A facile approach for new dibenzo [b,f][1,5] diazocinones

Article abstract of DOI:10.1081/SCC-200057990

The synthesis of new eight-membered cycle dibenzo[b,f][1,5]-diazocine-6- (5W)-one derivatives 11, 12 was developed. The key step in this synthesis was the intramolecular cyclization of the amino aldehyde precursors 9, 10 obtained by a selective reduction

Full text of DOI:10.1081/SCC-200057990

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A Facile Approach for
New Dibenzo [b,f][1,5]
Diazocinones
Hernán Pessoa‐Mahana a , Karen G. Martínez
Aránguiz a , Ramiro Araya‐Maturana a & C. David
Pessoa‐Mahana b
a Departamento de Química Orgánica y
Fisicoquímica, Facultad de Ciencias Químicas y
Farmacéuticas, Universidad de Chile, Santiago, Chile
b Departamento de Farmacia, Pontificia Universidad
Católica de Chile, Santiago, Chile
Version of record first published: 17 Dec 2010
To cite this article: Hernán Pessoa‐Mahana, Karen G. Martínez Aránguiz, Ramiro
Araya‐Maturana & C. David Pessoa‐Mahana (2005): A Facile Approach for New Dibenzo
[b,f][1,5] Diazocinones, Synthetic Communications: An International Journal for Rapid
Communication of Synthetic Organic Chemistry, 35:11, 1493-1500
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Synthetic Communicationsw, 35: 1493–1500, 2005
Copyright # Taylor & Francis, Inc.
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1081/SCC-200057990
A Facile Approach for New Dibenzo
[b,f][1,5] Diazocinones
´ ´
´
Hernan Pessoa-Mahana, Karen G. Martınez Aranguiz, and
Ramiro Araya-Maturana
´ ´ ´
Departamento de Quımica Organica y Fisicoquımica, Facultad de
´ ´
Ciencias Quımicas y Farmaceuticas, Universidad de Chile,
Santiago, Chile
C. David Pessoa-Mahana
Departamento de Farmacia, Pontificia Universidad Catolica de Chile,
Santiago, Chile
´
Abstract: The synthesis of new eight-membered cycle dibenzo[b,f][1,5]-diazocine-6-
(5H)-one derivatives 11, 12 was developed. The key step in this synthesis was the intra-
molecular cyclization of the amino aldehyde precursors 9,10 obtained by a selective
reduction of the nitro benzamides 7, 8.
¨
Keywords: Dibenzodiazocinones, Troger’s base, nitroaldehydes
INTRODUCTION
Troger’s base,[1–3] 2,8-dimethyl-6H,12H-5,11-methanodibenzo [b,f] [1,5]-
diazocine I is a chiral rigid molecule that has attracted much attention
mainly because of its interesting biological activities, such as host in recog-
nition phenomena,[4] DNA intercalation,[5] enzyme inhibition, and as a
ligand for asymmetric catalysis.[6] In this field the dibenzodiazocinic
skeleton[7–9] has gained considerable interest as a challenging target and
pharmacologically interesting compound. Recently Hassner et al.[10]
Received in the USA January 27, 2005
´ ´
Address correspondence to Hernan Pessoa-Mahana, Departamento de Quımica
´
´ ´
Organica y Fisicoquımica, Facultad de Ciencias Quımicas y Farmaceuticas, Universi-
´
dad de Chile, Casilla 233, Santiago 1, Chile. E-mail: hpessoa@ciq.uchile.cl
1493

1494
H. Pessoa-Mahana et al.
reported the synthesis of dibenzodiazocinedione II, the first substituted asym-
metrical dilactam by reaction of a sulfinamide lactone of anthranilic acid with
different N-alkyl anthranilic acids. On the other hand, reactivity studies
reported by Wakankar and Hosangadi[11] on dibenzodiazocine III demon-
strated the flexibility and the applications of the dibenzodiazocine
framework. However, as far as we know, the synthesis of dibenzodiazocinones
of type IV has not been reported yet.
In a previous work by our group, a versatile approach for obtaining
Troger’s base precursors from easily available 2-nitrobenzaldehyde and
2-aminobenzyl alcohol was described.[12] Based on these results and given
our interest in the azaheterocyclic chemistry, we decided to explore the
synthesis of the diazocinone IV.
In this article, we report a convenient synthetic method for the preparation
of novel dibenzo [b,f][1,5] diazocinones 11 and 12, following a four-step
reaction sequence.
RESULTS AND DISCUSSION
The general strategy is depicted in Scheme 1. Benzoyl halides 3, 4 were
prepared in quantitative yield from the corresponding carboxylic acids 1
and 2 by refluxing in thionyl chloride at 508C for 3 h. The resulting oils
were characterized by IR (1795 and 1797 cm21) and, without further purifi-
cation, immediately reacted with 2-aminobenzylic alcohol under an inert
atmosphere at 08C to give the expected benzamide alcohols 5 (83%) and 6
(87%), respectively. Subsequent oxidation of alcohol derivatives 5 and 6
with pyridinium chlorochromate in dichloromethane at room temperature
provided the corresponding nitroaldehydes 7 and 8 in high yield. The
aldehydes were easily purified by silica-gel column chromatography,
showing in the 1H-NMR spectra the characteristic singlet signals at low
field: (7dCHO ¼ 10.1 ppm and 8 dCHO ¼ 9.93 ppm), supporting the presence
of these functions. The key and final step of this synthesis consisted of a

Dibenzo [b,f][1,5] Diazocinones
1495
Scheme 1. Reagents: a) SOCl2, 50 8C (3 h); b) 2-aminobenzyl alcohol, anhydrous
THF, dry pyridine, N2 atmosphere; c) pyridinium chlorochromate/CH2Cl2 25 8C;
d) Fe8/H2O, EtOH, HOAc (1:1:1 v/v), 20 8C.
chemoselective nitroreduction of nitro aldehydes 7, 8, which was carried out
under diluted conditions with iron powder, in ethanolic, aqueous, acetic acid
medium.[13] The reaction afforded a mixture of amine aldehyde intermediates
9, 10 along with the desired cyclized products 11, 12 (Scheme 1) as was
1
detected by the H-NMR spectral analysis of the crude mixtures.
The presence of the aminoaldehydes 9 and 10, together with the cyclized
products 11, 12 in the crude reduction mixture, is not dependent on the
reduction time, as we confirmed by utilizing longer reduction times, but
probably results from the acidic, aqueous medium of the reaction, which
might promote imine hydrolysis and ring opening as is illustrated in Scheme 2.
Compounds 9, 11, and 12 were purified by chromatography, followed by
recrystallization, except for the amine aldehyde intermediate 10, which could
not be isolated from the crude product mixture.

1496
H. Pessoa-Mahana et al.
Scheme 2.
In summary, the present study provides a simple and short method for the
preparation of new benzofused eight-membered diazaheterocycles from easily
available reagents.
EXPERIMENTAL
All reagents were obtained commercially and used without further purification.
Melting points were measured on a Kofler hot-stage apparatus and are uncor-
rected. IR spectra were recorded with a FT Bruker spectrophotometer for
KBr. 1H-NMR and 13C-NMR spectra were obtained with a Bruker DRX-300
spectrophotometer. The chemical shifts are expressed in ppm (d scale)
downfield from TMS, J values are given in Hertz for solutions in CDCl3
unless otherwise indicated. Microanalysis were determined on a Fisons EA
1108 analyzer. Silica gel Merck 60 (70–230 mesh) and DC-alufolien 60 F254
were normally used for column and TLC chromatography respectively.
General Procedure for Preparation of N-[2-(hydroxymethyl) aryl]
nitrobenzamide Derivatives (5, 6) using Compound (5) as a Model
N-[2-(Hydroxymethyl) phenyl]-3,6-dimethoxy-2-nitrobenzamide (5).
Benzoylchloride 3 (1.02 g, 4.39 mmol) in dry THF (30 mL) was slowly added
to a stirred solution at 0 8C of 2-aminobenzyl alcohol (541 mg, 4.39 mmol),
pyridine (348 mg, 4.39 mmol), and dry THF (80 mL) in a nitrogen atmosphere.
The mixture was maintained with stirring for 8 h at room temperature and then
diluted with water (100 mL). The solution was extracted with ethyl acetate
(3 ꢀ 50 mL) and the organic layers dried over MgSO4. Concentration of the
solvent in vacuo afforded a residue, which was purified by silica-gel column
chromatography (AcOEt/CH2Cl2, 1:1) to give dimethoxy nitrobenzamide 5
(1.21 g, 83%) as a yellow pale solid. Mp 108–109 8C (EtOH/hexane 3:1).
Anal. calcd. for C16H16N2O6: C, 57.83; H, 4.81; N, 8.43. Found: C, 57.68;
H, 4.99; N, 8.62%. IR nmax: 3433 (O22H), 3300 (N22H), 1646 (NHC55O),
1
1540 (NO2), 1369 (NO2). H-NMR (DMSO-d6) d: 3.89 (s, 3H, OCH3), 3.95

Dibenzo [b,f][1,5] Diazocinones
1497
(s, 3H, OCH3), 4.61 (s, 2H, -CH2-OH), 5.35 (br s 1H, OH), 7.13 (t,1H,
J ¼ 7.3 Hz, Ar 40-H), 7.24–7.38 (m, 4 H, Ar-3H, Ar-4-H, Ar-30-H, Ar-50-
H), 7.84 (d, 1H, J ¼ 7.9 Hz, Ar 60-H), 10.12 (s, 1H, NHCO).13C-NMR
(75 MHz, DMSO-d6) d: 61.8, 62.0, 66.6, 120.1, 121.0, 124.4, 128.1, 129.7,
132.4, 133.0, 138.2, 140.8, 145.1, 149.7, 154.7, 165.1.
N-[(2-Hydroxymethyl) phenyl]-6-nitrobenzamide (6). Compound
(6) (630 mg, 91%), white crystals, was prepared from benzoyl chloride
(4) (472 mg, 2.54 mmol) and 2-aminobenzyl alcohol (313 mg, 2.54 mmol);
mp 169–170 8C (EtOH/hexane 3 : 1). Anal. calcd. for C14H12N2O4: C,
61.76; H, 4.44; N, 10.29. Found: C, 61.43; H, 4.51; N, 10.12%. IR nmax
:
3421 (O22H), 3240 (N22H), 1650 (NHC55O), 1530 (NO2), 1352 (NO2).
1H-NMR (DMSO-d6) d: 4.59 (d, 2H, J ¼ 5.5 Hz, CH2-OH), 5.29 (t,1H,
J ¼ 5.5 Hz, OH), 7.22–7.33 (m, 2H, Ar 40-H and 50-H), 7.51 (m,2H, Ar-60-
H and Ar-30-H), 7.69–7.91 (m, 3H, Ar 4-H, Ar-5-H, and Ar-6-H), 8.14
(d, 1H, J ¼ 8.0 Hz, Ar 3-H), 10.11 (s, 1H, NHCO). 13C-NMR (75 MHz,
DMSO-d6) d: 60.0, 124.8, 125.4, 126.2, 127.4, 127.5, 129.6, 131.5, 133.1,
134.5, 134.6, 136.9, 147.2, 164.8.
General Procedure for Preparation of N-(2-Formylaryl)
Nitrobenzamide Derivatives (7, 8) using Compound (7) as a Model
N-(2-Formylphenyl)-3,6-dimethoxy-2-nitrobenzamide (7). To a well-
stirred solution of alcohol benzamide 5 (300 mg, 0.90 mmol) in CH2Cl2
(50 mL) at rt is added a solution of pyridinium chlorochromate (300 mg,
1.39 mmol) in CH2Cl2 (20 mL). After complete conversion as indicated by
TLC, the reaction mixture was concentrated and chromatographed on silica-
gel column (CHCl3), and yielded nitroaldehyde 7 (200 mg, 67.1%). Mp
195–196 8C (EtOH). Anal. calcd. for C16H14N2O6: C, 58.18; H, 4.27; N,
8.48. Found: C, 57.95; H, 4.34; N, 8.63%. IR nmax: 3242 (N22H), 1686 (Ar-
CHO), 1668 (NHC55O), 1540 (NO2), 1368 (NO2). 1H-NMR (CDCl3)
d: 3.89 (s, 3H, OCH3), 3.97 (s, 3H, OCH3), 7.11 (d, 1H, J ¼ 9.3 Hz, Ar 3-H
or Ar 4-H), 7.16 (d, 1H, J ¼ 9.3 Hz, Ar 4-H or Ar 3-H), 7.29 (t, 1H,
J ¼ 7.5 Hz, Ar 40-H), 7.62 (td, 1H, Jo ¼ 7.3 Hz, Jm ¼ 1.4 Hz, Ar 50-H),
7.70 (dd, 1H, Jo ¼ 7.6 Hz, Jm ¼ 1.54 Hz, Ar 60-H), 8.85 (d, 1H, J ¼ 8.5 Hz,
Ar 30-H), 9.93 (s, 1H, Ar CHO), 11.94 (s, 1H, NHCO). 13C-NMR (75 MHz,
CDCl3) d: 56.7, 57.3, 114.3, 116.5, 118.9, 120.8, 122.4, 123.6, 136.1, 136.2,
139.9, 141.3, 145.4, 150.2, 161.4, 194.9.
N-(2-formylphenyl)-2-nitrobenzamide (8). Compound (8) (253 mg,
86%); white pale solid was prepared from alcohol benzamide (6) (296 mg,
1.08 mmol) and pyridinium chlorochromate (360 mg, 1.67 mmol). Purified
by column chromatography (CH2Cl2/AcOEt 1:1); mp 148–149 8C (EtOH).
Anal. calcd. for C14H10N2O4: C, 62.21; H, 3.73; N, 10.37. Found: C, 62.09;
H, 3.67; N, 10.32%. IR nmax: 3240 (N22H), 1686 (Ar-CHO), 1666
1
(NHC55O), 1530 (NO2), 1350 (NO2). H-NMR (DMSO-d6) d: 7.44 (t,1H,

1498
H. Pessoa-Mahana et al.
J ¼ 7.3 Hz, Ar 40-H), 7.75–7.85 (m, 2H, Ar 4-H, and 50-H), 7.92–7.95
(m, 3H, Ar 5-H, 30-H, and 60-H), 8.03 (d, 1H, J ¼ 7.8 Hz, Ar 6-H), 8.2
(d, 1H, J ¼ 7.9 Hz, Ar 3-H), 10.1 (s, 1H, Ar-CHO), 11.3 (s, 1H, Ar-
NHCO). 13C-NMR (75 MHz, DMSO-d6) d: 123.3, 12.5.1, 125.8, 126.8,
129.5, 132.0, 132.1, 132.3, 134.8, 135.7, 139.5, 147.2, 165.4, 193.5.
General Procedure for Reduction of N-(2-Formylaryl)-2-
nitrobenzamides (7,8) and Reduction of N-(2-Formylphenyl)-3,6-
dimethoxy-2-nitrobenzamide (7)
To a solution of nitrobenzamide (7) (173 mg, 0.52 mmol) in acetic acid–
ethanol–water (100 mL, 1:1:1 v/v) was added powder iron (234 mg,
4.19 mmol). After stirring for 3 h at rt, 50 mL of water was added. The
reaction mixture was neutralized with solid sodium hydrogencarbonate and
extracted with ethyl acetate (3 ꢀ 50 mL). The combined organic layers were
dried (MgSO4) and evaporated to dryness in vacuo to give a crude mixture,
which was purified by column chromatography (CHCl3) to afford two main
fractions. The first fraction provided pure aminoaldehyde (9) (88 mg, 56%).
Mp 113–1148C (AcOEt/hexane 3:1). Anal. calcd. for C16H16N2O4: C,
63.99; H, 5.37; N, 9.33. Found: C, 63.74; H, 5.34; N, 9.29%. IR nmax: 3476
and 3370 (Ar-NH2), 3250 (Ar-NHCO), 1683 (Ar-CHO), 1651 (Ar-
1
NHC55O). H-NMR (CDCl3) d: 3.77 (s, 3H, OMe), 3.91 (s, 3H, OMe), 6.1
(d, 1H, J ¼ 8.7 Hz, Ar 5-H), 6.22 (br s, 2H, Ar-NH2), 6.70 (d, 1H,
J ¼ 8.7 Hz, Ar 4-H), 7.15 (t, 1H, J ¼ 7.5 Hz, Ar 40-H), 7.55 (td, 1H,
Jo ¼ 8.7 Hz,
J
m ¼ 1.7 Hz, Ar 50-H), 7.61 (dd, 1H, Jo ¼ 7.6 Hz,
Jm ¼ 1.6 Hz, Ar-30-H), 8.87 (d, 1H, J ¼ 8.6 Hz, Ar-60-H), 9.9 (s, 1H, Ar-
CHO), 12.2 (s, 1H, Ar-NHCO). 13C-NMR (75 MHz, CDCl3) d: 55.5, 56.1,
95.9, 105.3, 112.2, 121.1, 122.5, 123.0, 135.5, 136.1, 140.6, 141.9, 142.5,
152.6, 167.8, 194.1.
The second fraction isolated from the column provided diazocinone 11:
7,10-Dimethoxy-dibenzo[b,f] [1,5]-diazocine-6-(5H)-one (11). (37 mg,
32%), white powder. Mp 78–80 8C (AcOEt/hexane 3 : 1). Anal. calcd. for
C16H14N2O3: C, 68.08; H, 5.00; N, 9.92. Found: C, 67.74; H, 5.14; N,
9.89%. IR nmax: 3252 (Ar CONH-Ar), 1636 (Ar-CONH-Ar), 1610
1
(Ar-C55N-Ar). H-NMR (CDCl3) d: 3.59 (s, 3H, OMe), 3.85 (s, 3H, OMe),
6.66 (d, 1H, J ¼ 8.9 Hz, Ar 8-H or 9-H), 6.81 (d, 1H, J ¼ 8.9 Hz, Ar-9-H or
8-H), 7.06 (t, 1H, J ¼ 7.4 Hz, Ar 2-H), 7.30 (dd, 1H, Jo ¼ 7.7 Hz,
Jm ¼ 1.4 Hz, Ar 1-H), 7.39 (td, 1H, Jo ¼ 7.87 Hz, Jm ¼ 1.4 Hz, Ar 3-H),
8.30 (s, 1H, Ar 12-H), 8.78 (d, 1H, J ¼ 8.33, Ar-4-H), 12.34 (s, 1H, Ar-
NHCO). 13C-NMR (75 MHz, CDCl3) d: 56.6 (2 ꢀ C), 107.8, 113.4, 119.9,
120.6, 120.8, 123.1,132.8, 134.7, 138.7, 139.7, 144.5, 151.6, 164.2, 167.3.
Reduction of N-(2-formylphenyl)-2-nitrobenzamide (8). The
reduction of N-(2-formylphenyl)-2-nitrobenzamide 8 afforded a complex
mixture of products, where it was only possible to isolate diazocinone 12.

Dibenzo [b,f][1,5] Diazocinones
1499
Dibenzo [b,f] [1,5]-diazocine-6-(5H)-one (12). Compound (12)
(37.8 mg, 36%), obtained from nitrobenzamide (8) (128 mg, 0.47 mmol) and
powder iron (210 mg, 3.76 mmol), white powder, mp 265 8C (decomp).
(CH2Cl2/hexane 3 : 1). Anal. calcd. for C14H10N2O: C, 75.65; H, 4.54; N,
12.61. Found: C, 75.74; H, 4.37; N, 12.58%. IR nmax: 3258 (Ar-CONH-Ar),
1639 (Ar-CONH-Ar), 1615 (Ar-C55N-Ar). 1H-NMR (DMSO-d6) d: 6.56
(s,1H, Ar 12-H), 6.85 (t, 1H, J ¼ 7.4 Hz, Ar-2-H), 6.96 (d, 1H, J ¼ 6.8 Hz,
Ar 10-H or Ar-4-H), 6.97 (d, 1H, J ¼ 7.2 Hz, Ar 4-H, or Ar- 10-H), 7.21–
7.24 (m, 2H, Ar 3-H, and Ar-8-H), 7.38 (td, 1H, Jo ¼ 7.7 Hz, Jm ¼ 1.5 Hz,
Ar 9-H), 7.52 (s, 1H, Ar-NHCO), 7.71 (d, 2H, J ¼ 6.73 Hz, Ar- 1-H, and
Ar-7-H). 13C-NMR (75 MHz, DMSO-d6) d: 116.0, 116.6, 119.0, 127.3,
127.9, 128.7, 129.9, 130.1, 133.5,133.9, 139.8, 150.0, 163.2, 166.7.
ACKNOWLEDGMENT
This work was supported by a grant from CEPEDEQ-Facultad of the
Chemical and Pharmaceutical Sciences Faculty, University of Chile,
Santiago, Chile.
REFERENCES
¨
1. Jensen, J.; Tejler, J.; Warnmark, K. General protocols for the synthesis of C2-
symmetric and asymmetric 2,8-disubstituted analogues of Troger’s base via
¨
efficient bromine–lithium exchanges of 2,8-dibromo-6H,12H-5,11-methanodibenzo
[b,f] [1,5] diazocine. J. Org. Chem. 2002, 67, 6008–6014.
¨
¨
2. Jensen, J.; Warnmark, K. Synthesis of halogen substituted analogues of Troger’s
base. Synthesis 2001, 12, 1873–1877.
3. Hansson, A.; Jensen, J.; Wendt, O. F.; Warnmark, K. Synthesis of dihalo-
¨
substituted analogues of Troger’s base from ortho and meta-substituted anilines.
Eur. J. Org. Chem 2003, 16, 3179–3188.
¨
4. Demeunynck, M.; Tatibou¨et, A. Recent developments in Troger’s base chemistry.
In Progress in Heterocyclic Chemistry; Gribble, G. W., Gilchrist, T. L. eds.
Pergamon: Oxford, U.K., 1999; Vol. 11, pp. 1–20.
5. Tatibouet, A.; Demeunynck, M.; Andraud, C.; Collet, A.; Lhomme, J. Synthesis
¨
and study of an acridine substituted Troger’s base: Preferential binding of the
(2) isomer to B-DNA. Chem. Commun. 1999, 2, 161–162.
¨
6. Harmata, M.; Kahraman, M. Congeners of Troger’s base as chiral ligands. Tetra-
hedron: Asymmetry 2000, 11, 2875–2879.
7. Kamal, A.; Venkata Ramana, K.; Antaki, H. B.; Venkata Ramana, A. Mild and
efficient reduction of azides to amines: Synthesis of fused [2,1-b] quinazolines.
Tetrahedron Lett. 2002, 43, 6861–6863.
8. Miyahara, I.; Izumi, K.; Ibrahim, A. A.; Inazu, T. Novel C-2 chiral diamine ligands
¨
derived from cyclic Troger bases. Tetrahedron Lett. 1999, 40, 1705–1708.
9. Eguchi, S.; Matushita, Y.; Takeuchi, H. Novel synthetic route to benzopolyaza-
macrocycles. Synthesis of 16-membered tetrabenzotetraazamacrocycles via

1500
H. Pessoa-Mahana et al.
bisquinazolinone annelation and reductive ring enlargement. J. Org. Chem. 1992,
57, 6975–6979.
10. Hassner, A.; Sun, B.; Gellermann, G.; Meir, S. Dilactams. Synthesis of nonsymme-
trical dibenzodiazocinediones. Tetrahedron Lett. 2004, 45, 1377–1379.
11. Wakankar, D. M.; Hosangadi, B. D. Studies in large ring compounds: Part VI.
Synthesis of 5,11-disubstituted dibenzo [b,f] [1,5] diazocine-6,12 (5H,11H)-
diones. Indian J. Chem. 1984, 23, 136–139.
´
12. Valderrama, J. A.; Pessoa-Mahana, H.; Sarras, G.; Tapia, R. Access to quinazo-
lines from 2-nitrobenzaldehyde and arylamines. Heterocycles 1999, 51,
2193–2201.
13. Pessoa-Mahana, H.; Pessoa-Mahana, C. D.; Salazar, R.; Saez, E.;
Valderrama, J. A.; Araya-Maturana, R. Solvent free synthesis of 6-arylbenzimi-
dazo [1,2-c]quinazolines under microwave irradiation. Synthesis 2004, 3,
436–440.