A facile synthesis of 3-methylene-4-aryl-1,3,4,5-tetrahydrobenzo[b][1,4] diazepin-2-ones and 3-arylmethylene-4,5-dihydro-3H-benzo[b] [1,4]diazepin-2- ylamines

Article abstract of DOI:10.1055/s-2006-950352

A simple and convenient synthesis of 3-methylene-4-aryl-1,3,4,5- tetrahydrobenzo[b][1,4]diazepin-2-ones was accomplished by the S_N2 nucleophilic substitution of the acetates of Baylis-Hillman adducts of acrylate with 1,2-phenylenediamines, foll

Full text of DOI:10.1055/s-2006-950352

PAPER
4205
A Facile Synthesis of 3-Methylene-4-aryl-1,3,4,5-tetrahydrobenzo[b][1,4]di-
azepin-2-ones and 3-Arylmethylene-4,5-dihydro-3H-benzo[b][1,4]diazepin-2-
ylamines1
S
ynthesis of Subs
.
titute
d
D
ia
z
P
ipins athak, S. Nag, S. Batra*
Medicinal Chemistry Division, Central Drug Research Institute, PO Box 173, Lucknow 226 001, India
Fax +91(522)2623405; fax +91(522)2623938; E-mail: batra_san@yahoo.co.uk
Received 28 July 2006
SN2 reaction of 1,2-phenylenediamine with the acetyl de-
Abstract: A simple and convenient synthesis of 3-methylene-4-
aryl-1,3,4,5-tetrahydrobenzo[b][1,4]diazepin-2-ones was accom-
plished by the SN2 nucleophilic substitution of the acetates of
Baylis–Hillman adducts of acrylate with 1,2-phenylenediamines,
rivative of the Baylis–Hillman adduct should result in a
diamino ester derivative, capable of intramolecular cy-
clization, to yield the methylene benzo[b][1,4]diazepin-2-
followed by base-mediated intramolecular cyclization. Similar sub- one. Previously, Chuang and Sharpless described the nu-
strates derived from the Baylis–Hillman adducts of acrylonitrile via
Pinner’s reaction led to 3-arylmethylene-4,5-dihydro-3H-ben-
zo[b][1,4]diazepin-2-ylamines in good yields.
cleophilic ring opening of the aziridinium ion with 1,2-
phenylenediamine, followed by base-mediated ring clo-
sure, to afford the benzo[b][1,4]diazepin-2-one.5a Further-
Key words: Baylis–Hillman, 1,2-phenylenediamine, diazipine, di-
more, Kim et al. carried out an SN2¢ reaction of 1,2-
azepin-2-ones, diazepin-2-ylamines
phenylenediamine with the acetyl derivatives of the
Baylis–Hillman adducts to afford the diamino esters,
which were cyclized in the presence of acetic acid to yield
A large number of pharmaceutical and biologically active
agents incorporate heterocycles as a substructural unit.
This has maintained researchers motivation for develop-
ing new synthetic strategies with which to achieve the
synthesis of heterocyclic architectures, in simple and con-
venient fashions. In recent times, the derivatives afforded
via the Baylis–Hillman reaction have proved to be fasci-
nating precursors for the straightforward construction of
biologically relevant heterocyclic systems.2 This is attrib-
uted to the propensity of this robust C–C bond forming re-
action to deliver products consisting of highly reactive
functional groups. We have been interested in the synthe-
sis of heterocycles containing an exocyclic methylene
group, utilizing derivatives of the Baylis–Hillman adduct.
In this context, recently we have described the synthesis
of a-methylene-d-valerolactones, 3-methylenepiperidin-
2,6-diones and 3-methylene-2-pyrrolidinones in excellent
yields.3 In our continued efforts in this direction, we have
now achieved a facile and diversity-oriented synthesis
of 3-methylene-4-aryl-1,3,4,5-tetrahydrobenzo[b][1,4]di-
azepin-2-ones and 3-arylmethylene-4,5-dihydro-3H-ben-
zo[b][1,4]diazepin-2-ylamines.
arylmethylene-benzo[b][1,4]diazepin-2-ones in low
yields, along with other side products.5b Intrigued by these
reports, we initiated studies on the synthesis of a range of
benzo[b][1,4]diazepin-2-ones, possessing an exocyclic
methylene moiety, from the Baylis–Hillman adducts. The
results of these investigations are described in this com-
munication.
The starting substrates for the study, the acetyl derivatives
1a–h of the Baylis–Hillman adduct, were synthesized fol-
lowing the literature procedure.6 The SN2 nucleophilic
substitution reaction of 1,2-phenylenediamine with the
acetates 1a–h was easily accomplished in the presence of
1,4-diazabicyclo[2.2.2]octane (DABCO) in a tetrahydro-
furan (THF)–water system, leading to the formation of di-
amino esters 2a–h in excellent yields (Scheme 1).
Treatment of these diamino esters with sodium hydride in
toluene at 80 °C furnished the desired diazepinones 3a–h
in good to excellent yields. In order to make the strategy
diversity-oriented, it was envisaged that the substituted 2-
nitroanilines could be introduced, instead of the 1,2-phe-
nylenediamine, during the SN2 nucleophilic substitution.
Subsequently the nitro group could be reduced chemose-
lectively to furnish the amine, which could then be cy-
clized in the usual fashion. Accordingly, the 2-nitroaniline
was treated with the acetyl derivative of the Baylis–
Hillman adduct, in the presence of DABCO, in a THF–
water system. Unfortunately, this reaction failed to occur
even after prolonged reaction time. We reasoned that,
probably, the nucleophilicity of the aniline is reduced due
to the deactivating effect of the nitro group present in the
molecule, leading to the failure of reaction. Thus, in an al-
ternative strategy for the synthesis of the desired sub-
strates, the 2-nitroaniline anion was generated by the
treatment of 2-nitroaniline with sodium hydride in anhy-
The benzo[b][1,4]diazepin-2-ones constitute unique
structures that exhibit a spectrum of biological activities
such as interleukin 1b enzyme inhibition and potassium
current blockers, amongst others.4 A survey of the litera-
ture revealed several methods,5 both in solution and in the
solid phase, whereby 1,2-phenylenediamine or its precur-
sor, the 2-nitroaniline, have been successfully employed
for the synthesis of this structural motif. In principle, the
SYNTHESIS 2006, No. 24, pp 4205–4211
x
x.
x
x
.
2
0
0
6
Advanced online publication: 02.11.2006
DOI: 10.1055/s-2006-950352; Art ID: P09106SS
© Georg Thieme Verlag Stuttgart · New York

4206
R. Pathak et al.
PAPER
HN
NH2
OAc
HN
NH
a
b
Compd R
CO2Et
CO2Et
R
R
R
O
a
b
c
d
e
f
C6H5
2-Cl-C6H4
2-F-C6H4
2,4-(Cl)2-C6H3
4-Me-C6H4
4-Cl-C6H4
4-Br-C6H4
2-thienyl
62–86%
59–84%
1a–h
3a–h
2a–h
R'
71–76%
c
R'
R'
R'
R'
R'
g
h
HN
NO2
HN
NH2
b
HN
NH
e
CO2Et
CO2Et
Compd
4,9,12
5,7,8,10,13 Me
6,11,14 Cl
R'
H
R
R
83%
60–63%
R
O
4–6a
2,7a
3,8a
68–72%
R
d
O
CO2Et
NH
R'
R'
R
b
R'
70–76%
N
N
H
H
NH2
R'
12–14a
9–11a
Scheme 1 Reagents and conditions: (a) DABCO, 1,2-phenylenediamine or substituted 1,2-phenylenediamine, THF–H2O (1:1), r.t., 4–5 h; (b)
NaH, THF, 80 °C, 2 h; (c) i. Acetate, DABCO, THF, 15 min, ii. (Substituted) 2-nitroaniline, NaH, THF, 15 min, iii. Add i to ii, r.t., 1.5 h; (d)
SnCl2·2H2O, MeOH, reflux, 12 h; (e) Zn, HCO2NH4, MeOH, r.t., 3 h.
drous THF. This was combined with the acetate 1a, which amines in excellent yield. This amine was then subjected
had been treated with 4.5 equivalents of DABCO in anhy- to a similar synthetic protocol as described above, to fur-
drous THF for 10 minutes (optimized conditions). Grati- nish the diaminoester 7a in 74% yield. Since the differ-
fyingly, this reaction was complete in 1.5 hours, and ence between the yields was not significant, it was
furnished the desired product 4a. Similarly, the reaction of concluded that either strategy could be adopted for the
acetate 1a with 4,5-dimethyl- and 4,5-dichloro-2-nitro- generation of this class of compounds.
anilines afforded the compounds 5a and 6a, respectively.
Once the objective of obtaining the benzodiazepine-2-
Reduction of the nitro group of compounds 4–6a was at- ones from the acetyl derivatives of the Baylis–Hillman ad-
tempted with SnCl2·2H2O. Surprisingly, though the nitro duct of acrylate was accomplished, we turned our atten-
group was reduced to furnish the amino group, a simulta- tion to similar derivatives of acrylonitrile. It was
neous rearrangement occurred that resulted in the forma- envisaged that the acetyl derivative 15, upon treatment
tion of products 9–11a as the E-isomer only. It was with 1,2-phenylenediamine, would lead to the formation
presumed that the acidic medium of the reaction mixture of the diaminonitrile derivative 16. The free amino group
may have initiated this unusual rearrangement. In order to on the phenyl ring may then attack the cyano moiety, re-
validate this assumption, compound 2a was treated with sulting in an intramolecular cyclization to afford the prod-
either hydrochloric or phosphoric acid and found that, in uct 17. To this end, compounds 16a, 16b and 16e were
both cases, the rearrangement occurred to yield diamino- synthesized via SN2 reactions of 1,2-phenylenediamine on
ester 9a. Additional chemical evidence for the rearrange- the acetyl derivatives 15a, 15b and 15e (Scheme 2). Un-
ment was obtained by treating the compounds 9–11a with fortunately, the desired cyclization failed in our hands un-
sodium hydride to furnish the 3-arylmethylene-1,3,4,5- der a range of reaction conditions. Therefore, in order to
tetrahydrobenzo[b][1,4]diazepin-2-ones (12–14a) in achieve the desired cyclization, we decided to examine
good yields. In view of these results, we decided to exam- the transformation of the cyano group into the correspond-
ine the zinc-mediated reduction of the nitro group in the ing imidate. In principle, the nucleophilic attack of the
presence of ammonium formate.7 We were pleased to ob- amino group on this imidate in situ, should result in the
serve that, under these conditions, 4a and 5a afforded the desired benzodiazepinamine 17. However, though reac-
desired products 2a and 7a, respectively, in good yields. tion of substrates 16a, 16b and 16e with dry HCl in etha-
These diamino esters were treated with sodium hydride to nol led to the isolation of solid products in good yields, the
afford products 3a and 8a. In an attempt to improve the spectral analysis of these compounds indicated that the re-
yields, we also evaluated an alternate strategy whereby arranged products 18a, 18b and 18e, were in fact formed
the substituted 2-nitroaniline was first reduced to the cor- rather than the expected compounds 17. As discussed
responding substituted 1,2-phenylenediamine and then above, here too, the acidic medium of the reaction seems
subjected to the SN2 reaction. Hence, the 4,5-dimethyl-2- to have resulted in the rearrangement of the aniline moi-
nitroaniline was hydrogenated in the presence of palladi- ety, leading to the formation of products 18a, 18b and
um–carbon to furnish the 4,5-dimethyl-1,2-phenylenedi- 18e.
Synthesis 2006, No. 24, 4205–4211 © Thieme Stuttgart · New York

PAPER
Synthesis of Substituted Diazepinones
4207
IR (neat): 1705 (CO2Et), 3431 (NH and NH2) cm–1.
1H NMR (CDCl3, 300 MHz): d = 1.27 (t, J = 8.2 Hz, 3 H, CH2CH3),
2.94 (br s, 2 H, NH2), 4.23 (q, J = 7.3 Hz, 2 H, CH2CH3), 5.76 (s,
1 H, H2C=), 5.91 (s, 1 H, CHNH), 6.43 (s, 1 H, H2C=), 6.50–6.53
(m, 1 H, ArH), 6.67–6.80 (m, 3 H, ArH), 7.22–7.25 (m, 2 H, ArH),
7.35–7.49 (m, 2 H, ArH).
OAc
HN
NH2
CN
a
CN
R
R
52–56%
15a–b,e
16a–b,e
MS (ES+): m/z = 331.0 [M + H]+.
b
70–76%
Anal. Calcd for C18H19ClN2O2: C, 65.35; H, 5.79; N, 8.47. Found:
C, 65.22; H, 5.58; N, 8.43.
H2N
HN
R
N
.HCl
N
2-[(2-Aminophenylamino)(2-fluorophenyl)methyl]acrylic Acid
Ethyl Ester (2c)
R
NH2
N
Yield: 86%; brown oil.
17a–b,e
H
IR (neat): 1713 (CO2Et), 3399 (NH and NH2) cm–1.
18a–b,e
1H NMR (CDCl3, 300 MHz): d = 1.27 (t, J = 7.2 Hz, 3 H, CH2CH3),
3.39 (br s, 2 H, NH2), 4.12 (q, J = 7.2 Hz, 2 H, CH2CH3), 5.75 (s,
1 H, CHNH), 5.84 (s, 1 H, H2C=), 6.40 (s, 1 H, H2C=), 6.54 (d,
J = 7.3 Hz, 1 H, ArH), 6.44–6.74 (m, 3 H, ArH), 7.01–7.13 (m, 2 H,
ArH), 7.22–7.39 (m, 2 H, ArH).
Scheme 2 Reagents and conditions: (a) 1,2-Phenylenediamine,
DABCO, THF–H2O, r.t., 4–5 h; (b) EtOH–CH2Cl2, dry HCl gas, 0 °C,
8 h.
In summary, we have developed a straightforward, conve-
nient and practical synthesis of 3-methylene-4-aryl-
1,3,4,5-tetrahydro-benzo[b][1,4]diazepin-2-ones with at
least two point diversity, utilizing the derivatives of the
Baylis–Hillman adducts of acrylates. Similar derivatives,
resulting from Baylis–Hillman reaction of acrylonitrile,
MS (ES+): m/z = 315.1 [M + H]+.
Anal. Calcd for C18H19FN2O2: C, 68.77; H, 6.09; N, 8.91. Found: C,
68.51; H, 5.81; N, 8.77.
2-[(2-Aminophenylamino)(2,4-dichlorophenyl)methyl]acrylic
Acid Ethyl Ester (2d)
furnished the 3-arylemethylene-4,5-dihydro-3H-ben- Yield: 62%; brown oil.
IR (neat): 1714 (CO2Et), 3365 (NH, NH2) cm–1.
zo[b][1,4]diazepin-2-ylamines via tandem conversion of
the cyano group into imidates, acid-catalyzed rearrange-
ment, followed by intramolecular cyclization.
1H NMR (CDCl3, 200 MHz): d = 1.25 (t, J = 7.6 Hz, 3 H, CH2CH3),
4.16 (q, J = 7.3 Hz, 2 H, CH2CH3), 5.73 (s, 1 H, H2C=), 5.81 (s, 1 H,
CHNH), 6.26–6.46 (m, 2 H, H2C= and ArH), 6.72–6.73 (m, 3 H,
ArH), 7.18–7.43 (m, 3 H, ArH).
Melting points are uncorrected and were determined in capillary
tubes on a hot stage apparatus containing silicon oil. IR spectra were
MS (ES+): m/z = 365.0 [M + H]+.
1
recorded using a Perkin Elmer RX I FTIR spectrophotometer. H
Anal. Calcd for C18H18Cl2N2O2: C, 59.19; H, 4.97; N, 7.67. Found:
C, 58.91; H, 5.16; N, 7.49.
NMR and 13C NMR spectra were recorded on either a 300 or a 200
MHz FT spectrometer, using TMS as an internal standard (chemical
shifts in d values, J in Hz). The FAB-MS were recorded on JEOL/
SX-102 spectrometers and ES-MS were recorded through a Micro-
mass LCMS system. Elemental analyses were performed on a Carlo
Erba 1108 microanalyzer or an Elementar Vario EL III microana-
lyzer. The spectral data for 9a and 12a have been published previ-
ously.5b
2-[(2-Aminophenylamino)(p-tolyl)methyl]acrylic Acid Ethyl
Ester (2e)
Yield: 84%; brown oil.
IR (neat): 1711 (CO2Et), 3402 (NH and NH2) cm–1.
1H NMR (CDCl3, 200 MHz): d = 1.22 (t, J = 7.3 Hz, 3 H, CH2CH3),
2.33 (s, 3 H, ArH), 3.34 (br s, 2 H, NH2), 4.16 (q, J = 7.3 Hz, 2 H,
CH2CH3), 5.38 (s, 1 H, CHNH), 5.88 (s, 1 H, H2C=), 6.35 (s, 1 H,
H2C=), 6.53 (d, J = 7.1 Hz, 1 H, ArH), 6.68–6.79 (m, 3 H, ArH),
7.13 (d, 2 H, J = 8.0 Hz, ArH), 7.27 (d, J = 8.0 Hz, 2 H, ArH).
Preparation of Compounds 2a–h and 16a,b,e
Prepared following a previously published procedure.8
2-[(2-Aminophenylamino)phenylmethyl]acrylic Acid Ethyl
Ester (2a)
MS (ES+): m/z = 311.1 [M + H]+.
Anal. Calcd for C19H22N2O2: C, 73.52; H, 7.14; N, 9.03. Found: C,
73.30; H, 7.01; N, 8.84.
Yield: 63%; brown oil.
IR (neat): 1711 (CO2Et), 3397 (NH and NH2) cm–1.
1H NMR (CDCl3, 300 MHz): d = 1.26 (t, J = 7.0 Hz, 3 H, CH2CH3),
3.41 (br s, 2 H, NH2), 4.18 (q, J = 7.2 Hz, 2 H, CH2CH3), 5.48 (s,
1 H, H2C=), 5.96 (s, 1 H, CHNH), 6.32 (s, 1 H, H2C=), 6.55–6.62
(m, 1 H, ArH), 6.71–6.83 (m, 3 H, ArH), 7.30–7.39 (m, 5 H, ArH).
2-[(2-Aminophenylamino)(4-chlorophenyl)methyl]acrylic Acid
Ethyl Ester (2f)
Yield: 62%; brown oil.
IR (neat): 1714 (CO2Et), 3365 (NH and NH2) cm–1.
1H NMR (CDCl3, 200 MHz): d = 1.25 (t, J = 7.6 Hz, 3 H, CH2CH3),
4.16 (q, J = 7.3 Hz, 2 H, CH2CH3), 5.73 (s, 1 H, H2C=), 5.81 (s, 1 H,
CHNH), 6.26–6.46 (m, 2 H, H2C= and ArH), 6.72–6.73 (m, 3 H,
ArH), 7.18–7.43 (m, 3 H, ArH).
MS (ES+): m/z = 297.0 [M + H]+.
Anal. Calcd for C18H20N2O2: C, 72.95; H, 6.80; N, 9.45. Found: C,
73.19; H, 6.86; N, 9.11.
2-[(2-Aminophenylamino)(2-chlorophenyl)methyl]acrylic Acid
Ethyl Ester (2b)
MS (ES+): m/z = 331.0 [M + H]+.
Yield: 74%; brown oil.
Anal. Calcd for C18H19Cl2N2O2: C, 65.35; H, 5.79; N, 8.47. Found:
C, 65.29; H, 5.70; N, 8.45.
Synthesis 2006, No. 24, 4205–4211 © Thieme Stuttgart · New York

4208
R. Pathak et al.
PAPER
2-[(2-Aminophenylamino)(4-bromophenyl)methyl]acrylic Acid
Ethyl Ester (2g)
Yield: 75%; brown oil.
IR (neat): 1710 (CO2Et), 3350 (NH and NH2) cm–1.
1H NMR (CDCl3, 300 MHz): d = 1.27 (t, J = 7.2 Hz, 3 H, CH2CH3),
4.20 (q, J = 7.2 Hz, 2 H, CH2CH3), 5.40 (s, 1 H, CHNH), 5.89 (s,
1 H, H2C=), 6.40 (s, 1 H, H2C=), 6.54 (d, J = 9.1 Hz, 1 H, ArH),
6.72–6.78 (m, 3 H, ArH), 7.29 (d, J = 9.0 Hz, 2 H, ArH), 7.47 (d,
J = 9.0 Hz, 2 H, ArH).
Preparation of 3a–h and 8a; General Procedure
To a stirred solution of either 2a–h or 7a (1.0 mmol) in dry THF (10
mL) was added NaH (60% suspension in oil; 0.121 g, 2.5 mmol)
and the mixture was heated at reflux for 2 h. On completion, the re-
action mixture was extracted with EtOAc (3 × 20 mL) and H2O (30
mL). The organic layers were pooled, dried over Na2SO4 and con-
centrated to afford a residue, which was purified by silica gel chro-
matography (hexane–EtOAc, 70:30) to yield the pure products.
3-Methylene-4-phenyl-1,3,4,5-tetrahydrobenzo[b][1,4]di-
azepin-2-one (3a)
Yield: 76%; light-yellow solid; mp 175–176 °C.
IR (KBr): 1667 (CONH), 3428 (NH) cm–1.
MS (ES+): m/z = 374.9 [M + H]+.
Anal. Calcd for C18H19BrN2O2: C, 57.61; H, 5.10; N, 7.47. Found:
C, 57.79; H, 5.33; N, 7.48.
1H NMR (CDCl3, 300 MHz): d = 4.01 (s, 1 H, NHCH), 5.18 (s, 2 H,
H2C= and NHCH), 5.99 (s, 1 H, H2C=), 6.78–6.96 (m, 4 H, ArH),
7.23–7.37 (s, 5 H, ArH), 7.93 (s, 1 H, CONH).
13C NMR (CDCl3 + DMSO-d6, 50 MHz): d = 66.4, 121.1, 121.6,
121.7, 122.9, 124.9, 127.3, 128.0, 128.9, 138.4, 141.9, 144.9, 169.6.
2-[(2-Aminophenylamino)(thiophen-2-yl)methyl]acrylic Acid
Ethyl Ester (2h)
Yield: 74%; brown oil.
IR (neat): 1711 (CO2Et), 3401 (NH and NH2) cm–1.
1H NMR (CDCl3, 200 MHz): d = 1.26 (t, J = 7.2 Hz, 3 H, CH2CH3),
3.45 (br s, 2 H, NH2), 4.21 (q, J = 7.3 Hz, 2 H, CH2CH3), 5.64 (s,
1 H, CHNH), 5.90 (s, 1 H, H2C=), 6.36 (s, 1 H, H2C=), 6.58–6.61
(m, 1 H, ArH), 6.74 (s, 3 H, ArH), 6.97 (s, 2 H, ArH), 7.22 (s, 1 H,
ArH).
MS (ES+): m/z = 251.0 [M + H]+.
Anal. Calcd for C16H14N2O: C, 76.78; H, 5.64; N, 11.19. Found: C,
76.80; H, 5.45; N, 10.87.
4-(2-Chlorophenyl)-3-methylene-4-phenyl-1,3,4,5-tetrahydro-
benzo[b][1,4]diazepin-2-one (3b)
MS (ES+): m/z = 302.9 [M + H]+.
Yield: 84%; yellow solid; mp 182–183 °C.
IR (KBr): 1668 (CONH), 3349 (NH) cm–1.
Anal. Calcd for C16H18N2O2S: C, 63.55; H, 6.00; N, 9.26. Found: C,
63.76; H, 6.20; N, 8.92.
1H NMR (CDCl3, 300 MHz): d = 4.18 (s, 1 H, NHCH), 5.43 (s, 1 H,
H2C=), 5.75 (s, 1 H, CHNH), 6.14 (s, 1 H, H2C=), 6.82–6.84 (m,
1 H, ArH), 6.90–6.97 (m, 2 H, ArH), 7.20–7.23 (m, 2 H, ArH), 7.28
(s, 1 H, ArH), 7.36–7.39 (m, 1 H, ArH), 7.50–7.52 (m, 1 H, ArH),
8.08 (s, 1 H, CONH).
13C NMR (CDCl3, 50 MHz): d = 63.8, 121.5, 121.7, 123.3, 125.1,
125.4, 127.6, 129.3, 129.6, 130.1, 133.2, 138.2, 139.1, 142.6, 169.7.
2-[(2-Aminophenylamino)phenylmethyl]acrylonitrile (16a)
Yield: 52%; brown oil.
IR (neat): 2225 (CN), 3400 (NH and NH2) cm–1.
1H NMR (CDCl3, 200 MHz): d = 3.08 (br s, 2 H, NH2), 5.04 (s, 1 H,
CHNH), 6.05 (s, 1 H, H2C=), 6.11 (s, 1 H, H2C=), 6.55–6.58 (m,
1 H, ArH), 6.74–6.81 (m, 3 H, ArH), 7.39–7.43 (m, 5 H, ArH).
MS (ES+): m/z = 250.1 [M + H]+.
MS (ES+): m/z = 285.1 [M + H]+.
Anal. Calcd for C16H15N3: C, 77.08; H, 6.06; N, 16.85. Found: C,
76.88; H, 6.21; N, 16.98.
Anal. Calcd for C16H13ClN2O: C, 67.49; H, 4.60; N, 9.84. Found: C,
67.67; H, 4.76; N, 9.64.
2-[(2-Aminophenylamino)(2-chlorophenyl)methyl]acrylo-
nitrile (16b)
Yield: 63%; brown oil.
IR (neat): 2209 (CN), 3377 (NH and NH2) cm–1.
4-(2-Fluorophenyl)-3-methylene-4-phenyl-1,3,4,5-tetrahydro-
benzo[b][1,4]diazepin-2-one (3c)
Yield: 75%: yellow solid; mp 160–162 °C.
IR (KBr): 1660 (CONH), 3316 (NH) cm–1.
1H NMR (CDCl3, 200 MHz): d = 3.93 (br s, 2 H, NH2), 5.57 (s, 1 H,
CHNH), 6.01 (s, 1 H, H2C=), 6.11 (s, 1 H, H2C=), 6.47–6.49 (m,
1 H, ArH), 6.71–6.77 (m, 3 H, ArH), 7.28–7.33 (m, 2 H, ArH),
7.43–7.53 (m, 2 H, ArH).
1H NMR (CDCl3, 200 MHz): d = 4.07 (br s, 1 H, NHCH), 5.39 (s,
1 H, H2C=), 5.63 (s, 1 H, CHNH), 6.10 (s, 1 H, H2C=), 6.83–6.96
(m, 4 H, ArH), 7.03–7.12 (m, 1 H, ArH), 7.23–7.24 (m, 2 H, ArH),
7.44–7.45 (m, 1 H, ArH), 8.03 (s, 1 H, CONH).
MS (ES+): m/z = 284.2 [M + H]+.
MS (ES+): m/z = 269.2 [M + H]+.
Anal. Calcd for C16H14ClN3: C, 67.72; H, 4.97; N, 14.81. Found: C,
67.93; H, 5.04; N, 14.89.
Anal. Calcd for C16H13FN2O: C, 71.63; H, 4.88; N, 10.44. Found:
C, 71.48; H, 5.11; N, 10.25.
2-[(2-Aminophenylamino)(p-tolyl)methyl]acrylonitrile (16e)
Yield: 56%; brown oil.
IR (neat): 2225 (CN), 3411 (NH and NH2) cm–1.
1H NMR (CDCl3, 200 MHz): d = 2.37 (s, 3 H, CH3), 3.39 (br s, 2 H,
NH2), 3.84 (br s, 1 H, CHNH), 5.04 (d, J = 3.6 Hz, 2 H, CHNH),
6.04 (d, J = 1.0 Hz, 1 H, H2C=), 6.06 (s, 1 H, H2C=), 6.55–6.57 (m,
1 H, ArH), 6.74–6.81 (m, 3 H, ArH), 7.10 (d, J = 8.0 Hz, 2 H, ArH),
7.31 (d, J = 8.0 Hz, 2 H, ArH).
4-(2,4-Dichlorophenyl)-3-methylene-1,3,4,5-tetrahydro-
benzo[b][1,4]diazepin-2-one (3d)
Yield: 73%; yellow solid; mp 162–164 °C.
IR (KBr): 1650 (CONH), 3411 (NH) cm–1.
1H NMR (CDCl3, 200 MHz): d = 4.14 (d, J = 3.6 Hz, 1 H, NHCH),
5.43 (s, 1 H, H2C=), 5.70 (d, J = 3.6 Hz, 1 H, CHNH), 6.07 (s, 1 H,
H2C=), 6.80–6.84 (m, 1 H, ArH), 6.92–6.98 (m, 3 H, ArH), 7.15–
7.20 (dd, J1 = 1.8 Hz, J2 = 8.40 Hz, 1 H, ArH), 7.38 (d, J = 1.8 Hz,
1 H, ArH), 7.44–7.49 (m, 1 H, ArH), 8.07 (s, 1 H, CONH).
MS (ES+): m/z = 264.2 [M + H]+.
13C NMR (CDCl3, 50 MHz): d = 63.8, 121.7, 121.8, 123.6, 124.9,
125.7, 127.9, 129.9, 130.2, 133.8, 134.7, 137.7, 137.9, 142.3, 169.7.
Anal. Calcd for C17H17N3: C, 77.54; H, 6.51; N, 15.96. Found: C,
77.75; H, 6.40; N, 16.09.
Synthesis 2006, No. 24, 4205–4211 © Thieme Stuttgart · New York

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Synthesis of Substituted Diazepinones
4209
MS (ES+): m/z = 319.1 [M + H]+.
Anal. Calcd for C14H12N2OS: C, 65.60; H, 4.72; N, 10.93. Found:
C, 65.51; H, 4.79; N, 11.12.
Anal. Calcd for C16H12Cl2N2O: C, 60.21; H, 3.79; N, 8.78. Found:
C, 60.50; H, 3.95; N, 8.62.
2-[2-Amino-4,5-dichlorophenylamino)phenylmethyl]acrylic
Acid Ethyl Ester (8a)
Yield: 83%; white solid; mp 138–140 °C.
IR (KBr): 1655 (CONH), 3430 (NH) cm–1.
4-(4-Methylphenyl)-3-methylene-4-phenyl-1,3,4,5-tetrahydro-
benzo[b][1,4]diazepin-2-one (3e)
Yield: 74%; white solid; mp 192–194 °C.
IR (KBr): 1665 (CONH), 3421 (NH) cm–1.
1H NMR (CDCl3, 300 MHz): d = 2.19 (s, 6 H, 2 × CH3), 3.85 (br s,
1 H, CHNH), 5.19 (s, 2 H, NHCH and H2C=), 5.95 (s, 1 H, H2C=),
6.65 (d, J = 2.2 Hz, 2 H, ArH), 7.31–7.42 (m, 5 H, ArH), 7.42 (s,
1 H, CONH).
13C NMR (CDCl3, 50 MHz): d = 19.3, 19.5, 60.8, 122.7, 123.4,
127.1, 127.6, 128.4, 129.2, 131.1, 133.9, 136.4, 142.2, 145.2, 170.3.
1H NMR (CDCl3, 200 MHz): d = 2.32 (s, 3 H, CH3), 3.91 (br s, 1 H,
CHNH), 5.12 (s, 1 H, H2C=), 5.23 (s, 1 H, CHNH), 6.02 (s, 1 H,
H2C=), 6.80–6.91 (m, 2 H, ArH), 6.93–7.08 (m, 1 H, ArH), 7.09–
7.12 (m, 2 H, ArH), 7.15–7.29 (m, 3 H, ArH), 8.01 (s, 1 H, CONH).
13C NMR (CDCl3, 50 MHz): d = 21.0, 65.0, 120.5, 121.1, 121.86,
124.3, 126.9, 128.3, 129.0, 136,7, 138.3, 138.9, 145.0, 169.0.
MS (ES+): m/z = 279.2 [M + H]+.
MS (ES+): m/z = 265.1 [M + H]+.
Anal. Calcd for C18H18N2O: C, 76.78; H, 5.64; N, 11.19. Found: C,
76.80; H, 5.45; N, 10.97.
Anal. Calcd for C17H16N2O: C, 77.25; H, 6.10; N, 10.60. Found: C,
77.31; H, 5.88; N, 10.39.
Preparation of 4–6a; General Procedure
To a solution of the appropriate acetate (1.0 mmol) in dry THF (15
mL) was added DABCO (1.02 g, 4.5 mmol) at r.t. and the mixture
was stirred for 10 min. During this time, the appropriate 2-nitro-
aniline (1.0 mmol) was dissolved in dry THF (10 mL) and NaH
(0.121 g, 2.5 mmol) was added at r.t. under stirring. The mixture of
DABCO and the Baylis–Hillman acetate was added dropwise to the
nitroaniline mixture, maintaining dry conditions. The reaction was
allowed to proceed at r.t. for 1.5 h. On completion, the reaction mix-
ture was extracted with EtOAc (3 × 20 mL) and H2O (30 mL). The
organic layers were pooled, dried over Na2SO4 and concentrated in
vacuo to afford a residue, which was purified by silica gel chroma-
tography (hexane–EtOAc, 95:5) to yield the pure products.
4-(4-Chlorophenyl)-3-methylene-4-phenyl-1,3,4,5-tetrahydro-
benzo[b][1,4]diazepin-2-one (3f)
Yield: 78%; light-yellow solid; mp 190–192 °C.
IR (KBr): 1658 (CONH), 3298 (NH) cm–1.
1H NMR (CDCl3, 200 MHz): d = 4.03 (s, 1 H, CHNH), 5.26 (s, 2 H,
H2C= and NHCH), 5.97 (s, 1 H, H2C=), 6.82–7.04 (m, 4 H, ArH),
7.31 (s, 4 H, ArH), 8.07 (s, 1 H, CONH).
13C NMR (CDCl3, 50 MHz): d = 66.1, 121.3, 121.7, 122.2, 123.3,
125.2, 128.8, 129.1, 133.8, 138.0, 140.4, 144.5, 169.6.
MS (ES+): m/z = 285.0 [M + H]+, 287.0 [M + 3]+.
Anal. Calcd for C16H13ClN2O: C, 67.49; H, 4.60; N, 9.84. Found: C,
67.60; H, 4.71; N, 10.01.
2-{[(4,5-Dimethyl-2-nitrophenyl)amino]phenylmethyl}acrylic
Acid Ethyl Ester (5a)
Yield: 71%; yellow solid; mp 114–116 °C.
IR (KBr): 1717 (CO2Et), 3377 (NH) cm–1.
4-(4-Bromophenyl)-3-methylene-4-phenyl-1,3,4,5-tetrahydro-
benzo[b][1,4]diazepin-2-one (3g)
Yield: 64%; light-yellow solid; mp 196–198 °C.
IR (KBr): 1650 (CONH), 3312 (NH) cm–1.
1H NMR (CDCl3, 200 MHz): d = 1.23 (t, J = 7.2 Hz, 3 H, CH2CH3),
2.16 (s, 3 H, CH3), 2.21 (s, 3 H, CH3), 4.20 (q, J = 7.2 Hz, 2 H,
CH2CH3), 5.67 (s, 1 H, CHNH), 5.70 (s, 1 H, CHNH), 5.82 (s, 1 H,
H2C=), 6.41 (s, 1 H, H2C=), 6.54 (s, 1 H, ArH), 7.28–7.38 (m, 5 H,
ArH), 7.95 (s, 1 H, ArH).
13C NMR (CDCl3, 50 MHz): d = 14.4, 19.0, 21.2, 58.1, 61.6, 115.5,
125.7, 126.7, 126.9, 127.7, 128.5, 129.4, 130.9, 139.8, 140.27,
142.8, 147.6, 166.2.
1H NMR (CDCl3, 300 MHz): d = 4.04 (br s, 1 H, CHNH), 5.24 (s,
1 H, H2C=), 5.28 (s, 1 H CHNH), 6.00 (s, 1 H, H2C=), 6.84–7.05
(m, 4 H, ArH), 7.28 (d, J = 8.4 Hz, 2 H, ArH), 7.47 (d, J = 8.4 Hz,
2 H, ArH), 7.78 (s, 1 H, CONH).
13C NMR (CDCl3 + DMSO-d6, 50 MHz): d = 70.1, 125.8, 126.1,
126.3, 126.5, 127.6, 129.7, 133.4, 134.1, 136.5, 143.0, 146.3, 149.5,
174.1.
MS (ES+): m/z = 354.9 [M + H]+.
MS (ES+): m/z = 329.1 [M + H]+.
Anal. Calcd for C20H22N2O4: C, 67.78; H, 6.26; N, 7.90. Found: C,
67.90; H, 6.39; N, 7.67.
Anal. Calcd for C16H13BrN2O: C, 58.38; H, 3.98; N, 8.51. Found: C,
58.54; H, 4.10; N, 8.30.
2-{[(4,5-Dichloro-2-nitrophenyl)amino]phenylmethyl}acrylic
Acid Ethyl Ester (6a)
Yield: 73%; orange solid; mp 114–116 °C.
IR (KBr): 1717 (CO2Et), 3377 (NH) cm–1.
3-Methylene-4-thiophene-1,3,4,5-tetrahydrobenzo[b][1,4]di-
azepin-2-one (3h)
Yield: 59%; brown solid; mp 182–184 °C.
IR (KBr): 1666 (CONH), 3418 (NH) cm–1.
1H NMR (CDCl3, 200 MHz): d = 1.27 (t, J = 7.4 Hz, 3 H, CH2CH3),
4.21 (q, J = 7.1 Hz, 2 H, CH2CH3), 5.59 (s, 1 H, CHNH), 5.63 (s,
1 H, CHNH), 5.81 (s, 1 H, H2C=), 6.45 (s, 1 H, H2C=), 6.88 (s, 1 H,
ArH), 7.37–7.43 (m, 5 H, ArH), 8.30 (s, 1 H, ArH).
13C NMR (CDCl3, 50 MHz): d = 14.3, 58.6, 61.8, 116.3, 120.1,
127.2, 127.6, 128.1, 128.9, 129.6, 131.6, 138.6, 139.9, 141.6, 142.9,
165.8.
1H NMR (CDCl3 + DMSO-d6, 200 MHz): d = 5.06 (br, 1 H,
CHNH), 5.16 (s, 1 H, H2C=), (s, 1 H, H2C=), 5.27 (d, J = 4.0 Hz,
1 H, CHNH), 5.69 (s, 1 H, ArH), 6.42–6.66 (m, 5 H, ArH and Het-
H), 6.93 (d, J = 3.0 Hz, 1 H, Het-H), 7.30 (s, 1 H, Het-H), 9.01 (s,
1 H, CONH).
13C NMR (CDCl3, 50 MHz): d = 65.4, 125.4, 126.0, 128.3, 129.4,
129.9, 130.7, 132.3, 133.6; 142.9, 149.3, 152.1, 172.8.
MS (ES+): m/z = 394.7 [M + H]+.
MS (ES+): m/z = 257.0 [M + H]+ .
Anal. Calcd for C18H16Cl2N2O4: C, 54.70; H, 4.08; N, 7.09. Found:
C, 54.88; H, 3.80; N, 6.90.
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4210
R. Pathak et al.
PAPER
Preparation of 9–11a; General Procedure
MS (ES+): m/z = 319.1 [M + H]+.
To a solution of appropriate 2-nitroaniline (1.0 mmol) in MeOH (10
mL) was added SnCl2·2H2O (1.73 g, 5.0 mmol) and the reaction
mixture was heated at reflux with stirring for 12 h in a nitrogen at-
mosphere. On completion, MeOH was evaporated and the residue
was made alkaline with saturated NaHCO3 and then EtOAc (100
mL) was added. The suspension was passed through a bed of celite
and the filtrate was partitioned in a separating funnel. The organic
layer was separated, dried (Na2SO4) and concentrated, to afford a
residue which was purified by silica gel chromatography (hexane–
EtOAc, 80:20) to yield pure product.
Anal. Calcd for C18H16Cl2N2O4: C, 60.21; H, 3.79; N, 8.78. Found:
C, 60.40; H, 4.01; N, 8.55.
Preparation of 2 and 7a; General procedure
To a stirred solution of appropriate 2-nitroaniline (1.0 mmol) in
MeOH (10 mL) at r.t. was added zinc powder (0.150 g, 1.5 mmol),
followed by HCO2NH4 (0.289 g, 3.0 mmol). After the reaction was
complete (monitored by TLC), MeOH was evaporated in vacuo and
the residue was dissolved in EtOAc (20 mL). This was then passed
through a bed of celite and the filtrate was extracted with EtOAC
(2 × 20 mL) and washed with H2O (30 mL). The organic layers
were combined, dried over Na2SO4 and evaporated to yield the
crude product which was purified by silica gel chromatography
(hexane–EtOAc, 80:20) to afford the pure compounds.
2-{[(2-Amino-4,5-dimethylphenyl)amino]methyl}-3-phenyl-
acrylic Acid Ethyl Ester (10a)
Yield: 72%; brown oil.
IR (neat): 1703 (CO2Et), 3343 (NH and NH2) cm–1.
2-[2-Amino-4,5-dichlorophenylamino)phenylmethyl]acrylic
Acid Ethyl Ester (7a)
Yield: 60%; brown oil.
IR (neat): 1748 (CO2Et), 3407 (NH and NH2) cm–1.
1H NMR (CDCl3, 200 MHz): d = 1.22 (t, J = 7.2 Hz, 3 H, CH2CH3),
2.12 (s, 6 H, 2 × CH3), 3.80 (br s, 1 H, NH), 4.15 (q, J = 7.0 Hz, 2 H,
CH2CH3), 5.37 (s, 1 H, CHNH), 5.90 (s, 1 H, H2C=), 6.35 (d,
J = 4.8 Hz, 2 H, H2C= and ArH), 6.54 (s, 1 H, ArH), 7.29–7.37 (m,
5 H, ArH).
1H NMR (CDCl3, 200 MHz): d = 1.34 (t, J = 7.2 Hz, 3 H, CH2CH3),
2.08 (s, 3 H, CH3), 2.13 (s, 3 H, CH3), 3.40 (br s, 2 H, NH2), 4.08 (s,
2 H, CH2NH), 4.30 (q, J = 7.2 Hz, 2 H, CH2CH3), 6.32 (s, 1 H,
ArH), 6.53 (s, 1 H, ArH), 7.37–7.45 (m, 5 H, ArH), 7.90 (s, 1 H,
CH2=).
MS (ES+): m/z = 325.1 [M + H]+.
Anal. Calcd for C20H24N2O2: C, 74.04; H, 7.46; N, 8.64. Found: C,
74.19; H, 7.44; N, 8.70.
2-{[(2-Amino-4,5-dichlorophenyl)amino]methyl}-3-phenyl-
acrylic Acid Ethyl Ester (11a)
Yield: 68%; brown oil.
IR (neat): 1710 (CO2Et), 3418 (NH and NH2) cm–1.
MS (ES+): m/z = 325.2 [M + H]+.
Anal. Calcd for C20H24N2O2: C, 74.04; H, 7.46; N, 8.64. Found: C,
73.89; H, 7.65; N, 8.49.
Preparation of 18a–c; General Procedure
1H NMR (CDCl3, 200 MHz): d = 1.32 (t, J = 7.2 Hz, 3 H, CH2CH3),
3.40 (s, 2 H, NH2), 4.07 (s, 2 H, CH2), 4.27 (q, J = 7.2 Hz, 2 H,
CH2CH3), 6.45 (s, 1 H, ArH), 6.54 (s, 1 H, ArH), 7.36–7.40 (m, 5 H,
ArH), 7.92 (s, 1 H, H2C=).
Gaseous HCl (~1.5 mmol) was bubbled through a solution of the ap-
propriate nitrile (1.0 mmol) in dry CH2Cl2 (10 mL) and EtOH (1.0
mmol, 0.12 mL) at 0 °C. The reaction was kept at 0 °C for 3 h then
allowed to warm to r.t. and continued for another 5 h. The excess
CH2Cl2 was removed under a stream of nitrogen, then dry Et2O (5
mL) was added to the residue and the flask was allowed to stand at
0 °C for 24 h. The resultant solid was filtered and dried over P2O5
to afford the final compounds as the hydrochloride salt.
MS (ES+): m/z = 365.2 [M + H]+.
Anal. Calcd for C18H18Cl2N2O2: C, 59.19; H, 4.97; N, 7.67. Found:
C, 58.95; H, 5.10; N, 7.88
Preparation of 12–14a; General Procedure
These compounds were prepared following the procedure described
for 3a–h.5b
3-Benzylidine-4,5-dihydro-3H-benzo[b][1,4]diazepin-2-yl-
amine Hydrochloride (18a)
Yield: 70%; brown solid, mp 178–179 °C.
IR (KBr): 3408 (NH and NH2) cm–1.
1H NMR (CD3OD, 300 MHz): d = 3.35 (s, 2 H, CH2NH), 7.09–
7.134 (m, 4 H, ArH), 7.14–7.18 (m, 5 H, ArH), 7.45 (s, 1 H, H2C=).
3-Benzylidene-7,8-dimethyl-1,3,4,5-tetrahydrobenzo[b][1,4]di-
azepin-2-one (13a)
Yield: 70%; white solid; mp 194–196 °C.
IR (KBr): 1632 (CONH), 3267 (NH) cm–1.
1H NMR (CDCl3, 200 MHz): d = 2.16 (s, 6 H, 2 × CH3), 3.85 (br s,
1 H, CHNH), 4.10 (s, 2 H, CH2), 6.55 (s, 1 H, ArH), 6.65 (s, 1 H,
ArH), 7.34–7.37 (m, 5 H, ArH), 7.79 (s, 1 H, H2C=), 7.92 (br s, 1 H,
CONH).
MS (ES+): m/z = 250.0 [M + H]+.
Anal. Calcd for C16H16ClN3: C, 67.25; H, 5.64; N, 14.70. Found: C,
66.96; H, 5.88; N, 14.47.
3-(2-Chlorobenzylidine)-4,5-dihydro-3H-benzo[b][1,4]di-
azepin-2-ylamine Hydrochloride (18b)
MS (ES+): m/z = 279.2 [M + H]+.
Yield: 77%; white solid; mp 216–218 °C.
IR (KBr): 3410 (NH and NH2) cm–1.
Anal. Calcd for C20H22N2O4: C, 77.67; H, 6.52; N, 10.06. Found: C,
77.32; H, 6.49; N, 10.22.
1H NMR (CD3OD, 300 MHz): d = 3.33 (s, 2 H, CH2NH), 7.17–7.20
3-Benzylidene-7,8-dichloro-1,3,4,5-tetrahydrobenzo[b][1,4]di-
azepin-2-one (14a)
Yield: 76%; white solid; mp 118–120 °C.
(m, 4 H, ArH), 7.17–7.20 (m, 6 H, ArH and H2C=).
MS (ES+): m/z = 284 [M + H]+.
IR (KBr): 1657 (CONH), 3374 (NH and NH2) cm–1.
Anal. Calcd for C16H15Cl2N3·H2O: C, 56.82; H, 5.07; N, 12.42.
Found: C, 57.13; H, 4.89; N, 12.35.
1H NMR (CDCl3, 200 MHz): d = 4.12 (s + br s, 3 H, CHNH and
CH2), 6.83 (s, 1 H, ArH), 7.07 (s, 1 H, ArH), 7.35–7.39 (m, 5 H,
ArH), 7.87 (s, 1 H, H2C=), 8.54 (s, 1 H, CONH).
13C NMR (DMSO-d6, 50 MHz): d = 47.8, 124.3, 126.2, 126.8,
130.3, 132.7, 133.8, 134.6, 137.9, 140.4, 141.8, 145.2, 174.6.
3-(4-Methylbenzylidine)-4,5-dihydro-3H-benzo[b][1,4]di-
azepin-2-ylamine Hydrochloride (18e)
Yield: 74%; brown solid; mp 199–201 °C.
Synthesis 2006, No. 24, 4205–4211 © Thieme Stuttgart · New York

PAPER
Synthesis of Substituted Diazepinones
4211
IR (KBr): 3420 (NH and NH2) cm–1.
Synlett 2005, 2623. (f) Lee, K. Y.; Gowrisankar, S.; Kim, J.
N. Bull. Korean Chem. Soc. 2005, 26, 1481.
(g) Shanmugam, P.; Rajasingh, P. Tetrahedron Lett. 2005,
46, 3369. (h) Mix, S.; Blechert, S. Org. Lett. 2005, 7, 2015.
(i) Du, Y.; Feng, J.; Lu, X. Org. Lett. 2005, 7, 1987.
(j) Kim, S. C.; Lee, H. S.; Lee, Y. J.; Kim, J. N. Tetrahedron
Lett. 2006, 47, 5681.
1H NMR (CD3OD, 300 MHz): d = 2.37 (s, 3 H, CH3), 3.32 (s, 1 H,
CH2NH), 3.78 (d, 2 H, J = 4.5 Hz, CH2NH), 6.85–6.90 (m, 4 H,
ArH), 7.12–7.37 (m, 4 H, ArH), 7.64 (s, 1 H, H2C=).
MS (ES+): m/z = 264 [M + H]+.
Anal. Calcd for C17H18ClN3·H2O: C, 64.25; H, 6.34; N, 13.22.
Found: C, 64.38; H, 6.66; N, 12.97.
(3) (a) Singh, V.; Batra, S. Synthesis 2006, 63. (b) Singh, V.;
Yadav, G. P.; Maulik, P. R.; Batra, S. Tetrahedron 2006, 62,
8731. (c) Singh, V.; Kanojiya, S.; Batra, S. Tetrahedron
2006, accepted.
(4) Horton, D. A.; Bourne, G. T.; Smythe, M. L. Chem. Rev.
2003, 103, 893; and references cited therein.
(5) (a) Chuang, T.-H.; Sharpless, K. B. Org. Lett. 2000, 23,
3555. (b) Kim, J. M.; Lee, K. Y.; Kim, J. N. Bull. Korean
Chem. Soc. 2002, 23, 1055. (c) Herpin, T. F.; van Kirk, K.
G.; Salvino, J. M.; Yu, S. T.; Labaudiniere, R. F. J. Comb.
Chem. 2000, 2, 513. (d) Schwarz, M. K.; Tumelty, D.;
Gallop, M. A. Tetrahedron Lett. 1998, 39, 8397. (e) Lee, J.;
Gauthier, D.; Rivero, R. A. J. Org. Chem. 1999, 64, 3060.
(6) Patra, A.; Batra, S.; Kundu, B.; Joshi, B. S.; Roy, R.;
Bhaduri, A. P. Synthesis 2001, 276.
Acknowledgment
Two of the authors (R.P. and S.N.) gratefully acknowledge the fi-
nancial support from CSIR and UGC, New Delhi, respectively, in
the form of fellowship. This work was supported by financial grant
from DST, N. Delhi.
References
(1) CDRI Communication No. 7050.
(2) (a) Basavaiah, D.; Rao, A. J.; Satyanarayana, T. Chem. Rev.
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Tetrahedron Lett. 2006, 47, 73. (c) Coelho, F.; Veronese,
D.; Pavam, C. H.; de Paula, V. I.; Buffon, R. Tetrahedron
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(7) Gowda, D.; Mahesh, B.; Shankare, G. Indian J. Chem., Sect.
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Synthesis 2006, No. 24, 4205–4211 © Thieme Stuttgart · New York