Synthesis of carbazoles from N-(N,N-diarylamino)phthalimides with aluminum chloride via diarylnitrenium ions

Article abstract of DOI:10.1021/jo016124r

Generation of diarylnitrenium ions from N-(N,N-diarylamino)phthalimides by treatment with AlCl₃ in benzene or in 1,2-dichloroethane leads to formation of carbazoles by intramolecular C-C bond formation. The reaction proceeds in synthetically useful yields.

Full text of DOI:10.1021/jo016124r

8612
J . Org. Chem. 2001, 66, 8612-8615
Syn th esis of Ca r ba zoles fr om N-(N,N-Dia r yla m in o)p h th a lim id es
w ith Alu m in u m Ch lor id e via Dia r yln itr en iu m Ion s
Yasuo Kikugawa,* Yutaka Aoki, and Takeshi Sakamoto
Faculty of Pharmaceutical Sciences, J osai University, 1-1 Keyakidai, Sakado, Saitama 350-0295, J apan
kikugawa@josai.ac.jp
Received September 17, 2001
Generation of diarylnitrenium ions from N-(N,N-diarylamino)phthalimides by treatment with AlCl3
in benzene or in 1,2-dichloroethane leads to formation of carbazoles by intramolecular C-C bond
formation. The reaction proceeds in synthetically useful yields.
Sch em e 1
In tr od u ction
From the extensive work of Gassman and his group,
the nitrenium ion has received increasing attention from
synthetic, theoretical, and biological perspectives.1 How-
ever, despite the potential utility of the nitrenium ion as
an electrophilic nitrogen, its synthetic applications re-
main limited, mainly because it is a short-lived reaction
intermediate.
Previously, we reported that N-phenylaminophthal-
imide reacts with AlCl3 in benzene to generate a phen-
ylnitrenium ion that is trapped by benzene to give o- and
p-aminobiphenyls and N-phenylaniline.2 On the other
hand, with N-(N-methyl-N-phenylamino)phthalimide, the
cleavage of the N-N bond results in a positive charge
exclusively on the para position of the methylamino
group, and 4-methylaminobiphenyl was obtained in 91%
yield.3 In an extension of this work, we now have
investigated the reaction of N-(N,N-diarylamino)phthal-
imides (1) with AlCl3 in benzene, with the expectation
that AlCl3-mediated cleavage of the N-N bond might give
a diarylnitrenium ion.4
carbon to form a new C-C bond rather than being
attacked intermolecularly by solvent benzene to give N-o-
and -p-biphenyl-N-phenylamines.
Resu lts a n d Discu ssion
Two reports of generation of a diarylnitrenium ion have
hitherto appeared. In one, photolysis of N-(diphenyl-
amino)-2,4,6-trimethylpyridinium tetrafluoroborate5 gave
diphenylamine (10%) and carbazole (3%) in low yields.
In a second report, decomposition of 1,1-diphenylhydra-
zine with trifluoromethanesulfonic acid in benzene6
produced only N-p-biphenyl-N-phenylamine (89%).
To develop a synthetically more useful carbazole
synthesis, we investigated the production of 3 with
different Lewis acids (AlCl3, TiCl4, and BF3‚OEt2). We
found that AlCl3-mediated decomposition of 1 gives the
best results. With other Lewis acids, a large amount of
unreacted starting material remained under comparable
reaction conditions. For example, treatment of 1a with
BF3‚OEt2 (10 mol equiv) in benzene for 24 h at room
temperature afforded recovery of 1a in 92% yield. Various
solvents such as benzene, toluene, 1,3,5-trimethylben-
zene, penta- and hexafluorobenzenes, chlorobenzene, 1,2-
dichloroethane, carbon disulfide, and tetrahydrofuran
Treatment of N-(N,N-diphenylamino)phthalimide (1a )
with AlCl3 (5 mol equiv) in benzene for 4 h at room
temperature gave carbazole (81%) along with N-p-biphen-
yl-N-phenylamine (11%), which indicates that AlCl3-
mediated heterolytic cleavage of the N-N bond produces
a diphenylnitrenium ion (2a ). Intramolecular trapping
of canonical forms involving one of the benzene rings by
the adjacent ring would produce carbazole (3a ). In
principle, arylation of the phenylnitrenium intermediate
could occur at three distinct sites where the positive
charge is preferentially located. Attack could occur at
nitrogen, at the para ring carbon, or at the ortho ring
carbons. In the present case, the ortho ring carbon is
attacked intramolecularly by the adjacent ortho ring
* To whom correspondence should be addressed. Fax: +81-49-271-
7984.
(1) (a) Gassmann, P. G. Acc. Chem. Res. 1970, 3, 26. (b) Abramovitch,
R. A.; J eyaraman, R. In Azides and Nitrenes; Scriven, E. F. V., Ed.;
Academic Press: New York, 1984; pp 297-357.
(2) Ohwada, A.; Li, H.; Sakamoto, T.; Kikugawa, Y. Heterocycles
1997, 46, 225.
(3) Ohwada, A.; Nara, S.; Sakamoto, T.; Kikugawa, Y. J . Chem. Soc.,
Perkin Trans. 1 2001, 3064.
(4) Moran, R. J .; Falvey, D. E. J . Am. Chem. Soc. 1996, 118, 8965.
(5) Moran, R. J .; Cramer, C.; Falvey, D. E. J . Org. Chem. 1997, 62,
2742.
(6) Ohta, T.; Miyake, S.; Shudo, K. Tetrahedron Lett. 1985, 26, 5811.
10.1021/jo016124r CCC: $20.00 © 2001 American Chemical Society
Published on Web 11/15/2001

Synthesis of Carbazoles
J . Org. Chem., Vol. 66, No. 25, 2001 8613
Sch em e 2
Ta ble 1. Rea ction of N-(N,N-Dia r yla m in o)p h th a lim id es w ith AlCl3
a
For methods A, B, and C (see Experimental Section).
also were examined. Among these, benzene proved to be
the solvent of choice despite formation of phenylated
byproducts. 1,2-Dichloroethane is also suitable in some
cases. As for the examination of leaving groups from the
diarylamine moiety, we have synthesized N-amino, N-
benzoyl, and N-succinoyl derivatives (5, 6, and 7, respec-
tively) in addition to phthalimide derivatives (1). From
6, the reaction did not proceed at all and starting
compound (6) was recovered in 91% yield. From 5, 7, and
1a , carbazole was obtained in yields of 33%, 57%, and
81%, respectively. From this result, it is clear that the
phthalimido group plays an important role for the
generation and stabilization of a diarylnitrenium ion.
This allows formation of carbazole in good yield by
intramolecular cyclization. Several carbazoles (3) were
obtained in this way. The results are presented in Table
1.
In the case of 1e and 1i, which have a methyl group
substituted at the para position to nitrogen, some adjust-
ments to the reaction procedure were necessary to obtain

8614 J . Org. Chem., Vol. 66, No. 25, 2001
Kikugawa et al.
Sch em e 3
F igu r e 1.
which a methoxy group can be introduced at the final
stage of manipulation of reactions will be potentially
useful for the synthesis of other methoxycarbazole de-
rivatives, depending on the availability of the corre-
sponding bromo compound.11
In conclusion, diarylnitrenium ions were generated
from N-(N,N-diarylamino)phthalimides with AlCl3 and
carbazoles were obtained by intramolecular C-C bond
formation.
Exp er im en ta l Section
F igu r e 2.
Gen er a l Meth od s. Melting points are uncorrected. NMR
spectra were recorded at 270 MHz (1H) and 125 MHz (13C) in
CDCl3 with TMS as the internal reference. Mass spectra were
measured with direct inlet system at 70 eV. Elemental
analyses were performed in the Microanalytical Laboratory
of this university. All purchased reagents were of reagent-
grade quality and were used without further purification.
Ma ter ia ls. The synthesis of starting materials (1a -g) were
reported previously,12 and 1i was prepared according to the
same procedure.12 Compound 1h was prepared from N-(4-
bromophenyl)-N-(2,5-dimethylphenyl)amine (11) by N-nitro-
sation, subsequent reduction, and finally phthaloylation2
according to the published procedure.13 Compound 11 was
obtained by Ullmann14 reaction of N-(2,5-dimethylphenyl)-
acetamide with 1,4-dibromobenzene followed by hydrolysis of
the acetamido group according to the same literature method.13
N-[N-(4-Br om op h en yl)-N-(2,5-d im eth ylp h en yl)a m in o]-
p h th a lim id e (1h ). A pale yellow solid: mp 148 °C (petroleum
ether); IR (KBr) 1790, 1740, 1590, 1490 cm-1; 1H NMR (CDCl3)
δ 2.28 (s, 3H), 2.36 (s, 3H), 6.43 (d, J ) 8.8 Hz, 2H), 7.06 (d, J
) 7.7 Hz, 1H), 7.16 (d, J ) 7.7 Hz, 1H), 7.27 (d, J ) 8.8 Hz,
2H), 7.39 (s, 1H), 7.77-7.85 (m, 2H), 7.88-7.96 (m, 2H); 13C
NMR (CDCl3) δ 17.88, 20.91, 112.53, 114.95, 123.89, 128.04,
129.05, 129.60, 131.26, 132.09, 133.87, 134.84, 137.50, 140.81,
144.89, 166.30; EI-MS m/z 422 (M+ + 2, 75.5), 420 (M+, 74.4),
194 (100). Anal. Calcd for C22H17N2O2Br: C, 62.72; H, 4.07;
N, 6.65. Found: C, 62.71; H, 4.14; N, 6.69.
products in acceptable yields. According to method A, the
color of the reaction mixture containing 1e quickly turned
from brown to black and considerable amounts of tarry
products were obtained. The yield of 3e was improved
very much by slow addition of 1e in 1,2-dichloroethane
to AlCl3 in 1,2-dichloroethane (entry 9). On the other
hand, using this procedure, we obtained 3i again in low
yield from 1i (entry 13). Careful isolation of the other
products of this reaction indicated the presence of 8 and
trace amounts of the dimeric product (9). The use of a
dilution method (method C) improved the yield of 3i
somewhat (52%, entry 14). Generally, the method that
has been most utilized for the preparation of aromatic
carbazoles from noncarbazole precursors is the dehydro-
genation of 1,2,3,4-tetrahydrocarbazoles.7 The Fischer
cyclization reaction can afford 1,2,3,4-tetrahydrocarba-
zoles. However, the cyclization of the 2,5-dimethyl phen-
ylhydrazone of cyclohexanone yielded a mixture of 1,2-,
1,4-, and 2,4-dimethylcarbazoles as the results of methyl
migration prior to dehydrogenation.8 Using the present
method, we obtained 1,4-dimethylcarbazole (3g) in 89%
yield from 1g and no methyl migration was observed
(entry 11).
N -[N -(2-B r o m o-4-m e t h ylp h e n yl)-N -p h e n y la m in o ]-
p h th a lim id e (1i). Pale yellow crystals: mp 246-248 °C (CH2-
Cl2); IR (KBr) 1800, 1740, 1600 cm-1; 1H NMR (CDCl3) δ 2.23
(s, 3H), 6.69 (d, J ) 8.1 Hz, 2H), 6.93 (t, J ) 7.3 Hz, 1H), 7.13
(dd, J ) 8.1, 1.8 Hz, 1H), 7.22 (t, J ) 7.9 Hz, 2H), 7.48 (s, 1H),
7.58 (d, J ) 8.1 Hz, 1H), 7.76-7.84 (m, 2H), 7.86-7.94 (m,
2H); 13C NMR (CDCl3) δ 20.67, 114.96, 121.58, 121.83, 123.83,
128.93, 129.19, 129.44, 129.63, 134.49, 134.75, 138.92, 139.51,
145.07, 166.02; EI-MS m/z 408 (M+ + 2, 91.1), 406 (M+, 91.2),
327 (27.6), 180 (100). Anal. Calcd for C21H15N2O2Br: C, 61.93;
H, 3.71; N, 6.88. Found: C, 61.88; H, 3.86; N, 6.85.
Syn th esis of Mu r r a ya folin e A. In the case of meth-
oxy-substituted 1, the reaction did not proceed smoothly
and production of many compounds was observed by TLC
analysis. For the synthesis of methoxycarbazoles, the
corresponding bromocarbazoles are synthesized by the
present method, and the replacement of the bromine
atom with a methoxy group was carried out by the
reported method.9
We applied this strategy to the synthesis of a carbazole
alkaloid, 1-methoxy-3-methyl-9H-carbazole (murrayafo-
line A) (10), using the same methodology described above.
This member of the 1-oxygenated C13-carbazole class of
alkaloids has been synthesized by several methods.10 We
achieved the synthesis of 10 in 92% yield by direct
methoxide displacement of bromine from 1-bromo-3-
methyl-9H-carbazole (3i). The present procedure by
The carbazoles (3a -g, 4c) and 4a are known compounds,
and their physical constants and spectral data are in agree-
ment with the literature data. 9H-Ca r ba zole (3a ): mp 240-
243 °C (lit.15 245 °C). 3-Ch lor o-9H-ca r ba zole (3b): mp 202-
(11) Lancelot, J .-C.; Rault, S.; Robba, M.; Dung, N. H. Chem. Pharm.
Bull. 1987, 35, 425.
(12) Aoki, Y.; Saito, Y.; Sakamoto, T.; Kikugawa, Y. Synth. Commun.
2000, 30, 131.
(7) J oule, J . A. Adv. Heterocycl. Chem. 1984, 35, 83.
(8) Luis, S. V.; Burguete, M. I. Tetrahedron 1991, 47, 1737.
(9) Kikugawa, Y.; Miyake, Y.; Kawase, M. Chem. Pharm. Bull. 1981,
29, 1231.
(10) (a) Martin, T.; Moody, C. J . J . Chem. Soc., Perkin Trans. 1 1988,
235. (b) Moody, C. J . Synlett 1994, 681. (c) Bringmann, G.; Tasler, S.;
Endress, H.; Peters, K.; Peters, E.-M. Synthesis 1998, 1501.
(13) Ishi, H.; Sugiura, T.; Kogusuri, K.; Watanabe, T.; Murakami,
Y. Chem. Pharm. Bull. 1991, 39, 572.
(14) (a) Ullmann, F. Ber. Dtsch. Chem. Ges. 1903, 36, 2382. (b)
Weston, P. E.; Adkins, H. J . Am. Chem. Soc. 1959, 50, 859. (c) Fanta,
P. E. Synthesis 1974, 9.
(15) Zelinsky, N. D.; Titz, I.; Gaverdowskaja, M. Ber. Dtsch. Chem.
Ges. 1926, 59, 2590.

Synthesis of Carbazoles
J . Org. Chem., Vol. 66, No. 25, 2001 8615
205 °C (lit.16 198-199 °C). 2-Ch lor o-9H-ca r ba zole (3c): mp
242-244 °C (lit.17 241 °C). 4-Ch lor o-9H-ca r ba zole (4c): mp
94-95 °C (lit.17 95 °C). 1-Br om o-9H-ca r ba zole (3d ): mp
110-111 °C (lit.18 111-112 °C). 3-Met h yl-9H -ca r b a zole
(3e): mp 204-206 °C (lit.19 207-208 °C). 2-Meth yl-9H-
ca r ba zole (3f): mp 269-274 °C (lit.19 264-266 °C). 1,4-
Dim eth yl-9H-ca r ba zole (3g): mp 97-98 °C (lit.19 98.2-98.3
°C). N-(Bip h en yl-4-yl)-N-p h en yla m in e (4a ): mp 113 °C
(lit.20 112 °C).
Gen er al P r ocedu r e: Reaction of N-(N,N-Diar ylam in o)-
p h th a lim id es (1) w ith AlCl3. Meth od A. To a solution of 1
(1 mmol) in benzene (10 mL) was added AlCl3 (5 equiv) at room
temperature, and the progress of the reaction was monitored
by TLC. When TLC indicated the disappearance of starting
material, the reaction was quenched with 10% NaOH under
ice cooling, and the aqueous layer was extracted with EtOAc.
The organic layer was washed with brine, dried over Na2SO4,
filtered, and concentrated. Purification by column chromatog-
raphy over silica gel (n-hexane/EtOAc ) 5:1-2:1) afforded the
corresponding products.
δ 20.26, 21.19, 103.70, 111.18, 112.81, 116.87, 118.61, 119.44,
119.49, 124.10, 124.76, 125.59, 128.09, 128.76, 129.21, 130.41,
131.20, 133.02, 133.26, 135.56, 136.80, 138.59, 138.63, 141.09;
EI-MS m/z 522 (M+ + 2, 51.7), 520 (M+, 100), 518 (50.5), 260
(10.4). Anal. Calcd for C26H20N2Br2: C, 60.02; H, 3.87; N, 5.38.
Found: C, 59.89; H, 3.82; N, 5.11.
8,8′-Dibr om o-6,6′-d im eth yl-9H,9′H-[3,3′]bica r ba zoyl (9).
White solid: mp 260-268 °C; IR (KBr) 3420, 1570, 1510, 1300
cm-1; 1H NMR (DMSO-d6) δ 2.50 (s, 6H), 7.48 (s, 2H), 7.64 (d,
J ) 8.6 Hz, 2H), 7.85 (dd, J ) 8.6, 2.0 Hz, 2H), 8.07 (s, 2H),
8.51 (s, 2H), 11.33 (br s, 2H); 13C NMR (CDCl3) δ 20.57, 103.09,
111.80, 118.47, 119.64, 123.09, 124.47, 125.44, 128.79, 129.13,
132.54, 136.76, 139.15; EI-MS m/z 520 (M+ + 2, 51.7), 518 (M+,
100), 516 (50.8), 439 (8.8), 437 (10.6), 357 (8.4), 259 (9.0), 218
(7.3), 179 (12.9); HR-MS (FAB) m/z for C26H18N2Br2 calcd
515.9836, found 515.9841.
Rea ction of N-[N-(2-Br om o-4-m eth ylp h en yl)-N-p h en yl-
a m in o]p h th a lim id e (1i) w ith AlCl3. Meth od C. A solution
of 1i (0.600 g, 1.47 mmol) in 1,2-dichloroethane (10 mL) was
added dropwise to a mixture of AlCl3 (2.79 g, 22.1 mmol) and
1,2-dichloroethane (700 mL) over 40 min at room temperature.
After the mixture was stirred for 20 min, the reaction was
quenched with 10% NaOH under ice cooling. The organic layer
was washed with brine (2 × 100 mL), dried over Na2SO4,
filtered, and concentrated. Purification by column chromatog-
raphy over silica gel (n-hexane/THF ) 10:1) afforded 3i (0.199
g, 52%) as a white solid: mp 71-72 °C (n-hexane); IR (KBr)
Meth od B. To a mixture of AlCl3 (5 equiv) and 1,2-
dichloroethane (10 mL) was added dropwise a solution of 1 (1
mmol) in 1,2-dichloroethane (2 mL) at room temperature, and
the progress of the reaction was monitored by TLC. When TLC
indicated the disappearance of starting material, the reaction
was quenched with 10% NaOH under ice cooling, and the
aqueous layer was extracted with CH2Cl2. The organic layer
was washed with brine, dried over Na2SO4, filtered, and
concentrated. Purification by column chromatography over
silica gel (n-hexane/EtOAc ) 5:1-2:1) afforded the correspond-
ing products.
1
3400, 2920, 1620, 1570, 1500 cm-1; H NMR (CDCl3) δ 2.51
(s, 3H), 7.20-7.28 (m, 1H), 7.38-7.50 (m, 3H), 7.80 (s, 1H),
8.01 (d, J ) 7.7 Hz, 1H), 8.15 (br s, 1H); 13C NMR (CDCl3) δ
21.15, 103.59, 110.97, 119.36, 119.81, 120.71, 123.51, 124.61,
6-Br om o-1,4-dim eth yl-9H-car bazole (3h ).21 Colorless crys-
tals: mp 137-138 °C (EtOAc/n-hexane); IR (KBr) 3400, 1590,
126.34, 129.04, 130.29, 136.32, 139.40; EI-MS m/z 261 (M+
+
2, 96.4), 259 (M+, 100), 180 (68.8), 152 (11.1), 90 (15.9). Anal.
Calcd for C13H10NBr: C, 60.02; H, 3.87; N, 5.38. Found: C,
60.07; H, 3.87; N, 5.21.
1
1460 cm-1; H NMR (CDCl3) δ 2.53 (s, 3H), 2.82 (s, 3H), 6.95
(d, J ) 7.7 Hz, 1H), 7.16 (d, J ) 7.3 Hz, 1H), 7.36 (d, J ) 8.1
Hz, 1H), 7.50 (dd, J ) 8.4, 1.8 Hz, 1H), 8.10 (br s, 1H), 8.26 (s,
1H); 13C NMR (CDCl3) δ 16.50, 20.38, 111.78, 112.12, 117.17,
120.47, 121.21, 125.03, 126.15, 126.82, 127.64, 130.98, 137.89,
139.11; EI-MS m/z 275 (M+ + 2, 99.9), 273 (M+, 100), 260
(16.4), 194 (28.8). Anal. Calcd for C14H12NBr: C, 61.33; H, 4.41;
N, 5.11. Found: C, 61.54; H, 4.36; N, 4.99.
1-Meth oxy-3-m eth yl-9H-ca r ba zole (Mu r r a ya folin e A)
(10). DMF (10 mL), CuI (95%, 0.373 g, 1.86 mmol), and 3i
(0.242 g, 0.930 mmol) were added to a solution of metallic
sodium (0.214 g, 18.6 mmol) in absolute MeOH (2.5 mL). The
reaction mixture was refluxed (oil bath temperature ) 120 °C)
for 3 h under an argon atmosphere. After the reaction, EtOAc
(40 mL) was added to the reaction mixture and the insoluble
materials were filtered through Celite and washed with EtOAc.
The filtrate was washed with brine, dried over Na2SO4,
filtered, and concentrated. The residue was chromatographed
on a column of silica gel using 10:1 n-hexane/EtOAc to give
10 (0.181 g, 92%) as a white powder: mp 51-53 °C (n-hexane)
(lit.22 52-54 °C); IR (KBr) 3425, 1600, 1510, 1460, 1310, 1235
N-(Bip h en yl-4-yl)-N-(4-ch lor op h en yl)a m in e (4b). White
solid: mp 119-120 °C (n-hexane); IR (KBr) 3430, 1610, 1500
cm-1 1H NMR (CDCl3) δ 6.98-7.18 (m, 4H), 7.19-7.36 (m,
;
3H), 7.42 (t, J ) 7.5 Hz, 2H), 7.48-7.62 (m, 4H); 13C NMR
(CDCl3) δ 118.08, 119.05, 125.72, 126.54, 126.71, 128.06,
128.75, 129.32, 134.26, 140.68, 141.59, 142.04; EI-MS m/z 281
(M+ + 2, 33.5), 279 (M+, 100), 243 (11.9). Anal. Calcd for C18H14
-
NCl: C, 77.28; H, 5.04; N, 5.01. Found: C, 77.22; H, 5.03; N,
5.01.
cm-1 1H NMR (CDCl3) δ 2.53 (s, 3H), 4.00 (s, 3H), 6.74 (s,
;
1H), 7.20 (t, J ) 7.8 Hz, 1H), 7.34-7.46 (m, 2H), 7.47 (s, 1H),
8.02 (d, J ) 7.9 Hz, 1H), 8.15 (br s, 1H). EI-MS m/z 211 (M+,
100), 196 (71.7), 168 (37.5), 167 (27.0).
N-[4-(8-Br om o-6-m et h yl-9H -ca r b a zol-3-yl)p h en yl]-N-
(2-br om o-4-m eth ylp h en yl)a m in e (8). Colorless crystals:
mp 167-168 °C (EtOAc/n-hexane); IR (KBr) 3430, 2920, 1610,
1530, 1330 cm-1; 1H NMR (CDCl3) δ 2.28 (s, 3H), 2.51 (s, 3H),
5.98 (br s, 1H), 7.02 (d, J ) 8.3 Hz, 1H), 7.13-7.28 (m, 3H),
7.34-7.42 (m, 2H), 7.48 (d, J ) 8.3 Hz, 1H), 7.57-7.68 (m,
3H), 7.83 (s, 1H), 8.14 (s, 1H), 8.17 (s, 1H); 13C NMR (CDCl3)
N-(4-Br om op h en yl)-N-(2,5-d im eth ylp h en yl)a m in e (11).
Pale yellow oil: IR (neat) 3400, 1590, 1490, 1320 cm-1 1H
;
NMR (CDCl3) δ 2.19 (s, 3H), 2.27 (s, 3H), 5.31 (br s, 1H), 6.74-
6.82 (m, 3H), 7.01 (s, 1H), 7.09 (d, J ) 7.7 Hz, 1H), 7.31 (d, J
) 8.8 Hz, 1H); 13C NMR (CDCl3) δ 17.40, 21.70, 111.75, 118.41,
120.53, 123.66, 126.17, 130.86, 132.05, 136.56, 140.21, 143.52;
EI-MS m/z 277 (M+ + 2, 98.5), 275 (M+, 100), 194 (27.9), 181
(16) Bonesi, S. M.; Erra-Balsells, R. J . Heterocycl. Chem. 1997, 34,
877.
(17) Rosa, M. D.; P., A. Q.; Dodsworth, D. J . J . Org. Chem. 1987,
52, 173.
(23.2); HR-MS m/z for
C14H14NBr calcd 275.0307, found
275.0310.
(18) Barclay, B. M.; Campbell, N. J . Chem. Soc. 1945, 530.
(19) Kuroki, M.; Tsunashima, Y. J . Heterocycl. Chem. 1981, 18, 709.
(20) Piccard, J . J . Am. Chem. Soc. 1926, 48, 2878.
(21) Tabka, T.; Letois, B.; Lancelot, J .-C.; Gauduchon, P.; Heron,
J .-F.; Le Talaer, J .-Y.; Rault, S.; Robba, M. Eur. J . Med. Chem. 1989,
24, 605.
J O016124R
(22) Fukukawa, H.; Wu, T.-S.; Ohta, T.; Kuoh, C.-S. Chem. Pharm.
Bull. 1985, 33, 4132.