Communication
[7] N. Giubellina, S. Mangelinckx, K. W. Törnroos, N. De Kimpe, J. Org. Chem.
2006, 71, 5881–5887.
Conclusions
[8] X.-T. Zhou, Y.-R. Lin, L.-X. Dai, J. Sun, L.-J. Xia, M.-H. Tang, J. Org. Chem.
In summary, we have developed a simple and rapid method for
the synthesis of N-sulfonyl ketimines, via direct condensation of
ketones and sulfonamides, assisted by MWI. Microwave-assisted
synthesis of imines from the commercially available ketones
and sulfonamides allows completing the transformation in one
hour, with minimal environmental impact, both in terms of en-
ergy and solvent use: no chlorinated solvents and no reflux
setup. The formation of N-sulfonyl ketimines reported here rep-
resents the first alternative to multistep procedures based on
the formation of N-sulfinyl imines, furnishing the products in
similar yields, with the additional advantages of using commer-
cially available reagents, a one-step procedure, lower energy
consumption and shorter reaction times.
1999, 64, 1331–1334.
[9] S. Kobayashi, Y. Mori, J. S. Fossey, M. M. Salter, Chem. Rev. 2011, 111,
2626–2704.
[10] C. Tan, X. Liu, L. Wang, J. Wang, X. Feng, Org. Lett. 2008, 10, 5305–5308.
[11] Z. Hou, J. Wang, X. Liu, X. Feng, Chem. Eur. J. 2008, 14, 4484–4486.
[12] S. Nakamura, M. Hayashi, Y. Hiramatsu, N. Shibata, Y. Funahashi, T. Toru,
J. Am. Chem. Soc. 2009, 131, 18240–18241.
[13] Q. Yang, G. Shang, W. Gao, J. Deng, X. Zhang, Angew. Chem. Int. Ed. 2006,
45, 3832–3835; Angew. Chem. 2006, 118, 3916.
[14] S. H. Kwak, S. A. Lee, K.-I. Lee, Tetrahedron: Asymmetry 2010, 21, 800–
804.
[15] M. A. Zolfigol, M. Tavasoli, A. R. Moosavi-Zare, P. Arghavani-Hadi, A. Zare,
V. Khakyzadeh, RSC Adv. 2013, 3, 7692–7696, and references 10–22
therein.
[16] Non-enolizable ketimines, such as diaryl ketimines, can be synthesized
in good yields, see: R. N. Ram, A. A. Khan, Synth. Commun. 2001, 31,
841–846.
[17] D. L. Boger, W. L. Corbett, T. T. Curran, A. M. Kasper, J. Am. Chem. Soc.
1991, 113, 1713–1729.
[18] G. D. Artman III, A. Bartolozzi, R. W. Franck, S. M. Weinreb, Synlett 2001,
232–233.
Experimental Section
Procedure for the Synthesis of N-Sulfonyl Imines: A 10 mL micro-
wave vial equipped with a stirrer was charged with the ketone
(1 mmol), the sulfonamide (1.2 mmol), dry toluene (0.5 mL) and
Ti(OEt)4 (1 mmol). The vial was closed and heated at 150 °C for 1 h
using microwave irradiation. After completion, it was let to cool
down to room temperature, diluted with 5 mL of AcOEt, quenched
with 1 mL of NaHCO3, and filtered through a pad of celite. The
solvent was evaporated in vacuo and the crude was analysed by 1H
NMR spectroscopy. Conversion was estimated by comparing the
integration of signals corresponding to the product and to the unre-
acted ketone. In the case of volatile ketones the comparison was
done against the remaining p-toluenesulfonamide. The crude prod-
uct was purified by flash chromatography on silica gel using mix-
tures of n-pentane and AcOEt as the eluent.
[19] D. L. Boger, W. L. Corbett, J. Org. Chem. 1992, 57, 4777–4780.
[20] J. L. García Ruano, J. Alemán, M. Belén Cid, A. Parra, Org. Lett. 2005, 7,
179–182.
[21] J. L. García Ruano, J. Alemán, M. Belén Cid, A. Parra, Org. Synth. 2007,
84, 129–138.
[22] R. Shintani, M. Takeda, Y.-T. Soh, T. Ito, T. Hayashi, Org. Lett. 2011, 13,
2977–2979.
[23] R. Shintani, M. Takeda, T. Tsuji, T. Hayashi, J. Am. Chem. Soc. 2010, 132,
13168–13169.
[24] A. A. Mikhailine, M. I. Maishan, R. H. Morris, Org. Lett. 2012, 14, 4638–
4641.
[25] J. P. Wolfe, J. E. Ney, Org. Lett. 2003, 5, 4607–4610.
[26] Y. Sugihara, S. Iimura, J. Nakayama, Chem. Commun. 2002, 134–135.
[27] L.-Y. Fan, F.-F. Gao, W.-H. Jiang, M.-Z. Deng, C.-T. Qian, Org. Biomol. Chem.
2008, 6, 2133–2137.
[28] There is an unoptimized procedure without reported yields [1.5 equiv.
of Ts-NH2, and 1.5 equiv. of Ti(OiPr) at toluene reflux for 12 h, together
with catalytic ZnCl2] X. Huang, J. Huang, Y. Wen, X. Feng, Adv. Synth.
Catal. 2006, 348, 2579–2584.
[29] J. F. Collados, E. Toledano, D. Guijarro, M. Yus, J. Org. Chem. 2012, 77,
5744–5750.
[30] J. Qin, L. Huang, Y. Cao, Z. Sun, RSC Adv. 2015, 5, 7291–7296.
[31] A. Vass, J. Dudás, R. S. Varma, Tetrahedron Lett. 1999, 40, 4951–4954.
[32] T. Jin, G. Feng, M. Yang, T. Li, Synth. Commun. 2004, 34, 1277–1283.
[33] R. W. Layer, Chem. Rev. 1963, 63, 489–510.
[34] A. Zare, A. R. Moosavi-Zare, A. Hasaninejad, A. Parhami, A. Khalafi-Nez-
had, M. H. Beyzavi, Synth. Commun. 2009, 39, 3156–3165.
[35] A. Khalafi-Nezhad, A. Parhami, A. Zare, A. N. Shirazi, A. R. Moosavi Zare,
A. Hassaninejad, Can. J. Chem. 2008, 86, 456–461.
[36] R. Matsubara, F. Berthiol, S. Kobayashi, J. Am. Chem. Soc. 2008, 130, 1804–
1805.
Acknowledgments
Financial support from the Netherlands Organisation for Scien-
tific Research (NWO) through VIDI and ECHO grants is gratefully
acknowledged.
Keywords: Microwave chemistry · Imines · Ketimines ·
Condensation reactions
[1] A. B. Charette, in: Chiral Amine Synthesis (Ed.: T. C. Nugent), Wiley-VCH,
Weinheim, Germany, 2010, p. 1–49.
[37] A. R. Moosavi-Zare, M. A. Zolfigol, E. Noroozizadeh, V. Khakyzadeh, A.
Zare, M. Tavasoli, Phosphorus Sulfur Silicon Relat. Elem. 2014, 189, 149–
156.
[38] G. I. Georg, G. C. B. Harriman, S. A. Peterson, J. Org. Chem. 1995, 60,
7366–7368.
[2] D. Xie, L. Yang, Y. Lin, Z. Zhang, D. Chen, X. Zeng, G. Zhong, Org. Lett.
2015, 17, 2318–2321.
[3] H.-M. Zhang, W.-Q. Jia, Z.-Q. Liang, S. Ye, Asian J. Org. Chem. 2014, 3,
462–465.
[4] B. M. Trost, S. M. Silverman, J. Am. Chem. Soc. 2012, 134, 4941–4954.
[5] B. M. Trost, S. M. Silverman, J. Am. Chem. Soc. 2010, 132, 8238–8240.
[6] A. Kondoh, K. Odaira, M. Terada, Angew. Chem. Int. Ed. 2015, 54, 11240–
1244; Angew. Chem. 2015, 127, 11392.
Received: January 8, 2016
Published Online: February 17, 2016
Eur. J. Org. Chem. 2016, 1247–1250
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© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim