The Journal of Organic Chemistry
Article
mediated by the solvent could be evaluated. The Gaussian 09
software25 was used for all the theoretical calculations.
based promoter and proper acid might improve the conversion
of 6 and the selectivity of 7 by pushing 8 back to K.
ASSOCIATED CONTENT
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EXPERIMENTAL SECTION
■
S
* Supporting Information
1
13
General Information. H and C NMR spectra were recorded
on a 400 MHz spectrometer. The progress of all reactions was
monitored by TLC on precoated silica gel plates. Column
chromatography was performed using silica gel (100−200 mesh)
with ethyl acetate and petroleum ether as eluent, unless otherwise
indicated. Solvents and reagents were obtained from commercial
sources. Solvents were anhydrous unless otherwise noted.
General Procedure for Beckmann Rearrangement of 1
(Table 1 and Scheme 2). To a solution of benzophenone oxime 1
in anhydrous CH3CN were added the corresponding reagants [3/
HCl/(3 + HCl)/TsCl/5] under a nitrogen atmosphere, and the
reaction mixture was heated at the corresponding temperature (90 or
40 °C, depending on the reagants). After completion, the solution was
concentrated on rotary vacuum evaporator and purified by column
chromatography on silica gel (5% EtOAc/petroleum Ether) to give the
product N-phenylbenzamide (2). Mp: 164−165 °C (lit.21 mp 164−
165 °C). 1H NMR (400 MHz, CDCl3): δ 8.03 (s, 1H), 7.87 (d, J=7.3
Hz, 2 H), 7.66 (d, J=7.9 Hz, 2 H), 7.54 (t, J=7.3 Hz, 1 H), 7.46 (t,
J=7.4 Hz, 2 H), 7.37 (t, J=7.9 Hz, 2 H), 7.16 (t, J=7.4 Hz, 1 H). 13C
NMR (100 MHz, CDCl3): δ 165.9, 138.0, 135.0, 131.8, 129.1, 128.8,
127.1, 124.6, 120.3.
1
Copies of H and 13C NMR spectra of compound 2, crystal
data for compounds 3 (CCDC 917941) and 4 (CCDC
917942), GC−MS data for the reactions of 6, computational
details, figures for optimized geometries in Schemes 1, 3, 4, and
6, and Cartesian coordinates for optimized geometries. This
material is available free of charge via the Internet at http://
AUTHOR INFORMATION
Corresponding Author
Notes
■
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
The National Natural Science Foundation of China (No.
20602011, 20972047), the Fundamental Research Funds for
the Central Universities, the Shanghai Committee of Science
and Technology (No. 11DZ2260600), the National University
of IrelandGalway, and the Faculty of Science of the
University of Gothenburg are gratefully acknowledged for
financial support.
Preparation of 3.17 To a stirred solution of ketoxime 1 (2 mmol)
in anhydrous THF (8 mL) at −40 °C was added LDA (1.1 equiv, 2
M) dropwise under a nitrogen atmosphere, and the mixture was stirred
at −40 °C for 30 min. Then a solution of (Z)-N-((1H-benzo[d]-
[1,2,3]triazol-1-yl)(phenyl)methylene)aniline22 (1.0 equiv) in dry
THF (5 mL) was added slowly, and the reaction mixture was heated
to reflux and stirred for another 3 h. After completion, the solvent was
removed on a rotary vacuum vaporator, and the residue was extracted
with n-hexane at −40 °C and recrystallized with ethanol to give 3 as a
light yellow solid in 27.0% yield (203 mg). The stucture of compound
3 was identified by X-ray crystallography.
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Transformation of 3 to 4. To a stirred solution of ketoxime 3
(37.6 mg, 0.1 mmol) in anhydrous CH3CN (0.3 mL) was added HCl/
CH3CN (0.2 mL, 0.1 M) under a nitrogen atmosphere, and the
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Beckmann Rearrangement of 6 by TsCl and the Reaction of
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Computational Details. The density functional theory (DFT)
method M062X23 was used to study the Gibbs free energy profiles of
different pathways. To take the solvent effect into account, all
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solvent (CH3CN) through the integral equation formalism of the
polarized continuum model (IEFPCM).24 Geometries were optimized
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at the same level of theory to ensure that these were stationary
structures on their respective energy surfaces and to extract Gibbs free
energy corrections at 298 K. Intrinsic reaction coordinate (IRC)
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several systems, explicit solvent molecules (CH3CN) were included, so
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dx.doi.org/10.1021/jo400278c | J. Org. Chem. XXXX, XXX, XXX−XXX