1 which can be synthesized in multiple steps
from the obtained THQs.
W. Li, Asian J. Org. Chem. 2019, 8, 2105-2108.
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Experimental Section
General procedure for transfer hydrogenation reaction: In a
pyrex tube (15 mL), substituted quinoline (0.5 mmol), Hantzsch
ester (2.5 equiv.), B(OH)3 (15 mol%) and solvent (2 mL) was
charged. The reaction tube was closed without the exclusion of
o
air and placed in a preheated oil bath (60 C) with continuous
stirring. The reaction was monitored by thin layered
chromatography (TLC) in n-hexane and ethyl acetate solvent
system. After completion of the reaction, the crude compound
was purified by column chromatography on silica gel for the
pure compound.
Conclusions
5
In summary, the catalytic reduction of quinolines with boric acid
and Hantzsch ester is reported. The present protocol works
under mild reaction conditions with excellent yield and good
chemoselectivity. The mechanistic studies demonstrate that
transformation proceeds through a stepwise 1,4/1,2-hydride
addition to the quinoline moiety, activated by metal-free air
stable boron-based Lewis acid. The synthetic utility of the
1,2,3,4-tetrahydroquinoline derivatives is demonstrated by the
synthesis of several bio-active molecules, including
antiarrhythmic drug nicainoprol. Overall, this approach is
promising especially from industrial perspective because it’s an
operationally simple, highly efficient, environment-friendly,
scalable, economical, and abundant boric acid used as the
catalyst.
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Conflicts of interest
There are no conflicts to declare.
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Acknowledgements
A.D gratefully acknowledges the SERB, DST (ECR/2016/001459)
and DST-INSPIRE (IFA-14-CH-135) for the financial support. We
would like to thank the Department of Chemistry, and Central
Instrumentation Facility, IITG for mass (FIST) and COE FAST for
NMR (F. No. 22-3/2016-TS-II/TC) analysis and start up grant.
D.B., S.N., P.A., B.S., and M.K. would also like to thank IITG for
their research fellowship.
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6 | J. Name., 2012, 00, 1-3
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