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B. Capuano et al.
Fast atom bombardment (FAB) mass spectra were obtained
using a JEOL JMS-DX300 mass spectrometer using the matrix
indicated (TG/G, thioglycerol/glycerol; 3NBA, 3-nitrobenzyl
alcohol). Thin-layer chromatography (TLC) was performed on
silica gel 60 F254 pre-coated plates (Merck), and spots were visu-
alized by irradiation with ultraviolet light (254 nm) or by iodine
vapour. Flash chromatography was performed using Merck
Kieselgel 60 (230–400) mesh.
δC (CDCl3) 165.3 (CO), 133.6 (C1), 132.0 (C4), 128.8 (C3, C5),
127.6 (C2, C6). m/z (FAB, TG/G) 122 (100%, [M + H]+).
Photolytic Reaction of Benzoyl Azide 1
and N,N-Dimethylaniline
A solution of 1 (141 mg, 0.96 mmol) in anhydrous N,N-
dimethylaniline (50 mL) was irradiated (254 nm) for 3 h. The
excess amine was removed under vacuum and the resulting dark
brown oil purified by flash chromatography (10:1 hexane/ethyl
acetate) resulting in the isolation of four products.
Benzoyl Azide 1
The least polar fraction (RF 0.34) gave a tan solid, which
recrystallized from hexane to give N-1-[2-(dimethylamino)-
phenyl]benzamide 6 as colourless needles (20 mg, 9%). mp 51–
52◦C (lit.[42] 53◦C). νmax (KBr)/cm−1 3360, 1672. δH (CDCl3)
2.71 (6H, s, 2 × CH3N), 7.09 (1H, app. td, J 7.5, 1.5, H5ꢀ), 7.18
(1H, app. td, J 7.5, 1.5, H4ꢀ), 7.23 (1H, dd, J 8, 1.5, H6ꢀ), 7.49–
7.56 (3H, m, H3, H4, H5), 7.92 (2H, dd, J 8, 2, H2, H6), 8.54
(1H, dd, J 8, 1.5, H3ꢀ), 9.34 (1H, br s, NH). δC (CDCl3) 165.3
(CO), 143.5 (C1ꢀ), 135.8 (C2ꢀ), 134.0 (C1), 132.0 (C4), 129.1
(C3, C5), 127.4 (C2, C6), 125.6 (C4ꢀ), 124.2 (C5ꢀ), 120.3 (C6ꢀ),
120.0 (C3ꢀ), 45.3 (2 × NCH3). m/z (ESI, positive ion, 30V) 241
(100%, [M + H]+).
To an ice-cooled solution of sodium azide (0.56 g, 8.5 mmol) in
water (10 mL) was added dropwise a solution of benzoyl chlo-
ride (830 µL, 1.0 g, 7.1 mmol) in anhydrous acetone (30 mL).
The mixture was vigorously stirred in ice for 2.5 h. The ace-
tone was removed under vacuum, the mixture extracted with
dichloromethane (2 × 50 mL), dried over sodium sulfate, and
concentrated. The resulting colourless oil solidified on stand-
ing and was recrystallized from dichloromethane–hexane to
afford benzoyl azide 1 as colourless needles (0.55 g, 52%). mp
29–31◦C (lit.[38] 32◦C). νmax (KBr)/cm−1 2132, 2100, 1692,
1600. δH (CDCl3) 7.45 (2H, br app. t, J 7.5, H3, H5), 7.61 (1H,
br t, J 7.5, H4), 8.03 (2H, dd, J 7.5, 1, H2, H6). δC (CDCl3) 172.4
(CO), 134.3 (C4), 130.7 (C1), 129.4 (C3, C5), 128.6 (C2, C6).
The next fraction (RF 0.23) gave N-methyl-N,Nꢀ-diphenylurea
5 which recrystallized from dichloromethane–hexane as colour-
less needles (31 mg, 14%). mp 102–105◦C (lit.[43] 106◦C). νmax
(KBr)/cm−1 3296, 1700. δH (CDCl3) 3.32 (3H, s, CH3N), 6.35
(1H, br s, NH), 6.97 (1H, br t, J 7.5, H4ꢀ), 7.21 (2H, br app. t,
J 7.5, H3ꢀ, H5ꢀ), 7.28–7.32 (4H, m, H2, H2ꢀ, H6, H6ꢀ), 7.35 (1H,
t, J 7.5, H4), 7.46 (2H, app. t, J 7.5, H3, H5). δC (CDCl3) 154.0
(CO), 142.7 (C1), 138.6 (C1ꢀ), 129.9 (C3ꢀ, C5ꢀ), 128.4 (C3, C5),
127.4 (C4), 127.0 (C2, C6), 122.5 (C4ꢀ), 119.0 (C2ꢀ, C6ꢀ), 36.9
(CH3N). m/z (ESI, positive ion, 30V) 227 (100%, [M + H]+).
Fraction three (RF 0.18) gave a colourless solid which recrys-
tallized from hexane to afford N-[(methylanilino)methyl]benza-
mide 7 as colourless needles (38 mg, 17%). mp 121–123◦C
(lit.[44] 120–125◦C). δH (d6-DMSO) 3.29 (3H, s, NCH3), 4.89
(2H, d, J 5, HNCH2), 6.66 (1H, t, J 7.5, H4ꢀ), 6.89 (2H, d, J 8,
H2ꢀ, H6ꢀ), 7.17 (2H, app. t, J 7.5, H3ꢀ, H5ꢀ), 7.44 (2H, app. t,
J 7.5, H3, H5), 7.52 (1H, t, J 7, H4), 7.84 (2H, d, J 8, H2, H6),
8.92 (1H, br app. t, J 5, NH). δC (CDCl3) 168.2 (CO), 148.1
(C1ꢀ), 134.3 (C1), 131.8 (C4), 129.6 (C3ꢀ, C5ꢀ), 128.7 (C3, C5),
127.2 (C2, C6), 118.8 (C4ꢀ), 113.8 (C2ꢀ, C6ꢀ), 58.3 (CH2), 38.1
(CH3N). m/z (ESI, positive ion, 30V) 263 (25%, [M + Na]+),
240 (90, [M + H]+), 120 (100).
Photochemistry: General Procedure
A solution of 1 in the anhydrous amine was degassed under
vacuum, fitted with a cold finger of cooling water (10–15◦C),
and then irradiated at 254 nm using a Photochemical Reactors
6W low-pressure mercury lamp.The excess amine was removed
and the reaction mixture analyzed.
Photolytic Reaction of Benzoyl Azide 1
and Triethylamine
A solution of 1 (162 mg, 1.1 mmol) in anhydrous triethy-
lamine (50 mL) was irradiated for 3 h. The solvent was removed
under vacuum to afford a yellow oil which, on standing, was
collected as a white precipitate. Recrystallization from ethyl
acetate–hexane gave N,Nꢀ-diphenylurea 2 as colourless nee-
dles (15 mg, 7%). mp 239–242◦C (lit.[39] 239–241◦C). νmax
(KBr)/cm−1 3348, 3304, 1648. δH (d6-DMSO) 6.96 (2H, br t,
J 7.5, H4, H4ꢀ), 7.27 (4H, br app. t, J 7.5, H3, H3ꢀ, H5, H5ꢀ),
7.46 (4H, dd, J 7.5, 1, H2, H2ꢀ, H6, H6ꢀ), 8.63 (2H, s, 2 × NH).
δC (CDCl3) 152.5 (CO), 139.6 (C1), 128.7 (C3, C3ꢀ, C5, C5ꢀ),
121.7 (C4, C4ꢀ), 118.2 (C2, C2ꢀ, C6, C6ꢀ). m/z (FAB, 3NBA)
213 (100%, [M + H]+).
The most polar fraction (RF 0.1) recrystallized from
dichloromethane as colourless needles (46 mg, 40%), and was
identified as benzamide 4.
The filtrate was subjected to purification by flash chro-
matography (9:1 dichloromethane/ethyl acetate) resulting in the
isolation of a further two products. The least polar fraction (RF
0.37) crystallized from dichloromethane–hexane to give Nꢀ,Nꢀ-
diethyl-N-phenylurea 3 as colourless rosettes (58 mg, 27%).
mp 81–83◦C (lit.[40] 84–85◦C). νmax (KBr)/cm−1 3320, 1638.
δH (CDCl3) 1.22 (6H, t, J 7, 2 × CH2CH3), 3.37 (4H, q, J 7,
2 × CH2CH3), 6.42 (1H, br s, NH), 7.01 (1H, br t, J 7.5, H4),
7.27 (2H, br app. t, J 7.5, H3, H5), 7.40 (2H, br d, J 7.5, H2,
H6). δC (CDCl3) 154.7 (CO), 139.4 (C1), 128.8 (C3, C5), 122.8
(C4), 119.9 (C2, C6), 41.6 (2 × CH2CH3), 13.9 (2 × CH2CH3).
m/z (FAB, TG/G) 193 (100%, [M + H]+).
Photolytic Reaction of Benzoyl Azide 1 and Pyridine
A solution of 1 (141 mg, 0.96 mmol) in anhydrous pyridine
(50 mL) was irradiated (254 nm) for 18.5 h. The excess pyridine
was removed under vacuum and the resulting brown oil puri-
fied by flash chromatography (4:1 chloroform/diethyl ether) to
afford unchanged starting material 1 (37 mg, 25%) and pyridine-
1-benzenecarbonylimide 13. The crude product recrystallized
from dichloromethane–hexane as orange prisms (78 mg, 41%).
mp 175–177◦C (lit.[45] 177.5◦C). νmax (KBr)/cm−1 1590. δH
(d6-DMSO) 7.36–7.43 (3H, m, H3ꢀ, H4ꢀ, H5ꢀ), 7.90 (2H, app. t,
J 7, H3, H5), 8.05 (2H, dd, J 7.5, 1.5, H2ꢀ, H6ꢀ), 8.17 (1H, t, J 7.5,
H4), 8.85 (2H, br d, J 6, H2, H6). δC (d6-DMSO) 175.2 (CO),
143.7 (C4), 139.0 (C1ꢀ), 137.1 (C2, C6), 130.6 (C4ꢀ), 128.3 (C3,
C5), 128.2 (C3ꢀ, C5ꢀ), 126.3 (C2ꢀ, C6ꢀ). m/z (FAB, 3NBA) 199
(100%, [M + H]+).
The more polar fraction (RF 0.1) gave benzamide 4 which was
crystallized from dichloromethane as colourless needles (43 mg,
32%) mp 128–129◦C (lit.[41] 130◦C). νmax (KBr)/cm−1 3388,
1656. δH (CDCl3) 6.30 (2H, br s, NH2), 7.44 (2H, br app. t, J 7,
H3, H5), 7.53 (1H, br t, J 7, H4), 7.83 (2H, br d, J 7.5, H2, H6).