T. Golub, J.Y. Becker / Electrochimica Acta 205 (2016) 207–214
209
(100%), 58, 43; HRMS (ESI): calculated for C7H13NO2 + H: 144.1019;
found: 144.1015.
2.6.9. N-acetyl, 2,3,4,5-tetrahydroazepine (a mixture of two
stereoisomers) [11] (from III)
1H NMR,
: 1.61-2.25 (m, 6H, CH2CH2CH2), 2.09 (1s, 3H, COCH3),
d
2.6.3. N-acetyl, 2-methoxy, 4-pyrroline (from I)
3.66 and 3.73 (2m, 2H, ꢁN-CH2-), 5.22 (m,1H, ꢁCH2-CH=), 6.38 and
1H NMR,
d
: 2.15 (2s, 3H, COCH3), 3.31 (s, 3H, OCH3), 2.60 and
2.75 (2m, 2H, CH2N), 5.60 (1m, 1H, ꢁCH2-CH = ), 6.25 and 6.39 (2m,
1H, N-CH = ); 13C NMR,
: 22.93 (CH3), 39.08 ( CH-CH2-CHN-),
56.71 (OCH3), 84.76 (CH2-CH-N), 112.39, 113.30 (N-CH CH), 119.33
CH-CH2), 170.91 (CO); (MS: m/z: 155 (M+); 142, 126, 113, 100, 84
6.75 (2m,1H, ꢁN-CH = ); 13C NMR,
d
: 22.34 (CH3), 26.74 ( CH-CH2),
¼
27.86 (CH2-CH2-CH2), 31.87 (CH2-CH-N), 45.92 (CH2-CH-N), 119.86
d
¼
(
¼
CH-CH2), 131.34 (N-CH
CH), 171.36 (CO); (MS: m/z: 139 (M+);
¼
¼
124, 111, 97, 82 (100%), 68, 54, 43; HRMS (ESI): calculated for
C8H13NO + H: 140.1070; found: 140.1063.
(¼
(100%), 68, 43; HRMS (ESI): calculated for C7H11NO2 + H: 142.0863;
found: 142.0858. Noteworthy, this product is unstable undergoes a
facile decomposition (various unidentified products, including
ring-opening ones) on standing or after preparative TLC (silica gel)
separation (ethyl acetate (70%)-hexane (30%).
2.6.10. N-acetyl, 2-methoxyhexahydroazepine (a mixture of two
stereoisomers) [11] (from III):
IR (liquid): 2930; 2845, 1650, 1420, 1200, 1080, 930 cmꢁ1 1H
;
NMR,
NCOCH3), 3.20 and 3.22 (2s, 3H, OCH3), 2.84, 3.19-3.25, 3.43 and
3.96 (4m, 2H, CH2N), 4.88 and 5.74 (2m, 1H, OCH); 13C NMR,
d
: 1.17-2.24 (m, 8H, ꢁCH2CH2CH2CH2-), 2.16 and 2.17 (2s, 3H,
2.6.4. N-acetyl, 2,5-dimethoxypyrrolidine (a mixture of two
d
:
stereoisomers, ꢅ1:1) [11] (from I)
21.53, 21.83, 21.99, 22.49, 26.69, 28.70, 29.32, 29.69, 33.95, 34.59,
39.45, 41.72, 54.10 (OCH3), 55.26 (OCH3), 82.35 (OCHN), 87.90
(OCHN), 172.20 (CO); MS: m/z: 171 (M+); 156 (100%), 140, 128, 148,
114 (100%), 98, 82, 71, 43; HRMS (ESI): calculated for C9H17NO2 + H:
172.1322; found: 172.1328; calculated for C7H17NO2 + Na: 194.1152;
found 194.1147.
1H NMR,
d
: 1.74-2.07 (m, 4H, ꢁCH2CH2), 2.04 and 2.07 (2s, 3H,
NCOCH3), 3.17, 3.19, 3.27 and 3.28 (4s, 6H, 2OCH3), 4.62-5.34 (6m,
2H, 2OCHN), 13C NMR,
d
: 14.40, 21.66, 28.05, 54.27 (OCH3), 60.34
(OCH3), 86.84 (OCHN), 89.73 (OCHN), 170.73, 171.99; MS: m/z: 173
(M+); 158, 142, 126, 111, 100 (100%), 84, 68, 60, 43; HRMS (ESI):
calculated for C8H15NO3 + H: 174.1119; found: 174.1125. Calculated
for C8H15NO3 + Na: 196.0944; found: 196.1020.
Noteworthy, this product undergoes a facile hydrolysis to yield
6-acetamidohexanal [8].
2.6.5. N-acetyl-1,2,3,4-tetrahydropyridine (a mixture of two
conformers) [12] (from II)
2.6.11. N-acetyl, 2-methoxy, 2,3,4,5-tetrahydroazepine (a mixture of
1H NMR,
d
: 2.07-2.20 (m, 4H, ꢁCH2CH2CH-), 2.14 and 2.15 (2s,
two stereoisomers) [11] (from III)
1H NMR,
d
: 1.61-2.25 (3m, 6H, ꢁCH2CH2CH2-), 2.15 (1s, 3H,
COCH3), 3.22 (1s, 3H, OCH3), 5.49 (m, 1H, ꢁCH2-CH = ), 5.90 (m, 1H,
OCHN) and 6.05 and 6.39 (2m, 1H, N-CH = ); 13C NMR,
: 18.83
(CH2-CH2-CH2), 22.86 (CH3), 27.73 ( CH-CH2), 33.73 (CH2-CH-N),
55.60 (OCH3), 82.60 (CH2-CH-N), 124.12 ( CH-CH2), 125.44 (N-
CH
CH), 171.26 (CO); MS: m/z: 169 (M+); 154, 137, 126, 110, 98, 71,
3H, NCOCH3), 4.95 (m,1H, NCH2), 3.21 and 3.23 (2s, 3H, OCH3), 2.71,
3.51, 3.72, 4.41 and 5.33, (5m, 2H, CH2N), 4.95 (-CH-CHN), 6.46-
6.57 and 7.18 (3m, 1H, NCH-); 13C NMR,
d: 20.57, 20.63, 20.91,
d
107.32 (CH-CHN), 125.01 (NCH); MS: m/z: 125 (M+); 110, 96, 82
(100%), 68, 60, 54, 43; HRMS (ESI): calculated for C7H11NO + H:
126.0913; found: 126.0908.
¼
¼
¼
56 (100%), 43; HRMS (ESI): calculated for C9H15NO2 + H: 170.1176;
found: 170.1172.
2.6.6. N-acetyl, 2-methoxypiperidine (a mixture of two stereoisomers)
[11] (from II)
1H NMR,
d
: 1.25-2.26 (m, 6H, ꢁCH2CH2CH2-), 2.11 and 214 (2s,
2.6.12. N-acetyl, 2,7-dimethoxyhexahydroazepine (a mixture of two
stereoisomers) [11] (from III)
3H, COCH3), 3.21 and 3.23 (2s, 3H, OCH3), 2.71, 3.51, 3.72, 4.41 and
5.33, (5m, 2H, CH2N), 4.95 and 5.78 (2m, 1H, OCHN); (MS: m/z: 157
(M+); 142, 126, 113, 100, 84 (100%), 68, 43; HRMS (ESI): calculated
for C8H15NO2 + H: 158.1176; found: 158.1173.
IR (liquid): 2940; 2850, 1650, 1420, 1370, 1200, 1140, 1100,
1070 cmꢁ1
;
1H NMR,
d
: 1.11-2.15 (m, 8H, ꢁCH2CH2CH2CH2-), 2.19,
2.25 (2s, 3H, NCOCH3), 3.31, 3.32 and 3.36 (3s, 6H, 2OCH3), 4.55,
4.81 and 5.77 (3m, 2H, OCH), 13C NMR,
: 21.75, 22.84, 23.23, 23.37,
d
2.6.7. N-acetyl, 6-methoxy, 1,2,3,4-tetrahydropyridine (a mixture of
two stereoisomers) [11] (from II)
23.53, 26.02, 32.01, 33.12, 33.36, 33.79, 55.42 (OCH3), 55.80 (OCH3),
56.06 (OCH3), 57.11 (OCH3), 82.42 (OCHN), 85.63 (OCHN), 87.27
(OCHN), 90.12 (OCHN), 172.81 (CO), 173.35 (CO); MS: m/z: 201
(M+); 186, 169, 144, 126, 102, 84, 71 (100%), 60, 43; HRMS (ESI):
calculated for C10H19NO3 + H: 202.1438; found: 202.1433; calculat-
ed for C10H19NO3 + Na: 224.1257; found 224.1252.
IR (liquid): 2935, 2850, 1740 (C
C-N), 1415, 1390, 1320, 1100 cmꢁ1
4H, ꢁCH2CH2-), 2.19 and 2.25 (2s, 3H, NCOCH3), 3.36 and 3.37 (2s,
3H, OCH3), 5.03-5.16 (2m, 1H, CH CH-N), 5.84 (m, 1H, CH-N),
6.45-6.48 (2m, 1H, NCH), 13C NMR,
: 16.90, 17.32, 21.43, 21.88,
25.31, 26.14, 54.51 (OCH3), 56.14 (OCH3), 82.70 (OCHN), 108.96 and
¼
C-N), 1645 (O
¼
C-N), 1675
(O
¼
;
1H NMR,
d
: 1.54-2.27, (m,
¼
¼
d
109.14 (CH
¼
CHN), 121.77 and 123.40 ( CHN), 169.28 (CO); MS: m/
¼
3. Results and Discussion
z: 155 (M+); 140, 123, 113, 98, 82 (100%), 68, 54, 43; HRMS (ESI):
calculated for C8H13NO2 + H: 156.1019; found: 156.1018; calculated
for C8H13NO2 + Na: 178.0838; found 178.0837.
In this study we have adopted former experimental conditions
that afforded “optimal” conditions in terms of yields of products
and selectivity, as follows:
2.6.8. N-acetyl, 2,6-dimethoxypiperidine (a mixture of stereoisomers)
[11] (from II)
- The use of constant current technique in undivided cell (rather
than CPE in a divided cell).
IR (liquid): 2965; 2850,1640,1420,1200,1100,1050,1000 cmꢁ1
;
1H NMR,
(3s, 3H, NCOCH3), 3.23-3.31 and 3.36 (4s, 6H, 2OCH3), 4.81, 4.94,
5.56 and 5.77 (4m, 2H, OCHN), 13C NMR,
: 11.11, 13.43,18.91, 22.50,
d
: 1.25-2.08, (m, 6H, ꢁCH2CH2CH2-), 2.17, 2.18 and 2.24
- Of the 5 anodes previously tested (carbon felt, graphite rod, Pt,
glassy carbon and PbO2) the C anode was chosen.
- Current density of 20 mA cmꢁ2 was selected (from a studied
range of 10 ꢁ 40 mA cmꢁ2).
d
25.25, 26.09, 29.25, 29.73, 30.22, 31.17, 36.53, 41.76, 54.42 (OCH3),
55.17 (OCH3), 55.59 (OCH3), 56.73 (OCH3), 79.20 (OCHN), 84.88
(OCHN), 172.61 (CO); MS: m/z: 185 (M+); 172, 155, 145, 130, 114, 98,
85, 71, 58 (100%), 43.
- Electricity consumption of 14 F/mol of substrate were chosen
(from a range of 5 to 14 F/mol).