Job/Unit: O50224
/KAP1
Date: 02-04-15 13:41:38
Pages: 8
J. K. Vandavasi, C.-T. Hsiao, W.-P. Hu, S. S. K. Boominathan, J.-J. Wang
FULL PAPER
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We have developed a new, convenient, and efficient meth-
odology for the synthesis of β-oxo amides with a broad sub-
strate scope for the first time by AgI catalysis. The crossover
experiments and in situ NMR reaction monitoring results
proved that the reaction does not follow the traditional con-
densation process. A new plausible mechanism was pro-
posed based on mechanistic studies. The key advantages of
this method are the readily available starting materials,
environmental friendliness, air stability and operational
simplicity. Further biological applications are being investi-
gated in our group.
In 2007 the American Chemical Society Green Chemistry Insti-
tute (comprising members from major pharmaceutical indus-
tries worldwide) voted “amide formation avoiding poor atom
economy reagents” as the top challenge for organic chemistry.
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Experimental Section
General Information: Melting points are uncorrected. 1H and 13C
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NMR spectra were recorded at 400 and 100 MHz, respectively, by
using CDCl3 as a solvent. H NMR chemical shifts are referenced
1
to TMS or CDCl3 (δ = 7.26 ppm). 13C NMR chemical shifts are
referenced to CDCl3 (δ = 77.0 ppm). Multiplicities were determined
by the DEPT sequence as s, d, t, q. Mass spectra and high-resolu-
tion mass spectra (HRMS) were measured by using the electron-
impact (EI, 70 eV) technique by Taichung Regional Instrument
Center of NSC at NCHU. IR spectra (attenuated total reflectance,
ATR) were recorded with a Bruker Vertex 80 FT-IR spectrometer,
and only the more representative wavenumbers (ν) are reported in
˜
cm–1. Flash chromatography was carried out on silica gel (E.
Merck, 230–400 mesh).
General Procedure for the Synthesis of β-Oxo Amides (4 or 8) from
β-Oxo Esters Treated with Arylamines: An oven-dried 50 mL
round-bottomed flask was charged with compound
1 or 6
[8]
[9]
(1 mmol), compound 2 (1 mmol), silver triflate (10 mol-%) and
nitromethane (5.0 mL). After stirring at 80 °C for 8 h under air, the
completion of the reaction was monitored by TLC. Removal of the
solvent in vacuo and purification of the residue by silica gel column
chromatography afforded the desired product 4 or 8.
General Procedure for the Synthesis of β-Oxo Amides (11) from β-
Oxo Esters Treated with Alkylamines: An oven-dried 50 mL round-
bottomed flask was charged with compound 1 or 6 (1 mmol), com-
pound 10 (1 mmol), silver triflate (10 mol-%), DBU (1 mmol) and
nitromethane (5.0 mL). After stirring at 80 °C for 2–8 h under air,
the completion of reaction was monitored by TLC. Removal of the
solvent in vacuo and purification of the residue by silica gel column
chromatography afforded the desired product 11.
[10]
[11]
[12]
Procedure for NMR Studies: In an NMR tube compound 1d
(1 equiv.) was dissolved in CD3NO2, and 10 mol-% of AgOTf was
added. The tube was placed in the NMR instrument and the tem-
perature was raised to constant 80 °C. Data was acquired at equal
time intervals at this temperature.
[13]
Acknowledgments
We thank the Ministry of Science and Technology (MOST), Tai-
wan for its financial support.
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