10.1002/adsc.201900093
Advanced Synthesis & Catalysis
Acknowledgements
delivered compound C, which was detected by GC-
MS. RhodiumII was released to complete the catalytic
cycle. 3-Methyl-1-phenyl-1H-pyrazol-5-amine (1a)
This work was supported by the National Natural Science
Foundation of China (No. 21772001, 21702003), Natural Science
Foundation of Anhui Province (No. 1808085QB31,
1808085MB41) and the Start-up Research Fund of Anhui Normal
University.
underwent
a
subsequent
Friedel-Crafts-type
nucleophilic addition to C to generate D, which then
underwent an intramolecular condensation to give E.
The title product (3a) was obtained by an oxidation
pathway driven by aromatization.
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Scheme 4. Proposed Mechanism.
In conclusion, we have developed a novel and
practical method for the synthesis of fused
pyrazolo[3,4-b]pyridine
derivatives
via
an
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Pyrazolo[3,4-b]pyridines 3
A mixture of 5-amino pyrazole 1 (0.1 mmol), cyclic
2-diazo-1,3-diketone 2 (0.2 mmol) and Rh2(OAc)4
(0.002 mmol) in DMF (1 mL) was heated to 110 °C
in an oil bath. After the reaction was complete (as
determined using TLC), the reaction mixture was
cooled to room temperature and quenched with H2O,
and the mixture was then extracted with ethyl acetate
(3 × 10 mL). The organic layers were combined and
dried over Na2SO4. After removal of the solvent
under vacuum, the residue was purified using flash
column chromatography (ethyl acetate : petroleum
ether = 1:10, v/v) to give desired product
4
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