A facile hybrid 'flow and batch' access to substituted 3,4-dihydro-2: H -benzo [b] [1,4]oxazinones

Article abstract of DOI:10.1039/c6ob01153e

We describe a simple flow chemistry approach to libraries of ethyl 3-oxo-2-(substituted-phenylamino)-3,4-dihydro-2H-benzo[b][1,4]oxazine-6-carboxylates (12a-l) and N-ethyl-3-oxo-2-(substituted-phenylamino)-3,4-dihydro-2H-benzo[b][1,4]oxazine-6-carboxamides (13a-l) in 38-87% yields. This scaffold is poorly described in the chemical literature. Screening against a panel of 11 cancer and one normal cell line showed that the amide linked library 13a-l was devoid of toxicity. Whereas the ester linked analogues 12b, 12c, 12g, 12j and 12l were highly cytotoxic with growth inhibition (GI₅₀) values from 0.34 to >50 μM across all cell lines, with the 2-OH-Ph substituted 12l analogue presenting with sub-micromolar potency against the A2780 (ovarian; 0.34 ± 0.04 μM), BEC-2 (glioblastoma; 0.35 ± 0.06 μM), MIA (pancreas; 0.91 ± 0.054 μM) and SMA (murine glioblastoma; 0.77 ± 0.029 μM) carcinoma cell lines. Interestingly, the U87 glioblastoma cell line showed inherent resistance to growth inhibition by all analogues (GI₅₀ 32 to >50 μM) while the A2780 cells were highly sensitive (GI₅₀ 3.8-0.34 μM), suggesting that the analogues developed herein may be valuable lead compounds for the development of ovarian carcinoma specific cytotoxic agents. The differences in amide versus ester cytotoxicity was consitent with esterase cleaveage to release the cytotoxic warhead.

Full text of DOI:10.1039/c6ob01153e

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A Facile hybrid ‘flow and batch’ access to substituted 3,4-dihydro-
2H-benzo[b][1,4]oxazinones
Received 00th January 20xx,
Accepted 00th January 20xx
Andrew J. S. Lin,a Cecilia Russell,a Jennifer R. Baker,a Shelby L. Fraileya,b
Jennette A Sakoff c and Adam McCluskeya*
DOI: 10.1039/x0xx00000x
www.rsc.org/
We describe a simple flow chemistry approach to libraries of ethyl 3-oxo-2-(substituted-phenylamino)-3,4-dihydro-2H-
benzo[b][1,4]oxazine-6-carboxylates
(12a-l)
and
N-ethyl-3-oxo-2-(substituted-phenylamino)-3,4-dihydro-2H-
benzo[b][1,4]oxazine-6-carboxamides (13a-l) in 38-87% yields. This scaffold is poorly described in the chemical literature.
Screening against a panel of 11 cancer and one normal cell line showed that the amide linked library 13a-l was devoid of
toxicity. Whereas the ester linked analogues 12b, 12c, 12g, 12j and 12l were highly cytotoxic with growth inhibition (GI50
)
values from 0.34 to > 50 ꢀM across all cell lines, with the 2-OH-Ph substituted 12l analogue presenting with sub-
micromolar potency against the A2780 (ovarian; 0.34 ± 0.04 ꢀM), BEC-2 (glioblastoma; 0.35 ± 0.06 ꢀM), MIA (pancreas;
0.91 ± 0.054 ꢀM) and SMA (murine glioblastoma; 0.77 ± 0.029 ꢀM) carcinoma cell lines. Interestingly, the U87
glioblastoma cell line showed inherent resistance to growth inhibition by all analogues (GI50 32 to > 50 µM) while the
A2780 cells were highly sensitive (GI50 3.8 – 0.34 ꢀM), suggesting that the analogues developed herein may be valuable
lead compounds for the development of ovarian carcinoma specific cytotoxic agents. The differences in amide versus ester
cytotoxicity was consitent with esterase cleaveage to release the cytotoxic warhead.
aniliobenzoxazinone derivatives and their biological activity
has only ever been the subject of limited investigations.
Similarly, the only report of 2-N-substituted benzoxazinones,
by Ilaš and Kikelji, presented only one derivative (3
, Figure 1).7
Introduction
The medicinal chemistry toolbox is replete with a wide array of
robust synthetic approaches typically geared towards the rapid
development of structure activity relationship (SAR) data.
Such approaches generally use a common central scaffold with
pendant arms that best position key pharmacophore moieties
to engage with binding site residues. The medicinal chemistry
1,2
toolkit has been reviewed by Roughly and Walters,
as has
bioisosteric approaches to potency enhancements.3,4
Independent of the target, access to a core scaffold is
imperative and often requires significant synthetic effort to
access in a quantity appropriate for SAR development. We
recently commenced a program that sought access to a 2-
(amino)-3,4-dihydro-2H-benzo[b][1,4]oxazine-6-carboxamide
(e.g. 1-3, Figure 1) and were surprised to discover that robust
chemistry permitting rapid access was poorly described in the
literature.5,6
Figure
benzo[b][1,4]oxazine-6-carboxamides (
benzo[b][1,4]oxazin-2-yl)amino)benzonitrile (
1
.
Target scaffold, 6- and 7- substituted 2-(amino)-3,4-dihydro-2H-
1
and ) and 4-((3-oxo-3,4-dihydro-2H-
2
3).
Recently there has been considerable progress in the use
of flow chemistry approaches in multi-step synthesis,8-17 the
synthesis
hydrogenations23 and in the use of unstable and /or dangerous
reagents.14-16,24,25 Herein, we envisaged
simple flow
of
drug
like
molecules,18-22
selective
Prior to this investigation, the synthesis of 2-
a
chemistry approach allowing a scalable access to two key
intermediates for use in either flow chemistry library
development or using robust batch approaches.1,2
Herein we report on our efforts in this area and highlight
the scope of this approach in the development of targeted
libraries of 1 and 2.
Results and discussion
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Our investigations commenced with the esterification of 4-
O
O
NO2
OH
NH2
OH
hydroxy-3-nitrobenzoic acid (
4
). Batch esterification resulted in
to the ethyl ester (ESI†). Under
flow conditions (0.05M ethanolic
, H2SO4, 140 °C, 1 mL.min-1)
was afforded in 69% yield (2 g.h-1). Alternatively simple
amines were readily installed via flow amide coupling
conditions, e.g.
, in an improved isolated yield (0.38 g.h-1),
when compared to batch synthesis ca. 77% vs 50% (Scheme 1).
R1
R1
Cl
10% Pd/C
incomplete conversion of
4
5
4
7; R1 = OEt
5; R1 = OEt
8; R1 = NHEt
6; R1 = NHEt
5
Cl
Cl
O
6
9
Cl
O
O
O
Cl
NaHCO3
H
N
O
NH
OH
R1
R1
O
O
i
NO2
OH
NO2
OH
O
OH
EtO
HO
10; R1 = OEt
R1 = OEt
11; R1 = NHEt
R1 = NHEt
Scheme 2. Reagents and conditions. (i) ThalesNano H-Cube Pro™, 10% Pd/C (70
mm cartridge), CH3CN, 50 °C, 50 bar H2 pressure, 3 ml.min-1; (ii) VapourTec
100 °C, 0.75 mL.min-1, 5 bar.
5
4
easy-MedChem, 9
, 2 x 10 mL reactor, 0.75 mL.min-1, 18 °C; (iii) 2 x 10 mL reactor,
COMU
iPr2NEt
EtNH2
ii
O
Et
NO2
OH
N
H
6
Scheme 3. Reagents and conditions. (i) R2NH2, Na2SO4; (ii) anhydrous Na2SO4
Scheme 1
.
Reagents and conditions. (i) EtOH, H2SO4, 140 °C, 1 mL.min-1; (ii),
COMU, iPr2NEt, EtNH2, DMF 18 °C, 1 mL.min-1.
There were however limitations to this flow transformation
(Scheme 3), in some instances where aniline coupling partners
possessed an additional nucleophiles, i.e. aminophenol, the
flow dehydration reaction failed to proceed to completion in
the same time as batch conditions. Moreover we noted that
the presence of the electron withdrawing 2-bromophenyl, or
2-carboxyphenyl moiety failed to produce any evidence of the
desired 3,4-dihydro-2H-benzo[b][1,4]oxazines, supporting the
importance of the amine nucleophilicity.
Optimised H-Cube ProTM reduction of
5/6 (0.01 M 5/6 in
EtOAc, 10% Pd/C, 50 °C, 50 bar H2, 3 mL.min-1) afforded the
corresponding anilines
yield; ESI†). The H-Cube ProTM eluent stream containing
was introduced into twin streams of dichloroacetyl chloride
7
and 8, in a single pass (1.9 g.h-1; 98%
and
7
8
9
in 1,1-dichloroethane (0.1 M, 0.75 mL.min-1, 18 °C) and
NaHCO3 (0.5 M, 0.75 mL.min-1, 18 °C) and passed through two
4 mL PFA coils (18 °C) to selectively N-acylate the aniline NH2
moiety. Again without isolating the product stream, the
biphasic solution was flowed into two 10 mL PFE coils,
maintained at 100 °C and 5 bar backpressure, to afford the
desired hemiacetals 10 and 11 in 44 and 52% yield, 0.5 and
0.36 g.h-1, respectively. Although the dichloroacetamide
adduct could be isolated in high yield (94%), it was determined
In a similar manner, we were not able to exploit the
hemiacetal moiety to access 2-N-alkylated benzoxazinone
derivatives with the reaction failing to go to completion, by
both flow and batch approaches, the product was found to be
unstable and decomposed during attempted chromatography
(SiO2) (Scheme 4).
that the direct conversion of anilines
7 and 8 to hemiacetals 10
and 11 by flow synthesis allowed continuous supply of scaffold
for further derivatisation and increased the overall synthetic
efficiency (Scheme 2).
With a scalable flow synthesis of the advanced scaffolds 10
and 11 in hand, these materials were subjected to a flow
condensation reaction with a library of selected anilines
through an Omnifit cartridge packed with anhydrous sodium
sulphate to afford hemiaminal ethers 12a-l and 13a-l (Scheme
3; Table 1). In most instances the flow condensation reaction
afforded product in high yield and without extensive work up,
when compared to the batch synthesis which required column
chromatography. Generally, the installation of a wide range of
substituted anilines proceeded smoothly with isolated yields
ranging from modest (13a; 38%) to excellent (12e; 87%).
Scheme 4.
anhydrous Na2SO4, 30 °C, 19 h.
Reagents and conditions. (i) CH3(CH2)5NH2, 1:4 v/v EtOAc/Et2O,
With two 3,4-dihydro-2H-benzo[b][1,4]oxazine libraries
(
12a-l and 13a-l), and the parent analogues 10 and 11, in hand
we examined these compounds for their ability to inhibit the
growth of eleven cancer and one normal cell line (see Table 2
for cell line details). Compounds were initially screened at a
single 25 ꢀM concentration (ESI†), and those analogues that
displayed growth inhibition >90% for any specific cell line were
subject to a full dose evaluation to determine GI50 values.26
From the initial cytotoxicity screening, neither the parent
hemiaminals 10 and 11, nor the amide based library 13a
displayed any noteworthy cytotoxicity (ESI†). Of the remaining
analogues only 12b 12c 12g 12j and 12l proceeded to full
-1
,
,
,
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dose response evaluation and these data are presented in
Table 2.
BE2-C h
MIA i
SMA j
2.5±0.74
4.1±0.06
5.0±0.40
>50
4.3±0.40
8.4±0.37
9.1±0.76
1.8±0.13
3.2±0.03
3.4±0.27
0.35±0.05
0.91±0.05
0.77±0.03
2.2±0.74
>50
13±5.9
MCF10A k
6.8±0.56
c
>50
15±1.9
4.8±0.80
g
Table 1. Isolated yields and diversity of substituted anilines used in the
preparation of 3,4-dihydro-2H-benzo[b][1,4]oxazines 12a
-
l
and 13a
-
l.
a
b
d
e
f
h
colon; glioblastoma; breast; lung; skin; prostate; neuroblastoma;
glioblastoma; pancreas; murine glioblastoma; normal breast; ND = not
determined
i
j
k
l
Of the five analogues that proceeded to full dose response
evaluation, analysis of the data presented in Table 2 highlights
effectively very low levels of activity against the U87 cell line
Yield
Yield
(%)
94
Compound
5
R1
R2
Compound R1
(%)
with GI50 values form 32 (12b) to ≥ 50
ꢀM (12c, g, j, l),
EtO OH
EtO
44
6
EtNH
EtNH
suggesting that this scaffold, regardless of the substituents has
very limited effect on the growth of this glioblastoma cell line.
Examining each analogue in turn it was apparent that 12b
displays good levels of broad spectrum growth inhibition with
12a
12b
82
73
13a
38
81
EtO
EtO
EtO
EtO
13b
13c
13d
13e
EtNH
EtNH
EtNH
EtNH
the 3-bromo moiety, with GI50 values ≤10
lines examined with the exception of U87 and Du145.
Repositioning of the bromine moiety from 3- (12b) to 4- (12c
resulted in a significant drop in observed cytotoxicity with all
cell lines returning GI50 values > 50 M, except SJ-G2 (4.8 ± 1.0
M), A2780 (3.8 ± 0.51 M) and SMA (13 ± 5.9 M) cells,
ꢀM against all cell
)
12c
12d
12e
72
80
87
80
55
64
ꢀ
ꢀ
ꢀ
ꢀ
suggesting a key role for this moiety. Introduction of a –OCH3
moiety (Br replacement) resulted in moderate levels of broad
spectrum activity with GI50 values ranging from 3.8 ± 0.12 ꢀM
(A2780) to 20 ± 0.67 M (HT29). Both 12j and 12l were
ꢀ
significantly more potent than the other analogues noted thus
12f
EtO
65
13f
EtNH
85
far, but with the same lack of activity against the U87 cell line.
Analogue 12j displayed growth inhibition from 1.7 ± 0.07
(A2780) to 9.1 ± 0.55 M (Du145). The activity of 12l was
most notable with GI50 values ranging from 0.34 ± 0.04
(A2780) to 6.7 ± 0.88 M (Du145). Indeed 12l displayed sub-
micromolar potency across the A2780, BEC-2 (0.35 ± 0.05 M),
MIA (0.91 ± 0.05 M) and SMA (0.77 ± 0.03 M) cell lines.
M
12g
12h
EtO
EtO
51
60
13g
13h
EtNH
EtNH
73
69
ꢀ
ꢀ
M
ꢀ
ꢀ
ꢀ
ꢀ
Screening of these analogues against the normal breast cell
line, MCF10A, revealed a similar level of toxicity suggesting
that differentiation in toxicity between cancer cells and normal
cells did not occur with these analogues. While in cell
measures of toxicity is a poor model of animal or human
toxicity, it does provide a note of caution in the development
of these analogues as potential cytotoxic agents.
12i
EtO
72
13i
EtNH
41
12j
EtO
EtO
70
67
13j
EtNH
EtNH
73
47
12k
13k
While the amide analogues 13a-l were inactive, this most
probably results from the different cellular hydrolysis rates
between amide and esters, with the esterase action more
facile than that of the corresponding amidase.27
Notwithstanding this, these data suggest that the amide linked
scaffold may offer future potential as a scaffold for use in the
development of small molecules for other biological targets
where cytotoxicity is not desired.
12l
EtO
64
13l
EtNH
80
Table 2. Dose response growth inhibition of a panel of cancer cell lines by
analogues 12b, 12c, 12g, 12j and 12l. Values given represent the compound
dose required to elicit 50% of cell growth inhibition relative to an untreated
control (GI50 values; ꢀM).
Compound
12b
12c
12g
12j
12l
Cell Line
HT29 a
U87 b
SJ-G2 b
MCF-7 c
A2780 d
H460 e
A431 f
10±0.23
32±3.00
6.4±0.24
7.6±0.82
2.3±0.39
4.6±0.74
5.4±0.60
13±1.8
>50
20±0.67
>50
7.8±0.85
>50
6.1±3.0
48 ± 3
Conclusions
>50
A simple sequence of flow reactions has allowed rapid
4.8±1.0
>50
13±0.88
18 ± 1.8
3.8±0.12
9.1±0.33
11±1.3
33±8.3
4.9±0.72
5.5 ± 1.3
1.7±0.07
3.7±0.20
4.2±0.17
9.1±0.55
2.3±0.70
ND l
access
to
two
libraries
of
3,4-dihydro-2H-
) in modest to
benzo[b][1,4]oxazines analogues (12a
-l
and 13a-l
3.8±0.51
>50
0.34±0.04
1.3±0.26
1.7±0.16
6.7±0.88
excellent yields. We were not able to uses these protocols to
access the corresponding 2-N-aliphatic analogues.
>50
Du145 g
>50
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Screening of 10
11 cancer and one normal cell line revealed that the parent room temperature, the reaction was diluted with Et2O (100
hemiaminals 10 and 11 and the amide linked library 13a were mL) and, then, washed with saturated NaHCO3 (1 × 50 mL). The
, 11 and 12a-l and 13a-l against a panel of permitted to stir at this temperature for 16 h. After cooling to
-l
essenꢀally devoid of toxicity (ESI†). This posiꢀons both the separated organic layer was dried (MgSO4), filtered and then
synthesis and the scaffolds as potentially interesting as rapidly concentrated to give a dark yellow solid (7.05 g, 63%).
modified scaffolds are highly sought after in medicinal
Flow Synthesis
chemistry studies. The ester based library, 12a-l, showed
higher levels of toxicity consistent with the esterase cleavage
of the free carboxylate on entry to the cells. Of the analogues
that proceeded to GI50 determination, 12j and 12l were the
most potent across all the cell lines examined. All the active
analogues displayed high levels of cytotoxicity against the
ovarian cell line, A2780, suggesting that the analogues
developed herein may be valuable lead analogues for the
development of A2780 ovarian carcinoma specific cytotoxic
A solution of 4-hydroxy-3-nitrobenzoate (4, 1.02 g, 5.10 mm9l)
and concentrated H2SO4 (1.04 g) in ethanol (15 mL) was
pumped and recirculated through Vapourtec easy-
a
MedChem, fitted with 2 × 10 mL PFA coils at 140 °C, at 0.5
mL.min-1 and 8 bar of backpressure. After 2 h, the resulting
reaction liquor was concentrated under reduced pressure to
afford a bright yellow solid. The solid was washed with water,
filtered through cellulose paper and air dried to afford a
yellowish-pink crystalline solid (0.90 g, 69%). m.p. 66.9–68.0°C,
%); Rf 0.2 (2:98 v/v MeOH/CH2Cl2); 1H NMR (600 MHz, CDCl3) δ
10.88 (s, 1H), 8.82 (d, J = 2.1 Hz, 1H), 8.25 (dd, J = 8.8, 2.1 Hz,
1H), 7.22 (d, J = 8.8 Hz, 1H), 4.40 (q, J = 7.1 Hz, 2H), 1.41 (t, J =
7.1 Hz, 3H); 13C NMR (151 MHz, CDCl3) δ 164.3, 158.1, 138.0
133.2, 127.3, 123.1, 120.2, 61.7, 14.3; Mass spectrum (ESI,
+ve) m/z 212 [(M+H)+, (ESI, –ve) m/z 210 [(M–H)–, 100%];
HRMS (ESI+) calcd. for C9H10NO5 (M+H)+ 212.0553, found
212.0554; IR νmax (cm-1) 3252, 3092, 2987, 1717, 1627, 1583,
1539, 1423, 1363, 1330, 1283, 1261, 1151, 1020, 925, 860,
758, 687, 633, 574, 533, 501, 428.
agents with GI50 values from 3.8 – 0.34 ꢀM.
Experimental Section
Materials and methods
All reagents were purchased from Sigma Aldrich and were
used without purification, with the exception of furfural, which
was distilled from glass prior to use. Solvents were bulk, and
distilled from glass prior to use.
1H and 13C NMR spectra were recorded on a Bruker
Advance™ AMX 400 at 400.13 and 100.62 MHz, respectively
and Advance™ AMX 600 at 600.21 and 150.92, respectively.
Chemical shifts (δ) are reported in parts per million (ppm)
measured relative to the internal standards. Coupling
constants (J) are expressed in Hertz (Hz). Mass spectra were
recorded on a Shimadzu LCMS 2010 EV and Agilent 6100 series
N-Ethyl-4-hydroxy-3-nitrobenzamide (6)
Two solution streams, one comprising 4-hydroxy-3-benzoate
(4, 0.92 mg, 5.0 mmol), COMU (2.6 g, 6.05 mmol) and iPr2NEt
(1.76 ml, 10.1 mmol) in CH3CN (25 mL); and the second
solution ethylamine (0.28 ml, 10.1 mmol of a 70% aqueous
solution) in DMF (15 mL) were pumped through a Vapourtec
R4 fitted with one 10 mL PFA coil, maintained at 60 °C at 1
mL.min-1 (residence time: 10 min) with a backpressure of 5
bar. The resulting product stream was concentrated in vacuo
and adsorbed on SiO2 and, then, subjected to column
chromatography (SiO2) with a gradual elution of 0:1 to 1:0 v/v
EtOAc/n-Hexane. Concentration of the relevant fractions (Rf:
0.3 – 1:1 v/v EtOAc/n-Hexane) afforded a yellow solid (340 mg,
32 %). m.p. = 122–124°C; 1H NMR (400 MHz, CDCl3) δ 10.75 (s,
1H), 8.51 (d, J = 2.2 Hz, 1H), 8.06 (dd, J = 8.8, 2.2 Hz, 1H), 7.22
(d, J = 8.8 Hz, 1H), 6.17 (s, 1H), 3.55 – 3.48 (m, 2H), 1.28 (t, J =
7.3 Hz, 3H); 13C NMR (101 MHz, CDCl3) δ 164.7, 157.2, 136.3,
133.1, 127.3, 123.8, 120.6, 35.4, 15.0; Mass spectrum (ESI,
+ve) m/z 211 [(M+H)+, 100%]; HRMS (ESI) calcd. for C9H11N2O4
(M+H) 211.0713, found 211.0714; IR νmax (cm-1) 3301, 3279,
2996, 1626, 1615, 1520, 1418, 1250, 1240, 1162, 1076, 756,
658, 618, 582, 487, 425.
single quadrupole LCMS using
a mobile phase of 1:1
acetonitrile:H2O with 0.1 % formic acid. Gas chromatography-
mass spectrometry (GC-MS) was performed on a Shimadzu GC-
MS QF2010 EI/NCI System equipped with a ZB-5MS capillary
column of 5% phenyl-arylene stationary phase.
Melting points (M.P.) were recorded on a Büchi Melting
Point M-565. IR spectra were recorded on a PerkinElmer
Spectrum
Two™
FTIR
Spectrometer.
Thin
layer
chromatography (TLC) was performed on Merck 60 F254 pre-
coated aluminium plates with a thickness of 0.2 mm. Column
chromatography was performed under ‘flash’ conditions on
Merck silica gel 60 (230-400 mesh).
Hydrogenations were performed using
a ThalesNano
H-Cube ProTM (H-Cube®) continuous-flow hydrogenation
reactor. All reactions were passed through the H-Cube® reactor
once, unless otherwise specified. Flow reactions were carried
out using Vapourtec RS-400 fitted with V3 pumps and
Vapourtec easy-MedChem fitted with V3 pumps.
Ethyl 4-hydroxy-3-nitrobenzoate (5)
Batch synthesis
Ethyl 3-amino-4-hydroxybenzoate (7)
A solution of ethyl 4-hydroxy-3-nitrobenzoate (
5, 130 mg,
0.62 mmol) in CH3CN (12 mL) was passed through
a
A magnetically stirred solution of 4-hydroxy-3-nitrobenzoate
ThalesNano H-Cube Pro® using a 30 mm 10% Pd/C CatCart®
catalyst at 3 mL.min-1 (residence time: 4 min) at 50 °C and 50
bar of pressure. The resulting product stream was
concentrated under reduced pressure to afforded a creamy
(4, 10 g, 54.6 mmol) in absolute ethanol (100 mL), maintained
at 18 °C, was charged with concentrated sulphuric acid (2
drops). The ensuing mixture was heated to reflux and
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ARTICLE
N-Ethyl-2-hydroxy-3-oxo-3,4-dihydro-2H-benzo[b][1,4, ]oxazine-6-
white solid (110 mg, 98 %). m.p. 65.5–67.8 °C, Rf 0.15 (1:9 v/v
CH3OH/CH2Cl2), 1H NMR (600 MHz, CDCl3) δ 7.46 (d, J = 1.8 Hz,
1H), 7.43 (dd, J = 8.2, 1.8 Hz, 1H), 6.75 (d, J = 8.2 Hz, 1H), 4.32
(q, J = 7.1 Hz, 2H), 3.74 (broad s, 2H), 1.37 (t, J = 7.1 Hz, 3H);
carboxamide (11)
Three solution streams, one comprising 3-amino-N-ethyl-4-
hydroxybenzamide (80 mg, 0.44 mmol) in CH3CN (9 mL); the
second, NaHCO3 in H2O (0.5 M); and the third dichloroacetyl
chloride in dichloroethane (0.05 M) were pumped through a
Vapourtec easy-MedChem fitted with two 4 mL PFA coils,
maintained at 18 °C, and two 10 mL PFA coils, maintained at
100 °C at 1 mL.min-1 (residence time: 14 min) with a
backpressure of 5 bar. The resulting biphasic product stream
was separated; the aqueous washed with EtOAc (2 × 30 mL),
dried (MgSO4), filtered and then concentrated in vacuo to give
13C NMR (151 MHz, CDCl3)
δ 167.2, 149.0, 134.4, 422.7, 122.0,
117.5, 114.5, 60.8, 14.4; Mass spectrum (ESI, +ve) m/z 265
[(M+iPrOH+Na+H)+, 100%], 182 [(M+H)+, 100%], (ESI, –ve) m/z
180 [(M–H)-, 100%]; HRMS (ESI) calcd. for C9H10NO3 (M–H)–
181.1885, found 181.0499; IR νmax (cm-1) 3386, 3100, 2985,
1687, 1602, 1520, 1365, 1302, 1285, 1202, 1151, 1094, 1022,
893, 764, 637, 453.
3-Amino-N-ethyl-4-hydroxybenzamide (8)
a pale yellow solid (54 mg, 52%); m.p. 222.9–239.1 °C; Rf 0.25
1
, 51 mg, (1:9 v/v CH3OH/CH2Cl2), H NMR (600 MHz, d6-DMSO):
A solution of N-ethyl-4-hydroxy-3-nitrobenzamide (
6
δ
10.91
0.3 mmol) in EtOAc (12 mL) was passed through a ThalesNano (s, 1H), 8.37 (t, J = 5.3 Hz, 1H), 8.05 (d, J = 6.5 Hz, 1H), 7.44 –
H-Cube Pro® using a 70 mm 10% Pd-C CatCart® catalyst at 7.43 (m, 2H), 7.05 (d, J = 8.2 Hz, 1H), 5.52 (d, J = 6.5 Hz, 1H),
3 mL.min-1 (residence time: 4 min) at 50 °C and 50 bar of 3.32 – 3.23 (m, 2H), 1.10 (t, J = 7.2 Hz, 3H); 13C NMR (151 MHz,
pressure. The resulting product stream was concentrated CD3OD) δ 168.2, 163.0, 151.3, 125.7, 125.3, 124.5, 121.0,
under reduced pressure to afford light brown solid (41 mg, 95 114.3, 66.6, 34.4, 13.6; Mass spectrum (ESI, +ve) m/z 235.1
%). m.p. 183–185 °C, Rf 0.1 (1:1 v/v EtOAc/n-henxane), 1H NMR [(M–H)–, 65%), (ESI, +ve) m/z 237 [(M+H)+, 30%); HRMS (ESI)
(400 MHz, CD3OD) δ 7.19 (d, J = 2.2 Hz, 1H), 7.08 (dd, J = 8.2, calcd. for C22H25N4O8 (2M+H)+ 473.1667, found 473.1667; IR
2.2 Hz, 1H), 6.71 (d, J = 8.2 Hz, 1H), 3.36 (q, J = 7.2 Hz, 2H), 1.19 νmax (cm-1) 3363, 3095, 1684, 1635, 1550, 1495, 1389, 1282,
(t, J = 7.2 Hz, 3H);
136.5, 127.3, 119.4, 115.9, 114.7, 35.7, 15.0
13C NMR (101 MHz, CD3OD) δ 170.6, 149.7, 17, 1087, 1001, 965, 890, 763, 716, 632, 535, 472, 445.
Mass spectrum
;
(ESI, +ve) 181.2 [(M), 100%]; HRMS (ESI); (M–H)– 180.0899; IR
General procedure for the synthesis of 2-anilo substituted
νmax (cm-1) 3398, 3328, 2878, 1576, 1509, 1403, 1384, 1285, benzoxazinones
1219, 1138, 870, 751, 686, 510, 451.
Batch Synthesis:
Ethyl 2-hydroxy-3-oxo-3,4-dihydro-2H-benzo[b][1,4]oxazine-6-
A magnetically stirred slurry of ethyl 2-hydroxy-3-oxo-3,4-
dihydro-2H-benzo[b][1,4]oxazine-6-carboxylate 11a or
carboxylate (10)
(
)
Three solution streams, one comprising ethyl 3-amino-4-
N-ethyl-2-hydroxy-3-oxo-3,4-dihydro-2H-benzo[b][1,4]oxazine-
6-carboxamide (11b) (1.0 mmol, 1 eq.) in 1:4 v/v EtOAc/Et2O (3
mL), was charged with the corresponding aniline (1.5 eq., 1.5
mmol) and anhydrous Na2SO4 (10.0 mmol, 10 eq.). The ensuing
slurry was stirred at 30 °C for 19 h. After cooling to room
temperature, the mixture was adsorbed onto SiO2 and then
hydroxybenzoate (7, 68 mg, 0.04 mmol) in CH3CN (7.5 mL); the
second, NaHCO3 in H2O (0.5 M); and the third dichloroacetyl
chloride in dichloroethane (0.055 M) w ere pumped through a
Vapourtec easy-MedChem fitted with two 4 mL PFA coils,
maintained at 18 °C, followed by two 10 mL PFA coils,
maintained at 100 °C at 1 mL.min-1 (residence time: 14 min)
with a backpressure of 8 bar. The resulting biphasic product
stream was diluted with H2O (1 × 50 mL) and extracted with
EtOAc (4 × 10 mL). The combined organic phases were washed
subjected to flash chromatography (silica, 0:1
ꢀ 2:98 v/v
MeOH/CH2Cl2 gradient elution) and concentration of the
relevant fractions afforded the titled product.
with brine (1 × 50 mL), dried (MgSO4), filtered and then Flow Synthesis:
concentrated in vacuo to give a black solid This material was
.
recrystallised with CH2Cl2 to give a light pink crystalline solid
Two solutions streams, one comprising of ethyl 2-hydroxy-3-
oxo-3,4-dihydro-2H-benzo[b][1,4]oxazine-6-carboxylate 11a
or N-ethyl-2-hydroxy-3-oxo-3,4-dihydro-2H-
(
)
(30 mg, 44%), m.p. 175.4–177.7 °C, Rf 0.23 (1:19 v/v
1
MeOH/CH2Cl2), H NMR (600 MHz, d6-DMSO):
δ 10.96 (s, 1H),
benzo[b][1,4]oxazine-6-carboxamide (11b, 1.0 mmol, 1 eq.) in
EtOAc (200 μL); and the second stream of aniline (1.01 mmol,
1 eq.) in EtOAc (200 μL), were pumped through a Vapourtec
easy-MedChem fitted with one 10 mL PFA coil, maintained 100
°C, and an Omnifit® column containing anhydrous Na2SO4,
maintained at 100 °C, at 1mL.min-1 with a back pressure of 4
bar. The product stream was recirculated for 19 h, before it
was concentrated under reduced pressure to afford the title
product.
8.16 (d, J = 6.6 Hz, 1H), 7.58 (dd, J = 8.3, 2.0 Hz, 1H), 7.57 (d, J =
2.0 Hz, 1H), 7.12 (d, J = 8.3 Hz, 1H), 5.56 (d, J = 6.6 Hz, 1H), 4.29
(d, J = 7.1 Hz, 2H), 1.31 (t, J = 7.1 Hz, 3H); 13C NMR (151 MHz,
d6-DMSO)
δ 165.6, 162.6, 145.3, 127.3, 125.1, 124.6, 118.0,
116.8, 91.0, 61.1, 14.7; Mass spectrum (ESI, –ve) m/z 236 [(M–
H)-, 100%]; calcd. for C11H12NO5 (M+H)+ 238.0710 found
238.0710; IR νmax (cm-1) 3283, 2990, 2878, 1712, 1679, 1615,
1485, 1403, 1290, 1213, 1136, 1075, 1018, 969, 898, 764, 716,
606, 540, 449.
Library 1 – Ethyl ester analogues
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Organic & Biomolecular Chemistry
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DOI: 10.1039/C6OB01153E
ARTICLE
Journal Name
Ethyl 3-oxo-2-(phenylamino)-3,4-dihydro-2H-
a white solid (48.3 mg, 72%); m.p. 225.5–230.9 °C; Rf 0.38 –
1
1:19 v/v MeOH/CH2Cl2; H NMR (600 MHz, d6-acetone) δ 9.99
benzo[b][1,4]oxazine-6-carboxylate (12a)
(s, 1H), 7.71 (d, J = 1.9 Hz, 1H), 7.67 (dd, J = 8.4, 1.9 Hz, 1H),
7.37 – 7.35 (m, 2H), 7.08 (d, J = 8.4 Hz, 1H), 6.97 – 6.95 (m, 2H),
6.70 (d, J = 8.2 Hz, 1H), 5.94 – 5.93 (m, 1H), 4.35 – 4.30 (m, 2H),
1.35 (t, J = 7.0 Hz, 3H); 13C NMR (151 MHz, d6-acetone) δ 165.1,
161.3, 146.1, 144.3, 131.9 (2 overlapping signals), 127.7, 125.2,
117.7, 117.0, 116.0 (2 overlapping signals), 110.8, 81.23
(rotamer A), 81.16 (rotamer B), 60.6, 13.7; Mass spectrum (ESI,
–ve) m/z 389 [(M–H)–, 95], 391 [(M+2-H)-, 100%]; HRMS (ESI)
Employing the procedure described above, ethyl 2-hydroxy-3-
oxo-3,4-dihydro-2H-benzo[b][1,4]oxazine-6-carboxylate
(10,
40.0 mg, 0.17 mmol), aniline (19.0 μL, 0.20 mmol) and
anhydrous Na2SO4 (241 mg, 1.70 mmol), were reacted in 1:4
v/v EtOAc/Et2O (10 mL). The titled product 12a was isolated as
a white solid (44.0 mg, 82%); Rf: 0.4 (1:19 v/v CH3OH/CH2Cl2),
m.p. 197.6–200.2 °C; 1H NMR (600 MHz, d6-acetone)
δ 9.98
(bs, 1H), 7.71 (d, J = 2.0 Hz, 1H), 7.67 (dd, J = 8.4, 2.0 Hz, 1H),
7.22 (dd, J = 8.4, 7.5 Hz, 2H), 7.07 (d, J = 8.4 Hz, 1H), 6.98 (d, J =
7.5 Hz, 2H), 6.81 (t, J = 7.5 Hz, 1H), 6.51 (d, J = 8.4 Hz, 1H), 5.94
– 5.93 (m, 1H), 4.35 – 4.31 (q, J = 7.1 Hz, 2H), 1.35 (t, J = 7.1 Hz,
3H); 13C NMR (151 MHz, d6-acetone) δ 165.2, 161.5, 146.3,
144.9, 129.1 (2 overlapping signals), 127.8, 125.2 (rotamer A),
125.2 (rotamer B), 119.4, 117.7, 116.9, 114.0, 114.0, 81.6
(rotamer A), 81.5 (rotamer B), 78.3, 60.5, 13.7; Mass spectrum
(ESI, –ve) m/z 311 [(M–H)–, 100%]; HRMS (ESI) Compound 12a
Compound 12c hydrolysed to hemiacetal 7 calcd. for C11H12NO5
(M+H)+ 238.0710, found 238.0711; IR νmax (cm-1) 3276, 1703,
1679, 1592, 1379, 1284, 1208, 1101, 1012, 921, 812, 765, 710,
658, 539, 504, 434.
3-(6-(Ethoxycarbonyl)-3-oxo-3,4-dihydro-2H benzo[b][1,4]oxazin -
2-ylamino)benzoic acid (12d)
Employing the procedure described above, ethyl 2-hydroxy-3-
hydrolysed to hemiacetal
7
calcd. for C11H12NO5 (M+H)+
oxo-3,4-dihydro-2H-benzo[b][1,4]oxazine-6-carboxylate
(10,
238.0710, found 238.0810; IR νmax (cm-1): 3310, 3191, 3101,
3045, 2995, 2885, 1717, 1477, 1603, 1526, 1494, 1449, 1400,
1289, 1208, 1127, 1098, 1015, 951, 916, 764, 746, 690, 507,
473.
40 mg, 0.17 mmol), 3-aminobenzoic acid (28 mg, 0.20 mmol)
and anhydrous Na2SO4 (241 mg, 1.70 mmol), were reacted in
1:4 v/v EtOAc/Et2O (10 mL). The titled product 12d was
isolated as a white solid (49.0 mg, 80%); m.p. 163.3–201.6; Rf
1
*Rotamer exists through the free rotation of the N-phenyl
group.
0.15 (1:19 v/v CH3OH/CH2Cl2); H NMR (600 MHz, d6-DMSO) δ
12.78 (s, 1H), 11.15 (s, 1H), 7.61 (d, J = 2.0 Hz, 1H), 7.57 – 7.54
(m, 2H), 7.45 (s, 1H), 7.35 (d, J = 7.7 Hz, 1H), 7.30 (t, J = 7.7 Hz,
1H), 7.14 – 7.12 (m, 1H), 7.03 (d, J = 8.5 Hz, 1H), 6.06 (d, J = 8.5
Hz, 1H), 4.32 – 4.28 (m, 2H), 1.31 (t, J = 6 Hz, 3H); 13C NMR
(151 MHz, d6-DMSO) δ 168.0, 165.6, 161.9, 146.2, 145.5,
132.2, 129.7, 128.0, 125.3, 124.5, 120.2, 118.3, 118.1, 117.1,
114.8, 81.0, 61.1, 14.7; Mass Spectrum (ESI, –ve) 355 [(M-H)-,
100%]; (ESI, +ve) 357 [(M+H)+, 100%], 379 [(M+Na), 20%];
Ethyl 2-(3-bromophenylamino)-3-oxo-3,4-dihydro-2H-
benzo[b][1,4]oxazine-6-carboxylate (12b)
Employing the procedure described above, ethyl 2-hydroxy-3-
oxo-3,4-dihydro-2H-benzo[b][1,4]oxazine-6-carboxylate
(10,
40 mg, 0.17 mmol), 3-bromoaniline (21 μL, 0.18 mmol) and
anhydrous Na2SO4 (241 mg, 1.70 mmol), were reacted in 1:4
v/v EtOAc/Et2O (10 mL). The titled product 12b was isolated as
a white solid (49 mg, 73%); m.p. 182.2–188.9 °C; Rf 0.45 (1:19
HRMS (ESI) Compound 12d hydrolysed to hemiacetal
7 calcd.
for C11H12NO5 (M+H)+ 238.0710, found 238.0711; IR νmax (cm-1)
3267, 2979, 1705, 1688, 1611, 1597, 1439, 1292, 1209, 1132,
1119, 960, 938, 901, 768, 754, 680, 647, 536, 492, 446.
1
v/v CH3OH/CH2Cl2); H NMR (600 MHz, d6-acetone) δ 10.08 (s,
1H), 7.72 (d, J = 1.9 Hz, 1H), 7.69 (dd, J = 8.4, 1.9 Hz, 1H), 7.20
(t, J = 2.0 Hz, 1H), 7.18 (t, J = 8.0 Hz, 1H), 7.11 (d, J = 8.4 Hz,
1H), 7.00 – 6.99 (m, 2H), 6.79 (d, J = 8.2 Hz, 1H), 6.01 – 5.99 (m,
1H), 4.34 (q, J = 7.0 Hz, 2H), 1.36 (t, J = 7.0 Hz, 3H); 13C NMR
(151 MHz, d6-acetone) δ 165.1, 161.3, 146.7, 146.1, 130.9,
127.7, 125.3, 125.2, 122.6, 122.0, 117.7, 117.0, 116.6, 113.0,
81.0, 60.6, 13.7; Mass spectrum (ESI, +ve) m/z 391 [(M+H)+,
100%], 393 [(M+2+H)+, 100%], (ESI, –ve) m/z 389 [(M–H)–,
100%], 391 [(M+2–H)–, 100%]; HRMS (ESI) Compound 12a
4-(6-(Ethoxycarbonyl)-3-oxo-3,4-dihydro-2H-benzo[b][1,4]oxazin-
2-ylamino)-3-methoxybenzoic acid (12e)
Employing the procedure described above, ethyl 2-hydroxy-3-
oxo-3,4-dihydro-2H-benzo[b][1,4]oxazine-6-carboxylate
(11a,
40 mg, 0.17 mmol), 4-aminobenzoic acid (28 mg, 0.20 mmol)
and anhydrous Na2SO4 (241 mg, 1.70 mmol), were reacted in
1:4 v/v EtOAc/Et2O (10 mL). The titled product 12e was
isolated as a white solid (53 mg, 87%); m.p. 238.1–246.7 °C; Rf
hydrolysed to hemiacetal
7
calcd. for C11H12NO5 (M+H)+
238.0710, found 238.0709; IR νmax (cm-1) 3191, 2989, 2390,
1714, 1678, 1674, 1597, 1479, 1368, 1306, 1254, 1215, 1170,
1123, 1070, 1018, 954, 846, 765, 680, 492, 467, 433.
1
0.14 (1:19 v/v MeOH/CH2Cl2); H NMR (600 MHz, d6-DMSO) δ
12.33 (s, 1H), 11.19 (s, 1H), 7.89 (d, J = 8.8 Hz, 1H), 7.77 (d, J =
8.7 Hz, 2H), 7.62 (d, J = 2.0 Hz, 1H), 7.56 (dd, J = 8.4, 2.0 Hz,
1H), 7.04 (d, J = 8.4 Hz, 1H), 6.93 (d, J = 8.8 Hz, 2H), 6.11 (d, J =
8.8 Hz, 1H), 4.30 (q, J = 7.1 Hz, 2H), 1.31 (t, J = 7.1 Hz, 3H); 13C
NMR (151 MHz, d6-DMSO) δ 167.7, 165.6, 161.8, 149.5, 146.1,
131.5 (2 overlapping signals), 127.9, 125.3, 124.7, 121.1 118.1,
117.2, 113.4 (2 overlapping signals), 80.3, 61.1, 14.7; Mass
spectrum (ESI, –ve) m/z 355 [(M–H)–, 100%]; HRMS (ESI)
Ethyl 2-(4-bromophenylamino)-3-oxo-3,4-dihydro-2H-benzo[b]
[1,4]oxazine-6-carboxylate (12c)
Employing the procedure described above, ethyl 2-hydroxy-3-
oxo-3,4-dihydro-2H-benzo[b][1,4]oxazine-6-carboxylate
(11a,
40 mg, 0.17 mmol), 4-bromoaniline (32 mg, 0.18 mmol) and
anhydrous Na2SO4 (241 mg, 1.70 mmol), were reacted in 1:4
v/v EtOAc/Et2O (10 mL). The titled product 12c was isolated as
Compound 12e hydrolysed to hemiacetal 7 calcd. for C11H12NO5
(M+H)+ 238.0710, found 238.0710; IR νmax (cm-1) 3267, 2978,
6 | J. Name., 2012, 00, 1-3
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DOI: 10.1039/C6OB01153E
ARTICLE
1688, 1611, 1596, 1529, 1484, 1426, 1377, 1310, 1292, 1209, v/v EtOAc/Et2O (10 mL). The titled product 12h was isolated as
1132, 1090, 959, 768, 753, 680, 535, 445.
a white solid (35 mg, 60%); m.p. 182.2–184.0 °C; Rf 0.3 (1:19
v/v MeOH/CH2Cl2); 1H NMR (600 MHz, CDCl3 + d4-MeOD
(drop)) δ 8.83 (s, 1H), 7.76 (dd, J = 8.4, 1.8 Hz, 1H), 7.62 (d, J =
1.8 Hz, 1H), 7.11 (d, J = 8.4 Hz, 1H), 6.87 – 6.83 (m, 4H), 5.62 (d,
J = 6.8 Hz, 1H), 5.16 (d, J = 6.8 Hz, 1H), 4.38 (q, J = 7.1 Hz, 2H),
3.77 (s, 3H), 1.40 (t, J = 7.1 Hz, 3H); 13C NMR (151 MHz, d6-
Acetone) δ 165.1, 161.6, 153.7, 146.3, 138.5, 127.9, 125.1,
125.0, 117.7, 116.9, 115.4 (2 overlapping signals), 114.6 (2
overlapping signals), 82.6, 60.5, 54.8, 13.7; Mass spectrum
(ESI, –ve) 341 [(M–H)-, 100%]; (ESI, +ve) 343 [(M+H)+, 100%];
Ethyl 2-(2-methoxyphenylamino)-3-oxo-3,4-dihydro-2H-
benzo[b][1,4]oxazine-6-carboxylate (12f)
Employing the procedure described above, ethyl 2-hydroxy-3-
oxo-3,4-dihydro-2H-benzo[b][1,4]oxazine-6-carboxylate
(11a,
40 mg, 0.17 mmol), 2-anisidine (21 μL, 0.18 mmol) and
anhydrous Na2SO4 (241 mg, 1.70 mmol), were reacted in 1:4
v/v EtOAc/Et2O (10 mL) were reacted in EtOAc (10 mL). The
titled product 12f was isolated as a white solid (38 mg, 65%);
1
HRMS (ESI) Compound 12h hydrolysed to hemiacetal
7 calcd.
m.p. 168.2–176.8 °C; Rf 0.33 (1:19 v/v CH3OH/CH2Cl2); H NMR
for C11H12NO5 (M+H)+ 238.0710 found, 238.0710; IR νmax 3309,
2989, 1710, 1674, 1601, 1512, 1490, 1408, 1366, 1303, 1252,
1229, 1201, 1033, 956, 927, 820, 764, 650, 556, 472, 432.
(400 MHz, d6-Acetone) δ 10.0 (s, 1H), 7.74 (d, J = 1.9 Hz, 1H),
7.70 (dd, J = 8.4, 1.9 Hz, 1H), 7.13 (d, J = 8.4 Hz, 1H), 7.07 (d, J =
7.9 Hz, 1H), 6.93 – 6.90 (m, 2H), 6.82 (t, J = 7.9 Hz, 1H), 6.12 (d,
J = 6.8 Hz, 1H), 5.83 (d, J = 6.8 Hz, 1H), 4.33 (q, J = 7.1 Hz, 2H),
3.83 (s, 3H), 1.36 (t, J = 7.1 Hz, 4H); 13C NMR (151 MHz, CDCl3)
δ 165.9, 162.4, 147.3, 146.5, 133.7, 126.4, 125.3, 121.2, 120.1,
Ethyl 3-oxo-2-(o-tolylamino)-3,4-dihydro-2H-benzo[b][1,4]oxazine-
6-carboxylate (12i)
117.8, 117.4, 112.0, 110.1, 81.9, 65.9, 61.3, 55.5, 14.3; Mass Employing the procedure described above, ethyl 2-hydroxy-3-
spectrum (ESI, +ve) m/z 343 [(M+H)+, 100%], (ESI, –ve) m/z 341 oxo-3,4-dihydro-2H-benzo[b][1,4]oxazine-6-carboxylate
10
[(M-H)-, 100%]; HRMS (ESI) Compound 12f hydrolysed to 40 mg, 0.17 mmol), 2-toluidine (19 mg, 0.18 mmol) and
(
,
hemiacetal
7
calcd. for C11H12NO5 (M+H)+ 238.0710, found anhydrous Na2SO4 (241 mg, 1.70 mmol), were reacted in 1:4
238.0709; IR νmax (cm-1) 3412, 3305, 2978, 1723, 1695, 1600, v/v EtOAc/Et2O (10 mL). The titled product 12i was isolated as
1527, 1483, 1329, 1288, 1212, 1182, 1103, 1022, 917, 760, a white solid (40 mg, 72%); m.p. 199.8–200.7 °C; Rf 0.4 (1:19
1
732, 632, 462, 475, 435.
v/v CH3OH/CH2Cl2); H NMR (600 MHz, d6-acetone) δ 10.03 (s,
1H), 7.74 (d, J = 2.0 Hz, 1H), 7.71 (dd, J = 8.3, 2.0 Hz, 1H), 7.14
(t, J = 7.5 Hz, 1H), 7.12 – 7.10 (m, 3H), 6.80 (td, J = 7.5, 0.8 Hz,
1H), 5.90 (d, J = 7.4 Hz, 1H), 5.85 (d, J = 7.4 Hz, 1H), 4.35 (q, J =
7.0 Hz, 2H), 2.19 (s, 3H), 1.37 (t, J = 7.1 Hz, 3H); 13C NMR (151
MHz, CDCl3) δ 166.0, 162.9, 147.5, 143.7 (rotamer A), 143.7
(rotamer B), 131.2, 128.7, 127.9, 126.2, 126.15 (rotamer A),
126.07 (rotamer B), 124.43 (rotamer A), 124.40 (rotamer B),
120.6, 118.4, 118.0, 113.6, 83.02 (rotamer A), 82.98 (rotamer
B), 61.4, 17.5, 14.6; Mass spectrum (ESI, +ve) m/z 327 [(M+H)+,
100%], (ESI, –ve) 325 [(M–H)–, 100%]; HRMS Compound 12i
Ethyl 2-(3-methoxyphenylamino)-3-oxo-3,4-dihydro-2H-benzo
[b][1,4]oxazine-6-carboxylate (12g)
Employing the procedure described above, ethyl 2-hydroxy-3-
oxo-3,4-dihydro-2H-benzo[b][1,4]oxazine-6-carboxylate (10,
40 mg, 0.17 mmol), 3-anisidine (21 μL, 0.18 mmol) and
anhydrous Na2SO4 (241 mg, 1.70 mmol), were reacted in 1:4
v/v EtOAc/Et2O (10 mL). The titled product 12g was isolated as
a white solid (30 mg, 51 %); m.p. 169.9–180.0 °C; Rf 0.2 (1:19
1
v/v CH3OH/CH2Cl2); H NMR (600 MHz, CDCl3+CD3OD (drop)) δ
cleaved to hemiacetal
7
calcd. for C11H12NO5 (M+H)+ 238.0710,
8.91 (s, 1H), 7.76 (dd, J = 8.4, 1.9 Hz, 1H), 7.64 (d, J = 1.9 Hz,
1H), 7.17 (t, J = 8.4 Hz, 1H), 7.12 (d, J = 8.4 Hz, 1H), 6.51 – 6.47
(m, 3H), 5.67 (d, J = 7.0 Hz, 1H), 5.44 (d, J = 7.0 Hz, 1H), 4.38 (q,
J = 7.1 Hz, 2H), 3.80 (s, 3H), 1.40 (t, J = 7.1 Hz, 3H); 13C NMR
(151 MHz, CDCl3+CD3OD (drop)) δ 165.8, 162.3, 160.8, 146.6,
145.2, 130.3, 126.5, 126.4, 125.5, 117.8, 117.5, 107.1, 105.6,
100.6, 82.0, 61.3, 55.2, 14.3; Mass spectrum (ESI, –ve) m/v 340
[(M-H)-, 100%]; HRMS (ESI) Compound 12g cleaved to
found 238.0710; IR νmax (cm-1) 3331, 3273, 2978, 1721, 1674,
1606, 1489, 1290, 1216, 1154, 1098, 1023, 950, 913, 840, 760,
743, 711, 539, 448.
*Rotamer exists through the free rotation of the N-tolyl group.
Ethyl 3-oxo-2-(m-tolylamino)-3,4-dihydro-2H-
benzo[b][1,4]oxazine-6-carboxylate (12j)
hemiacetal
238.0709; IR νmax (cm-1) 3333, 3261, 2984, 1704, 1699, 1679, oxo-3,4-dihydro-2H-benzo[b][1,4]oxazine-6-carboxylate
1601, 1486, 1369, 1293, 1200, 1165, 1118, 917, 823, 763, 686, 40 mg, 0.17 mmol), 3-toluidine (19 μL, 0.18 mmol) and
652, 540, 491, 439. anhydrous Na2SO4 (241 mg, 1.70 mmol), were reacted in 1:4
*Rotamer exists through the free rotation of the N- v/v EtOAc/Et2O (10 mL). The titled product 12j was isolated as
7
calcd. for C11H12NO5 (M+H)+ 238.0710, found Employing the procedure described above, ethyl 2-hydroxy-3-
(
11a
,
methoxyphenyl group.
a white solid (39 mg, 70%); m.p. 205.4–207.7 °C; Rf 0.32 (1:19
1
v/v CH3OH/CH2Cl2); H NMR (600 MHz, CDCl3) δ 8.98 (s, 1H),
Ethyl 2-(4-methoxyphenylamino)-3-oxo-3,4-dihydro-2H-
benzo[b][1,4]oxazine-6-carboxylate (12h)
7.76 (dd, J = 8.4, 1.9 Hz, 1H), 7.64 (d, J = 1.9 Hz, 1H), 7.15 –
7.11 (m, 2H), 6.74 – 6.70 (m, 3H), 5.68 (d, J = 7.0 Hz, 1H), 5.36
(d, J = 7.0 Hz, 1H), 4.38 (q, J = 7.1 Hz, 2H), 2.32 (s, 3H), 1.40 (t, J
= 7.1 Hz, 3H); 13C NMR (151 MHz, CDCl3) δ 165.8, 162.4, 146.7,
143.8, 139.4, 129.3, 126.5, 126.4, 125.5, 121.4, 117.8, 117.53
(rotamer A), 117.47 (rotamer B), 115.1, 111.4, 82.2, 61.3, 21.6,
Employing the procedure described above, ethyl 2-hydroxy-3-
oxo-3,4-dihydro-2H-benzo[b][1,4]oxazine-6-carboxylate
(10,
40 mg, 0.17 mmol), 4-anisidine (23 mg, 0.18 mmol) and
anhydrous Na2SO4 (241 mg, 1.70 mmol), were reacted in 1:4
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Journal Name
14.3; Mass spectrum (ESI, +ve) m/z 327 [(M+H)+, 100%], (ESI, – Library 2 – Ethyl amide analogues
ve) m/z 325 [(M-H)-, 100%]; HRMS (ESI) Compound 12j cleaved
6-(1-Iminopropyl)-2-(phenylamino)-2H-benzo[b][1,4]oxazin-3(4H)-
to hemiacetal
7
calcd. for C11H12NO5 (M+H)+ 238.0710, found
one (13a)
238.0709 IR νmax (cm-1) 3304, 3270, 3191, 2986, 1678, 1609,
1488, 1387, 1295, 1217, 1177, 1122, 1026, 954, 922, 761, 690,
645, 537, 447, 437.
Employing
N-ethyl-2-hydroxy-3-oxo-3,4-dihydro-2H-benzo[b][1,4]oxazine-
6-carboxamide (11, 35 mg, 0.15 mmol), aniline (15 L, 0.16
the
procedure
described
above,
ꢀ
*Rotamer exists through the free rotation of the N-tolyl group.
mmol) and anhydrous Na2SO4 (220 mg, 1.5 mmol) were
reacted in 1:4 v/v EtOAc/Et2O (10 mL). The titled product 13a
was isolated as a white solid (18 mg, 38%); Rf 0.25 (1:19 v/v
CH3OH/CH2Cl2); m.p. 197.6–200.2 °C; 1H NMR (600 MHz, d6-
acetone) δ 9.98 (s, 1H), 7.68 (s, 1H), 7.64 (s, 1H), 7.49 (d, J = 8.3
Hz, 1H), 7.21 (t, J = 7.3 Hz, 2H), 7.00 – 6.97 (m, 3H), 6.81 (t, J =
7.3 Hz, 1H), 6.47 (d, J = 8.0 Hz, 1H), 5.88 (d, J = 8.0 Hz, 1H),
3.43–3.38 (m, 2H), 1.18 (t, J = 7.2 Hz, 3H); 13C NMR (151 MHz,
d6-acetone) δ 165.3, 161.7, 145.0, 144.6, 130.1, 129.1 (2
overlapping peaks), 127.7, 122.0, 119.3, 117.2, 115.7, 114.0 (2
overlapping peaks), 81.4, 34.2, 14.3; Mass spectrum (ESI, +ve)
m/z 312 [(M+H)+, 100%], (ESI, –ve) m/z 310 [(M–H)–, 100%];
HRMS (ESI) calcd. for C18H18N3O5 (M+formic acid–H)– 356.1252,
found 356.1256; IR νmax (cm-1) 3586, 3326, 2971, 1674, 1634,
1594, 1544, 1489, 1398, 1300, 1212, 1139, 1120, 1077, 1005,
927, 880, 850, 754, 688, 646, 509, 468, 448.
Ethyl 3-oxo-2-(p-tolylamino)-3,4-dihydro-2H-benzo[b][1,4]oxazine-
6-carboxylate (12k)
Employing the procedure described above, ethyl 2-hydroxy-3-
oxo-3,4-dihydro-2H-benzo[b][1,4]oxazine-6-carboxylate
(11a,
40 mg, 0.17 mmol), 4-toluidine (19 μL, 0.18 mmol) and
anhydrous Na2SO4 (241 mg, 1.70 mmol), were reacted in 1:4
v/v EtOAc/Et2O (10 mL). The titled product 12k was isolated as
a white solid (37 mg, 67%); m.p. 182.2–184.4 °C, Rf 0.4 (1:19
1
v/v CH3OH/CH2Cl2); H NMR (600 MHz, d6-acetone) δ 9.97 (s,
1H), 7.71 (d, J = 1.9 Hz, 1H), 7.68 (dd, J = 8.4, 1.9 Hz, 1H), 7.07
(d, J = 8.4 Hz, 1H), 7.04 (d, J = 8.1 Hz, 2H), 6.89 (d, J = 8.4 Hz,
2H), 6.37 (d, J = 8.4 Hz, 1H), 5.92 – 5.90 (m, 1H), 4.36 – 4.32 (m,
2H), 2.24 (s, 3H), 1.36 (t, J = 7.1 Hz, 3H); 13C NMR (151 MHz, d6-
acetone) δ 165.2, 161.6, 146.3, 142.5, 129.6 (2 overlapping
signals), 128.3, 127.9, 125.2 (rotamer A), 125.0 (rotamer B),
117.7, 116.9, 114.1 (2 overlapping signals), 81.95 (rotamer A),
81.89 (rotamer B), 60.5, 29.7, 19.6, 13.7; Mass spectrum (ESI, -
+ve) m/z 327 [(M+H)+, 100%], (ESI, –ve) m/z 325 [(M–H)–,
2-((3-Bromophenyl)amino)-6-(1-iminopropyl)-2H-
benzo[b][1,4]oxazin-3(4H)-one (13b)
Employing
the
procedure
described
above,
100%]; HRMS (ESI) Compound 12k cleaved to hemiacetal
7
N-ethyl-2-hydroxy-3-oxo-3,4-dihydro-2H-benzo[b][1,4]oxazine-
6-carboxamide (11, 35 mg, 0.15 mmol), 3-bromoaniline (21 μL,
0.18 mmol) and anhydrous Na2SO4 (210 mg, 1.50 mmol), were
reacted in 1:4 v/v EtOAc/Et2O (10 mL). The titled product 13b
was isolated as a white solid (48 mg, 81%); m.p. 162.9–170 °C;
Rf 0.4 (1:19 v/v CH3OH/CH2Cl2); 1H NMR (400 MHz, d6-acetone)
δ 9.98 (s, 1H), 7.67 (s, 1H), 7.62 (s, 1H), 7.50 (dd, J = 8.3, 1.8 Hz,
1H), 7.19 (t, J = 1.8 Hz, 1H), 7.16 (d, J = 8.0 Hz, 1H), 7.01 (d, J =
8.0 Hz, 1H), 6.99 – 6.96 (m, 2H), 6.72 (d, J = 8.0 Hz, 1H), 5.93 –
5.91 (m, 1H), 3.43 – 3.36 (m, 2H), 1.17 (t, J = 7.2 Hz, 3H); 13C
NMR (101 MHz, d6-DMSO) 167.7, 162.7, 146.6, 144.7, 130.3,
129.2, 127.1, 122.5, 121.8, 117.3, 116.5, 115.4, 112.5, 80.8,
34.5, 13.5; Mass spectrum (ESI, +ve) m/z 390 [(M+H)+, 100%],
392 [(M+2+H)+, 100%], (ESI, -ve) m/z 388 [(M-H)-, 100%], 390
[(M+2-H)-, 100]; HRMS (ESI) Material decomposed; IR νmax (cm-
1) 3252, 3125, 2979, 1687, 1583, 1564, 1380, 1332, 1308,
1215, 1147, 1118, 1088, 951, 923, 853, 763, 701, 763, 701,
680, 574, 470.
calcd. for C11H12NO5 (M+H)+ 238.0710, found 238.0710 IR νmax
(cm-1) 3280, 2433, 1700, 1675, 1602, 1527, 1506, 1489, 1367,
1329, 1287, 1251, 1209, 1122, 1018, 899, 807, 765, 509, 468,
439.
*Rotamer exists through the free rotation of the N-tolyl group.
Ethyl 2-(2-hydroxyphenylamino)-3-oxo-3,4-dihydro-2H-
benzo[b][1,4]oxazine-6-carboxylate (12l)
Employing the procedure described above, ethyl 2-hydroxy-3-
oxo-3,4-dihydro-2H-benzo[b][1,4]oxazine-6-carboxylate
(11a,
40 mg, 0.17 mmol), 2-aminophenol (22 mg, 0.18 mmol) and
anhydrous Na2SO4 (241 mg, 1.70 mmol), were reacted in 1:4
v/v EtOAc/Et2O (10 mL). The titled product 12l was isolated as
a white solid (36 mg, 64%); m.p. 166.2–176.3; Rf 0.3 (5:95 v/v
CH3OH/CH2Cl2); 1H NMR (600 MHz, d6-acetone) δ 10.03 (s, 1H),
8.56 (s, 1H), 7.74 (d, J = 1.9 Hz, 1H), 7.71 (dd, J = 8.4, 1.9 Hz,
1H), 7.13 (d, J = 8.4 Hz, 1H), 7.04 (dd, J = 7.8, 1.0 Hz, 1H), 6.83 –
6.81 (m, 2H), 6.69 (td, J = 7.7, 1.3 Hz, 1H), 6.01 (d, J = 6.8 Hz,
1H), 5.84 (d, J = 6.8 Hz, 1H), 4.33 (q, J = 7.1 Hz, 2H), 1.36 (t, J =
7.1 Hz, 3H); 13C NMR (151 MHz, d6-acetone) δ 165.1, 162.1,
146.7, 144.6, 133.4, 127.9, 125.3, 125.2, 120.3, 119.6, 117.5,
117.1, 114.3, 112.8, 81.9, 60.6, 13.7; Mass spectrum (ESI, +ve)
m/z 329 [(M+H)+, 100], 370 [(M+ACN+H), 5]+, 392
[(M+ACN+Na)+, 1]; m/z (ESI, –ve) 327 [(M–H)–, 100], 363
[(M+Cl)–, 5], 441[(M+TFA)–, 3], 655 [(2M–H)–, 10]; HRMS (ESI)
2-((4-Bromophenyl)amino)-6-(1-iminopropyl)-2H-
benzo[b][1,4]oxazin-3(4H)-one (13c)
Employing
the
procedure
described
above,
N-ethyl-2-hydroxy-3-oxo-3,4-dihydro-2H-benzo[b][1,4]oxazine-
6-carboxamide (11, 35 mg, 0.15 mmol), 4-bromoaniline (32
mg, 0.18 mmol) and anhydrous Na2SO4 (210 mg, 1.50 mmol),
were reacted in 1:4 v/v EtOAc/Et2O (10 mL). The titled product
13c was isolated as a white solid (48 mg, 81%); m.p. 205.7–
Compound 12l cleaved to hemiacetal
7 calcd. for C11H12NO5
(M+H)+ 238.0710, found 238.0709 IR νmax 3257, 2981, 1700,
1674, 1600, 1525, 1490, 1456, 1287, 1223, 1200, 1123, 1105,
1020, 975, 952, 901, 872, 823, 765, 732, 633, 572, 477, 432.
1
218.8 °C; Rf 0.58 (1:19 v/v CH3OH/CH2Cl2); H NMR (400 MHz,
d6-acetone) δ 9.98 (s, 1H), 7.67 (s, 1H), 7.62 (d, J = 2.0 Hz, 1H),
7.49 (dd, J = 8.4, 2.0 Hz, 1H), 7.37 – 7.34 (m, 2H), 7.00 (d, J =
8 | J. Name., 2012, 00, 1-3
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DOI: 10.1039/C6OB01153E
ARTICLE
N-Ethyl-2-((2-methoxyphenyl)amino)-3-oxo-3,4-dihydro-2H-
benzo[b][1,4]oxazine-6-carboxamide (13f)
Employing the procedure
N-ethyl-2-hydroxy-3-oxo-3,4-dihydro-2H-benzo[b][1,4]oxazine-
6-carboxamide (11, 40 mg, 0.17 mmol), 2-anisidine (26 ꢀL,
8.4 Hz, 1H), 6.96 – 6.94 (m, 2H), 6.67 (d, J = 8.2 Hz, 1H), 5.88–
5.86 (m, 1H), 3.43 – 3.36 (m, 2H), 1.17 (t, J = 7.2 Hz, 3H); 13C
NMR (101 MHz, d6-acetone) δ 165.3, 161.5, 144.39 (rotamer
A), 144.35 (rotamer B), 131.8 (2 overlapping signals), 130.1,
127.6, 122.0, 117.2, 115.9 (2 overlapping signals), 115.7, 110.7,
81.0, 78.3, 34.2, 14.3; Mass spectrum (ESI, +ve) m/z 390
[(M+H)+, 100%], 392 [(M+2+H)+, 100%], (ESI, -ve) m/z 389 [(M-
H)-, 100%], 390 [(M+2-H)-, 100%]; HRMS (ESI) Material
decomposed; IR νmax (cm-1) 3320, 3056, 2974, 1679, 1616,
1579, 1563, 1489, 1386, 1408, 1294, 1212, 1143, 1110, 985,
923, 846, 815, 679, 525, 506, 469, 442.
described
above,
0.19 mmol) and anhydrous Na2SO4 (270 mg, 1.7 mmol) were
reacted in 1:4 v/v EtOAc/Et2O (10 mL). The titled product 13f
was isolated as a white solid (49 mg, 85%); m.p. 232.0–
1
244.5 °C; Rf 0.18 (1:19 v/v CH3OH/CH2Cl2); H NMR (600 MHz,
d6-acetone) δ 10.04 (s, 1H), 7.69 (s, 1H), 7.66 (d, J = 2.0 Hz, 1H),
7.53 (dd, J = 8.3, 2.0 Hz, 1H), 7.06 (d, J = 8.3 Hz, 2H), 6.92–6.89
(m, 2H), 6.81 (m, 1H), 6.10 (d, J = 6.6 Hz, 1H), 5.77 (d, J = 6.6
Hz, 1H), 3.84 (s, 3H), 3.43 – 3.39 (m, 2H), 1.18 (t, J = 7.2 Hz,
3H); 13C NMR (151 MHz, d6-acetone) δ 167.1, 164.0, 149.1,
146.8, 136.1, 132.1, 129.6, 124.0, 122.8, 121.2, 118.8, 117.6,
113.8, 112.0, 83.4, 56.8, 36.1, 16.1; Mass spectrum (ESI, +ve)
m/z 342 [(M+H)+, 10], 683 [(2M+H)+, 5], (ESI, -ve) 340 [(M-H)-,
100%], 454 [(M+TFA-H)-, 5], 681 [(2M-H)-, 10]; HRMS (ESI)
calcd. for C18H18N3O4 (M–H)– 340.1303, found 340.1302; IR νmax
(cm-1) 3409, 3305, 2972, 2873, 1710, 1634, 1616, 1599, 1526,
1493, 1390, 1336, 1225, 1151, 1033, 927, 853, 767, 742, 683,
647, 528.
3-((6-(Ethylcarbamoyl)-3-oxo-3,4-dihydro-2H-benzo[b][1,4]oxazin-
2-yl)amino)benzoic acid (13d)
Employing
the
procedure
described
above,
N-ethyl-2-hydroxy-3-oxo-3,4-dihydro-2H-benzo[b][1,4]oxazine-
6-carboxamide (11, 35 mg, 0.15 mmol), 3-aminobenzoic acid
(22 mg, 0.16 mmol), anhydrous Na2SO4 (210 mg, 1.48 mmol),
were reacted in 1:4 v/v EtOAc/Et2O (10 mL). The titled product
13d was isolated as a white solid (29 mg, 55%); m.p. 210.1–212
°C; Rf 0.2 (1:19 v/v CH3OH/CH2Cl2); 1H NMR (600 MHz, d6-
DMSO) δ 12.79 (s, 1H), 11.09 (s, 1H), 8.36 (t, J = 5.3 Hz, 1H),
7.50 – 7.49 (m, 2H), 7.44 – 7.33 (m, 2H), 7.32 (d, J = 7.8 Hz, 1H),
7.29 (t, J = 7.8 Hz, 1H), 7.12 (d, J = 6.9 Hz, 1H), 6.95 (d, J = 8.3
Hz, 1H), 5.97 (d, J = 8.3 Hz, 1H), 3.33–3.23 (m, 2H), 1.10 (t, J =
7.2 Hz, 3H); 13C NMR (151 MHz, d6-DMSO) δ 168.0, 165.6,
162.1, 145.7, 144.4, 132.1, 129.7 (rotamer A), 129.6 (rotamer
B), 127.8, 122.4, 120.1, 118.3, 117.4, 116.1, 114.8, 80.9, 34.5,
31.2, 15.3; Mass spectrum (ESI, –ve) m/z (ESI, -ve) 354 [(M-H)-,
100%], 390 [(M+Cl)-, 45], 709 [(2M-H)-, 40]; HRMS (ESI) calcd.
for C18H15N3NaO5 (M+Na–H)– 376.0915, found 376.2785; IR
νmax (cm-1) 3344, 3145, 2979, 1689, 1652, 1610, 1594, 1495,
1382, 1311, 1244, 1211, 1116, 964, 937, 810, 753, 446.
N-Ethyl-2-((3-methoxyphenyl)amino)-3-oxo-3,4-dihydro-2H-
benzo[b][1,4]oxazine-6-carboxamide (13g)
Employing
the
procedure
described
above,
N-ethyl-2-hydroxy-3-oxo-3,4-dihydro-2H-benzo[b][1,4]oxazine-
6-carboxamide (11, 35 mg, 0.15 mmol), 3-anisidine (20 μL, 0.17
mmol), anhydrous Na2SO4 (210 mg, 1.48 mmol), were reacted
in 1:4 v/v EtOAc/Et2O (10 mL). The titled product 13g was
isolated as a white solid (37 mg, 73%); m.p. 214.7–217.0 °C; Rf
1
0.46 (1:19 v/v CH3OH/CH2Cl2), H NMR (600 MHz, d6-acetone)
δ 9.97 (s, 1H), 7.68 (s, 1H), 7.64 (d, J = 2.0 Hz, 1H), 7.49 (dd, J =
8.3, 2.0 Hz, 1H), 7.10 (t, J = 8.3 Hz, 1H), 7.00 (d, J = 8.3 Hz, 1H),
6.56–6.55 (m, 2H), 6.48 (d, J = 8.3 Hz, 1H), 6.40–6.39 (m, 1H),
5.87 (d, J = 8.2 Hz, 1H), 3.75 (s, 3H), 3.42–3.39 (m, 2H), 1.18 (t,
J = 7.2 Hz, 3H); 13C NMR (151 MHz, d6-acetone) δ 165.4, 161.8,
160.9, 146.4, 144.6, 130.1, 129.9, 127.8, 121.9, 117.2, 115.7,
106.64 (rotamer A), 106.60 (rotamer B), 104.8, 100.03
(rotamer A), 100.00 (rotamer B), 81.4, (rotamer A) 81.3
(rotamter B), 54.4, 34.3, 14.3; Mass spectrum (ESI, +ve) m/z
342 [(M+H)+, 100], 383 [(M+2NA+H)+, 20], 683 [(2M+H)+, 50],
(ESI, ve) m/z 340 [(M-H)-, 100%], 386 [(M+formic acid-H)-, 5],
454 [(M+TFA-H)-, 5], 681 [(2M-H)-, 10]; HRMS (ESI) calcd. for
C18H18N3O4 (M–H)– 340.1303, found 340.1302; IR νmax (cm-1)
3299, 2973, 1687, 1683, 1605, 1558, 1382, 1310, 1203, 1177,
1043, 924, 813, 766, 687, 514, 495, 474, 436.
4-((6-(Ethylcarbamoyl)-3-oxo-3,4-dihydro-2H-benzo[b][1,4]oxazin-
2-yl)amino)benzoic acid (13e)
Employing
the
procedure
described
above,
N-ethyl-2-hydroxy-3-oxo-3,4-dihydro-2H-benzo[b][1,4]oxazine-
6-carboxamide (11, 35 mg, 0.15 mmol), 4-aminobenzoic acid
(22 mg, 0.16 mmol), anhydrous Na2SO4 (210 mg, 1.48 mmol)
were reacted in 1:4 v/v EtOAc/Et2O (10 mL). The titled product
13e was isolated as a white solid (34 mg, 64%); m.p. 209.6–
1
214.7 °C; Rf 0.18 (1:19 v/v CH3OH/CH2Cl2); H NMR (600 MHz,
d6-DMSO) δ 12.31 (s, 1H), 11.14 (s, 1H), 8.37 (t, J = 5.2 Hz, 1H),
7.85 (d, J = 8.6 Hz, 1H), 7.76 (d, J = 8.6 Hz, 2H), 7.49 (s, 1H),
7.44 (d, J = 8.3 Hz, 1H), 6.97 (d, J = 8.3 Hz, 1H), 6.92 (d, J = 8.6
Hz, 2H), 6.03 (d, J = 8.6 Hz, 1H), 3.29 – 3.22 (m, 2H), 1.10 (t, J =
7.2 Hz, 3H); 13C NMR (151 MHz, d6-DMSO) δ 166.6, 164.5,
160.9, 148.6, 143.1, 130.4 (2 overlapping signals), 128.7, 126.6,
121.4, 119.9, 116.3, 115.0, 112.3 (2 overlapping signals), 79.1,
33.4, 14.2; Mass spectrum m/z 354 [(M–H)–, 100%]; HRMS
(ESI) calcd. for C18H15N3NaO5 (M+Na–H)– 376.0915, found
376.2785; IR νmax (cm-1) 3322, 3056, 2974, 2543, 1683, 1606,
1575, 1490, 1426, 1307, 1292, 1213, 1178, 1145, 1102, 931,
845, 530, 468.
*Rotamer exists through the free rotation of the N-
arylmethoxy group.
N-Ethyl-2-((4-methoxyphenyl)amino)-3-oxo-3,4-dihydro-2H-
benzo[b][1,4]oxazine-6-carboxamide (13h)
Employing
the
procedure
described
above,
N-ethyl-2-hydroxy-3-oxo-3,4-dihydro-2H-benzo[b][1,4]oxazine-
6-carboxamide (11, 35 mg, 0.14 mmol), 4-anisidine (20 mg,
0.17 mmol) and anhydrous Na2SO4 (210 mg, 1.48 mmol), were
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DOI: 10.1039/C6OB01153E
ARTICLE
Journal Name
reacted in 1:4 v/v EtOAc/Et2O (10 mL). The titled product 13h 3.39 (m, 2H), 2.26 (s, 3H), 1.18 (t, J = 7.2 Hz, 3H); 13C NMR (151
was isolated as a white solid (35 mg, 69%); m.p. 207.4– MHz, d6-acetone) δ 165.4, 161.8, 145.0, 144.6, 138.6, 130.0,
1
209.3 °C; Rf 0.55 (1:19 v/v CH3OH/CH2Cl2); H NMR (600 MHz, 129.0, 127.8, 121.9, 120.1, 117.2, 115.8, 114.7, 111.2, 81.5
d6-acetone) δ 9.90 (s, 1H), 7.65 (s, 1H), 7.61 (d, J = 2.0 Hz, 1H), (rotamer A), 81.5 (rotamer B), 34.4, 20.7, 14.3; Mass spectrum
7.49 (dd, J = 8.3, 2.0 Hz, 1H), 6.98 (d, J = 8.3 Hz, 1H), 6.93 (d, J = (ESI, +ve) m/z 326 [(M+H)+, 80%], 367 [(M+ACN+H)+, 100], 651
8.9 Hz, 2H), 6.82 (d, J = 8.9 Hz, 2H), 6.18 (d, J = 8.4 Hz, 1H), 5.79 [(2M+H)+, 50], (ESI, –ve) 324 [(M–H)–, 100%], 438 [(M+TFA–H)–,
(d, J = 8.4 Hz, 1H), 3.73 (s, 3H), 3.42 – 3.37 (m, 2H), 1.17 (t, J = 100]; HRMS (ESI) Compound 13k cleaved to hemiacetal 6 calcd.
7.2 Hz, 3H); 13C NMR (151 MHz, d6-acetone) δ 167.2, 163.7, for C11H13N2O4 (M+H)+ 237.0870, found 237.0870; IR νmax (cm-
155.4, 146.4, 140.5, 131.8, 129.6, 123.7, 119.0, 117.4, 117.1 (2 1) 3453, 3291, 3144, 2971, 1683, 1647, 1595, 1536, 1486,
overlapping signals), 116.3 (2 overlapping signals), 84.2, 56.7, 1383, 1317, 1280, 1218, 1177, 954, 919, 852, 813, 774, 755,
36.1, 16.1; Mass spectrum (ESI, +ve) m/z 342 [(M+H)+, 100], 689, 648, 572, 535, 453, 445.
383 [(M+2NA+H)+, 10], 683 [(2M+H)+, 50], (ESI, –ve) m/z 340
[(M-H)-, 100%], 386 [(M+formic acid-H)-, 5], 454 [(M+TFA-H)-,
N-Ethyl-3-oxo-2-(p-tolylamino)-3,4-dihydro-2H-
5], 681 [(2M-H)-, 10]; HRMS (ESI) calcd. for C18H18N3O4 (M–H)–
benzo[b][1,4]oxazine-6-carboxamide (13k)
340.1303, found 340.1302; IR νmax (cm-1) 3446, 3274, 3139,
Employing
the
procedure
described
above,
2971, 1684, 1644, 1599, 1504, 1393, 1307, 1280, 1238, 1211,
1030, 954, 927, 818, 760, 536, 471.
N-ethyl-2-hydroxy-3-oxo-3,4-dihydro-2H-benzo[b][1,4]oxazine-
6-carboxamide (11b, 35 mg, 0.15 mmol), 4-toluidine (18 mg,
0.17 mmol) and anhydrous Na2SO4 (210 mg, 1.48 mmol), were
reacted in 1:4 v/v EtOAc/Et2O (10 mL). The titled product 13k
N-Ethyl-3-oxo-2-(o-tolylamino)-3,4-dihydro-2H-
benzo[b][1,4]oxazine-6-carboxamide (13i)
was isolated as a white solid (23 mg, 47%); m.p. 221–224 °C; Rf
1
above, 0.46 (1:19 v/v CH3OH/CH2Cl2); H NMR (600 MHz, d6-acetone)
Employing
the
procedure
described
N-ethyl-2-hydroxy-3-oxo-3,4-dihydro-2H-benzo[b][1,4]oxazine- δ 9.93 (s, 1H), 7.67 (s, 1H), 7.62 (d, J = 2.0 Hz, 1H), 7.49 (dd, J =
6-carboxamide (11, 35 mg, 0.15 mmol), 2-toluidine (18 L, 0.19 8.4, 2.0 Hz, 1H), 7.04 (d, J = 8.2 Hz, 2H), 6.99 (d, J = 8.4 Hz, 1H),
mmol) and anhydrous Na2SO4 (210 mg, 1.48 mmol), were 6.89 (d, J = 8.2 Hz, 2H), 6.32 (d, J = 8.4 Hz, 1H), 5.84 (d, J = 8.4
reacted in 1:4 v/v EtOAc/Et2O (10 mL). The titled product 13i Hz, 1H), 3.43–3.39 (m, 2H), 2.24 (s, 3H), 1.19 (t, J = 7.2 Hz, 3H);
was isolated as a white solid (23 mg, 41%); m.p. 208–212 °C; Rf 13C NMR (151 MHz, d6-acetone) δ 165.4, 161.8, 144.6, 142.6,
1
0.6 (1:19 v/v MeOH/CH2Cl2); H NMR (600 MHz, d6-acetone) δ 130.0, 129.6 (2 overlapping signals), 128.2, 127.8, 121.9, 117.2,
10.02 (s, 1H), 7.70 (s, 1H), 7.65 (d, J = 1.8 Hz, 1H), 7.52 (dd, J = 115.7, 114.1 (2 overlapping signals), 81.8, 34.3, 19.6, 14.3;
8.3, 1.8 Hz, 1H), 7.15 (t, J = 7.4 Hz, 1H), 7.09–7.08 (m, 2H), 7.04 Mass spectrum (ESI,+ve) m/z 326 [(M+H)+, 10], (ESI, –ve) m/z
(d, J = 8.3 Hz, 1H), 6.78 (t, J = 7.4 Hz, 1H), 5.81 (s, 1H), 3.43– 324 [(M-H)-, 100%], 438 [(M+TFA-H)-, 10]; HRMS (ESI)
3.39 (m, 2H), 2.18 (s, 3H), 1.18 (t, J = 7.2 Hz, 3H) (Proton due to Compound 13k cleaved to hemiacetal
6 calcd. for C11H13N2O4
NH-Ar not observed); 13C NMR (151 MHz, d6-acetone) δ 166.3 (M+H)+ 237.0870, found 237.0870; IR νmax (cm-1) 3453, 3291,
(rotamer A), 166.2 (rotamer B), 163.1, 145.8, 143.8 (rotamer 3144, 2971, 1683, 1647, 1595, 1536, 1486, 1383, 1317, 1280,
A), 143.8 (rotamer B), 131.2, 131.0, 128.7, 127.9, 124.3, 123.0, 1218, 1177, 954, 919, 852, 813, 774, 755, 689, 648, 572, 535,
120.5, 117.9, 116.7, 113.6, 82.9 (rotamer A), 82.9 (rotamer B), 453, 445.
35.2 (rotamer A), 35.1 (rotamer B), 17.5, 15.2; Mass spectrum
(ESI, +ve) m/z 326 [(M+H)+, 100%], 367 [(M+CAN+H)+, 25], 651
N-ethyl-2-((2-hydroxyphenyl)amino)-3-methylene-3,4-dihydro-2H-
[(2M+H)+, 50], (ESI, –ve) 324 [(M–H)–, 100%], 438 [(M+TFA–H)–,
benzo[b][1,4]oxazine-6-carboxamide (13l)
20]; HRMS (ESI) calcd. for C18H18N3O4 (M–H)– 340.1303, found
Employing
the
procedure
described
above,
340.1302; IR νmax (cm-1) 3419, 3291, 2976, 2421, 1706, 1631,
1519, 1495, 1455, 1393, 1326, 1151, 1051, 926, 854, 750, 689,
466.
N-ethyl-2-hydroxy-3-oxo-3,4-dihydro-2H-benzo[b][1,4]oxazine-
6-carboxamide (11b, 35 mg, 0.15 mmol), 2-aminophenol (18
mg, 0.16 mmol) and anhydrous Na2SO4 (210 mg, 1.48 mmol),
were reacted in 1:4 v/v EtOAc/Et2O (10 mL). The titled product
13k was isolated as a white solid (39 mg, 80%); m.p. 181.4–
N-Ethyl-3-oxo-2-(m-tolylamino)-3,4-dihydro-2H-
benzo[b][1,4]oxazine-6-carboxamide (13j)
1
191.5 °C; Rf 0.21 (1:19 v/v CH3OH/CH2Cl2); H NMR (600 MHz,
Employing
N-ethyl-2-hydroxy-3-oxo-3,4-dihydro-2H-benzo[b][1,4]oxazine- = 2.0 Hz, 1H), 7.54 (dd, J = 8.4, 2.0 Hz, 1H), 7.06 (d, J = 8.3 Hz,
6-carboxamide (11, 35 mg, 0.15 mmol), m-toluidine (18 L, 1H), 7.03 (dd, J = 7.9, 1.2 Hz, 1H), 6.84 – 6.79 (m, 2H), 6.68 (td,
the
procedure
described
above, d6-acetone) δ 10.05 (s, 1H), 8.56 (s, 1H), 7.72 (s, 1H), 7.68 (d, J
ꢀ
0.19 mmol) and anhydrous Na2SO4 (210 mg, 1.48 mmol), were J = 7.9, 1.2 Hz, 1H), 5.99 (d, J = 6.7 Hz, 1H), 5.77 (d, J = 6.7 Hz,
reacted in 1:4 v/v EtOAc/Et2O (10 mL). The titled product 13j 1H), 3.44–3.39 (m, 2H), 1.18 (t, J = 7.2 Hz, 3H); 13C NMR (151
was isolated as a white solid (36 mg, 73%); m.p. 199.0– MHz, d6-acetone) δ 165.4, 162.3, 145.1, 144.6, 133.5, 130.2,
1
201.0 °C; Rf 0.46 (1:19 v/v CH3OH/CH2Cl2); H NMR (600 MHz, 127.8, 122.2, 120.3, 119.5, 117.0, 115.8, 114.3, 112.7, 81.8,
d6-acetone) δ 9.99 (s, 1H), 7.70 (s, 1H), 7.65 (d, J = 2.0 Hz, 1H), 34.4, 14.3; Mass spectrum (ESI, +ve) m/z 328 [(M+H)+, 5], (ESI,
7.49 (dd, J = 8.3, 2.0 Hz, 1H), 7.08 (t, J = 8.3 Hz, 1H), 6.99 (d, J = –ve) m/z 326 [(M–H)–, 100], 362 [(M+Cl) –, 33], 440 [(M+TFA–
8.3 Hz, 1H), 6.80 (s, 1H), 6.77 (d, J = 8.3 Hz, 1H), 6.63 (d, J = 8.3 H)–, 50], 653 [(2M–H), 45]; HRMS (ESI) material decomposed;
Hz, 1H), 6.39 (d, J = 8.3 Hz, 1H), 5.86 (d, J = 8.3 Hz, 1H), 3.43– IR νmax (cm-1) 3376, 3063, 2977, 2876, 1695, 1635, 1611, 1532,
10 | J. Name., 2012, 00, 1-3
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DOI: 10.1039/C6OB01153E
ARTICLE
27 M. P. Patricelli and B. F. Cravatt, Biochem., 1999, 38, 14125–
1489, 1457, 1386, 1315, 1207, 1121, 981, 909, 877, 797, 740,
634, 536, 481, 456, 446, 407.
14130.
Acknowledgements
Financial support was received from the Australian Research
Council (ARCDP 14101565), the Australian Cancer Research
Foundation and the Ramaciotti Foundation.
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