10.1002/adsc.201901161
Advanced Synthesis & Catalysis
Solvent was removed, and the residue was separated
by column chromatography to give a pure sample by
using mixed petroleum ether/ethyl acetate 8:1 (v/v) as
an eluent to afford the desired product 3a. The
remaining substituted imidazoles were prepared in a
similar manner.
References
Scheme 3. Reactions carried out as control experiments.
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iodinated with iodine to give 2-iodocyclohexanone A
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by leaving of I along with a catalytic cycle of I
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In conclusion, we have developed a simple and
direct protocol to synthesize 1,2-diphenyl-1Hbenzo[d]
imidazoles from amidines and cyclohexanones under
metal-free conditions. Iodine can be used to smoothly
mediate such a transformation without the need for a
transition-metal catalyst. 1,1,2,2-Tetrachloroethane as
solvent also plays an important role in affording high
yield using this protocol. This method provides an
efficient route for the synthesis of substituted 1,2-
diphenyl-1H-benzo[d] imidazoles using non-aromatic
cyclohexanones as the aryl source in the presence of
I2, which used as a green catalyst. Currently, the
application of this protocol in the synthesis of other
products is under investigation in our laboratory.
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Experimental Section
A mixture of 1a N-phenylbenzimidamide (0.1 mmol),
cyclohexanone 2a (0.2 mmol), I2 (50 mol%), 1,1,2,2-
tetrachloroethane (1 mL) was placed into a test tube
equipped with a magnetic stirring bar. The resulting
mixture was stirred at 140 °C under O2 (balloon) for 24 h.
4
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