Tribenzotriquinacenes bearing three peripheral or bridgehead urea groups stretched into the 3-D space

Article abstract of DOI:10.3762/bjoc.7.43

The syntheses of tribenzotriquinacenes (TBTQ) bearing three phenylurea groupings at either the arene periphery or at the benzhydrylic bridgeheads of the rigid, convex-concave, C_3v-symmetrical molecular framework are reported. ¹H NMR

Full text of DOI:10.3762/bjoc.7.43

Tribenzotriquinacenes bearing three peripheral or
bridgehead urea groups stretched into the 3-D space
Jörg Tellenbröker and Dietmar Kuck*
Full Research Paper
Open Access
Address:
Beilstein J. Org. Chem. 2011, 7, 329–337.
Department of Chemistry, Bielefeld University, Universitätsstraße 25,
D-33615 Bielefeld, Germany
doi:10.3762/bjoc.7.43
Received: 06 January 2011
Accepted: 18 February 2011
Published: 18 March 2011
Email:
Dietmar Kuck* - dietmar.kuck@uni-bielefeld.de
* Corresponding author
Associate Editor: S. C. Zimmerman
Keywords:
© 2011 Tellenbröker and Kuck; licensee Beilstein-Institut.
License and terms: see end of document.
convex–concave structures; polycyclic compounds; supramolecular
chemistry; tribenzotriquinacenes; urea derivatives
Abstract
The syntheses of tribenzotriquinacenes (TBTQ) bearing three phenylurea groupings at either the arene periphery or at the
benzhydrylic bridgeheads of the rigid, convex–concave, C3v-symmetrical molecular framework are reported. 1H NMR data point to
supramolecular aggregation of these TBTQ derivatives in low-polarity solvents.
Introduction
In the course of our extended research on polyfunctionalized scientific interest over the past few decades [8-15]. For
derivatives of tribenzotriquinacene (TBTQ, 1) and some hydro- example, cone-like building blocks such as those based on
carbon congeners 2–4, which provide a great variety of calix[4]arenes and calix[6]arenes bearing urea groups at their
convex–concave molecular building blocks [1-7], we focused lower rims have been used for the generation of multi-hydrogen
our attention on the synthesis of TBTQ derivatives 5–7 with bonded dimers [8,9]. Therefore, the TBTQ framework, with its
three urea units located at the molecular periphery (Figure 1). close similarity to that of the cyclotribenzylenes and the
Owing to the rigidity of their molecular framework, these com- cyclotriveratrylenes [16-19], should constitute a promising sub-
pounds were considered of potential interest for the formation strate for such studies. In the present paper, we wish to report
of supramolecular aggregates consisting of two or more the facile access to TBTQs that bear three phenylurea groups
multiply hydrogen-bonded TBTQ units. Research on the forma- directed into the 3-D space in well controlled orientations.
tion and chemical properties of host–guest compounds bearing Some observations that point to non-covalent aggregation of
urea units as linker groups has become an exciting field of these novel molecules are also reported.
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Figure 1: Parent TBTQ 1, three bridgehead-alkylated congeners 2–4, and three TBTQ tris-urea derivatives 5–7 bearing the functional groups in three
different spatial orientations.
Results and Discussion
the crude reaction mixture. As expected, the symmetrical com-
As shown earlier, introduction of six amino groups at the pound 8 was the minor component and the ratio observed, 8:9 ≈
periphery of the TBTQ skeleton is achievable by nitration with 1:3, suggested a random attack of the electrophile at each of the
nitric acid (100%) and sulfuric acid (98%) followed by reduc- benzene rings even in the second and third step of the threefold
tion [20]. However, this holds true only for TBTQ derivatives nitration. This corresponds to comparable findings with
with alkyl groups at the benzhydrylic bridgehead positions, multiple electrophilic substitutions of the centropolyindanes and
such as the tetramethyl derivative 3 [20] and the related reflects the lack of electronic interaction between the aromatic
tripropyl analog 4 [5,7]. The monomethyl derivative 2 decom- units [22].
poses under these conditions. By contrast, threefold nitration of
the arene periphery, leading to single functionalization at the Because of the prototypical character of three-fold nitration of a
outer positions of each of the three benzene rings, was achieved TBTQ derivative, the ability to distinguish between the C3- and
by use of sodium nitrate in trifluoroacetic acid [21]. As shown the C1-symmetrical isomers 8 and 9 and to assess the relative
in Scheme 1, this method allowed us to convert the tetramethyl amounts is addressed here in some detail (Figure 2). Notwith-
derivate 3 into a mixture of the C3-symmetrical compound 8 standing the fact that the 1H NMR spectra of compounds 8 and
and the C1-symmetrical isomer 9 in apparently quantitative 9 are very similar, their isomer ratio can be determined from the
yield. More recently, this method was also successfully applied mixture by assuming incremental deshielding effects caused by
to the analogous nitration of compound 2 [22].
the nitro group placed at the benzene ring which is adjacent to
that bearing the proton under observation. Thus, besides the
Our attempts to separate the two constitutional isomers 8 and 9 strong deshielding effect due to the ortho-NO2 groups of the
by gravity column chromatography failed due to their almost very same benzene ring, the “distal” or “proximal” nitro group
identical elution behaviour. However, 1H NMR spectroscopy of at the closest neighbouring ring affects the chemical shift. For
the mixture allowed us to determine the ratio of the isomers in example, the resonance of the (“isolated”) ortho-proton 1-H of
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Scheme 1: Nitration of tetramethyl-TBTQ 3 to give a 1:3 mixture of the trinitro derivatives 8 and 9, and subsequent reduction of the mixture, yielding
the TBTQ triamines 10 and 11. Reagents, conditions and yields: (i) NaNO3, TFA, 25 °C, 48 h, quantitative. (ii) N2H4 · H2O (96%), FeCl3 · 6 H2O, char-
coal, 80 °C, 24 h, 81%. Alternatively: (ii) H2, Pd/C, EtOH, 5 bar, 20 °C, 24 h, 91%; yields after chromatography 20% (10) and 70% (11).
isomer 8 (Ha, δ 8.19) is also affected to a minor extent by the fact, the unity integral ratios observed for the six different reso-
distal 10-NO2 group. The equivalent protons 5-Ha and 9-Ha of nances a and a’, b and b’, and c and c’ are in excellent agree-
8 suffer the same extra chemical shift but, interestingly, the ment with the assumed isomer ratio 8:9 = 25:75: With this ratio,
isolated proton 5-Ha of isomer 9 is also isochronous and the integrals of the groups of isochronous protons, e.g., Ha in 8
contributes to the doublet (4J = 2.0 Hz) at δ 8.19. By contrast, and 9 and Ha’ in 9, become equal: [Ha] = 0.25 × 3 + 0.75 × 1 =
the remaining isolated ortho-protons, 1-H and 12-H, of isomer 9 [Ha’] = 0.75 × 2 = 1.50. Finally, it may be noted that, accord-
resonate at slightly lower field (Ha’, δ 8.24) due to the stronger ingly, the 1:3 mixture of the trinitro compounds 8 and 9 is also
deshielding effect of the proximal 11-NO2 and 2-NO2 groups, reflected by three 13C NMR lines at δ 25.54, 25.46 and 25.40 in
respectively. Correspondingly, this significant difference in the the intensity ratio of ca. 3:6:3.
chemical shifts (Δδ = 0.05 ppm) of protons Ha and Ha’ of
isomers 8 and 9 is found to occur inversely with the resonances Reduction of the mixture of the trinitro compounds 8 and 9 was
of the non-isolated ortho-protons Hc and Hc’, and appear as in the first instance achieved by use of hydrazine with iron(III)
doublets (3J = 8.5 Hz) at δ 7.57 and δ 7.50, respectively. Thus, chloride and charcoal in refluxing methanol (Scheme 1) [23],
the former resonance is assigned to the equivalent protons 4-Hc, and afforded a mixture of the triamino-TBTQs 10 and 11 in
9-Hc and 12-Hc of 8 and the isochronous proton 4-Hc of 9, all good yield (81%). However, catalytic hydrogenolysis of com-
having one proximal nitro group at the adjacent benzene ring. pounds 8 and 9 at ambient temperature under medium pressure
The latter resonance assigned to the isochronous protons 8-Hc’ [20,24,25] proved to be even more efficient and gave the
and 9-Hc’ is slightly upfield-shifted (Δδ = 0.07 ppm) due to the TBTQ-trianilines 10 and 11 in an even higher yield (91%). At
weaker deshielding effect of the respective distal 11-NO2 and variance from the trinitrotribenzotriquinacenes, these deriva-
6-NO2 groups. Similar arguments hold true for the meta-protons tives were found to display quite different elution behaviour on
Hb and Hb’ of the TBTQ skeleton, with a noticeably slight silica gel. By use of ethyl acetate as an eluent, the retention
perturbation in the case of Hb due to the asymmetry of 9. In factors of 10 and 11 were found to be 0.44 and 0.27. After sep-
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Figure 2: Partial 1H NMR spectrum (500 MHz, CDCl3) of the mixture of the trinitro-TBTQ isomers 8 and 9.
aration by column chromatography, the first-eluting, tively sharp singlet at δ 6.59, all of which having unity integral
C3-symmetrical isomer 10 was obtained in 20% and the second- ratios. As expected, the chemical shifts in the spectrum of the
eluting, C1-symmetrical isomer 11 in 70% yields, in line with C1-symmetrical isomer 11 are very similar to those of 10 but
the isomer ratio deduced for the trinitro precursors.
very slight differences of the chemical shifts are evident from
the significantly broadened and more complex signals. Notably,
Similar to the trinitro compounds 8 and 9, the triamines 10 and these differences are much less pronounced as was the case
11 were found to give apparently identical EI mass spectra. In with the trinitro precursors; thus, the splitting of the resonances
all of these cases, loss of a methyl radical is, by far, the domi- of the isolated protons 1-H, 5-H and 12-H of isomer 11 into two
nating primary fragmentation process. However, 1H and singlets at δ 6.59 (1H) and δ 6.61 (2H) is minute. Moreover, and
13C NMR spectroscopy allowed us to unequivocally assign the quite specifically, the proton-decoupled 13C NMR spectrum of
isomers. The C3-symmetry of compound 10 is reflected by the the C3-symmetrical isomer 10 exhibits a single line at δ 61.7
relatively well resolved doublets at δ 6.47 and 7.06 and the rela- due to the three benzhydrylic bridgeheads and another line
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Beilstein J. Org. Chem. 2011, 7, 329–337.
at δ 25.9 due to the three methyl groups attached to these posi- of the C3-symmetrical 5 isomer exhibited two characteristic
tions, whereas the spectrum of 11 shows two sets of three singlets at δ 8.54 and δ 8.60 for the two sets of amido protons.
lines at δ 61.1, 61.7 and 62.2 and at δ 25.7, 25.9 and 26.1, res- 1H,1H-COSY measurements allowed us to assign these reso-
pectively.
nances to the “outer” (Ph–NHCO) and the “inner”
(TBTQ–NHCO) amido protons, respectively, of the three
The triamino-substituted TBTQs 10 and 11 readily added three equivalent urea groups. In fact, the singlet for the adjacent
equivalents of phenylisocyanate to give the corresponding C3- protons, 1-H, 5-H and 9-H (δ 7.55), at the TBTQ nucleus, as
and C1-symmetrical TBTQ-based tris-ureas 5 and 6 in very well as the doublet for the six ortho-protons of the phenyl
good yields (Scheme 2). These conversions were as efficient as groups (δ 7.43), were found to be useful for this assignment.
the corresponding reactions of the tetraaminocalix[4]arenes The three equivalent bridgehead methyl groups of 5 resonate at
[10]. As expected, the colorless amorphous solids had good δ 1.57 and those of the central methyl group appear at δ 1.30.
solubility in polar solvents but not in non-polar ones. Whereas
EI and DEI mass spectrometry failed, ionization by FAB(+) Although the bridgehead chemistry of the tribenzotriquin-
furnished almost identical mass spectra that clearly showed the acenes has been extensively investigated [1-4,7], the attach-
expected [M + H]+ peaks at m/z 739 along with very minor ment of multifunctional groupings at the convex surface of the
signals for the twofold condensation product. However, the TBTQ skeleton has been only scarcely examined [4]. Therefore,
1H NMR spectra of compounds 5 and 6 gave no hint to such we subjected the previously described bridgehead triaminotri-
impurities.
benzotriquinacene 12 [4] to the reaction with phenylisocyanate
in analogy to the conversion of the peripheral triamines 10 and
In analogy to the triamino precursors 10 and 11, the TBTQ-tris- 11, and isolated the corresponding C3v-symmetrical TBTQ tris-
ureas 5 and 6 gave very similar 1H NMR spectra even at urea 7 in very good yield (Scheme 2). Again, characterization
600 MHz but, again, the spectrum of the non-symmetrical 6 by FAB(+) and also by ESI(+) mass spectrometry was straight-
isomer revealed significant splitting of the peaks. The spectrum forward; intense [M + H]+ (m/z 697) and, respectively,
Scheme 2: Syntheses of tris-phenylurea-substituted tribenzotriquinacenes 5–7. Reagents and conditions: (i) PhNCO, CHCl3, 50 °C, 6 h, 84%. (ii)
ditto, 86%. (iii) ditto, 96%.
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Beilstein J. Org. Chem. 2011, 7, 329–337.
[M + Na]+ (m/z 719) peaks were in accord with the product of It is noteworthy that the 1H resonance of the central methyl
threefold addition. Interestingly, the 1H NMR spectra of com- group is hardly affected by the solvent, whereas the resonance
pound 7 showed pronounced solvent effects on the NH proton of the outer bridgehead methyl groups is shifted to a higher
resonances. The outer protons were found to resonate at δ 8.86 field by Δδ ≈ 0.4 ppm for the C3-symmetrical compound 5 and
in DMSO-d6 but at δ 6.80 in C2D2Cl4, and the inner protons by even Δδ ≈ 0.5 ppm for the C1-symmetrical compound 5.
to resonate at δ 6.57 in DMSO-d6 and at δ 5.37 in C2D2Cl4. Similar to the argument mentioned above for compound 7, this
Thus, the change from the polar to the low-polarity solvent effect could be attributed to the shielding effect exerted by the
gives rise to a high-field shifts of Δδ = 2.3 and 1.4 ppm, respect- arene units of the TBTQ core belonging to the opposite mole-
ively. This effect was attributed to the preferred formation of cule associated in face-to-face dimers of either 5 or 6. Notably,
hydrogen-bound dimers of the tris-urea 7 in tetrachloroethane however, and in contrast to the case of compound 7, the TBTQ
solution.
molecules in such dimers would be aggregated with their
concave sides toward each other.
As outlined above, the potential dimerization of the threefold
urea-functionalized TBTQ derivatives 5, 6 and 7 was one motif Finally, it should be noted that all of the FAB(+) and ESI(+)
for this work. In fact, some evidence for the formation of mass spectra recorded with compounds 5, 6 and 7 exhibited
neutral dimers in low-polarity solvents was found. As strong signals for dimeric quasi-molecular ions. For example,
mentioned above, the strong high-field shift observed in the ESI(+) mass spectrum of the C1-symmetrical isomer 6
dichloroethane solution for the NH protons of the bridgehead obtained from pure methanol solution exhibited the ions
TBTQ tris-urea 7 suggests the formation of a dimeric aggregate. [M + Na]+ (m/z 761) and [2 M + Na]+ (m/z 1499) in the abun-
Specifically, the particularly strong shielding of the external NH dance ratio of ca. 100:20. About the same ratio was found when
protons (Δδ = −2.3) may point to the formation of face-to-face a chloroform/methanol mixture (99:1) was used. By contrast,
dimers in which the arene units of the opposite TBTQ core the C3-symmetrical isomer 5 sprayed from the latter solvent
exert pronounced magnetic anisotropy effects.
gave ESI(+) mass spectra that reproducibly show abundant
peaks for (singly charged) [M + 2 Na]+ (m/z 784) and [2 M +
In the case of the peripheral TBTQ tris-ureas 5 and 6, 1H NMR 2 Na]+ ions. This difference may be due to the different molec-
measurements in DMSO and tetrachloroethane revealed a ular symmetry. The FAB(+) mass spectrum of the bridgehead
surprising effect which may also be attributed to aggregation of tris-urea 7 (obtained with NBA as a matrix) and the corres-
these molecules in low-polarity solvents. Both of these com- ponding ESI(+) mass spectrum obtained from pure methanol
pounds were found to be only poorly soluble in C2D2Cl4 and exhibited the [M + H]+ (m/z 697) and the [M + Na]+ (m/z 719)
their 1H NMR spectra in this solvent showed very broad signals peaks, respectively, but only very minor dimeric quasi-molec-
for the NH protons. Therefore, assignment of NH and arene ular ion peaks.
proton resonances was impossible even at elevated tempera-
tures (≤ 120 °C). Nevertheless, the 1H resonances of the three No more detailed analysis of the dimerization of the new
benzhydrylic and the single central methyl groups were clearly TBTQ-based tris-urea 5, 6, and 7 has been carried out so far.
detectable in both DMSO-d6 and C2D2Cl4. However, in the Also, it remains open whether homo- or heterochiral associ-
latter solvent, the protons of the benzhydrylic methyl groups of ation is preferred with the peripheral tris-urea 5 and 6 and
5 and 6 were found to resonate at significantly higher fields whether the C3-symmetrical isomer 5 behaves differently from
than those of the central methyl group (Table 1). This is in stark the C1-symmetrical isomer 6. Nevertheless, the observations
contrast to the relative chemical shifts found with DMSO-d6 as reported in the present work point to the existence of TBTQ
a solvent and with all TBTQ derivatives studied so far.
tris-urea dimers in non-polar solvents. Congeners bearing three
longer-chain aliphatic groups in place of the phenylcarbamoyl
residues appear to be good candidates for further studies in this
field.
Table 1: Solvent effect on the chemical shifts (δ) observed in the
1H NMR spectra (500 MHz) of the central (12d-) and the outer bridge-
head (4b-, 8b-, 12b-) methyl groups of compounds 5 and 6.
Compound Bridgehead methyl
groups
Solvent
Experimental
DMSO-d6 C2D2Cl4
2,6,10-Trinitro-4b,8b,12b,12d-tetramethyl-4b,8b,12b,12d-
tetrahydrodibenzo-[2,3:4,5]pentaleno[1,6-ab]indene (8) and
2,6,11-trinitro-4b,8b,12b,12d-tetramethyl-4b,8b,12b,12d-
tetrahydrodibenzo[2,3:4,5]-pentaleno-[1,6-ab]indene (9)
(mixture of isomers). A suspension of tetramethyltriben-
zotriquinacene 3 (250 mg, 743 mmol) in trifluoroacetic acid
5
6
12d-CH3
1.30
1.57
1.30
1.56
1.34
1.17
1.26
1.07
4b-, 8b-, 12b-CH3
12d-CH3
4b-, 8b-, 12b-CH3
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Beilstein J. Org. Chem. 2011, 7, 329–337.
(40 mL) was stirred while sodium nitrate (756 mg, 8.92 mmol) and the C1-symmetrical isomer 11 (399 mg, 70%). Isomer 10:
was added in small portions. The reaction mixture became a Rf (EtOAc) 0.44; mp 344 °C; IR (KBr): ν = 3445, 3372, 3208,
yellow solution after several hours and stirring was continued 3013, 2960, 2927, 2866, 1619, 1494, 1449, 1434, 1389, 1370,
for a total of 48 h at ambient temperature. After the addition of 1313, 1276, 1258, 1238, 1188, 1157, 1137, 1078, 1028, 926,
water (25 mL), the mixture was cooled with ice and the pH 857, 815, 756, 708, 613 cm−1; 1H NMR (500 MHz, CDCl3): δ =
adjusted to ≈10 by the careful addition of sodium hydroxide 7.06 (d, J = 8.0 Hz, 3H), 6.59 (s, 3H), 6.47 (d, J = 7.4 Hz, 3H),
(solid or 6 M aqueous solution). Repeated extraction with chlo- 3.45 (br s, 6H), 1.53 (s, 9H), 1.27 (s, 3H); 13C NMR (125 MHz,
roform, drying of the combined extracts with sodium sulfate CDCl3): δ = 150.7, 145.9, 139.2 (all C), 123.3, 115.1, 109.1 (all
and removal of the solvent under reduced pressure followed by CH), 70.6 (C), 61.7 (C), 25.9 (CH3), 16.1 (CH3); MS (EI,
column chromatography (silica gel/CHCl3) gave a mixture of 70 eV) m/z (%): 381 (26) [M+•], 366 (100), 351 (5), 336 (9),
the trinitro compounds 8 and 9 (350 mg, 100%) in a ratio of 319 (5); accurate mass (EI, 70 eV): C26H27N3 (M+•), calcd
ca. 1:3 as a yellow, amorphous solid; Rf (CHCl3) 0.74; mp 381.2205, found 381.2206. Isomer 11: Rf (EtOAc) 0.27;
>360 °C; IR (KBr): ν = 3073, 2974, 2934, 1594, 1530, 1475, mp 339 °C; IR (KBr): ν = 3454, 3374, 3216, 3014, 2961, 2929,
1453, 1396, 1345, 1207, 1153, 1112, 1097, 1067, 1032, 907, 2864, 1618, 1490, 1453, 1434, 1392, 1371, 1311, 1266, 1245,
887, 825, 742, 674 cm−1; 1H NMR (500 MHz, CDCl3), integral 1183, 1156, 1133, 1077, 1027, 931, 860, 814, 753 cm−1;
data given as parts of a total of 9 Har and 12 Hme: δ = 8.240 (d, 1H NMR (500 MHz, CDCl3): δ = 7.09–7.03 (m, 3H), 6.61 (s,
J = 2.1 Hz, 1.5 Har), 8.193 (d, J = 2.1 Hz, 1.5 Har), 8.125 (d, 2H), 6.59 (s, 1H), 6.49–6.42 (m, 3H), 3.41 (br s, 6H), 1.53 (s,
J ≈ 8.5 Hz, with fine splitting of J ≈ 1.9 Hz, 1.5 Har), 8.105 (br 9H), 1.27 (s, 3H); 13C NMR (125 MHz, CDCl3): δ = 150.3,
d, J ≈ 8.5 Hz, 1.5 Har), 7.575 (d, J = 8.5 Hz, 1.5 Har), 7.506 (d, 150.0, 149.6, 145.8, 145.7, 145.6, 140.3, 139.9, 139.6 (all C),
J = 8.5 Hz, 1.5 Har), 1.77 (s, 2.25 Hme), 1.75 (s, 4.5 Hme), 1.73 123.4, 123.22, 123.19, 115.4, 115.3, 115.2, 109.3, 109.1 (all
(s, 2.25 Hme), 1.43 (s, 3Hme); 13C NMR (75 MHz, acetone-d6): CH), 70.6, 62.2, 61.7, 61.1 (all C), 26.1, 25.9, 25.7, 16.1 (all
δ = 155.9, 155.6, 150.8, 150.7, 149.9 (all C), 125.6, 124.8, CH3); MS (EI, 70 eV) m/z (%): 381 (20) [M+•], 366 (100), 351
124.7, 119.7 (all CH), 72.3, 64.1, 63.94, 63.86 (all C), 25.54, (4), 336 (8), 319 (4); accurate mass (EI, 70 eV): C26H27N3
25.46, 25.4, 16.1 (all CH3); MS (EI, 70 eV) m/z (%): 471 (9) (M+•), calcd 381.2205, found 381.2204.
[M+•], 456 (100), 410 (9), 395 (7); accurate mass (EI, 70 eV):
m/z 456 ([M – CH3]+), C25H18N3O6, calcd 456.1196; found 2,6,10-Tris[(N-phenylcarbamoyl)amino]-4b,8b,12b,12d-te-
456.1196.
t r a m e t h y l - 4 b , 8 b , 1 2 b , 1 2 d - t e t r a h y d r o d i b e n z o -
[2,3:4,5]pentaleno[1,6-ab]indene (5). A solution of the
2,6,10-Triamino-4b,8b,12b,12d-tetramethyl-4b,8b,12b,12d- triamino-TBTQ 10 (115 mg, 302 μmol) in anhydrous chloro-
tetrahydrodibenzo-[2,3:4,5]pentaleno[1,6-ab]indene (10) form (70 mL) was stirred under an argon atmosphere while
and 2,6,11-triamino-4b,8b,12b,12d-tetramethyl- phenylisocyanate (108 μL, 995 μmol) was added. The mixture
4b,8b,12b,12d-tetrahydrodibenzo[2,3:4,5]pentaleno[1,6- was heated at 50 °C for 6 h and the solvent was removed under
ab]indene (11). Procedure A. A suspension containing the mix- reduced pressure. The colorless solid residue was suspended in
ture of isomeric trinitrotribenzotriquinacenes 8 and 9 described n-hexane, filtered by suction and dried in vacuo to give the tris-
above (230 mg, 488 mmol), charcoal (32 mg) and iron(III) chlo- urea 5 (187 mg, 84%) as a colorless amorphous solid, mp
ride hexahydrate (10 mg) in methanol (10 mL) was heated to >360 °C; IR (KBr): ν = 3372, 2968, 2928, 1663, 1598, 1546,
reflux for 15 min and then hydrazine hydrate (97%, 120 mg) 1491, 1443, 1416, 1372, 1311, 1227, 1080, 752, 692 cm−1;
added. After heating for 4 h further FeCl3•6H2O (10 mg) and 1H NMR (500 MHz, DMSO-d6), see Supporting Information
120 mg N2H4•H2O (120 mg) were added. The mixture was File 1 for 600 MHz spectrum: δ = 8.60 (s, 3H), 8.54 (s, 3H),
heated under reflux for a total of 24 h, allowed to cool and 7.55 (d, J = 1.4 Hz, 3H), 7.43 (d, J = 8.0 Hz, 6H), 7.26 (t, J =
filtered through silica with ethyl acetate. Removal of the solvent 7.9 Hz, 9H), 7.18 (dd, 3J = 8.4 Hz, 4J = 1.4 Hz, 3H), 6.94 (t, J =
gave a mixture of the triamines 10 and 11 (151 mg, 81%) as a 7.4 Hz, 3H), 1.57 (s, 9H), 1.30 (s, 3H); 13C NMR (125 MHz,
yellow solid, the components of which can be separated by DMSO-d6): δ = 152.6, 149.5, 142.1, 139.8, 139.1 (all C), 128.8,
chromatography. Procedure B. The mixture of isomers 8 and 9 122.8, 121.8, 118.2, 112.6 (all CH), 69.9 (C), 61.7 (C), 25.5
described above (500 mg, 1.06 mmol) and Pd/C (10%, 100 mg) (CH3). The 12d-CH3 group does not show a separate resonance.
were suspended in ethanol (100 mL) and shaken under a 1H NMR (500 MHz, C2D2Cl4): δ = 7.30–6.90 (m, 30H), 1.34
hydrogen atmosphere at 5 bar at ambient temperature for 24 h. (s, 3H), 1.17 (s, 9H); MS (FAB(+), NBA) m/z (%): 1479 (1)
The catalyst was removed by filtration through silica gel and the [2 M + H]+, 739 (97) [M + H]+, 723 (19); MS [ESI(+), MeOH]
solvent removed under reduced pressure. The triamines 10 and m/z (%): 1499.8 (8) [2 M + Na]+, 1358.7 (6), 761.3 (100)
11 were separated by column chromatography (silica gel, [M + Na]+, 756.4 (19), 739.3 (12), 642.3 (25), 620.3 (28); MS
EtOAc) to yield the C3-symmetrical isomer 10 (115 mg, 20%) [ESI(+), CHCl3 and ~1% MeOH] m/z (%): 1565.8 (1), 1523.8
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Beilstein J. Org. Chem. 2011, 7, 329–337.
(7) [2 M + 2 Na]+, 1500.8 (1), 1403.8 (1), 1358.7 (1), 826.4 1542, 1498, 1441, 1351, 1311, 1237, 751, 692, 663 cm−1;
(25), 784.4 (100) [M + 2 Na]+, 757.4 (19), 665.4 (68); MS 1H NMR (500 MHz, DMSO-d6), see Supporting Information
[ESI(+), MeOH, (CH3)4NPF6] m/z (%): 1551.9 (2) [2 M + File 1 for 600 MHz spectrum: δ = 8.86 (s, 3H), 7.56 and 7.24
(CH3)4N]+, 812.5 (100) [M + (CH3)4N]+, 761.3 (46), 680.1 (AA’BB’, 12H), 7.28 (d, J = 7.9 Hz, 6H), 7.15 (t, J = 7.7 Hz,
(52), 620.3 (12); combustional analysis: C47H42N6O3•H2O 6H), 6.84 (t, J = 7.4 Hz, 3H), 6.80 (s, 3H), 1.62 (s, 3H);
calcd C 74.58, H 5.86, N 11.10, found C 74.57, H 6.09, 13C NMR (125 MHz, DMSO-d6): δ = 154.2, 144.6, 140.4 (all
N 10.98.
C), 128.6, 128.3, 123.5, 120.9, 117.3 (all CH), 77.1 (C), 76.9
(C), 12.9 (CH3); 1H NMR (500 MHz, C2D2Cl4, 120 °C): δ =
2,6,11-Tris[(N-phenylcarbamoyl)amino]-4b,8b,12b,12d- 7.49 and 7.26 (AA’BB’, 12H), 7.17 (br s, 12H), 7.00 (m, 3H),
tetramethyl-4b,8b,12b,12d-tetrahydrodibenzo- 6.57 (s, 3H), 5.37 (s, 3H), 1.71 (s, 3H); MS [FAB(+), NBA]
[2,3:4,5]pentaleno[1,6-ab]indene (6). In analogy to the proce- m/z (%): 1394 (2) [2 M + H]+, 697 (100) [M + H]+, 561 (78),
dure given above, triaminotribenzotriquinacene 11 (104 μg, 426 (14); MS [ESI(+), MeOH] m/z (%): 1415.7 (2) [2 M +
273 μmol) was dissolved in anhydrous chloroform (70 mL) Na]+, 1394.6 (1), 1274.6 (1), 1072.9 (1), 719.2 (100)
and reacted with phenylisocyanate (98 μL, 901 μmol) under [M + Na]+, 697.3 (7), 561.2 (15); MS [ESI(+), MeOH,
argon. The mixture was heated at 50 °C for 6 h and then treated (CH3)4NPF6)] m/z (%): 1467.7 (1) [2 M + (CH3)4N]+, 1416.7
as above to yield the tris-urea 6 (173 mg, 86%) as a colorless, (1), 1393.7 (1), 770.3 (20) [M + (CH3)4N]+, 719.2 (100), 697.3
amorphous solid, mp 257 °C (decomp.); IR (KBr): ν = 3381, (52), 561.2 (90); combustional analysis: C44H36N6O3 calcd C
2968, 2928, 1664, 1598, 1549, 1491, 1443, 1415, 1372, 1311, 75.84, H 5.21, N 12.06, found C 75.72, H 5.44, N 12.09; accu-
1227, 1079, 752, 692 cm−1; 1H NMR (500 MHz, DMSO-d6), rate mass [ESI(+)]: [C44H36N6O3Na]+ calcd 719.2747, found
see Supporting Information File 1 for 600 MHz spectrum: δ = 719.2728.
8.62 (s, 1H), 8.60 (s, 2H), 8.57 (s, 1H), 8.56 (s, 1H), 8.54 (s,
1H), 7.53 (d, J = 1.4 Hz, 1H), 7.49 (d, J = 1.3 Hz, 1H), 7.46 (d,
Supporting Information
J = 1.4 Hz, 1H), 7.42 (d, J = 7.9 Hz, 6H), 7.38 (d, J = 8.4 Hz,
1H), 7.37 (d, J = 8.3 Hz, 1H), 7.25 (m, 9H), 7.16 (dd, J =
Supporting Information File 1
8.3 Hz, J = 1.5 Hz, 1H), 6.94 (t, J = 7.3 Hz, 3H), 1.56 (s, 9H),
1.30 (s, 3H). 13C NMR (125 MHz, DMSO-d6): δ = 152.6,
149.2, 149.0, 148.7, 142.9, 142.6, 142.4, 139.7, 139.1, 139.0
(all C), 128.7, 123.1, 123.0, 122.9, 121.7, 118.4, 118.2, 112.5,
112.4, 112.3 (all CH), 69.9, 62.2, 61.7, 61.3 (all C), 25.6 (CH3),
15.8 (CH3); 1H NMR (500 MHz, C2D2Cl4): δ = 7.32 (br s),
7.22 (br s), 7.20 (br s), 7.19 (br s), 7.03 (br s), 7.00 (br s), 6.91
(br s), 1.26 (br s, 3H), 1.07 (br s, 9H); MS [FAB(+), NBA]
m/z (%): 1478 (2) [2 M + H]+, 739 (73) [M + H]+, 723 (7); MS
[ESI(+), MeOH] m/z (%): 1500.6 (19) [2 M + Na]+, 1136.4 (4),
767.3 (9), 761.3 (100) [M + Na]+, 756.3 (28), 739.3 (12), 670.3
(6), 620.3 (7); MS [ESI(+), CHCl3 and ~1% MeOH] m/z (%):
1500.7 (9) [2 M + Na]+, 761.4 (100) [M + Na]+; MS [ESI(+),
MeOH, (CH3)4NPF6] m/z (%): 1551.8 (5) [2 M + (CH3)4N]+,
1499.6 (5), 848.6 (17), 812.4 (70) [M + (CH3)4N]+, 761.3 (76),
756.3 (100), 739.3 (54), 663.4 (20), 620.3 (27), 529.4 (30);
combustional analysis: C47H42N6O3•H2O calcd C 74.58,
H 5.86, N 11.10, found C 74.51, H 5.92, N 10.92.
1H NMR spectra including magnifications of compounds 5,
6 and 7 (600 MHz) and of compounds 8, 9, 10 and 11 (500
MHz).
[http://www.beilstein-journals.org/bjoc/content/
supplementary/1860-5397-7-43-S1.pdf]
Acknowledgements
We would like to thank Dr. H. Luftmann, University of
Münster, and Dr. M. Letzel, Bielefeld University, for recording
the ESI mass spectra of compounds 5–7.
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