Melting points and 1H NMR data for known triazenes (see
Supporting Information) are all in excellent agreement with reported
values.
271 Hz), 121.2, 51.8, 47.2, 24.4, 24.0; IR (CH2Cl2) 2879, 1612,
1402, 1316, 848 cm-1; MS m/z (rel intensity) (EI) 243 [M, 20],
173 (27), 145 (100); HRMS calcd for C11H12F3N3 243.0983, found
243.0983.
N-(4-Methoxyphenylazo)azetidine (1a). Dark brown crystals;
mp 48-49 °C; 1H NMR (300 MHz, CDCl3) δ 7.40-7.37,
6.87-6.84 (AA′XX′, 4H), 4.24 (app. t, J ) 7.5 Hz, 4H), 3.79 (s,
3H), 2.33 (app quintet, J ) 7.5 Hz, 2H); 13C NMR (500 MHz,
DMSO-d6) δ 157.8, 143.6, 121.4, 114.1, 55.2, 54.8, 15.3; IR
Methods. Solvents (OmniSolv grade, except for 1-BuOH and
1-OcOH, ACS grade) were used as received. Solutions of triazenes
(having an absorbance of ca. 0.5 at 350 nm when placed in quartz
cells constructed of 7 × 7 mm Suprasil tubing) were prepared by
transferring 64 µL of an appropriate stock triazene solution in
acetonitrile to a 5-mL flask and diluting to the mark with desired
organic solvent; 2-mL aliquots were subsequently placed in 7 × 7
mm quartz cells. Samples were irradiated using a Rayonet photo-
reactor fitted with one RPR-3500 Å lamp. After an irradiation period
of 30 s, samples were quickly transferred to a spectrophotometer
(equipped with a thermotasted cell compartment connected to a
circulating water bath) where kinetic traces corresponding to cis-
to-trans isomerization were recorded by measuring the increase in
absorbance (at 325 nm) as a function of time. All measurements
were carried out at (21.0 ( 0.1) °C using air-equilibrated samples.
Values for the observed rate constants were obtained by fitting the
kinetic traces to a single exponential function. Reported values
correspond to the average of two to four independent runs. Percent
decomposition values were determined by comparing the absor-
bance obtained at the end of the thermal growth with that recorded
before irradiation. In no case did light exposure in the conventional
spectrophotometer lead to any detectable photoisomerization or
photodecomposition.
(CH2Cl2) 2978, 2883, 1605, 1585, 1503, 1442, 1409, 837 cm-1
;
MS m/z (rel intensity) (EI) 191 [M, 46], 135 (60), 107 (100), 92
(35), 77 (45); HRMS calcd for C10H13N3O 191.1059, found
191.1055.
N-(4-Methoxyphenylazo)perhydroazepine (1e). Light brown
1
solid; mp 45-46 °C; H NMR (300 MHz, CDCl3) δ 7.35-7.33,
6.86-6.83 (AA′XX′, 4H), 4.00-3.68 (br and s overlapped, 7H),
1.80 (br, 4H), 1.59 (br, 4H); 13C NMR (500 MHz, CDCl3) δ 157.3,
145.3, 121.2, 114.0, 55.4, 28.7; IR (CH2Cl2) 2933, 2856, 1604,
1584, 1503, 1460, 1408, 834 cm-1; MS m/z (rel intensity) (EI) 233
[M, 51], 135 (46), 107 (100), 92 (16), 77 (23); HRMS calcd for
C13H19N3O 233.1528, found 233.1530.
N-(Phenylazo)azetidine (3a). Product was isolated from reaction
medium by solvent extraction (with diethyl ether) to afford a yellow
1
oil; H NMR (300 MHz, acetone-d6) δ 7.36 (d, J ) 7.4 Hz, 2H),
7.30 (t, J ) 7.4 Hz, 2H), 7.14 (t, J ) 7.4 Hz, 1H), 4.24 (app t, J
) 7.1 Hz, 4H), 2.36 (app quintet, J ) 7.5 Hz, 2H); 13C NMR (500
MHz, CDCl3) δ 150.4, 128.9, 126.3, 120.7, 55.0, 15.8; IR (CH2Cl2)
2973, 2882, 1596, 1585, 1483, 1459, 766 cm-1; MS m/z (rel
intensity) (EI): 161 [M, 37], 105 (48), 77 (100); HRMS calcd for
C9H11N3 161.0953, found 161.0949.
Calculations were performed using the Gaussian03 package of
programs.20 Full geometry optimization were performed using DFT-
B3LYP method and 6-31G* basis set.
N-(4-Chlorophenylazo)azetidine (4a). Crude product was puri-
fied by recrystallization from ethanol to afford a light brown solid;
mp 56-57 °C; 1H NMR (300 MHz, acetone-d6) δ 7.38-7.29
(AA′BB′, 4H), 4.27 (br, 4H), 2.38 (app quintet, J ) 7.5 Hz, 2H);
13C NMR (500 MHz, CDCl3) δ 149.0, 131.4, 128.9, 121.8, 55.2,
15.8; IR (CH2Cl2) 2978, 2884, 1484, 1396, 835 cm-1; MS m/z (rel
intensity) (EI) 195 [M (35Cl), 26], 139 (44), 113 (32), 111 (100);
HRMS calcd for C9H1035ClN3 195.0563, found 195.0564.
N-(4-Trifluoromethtylphenylazo)azetidine (5a). Yellow crys-
Acknowledgment. Financial support from the Natural Sci-
ences and Engineering Research Council (NSERC) of Canada
and the University of Waterloo is gratefully acknowledged.
Supporting Information Available: Full citation for ref 20,
general synthesis procedure, analytical data for known com-
pounds, copies of NMR spectra for new compounds, photolytic
decomposition yields, UV-vis absorption spectra (MeCN
solution) for all compounds (trans form), potential energy curves
for rotation and inversion pathways for 3b, and calculated
geometries (coordinates), imaginary frequencies (where ap-
plicable), and energies of all stationary points. This material is
1
tals; mp 78-80 °C; H NMR (300 MHz, CDCl3) δ 7.57-7.54,
7.49-7.46 (AA′BB′, 4H), 4.37 (app t, J ) 7.3 Hz, 4H), 2.41 (app
quintet, J ) 7.6 Hz, 2H); 13C NMR (500 MHz, CDCl3) δ 153.1,
2
3
127.5 (q, JC-F ) 32.3 Hz), 126.0 (q, JC-F ) 3.8 Hz), 124.4 (q,
1JC-F ) 272 Hz), 120.6, 55.3, 15.7; IR (CH2Cl2) 2887, 1612, 1399,
1322, 848 cm-1; MS m/z (rel intensity) (EI) 229 [M, 19], 173 (29),
145 (100); HRMS calcd for C10H10F3N3 229.0827, found 229.0824.
N-(4-Trifluoromethylphenylazo)pyrrolidine (5b). Bright or-
ange flakes; mp 113-114 °C; 1H NMR (300 MHz, CDCl3) δ
7.55-7.52, 7.46-7.44 (AA′BB′, 4H), 3.92 (br, 2H), 3.67 (br, 2H),
2.03 (m, 4H); 13C NMR (500 MHz, acetone-d6) δ 155.5, 126.8 (q,
JO8024048
(20) Frisch, M. J. et al. Gaussian 03, ReVision C.02; Gaussian, Inc.:
Wallingford, CT, 2004.
2
1
3JC-F ) 3.8 Hz), 126.4 (q, JC-F ) 31.1 Hz), 125.7 (q, JC-F
)
J. Org. Chem. Vol. 74, No. 4, 2009 1773