Beyer et al.
•
•
•
studies of the aromatic nitroxides 2 , 4 , and 5 will be
reported in due course.
solid. For the EPR measurements, 3 mL of C
6 6
D was
added and CH Cl was evaporated off under reduced pres-
2
2
sure, yielding a final concentration of 0.4 mM as quantified
+
+
by EPR. MS (MALDI): 186.55 (52, M ), 170.24 (100, M
-
Exp er im en ta l Section
O).
Com p u ta tion a l Deta ils. Sim u la tion a n d F it P r ogr a m .
The simulation program is based on MATLAB. The isotropic
spin Hamiltonian, describing the spin system under study,
includes the electron Zeeman and electron-nuclear spin-spin
interactions. Input data needed for describing the spectrum
are fixed values as center field and microwave frequency, and
3,6-Dim eth ylca r ba zole 3. An 800 mg (2.46 mmol) portion
of dibromocarbazole 6 and 66.7 mg (0.12 mmol) of 1,3-bis-
(diphenylphosphino)dichloronickel(II) (Ni(dppp) Cl ) were sus-
2 2
pended in 60 mL of absolute diethyl ether in a dried and argon-
flushed 100 mL three-necked flask equipped with a reflux
condenser. To the purple red suspension was added 2.5 mL of
variable parameters as giso, hyperfine coupling constants Aiso
,
a 3 M CH MgBr solution in diethyl ether (7.38 mmol) over a
3
and the line width ∆Hpp. The line width was added by means
of a convolution procedure in the Fourier transform space. The
variable parameters are optimized by a simplex fit routine
minimizing the root-mean-square values.
period of 20 min, yielding a brown and clear solution. The
reaction mixture was gently refluxed for 2 h, cooled to room
temperature, and quenched with 8 mL of saturated aqueous
NH
4
Cl solution. The organic phase was treated three times
CO solution, three times
DF T Ca lcu la tion s. All DFT calculations were carried out
within the unrestricted Kohn-Sham formalism as imple-
mented in the GAUSSIAN 98 program package.17 For the
geometry optimizations as well as for the calculations of the
Fermi contact interactions, dipole moments and polarizabilities
with 7 mL of saturated aqueous Na
2
3
with 7 mL of saturated aqueous NaCl solution, and finally
three times with 7 mL of water. The organic phases were
combined and dried over MgSO , and the solvent was removed
4
under vacuo. The crude product was purified by HPLC using
1
8
the PBE0 functional together with the standard 6-31G(d)
basis set was used. In addition, the isotropic hyperfine
n-hexane/ethyl acetate 3:1 as the eluent, yielding 120 mg of 3
0.61 mmol; 24%) as white needles. 1H NMR (250 MHz;
(
1
3
couplings were also computed with the EPR-II basis set
acetone-d
Hz, H2/H7), 7.36 (d, 2H, J ) 8.23 Hz, H1/H8), 7.86 (m, 2H,
H4/H5), 10.01 (bs, 1H, NH). 13C NMR (250 MHz; acetone-d
):
6
): δ 2.48 (s, 6H, CH
3
), 7.19 (dq, 2H, J ) 1.65/8.23
1
4
1
yielding, however, somewhat smaller N but similar
H
hyperfine couplings compared to the 6-31G(d) basis set, as
1
3
6
found before. Therefore, in this work only the data obtained
with the 6-31G(d) basis set are shown.
δ 20.93, 111.43 (2-fold), 120.74, 124.12, 127.64, 128.42. MS
+
(
1
MALDI): 196.79 (100, M + H). IR (KBr): ν 3397, 2912, 2856,
EP R. The cw X-band EPR spectra were acquired on a cw
X-band EPR spectrometer equipped with a TM102 rectangular
-1
612, 1575, 1497, 1467, 1300, 1248, 880, 808 cm . Anal. Calcd
13N (195.26): C, 86.12; H, 6.71; N, 7.17. Found: C,
6.26; H, 6.83; N, 6.98.
,6-Dim eth ylca r ba zole-9-oxyl 3 . A 19.3 mg (0.10 mmol)
portion of 3 was dissolved in 3 mL of CH Cl and cooled to 0
°C. A solution of 25.59 mg (0.15 mmol) of m-CPBA in 1.5 mL
of CH Cl was also cooled to 0 °C and added during 20 min to
•
•
•
for C14H
8
resonator. For the EPR measurements, 2 , 4 , and 5 were
dissolved under argon in dry benzene-d to yield final concen-
6
•
3
trations of 1 mM and transferred into quartz EPR tubes. The
parameters of the signal channel were as follows: modulation
amplitude 0.1 G, modulation frequency 100 kHz, conversion
time 141 ms, time constant 141 ms. The microwave power was
2
2
2
2
1
mW.
the carbazole solution. The reaction mixture was stirred for 2
h and warmed slowly to room temperature. The solution was
Syn th esis. Chemical synthesis under argon was carried out
according to standard Schlenck techniques. The starting
extracted three times with 4 mL of a 5% aqueous Na
2 3
CO
compound 3,6-dibromocarbazole 6 was synthesized by bromi-
nation of 1, and 9-acridanylidenemalonitrile 4 and 9-ethy-
solution, and the yellow organic layer was separated and dried
1
9
•
over MgSO
4
. It was not possible to isolate 3 as a solid. For
lacridanylidenecyanoacetate 5 were synthesized via 9-chlo-
the EPR measurements, 3 mL of C D was added and CH Cl
6
6
2
2
according to literature procedures.2
0,21
9,9-
racridine
7
was removed under reduced pressure, yielding a final concen-
tration of 0.4 mM by means of EPR quantification. MS
•
Diphenylacridane-10-oxyl 2 was synthesized by a slightly
modified procedure described by Greci.
Ca r ba zole-9-oxyl 1 . A 20.5 mg (0.123 mmol) portion of
9
+
+
(MALDI): 214.45 (52, M ), 198.34 (100, M - O).
9
•
•
-Acr id a n ylid en m a lon itr ile-10-oxyl 4 . A 200 mg (0.82
carbazole 1 was dissolved in 3 mL of CH
C. A solution of 31.8 mg (0.184 mmol) of m-CPBA in 1.5 mL
of CH Cl was also cooled to 0 °C and added during 20 min to
2 2
Cl and cooled to 0
mmol) portion of 4 was dissolved in 7 mL of CH
to 0 °C. A solution of 213 mg (1.23 mmol) of m-CPBA in 5 mL
of CH Cl was also cooled to 0 °C and added during 20 min to
2 2
Cl and cooled
°
2
2
2
2
the carbazole solution. The reaction mixture was stirred for 2
h and warmed during this time slowly to room temperature.
Then the solution was extracted three times with 5% aqueous
the first solution. The reaction mixture was stirred for 4 h and
warmed during this time to room temperature. The solution
was treated with 20 mL of a 5% aqueous Na
2 3
CO solution, and
Na
2 3
CO solution, and the yellow organic layer was separated
•
the yellow organic layer was separated and dried over MgSO .
4
and dried over MgSO
4
. It was not possible to isolate 1 as a
•
The solvent was removed under vacuum yielding pure 4 as a
+
+
yellow solid. MS (MALDI): 258.45 (52, M ), 242.43 (100, M
O). Anal. Calcd for C16 O (258.26): C, 74.41; H, 3.12;
N, 16.27. Found C, 74.60; H, 3.03; N, 15.98.
(17) Frisch, M. J .; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.;
-
8 3
H N
Robb, M. A.; Cheeseman, J . R.; Zakrzewski, V. G.; Montgomery, J . A.,
J r.; Stratmann, R. E.; Burant, J . C.; Dapprich, S.; Millam, J . M.;
Daniels, A. D.; Kudin, K. N.; Strain, M. C.; Farkas, O.; Tomasi, J .;
Barone, V.; Cossi, M.; Cammi, R.; Mennucci, B.; Pomelli, C.; Adamo,
C.; Clifford, S.; Ochterski, J .; Petersson, G. A.; Ayala, P. Y.; Cui, Q.;
Morokuma, K.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.;
Foresman, J . B.; Cioslowski, J .; Ortiz, J . V.; Stefanov, B. B.; Liu, G.;
Liashenko, A.; Piskorz, P.; Komaromi, I.; Gomperts, R.; Martin, R. L.;
Fox, D. J .; Keith, T.; Al-Laham, M. A.; Peng, C. Y.; Nanayakkara, A.;
Gonzalez, C.; Challacombe, M.; Gill, P. M. W.; J ohnson, B. G.; Chen,
W.; Wong, M. W.; Andres, J . L.; Head-Gordon, M.; Replogle, E. S.;
Pople, J . A. Gaussian 98, revision A.11; Gaussian, Inc.: Pittsburgh,
PA, 1998.
•
9-Eth yla cr id a n ylid en ecya n oa ceta te-10-oxyl 5 . To 58
mg (0.20 mmol) of 5 in 5 mL of benzene was added 128 µL of
a 5 M solution of tert-butyl hydroperoxide in decane (0.64
mmol). A 58 mg (0.23 mmol) portion of PbO
vigorous stirring at room temperature. After 12 h, 51.7 mg
0.30 mmol) of m-CPBA was added to the dark red solution
resulting after 2 h in an orange red solution. The PbO was
2
was added under
(
2
filtered off, the solvent evaporated, and the crude product
purified by column chromatography over silica gel using
n-hexane/ethyl acetate (1:1) as the eluent (R
f
0.48). Pure 5•
(
(
18) Adamo, C.; Barone, V. J . Chem. Phys. 1999, 110, 6158.
19) Smith, K.; J ames, D. M.; Mistry, A. G.; Faulkner, D. J .
was obtained after crystallization from toluene at 0 °C as a
Tetrahedron 1992, 48, 7479.
20) Vinh Lap, B.; Boux, L. J .; Cheung, H. T. A.; Holder, G. M. J .
Heterocycl. Chem. 1983, 20, 281.
21) Tsuge, O.; Torii, A. Bull. Chem. Soc. J pn. 1973, 46, 283.
+
pale yellow solid. MS (MALDI): 327,0 (27, M + Na), 289.0
(
+
(
100, M - O). Anal. Calcd for C18
H
13
N
2
O
3
(305.31): C, 70.81;
(
H, 4.29; N, 9.18. Found C, 71.01; H, 3.98; N, 9.03.
2
214 J . Org. Chem., Vol. 68, No. 6, 2003