Nucleophilic substitution of 4H-imidazoles by thioles: New starting materials for tetraazafulvalenes and fused heterocycles

Article abstract of DOI:10.1007/s007060070026

Different reactivities towards the 4H-imidazoles 1 depending on the nature of the sulfur containing nucleophile were observed. Whereas H₂S and aromatic thioles led to 4,5-diaminoimidazoles in the course of a reduction process, treatment with al

Full text of DOI:10.1007/s007060070026

Monatshefte fuÈr Chemie 131, 1181±1190 (2000)
Nucleophilic Substitution of 4H-Imidazoles
by Thioles: New Starting Materials for
Tetraazafulvalenes and Fused Heterocycles
2
Jens Atzrodt1, Rainer Beckert1;Ã, and Helmar Gorls
È
1
È
Institut fuÈr Organische und Makromolekulare Chemie, Friedrich-Schiller-Universitat, D-07743
Jena, Germany
È
Institut fuÈr Anorganische und Analytische Chemie, Friedrich-Schiller-Universitat, D-07743 Jena,
2
Germany
Summary. Different reactivities towards the 4H-imidazoles 1 depending on the nature of the sulfur
containing nucleophile were observed. Whereas H2S and aromatic thioles led to 4,5-diamino-
imidazoles in the course of a reduction process, treatment with aliphatic mercaptanes resulted in
a substitution-reduction-dimerization cascade which ®nally gave bis-imidazoles. Their oxidative
modi®cation in presence of m-chloroperbenzoic acid then allowed new 1,3,5,7-tetraazafulvalenes to
be easily obtained. Treatment of the bis-imidazoles with acetylene dimethyldicarboxylate caused
cleavage of the central bond, thus leading to the formation of derivatives which are of interest for the
transformation into fused heterocycles such as imidazo[4,5-b]azepines.
Keywords. Fused heterocycles; 4H-Imidazoles; Nucleophilic substitution; 1,3,5,7-Tetraazafulva-
lenes.
Introduction
We have recently reported a new synthesis of 4H-imidazoles of type 1 [1]. These
heterocycles can be regarded as 1,3,6-triazafulvenes and have received particular
attention not only from structural and theoretical [2] but also from synthesis points
of view [3,4]. Up to now, possibilities for varying the peripheric residues at the
positions 4 and 5 of the imidazole ring have been relatively restricted due to the low
stabilities of the starting materials employed. These synthesis problems have now
been solved by a new nucleophilic exchange reaction in the course of which the
cyclic iminium salt 2 possessing the resonance structure of a (4n)ꢀ-bond system 20
[5] have to be considered in order to explain the reaction pathway. Using this
method, arylamino, alkylamino, and hydrazino substructures as well as NH2-groups
can be introduced in the 4- and 5-position of the heterocycle 1 [6]. Continuing our
investigations, we now report upon the reactivity of 1 and 2 towards sulfur
containing nucleophiles.
Ã
Corresponding author

1182
J. Atzrodt et al.
Results and Discussion
Depending on the nature of the SH-nucleophile employed, different reactivities
towards the 4H-imidazoles 1 were observed. A quantitative reduction of 1 to form
the corresponding 4,5-diamino-imidazoles 3 could be achieved by passing a
constant stream of H2S through the reaction mixture containing catalytical amounts
of mineral acids. A comparable reaction course was observed by treatment of 1 with
thiophenols. In addition to 3, the oxidatively formed diaryldisul®des could be
isolated and spectroscopically characterized. An ef®cient access to the imidazoles 3,
which are heterocyclic analogues to electron-rich ole®nes, has been already realized
by reduction of 1 with zinc, with ascorbic acid, or by reduction with metallic lithium
and subsequent hydrolysis of the preformed trianion [7]. In direct contrast to the SH
and SPh nucleophiles, a more complicated reaction was observed when alkylthioles
were employed. Substitution of one of the arylamine residues in the ®rst step of the
reaction resulted in the mixed substituted derivative 4. A comparable difference in
thiolysis reactions of aromatic and aliphatic thioles has been already reported [8].
However, in the presence of an excess of the thiol, the intermediate 4 underwent an
electron transfer reaction yielding the diazacyclopentadienyl radical 5 which could
be detected by ESR measurements. Analogous to dithiazolyl radicals [9], 5
dimerized under formation of biimidazole systems of type 6. Treatment of 1a±c
with ethanethiol or 2-mercaptoethanol thus gave rise to the bluish ¯uorescent
derivatives 6a±d in good yields. We succeeded in determining the structure of 6a,
which is illustrated in Fig. 1. In the crystal of 6a, both imidazole rings occupy
different planes which are shifted parallel to each other. The thioether subunits are
Ã
Fig. 1. Crystal structure of 6a; the numbering corresponds to that used for the X-ray analysis ;
symmetry transformation used to generate equivalent atoms: A x ‡ 2; y; z ‡ 1
Ã
1.310(5), N2-C1 1.418(5), C2-N3 1.344(5), C3-C3A 1.545(8), C3-S 1.844(5); N1-C1-N2 117.9(4),
ꢀ
Ê
Selected distances (A) and angles ( ): C1-N1 1.297(5), N1-C3 1.465(5), C3-C2 1.523(6), C2-N2
C1-N2-C2 103.1(3), C1-N1-C3 105.0(3), N1-C3-C2 102.3(3), N1-C3-S1 111.3(3)

New Precursors for Tetraazafulvalenes
1183
Scheme 1
located in an anti-position orthogonally above and beneath the plane of the ring
Ê
system. The bond length of the central C-C-bond (1.545(8) A) corresponds to a
typical Csp3-Csp3 single bond [10]. In the 13C NMR spectrum of 6a, the signal of
the two quaternary ring carbon atoms appeared at ꢁ ˆ 102.8 ppm which con®rms a
sp3 hybridized bonding state in solution. The NH protons were detected as a sharp
singlet at ꢁ ˆ 12.50 ppm. In addition, all NMR spectra of compounds 6 indicated a
diastereoselective dimerization reaction due to the presence of a doubled set of
signals especially evident for the aromatic protons. A ratio of 8:1 prefering the
anti-isomer was found. Most likely, steric aspects are responsible for this diastereo-
selective differentiation. This is in accord with the small number of diastereo-
selective radical reactions known to present date [11]. As shown in Fig. 1, the
arylamino groups achieves a maximum separation from the sterically demanding
thioether substructure only in the anti-form. In addition, the strong intramolecular

1184
J. Atzrodt et al.
hydrogen bond between the NH proton and the ring nitrogen can be realized only in
the anti-orientation.
In contrast to reactivities reported for diazathioorthooxalates [12], derivatives of
type 6 do not loose diethyldisul®de. In addition, the formation of a central double
bond could not be induced either by increasing the temperature or by changing the
solvent. The expected elimination reaction took place only after addition of m-
chloroperbenzoic acid to afford the 1,3,5,7-tetraazafulvalenes 8a±c as microcrystal-
line blue solids. In the ®rst step, both thioether groups are apparently oxidized to the
sulfones 7 [13] which are then subsequently decomposed thermally to give the
corresponding sulfonyl radicals [14]. Such an oxidative activation has already been
described for the synthesis of tetrathiafulvalenes starting from orthothiooxalates
[15]. The new 1,3,5,7-tetraazafulvalenes 8 are nearly insoluble in common organic
solvents. The determination of the con®guration of the central double bond was
therefore not feasible. However, the (E)-con®guration in 8 seems to be favoured due
to the pre®xation in the educts 6. The purity of the products was con®rmed by
combustion analysis and mass spectra. The remarkable and strong bathochromic
absorptions of the compounds 8 are comparable with those of the heterofulvalenes 9
[12]. Both systems contain a vinylene homologous indigoid chromophore [16, 17]
which has been modi®ed by imino substituents. In comparision to 9, the exchange
of the SCH3 group by an arylamino residue in 8 results in a bathochromic shift of
the longest wavelength absorption of about 50 nm.
A closely related reaction occured when singlet oxygen was employed as the
oxidizing agent. Under mild conditions, the oxo derivatives 10 were obtained as
yellowish compounds in good yields. The mechanism is assumed to proceed
through the formation of the initial product 7, which leads to the fulvalenes 8 and
then under cleavage of the central double bond [18] to the product 10.
Upon treatment of 6 with acetylenedimethyldicarboxylate, an addition reaction
1
was observed in which the colourless product 11 was formed. H, 13C NMR, and
MS spectroscopic data con®rmed the structural assignments of the 4H-imidazole
derivative 11a. The H NMR spectrum of 11a revealed ± in addition to the
1
characteristical signal pattern for the ethyl and tolyl residues ± two sharp singlets at
ꢁ ˆ 9.47 and 6.38 ppm. A comparison with HMQC experiments showed that the ®rst
singlet can be assigned to the NH-proton and the second one at lower ®eld to the
CH-group. Whereas in NOESY measurements the NH-proton showed dipolar
coupling only with the neighbouring protons of the aryl moity, no cross peaks were
observed for the CH group. These ®ndings point to an arrangement as represented in
formula 11, although comparable addition reactions mainly lead to derivatives of
fumaric acid [16]. Due to the chiral centre, the CH2-group of the ethyl residue is
1
diastereotopic as is shown by the presence of a doubled quartett in the H NMR
spectrum of 11a. Furthermore, the signal of a quaternary ring carbon atom in 11a
appeared at high ®eld (83.9 ppm), thus indicating a sp3 hybridized bonding state.
Upon use of an excess of acetylenedimethyldicarboxylate, a second addition
reaction forming imidazo[4,5-b]azepines of type 12 was observed. This indicates a
high synthetic potential for heterocycles 11. A mechanistic interpretation of the
described ring fusion reaction is not yet available. Despite the large number of well-
documented reactions involving acetylenedicarboxylates [19], there exist only a few
examples which show any similarity to our experimental ®ndings [20, 21]. The

New Precursors for Tetraazafulvalenes
1185
Scheme 2
derivatives presented here can be considered as being further evidence for
unexpected ring transformation reactions. We will present our concept for the
mechanism of this reaction as well as the application of 11 as a versatile starting
material for the synthesis of heterobicycles in a forthcoming paper.
Experimental
All reagents were of commercial quality (Aldrich, Fluka, Merck) and were used as received. Solvents
were dried and puri®ed using standard techniques. Reactions were monitored by TLC on plastic plates

1186
J. Atzrodt et al.
coated with neutral alumina with ¯uorescence indicator (Polygram ALOX N/UV254 from Macherey-
Nagel). Separations by ¯ash chromatography were carried out on neutral alumina (Merck, aluminium
oxide 90 active neutral, activity V, particle size 0.063±0.2 mm, 70±230mesh ASTM). Melting points
were measured with a Galen III (Boetius system) from Cambridge Instruments and are uncorrected.
1
UV/Vis spectra were obtained using a Perkin Elmer Lambda 19 spectrophotometer. The H and 13
C
NMR spectra were obtained on Bruker DRX 400 and Bruker AC 250 spectrometers (1H NMR shifts:
relative to 1H signals of the solvent). Mass spectra were taken from measurements on a Finnigan MAT
SAQ 710 mass spectrometer. Elemental analyses were carried out with an automatic analyzer LECO
CHNS 932. Their results were in good agreement with the calculated values.
General procedure for the reaction of sulfur containing nuleophiles with 4H-imidazoles
Concentrated HCl was added in catalytical amounts (3 drops) to a solution of 1.0 mmol 1 in 30 cm3
THF. The colour of the solution immediately turned to green because of the formation of the
protonated heterocycle 2. An excess of alkylmercaptane (1 cm3) was subsequently added before the
solution was heated to 50ꢀC. The progress of the reaction was monitored by TLC. Reaction times
were usually chosen between 1 and 4 h. After ®ltration, the solvent was removed in vacuo, and the
residue was puri®ed either by column chromatography (eluent: ethyl acetate/n-heptane, 1:5) or by
recrystallization from acetone/n-heptane to yield the products 6a±d.
4,40-Bis-ethylsulfanyl-2,20-diphenyl-N5,N50-di-(4-tolyl)-4H,40H-[4,40]biimidazolyl-5,50-diamine
(6a; C36H36N6S2)
1
Yield: 0.24 g (77%); colourless crystals; m.p.: 182ꢀC; H NMR (400 MHz, ꢁ, DMSO-d6): 12.49 (s,
2H, NH), 7.94 (d, J ˆ 7:85 Hz, 4H), 7.43 (t, J ˆ 7:67 Hz, 4H), 7.32 (t, J ˆ 7:45 Hz, 2H), 7.27 (d,
J ˆ 8:26 Hz, 4H), 6.94 (d, J ˆ 8:23 Hz, 4H), 2.70 (m, 4H, CH2), 2.18 (s, 6H, CH3-Tol), 1.13 (t,
J ˆ 7:28 Hz, 6H, CH3) ppm; 13C NMR (100 MHz, ꢁ, DMSO-d6): 147.5, 143.2, 142.5, 130.5, 129.4,
129.1, 128.9, 128.7, 126.2, 124.7, 120.4, 115.0, 102.8, 30.3, 20.2, 14.5 ppm; MS (CI): m/z (%) ˆ 619
‡
‡
[M‡2H ] (2), 310 [1/2 M ] (100), 280 (22), 118 (11).
4,40-Bis-ethylsulfanyl-2,20-diphenyl-N5,N50-bis-(4-tert.-butyl-phenyl)-4H,40H-[4,40]biimidazolyl-
5,50-diamine (6b; C42H48N6S2)
Yield: 0.22 g (63%); greenish crystals; m.p.: 156ꢀC; 1H NMR (250 MHz, ꢁ, CDCl3): 7.77 (d,
J ˆ 8:12 Hz, 4H), 7.34-7.20 (m, 14H), 5.98 (brs, 2H, NH), 2.55 (q, J ˆ 7:34 Hz, 4H), 1.24 (s, 18H),
1.16 (t, J ˆ 7:34 Hz, 6H) ppm; 13C NMR (62 MHz, ꢁ, CDCl3): 143.9, 142.5, 129.7, 128.8, 128.7,
‡
128.5, 126.0, 125.8, 124.9, 115.6, 34.0, 31.5, 31.2, 15.2 ppm; MS (ESI): m/z (%) ˆ 725.2 [M‡Na ]
‡
(12), 352.1 [1/2 M ] (100).
4,40-Bis-ethylsulfanyl-2,20-diphenyl-N5,N50-bis-ꢂ-naphthyl-4H,40H-[4,40]biimidazolyl-
5,50-diamine (6c; C42H36N6S2)
Yield: 0.20 g (58%); greenish solid; m.p.: 194ꢀC; 1H NMR (250 MHz, ꢁ, CDCl3): 8.02 (d,
J ˆ 7:09 Hz, 4H), 7.92 (t, J ˆ 7:02 Hz, 4H), 7.83 (m, 6H), 7.52±7.32 (m, 14H), 6.69 (s, 2H, NH),
2.61 (q, J ˆ 7:34 Hz, 4H), 1.22 (t, J ˆ 7:32 Hz, 6H) ppm; 13C NMR (62 MHz, ꢁ, CDCl3):
148.5, 144.5, 138.7, 134.4, 129.6, 128.9, 128.9, 128.7, 126.5, 125.5, 125.1, 125.0, 124.1, 120.1,
‡
110.6, 103.0, 31.4, 15.3 ppm; MS (ESI): m/z (%) ˆ 713.1 [M‡Na ] (10), 400.1 (22), 368.1 (34),
346 (100).

New Precursors for Tetraazafulvalenes
1187
4,40-Bis-(2-hydroxy-ethylsulfanyl)-2,20-diphenyl-N5,N50-di-(4-tolyl)-4H,40H[4,40]biimidazolyl-
5,50-diamine (6d; C36H36N6S2O2)
1
Yield: 0.17 g (54%); greenish crystals; m.p.: 211ꢀC; H NMR (250 MHz, ꢁ, DMSO-d6): 12.48 (s,
2H), 7.94 (d, J ˆ 7:39 Hz, 4H), 7.55 (s, 2H), 7.43 (t, J ˆ 7:18 Hz, 4H), 7.32 (m, 6H), 6.96 (d,
J ˆ 6:37 Hz, 4H), 2.75 (q, J ˆ 6:65 Hz, 4H), 2.18 (s, 6H) ppm; 13C NMR (62 MHz, ꢁ, DMSO-d6):
147.8, 143.1, 142.1, 130.2, 128.9, 128.6, 128.0, 126.3, 124.7, 115.0, 101.9, 59.8, 39.7, 20.2 ppm; MS
‡
(CI): m/z (%) ˆ 325 [1/2 M‡H ] (65), 280 (78), 118 (52), 71 (38), 57 (100).
General procedure for the synthesis of 1,3,5,7-tetraazafulvalenes 8
m-Chloroperbenzoic acid (0.19 g, 1.2 mmol) was added to a solution of 1.0 mmol 6 in 50 cm3
toluene. The solution was then stirred under re¯ux for 1±2 h while a dark coloured precipitate was
slowly formed. The bluish-black solid was collected by ®ltration and repeatedly washed with toluene
and acetone to yield the 1,3,5,7-tetraazafulvalenes 8.
2,6-Bis-phenyl-4,8-bis-(4-tolylamino)-1,3,5,7-tetraazafulvalene (8a; C32H26N6)
‡
Yield: 0.21 g (43%); black crystals; m.p.: 357ꢀC; MS (CI): m/z (%) ˆ 495 [M‡H ] (100), 479 (8),
247 (5), 121 (27), 93 (8); UV/Vis (DMSO): ꢃmax (lg") ˆ 288 (3.81), 424 (3.65), 633 (3.65), 681
(3.54) nm.
2,6-Bis-phenyl-4,8-bis-(4-tert.-butylphenylamino)-1,3,5,7-tetraazafulvalene (8b; C38H38N6)
‡
Yield: 0.24 g (41%); black solid; m.p.: >360ꢀC; MS (CI): m/z (%) ˆ 579 [M‡H ] (100), 521 (10),
121 (18), 93 (13); UV/Vis (DMSO): ꢃmax (lg") ˆ 285 (3.79), 424 (3.63), 448 (3.62), 636 (3.59), 678
(3.56) nm.
2,6-Bis-phenyl-4,8-bis-(ꢂ-naphthylamino)-1,3,5,7-tetraazafulvalene (8c; C38H26N6)
‡
Yield: 0.18 g (33%) black solid; m.p.: 340ꢀC; MS (CI) ˆ m/z (%): 567 [M‡H ] (78), 442 (7),
121 (43), 93 (100), 144 (8); UV/Vis (DMSO): ꢃmax (lg") ˆ 415, 646 (3.75), 720 (3.74), 857
(3.79) nm.
General procedure for the synthesis of the imidazolones 10
A biimidazole derivative 6 (1.0 mmol) was dissolved in 20 cm3 CH2Cl2, and 5 mg tetraphenylpor-
phyrine were added. A constant stream of dry O2 was passed through the reaction mixture at 20ꢀ
for 3 h while externally irradiating with a Na vapour lamp. The solution turned greenish, and a
yellow precipitate was formed. The microcrystalline solid was collected by ®ltration and repeatedly
washed with CH2Cl2 to yield the corresponding imidazolones 10.
2-Phenyl-5-(4-tolylamino)-imidazol-4-one (10a; C16H13N3O)
Yield: 0.15 g (58%); yellow crystals; m.p.: 264ꢀC; 1H NMR (400 MHz, ꢁ, DMSO-d6): 12.47 (s, 1H,
NH), 8.16 (d, J ˆ 7:48 Hz, 2H), 7.61 (m, 3H), 7.23 (d, J ˆ 8:08 Hz, 2H), 7.13 (d, J ˆ 8:12 Hz, 2H),
2.27 (s, 3H) ppm; 13C NMR (100 MHz, ꢁ, DMSO-d6): 153.8, 144.6, 137.6, 134.9, 129.6, 129.4,
‡
128.8, 128.6, 127.8, 126.7, 119.1, 21.1 ppm; MS (CI): m/z (%) ˆ 264 [M‡H ] (100), 154 (3), 122
(5), 108 (10), 89 (7); UV/Vis (DMSO): ꢃmax (lg") ˆ 271 (5.11), 475 (3.14) nm.

1188
J. Atzrodt et al.
5-(4-tert.-Butyl-phenylamino)-2-phenyl-imidazol-4-one (10b; C19H19N3O)
Yield: 0.14 g (47%); yellow crystals; m.p.: 215ꢀC; 1H NMR (250 MHz, ꢁ, DMSO-d6): 8.19 (d,
J ˆ 8:65 Hz, 2H), 7.61 (m, 3H), 7.43 (d, J ˆ 8:44 Hz, 2H), 7.37 (d, J ˆ 8:58 Hz, 2H), 1.31 (s, 9H)
ppm; 13C NMR (62 MHz, ꢁ, DMSO-d6): 145.0, 138.8, 133.9, 128.9, 128.4, 128.2, 128.0, 127.6,
‡
125.7, 125.4, 124.9, 34.3, 31.1 ppm; MS (CI): m/z (%) ˆ 307 [M‡H ] (96), 292 (100), 276 (27), 159
(96), 149 (36), 134 (95), 117 (32), 104 (66), 91 (17), 77 (50); UV/Vis (DMSO): ꢃmax (lg") ˆ 286
(4.10), 379 (3.64), 426 (3.65) nm.
2-(4-Ethylsulfanyl-2-phenyl-5-phenylamino-4H-imidazol-4-yl)-but-2-en-dicarboxylicacid
dimethylester (11a; C24H25N3O4S)
A solution of 0.6 g 6a (1.0 mmol) and 0.3 g acetylenedimethyldicarboxylate (2.0 mmol) dissolved in
20 cm3 THF was heated for 3 h under re¯ux. The formation of a colourless product could be
monitored by TLC. After completion of the reaction, the solvent was evaporated, and the residue was
puri®ed by column chromatography (ethylacetate/n-heptane 1:5).
1
Yield: 0.2 g (45%); colourless solid; m.p.: 101ꢀC; H NMR (400 MHz, ꢁ, CDCl3): 9.47 (s, 1H,
NH), 8.38 (d, J ˆ 8:04 Hz, 2H, o-Ph), 7.76 (d, J ˆ 8:44 Hz, 2H, Tol), 7.54±7.45 (m, 3H, m-, p-Ph),
7.20 (d, J ˆ 8:25 Hz, 2H, Tol), 3.96 (s, 3H, CH3OOC), 3.70 (s, 3H, CH3OOC), 2.60 (m, 2H, CH2),
2.34 (s, 3H, CH3-Tol), 1.19 (t, J ˆ 7:48 Hz, 3H, CH3) ppm; 13C NMR (100 MHz, ꢁ, CDCl3): 178.2,
175.5, 169.4, 164.7, 143.1, 136.1, 133.8, 131.8, 131.6, 129.5, 129.2, 128.3, 124.1, 119.5, 83.9, 53.3,
‡
52.1, 24.5, 20.8, 14.0 ppm; MS (CI): m/z (%) ˆ 452 [M‡H ] (100), 420 (5), 390 (63), 358 (4), 269
(10), 143 (7).
General procedure for the synthesis of imidazo[4,5-b]azepines 12
A solution of 0.5 mmol 6 and 0.3 g acetylenedimethyldicarboxylate (2.0 mmol) in 20 cm3 toluene
was heated under re¯ux for two days. The colourless product 11 was ®rst formed which then slowly
added a second molecule acetylenedimethyldicarboxylate to give the ®nal product 12 which was
purple. After completion of the reaction the solvent was evaporated and the residue was puri®ed by
column chromatography (ethylacetate/n-heptane 1:5) to yield the imidazo[4,5-b]azepines 12.
2-Phenyl-9-(4-tolyl)-1H-imidazo[4,5-b]azepin-5,6,7,8-tetracarboxylic
acid tetramethylester (12a; C28H25N3O8)
1
Yield: 0.08 g (31%) purple crystals; m.p.: 166±167ꢀC; H NMR (250 MHz, ꢁ, CDCl3): 7.54 (d,
J ˆ 7:84 Hz, 2H), 7.46±7.35 (m, 3H), 7.25 (d, J ˆ 8:71 Hz, 2H), 7.05 (d, J ˆ 8:30 Hz, 2H), 6.66 (s,
1H, NH), 3.90 (s, 3H), 3.86 (s, 3H), 3.81 (s, 3H), 3.13 (s, 3H), 2.26 (s, 3H) ppm; 13C NMR (62 MHz,
ꢁ, CDCl3): 166.6, 165.6, 163.8, 160.9, 141.0, 140.5, 139.4, 131.4, 130,8, 130.5, 129.9, 129.8, 129.6,
128.9, 128.7, 127.3, 125.7, 125.1, 116.7, 53.6, 53.1, 52.9, 52.3, 20.6 ppm; MS (EI): m/z (%) ˆ 531
‡
[M ] (100), 498 (10), 413 (17), 381 (44), 357 (15), 310 (17), 252 (22), 194 (17), 91 (37); UV/Vis
(CHCl3): ꢃmax (lg") ˆ 259 (4.24), 350 (3.81), 521 (3.33) nm.
2-Phenyl-9-(4-tert.-butyl-phenyl)-1H-imidazo[4,5-b]azepin-5,6,7,8-tetracarboxylicacid
tetramethylester (12b; C31H31N3O8)
Yield: 0.06 g (12%); purple solid; m.p.: 158±162ꢀC; 1H NMR (400 MHz, ꢁ, CDCl3): 7.55 (d,
J ˆ 7:96 Hz, 2H), 7.43 (m, 3H), 7.32 (m, 4H), 3.90 (s, 3H), 3.86 (s, 3H), 3.81 (s, 3H), 3.13 (s, 3H),
1.27 (s, 9H) ppm; 13C NMR (100 MHz, ꢁ, CDCl3): 143.9, 129.7, 128.9, 128.7, 127.2, 126.2, 125.8,
‡
116.3, 53.5, 53.1, 52.8, 52.2, 31.4 ppm; MS (CI): m/z (%) ˆ 574 [M‡H ] (100).

New Precursors for Tetraazafulvalenes
1189
Crystal structure determination
The intensity data were collected on a Nonius KappaCCD diffractometer using graphite-
monochromated Mo-Kꢂ radiation. Data were corrected for Lorentz and polarization effects but not
for absorption [22, 23]. The structures were solved by direct methods (SHELXS [24]) and re®ned by
full-matrix least squares techniques against Fo2 (SHELXL-97 [25]). The hydrogen atom of the amino
group was located by difference Fourier synthesis and re®ned isotropically. The other hydrogen
atoms were included at calculated positions with ®xed thermal parameters. All nonhydrogen atoms
were re®ned anisotropically [25]. XP (SIEMENS Analytical X-ray Instruments, Inc.) was used for
the structure representations.
Crystal data for 6a: C36H36N6S2 Á C3H6O; M ˆ 645.87 g Á mol 1, colourless prisms, size
1
2
0:30  0:28  0:20 mm3, triclinic, space group P-1; a ˆ 9.7593(6), b ˆ 10.5440(7), c ˆ
Ê 3
ꢀ
ꢀ
Ê
11.4990(9) A, ꢂ ˆ 107.827(3), ꢄ ˆ 101.124(3), ꢅ ˆ 110.100(3) , V ˆ 997.29(12) A , T ˆ 20 C,
Z ˆ 1, ꢆcalcd ˆ 1.075 g Á cm 3, ꢇ(Mo-Kꢂ) ˆ 1.66 cm 1, F(000) ˆ 342, 8223 re¯ections in h( 12/0),
k( 12/13), l( 13/14) measured in the range 3.90ꢀ ꢁ  ꢁ 26.37ꢀ; completeness: Âmax ˆ 98.3%, 4003
independent re¯ections; Rint ˆ 0.097, 2463 re¯ections with Fo > 4ꢈ(Fo), 220 parameters, 0 restraints,
R1obs ˆ 0.1053, wR2obs ˆ 0.2643, R1all ˆ 0.1608, wRa2ll ˆ 0.2931, GOOF ˆ 1.339; largest difference
peak and hole: 1.004/ 0.417 e Á A 3. Further details are available upon request from the Cambridge
Ê
Crystallographic Data Center, 12 Union Road, Cambridge CB2 1EZ on quoting the depository
number CCSD-144291, the names of the authors, and the citation of the paper.
Acknowledgements
È È
Support from the Fonds der Chemischen Industrie, the Thuringer Ministerium fur Wissenschaft,
Forschung und Kultur and the Deutsche Forschungsgemeinschaft is gratefully acknowledged.
References
È È
È
[1] Atzrodt J, Brandenburg J, Kapplinger Ch, Beckert R, Gunther W, Gorls H, Fabian J (1997) J Prakt
Chem/Chem-Ztg 339: 729
È
[2] Fabian J, Gorls H, Beckert R, Atzrodt J (1997) J Prakt Chem/Chem-Ztg 339: 735
È È
[3] Atzrodt J, Beckert R, Brauer M, Nordhoff K, Anders E, Gorls H (1998) Eur J Org Chem 2557
È
[4] Atzrodt J, Beckert R, Gorls H (2000) J Prakt Chem 342: 245
[5] Gompper R, Wagner H-U (1988) Angew Chem 100: 1492; Angew Chem Int Ed Engl 27: 1437
È
[6] Atzrodt J, Beckert R, GuÈnther W, Gorls H (2000) Eur J Org Chem 1661
È
[7] Atzrodt J, Beckert R, Gorls H (1999) Heterocycles 51: 763
[8] BuÈchel KH, Erdmann H (1976) Chem Ber 109: 1638
[9] Oakley RT, Richardson JF, Spence REH (1994) J Org Chem 59: 2997; Oakley RT, Richardson JF,
Spence REH (1993) J Chem Soc Chem Commun 1226
[10] Allen TH, Kamard O, Watson DG, Brammer L, Guy Orpen A, Taylor R (1987) J Chem Soc
Perkin Trans 2, S1
[11] Linker Th, Schmittel M (1988) Radikale und Radikalionen in der organischen Synthese. Wiley-
VCH, Weinheim Chichester Brisbane Singapore Toronto Wiley-VCH
È
[12] Glas G, Gompper R, Junius M, Mertz R, Wagner HU, Noth H, Staudigl R (1990) J Prakt Chem/
Chem-Ztg 332: 949
È
th
[13] Schoberl E, Wagner A (1955) Methoden Org Chem (Houben-Weyl), 4 edn, vol 9, p 233
È
[14] Vogtle F, Rossa L (1979) Angew Chem 91: 534; (1979) Angew Chem Int Ed Engl 18: 514
È
[15] Fanghanel E, Hinh L, Schukat G (1976) Z Chem 16: 317
[16] Wille E, LuÈttke W (1971) Angew Chem 83: 853; (1971) Angew Chem Int Ed Engl 19: 803
[17] Klessinger M (1966) Tetrahedron 22: 2136
È
[18] Kapplinger C, Beckert R, Imhof W (1998) J Prakt Chem/Chem-Ztg 340: 323

1190
J. Atzrodt et al.: New Precursors for Tetraazafulvalenes
[19] Acheson RM (1963) Adv Heterocycl Chem 1: 125; Acheson RM, Elmore NF (1978) Adv
Heterocycl Chem 23: 263
[20] Diels O, Meyer R (1934) Liebigs Ann Chem 513: 129
[21] Crabtree A, Johnson W, Tebby JC (1961) J Chem Soc 3497
[22] COLLECT, Data Collection Software. Nonius BV, Netherlands (1998)
[23] Otwinowski Z, Minor W (1997) Processing of X-Ray Diffraction Data Collected in Oscillation
Mode. In: Carter CW, Sweet RM (eds) Methods in Enzymology, Vol 276: Macromolecular
Crystallography, Part A. Academic Press, p 307
[24] Sheldrick GM (1990) Acta Crystallogr Sect A 46: 467
È
[25] Sheldrick GM (1993) SHELXL-97. University of Gottingen, Germany
Received May 22, 2000. Accepted June 19, 2000