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. 2018 Dec 28;24(1):100.
doi: 10.3390/molecules24010100.

Electrochemical Performance of ABNO for Oxidation of Secondary Alcohols in Acetonitrile Solution

Pengfei Niu  1   2 , Xin Liu  3   4 , Zhenlu Shen  5 , Meichao Li  6   7
Affiliations

Electrochemical Performance of ABNO for Oxidation of Secondary Alcohols in Acetonitrile Solution

Pengfei Niu et al. Molecules. .

Abstract

The ketones was successfully prepared from secondary alcohols using 9-azabicyclo[3.3.1]nonane-N-oxyl (ABNO) as the catalyst and 2,6-lutidine as the base in acetonitrile solution. The electrochemical activity of ABNO for oxidation of 1-phenylethanol was investigated by cyclic voltammetry, in situ Fourier transform infrared spectroscopy (FTIR) and constant current electrolysis experiments. The resulting cyclic voltammetry indicated that ABNO exhibited much higher electrochemical activity when compared with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) under the similar conditions. A reasonable reaction mechanism of the electrocatalytic oxidation of 1-phenylethanol to acetophenone was proposed. In addition, a series of secondary alcohols could be converted to the corresponding ketones at room temperature in 80⁻95% isolated yields.

Keywords: ABNO; electrochemical; in situ FTIR; ketones; secondary alcohols.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Scheme 1
Scheme 1
The electrochemical synthesis of ketones from secondary alcohols.
Figure 1
Figure 1
Cyclic voltammograms of Pt electrode in 0.1 M NaClO4-CH3CN solution with (a) 1-phenylethanol (1.0 mmol) and 2,6-lutidine (1.0 mmol); (b) active oxoammonium cations (ABNO) (0.1 mmol); (c) ABNO (0.1 mmol) and 1-phenylethanol (1.0 mmol); and, (d) ABNO (0.1 mmol), 1-phenylethanol (1.0 mmol) and 2,6-lutidine (1.0 mmol) at the scan rate of 50 mV·s−1.
Figure 2
Figure 2
Cyclic voltammogram of Pt electrode in 0.1 M NaClO4-CH3CN solution with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) (0.1 mmol) at the scan rate of 50 mV·s−1.
Figure 3
Figure 3
(A) Cyclic voltammograms for the oxidation of 1-phenylethanol (1.0 mmol) with ABNO (0.1 mmol) and 2,6-lutidine (1.0 mmol) in 0.1 M NaClO4-CH3CN solution at various scan rates. (B) Linear plot between the oxidation peak current (Ip) and the square root of scan rate.
Figure 4
Figure 4
In situ FTIR spectra collected on Pt disk electrode during the oxidation of 1-phenylethanol (1.0 mmol) in the presence of ABNO (0.1 mmol) and 2,6-lutidine (1.0 mmol) in 0.1 M NaClO4-CH3CN solution in a short time interval 10 s.
Figure 5
Figure 5
In situ time-resolved FTIR spectra collected on Pt disk electrode during the oxidation of 1-phenylethanol (1.0 mmol) in the presence of ABNO (0.1 mmol) and 2,6-lutidine (1.0 mmol) in 0.1 M NaClO4-CH3CN solution at 400 mV.
Figure 6
Figure 6
Comparison of in situ FTIR spectra collected on Pt disk electrode during the oxidation of 1-phenylethanol (1.0 mmol) in the presence of 2,6-lutidine (1.0 mmol) at 400 mV. (a) without any catalyst, (b) with TEMPO (0.1 mmol) as the catalyst, (c) with ABNO (0.1 mmol) as the catalyst.
Scheme 2
Scheme 2
A plausible mechanism for the oxidation of 1-phenylethanol in the presence of ABNO and 2,6-lutidine (M).
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