One-pot Electrochemical Oxidation Synthesis of Nitriles from Alcohols with Hexamethyldisilazane as the Nitrogen Source†

doi:10.7503/cjcu20170245

Abstract

Abstract:

One-pot electrochemical oxidation synthesis of nitriles from alcohols was developed with hexamet-hyldisilazane(HMDS) as the nitrogen source, 2,2,6,6-tetramethylpiperidinyl-1-oxy(TEMPO) as the electrooxidation medium at the room temperature. The catalytic performance of TEMPO was studied by cyclic voltammetry, and the oxidation process was monitored by in situ FTIR analysis. Under the optimized conditions, the constant potential electrolysis of various alcohols, especially of benzylic alcohols, afforded the corresponding nitriles in moderate to excellent yields. Finally, the corresponding reaction mechanism of one-pot electrochemical oxidation of alcohols to nitriles was proposed.

Key words: 2,2,6,6-Tetramethylpiperidinyl-1-oxy(TEMPO), Electrooxidation, Hexamethyldisilazane(HMDS), Alcohol, Nitrile

CLC Number:

O621
O646

TrendMD:

FAN Zhongquan, CHEN Chen, SHEN Zhenlu, LI Meichao. One-pot Electrochemical Oxidation Synthesis of Nitriles from Alcohols with Hexamethyldisilazane as the Nitrogen Source^†[J]. Chem. J. Chinese Universities, 2018, 39(1): 78.

Figures/Tables 8

Scheme 1 One-pot electrochemical synthesis of nitriles from alcohols

Fig.1 Cyclic voltammograms recorded in 0.1 mol/L NaClO4-CH3CN solution in the presence of 1.0 mmol benzyl alcohol(a), 0.15 mmol TEMPO(b), 0.15 mmol TEMPO+1.0 mmol benzyl alcohol(c) and 0.15 mmol TEMPO+1.0 mmol benzyl alcohol+2.5 mmol HMDS+5.0 mmol AcOH(d)

Fig.2 In situ FTIR spectra collected on Pt electrode during the oxidation of 1mmol benzyl alcohol with 0.15 mmol TEMPO, 2.5 mmol HMDS and 5.0 mmol AcOH in 0.1 mol/L NaClO4-CH3CN solution

Table 1 Optimization of electrochemical synthesis of benzonitrilea

Entry	n_HMDS/mmol	x_TEMPO(molar fraction, %)	n_AcOH/mmol	Potential/V	Yield of benzonitrile^b(%)
1	2.5	15	3.0	1.5	27
2	2.5	15	4.0	1.5	88
3	2.5	15	5.0	1.5	95
4	1.0	15	5.0	1.5	62
5	3.0	15	5.0	1.5	97
6	2.5	5	5.0	1.5	58
7	2.5	10	5.0	1.5	84
8	2.5	15	0	1.5	0
9	2.5	15	5.0	1.2	12
10	2.5	15	5.0	1.8	60

Scheme 2 Scheme 2 Silylation reaction

Fig.3 Reaction profiles for electrochemical synthesis of benzonitrile from benzyl alcohol in 0.1 mol/L NaClO4-CH3CN solution containing 0.15 mmol TEMPO, 2.5 mmol HMDS and 5.0 mmol AcOH

Table 2 Electrochemical conversion of various alcohols to nitrilesa

Entry	Time/h	Conversion^b(%)	Yield^b(%)
1	15	>99	99
2	12	>99	98
3	12	>99	95
4	12	>99	>99
5	12	>99	96
6	12	>99	90
7	12	>99	92
8	12	>99	94
9	12	>99	97
10^c	20	>99	68
11^c	15	18
12^c	15	>99	9

Scheme 3 Plausible electrochemical reaction mechanism

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