4
Tetrahedron
5bh
Acknowledgments
a Reaction conditions: 3 (0.50 mmol), 4a (0.55 mmol), i-PrOH (1.5 mL),
110oC, 10 h.
We are grateful to the Natural Science Foundation of China
(21402137 and 21302135) and the Chemical Engineering &
Technology of Zhejiang Province First-Class Discipline (Taizhou
University) for financial support.
b Isolated yield.
References and notes
1.
2.
3.
(a) Yamada, S.; Takahashi, Y. Tetrahedron Lett. 2009, 50, 5395-
5398. (b) Katritzky, A. R.; He, H.-Y.; Wang, J. J. Org. Chem.
2002, 67, 4951-4956. (c) Bell, S. C.; Gochman, C. U.S. Patent 3
631 061, 1971; d) Bell, S. C.; Gochman, C. U.S. Patent 3 423
459, 1969.
(a) Tsuge, O.; Watanabe, H.; Masuda, K.; Yousif, M. M. J. Org.
Chem. 1979, 44, 4543-4547. (b) Vasvari-Debreczy, L.; Beckett, A.
H.; Vutthikongsirigool, W. Tetrahedron 1981, 37, 4337-4342. (c)
Ren, X.; O’Hanlon, J. A.; Morris, M.; Robertson, J.; Wong, L. L.
ACS Catal. 2016, 6, 6833-6837.
(a) Zheng, L.; Yang, F.; Dang, Q.; Bai, X. Org. Lett. 2008, 10,
889-892. (b) Bi, H.-P.; Teng, Q.; Guan, M.; Chen, W.-W.; Liang,
Y.-M.; Yao, X.; Li, C.-J. J. Org. Chem. 2010, 75, 783-788. (c)
Zhang, C.; Seidel, D. J. Am. Chem. Soc. 2010, 132, 1798-1799. (d)
Das, D.; Richers, M. T.; Ma, L.; Seidel, D. Org. Lett. 2011, 13,
6584-6587. (e) Zhang, C.; Das, D.; Seidel, D. Chem. Sci. 2011, 2,
233-236. (f) Yang, D.; Zhao, D.; Mao, L.; Wang, L.; Wang, R. J.
Org. Chem. 2011, 76, 6426-6431. (g) Firouzabadi, H.; Iranpoor,
N.; Ghaderi, A.; Ghavami, M. Tetrahedron Lett. 2012, 53, 5515-
5518. (h) Dighe, S. U.; Kumar K. S., A.; Srivastava, S.; Shukla, P.;
Singh, S.; Dikshit, M.; Batra, S. J. Org. Chem. 2015, 80, 99-108.
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56, 2720-2723.
Scheme 3. Decarboxylation reaction of 3aa with α-amino
acids
4.
As a comparison, the reaction of ketoamide 3aa with
thioproline 4b failed to afford any product even at an elevated
reaction temperature (Scheme 3). While the reaction of 4-
hydroxy proline with 3aa gave a pyrrole derivative 6 instead of
the desired cyclization product. When acyclic amino acid N-
methylglycine was used, the desired decarboxylative cyclization
product 7 was isolated in 33% yield. However, the reaction of
3aa with N-benzylglycine was rather complex.
Supplementary Material
Supplementary material that may be helpful in the review
process should be prepared and provided as a separate electronic
file. That file can then be transformed into PDF format and
submitted along with the manuscript and graphic files to the
appropriate editorial office.
In conclusion, we have developed an efficient and practical
method for the synthesis of tetrahydro-1H-pyrrolo[1,2-
a]imidazol-2-ones from readily available starting materials based
on the decarboxylative cyclization reaction of α-ketoamides and
proline. In most cases, the reaction proceeded with perfect
diastereoselectivity to give trans-isomer in excellent yield.
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