10.1002/adsc.201901617
Advanced Synthesis & Catalysis
A solution of 1.0 mmol of α-keto acid 1, 0.5 mmol of 2-
aminothiophenol 2 and 3.0 equiv. of H2O2 in 2 mL1,4-
dioxane/H2O (v/v = 4:1) were taken in a 4 mL glass vial with
solid top cap. The resultant mixture was kept stirred under
Aldrich® Micro Photochemical Reactor, blue LED lights
Conclusion
In conclusion, we have developed for the first time the having λ = 435-445 nm at room temperature for 8 h. After that
the reaction mixture was treated with ethyl acetate and three
times washed with brine solution. The ethyl acetate fraction
was collected and dried over anhydrous sodium sulfate and
was subjected to concentration under rota evaporator. The
obtained residue was column chromatographed (hexane/ethyl
acetate) to afford benzothiazoles 3a-p.
metal-free and photocatalyst-free photooxidative version
of synthesis of benzothiazoles following the
decarboxylation strategy. α-Keto acids and 2-
aminothiophenols bearing different substituents at
different positions were found well accommodated in the
given reaction conditions and provided corresponding
benzothiazoles in moderate to good yields. Notably, the
synthesis of 2-unsubstituted benzothiazoles was also
achieved without any difficulty. The mechanistic course
of the reaction is clearly justified through control
experiments and UV-Vis studies according to which the
reaction proceeds via formation of an EDA complex
between α-keto acids and 2-aminothiophenols.
Acknowledgments
We gratefully acknowledge Department of Chemistry, IIT Roorkee for
allowing access to instrumental facilities. The authors A. M., S. B. and
R.K.S. thank MHRD for the award of fellowship. This work was
financially supported by Council of Scientific and Industrial Research
(CSIR) (Scheme No. 02(0372)/19/EMR-II).
Experimental Section
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1
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