Organic Letters
Letter
Chen, H.; Deng, G. Tetrahedron Lett. 2013, 54, 3838. (e) Gao, Q.; Wu,
X.; Jia, F.; Liu, M.; Zhu, Y.; Cai, Q.; Wu, A. J. Org. Chem. 2013, 78, 2792.
(f) Wang, J.; Zhang, X.; Chen, S.; Yu, X. Tetrahedron 2014, 70, 245.
(g) Feng, Q.; Song, Q. Adv. Synth. Catal. 2014, 356, 2445. (h) Park, S.;
Lee, K.; Kim, S. Bull. Korean Chem. Soc. 2014, 35, 1848.
(12) Dos Santos, A.; El Kaim, L.; Grimaud, L. Org. Biomol. Chem. 2013,
11, 3282.
(13) (a) Nguyen, T. B.; Ermolenko, L.; Al-Mourabit, A. Org. Lett. 2013,
15, 4218. For related works, see: (b) Nguyen, T. B.; Ermolenko, L.;
Retailleau, P.; Al-Mourabit, A. Angew. Chem., Int. Ed. 2014, 53, 13808.
(c) Tong, Y.; Pan, Q.; Jiang, Z.; Miao, D.; Shi, X.; Han, S. Tetrahedron
Lett. 2014, 55, 5499. (d) Guntreddi, T.; Vanjari, R.; Singh, K. N. Org.
Lett. 2015, 17, 976.
hydrochloride could accelerate the tautomerization of acetophe-
none, thus facilitating the D → E step.
In summary, we have developed a three-component redox
condensation of a variety of o-nitrohalobenzenes and acetophe-
none with elemental sulfur, enabling a direct, inexpensive, and
easy synthesis of 2-benzoylbenzothiazoles. The choice of base is
of vital importance to the success of the transformation, and N-
methylmorpholine was found to be particularly suitable for this
role. Elemental sulfur was found to play dual roles as nucleophilic
building block and redox moderating agent to fulfill electronic
requirement of the global process. The process involves the
formation of three new bonds (two C−S and one CN) in a
highly efficient and atom-, step-, and redox-economical manner
without addition of oxidizing or reducing agents or coupling
catalyst.
(14) At the time of manuscript preparation, 2-chloro-5-fluoronitro-
benzene and 2,5-difluoronitrobenzene were commercially available
from Sigma-Aldrich for $87.40/25 g (196622-5G) and $56.70/25 g
(368709-5G), respectively.
1
(15) Only three H NMR singlet signals which correspond to one
ASSOCIATED CONTENT
* Supporting Information
■
methyl signal of the product 3ab and two methyl signals of the starting
ketone 2b were observed between 2.0 and 2.8 ppm. If other products
derived from 2b were formed, other singlet signals should be observed in
this zone.
(16) For the single example of related bis(DABCO)disulfide
dichloride salt, see: (a) Konstantinova, L. S.; Rakitin, O. A.; Rees, C.
W.; Amelichev, S. A. Mendeleev Commun. 2004, 14, 9. (b) Konstantinova,
L. S.; Amelichev, S. A.; Rakitin, O. A. Russ. Chem. Bull. 2006, 55, 2081.
(c) Konstantinova, L. S.; Lysov, K. A.; Souvorova, L. I.; Rakitin, O. A.
Beilstein J. Org. Chem. 2013, 9, 577. This compound was found to be
unstable and readily hydrolyzed to yield elemental sulfur, DABCO
hydrochloride, and other sulfur compounds with positive oxidation
states of sulfur.
S
Experimental procedure, characterization data, and NMR
spectra. The Supporting Information is available free of charge
AUTHOR INFORMATION
Corresponding Authors
■
Notes
The authors declare no competing financial interest.
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