Ether refers to diethyl ether. THF and ether were distilled
under nitrogen from sodium benzophenone ketyl prior to use.
Where dry DCM was used, it was distilled over CaH2. Petrol-
eum ether (PE) refers to the fraction boiling between 40 and 60
ЊC. Other organic compounds were used as received. Column
chromatography was performed using BDH silica gel (40–63
µm). N-(2,2-Dimethylpropylidene)aniline (91%) (1a),27 N-(2,2-
dimethylpropylidene)-4-methoxycarbonylaniline (78%) (1d),28
N-(2,2-dimethylpropylidene)-2,6-dimethylaniline (88%) (1f ),29
and N-benzylidene-1,1-dimethylethylamine (80%) (9a),16 were
prepared as described in the literature.
N-(2,2-Dimethylpropylidene)-2,4,6-trimethylaniline
(1k).
73%, bp 71–73 ЊC/0.7 Torr, δH 1.20 (9H, s, C(CH3)3), 2.02 (6H, s,
ArCH3), 2.23 (3H, s, ArCH3), 6.78 (2H, s, ArH), 7.45 (1H, s,
N᎐CH). (Found: Mϩ 203.1670. C H N requires M 203.1674.
᎐
14 21
Found: C, 82.7; H, 10.4; N, 6.9. Calc. for C14H21N: C, 82.7; H,
10.4; N, 6.9%).
N-(2,2-Dimethylpropylidene)-2,4,6-trifluoroaniline (1l). 85%,
bp 36–38 ЊC/0.7 Torr, δH 1.20 (9H, s, C(CH3)3), 6.55–6.77 (2H,
m, ArH), 7.83 (1H, br s, N᎐CH). (Found: Mϩ 215.0918.
᎐
C11H12F3N requires M 215.0922. Found: C, 61.4; H, 5.7; N, 6.6.
Calc. for C11H12F3N: C, 61.4; H, 5.6; N, 6.5%).
General procedure for the preparation of N-(2,2-dimethylpropyl-
idene)anilines
N-(2,2-Dimethylpropylidene)-3,4,5-trimethoxyaniline
(1n).
72%, bp 120–122 ЊC/0.7 Torr, δH 1.15 (9H, s, C(CH3)3), 3.77
Pivaldehyde (1.29 g, 15 mmol) and the aromatic amine (10
mmol) in benzene (16 cm3) containing toluene-p-sulfonic acid
(ca. 10 mg) were refluxed in a Dean Stark apparatus until the
expected quantity of water had collected. Solvent and excess
pivaldehyde were evaporated, and the imines were purified by
distillation or crystallisation.
(3H, s, OCH3), 3.81 (6H, s, OCH3), 6.23 (2H, s, ArH), 7.68 (1H,
s, N᎐CH). (Found: Mϩ 251.1519. C14H21NO3 requires M
᎐
251.1521. Found: C, 66.9; H, 8.5; N, 5.5. Calc. for C14H21NO3:
C, 66.9; H, 8.4; N, 5.6%).
N-[4-(1,1-Dimethylethyl)benzylidene]-1,1-dimethylethylamine
(9b). This was prepared by a similar method, 79%, bp 130–132
ЊC/1 Torr, δH 1.30 (9H, s, C(CH3)3), 1.35 (9H, s, C(CH3)3), 7.45
N-(2,2-Dimethylpropylidene)-p-toluidine (1b). 85%, bp 94–96
ЊC/20 Torr, δH 1.22 (9H, s, C(CH3)3), 2.35 (3H, s, CH3), 6.94 and
and 7.72 (4H, AAЈBBЈ, ArH), 8.28 (1H, s, N᎐CH). Found: Mϩ
᎐
7.15 (4H, AAЈBBЈ, ArH), 7.70 (1H, s, N᎐CH); m/z (%), 175
᎐
217.1835. C15H23N requires M 127.1830. Found: C, 82.8; H,
10.7; N, 6.5. Calc. for C15H23N: C, 82.9; H, 10.7; N, 6.4%).
(Mϩ, 15), 160 (15), 119 (12), 118 (97), 91 (100), 90 (12). (Found:
Mϩ, 175.1363. C12H17N requires M, 175.1361. Found: C, 82.3;
H, 9.8; N, 7.8. Calc. for C12H17N: C, 82.2; H, 9.8; N, 8.0%).
Photochemical reaction of 1b with DTBP
N-(2,2-Dimethylpropylidene)-4-(1,1-dimethylethyl)aniline
(1c). 79%, bp 80–82 ЊC/0.7 Torr, δH 1.23 (9H, s, C(CH3)3), 1.37
(9H, s, C(CH3)3), 7.01, 7.37 (4H, AAЈBBЈ, ArH), 7.75 (1H, s,
N᎐CH). (Found: Mϩ 217.1822. C H N requires M 217.1830.
Found: C, 82.9; H, 10.7; N, 6.5. Calc. for C15H23N: C, 82.9; H,
10.7; N, 6.4%).
A solution of N-(2,2-dimethylpropylidene)-p-toluidine (40 mg,
0.23 mmol) in DTBP (0.2 cm3) in a quartz tube was deaerated
by purging with nitrogen for 15 min and then photolysed with
light from a 500 W super pressure Hg lamp for 5.5 h at 300 K.
Besides starting materials, and products from DTBP decom-
position, the following products were observed: peak no. 90;
ethane, peak no. 92; isobutene, peak no. 94; isobutane, peak no.
110; pivaldehyde, peak no. 657; toluidine, peak no. 925; m/z (%)
189 (4), 177 (13), 162 (5), 132 (10), 120 (100), 106 (20), 91 (23),
77 (19), 65 (22), probably N-(1,2,2-trimethylpropylidene)-p-
toluidine (12b). Careful search was made for 4-methylbenzo-
nitrile and 1-isocyano-4-methylbenzene, but neither was
detected.
᎐
15 23
N-(2,2-Dimethylpropylidene)-3,5-dimethylaniline (1g). 89%,
bp 92–94 ЊC/0.7 Torr, δH 1.23 (9H, s, C(CH3)3), 2.35 (6H, s,
ArCH3), 6.67 (2H, m, ArH), 6.85 (1H, m, ArH), 7.73 (1H, s,
N᎐CH). (Found: Mϩ 189.1511. C H N requires M 189.1517.
᎐
13 19
Found: C, 82.5; H, 10.2; N, 7.4. Calc. for C13H19N: C, 82.5; H,
10.1; N, 7.4%).
Photochemical reaction of 9b with DTBP
N-(2,2-Dimethylpropylidene)-3,5-bis(1,1-dimethylethyl)aniline
(1h). 60%, mp 88–89 ЊC, δH 1.20 (9H, s, C(CH3)3), 1.35 (18H, s,
ArC(CH3)3), 6.84 (2H, d, J 1.7 Hz, ArH), 7.24 (1H, t, J 1.7 Hz,
N-(4-tert-Butylbenzylidene)-tert-butylamine (23.2 mg, 0.11
mmol) was dissolved in DTBP (0.5 cm3) in a quartz tube, deaer-
ated by purging with nitrogen for 15 min, and photolysed with
light from a 500 W super pressure Hg lamp for 1 h at 320 K.
Besides starting materials, and products from DTBP decom-
position, the only significant product shown by GC–MS was
4-tert-butylbenzonitrile. Isobutene and isobutane were
obscured by added solvent.
ArH), 7.72 (1H, s, N᎐CH). (Found: Mϩ 273.2460. C19H31N
᎐
requires M 273.2456. Found: C, 83.4; H, 11.3; N, 5.1. Calc. for
C19H31N: C, 83.5; H, 11.4; N, 5.1%).
N-(2,2-Dimethylpropylidene)-3,5-dimethoxyaniline (1i). 65%,
bp 108–110 ЊC/1 Torr, δH 1.18 (9H, s, C(CH3)3), 3.79 (6H, s,
OCH3), 6.16 (2H, d, J 2.2 Hz, ArH), 6.28 (1H, t, J 2.2 Hz,
ArH), 7.69 (1H, s, N᎐CH). (Found: Mϩ 221.1419. C H NO
᎐
13 19
2
Photochemical reaction of 1-isocyano-4-chlorobenzene with
DTBP
requires M 221.1416. Found: C, 70.5; H, 8.6; N, 6.4. Calc. for
C13H19NO2: C, 70.6; H, 8.65; N, 6.3%).
A solution of the isonitrile (20 mg, 0.14 mmol) in DTBP
(300 cm3) was deaerated by purging with nitrogen for 15 min
and then photolysed with light from a 500 W super pressure Hg
lamp for 4.5 h at 330 K. GC–MS analysis showed unchanged
reactants, and DTBP decomposition products, together with
the following products. Peak 85; ethane, peak 88; isobutene,
peak 90; isobutane, peak 715; 1-isocyanato-4-chlorobenzene,
peak 769; 4-chloroaniline together with minor unidentified
components.
N-(2,2-Dimethylpropylidene)-3,5-difluoroaniline (1j). 98%, bp
86–87 ЊC/0.5 Torr, δH 1.17 (9H, s, C(CH3)3), 6.42–6.68 (3H, m,
ArH), 7.65 (1H, br s, N᎐CH). (Found: Mϩ 197.1010.
᎐
C11H13F2N requires M 197.1016. Found: C, 67.0; H, 6.5; N, 7.1.
Calc. for C11H13F2N: C, 67.0; H, 6.6; N, 7.1%).
N-(2,2-Dimethylpropylidene)-2,4-dimethoxyaniline
(1m).
68%, bp 100–101 ЊC/0.5 Torr, δH 1.17 (9H, s, C(CH3)3), 3.75
(3H, s, OCH3), 3.77 (3H, s, OCH3), 6.39 (1H, dd, J 8.2, 2.4 Hz,
ArH), 6.45 (1H, d, J 2.4 Hz, ArH), 6.72 (1H, d, J 8.2 Hz, ArH),
Acknowledgements
7.76 (1H, s, N᎐CH). (Found: Mϩ 221.1421. C13H19NO2
᎐
requires: M 221.1416. Found: C, 70.5; H, 8.7; N, 6.2. Calc. for
We thank the EPSRC (Grant GR/L49185/01) and MURST
C13H19NO2: C, 70.6; H, 8.7; N, 6.3%).
(Rome) for financial support.
J. Chem. Soc., Perkin Trans. 2, 2002, 1098–1104
1103