Synthesis of pyrazolo[3,4-b]- and pyrido[2,3-b]-1,5-benzodiazepines

Article abstract of DOI:10.1080/00397911003629507

3-Dimethylaminomethyleno-4-phenyl-1H-1,5-benzodiazepin-2-one (1) was synthesized and reacted with hydrazines, active nitriles, and amino-heterocyclic compounds to give fused heterocyclic compounds 2-14.

Full text of DOI:10.1080/00397911003629507

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Synthesis of Pyrazolo[3,4-b]- and
Pyrido[2,3-b]-1,5-benzodiazepines
A. Khodairy a
a Sohag University, Faculty of Science, Chemistry Department,
Sohag, Egypt
Published online: 02 Feb 2011.
To cite this article: A. Khodairy (2011) Synthesis of Pyrazolo[3,4-b]- and Pyrido[2,3-b]-1,5-
benzodiazepines, Synthetic Communications: An International Journal for Rapid Communication of
Synthetic Organic Chemistry, 41:4, 612-621, DOI: 10.1080/00397911003629507
To link to this article: http://dx.doi.org/10.1080/00397911003629507
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Synthetic Communications1, 41: 612–621, 2011
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911003629507
SYNTHESIS OF PYRAZOLO[3,4-b]- AND
PYRIDO[2,3-b]-1,5-BENZODIAZEPINES
A. Khodairy
Sohag University, Faculty of Science, Chemistry Department, Sohag, Egypt
Abstract 3-Dimethylaminomethyleno-4-phenyl-1H-1,5-benzodiazepin-2-one (1) was
synthesized and reacted with hydrazines, active nitriles, and amino-heterocyclic compounds
to give fused heterocyclic compounds 2–14.
Keywords Pyrazolo(3,4-b)- and pyrido(2,3-b)-4-phenyl-1H-1,5-benzodiazepines
INTRODUCTION
The pharmacological activities[1–5] of pyrazolo- and pyridobenzodiazepines
prompted us to contine our previous work on the synthesis of fused and spiro-1,5
benzodiazepines.[1,6–9] Enaminones have been utilized extensively as building blocks
in organic synthesis of polyfunctionally substituted heterocycles.[10–15] We report here
the utility of 3-dimethylaminomethyleno-4-phenyl-1H-1,5-benzodiazepin-2-one (1)
for the syntheses of pyrazole, isoxazole, and pyridine derivatives, hoping to get
compounds with better biological activity for medicinal applications.
RESULTS AND DISCUSSION
3-Dimethylaminomethyleno-4-phenyl-1H-1,5-benzodiazepin-2(3H)-one (1) was
synthesized from the reaction of 1,3-dihydro-4-phenyl-1,5-benzodiazepin-2-one[1]
with dimethylformamidedimethylacetals (DMF-DMA) in refluxing p-xylene
[Eq. (1)]. 1H NMR spectrum showed new signals at d 8.00 as a singlet corresponding
=
to the CH group and at d 2.36 as a singlet corresponding to the N(CH3)2 group. Its
Received November 7, 2009.
Address correspondence to A. Khodairy, Sohag University, Faculty of Science, Chemistry
Department, Sohag 82524, Egypt. E-mail: khodairy@yahoo.com
612

SYNTHESIS OF FUSED BENZODIAZEPINES
613
mass spectrum showed m=z (relative abundance) of 291 [(Mþ), 41.2%], 392 [(M þ 1þ),
11.5%], and 393 [(M þ 2þ), 1.5%] (Scheme 1).
The reaction of enaminone 1 with phenylhydrazine in ethanol in the presence
of a catalytic amount of triethylamine afforded 3-(2-phenylhydrazinomethyleno)-
4-phenyl-1H-1,5-benzodiazepin-2-one (2), which underwent intramolecular cycliza-
tion in refluxing dimethylformamide (DMF) to give 1,4-diphenylpyrazolo[3,4-b]-
1,5-benzodiazepine (3). Treatment of enaminone 1 with hydrazine or hydroxylamine
afforded pyrazolo[3,4-b]- and isoxazolo[5,4-b]-1,5-benzodiazepines 4a,b, respectively
Scheme 1. Mass spectrum fragmentation of enaminone 1.

614
A. KHODAIRY
(Scheme 2). Infrared (IR) spectra of compounds 3 and 4a,b showed the disappearance
=
1
of the absorption band corresponding to the C O group. H NMR showed the
disappearance of the -N(CH3)2 signal.
Treatment of compound 1 with malononitrile in the presence of sodium ethox-
ide or cyanothioacetamide in acetic acid gave 3-cyano-5-phenyl-2,11-dihydro-1H-
pyrido[2,3-b]-1,5-benzodiazepin-2-one (5) or 3-cyano-5-phenyl-2,11-dihydro-1H-
pyrido[2,3-b]-1,5-benzodiazepin-2-thione (6), respectively (Scheme 3). Their IR spec-
tra showed the new absorption bands corresponding to NH (3310, 3300), CN (2194,
=
=
2224), C O (1688), and C S (1124), respectively. Mass spectrum of compound 5
showed m=z (relative abundance) Mþ, 312 (79%). Treatment of compound 1 with
2-amino-1,1,3-tricyanopropene in the presence of a catalytic amount of triethylamine
gave 10-amino-8-oxo-12-phenyl-8,9-dihydro-5H-[1,6]naphthyridino[2,3-b]-1,5-benzo-
diazepine-7-carbonitrile (7) (Scheme 3). Its IR spectrum showed new absorption bands
=
corresponding to NH (3395), NH2 (3257, 3200), CN (2184), and C O (1670), respect-
ively. ꢀ1H NMR spectrum showed deuterium exchangeable proton at d ¼ 10.10, 7.7,
and 5.00–4.64, which are attributed to 2 NH and NH2 groups. Its MS spectrum
showed the fragment ion at m=z 376 due to (Mþ ꢀ 1). In analogy, enaminone 1 was
reacted with 1,3-diethyl-2-amino-1-cyano-1-propendioate in the presence of triethyla-
mine as a catalyst to give ethyl 8,10-dioxo-12-phenyl-7,8,9,10-tetrahydro-5H-[1,6]
naphthyridino[2,3-b]-1,5-benzodiazepine-7-carboxylate (8) (Scheme 3). Its IR spec-
trum showed new absorption bands corresponding to OH (3421), 2NH (3309,
1
=
=
3244), C Oester (1722), and C Oamide (1688), respectively. Its H NMR spectrum
showed deuterium exchangeable protons at d ¼ 10.05, 6.00, and 2.10, which are attrib-
uted to 2 NH and OH groups. Also, enaminone 1 was reacted with 3-ethyl-2-amino-
1,1-dicyanopropenoate in the presence of triethylamine as a catalyst to afford
pyrido[2,3-b]-1,5-benzodiazepine derivative 9 (Scheme 3). IR spectrum showed new
absorption bands corresponding to 2NH (3451, 3244), CN (2222), and COester
1
(1714), respectively. H NMR spectrum showed the following signals corresponding
=
to NHbenzodiazepine at d 12.00 ppm, CH at d 8.20 ppm, NHpyridine at d 6.20 ppm,
aromatic protons at d 7.00–7.85 ppm, CH2 at d 4.10–3.80 ppm, and CH3 group at d
1.20–0.90 ppm, respectively, along with a deuterium exchangeable proton at
d ¼ 12.00 ppm and 6.20 ppm, which are attributed to 2 NH groups. The formation
Scheme 2. Reaction of enaminone 1 with hydrazines.

SYNTHESIS OF FUSED BENZODIAZEPINES
615
Scheme 3. Reaction of enaminone 1 with active nitriles.
reaction of compounds 7 and 8 was assumed to proceed via nucleophilic attack of the
active methylene to the olefinic bond of compound 1 with elimination of dimethyla-
=
mine, followed by condensation of the amino group with the C O group, hydrolysa-
tion of one of the cyano groups into CONH2, and subsequent addition to the cyano
group or the ester group with elimination of the ethanol molecule.
The reaction of compound 1 with 3-amino-1,2,4-triazole, 3-aminotriazene, 2-ami-
nothiazole, 3-aminopyridine, o-aminothiophenol, or o-phenelenediamine in refluxing
pyridine afforded 3-[(1H-1,2,4-triazol-5-yl)aminomethylene]- 10, 3-[(triazine-3-yl)ami-
nomethylene]- 11, 3-[(1,3-thiazol-2-yl)aminomethylene]- 12, 3-[(pyridine-3-yl)
aminomethylene]- 13, 3-[(2-mercaptophenyl)aminomethylene]- 14a, 3-[(2-aminophenyl)
aminomethylene]- 14b, and 5-phenyl-1,3-dihydro-2H-1,5-benzodiazepin-2-ones,
respectively (Scheme 4). MS spectrum of compound 10 showed the fragment ion at
m=z at 331 (4.5%) due to (Mþ þ 1). An attempt was made to cyclize compounds

616
A. KHODAIRY
Scheme 4. Reaction of enaminone 1 with amino-heterocyclic compounds.
10–14a,b in boiling glacial acetic acid[16] but it was unsuccessful. So, we studied these
reactions through the minimized energy structure of compounds 10–14a,b by MM2
and AM1, and we noticed that the NH or SH group is out of plan with the carbonyl
group of benzodiazepinone (Fig. 1).
EXPERIMENTAL
All melting points are uncorrected and were recorded on a Melt-Temp II
melting-point apparatus. Infrared (IR) spectra were measured as KBr pellets on a
Nicolet 710 Fourier transform (FT)–IR spectrometer. 1H NMR spectra were
recorded in deuterated chloroform or dimethylsulfoxide (DMS) at 200 MHz on a
Varian Gemini NMR spectrometer using tetramethylsilane (TMS) as an internal
reference. The D2O experiment was carried out to check acidic protons. Mass

SYNTHESIS OF FUSED BENZODIAZEPINES
617
Figure 1. Minimized energy structure of 14 by MM2 and AM1. Software used to minimize energy
structures is Chemoffice Ultra 2008, v. 11 (Chem3D Pro 11.0).
spectrometry was performed on a Shimadzu GCMS-QP 1000 mass spectrometer at
70 eV. The elemental analyses were carried on a Perkin-Elimer 2400 analyzer.
3-Dimethylaminomethylene-4-phenyl-1H-1,5-benzodiazepin-2-one (1)
Dimethylformamide dimethylacetal (10 mmol) was added to 4-phenyl-2(H)-
1,5-benzodiazepin-2-one[1] (10 mmol), in p-xylene (20 ml), and the reaction mixture
was refluxed for 3 h, then left to cool. The solid product so formed was filtered, dried,
and crystallized from p-xylene. Yield 60%; mp 217–219 ꢁC. Found: C, 74.20; H, 5.88;
N, 14.42. C18H17N3O (291.34) requires: C, 74.77; H, 5.45; N, 14.76. IR (KBr):
ꢀ1
1
n ¼ 3245 (NH) cmꢀ1, 1704 (C O) cm , 1605 (C N) cmꢀ1; H NMR (DMSO):
=
=
=
10.2 (s, 1H, NH), 8.00 (s, 1H, CH), 7.97–6.90 (m, 9H, arom.), 2.63 [s, 6H,
N(CH3)2] ppm; MS (m=e): 65 (5.6%), 51 (3.5%), 77 (8.6%), 90 (6%), 92 (2.1%), 98
(63.4%), 117 (2%), 118 (1.9%), 193 (23%), 194 (100%), 195 (41.9%), 219 (5.8%), 247
(2.5%), 291 [(Mþ), 41.2%], 392 [(M þ 1þ), 11.5%], 393 [(M þ 2þ), 1.5%].
3-(2-Phenylhydrazinomethylene)-4-phenyl-1H-
1,5-benzodiazepin-2-one (2)
Phenylhydrazine (10 mmol) and a few drops of triethylamine were added to a
suspension of compound 1 (10 mmol) in ethanol (30 ml). The reaction mixture was
refluxed for 3 h, then left to cool. The solid product so formed was filtered, dried,
and crystallized from dioxane. Yield 66%; mp 237–239 ꢁC. Found: C, 74.20; H,
5.44; N, 15.62. C22H18N4O requires: C, 74.56;ꢀH1 , 5.12; N, 15.81. IR (KBr):
1
n ¼ 3390, 3300, 3225 (NH) cmꢀ1, 1690 (C O) cm , 1605 (C N) cmꢀ1; H NMR
=
=
=
(CDCl3): d ¼ 10.5 (s, 1H, NH), 8.00 (s, 1H, CH), 7.97–6.90 (m, 15H, arom.
þNH), 6.4 (br, 1H, NH) ppm.

618
A. KHODAIRY
1,4-Diphenylpyrazolo[3,4-b]-1,5-benzodiazepine (3)
A suspension of compound 2 (5 mmol) in DMF (10 ml) was refluxed for 3 h. The
reaction was left to cool and poured into crused ice with HCl (5 ml). The separated
solid was filtered, dried, and crystallized from ethanol. Yield 45%; mp 205–207 ꢁC.
Found: C, 78.19; H, 4.54; N, 16.92. C22H16N4 requires: C, 78.55; H, 4.79; N, 16.66.
1
IR (KBr): n ¼ 3275 (NH) cmꢀ1, 1605 (C N) cmꢀ1; H NMR (DMSO): 10.6 (s, 1H,
=
=
NH), 8.40 (s, 1H, CH), 7.97–6.90 (m, 14H, arom.) ppm.
4-Phenylpyrazolo[3,4-b]-1,5-benzodiazepine (4a)
Hydrazine hydrazine (10 mmol) was added to a suspension of compound 1
(10 mmol) in ethanol (30 ml). The reaction mixture was refluxed for 3 h, then left to
cool. The solid product so formed was filtered, dried, and crystallized from benzene.
Yield 56%; mp 177 ꢁC. Found: C, 73.60; H, 4.74; N, 21.72. C16H12N4 (260.29)
requires: C, 73.83; H, 4.65; N, 21.52. IR (nmaxncmꢀ1): 3380, 3265 (2NH), 1640
1
(C N); H NMR (CDCl3): 10.5 (s, 1H, NH), 8.30 (s, 1H, CH), 7.80–6.50 (m,
=
=
10H, arom. þNH) ppm.
5-Phenylisoxazolo[5,4-b](1,5)benzodiazepines (4b)
A mixture of compound 1 (10 mmol) and hydroxylamine hydrochloride
(10 mmol) in dry pyridine (20 ml) was refluxed for 4 h. The reaction mixture was left
to cool and poured into a mixture of cold water (50 ml) and HCl (5 ml). The solid pro-
duct was collected by filtration, dried, and crystallized from chloroforme. Yield 76%;
mp 226–228 ꢁC; Found: C, 73.70; H, 4.64; N, 16.32. C16H11N3O (261.27) requires: C,
73.55; H, 4.24; N, 61.08. IR (KBr): n ¼ 3244 (NH) cmꢀ1, 1615 (C N) cmꢀ1; 1H NMR
=
=
(CDCl3): 10.7 (s, 1H, NH), 8.20 (s, 1H, CH), 7.97–6.90 (m, 9H, arom.) ppm.
3-Cyano-5-phenyl-2,11-dihydro-1H-pyrido[2,3-b]-1,5-benzodiazepin-
2-one (5)
Malononitrile (10 mmol) was added to a suspension of compound 1 (10 mmol)
in ethanolic sodium ethoxide (Na, 10 mmol in 20 ml ethanol). The mixture was
refluxed for 1 h, left to cool, and poured into a mixture of cold water (20 ml) and
HCl (2 ml). The precipitate was collected by filtration, dried, and crystallized in etha-
nol. Yield 96%; mp 240–242 ꢁC. Found: C, 72.61; H, 4.34; N, 17.62. C19H13N4O
(313.33) requires: C, 72.83; H, 4.18; N, 17.88. IR (KBr): n ¼ 3412 (OH) cmꢀ1
,
1
3300, 3225 (NH) cmꢀ1, 2194 (CN) cmꢀ1, 1654 (C O) cmꢀ1; H NMR (DMSO):
=
=
10.3 (s, 1H, NH), 8.50 (s, 1H, CH), 7.70–6.50 (m, 9H, arom.), 5.5 (s, 1H, NH);
MS (m=e): 312 (79%), 270 (71.8), 195 (28.7), 134 (98.6), 51 (100) ppm.
3-Cyano-5-phenyl-2,11-dihydro-1H-pyrido[2,3-b]-1,5-
benzodiazepine-2-thione (6)
Cyanothioacetamide (10 mmol) was added to a suspension of compound 1
(10 mmol) in glacial acetic acid (30 ml). The reaction mixture was refluxed for 3 h, left

SYNTHESIS OF FUSED BENZODIAZEPINES
619
to cool, and poured into cold water (20 ml). The solid product was filtered, dried, and
crystallized from dioxane. Yield 80%; mp 186–188 ꢁC. Found: C, 69.60; H, 3.44; N,
17.22; S, 9.90. C19H12N4S (328.39) requires: C, 69.49; H, 3.68; N, 17.09; S, 9.79. IR
1
(KBr): n ¼ 3310, 3233 (NH) cmꢀ1, 2221 (CN) cmꢀ1, 1144 (C S) cmꢀ1; H NMR
=
=
(DMSO): 10.8 (s, 1H, NH), 8.10 (s, 1H, CH), 7.70–6.50 (m, 9H, arom.), 6.00
(s, 1H, NH).
Synthesis of Compounds 7–9
2-Amino-1,1,3-tricyano-1-propene (10 mmol), 1,3-diethyl-2-amino-1-cyano-1-
propenate (10 mmol), or 3-ethyl-2-amino-1,1-dicyanopropenate (10 mmol), and a
few drops of triethylamine were added to a suspension of compound 1 (10 mmol)
in ethanol (30 ml). The mixture was refluxed for 4 h, and the precipitated solid so
formed was collected by filteration (product 8). The mixture was left to cool, and
the formed solid was obtained by filtration (products 9 and 10) and crystallized.
10-Amino-8-oxo-12-phenyl-8,9-dihydro-5H-[1,6]naphthyridino[2,3-b]-
1,5-benzodiazepine-7-carbonitrile (7). From ethanol. Yield 80%; mp 260–
262 ꢁC; MS: m=z ¼ 376 (18.5, M), 356 (51.9), 152 (25.9), 153 (18.5), 106 (74.1), 79
(100), 51 (74.1). Found: C, 69.60; H, 3.94; N, 22.45. C22H14N6O (378.38) requires:
C, 69.83; H, 3.73; N, 22.21. IR(KBr): n ¼ 3440, 3395, 3257, 3200 (NH, NH2) cmꢀ1
,
1
2184 (CN) cmꢀ1, and 1670 (C O) cmꢀ1; H NMR (DMSO): 10.10 (s, 1H, NH),
=
=
8.20 (s, 1H, CH), 7.70–6.50 (m, 10H, arom. þNHpyridine), 4.3–4.1 (br, 2H, NH2) ppm.
8,10-Dioxo-12-phenyl-7,8,9,10-tetrahydro-5H-[1,6]naphthyridino[2,3-b]-
1,5-benzodiazepine-7-carboxylate (8). From dioxane. Yield 55%; mp
187–189 ꢁC. Found: C, 67.90; H, 4.55; N, 13.31. C24H18N4O4 (426.42) requires C,
=
67.60; H, 4.25; N, 13.14. IR(KBr): n ¼ 3309, 3244 (OH, NH), 1717 (C Oester), and
1688 (C O) cmꢀ1. H NMR (DMSO): 10.60 (s, 1H, NH), 8.40 (s, 1H, CH),
7.70–6.50 (m, 9H, arom.), 6.00 (s, 1H, NH), 4.10–3.80 (q, CH2), 2.4–2.1 (br, 1H,
OH), 1.20–0.90 (t, 3H, CH3) ppm.
1
=
=
5-Phenylpyrido[2,3-b]-1,5-benzodiazepine (9). From ethanol. Yield (60%);
mp 166–168 ꢁC. Found: C, 70.45; H, 4.50; N, 17.31. C24H17N5O2 (407.42) requires C,
70.76; H, 4.21; N, 17.19. IR (KBr): n ¼ 3244, 3200 (2NH), 2222 (CN), and 1714
(C Oester) cmꢀ1 1H NMR (DMSO): 10.00 (s, 1H, NH), 8.30 (s, 1H, CH),
;
=
=
7.80–6.90 (m, 9H, arom.), 6.30–6.50 (br, 1H, NH), 4.3–4.00 (q, 2H, CH2),
1.40–1.00 (t, 3H, CH3) ppm.
Synthesis of Compounds 10–14
A solution of compound 1 (10 mmol) and 3-amino-1,2,4-triazole, 3-aminotria-
zene, 3-aminopyridine, 2-aminothiazole, o-aminothiophenol, and o-phenelenediamine
(10 mmol) in pyridine (15 ml) was refluxed for 6 h. The reaction mixture was concen-
trated, cooled, and poured into a mixture of cold water (50 ml) and HCl (5 ml). The
solid product that was obtained on cooling was filtered and crystallized.
3-[(1,2,4-Triazol-5-yl)aminomethylene]-4-phenyl-1,3-dihydro-1H-benzo-
diazepin-2-one (10). From ethanol. Yield (92%); mp 280–282 ꢁC. Found: C, 65.68;

620
A. KHODAIRY
H, 4.60; N, 25.66. C18H14N6O (330.34) requires C, 65.44; H, 4.27; N, 25.44. IR
(nmaxncmꢀ1): 3332, 3225 (NH), 1704 (C O) cmꢀ1; H NMR (DMSO): 10.3 (s, 1H,
1
=
=
NH), 9.0 (s, 1H, CHtriazole), 8.50 (br, 1H, CH), 7.70–6.50 (m, 9H, arom.), 6.5–6.3
=
(br, 1H, NH) ppm.
3-[(Triazine-3-yl)aminomethylene]-5-phenyl-1,3-dihydro-2H-1,5-benzo-
diazepin-2-one (11). From dioxane. Yield 80%; mp 233–235 ꢁC. Found: C, 66.85;
H, 4.40; N, 24.31. C19H14N6O (342.35) requires: C, 66.66; H, 4.12; N, 24.55. IR
1
(nmaxncmꢀ1): 3300, 3225 (NH), 1706 (C O) cmꢀ1; H NMR (DMSO): 10.1 (s, 1H,
=
=
NH), 8.50 (s, 1H, CH), 7.70–6.50 (m, 10H, arom. þNH), 6.6–6.3 (br, 2H,
=
CH CHtriazene) ppm.
3-[(Pyridine-3-yl)aminomethylene]-4-phenyl-1,3-dihydro-2H-1,5-benzo-
diazepin-2-one (12). From ethanol. Yield 94%; mp 300–302 ꢁC. Found: C, 65.50; H,
4.22; N, 16.39; S, 9.39. C19H14N4OS (346.40) requires: C, 65.88; H, 4.07; N, 16.17; S,
1
9.26. IR (nmaxncmꢀ1): 3289, 3221 (NH), 1700 (C O) cmꢀ1. H NMR (DMSO): 11.0
=
=
(s, 1H, NH), 8.10 (s, 1H, CH), 7.70–6.50 (m, 10H, arom. þ ¼ CHthiazole), 6.5 (s, 1H,
NH)ppm.
3-[(Pyridine-3-yl)aminomethylene]-4-phenyl-1,3-dihydro-2H-1,5-benzo-
diazepin-2-one (13). From acetic acid. Yield (70%); mp 200 ꢁC. Found: C, 74.40;
H, 4.520; N, 16.66. C21H16N4O (340.37) requires: C, 74.10; H, 4.74; N, 16.46. IR
ꢀ1
(nmaxncmꢀ1): 3280, 3229 (NH), 1701 (C O) cm
;
1H NMR (DMSO): 11.0 (s,
1H, NH), 9.1 (s, 1H, CH pyridine), 8.7–8.6 (d, 2H, CH pyridine), 8.30 (s, 1H,
=
=
CH), 7.90–6.50 (m, 10H, arom. þ ¼ CHthiazole), 6.5 (s, 1H, NH) ppm.
3-[(2-Mercaptophenyl)aminomethylene]-4-phenyl-1,3-dihydro-2H-1,5-
benzo-diazepin-2-one (14a). From benzene. Yield 45%; mp 160–162 ꢁC. Found: C,
71.35; H, 4.80; N, 11.51; S, 8.90. C22H17N3OS (371.45) requires: C, 71.14; H, 4.61; N,
ꢀ1,
11.31; S, 8.63. IR (nmaxncmꢀ1): 3380, 3219 (NH), 1703 (C O) cm
1H NMR
=
=
(DMSO): 10.50 (s, 1H, NH), 8.20 (s, 1H, CH), 7.80–6.50 (m, 10H, arom. þNH),
2.5 (s, 1H, SH) ppm.
3-[(2-Aminophenyl)aminomethylene]-4-phenyl-1,3-dihydro-2H-1,5-benzo-
diazepin-2-one (14b). From dioxane. Yield 70%; mp 255–257 ꢁC. Found: C, 74.25;
H, 5.33; N, 15.66. C22H18N4O (354.40) requires: C, 74.56; H, 5.12;ꢀN1,, 15.81. IR
=
(nmaxncmꢀ1): 3322, 3290, 3230, 3143 (NH2, NH), 1700 (C O) cm
1H NMR
=
(DMSO): 11.0 (s, 1H, NH), 8.00 (s, 1H, CH), 7.90–6.50 (m, 10H, arom. þNH),
5.5–5.3 (br, 2H, NH2) ppm.
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