Organic Letters
Letter
selective as amide 6an was formed exclusively. Other cyclic
amines such as morpholine can also be used as shown by the
amidation of 1a to 6ao.
To further demonstrate the potential of our transformation,
we then applied our conditions to the amidation of Evans’
diastereoselective alkylation and aldolization products 1f and
1g. As evidenced by the results presented in Scheme 6, imide
Lewis acid smoothly promotes the cleavage of a wide range of
imides into the corresponding esters, carboxylic acids, amides,
and Weinreb amides. Compared to previously reported
procedures, our process is certainly one of the broadest and
relies on user-friendly and mild reactions conditions which
should facilitate the post-transformation of oxazolidinone-
derived imides, versatile intermediates in chemical synthesis.
ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge on the
Scheme 6. Application of the Ytterbium-Catalyzed
Amidation of Imides to Evans’ Alkylation and Aldolization
Products
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Experimental procedures, characterization, and copies of
Primary NMR data files (ZIP)
AUTHOR INFORMATION
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1f was smoothly converted into the corresponding primary
amide 6ap with an excellent yield, and the amidation of 1g also
proceeded smoothly. Importantly, the reactions proceeded
with complete retention of the stereochemical information.21
In a final effort to further highlight the synthetic potential of
this ytterbium-catalyzed cleavage of imides, we next envisioned
its extension to the preparation of Weinreb amides, a
transformation that is typically performed with N,O-dimethyl-
hydroxylamine hydrochloride and trimethylaluminum. For the
sake of practicality, we decided to directly use commercially
available N,O-dimethylhydroxylamine hydrochloride instead of
the corresponding volatile free base that would then be
generated in situ with additional diisopropylethylamine. Under
these conditions, various imides could be readily and
successfully converted to the corresponding Weinreb amides
as shown by the results presented in Scheme 7. It is important
Corresponding Author
ORCID
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
Our work was supported by the Universite libre de Bruxelles
(ULB) and the FNRS (CDR J.0058.17 Keteniminium).
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REFERENCES
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(1) (a) Evans, D. A.; Bartroli, J.; Shih, T. L. J. Am. Chem. Soc. 1981,
103, 2127. (b) Evans, D. A. Aldrichimica Acta 1982, 15, 23.
(2) For examples, see: (a) Evans, D. A.; Miller, S. J.; Leckta, T.; von
Matt, P. J. Am. Chem. Soc. 1999, 121, 7559. (b) Evans, D. A.; Johnson,
D. S. Org. Lett. 1999, 1, 595. (c) Evans, D. A.; Willis, M. C.; Johnston,
J. N. Org. Lett. 1999, 1, 865.
Scheme 7. Ytterbium-Catalyzed Amidation of Imides to
Weinreb Amides
(3) For representative examples, see: (a) Mulder, J. A.; Hsung, R. P.;
Frederick, M. O.; Tracey, M. R.; Zificsak, C. A. Org. Lett. 2002, 4,
1383. (b) Minko, Y.; Pasco, M.; Lercher, L.; Botoshansky, M.; Marek,
I. Nature 2012, 490, 522. (c) Dos Santos, M.; Davies, P. W. Chem.
Commun. 2014, 50, 6001. (d) Peng, B.; Huang, X.; Xie, L.-G.;
Maulide, N. Angew. Chem., Int. Ed. 2014, 53, 8718.
(4) For representative examples, see: (a) Evans, D. A.; Bender, S. L.
Tetrahedron Lett. 1986, 27, 799. (b) Evans, D. A.; Sjogren, E. B.;
Bartroli, J.; Dow, R. L. Tetrahedron Lett. 1986, 27, 4957. (c) Prashad,
M.; Har, D.; Kim, H.-Y.; Repic, O. Tetrahedron Lett. 1998, 39, 7067.
(d) Prashad, M.; Shieh, W.-Ch; Liu, Y. Tetrahedron 2016, 72, 17.
(5) For representative examples, see: (a) Evans, D. A.; Ennis, M. D.;
Mathre, D. J. J. Am. Chem. Soc. 1982, 104, 1737. (b) Evans, D. A.;
Morrissey, M. M.; Dorow, R. L. J. Am. Chem. Soc. 1985, 107, 4346.
(6) (a) Evans, D. A.; Britton, T. C.; Ellman, J. A. Tetrahedron Lett.
1987, 28, 6141. Lithium hydroxide can also be used, although with
reduced efficiency. For representative examples, see: (b) Evans, D. A.;
Britton, T. C.; Dorow, R. L.; Dellaria, J. F. J. Am. Chem. Soc. 1986,
108, 6395. (c) Woiwode, T. F.; Wandless, T. J. J. Org. Chem. 1999, 64,
7670.
(7) For representative examples, see: Lee, E.; Jeong, E. J.; Kang, E. J.;
Sung, L. T.; Hong, S. K. J. Am. Chem. Soc. 2001, 123, 10131.
(8) Yokomatsu, Y.; Arakawa, A.; Shibuya, S. J. Org. Chem. 1994, 59,
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(9) Sibi, M. P.; Hasegawa, H.; Ghorpade, S. R. Org. Lett. 2002, 4,
3343.
to note that the reaction could easily be performed on a 5 g
scale, with the Weinreb amide 8a then being obtained in 85%
yield, which further demonstrates the robustness and
practicality of our process.21
In conclusion, we have developed a divergent, efficient, and
broadly applicable system for the cleavage of imides with
various nucleophiles. The use of ytterbium(III) triflate as a
D
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