2-Alkyl-1,2,3,4-benzotetrazinium tetrafluoroborates: Their reaction with nucleophiles

Article abstract of DOI:10.1002/ejoc.200400588

Treatment of 2-alkyl-1,2,3,4-benzotetrazinium tetrafluoroborates with a nucleophile (AlkO^-, ArO^-, AcO^-, Hal ^-, CN^-, NCO^-, ArNH₂, Alk ₂NH), Alk₂NH), at room temperature, results in elimination of an N₂ molecule to afford ortho-substituted azobenzenes. This reaction could be suitable for mild phenylation of carboxylic acids and other compounds containing active hydrogen. A plausible reaction pathway for the reaction is discussed. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.

Full text of DOI:10.1002/ejoc.200400588

FULL PAPER
2
-Alkyl-1,2,3,4-benzotetrazinium Tetrafluoroborates: Their Reaction with
Nucleophiles
[
a]
[a]
[a]
[a]
Dmitry L. Lipilin, Oleg Y. Smirnov, Aleksandr M. Churakov,* Yuri A. Strelenko,
[a]
[a]
[a]
Aleksei Y. Tyurin, Sema L. Ioffe, and Vladimir A. Tartakovsky
Keywords: Azo compounds / Nitrogen heterocycles / Fused-ring systems / Aromatic substitution
Treatment of 2-alkyl-1,2,3,4-benzotetrazinium tetrafluoro- phenylation of carboxylic acids and other compounds con-
−
−
−
−
−
borates with a nucleophile (AlkO , ArO , AcO , Hal , CN ,
taining active hydrogen. A plausible reaction pathway for the
reaction is discussed.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
−
NCO , ArNH
2
, AlkNH
2
, Alk
2
NH), at room temperature, re-
molecule to afford ortho-substi-
sults in elimination of an N
2
tuted azobenzenes. This reaction could be suitable for mild Germany, 2004)
Introduction
NMR spectroscopic studies demonstrated that this equi-
librium is fast on the NMR timescale, and only one set of
1
13
signals is observed in the H and C NMR spectra even at
low temperatures (220 K). The equilibrium depends on the
nitrogen substituents R and the benzene-ring substituents
X. Herein, the reactions of nucleophiles with five typical
salts 1Ϫ5 have been investigated. The TS/DS ratios of these
Aromatic 1,2,3,4-tetrazines are represented in the litera-
ture only by annulated compounds, especially triazolo-an-
[1]
[2]
nulated 1,2,3,4-tetrazine and benzo-annulated 1,2,3,4-
1
[3]
tetrazine N -oxides. The question of ring-chain tautomer-
ism is of considerable importance in the chemistry of these
[
5]
[6]
[
4]
salts are shown in Table 1. The salts 6 and 7, both of
which exist only in the open-ring form, were also studied in
order to underline the difference in reactivity between the
DS and TS forms.
compounds. It has been disclosed recently that diazonium
salts DS, which were synthesized by diazotization of ortho-
(
1
2-alkylazo)anilines, exist in equilibrium with 2-alkyl-
,2,3,4-benzotetrazinium salts TS (Table 1).[
5]
Table 1. The percentage ratio of the ring-chain tautomers TS/DS
at 297 K
Results and Discussion
The reaction of salts 1Ϫ5 with nucleophiles could, a
priori, proceed in two main directions: a nucleophile could
attack the open-chain form of the salt at the terminal nitro-
gen atom of the diazonium ion, or the cyclic form could be
attacked at the carbon atom of the benzene ring.
Compound
R
X
TS/DS
[
[
[
[
[
a]
a]
b]
b]
a]
1
2
3
4
5
tBu
tBu
Me
Me
tBu
H
4,6-Br
H
4,6-Br
5-Br
50:50
100:0
ca. 60:40
ca. 95:5
85:15
2
2
O-Nucleophiles
Regardless of the TS/DS ratio, salts 1, 2, and 5 readily
react at room temperature with water, sodium methoxide,
sodium acetate, or sodium phenoxide, with evolution of ni-
[
a]
a]
In acetone solution. [b] In acetonitrile solution.
[
N. D. Zelinsky Institute of Organic Chemistry, Russian trogen, to afford compounds 8aϪh (Table 2). The open-ring
Academy of Sciences,
diazonium salts 6 and 7 do not give the products of N2
4
7 Leninsky prosp., 119991 Moscow, Russian Federation
replacement upon reaction with the above-mentioned nucle-
Fax: (internat.) ϩ 7-095-135-5328
[
7]
E-mail: churakov@ioc.ac.ru
ophiles under the same conditions. Such a high reactivity
4794
© 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
DOI: 10.1002/ejoc.200400588
Eur. J. Org. Chem. 2004, 4794Ϫ4801

2-Alkyl-1,2,3,4-benzotetrazinium Tetrafluoroborates
FULL PAPER
of salts 1Ϫ5 as compared with ordinary aryldiazonium afford the triazole derivatives 11 and 12, respectively
[
8]
salts could be due to the fact that the electrophilicity of (Scheme 1). For the salt 7, this reaction was described by
[
6]
the C-1 atom in benzotetrazinium salts TS is much higher Katritzky and coworkers already in 1964.
than that of the C-1 atom in aryldiazonium salts DS.
Table 2. Reaction of salts 1Ϫ5 with O-nucleophiles, halogen anions,
and the cyanide ion
Starting
salt
Reagent[a]
Time
[min]
Product
Nu
Yield
(%)
Scheme 1
[
[
[
b]
b]
b]
1
2
5
1
2
1
2
2
1
2
2
2
2
1
2
3
4
H
H
H
2
2
2
O
O
O
30
10
15
5
5
15
5
8a
8b
OH
OH
OH
OMe
OMe
OAc
OAc
OPh
Br
Cl
Br
Br
F
72
79
80
73
92
84
82
89
40
43
52
64
89
62
65
68
70
8c
[
[
c] [d]
c] [d]
MeON
MeON
AcONa
AcONa
PhONa
NBr
NaCl
8d
Isocyanate Anion
8e
[
[
c] [e]
c] [e]
8f
8g
The reaction of salts 1 and 2 with NaOCN resulted in
[
c] [e]
5
8h
1
,2,4-triazine derivatives 13a,b by the intermediate forma-
[
e] [f]
Bu
4
40
60
30
10
30
45
10
30
10
9a
[11]
tion of the aryl isocyanates (Scheme 2). Ordinary aryldi-
azonium salts afforded aryl isocyanates only when the reac-
tion with NaOCN was performed in the presence of copper
[
f] [g]
f] [g]
9b
[
NaBr
9c
[
e] [f]
Bu
Bu
4
NBr
NF
NaCN
NaCN
NaCN
NaCN
9c
[
e] [f]
[12]
4
9d
or copper salts.
[
e] [f]
e] [f]
e] [f]
e] [f]
10a
10b
10c
10d
CN
CN
CN
CN
[
[
[
[
a]
[b]
[c]
[d]
2
At 20 °C. 20 % H O in MeCN. 1 equiv. of reagent. Sol-
[
e]
[f]
[g]
vent: MeOH. Solvent: MeCN. 5 equiv. of reagent. Solvent:
acetone.
؊
؊
؊
Halogen Anions (F , Cl , Br )
The reaction of salts 1 and 2 with halogen anions also Scheme 2
proceeded with evolution of nitrogen. The reaction of salt 1
with NaBr proceeded very slowly in acetone or acetonitrile
The cyclic structure of 1,2,4-triazolones 13a,b was con-
solution to give 9a, whereas the more reactive salt 2 easily
afforded compounds 9b and 9c upon reaction with NaCl
and NaBr, respectively (Table 2). The reactions of salts 1
firmed by the lack of an absorption band due to the isocy-
Ϫ1
anate group in the 2000Ϫ2200 cm region of the IR spec-
tra, the typical high-field signal of the nitrogen atom con-
and 2 with Bu NBr are faster than with NaBr. The reaction
15
4
nected to a tert-butyl group in the N NMR spectrum
of salt 2 with NaF failed due to the low solubility of the
[13]
(
13a: δ ϭ Ϫ138.0 ppm for N-2), and the low-field signal
N
latter. However, with Bu NF the replacement of nitrogen
1
13
4
of the tert-butyl group in the H and C NMR spectra
proceeded easily to afford 9d. The diazonium salts 6 and 7,
[
13a: δH ϭ 1.81 and δ ϭ 69.1 (CMe )].
C 3
as well as the ordinary aryldiazonium salts,[
9,10]
failed to
react with Bu NBr or with Bu NF under these reaction
4
4
conditions.
Amines
Cyanide Ion
The reactions of salts 1Ϫ5 with amines depend on the
The reaction of salts 1Ϫ4 with NaCN also proceeded nature of the salt and the amine. The open-chain pyridodia-
with the evolution of nitrogen to give products 10aϪd zonium salt 6 reacts with morpholine, as expected, to afford
(Table 2). The diazonium salts 6 and 7 react as ordinary triazene 14. Salt 1, containing about 50 % of the ring form,
aryldiazonium salts — the cyanide ion attacks the terminal reacts similarly to afford only triazene 15 (Scheme 3). Evol-
atoms of the diazonium ions, and subsequent cyclizations ution of N was not observed in this case.
2
Eur. J. Org. Chem. 2004, 4794Ϫ4801
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A. M. Churakov et al.
FULL PAPER
hindered tBuNH resulted in the products of both types,
2
with a 20c/21a ratio of about 3:4.
Table 4. Reaction of 2 with aliphatic amines
Scheme 3
Interaction of the more reactive salt 2 with amines was Amine[a] R and R
more complicated. Aromatic amines 16aϪe replaced the N2
1
2
Time
[min]
Product
Yield
(%)
molecule to afford compounds 17aϪe (Table 3). The reac-
1
2
1
1
1
9a
9b
9c
R ϭ R ϭ Pr
30
30
30
20a
20b
20c
21a
21b
21c
21d
21e
65
75
35
44
60
81
75
76
tion took place not only with the parent aniline, but also
with substituted anilines bearing electron-withdrawing
groups. For example, 4-chloroaniline (16b) and 2,4-di-
chloroaniline (16c) gave compounds 17b and 17c, respec- 19d
tively.
1
2
R ϭ R ϭ iPr
1
2
R ϭ tBu, R ϭ H
1
2
R ϭ Me, R ϭ H
10
20
15
15
1
2
19e
19f
19g
R ϭ iPr, R ϭ H
1
2
R ϭ R ϭ Me
1
2
R R N ϭ morpholino
Table 3. Reaction of salt 2 with anilines
[a]
Reagents and conditions: 5 equiv. of amine, CH
2
Cl
2
, 20 °C.
The formation of compounds of type 21 can be rational-
ized by proposing that the amine initially attacks salt 2 at
the C-5 position of the benzene ring to give intermediate 22
(Scheme 4). This compound was observed in solution when
salt 2 was treated with 2 equiv. of morpholine; its structure
was confirmed by NMR spectroscopy. The C-5 signal of 22
appears in the aliphatic region at δ ϭ 73.3 ppm
C
1
1
13
[
J( H, C) ϭ 144.3 Hz], and the signal of the nitrogen
Aniline[a]
R
Time
min]
Yield of
17aϪe (%)
Yield of
18 (%)
atom connected to the tert-butyl group appears at δN
ϭ
[
Ϫ135.4 ppm in the 15N NMR spectrum, as expected. Un-
fortunately, we failed to isolate 22 in a pure state due to its
decomposition upon concentrating the solution.
16a
16b
16c
16d
16e
H
10
15
30
10
5
17a: 97
17b: 66
17c: 49
17d: 42
17e: 0
0
0
0
11
65
[
b]
4-Cl
2,4-Cl
4-Me
2
4-OMe
[
a]
2 2
equiv. of anilines 16, CH Cl
, 20 °C. [b] 2 equiv. of aniline 16b.
5
With anilines bearing electron-releasing substituents, for
example p-toluidine (16d), the reaction of salt 2 proceeds in
two directions. The first one is reduction to give compound
18 and the second one is substitution to give 17d. With p-
anisidine (16e), only reduction took place. It is likely that
the first stage of the reduction involves electron transfer
from the amine to the tetrazinium salt, followed by elimin-
ation of N2.
Scheme 4
The reaction of salt 2 with aliphatic sterically hindered
When a CCl solution of 22 (0.023 mmol/mL) was al-
4
secondary amines such as Pr NH and iPr NH resulted in lowed to stand at 20 °C for 30 min, 21e was obtained in
2
2
the substitution of N to give products 20a and 20b, respec- 44 % yield (Scheme 4) along with other, tarry products.
2
tively (Table 4). The reaction with primary amines
The conversion of 22 to 21e proceeded rapidly, with high
(
MeNH , iPrNH ) and secondary amines (Me NH, morph- yield, when an excess of morpholine or another organic
2
2
2
oline) afforded products of type 21. The latter were readily base was added (e.g., Et N or tBuNH ). It is likely that a
3
2
distinguished from isomers 20 by NMR spectroscopy due base is required for transfer of the proton from C-5 to nitro-
to their symmetrical structure. The reaction with sterically gen to give the intermediate 23, which could readily ring-
4796
© 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Eur. J. Org. Chem. 2004, 4794Ϫ4801

2-Alkyl-1,2,3,4-benzotetrazinium Tetrafluoroborates
FULL PAPER
open to afford the azo compound 24, followed by evolution 4,6-Dibromo-2-(tert-butylazo)benzenediazonium Tetrafluoroborate
(2):[
5,16] 1
[
14]
6 3
H NMR at 297 K ([D ]acetone): δ ϭ 2.16 (s, 9 H, 3 CH ,
of nitrogen.
tBu), 9.44 (d, J ϭ 2.1 Hz, 1 H, 3-H), 9.56 (d, J ϭ 2.1 Hz, 1 H, 5-
H) ppm. C NMR at 297 K ([D
It is interesting to note that salt 5, bearing a bromine
atom in the 5-position of the benzene ring, reacts with iso-
propylamine, with the evolution of nitrogen, to give 25, but
the bromine atom is not replaced (Scheme 5). The hydroly-
sis of salt 5 also proceeds with the evolution of nitrogen to
afford 8c (see Table 2).
1
3
6
3
]acetone): δ ϭ 29.4 (CH ), 82.9
(
(
CMe
C-1), 152.0 (C-5) ppm. The H and C signals remained un-
3
), 126.4 (C-2), 132.8 (C-3), 135.0 (C-6), 139.6 (C-4), 141.1
1
13
changed when cooling the sample to 263 K.
4
,6-Dibromo-2-(methylazo)benzenediazonium
Tetrafluoroborate
H NMR at 297 K (at, 273 K in parentheses) (CD CN):
δ ϭ 5.25 (5.30) (s, 3 H, CH ), 9.01 (9.05) (d, J ϭ 1.5 Hz, 1 H, 3-
H), 9.25 (9.29) (d, J ϭ 1.5 Hz, 1 H, 5-H) ppm. C NMR at 297 K
4):[
5,16] 1
(
3
3
1
3
(
(
(
at 263 K in parentheses) (CD
3 3
CN): δ ϭ 56.1 (56.0) (CH ), 127.0
126.8) (C-2), 132.4 (132.5) (C-3), 140.8 (141.0) (C-4), 152.8 (153.3)
1
3
C-5) ppm. The C NMR signals remained unchanged when cool-
ing the sample from 263 to 253 K.
Scheme 5
2-[(tert-Butyl)azo]phenol (8a): A solution of salt 1 (200 mg,
3 2
0.73 mmol) in 10 mL of CH CN and 2 mL of H O was stirred at
room temperature for 30 min. The solvents were then removed in
vacuo. The residue was purified by chromatography (silica gel; ben-
zene) to yield 93 mg (72 %) of 8a as a yellow oil. IR (KBr): ν˜ ϭ
4
The closely related 1,2,3,4-benzotetrazinium N -oxide 26
[
3]
[15]
reacts with water or primary amines in another way —
replacement of bromine to give the quinoid structures 27
Ϫ1 1
3590 (OH) cm . H NMR (300 MHz, CDCl
3
): δ ϭ 1.35 (s, 9 H,
(Scheme 6).
3 CH , tBu), 6.96 (m, 2 H, 4-H and 6-H), 7.23 (dt, J ϭ 7.2, 1.7 Hz,
3
1
H, 5-H), 7.82 (dd, J ϭ 8.0, 1.7 Hz, 1 H, 3-H), 12.7 (s, 1 H, OH)
1
3
ppm. C NMR (75 MHz, CDCl
3
): δ ϭ 27.1 (CH
17.9 (ddd, J ϭ 158.3, 11.8, 4.6 Hz, C-6), 119.1 (dddd, J ϭ 161.1,
1.1, 5.1, 4.2 Hz, C-4), 132.1 (dddd, J ϭ 160.3, 10.0, 6.0, 4.8 Hz,
3 3
), 66.8 (CMe ),
1
1
C-5), 132.4 (ddd, J ϭ 156.1, 10.4, 6.6 Hz, C-3), 135.9 (br.s, C-2),
ϩ
1
52.5 (dd, J ϭ 11.2, 5.6 Hz, C-1) ppm. MS (70 eV), m/z: 178 [M ].
10 14 2
C H N
O (178.23): calcd. C 67.39, H 7.92, N 15.72; found C
67.45, H 7.93, N 15.60.
Scheme 6
2,4-Dibromo-6-[(tert-butyl)azo]phenol (8b): The reaction of salt 2
(
2
50 mg, 0.12 mmol) with water (5 mL MeCN and 1 mL of H O)
It is possible that such a great difference in the reactivities
was carried out as described above to give, after 10 min of stirring,
of the related compounds 5 and 26 is due to the higher 32 mg (79 %) of 8b as a yellow oil. IR (KBr): ν˜ ϭ 3600 (OH) cmϪ1
.
1
thermodynamic stability of the N molecule, which is liber-
3 3
H NMR (300 MHz, CDCl ): δ ϭ 1.40 (s, 9 H, 3 CH , tBu), 7.63
2
ated in the course of the reaction, as compared with the (d, J ϭ 2.7 Hz, 1 H), 7.95 (d, J ϭ 2.7 Hz, 1 H), 13.65 (s, 1 H, OH)
1
3
ppm. C NMR (75 MHz, CDCl
1
(
3 3 3
): δ ϭ 27.1 (CH ), 67.6 (CMe ),
N O molecule; this results in a lower activation barrier in
case of salt 5.
In conclusion, we propose that the reaction of 2-alkyl-
2
10.3 (C-2 or C-4), 112.0 (C-4 or C-2), 134.0 (C-3 or C-5), 136.0
C-6), 137.0 (C-5 or C-3), 149.2 (C-1) ppm. N NMR/INEPT
30 MHz, CDCl ): δ ϭ 116.0 (NtBu) ppm. MS (70 eV), m/z (rel.
intensities): 334, 336, 338 (1:2:1) [M ]. C10H12Br N O (336.02):
2 2
calcd. C 35.74, H 3.60, Br 47.56, N 8.34; found C 35.78, H 3.59,
Br 47.42, N 8.28.
1
5
(
3
1,2,3,4-benzotetrazinium salts with nucleophiles could be
ϩ
suitable for mild phenylation of carboxylic acids and other
compounds containing active hydrogen. The products of
this reaction could also serve as precursors for annulated
heterocycles.
5
(
-Bromo-2-[(tert-butyl)azo]phenol (8c): The reaction of salt 5
43 mg, 0.12 mmol) with water (5 mL MeCN and 1 mL of H O)
was carried out as described above to give, after 15 min of stirring
and chromatographic purification (silica gel; CHCl ), 25 mg (80 %)
of 8c as an orange oil. IR (KBr): ν˜ ϭ 3610 (OH) cm . H NMR
300 MHz, CDCl ): δ ϭ 1.35 (s, 9 H, 3 CH , tBu), 7.14 (dd, J ϭ
.2, 1.8 Hz, 1 H, 4-H), 7.18 (d, J ϭ 1.8 Hz, 1 H, 6-H), 7.75 (d, J ϭ
2
3
Experimental Section
Ϫ1
1
(
3
3
General Remarks: Mass spectra were recorded at 70 eV using the
electron-impact technique. Melting points were determined with a
Kofler apparatus and are uncorrected. NMR spectra were recorded
8
8
1
3
.2 Hz, 1 H, 3-H), 12.4 (s, 1 H, OH) ppm. C NMR (75 MHz,
): δ ϭ 26.8 (CH ), 67.8 (CMe ), 121.1 (C-6), 122.7 (C-4),
26.0 (C-5), 134.6 (C-3), 135.1 (C-2), 155.8 (C-1) ppm. MS (70 eV),
CDCl
3
3
3
1
with an AM 300 Bruker spectrometer (300.13 MHz for H,
1
14
15
7
5.47 MHz for 13C, 21.69 MHz for N, and 30.42 MHz for N);
ϩ
2
m/z (rel. intensities): 256, 258 (1:1) [M ]. C10H13BrN O (257.13):
calcd. C 46.71, H 5.10, Br 31.08, N 10.89; found C 46.63, H 5.09,
Br 31.01, N 10.79.
chemical shifts are quoted in δ units downfield from internal TMS
1
13
14
15
(
H, C) or external CH
3
NO
2
( N, N). Negative values of δ
N
1
13
correspond to upfield shifts. The assignments of the H and
C
NMR signals were made by experiments without proton decoup-
1-(tert-Butyl)-2-(2-methoxyphenyl)diazene (8d): A solution of so-
ling (for 8a, 8e, 8, 18, 21e, 22) and CH COSY (8a, 8c, 8d, 8f, 8h, dium methoxide in CH
3
OH (1.0 mL of 1.15 mmol/mL solution,
13a, 17a), HH COSY (8f), SPT (8d, 8f, 8, 9a, 9c, 9d, 10a, 10b, 21b), 1.15 mmol) was added to a stirred solution of salt 1 (300 mg,
NOE-difference (8d), and selective decoupling experiments (8e, 8,
1.08 mmol) in 5 mL of dry CH
3
OH. After 5 min of stirring at room
13b).
temperature, the solvent was evaporated in vacuo and the residue
Eur. J. Org. Chem. 2004, 4794Ϫ4801
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A. M. Churakov et al.
FULL PAPER
chromatographed (silica gel; CHCl
as an orange oil. H NMR (300 MHz, CDCl
3
) to yield 150 mg (73 %) of 8d
): δ ϭ 1.36 (s, 9 H, 3
), 6.92 (d, J ϭ 7.9 Hz, 3-H), 6.95 (t,
J ϭ 7.9 Hz, 5-H), 7.23 (dd, J ϭ 7.9, 1.7 Hz, 6-H), 7.30 (dt, J ϭ 8.2 Hz, 1 H, H
.9, 1.7 Hz, 4-H) ppm. 13C NMR (75 MHz, CDCl
): δ ϭ 26.7 (d, J ϭ 2.1 Hz, 1 H, 6-H), 7.81 (d, J ϭ 2.1 Hz, 1 H, 4-H) ppm.
CH ), 56.2 (OMe), 68.0 (CMe ), 112.5 (C-3), 117.2 (C-6), 120.6 NMR (75 MHz, CDCl ): δ ϭ 26.5 (CH ), 69.4 (CMe ), 115.7 (C
C-5), 130.7 (C-4), 142.3 (C-1), 155.3 (C-2) ppm. N NMR/INEPT Ph), 118.6 (C-3), 119.2 (C-5), 120.2 (C-6), 122.2 (C , Ph), 129.4
30 MHz, CDCl ): δ ϭ 120.3 (NAr), 168.4 (NtBu) ppm. MS (C , Ph), 136.4 (C-4), 158.9 ppm. MS (70 eV), m/z (rel. intensities):
70 eV), m/z: 192 [M ]. C11
by chromatography (silica gel; benzene) to yield 45 mg (89 %) of
1
1
3
8h as a yellow oil. H NMR (300 MHz, CDCl
3
): δ ϭ 1.05 (s, 9 H,
, C ), 6.96 (t, J ϭ
), 7.20 (t, J ϭ 7.4 Hz, 2 H, H , C ), 7.40
CH
3
, tBu), 3.69 (s, 3 H, CH
3
3 CH
3
, tBu), 6.79 (d, J ϭ 8.1 Hz, 2 H, H
, C
o
6 5
H
p
6
H
5
m
6 5
H
13
7
3
C
(
(
(
(
3
3
3
3
3
o
,
15
p
3
m
ϩ
ϩ
H
16
N
2
O (192.26): calcd. C 68.72, H
410, 412, 414 (1:2:1) [M ]. C16
H16Br
2
N
2
O (412.12): calcd. C 46.63,
8.39, N 14.57; found C 68.56, H 8.36, N 14.62.
H 3.91, Br 38.78, N 6.80; found C 46.68, H 3.91, Br 38.71, N 6.75.
1
-(tert-Butyl)-2-(3,5-dibromo-2-methoxyphenyl)diazene (8e): The re-
Attempt to Hydrolyse 2-(Phenylazo)phenyldiazonium Tetrafluorobo-
rate 7. Experiment 1: A solution of salt 7 (50 mg, 0.17 mmol) in
7 mL of CH CN and 1.5 mL of H O was stirred at room tempera-
action of salt 2 (50 mg, 0.12 mmol) with sodium methoxide was
carried out as described above to give, after chromatographic puri-
3
2
fication (silica gel; benzene), 39 mg (92 %) of 8e as an orange oil.
H NMR (300 MHz, CDCl ): δ ϭ 1.36 (s, 9 H, 3 CH , tBu), 4.01 with Et O to give 48 mg (96 %) of unchanged salt 7. Experiment 2:
3 3
2
ture for 24 h. The solvent was evaporated and the residue washed
1
(
1
6
s, 3 H, OMe), 7.43 (d, J ϭ 2.3 Hz, 1 H, 6-H), 7.79 (d, J ϭ 2.3 Hz, A solution of NaOH (34 mg, 0.85 mmol) in 1.5 mL of H O was
2
H, 4-H) ppm. 13C NMR (75 MHz, CDCl
9.6 (CMe
3 3
): δ ϭ 63.4 (OCH ), added to a solution of salt 7 (50 mg, 0.17 mmol) in 7 mL of
3
), 116.9 (t, J ϭ 4.3 Hz, C-5), 119.4 (dd, J ϭ 4.3, 1.5 Hz, CH CN. After 30 min of reflux, the solvent was evaporated. The
3
C-3), 120.6 (dd, J ϭ 170.3, 6.4 Hz, C-6), 136.7 (dd, J ϭ 172.8,
residue was purified by chromatography (silica gel; benzene) to give
1
5
6
.8 Hz, C-4), 146.9 (t, J ϭ 2.2 Hz, C-1), 154.0 (m, C-2) ppm.
N
30 mg (90 %) of 2-(phenylazo)phenol as an orange solid, m.p.
): δ ϭ 186.0 (NtBu) ppm. MS 82Ϫ84 °C (ref.[ m.p. 82.5Ϫ83 °C).
17]
NMR/INEPT (30 MHz, CDCl
3
ϩ
(70 eV), m/z (rel. intensities): 348, 350, 352 (1:2:1) [M ].
Reactions of 2-Alkyl-1,2,3,4-benzotetrazinium Tetrafluoroborates
؊4 with Halide and Cyanide Ions. General Procedure: The appro-
11 2 2
C H14Br N O (350.05): calcd. C 37.74, H 4.03, Br 45.65, N 8.00;
found C 37.79, H 4.01, Br 45.72, N 7.94.
1
priate reagent (0.6 mmol) was added to a stirred solution contain-
General Procedure for the Reaction of Salts 1 and 2 with NaOAc:
NaOAc was added at room temperature to a stirred solution of
ing 0.12 mmol of salts 1Ϫ4 in 5 mL of dry CH CN or acetone (see
3
Table 2). After the reaction had reached completion (TLC control),
0.54 mmol of salt 1 or 2 in 5 mL of dry CH
3
CN, (45 mg,
the precipitate of inorganic salts was filtered off and the solvent
evaporated. The residue was purified by chromatography [silica gel;
hexane (for 10d: hexane/EtOAc, 7:1)] to afford 9aϪd and 10aϪd
(see Table 2).
0.54 mmol). After the reaction had reached completion (TLC con-
trol), the solution was concentrated to dryness and extracted with
hexane. The solvent was removed in vacuo and the residue was
purified by chromatography (silica gel, CHCl
3
).
1
1
-(2-Bromophenyl)-2-(tert-butyl)diazene (9a): Orange oil. H NMR
2-[(tert-Butyl)azo]phenyl Acetate (8f): According to the general pro-
(300 MHz, CDCl
3
): δ ϭ 1.39 (s, 9 H, 3 CH
3
, tBu), 7.24 (m, 2 H,
cedure salt 1, after 15 min of stirring, gave 110 mg (84 %) of 8f as
3
6
-H and 5-H), 7.31 (dt, J ϭ 6.8, 1.6 Hz, 1 H, 4-H), 7.66 (dd, J ϭ
Ϫ1
1
an orange oil. IR (KBr): ν˜ ϭ 1760 (CϭO) cm
300 MHz, CDCl ): δ ϭ 1.31 (s, 9 H, 3 CH , tBu), 2.29 (s, 3 H,
COCH ), 7.15 (dd, J ϭ 8.0, 1.7 Hz, 1 H, 6-H), 7.25 (dt, J ϭ 7.8,
.7 Hz, 1 H, 5-H), 7.38 (dt, J ϭ 8.0, 1.7 Hz, 1 H, 4-H), 7.48 (dd,
.
H NMR
13
.7, 1.6 Hz, 1 H, 6-H) ppm. C NMR (75 MHz, CDCl
), 69.1 (CMe ), 118.0 (C-6), 123.8 (C-2), 127.6 (C-5), 130.7
C-4), 133.2 (C-3), 149.8 (C-1) ppm. MS (70 eV), m/z (rel. intensit-
3
): δ ϭ 27.0
(
3
3
(CH
3
3
3
(
1
ϩ
ies): 240, 242 (1:1) [M ]. C10
H13BrN
2
(241.13): calcd. C 49.81, H
13
J ϭ 7.8, 1.7 Hz, 1 H, 3-H) ppm. C NMR (75 MHz, CDCl
3
): δ ϭ
), 117.6 (C-3), 122.8 (C-6),
26.5 (C-5), 131.0 (C-4), 143.3 (C-2), 147.9 (C-1), 169.2 (COCH
5.43, Br 33.14, N 11.62; found C 49.75, H 5.43, Br 33.22, N 11.67.
3 3 3
20.5 (COCH ), 26.9 (CH ), 68.5 (CMe
1
-(3,5-Dibromo-2-chlorophenyl)-2-(tert-butyl)diazene (9b): Orange
1
3
)
1
15
3 3
oil. H NMR (300 MHz, CDCl ): δ ϭ 1.34 (s, 9 H, 3 CH , tBu),
ppm. N NMR/INEPT (30 MHz, CDCl
3
ϩ
): δ ϭ 116.0 (NAr), 174.0
7.34 (d, J ϭ 2.1 Hz, 1 H, 6-H), 7.81 (d, J ϭ 2.1 Hz, 1 H, 4-H) ppm.
(NtBu) ppm. MS (70 eV), m/z: 220 [M ]. C12
16 2 2
H N O (220.27):
ϩ
MS (70 eV), m/z (rel. intensities): 352, 354, 356, 358 (2:5:4:1) [M ].
calcd. C 65.43, H 7.32, N 12.72; found C 65.48, H 7.34, N 12.59.
C
10
H11Br
2
ClN
2
(354.47): calcd. C 33.88, H 3.13, Br 45.08, Cl 10.00,
2,4-Dibromo-6-[(tert-butyl)azo]phenyl Acetate (8): According to the
N 7.90; found C 33.93, H 3.13, BrϩCl 55.16, N 7.79.
general procedure salt 2, after 5 min of stirring, gave 180 mg (82 %)
of 8 as a yellow oil. IR (KBr): ν˜ ϭ 1750 (CϭO) cmϪ1. H NMR 1-(2,3,5-Tribromophenyl)-2-(tert-butyl)diazene (9c): Orange oil. H
300 MHz, [D ]acetone): δ ϭ 1.30 (s, 9 H, 3 CH
, tBu), 2.35 (s, 3 NMR (300 MHz, CDCl ): δ ϭ 1.38 (s, 9 H, 3 CH , tBu), 7.28 (d,
H, COCH
), 7.56 (d, J ϭ 2.3 Hz, 1 H, 5-H), 7.90 (d, J ϭ 2.3 Hz, J ϭ 2.2 Hz, 1 H, 6-H), 7.80 (d, J ϭ 2.2 Hz, 1 H, 4-H) ppm.
H, 3-H) ppm. 13C NMR (75 MHz, [D
]acetone): δ ϭ 20.1
NMR (75 MHz, CDCl ): δ ϭ 29.7 (CH ), 69.8 (CMe ), 120.0 (C-
COCH ), 26.6 (CH ), 69.7 (CMe
), 118.8 (dd, J ϭ 4.0, 1.5 Hz, C- 6), 124.3 (C-2), 126.9 (C-5), 135.9 (C-4), 137.2 (C-3), 158.6 (C-
), 119.9 (t, J ϭ 4.4 Hz, C-4), 120.3 (dd, J ϭ 172.0, 6.5 Hz, C-5), 1) ppm. MS (70 eV), m/z (rel. intensities): 395, 397, 399, 401, 403
1
1
(
6
3
3
3
1
3
C
3
1
6
3
3
3
(
3
3
3
2
1
8
ϩ
36.6 (dd, J ϭ 174.0, 6.8 Hz, C-3), 145.7 (s, C-6), 145.8 (t, J ϭ
) ppm. 15N NMR/IN- 60.09, N 7.02; found C 30.01, H 2.77, Br 60.01, N 6.99.
.0 Hz, C-1), 167.7 (q, J ϭ 7.0 Hz, COCH
]acetone): δ ϭ 113.2 (NAr), 185.6 (NtBu) ppm.
3 2
(1:3:5:3:1) [M ]. C10H11Br N (398.92): calcd. C 30.11, H 2.78, Br
3
EPT (30 MHz, [D
MS (70 eV), m/z (rel. intensities): 376, 378, 380 (1:2:1) [M ].
(378.06): calcd. C 38.12, H 3.73, Br 42.27, N 7.41;
found C 38.05, H 3.74, Br 42.37, N 7.29.
6
1
-(3,5-Dibromo-2-fluorophenyl)-2-(tert-butyl)diazene (9d): Orange
ϩ
1
oil. H NMR (300 MHz, CDCl
3
): δ ϭ 1.36 (s, 9 H, 3 CH
3
, tBu),
12 2 2 2
C H14Br N O
7
4
.48 (d, J ϭ 6.4, 2.1 Hz, 1 H, 6-H), 7.73 (d, J ϭ 5.9, 2.1 Hz, 1 H,
1
3
-H) ppm. C NMR (75 MHz, CDCl
), 111.2 (C-3, J13 ϭ 21.1 Hz), 117.1 (C-5, J13
4.7 Hz), 120.1 (C-6, J13 ϭ 7.1 Hz), 136.3 (C-4, J13
ϭ 7.2 Hz),
141.1 (C-1, J13 ϭ 10.5 Hz), 154.9 (C-2, J13
ϭ 256.8 Hz) ppm.
MS (70 eV), m/z (rel. intensities): 336, 338, 340 (1:2:1) [M ].
3 3
): δ ϭ 28.9 (CH ), 69.8
1
(
0
-(tert-Butyl)-2-(3,5-dibromo-2-phenoxyphenyl)diazene (8h): NaOPh (CMe
14 mg, 0.12 mmol) was added to a stirred solution of salt 2 (50 mg,
.12 mmol) in 5 mL of dry CH CN. After 5 min of stirring at room
temperature, the solvent was evaporated and the residue purified
3
C
19
F
C F
ϭ
19
19
19
C
F
C F
19
19
3
C
F
C F
ϩ
4798
© 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2004, 4794Ϫ4801

2-Alkyl-1,2,3,4-benzotetrazinium Tetrafluoroborates
FULL PAPER
C
10
H
11Br
2
FN
2
(338.01): calcd. C 35.53, H 3.28, Br 47.28, F 5.62,
9 H, 3 CH
3
, tBu), 7.30 (ddd, J ϭ 8.7, 6.4, 1.1 Hz, 1 H, 7-H), 7.43
1
3
N 8.29; found C 35.59, H 3.27, Br ϩ F 52.76, N 8.32.
(d, J ϭ 9.0 Hz, 1 H, 5-H), 7.68 (m, 2 H, 6-H, 8-H) ppm. C NMR
75 MHz, [D ]acetone): δ ϭ 27.4 (CH ), 69.1 (CMe ), 126.8 (dd,
J ϭ 165.0, 9.0 Hz, C-7 or C-8), 126.9 (dd, J ϭ 167.3, 9.0 Hz, C-8
(
6
3
3
2
2
3
1
-[(tert-Butyl)azo]benzonitrile (10a): Orange oil. IR (KBr): ν˜ ϭ
Ϫ1
1
270 (CN) cm . H NMR (300 MHz, CDCl
CH , tBu), 7.36Ϫ7.46 (m, 2 H, 4-H and 6-H), 7.80 (t, J ϭ 8.2 Hz,
H, 5-H), 8.04 (d, J ϭ 8.7 Hz, 1 H, 3-H) ppm. C NMR (75 MHz,
3
): δ ϭ 1.39 (s, 9 H,
3
or C-7), 129.8 (ddt, J ϭ 166.2, 7.3, 1.5 Hz, C-5), 136.1 (dd, J7-H
ϭ
3
3
1
0.7, J5-H ϭ 5.5 Hz, C-8a), 139.1 (ddd, J ϭ 161.0, 10.6, 2.0 Hz,
13
3
3
C-6), 153.6 (s, C-3), 153.7 (dd, J6 -Hϭ 10.3, J8-H ϭ 5.0 Hz, C-4a)
CDCl
3
): δ ϭ 26.6 (CH
3
), 69.8 (CMe
3
), 114.0 (CN), 115.3 (C-1),
(187.24): calcd. C 70.56, H
15
ppm. N NMR/INEPT (30 MHz, [D
6
]acetone): δ ϭ Ϫ138.0
]acetone): δ ϭ
Ϫ108.4 (d, J ϭ 1.3 Hz, N-4) ppm. N NMR (30 MHz, [D ]ace-
tone): δ ϭ Ϫ138.2 (m, N-2), Ϫ108.4 (d, J ϭ 1.3 Hz, N-4), 2.8 (d,
116.8 (C-3), 118.5 (C-6), 130.0 (C-5), 131.6 (C-4), 143.7 (C-2) ppm.
NtBu) ppm. 15N NMR/SPT from 5-H (30 MHz, [D
(
6
ϩ
MS (70 eV), m/z: 187 [M ]. C11
H
13
N
3
15
6
7.00, N 22.44; found C 70.62, H 6.98, N 22.16.
1
4
J ϭ 0.8 Hz, N-1) ppm. N NMR (21 MHz, [D
Ϫ140 (∆ν1/2 ϭ 2000 Hz) (N-2) ppm. MS (70 eV), m/z: 203 [M ].
O (203.24): calcd. C 65.01, H 6.45, N 20.68; found C
64.96, H 6.41, N 20.47.
6
]acetone): δ ϭ
2,4-Dibromo-6-[(tert-butyl)azo]benzonitrile (10b): Yellow oil. IR
ϩ
Ϫ1
1
(
KBr): ν˜ ϭ 2240 (CN) cm . H NMR (300 MHz, CDCl
.41 (s, 9 H, 3 CH , tBu), 7.62 (d, J ϭ 2.0 Hz, 1 H, 5-H), 7.89 (d,
J ϭ 2.0 Hz, 1 H, 3-H) ppm. C NMR (75 MHz, CDCl
3
): δ ϭ
11 13 3
C H N
1
3
13
3
): δ ϭ 26.8
), 113.8 (CN), 114.1 (C-1), 119.6 (C-5), 125.4
C-2), 126.6 (C-4), 136.1 (C-3), 155.0 (C-6) ppm. MS (70 eV), m/z
(
(
(
3 3
CH ), 70.7 (CMe
5
,7-Dibromo-2-(tert-butyl)-1,2,4-benzotriazin-3(2H)-one
Brown solid, m.p. 133Ϫ134 °C. IR (KBr): ν˜ ϭ 1850 (CϭO) cm
1
(13b):
Ϫ1
.
ϩ
rel. intensities): 343, 345, 347 (1:2:1) [M ]. C11
H11Br
2
N
3
(345.03):
H NMR (300 MHz, [D
6 3
]acetone): δ ϭ 1.80 (s, 9 H, 3 CH , tBu),
calcd. C 38.29, H 3.21, Br 46.32, N 12.18; found C 38.34, H 3.23,
Br 46.24, N 12.21.
8
.10 (d, J ϭ 2.0 Hz, 1 H, 8-H), 8.25 (d, J ϭ 2.0 Hz, 1 H, 6-H) ppm.
13
C NMR (75 MHz, [D
18.2 (t, J ϭ 4.7 Hz, C-7), 121.7 (dd, J ϭ 5.3, 2.1 Hz, C-5), 131.5
dd, J ϭ 174.3, 5.3 Hz, C-8), 136.0 (s, C-8a), 143.5 (dd, J ϭ 173.5,
6 3 3
]acetone): δ ϭ 27.1 (CH ), 70.2 (CMe ),
1
2
-(Methylazo)benzonitrile (10c): Orange oil. IR (KBr): ν˜ ϭ 2240
(
Ϫ1
1
(CN) cm . H NMR (300 MHz, CDCl
3 3
): δ ϭ 4.12 (s, 3 H, CH ),
3
3
7.2 Hz, C-6), 149.7 (dd, J6-H ϭ 7.7, J8-H ϭ 4.7 Hz, C-4a), 153.2
7.45 (m, 2 H, 4-H and 6-H), 7.78 (d, J ϭ 8.1 Hz, 1 H, 3-H), 8.07
1
5
(
s, C-3) ppm. N NMR/INEPT (30 MHz, [D
6
]acetone): δ ϭ
ϩ
(t, J ϭ 8.6 Hz, 1 H, 5-H) ppm. MS (70 eV), m/z: 145 [M ]. C
8 7 3
H N
Ϫ132.5 (N-2) ppm. MS (70 eV), m/z (rel. intensities): 359, 361, 363
(145.16): calcd. C 66.19, H 4.86, N 28.95; found C 66.24, H 4.85,
ϩ
(
1:2:1) [M ]. C11
2 3
H11Br N O (361.03): calcd. C 36.59, H 3.07, Br
N 29.91.
,4-Dibromo-6-(methylazo)benzonitrile (10d): Orange oil. IR (KBr):
44.26, N 11.64; found C 36.68, H 3.07, Br 44.31, N 11.52.
2
General Procedure for the Reaction of Benzotetrazinium Salts 1 and
with Morpholine: Morpholine (190 mg, 2.16 mmol) was added to
a stirred suspension of salts 1 or 6 (0.72 mmol) in 20 mL of dry
CH Cl . After the reaction reached completion (TLC control), the
solution was washed with H O and 5 % HCl. The organic layer
was dried (MgSO ) and the solvent evaporated. The residue was
purified by chromatography (silica gel; Et O) to afford compounds
Ϫ1
1
ν˜ ϭ 2260 (CN) cm . H NMR (300 MHz, CDCl
H, CH ), 7.63 (d, J ϭ 1.9 Hz, 1 H, 5-H), 7.90 (d, J ϭ 1.9 Hz, 1 H,
-H) ppm. 13C NMR (75 MHz, CDCl
): δ ϭ 57.0 (CH ), 120.1 (C-
), 136.2 (C-3) ppm. MS (70 eV), m/z (rel. intensities): 301, 303,
): δ ϭ 4.14 (s, 3
3
6
3
3
5
3
5
3
3
2
2
2
ϩ
8 5 2 3
05 (1:2:1) [M ]. C H Br N (302.95): calcd. C 31.72, H 1.66, Br
2.75, N 13.87; found C 31.75, H 1.66, Br 52.66, N 13.93.
4
2
14 or 15, respectively.
2-(tert-Butyl)-2H-[1,2,3]triazolo[4,5-b]pyridin-1-cyanoimide
(11):
NaCN (43 mg, 0.87 mmol) was added to a solution of 6 (50 mg,
.175 mmol) in 5 mL of dry CH CN. After stirring for 20 min at
room temperature, the precipitate of inorganic salts was filtered off
and the solvent evaporated. The residue was extracted with EtOAc,
4
-{[2-[(tert-Butyl)azo]-3-pyridinyl]azo}morpholine (14): According
0
3
to the general procedure, salt 6, after 15 min of stirring, gave
1
1
65 mg (92 %) of 14 as a brownish oil. H NMR (300 MHz,
CDCl ): δ ϭ 1.42 (s, 9 H, 3 CH , tBu), 3.27 (t, J ϭ 5.2 Hz, 4 H,
NCH ), 3.68 (t, J ϭ 5.2 Hz, 4 H, OCH ), 7.26 (dd, J ϭ 8.1, 4.4 Hz,
H, 5-H), 7.37 (dd, J ϭ 8.1, 1.5 Hz, 1 H, 4-H), 8.20 (dd, J ϭ 4.4,
3
3
and the organic layer washed with H
2 4
O and dried (MgSO ). The
2
2
solvent was evaporated and the residue purified by chromatography
1
1
(
silica gel; EtOAc) to give 32 mg (80 %) of 11 as a red solid, m.p.
ϩ
20 6
.5 Hz, 1 H, 6-H) ppm. MS (70 eV), m/z: 276 [M ]. C13H N O
Ϫ1
1
1
55Ϫ158 °C (decomp.). IR (KBr): ν˜ ϭ 2210 (CN) cm . H NMR
]DMSO): δ ϭ 2.11 (s, 9 H, 3 CH , tBu), 7.33 (dd,
J ϭ 8.1, 4.4 Hz, 1 H, 6-H), 7.97 (dd, J ϭ 4.4, 1.5 Hz, 1 H, 5-H),
.48 (dd, J ϭ 8.1, 1.5 Hz, 1 H, 7-H) ppm. MS (70 eV), m/z: 216
(
276.34): calcd. C 56.50, H 7.29, N 30.41; found C 56.41, H 7.30,
(
300 MHz, [D
6
3
N 30.37.
4-{[2-[(tert-Butyl)azo]phenyl]azo}morpholine (15): According to the
8
ϩ
general procedure, salt 1, after 10 min of stirring, gave 190 mg
[M ]. C10
12 6
H N (216.24): calcd. C 55.54, H 5.59, N 38.86; found
1
(
96 %) of 15 as a red oil. H NMR (300 MHz, CDCl
3
): δ ϭ 1.35
C 55.59; H 5.60; N 38.71.
(s, 9 H, 3 CH , tBu), 3.7 (br. s, 8 H, OCH , NCH ), 7.17 (m, 2 H,
3
2
2
General Procedure for the Reaction of Benzotetrazinium Salts 1 and 4-H, 6-H), 7.29 (dt, J ϭ 8.0, 2.1 Hz, 1 H, 5-H), 7.47 (d, J ϭ 8.0 Hz,
1
3
2
with Sodium Isocyanate: NaNCO (39 mg, 0.6 mmol) was added
to a stirred solution of 0.12 mmol of salt 1 or 2 in 5 mL of dry
CH CN. The stirring was continued for 5Ϫ10 min (TLC control)
3 3
1 H, 3-H) ppm. C NMR (75 MHz, CDCl ): δ ϭ 26.6 (CH ), 47.6
(br., NCH ), 65.7 (br., OCH ), 67.7 (CMe ), 116.8 (C-6), 119.0 (C-
3), 126.0 (C-4), 129.2 (C-5), 144.6 (C-1 or C-2), 145.9 (C-2 or C-1)
14 21 5
ppm. N NMR/INEPT, MS (70 eV), m/z: 275 [M ]. C H N O
(275.35): calcd. C 61.07, H 7.69, N 25.43; found C 60.98, H 7.70,
N 25.36.
2
2
3
3
1
5
ϩ
and then the precipitate of inorganic salts was filtered off and the
solvent evaporated. The residue was purified by chromatography
(silica gel; benzene) to afford 13a or 13b, respectively
2
-(tert-Butyl)-1,2,4-benzotriazin-3(2H)-one (13a): Brown solid, m.p.
General Procedure for the Reaction of Salt 2 with Amines 16a؊e
Ϫ1
1
1
10Ϫ112 °C. IR (KBr): ν˜ ϭ 1870 (CϭO) cm
]acetone): δ ϭ 1.81 (s, 9 H, 3 CH
J ϭ 9.0, 1.3 Hz, 1 H, 5-H), 7.34 (ddd, J ϭ 9.2, 6.5, 1.3 Hz, 1 H, 7-
H), 7.68 (dd, J ϭ 9.2, 1.3 Hz, 1 H, 8-H), 7.75 (ddd, J ϭ 9.0, 6.5, (TLC control, see Tables 3 and 4), the solution was passed through
.
H NMR and 19a؊g: Amine (0.6 mmol) was added dropwise to a stirred sus-
(300 MHz, [D
6
3
, tBu), 7.34 (dd,
pension of salt 2 (50 mg, 0.12 mmol) in 5 mL of dry CH
2 2
Cl at
room temperature. After the reaction had reached completion
1
1.3 Hz, 1 H, 6-H) ppm. H NMR (300 MHz, CDCl
3
): δ ϭ 1.83 (s,
a silica gel pad. The solvent was evaporated and the residue was
Eur. J. Org. Chem. 2004, 4794Ϫ4801
www.eurjoc.org
© 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4799

A. M. Churakov et al.
FULL PAPER
purified by chromatography [silica gel; benzene, or hexane, or hex-
ane/benzene (3:1)] to afford 17aϪe, 18, 20aϪc, and 21cϪe.
Reaction of Salt 2 with Anisidine (16e): According to the general
procedure, the reaction of salt 2 with 16e gave 25 mg (65 %) of 18
identical to the sample obtained above.
2,4-Dibromo-6-[(tert-butyl)azo]-N-phenylaniline (17a): According to
the general procedure, the reaction of salt 2 with aniline gave 48 mg 2,4-Dibromo-6-[(tert-butyl)azo]-N,N-dipropylaniline (20a): Accord-
Ϫ1
(
97 %) of 17a as an orange oil. IR (KBr): ν˜ ϭ 3420 (NH) cm
.
ing to the general procedure, the reaction of salt 2 with Pr NH
2
1
1
H NMR (300 MHz, CDCl
3
): δ ϭ 1.08 (s, 9 H, 3 CH
3
, tBu), 6.66 gave 33 mg (65 %) of 20a as an orange oil. H NMR (300 MHz,
(s, 1 H, NH), 6.74 (d, J ϭ 8.0 Hz, 2 H, H
o
, Ph), 6.89 (t, J ϭ 7.4 Hz, CDCl ): δ ϭ 0.85 (t, J ϭ 6.9 Hz, 6 H, 2 CH CH CH ), 1.25 (s, 9
3
2
2
3
1
H, H
p
, Ph), 7.16 (dd, J ϭ 7.4, 8.0 Hz, 2 H, H
m
, Ph), 7.43 (d, J ϭ
3 2 2 3
H, 3 CH , tBu), 1.28 (m, 4 H, 2 CH CH CH ), 3.11 (t, J ϭ 6.8 Hz,
13
2.0 Hz, 1 H, 5-H), 7.75 (d, J ϭ 2.0 Hz, 1 H, 3-H) ppm. C NMR 4 H, 2 CH CH CH ), 7.32 (d, J ϭ 2.7 Hz, 1 H, 5-H), 7.68 (d, J ϭ
2
2
3
(
(
1
(
75 MHz, CDCl
, Ph), 118.6 (C-2), 120.9 (C-5), 121.6 (C
36.2 (C-3), 144.4 [C-1 or C (Ph)], 145.1 [C
70 eV), m/z (rel. intensities): 409, 411, 413 (1:2:1) [M ].
(411.13): calcd. C 46.74, H 4.17, Br 38.87, N 10.22;
found C 46.65, H 4.15, Br 38.99, N 10.11.
3
): δ ϭ 26.5 (CH
3
), 68.9 (CMe
, Ph), 128.9 (C
(Ph) or C-1] ppm. MS
3
), 115.6 (C-4), 118.5 2.7 Hz, 1 H, 3-H) ppm. MS (70 eV), m/z (rel. intensities): 417, 419,
ϩ
C
o
p
m
16 25 2 3
, Ph), 421 (1:2:1) [M ]. C H Br N (419.20): calcd. C 45.84, H 6.01, Br
i
i
38.12, N 10.02; found C 45.90, H 6.01, Br 38.01, N 10.10.
ϩ
2,4-Dibromo-6-[(tert-butyl)azo]-N,N-diisopropylaniline (20b): Ac-
16 2 3
C H17Br N
cording to the general procedure, the reaction of salt 2 with iPr NH
2
1
gave 38 mg (75 %) of 20b as an orange oil. H NMR (300 MHz,
CDCl ): δ ϭ 1.29 (s, 9 H, 3 CH , tBu), 1.37 (d, J ϭ 7.1 Hz, 12 H,
2
,4-Dibromo-6-[(tert-butyl)azo]-N-(4-chlorophenyl)aniline (17b): Ac-
3
3
cording to the general procedure, the reaction of salt 2 with p-
chloroaniline gave 35 mg (66 %) of 17b as a yellow solid, m.p.
3 2
4 CH , 2 iPr), 4.03 (sept, J ϭ 7.1 Hz, 2 H, 2 CHMe ), 7.31 (d, J ϭ
2.7 Hz, 1 H, 5-H), 7.76 (d, J ϭ 2.7 Hz, 1 H, 3-H) ppm. MS (70 eV),
Ϫ1
1
ϩ
1
05Ϫ107 °C. IR (KBr): ν˜ ϭ 3400 (NH) cm . H NMR (300 MHz, m/z (rel. intensities): 417, 419, 421 (1:2:1) [M ]. C H Br N
16 25 2 3
CDCl
3
): δ ϭ 1.10 (s, 9 H, 3 CH
), 6,87 (br. s, 1 H, NH), 6.86 (d, J ϭ 6.7 Hz, 2 H, H
), 7.45 (d, J ϭ 2.7 Hz, 1 H, 5-H), 7.75 (d, J ϭ 2.7 Hz, 1 H,
-H) ppm. MS (70 eV), m/z (rel. intensities): 443, 445, 447, 449
3
, tBu), 6.66 (d, J ϭ 6.7 Hz, 2 H,
(419.20): calcd. C 45.84, H 6.01, Br 38.12, N 10.02; found C 45.89,
H 6.02, Br 38.19, N 9.95.
o
H , ClC
6
H
4
m
,
ClC
6
H
4
3
Reaction of Salt 2 with tBuNH
2
: According to the general pro-
gave 16 mg (35 %) of
20c as an orange oil and 21 mg (44 %) of 21a as a yellow oil.
ϩ
(2:5:4:1) [M ]. C16
H16Br
2
ClN
3
(445.58): calcd. C 43.13, H 3.62, Br cedure, the reaction of salt 2 with tBuNH
2
35.87, Cl 7.96, N 9.43; found C 43.05, H 3.60, BrϩCl 43.95, N 9.49.
2
,4-Dibromo-6-[(tert-butyl)azo]-N-(2,4-dichlorophenyl)benzenamine
2,4-Dibromo-6-[(tert-butyl)azo]-N-(tert-butyl)aniline
(20c):
(KBr): ν˜ ϭ 3380 (NH) cm . H NMR (300 MHz, CDCl
1.15 (s, 9 H, 3 CH , tBu), 1.37 (s, 9 H, 3 CH
H NMR NH), 7.38 (d, J ϭ 2.0 Hz, 1 H, 5-H), 7.72 (d, J ϭ 2.0 Hz, 1 H, 3-
, tBu), 6.38 (d, J ϭ H) ppm. MS (70 eV), m/z (rel. intensities): 389, 391, 393 (1:2:1)
3
IR
): δ ϭ
Ϫ1
1
(17c): According to the general procedure, the reaction of salt 2
3
with 2,4-dichloroaniline gave 28 mg (49 %) of 17c as a yellow solid,
3
3
, tBuN), 5.40 (s, 1 H,
Ϫ1
1
m.p. 131Ϫ133 °C. IR (KBr): ν˜ ϭ 3410 (NH) cm
300 MHz, CDCl ): δ ϭ 1.15 (s, 9 H, 3 CH
.7 Hz, 1 H, 6Ј-H, Cl
2 3
), 6.60 (d, J ϭ 2.0 Hz, 1 H, 3Ј-H, [M ]. C14H21Br N (391.14): calcd. C 42.99, H 5.41, Br 40.86, N
.
(
8
3
ϩ
2
C
6
H
3
Cl
Cl
2
C
C
6
H
H
3
), 6.88 (s, 1 H, NH), 6.96 (dd, J ϭ 8.7, 2.0 Hz, 1 H, 5Ј-H, 10.74; found C 43.07, H 5.39, Br 40.78, N 10.70.
2
6
3
), 7.33 (d, J ϭ 2.7 Hz, 1 H, 5-H), 7.51 (d, J ϭ 2.7 Hz, 1
2
,6-Dibromo-4-[(tert-butyl)azo]-N-(tert-butyl)aniline
(21a):
IR
H, 3-H) ppm. MS (70 eV), m/z (rel. intensities): 477, 479, 481, 483,
Ϫ1
1
ϩ
(KBr): ν˜ ϭ 3400 (NH) cm . H NMR (300 MHz, CDCl ): δ ϭ
4
85 (4:12:13:6:1) [M ]. C16
H15Br
2
Cl
2
N
3
(480.02): calcd. C 40.03,
3
1.31 (s, 9 H, 3 CH
3 3
, tBu), 1.40 (s, 9 H, 3 CH , tBuNH), 3.69 (s, 1
H 3.15, Br 33.29, Cl 14.77, N 8.75; found C 39.93, H 3.15, Br ϩ
Cl 48.16, N 8.66.
H, NH), 7.80 (s, 2 H, 3-H and 5-H) ppm. MS (70 eV), m/z (rel.
ϩ
2 3
intensities): 389, 391, 393 (1:2:1) [M ]. C14H21Br N (391.14):
Reaction of Salt 2 with p-Toluidine (16d): According to the general
procedure, the reaction of salt 2 with p-toluidine gave 22 mg (42 %)
of 17d as a yellow oil and 5 mg (11 %) of 18 as an orange oil.
calcd. C 42.99, H 5.41, Br 40.86, N 10.74; found C 43.03, H 5.40,
Br 40.94, N 10.62.
2
,6-Dibromo-4-[(tert-butyl)azo]-N-methylaniline (21b): According to
the general procedure, the reaction of salt 2 with MeNH gave
17d): IR (KBr): ν˜ ϭ 3410 (NH) cm
.
H NMR (300 MHz, 25 mg (60 %) of 21b as a yellow oil. IR (KBr): ν˜ ϭ 3380 (NH)
2
(
,4-Dibromo-6-[(tert-butyl)azo]-N-(4-methylphenyl)benzenamine
2
Ϫ1
1
Ϫ1
1
CDCl
3
): δ ϭ 1.08 (s, 9 H, 3 CH
3
, tBu), 2.24 (s, 3 H, CH
, MeC ), 6.97 (d,
), 7.42 (d, J ϭ 2.1 Hz, 1 H, 5-H), H) ppm. C NMR (75 MHz, CDCl
.72 (d, J ϭ 2.1 Hz, 1 H, 3-H) ppm. MS (70 eV), m/z (rel. intensit-
(NCH ), 67.3 (CMe ), 114.2 (d, J ϭ 5.4 Hz, C-2 and C-6), 127.0
(425.16): calcd. C (dd, J ϭ 168.4, 6.1 Hz, C-3 and C-5), 145.7 (t, J ϭ 3.2 Hz, C-4),
8.02, H 4.50, Br 37.59, N 9.88; found C 47.96, H 4.48, Br 37.73,
146.9 (m, C-1) ppm. MS (70 eV), m/z (rel. intensities): 347, 349,
3
), 5.90 cm . H NMR (300 MHz, CDCl
3 3
): δ ϭ 1.28 (s, 9 H, 3 CH , tBu),
(br. s, 1 H, NH), 6.67 (d, J ϭ 8.1 Hz, 2 H, H
o
6 4
H
3.07 (s, 3 H, MeNH), 4.17 (s, 1 H, NH), 7.86 (s, 2 H, 3-H and 5-
1
3
J ϭ 8.1 Hz, 2 H, H , MeC
m
6
H
4
3 3
): δ ϭ 27.0 (CCH ), 34.8
7
3
3
ϩ
2
2 3
ies): 423, 425, 427 (1:2:1) [M ]. C17H19Br N
4
ϩ
N 9.81.
351 (1:2:1) [M ]. C11
2 3
H15Br N (349.07): calcd. C 37.85, H 4.33, Br
4
5.78, N 12.04; found C 37.90, H 4.34, Br 45.75, N 11.93.
1
(
-(tert-Butyl)-2-(3,5-dibromophenyl)diazene
300 MHz, CDCl ): δ ϭ 1.32 (s, 9 H, 3 CH
.8 Hz, 1 H, 4-H), 7.72 (d, J ϭ 1.8 Hz, 2 H, 2-H and 6-H) ppm. to the general procedure, the reaction of salt 2 with iPrNH
(18):
1H
NMR
3
3
, tBu), 7.62 (t, J ϭ
2,6-Dibromo-4-[(tert-butyl)azo]-N-isopropylaniline (21c): According
gave
37 mg (81 %) of 21c as a yellow oil. IR (KBr): ν˜ ϭ 3380 (NH)
1
2
13
C NMR (75 MHz, CDCl
br.t, J ഠ 2 Hz C-3 and C-5), 124.1 (dt, J ϭ 170.2, 5.6 Hz, C-2 and cm . H NMR (300 MHz, CDCl
C-6), 134.8 (dt, J ϭ 173.5, 5.8 Hz, C-4), 153.2 (t, J ϭ 2.5 Hz, C-1) 2 CH , iPr), 1.28 (s, 9 H, 3 CH
ppm. 15N NMR/INEPT (30 MHz, [D
]acetone): δ ϭ 179.8 (NtBu), (sept, J ϭ 6.7 Hz, 1 H, CHMe ), 7.84 (s, 2 H, 3-H and 5-H) ppm.
18.3 (ArN) ppm. MS (70 eV), m/z (rel. intensities): 318, 320, 322 MS (70 eV), m/z (rel. intensities): 375, 377, 379 (1:2:1) [M ].
(377.12): calcd. C 41.40, H 5.08, Br 42.38, N 11.14;
found C 41.40, H 5.08, Br 42.38, N 11.14.
3 3 3
): δ ϭ 26.6 (CH ), 68.5 (CMe ), 123.0
Ϫ1
1
(
3
): δ ϭ 1.18 (d, J ϭ 6.7 Hz, 6 H,
3
, tBu), 3.87 (s, 1 H, NH), 4.10
3
6
2
ϩ
1
ϩ
(1:2:1) [M ]. C10
H
12Br
2
N
2
(320.02): calcd. C 37.53, H 3.78, Br
9.94, N 8.75 found C 37.61, H 3.79, Br 50.02, N 8.70.
13 2 3
C H19Br N
4
4800
© 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2004, 4794Ϫ4801

2-Alkyl-1,2,3,4-benzotetrazinium Tetrafluoroborates
FULL PAPER
2,6-Dibromo-4-[(tert-butyl)azo]-N,N-dimethylaniline (21d): Accord-
ring at room temperature, the solvent was evaporated and the resi-
ing to the general procedure, the reaction of salt 2 with Me
2
NH
gave 33 mg (75 %) of 21d as an orange oil. H NMR (300 MHz,
CDCl ): δ ϭ 1.29 (s, 9 H, 3 CH , tBu), 2.98 (s, 6 H, Me N), 7.85
s, 2 H, 3-H and 5-H) ppm. C NMR (75 MHz, CDCl ): δ ϭ 27.1
CH ), 35.4 (CH N), 67.0 (CMe ), 112.9 (C-2 and C-6), 127.1 (C- s, 1 H, NH), 6.79 (dd, J ϭ 8.1, 1.7 Hz, 1 H, 4-H), 6.88 (d, J ϭ
and C-5), 143.5 (C-4), 148.6 (C-1) ppm. MS (70 eV), m/z (rel. 1.7 Hz, 1 H, 6-H), 7.51 (d, J ϭ 8.1 Hz, 1 H, 3-H) ppm. MS (70 eV),
3
due was purified by chromatography (silica gel; CHCl ) to give
1
Ϫ1
60 mg (84 %) of 25 as a red oil. IR (KBr): ν˜ ϭ 3420 cm (NH).
1
3
3
2
H NMR (300 MHz, CDCl
3
): δ ϭ 1.26 (d, J ϭ 6.6 Hz, 6 H, 2 CH
3
,
13
(
(
3
iPr), 1.33 (s, 9 H, 3 CH , tBu), 3.67 (sept, 1 H, CHMe
3
2
), 5.60 (br.
3
3
3
3
ϩ
ϩ
intensities): 361, 363, 365 (1:2:1) [M ]. C12
H17Br
2
N
3
(363.09):
3
m/z (rel. intensities): 297, 299 (1:1) [M ]. C13H20BrN (298.22):
calcd. C 39.69, H 4.72, Br 44.01, N 11.57; found C 39.76, H 4.73,
Br 43.90, N 11.45.
calcd. C 52.36, H 6.76, Br 26.79, N 14.09; found C 52.39, H 6.77,
Br 26.69, N 14.15.
4-{2,6-Dibromo-4-[(tert-butyl)azo]phenyl}morpholine (21e): Accord-
ing to the general procedure, the reaction of salt 2 with morpholine
gave 37 mg (76 %) of 21e as an orange oil. H NMR (300 MHz,
Acknowledgments
1
[
3
(
(
(
7
D
6
]acetone): δ ϭ 1.33 (s, 9 H, 3 CH
.79 (m, 4 H, CH
O), 7.86 (s, 2 H, 3-H and 5-H) ppm. 13C NMR
75 MHz, [D ]acetone): δ ϭ 27.0 (CH
CH O), 68.9 (CMe
3 2
, tBu), 3.22 (m, 4 H, CH
N), This work was financially supported by the Russian Foundation
for Basic Research (project 04-03-32432).
2
6
3
), 50.1 (CH
2
N), 67.8
), 126.2 (d, J ϭ 5.0 Hz, C-2 and C-6), 127.4
[1]
2
3
A. M. Churakov, V. A. Tartakovsky, Chem. Rev. 2004, 104,
3
3
dd, J ϭ 169.4, 6.2 Hz, C-3 and C-5), 148.9 (m, J3-H ϭ J5-H
.0 Hz, C-1), 150.4 (t, J ϭ 3.1 Hz, C-4) ppm. N NMR/INEPT
ϭ
2601Ϫ2616.
2
15
[2]
T. Kaihoh, T. Itoh, K. Yamaguchi, A. Ohsawa, J. Chem. Soc.,
(
(
(
30 MHz, [D
rel. intensities): 403, 405, 407 (1:2:1) [M ]. C14
405.13): calcd. C 41.51, H 4.73, Br 39.45, N 10.37; found C 41.45,
6
]acetone): δ ϭ 182.7 (NtBu) ppm. MS (70 eV), m/z
Perkin Trans. 1 1991, 2045Ϫ2048.
[
[
[
3]
4]
5]
ϩ
D. L. Lipilin, O. Y. Smirnov, A. M. Churakov, Y. A. Strelenko,
2 3
H19Br N O
S. L. Ioffe, V. A. Tartakovsky, Eur. J. Org. Chem. 2002,
3
435Ϫ3446.
H 4.71, Br 39.51, N 10.41.
For ring-chain tautomerism in the closely related cyclopenta-
annulated 2-R-1,2,3,4-tetrazines, see: P. J. Mackert, K. Hafner,
N. Nimmerfroh, K. Banert, Chem. Ber. 1994, 127, 1479Ϫ1488.
D. L. Lipilin, P. A. Belyakov, Y. A. Strelenko, A. M. Churakov,
O. Y. Smirnov, S. L. Ioffe, V. A. Tartakovsky, Eur. J. Org. Chem.
5
,7-Dibromo-2-(tert-butyl)-2,6-dihydro-6-(4-morpholinyl)-1,2,3,4-
benzotetrazine (22): A solution of morpholine (80 mg, 0.92 mmol)
in 10 mL of dry CCl was added dropwise to a stirred suspension
of salt 2 (200 mg, 0.46 mmol) in 10 mL of dry CCl at 0 °C. The
reaction reached completion after an additional 5 min of stirring
at 0 °C, to afford a solution of 22, which was analyzed by NMR
4
4
2
002, 3821Ϫ3826.
[6]
[7]
H. Bauer, G. R. Bedford, A. R. Katritzky, J. Chem. Soc.
1
964, 751Ϫ755.
1
spectroscopy. H NMR at 273 K (300 MHz, CCl
4
/CDCl
N), 3.65 (m, 4 H, CH
.66 (s, 1 H, 6-H), 6.69 (s, 1 H, 8-H) ppm. 13C NMR at 273 K
75.5 MHz, CCl /CDCl ): δ ϭ 28.1 (CH ), 49.3 (CH N), 64.9
CMe ), 67.3 (CH O), 73.3 (dd, J ϭ 144.3, 6.0 Hz, C-6), 106.5 (d,
3
): δ ϭ 1.50
The hydrolysis of compound 7 under drastic reaction con-
(
4
(
(
s, 9 H, 3 CH
3
, tBu), 2.81 (m, 4 H, CH
2
2
O),
ditions gave 2-(phenylazo)phenol: MeCN/H O, NaOH, reflux,
2
30 min (90 %) (cf.: T. Cohen, A. G. Dietz, J. R. Miser, J. Org.
Chem. 1977, 42, 2053Ϫ2058).
4
3
3
2
[
[
8]
9]
H. Zollinger, Acc. Chem. Res. 1973, 6, 335Ϫ341. H. Zollinger,
Diazo Chemistry I: Aromatic and Heteroaromatic Compounds,
VCH, Weinheim, 1994.
J. K. Kochi, J. Am. Chem. Soc. 1957, 79, 2942Ϫ2948.
C. Galli, J. Chem. Soc., Perkin Trans. 2 1982, 1139Ϫ1141.
For related annulated 2-alkyl-1,2,4-benzotriazin-3(2H)-ones
see: M. M. M. Sallam, Y. A. Ibrahim, S. A.-L. Abel-Hady,
Helv. Chim. Acta 1976, 59, 1093Ϫ1098.
3
2
J ϭ 11.0 Hz, C-5), 124.4 (t, J ϭ 5.3 Hz, C-4a or C-7), 126.0 (dd,
J ϭ 171.5, 4.2 Hz,C-8), 135.9 (dd, J ϭ 10.6, 5.0 Hz, C-7 or C-4a),
1
38.5 (d, J ϭ 2.4 Hz, C-8a) ppm. 15N NMR/INEPT (30 MHz,
[10]
[11]
3
CCl
4
/CDCl
3
): δ ϭ Ϫ135.4 (m, N-2), Ϫ89.5 (d, J ϭ 2.7 Hz, N-1).
Formation of 21g from 22. Experiment 1: A solution of 22 in CCl
5 mL, 0.023 mmol/mL) was allowed to stand at 20 °C for 30 min.
4
(
[12]
L. Gattermann, Ber. Dtsch. Chem. Ges. 1890, 23, 1218Ϫ1228;
L. Gattermann, A. Cantzler, Chem. Ber. 1892, 25, 1086Ϫ1091.
The solvent was evaporated and the residue purified by chromatog-
raphy (silica gel; hexane/EtOAc, 7:1) to give 20.5 mg (44 %) of 21g
identical to the sample obtained above. Experiment 2: A solution
[13] 15
3 2
N NMR, δ from external CH NO , upfield shifts are nega-
tive.
[14]
of morpholine (20 mg, 0.23 mmol) in 5 mL of dry CCl
to a stirred solution of 22 (0.115 mmol) in 5 mL of dry CCl
min of stirring at room temperature, the solvent was evaporated
4
was added
The instability of azo compounds of the type ArϪNϭNϪH is
well known: E. M. Kosower, Acc. Chem. Res. 1971, 4,
4
. After
1
93Ϫ198.
5
[
[
15]
16]
This reaction will be reported in due course.
In ref. the assignments of NMR signals for 4,6-dibromo-2-
and the residue purified by chromatography (silica gel; hexane/
EtOAc, 7:1) to give 34.5 mg (76 %) of 21g, identical to the sample
obtained above. Experiment 3: Treatment of 22 (0.115 mmol) with
[5]
(
tert-butylazo)benzenediazonium tetrafluoroborate (com-
[5]
pound 3f in ref. ) and 4,6-dibromo-2-(methylazo)benzenedia-
tBuNH
forded 32.6 mg (70 %) of 21g, identical to the sample obtained
above. Experiment 4: Treatment of 22 (0.115 mmol) with Et
17 mg, 0.23 mmol) according to the above procedure afforded
2
(17 mg, 0.23 mmol) according to the above procedure af-
[5]
zonium tetrafluoroborate (compound 3i in ref. ) are wrong
due to a mistake in the numbering of these compounds. There
1
3
3
N
is also a mistake in the C NMR signal assignments for 2-
(
2
[(tert-butyl)azo]-4,6-dichlorobenzenediazonium tetrafluorobo-
[5]
5.6 mg (55 %) of 21g, identical to the sample obtained above.
rate (3 in ref. ). The corrected assignment for this compound
13
is: C NMR at 297 K (75.5 MHz, [D
6
]acetone): δ ϭ 29.4
5
(
(
-Bromo-2-[(tert-butyl)azo]-N-isopropylaniline (25): Isopropylamine
71 mg, 1.2 mmol) was added to a stirred suspension of salt 5
(
CH ), 82.4 (CMe ), 128.9 (C-3), 145.7 (C-5) ppm.
3
3
[17]
E. Bamberger, Ber. Dtsch. Chem. Ges. 1900, 33, 3188Ϫ3192.
86 mg, 0.24 mmol) in 5 mL of dry CH
3
CN. After 15 min of stir-
Received August 18, 2004
Eur. J. Org. Chem. 2004, 4794Ϫ4801
www.eurjoc.org
© 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4801