[1,5]-Hydride shift-cyclization versus C(sp2)-H functionalization in the knoevenagel-cyclization domino reactions of 1,4- And 1,5-Benzoxazepines

Article abstract of DOI:10.3390/molecules25061265

Domino cyclization reactions of N-aryl-1,4- and 1,5-benzoxazepine derivatives involving [1,5]-hydride shift or C(sp²)-H functionalization were investigated. Neuroprotective and acetylcholinesterase activities of the products were studied. Domino Knoevenagel-[1,5]-hydride shift-cyclization reaction of N-aryl-1,4-benzoxazepine derivatives with 1,3-dicarbonyl reagents having active methylene group afforded the 1,2,8,9-tetrahydro-7bH-quinolino [1,2-d][1,4]benzoxazepine scaffold with different substitution pattern. The C(sp³)-H activation step of the tertiary amine moiety occurred with complete regioselectivity and the 6-endo cyclization took place in a complete diastereoselective manner. In two cases, the enantiomers of the chiral condensed new 1,4-benzoxazepine systems were separated by chiral HPLC, HPLC-ECD spectra were recorded, and absolute configurations were determined by time-dependent density functional theory- electronic circular dichroism (TDDFT-ECD) calculations. In contrast, the analogue reaction of the regioisomeric N-aryl-1,5-benzoxazepine derivative did not follow the above mechanism but instead the Knoevenagel intermediate reacted in an S_EAr reaction [C(sp²)-H functionalization] resulting in a condensed acridane derivative. The AChE inhibitory assays of the new derivatives revealed that the acridane derivative had a 6.98 μM IC₅₀ value.

Full text of DOI:10.3390/molecules25061265

molecules
Article
2
[
1,5]-Hydride Shift-Cyclization versus C(sp )-H
Functionalization in the Knoevenagel-Cyclization
Domino Reactions of 1,4- and 1,5-Benzoxazepines
Dóra Szalóki Vargáné 1 , László Tóth
,2,†
1,3,†
, Balázs Buglyó , Attila Kiss-Szikszai
1
1
,
Attila Mándi 1 , Péter Mátyus , Sándor Antus *, Yinghan Chen , Dehai Li
4
1,
5
5
, Lingxue Tao ,
6
Haiyan Zhang 6 and Tibor Kurtán *
1,
1
Department of Organic Chemistry, University of Debrecen, Debrecen, P. O. Box 400, Debrecen 4002, Hungary;
szalokido@gmail.com (D.S.V.); tothlaszlochemist@gmail.com (L.T.); buglyo.balazs@science.unideb.hu (B.B.);
kiss.attila@science.unideb.hu (A.K.-S.); mandi.attila@science.unideb.hu (A.M.)
Doctoral School of Chemistry, University of Debrecen, Egyetem tér 1, Debrecen 4032, Hungary
Department of Organic Chemistry, Semmelweis University, Budapest 1094, Hungary
Institute of Digital Health Sciences, Faculty of Health and Public Services, Semmelweis University,
Ferenc tér 15, Budapest 1094, Hungary; peter.maty@gmail.com
Key Laboratory of Marine Drugs, Chinese Ministry of Education, School of Medicine and Pharmacy,
Ocean University of China, Qingdao 266003, China; qd_yinghan@163.com (Y.C.); dehaili@ouc.edu.cn (D.L.)
CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of
Sciences, 555 Zu Chong Zhi Road, Zhang Jiang Hi-Tech Park, Shanghai 201203, China;
lingxuetao@simm.ac.cn (L.T.); hzhang@simm.ac.cn (H.Z.)
2
3
4
5
6
*
†
Correspondence: kurtan.tibor@science.unideb.hu (T.K.); antus.sandor@science.unideb.hu (S.A.)
These authors contributed equally to this work.
ꢀ
ꢁꢂꢀꢃꢄꢅꢆꢇ
Academic Editor: György Keglevich
Received: 31 January 2020; Accepted: 7 March 2020; Published: 11 March 2020
ꢀ
ꢁꢂꢃꢄꢅꢆ
Abstract: Domino cyclization reactions of N-aryl-1,4- and 1,5-benzoxazepine derivatives involving
2
[
1,5]-hydride shift or C(sp )-H functionalization were investigated.
Neuroprotective and
acetylcholinesterase activities of the products were studied. Domino Knoevenagel-[1,5]-hydride
shift-cyclization reaction of N-aryl-1,4-benzoxazepine derivatives with 1,3-dicarbonyl reagents having
active methylene group afforded the 1,2,8,9-tetrahydro-7bH-quinolino [1,2-d][1,4]benzoxazepine
3
scaffold with different substitution pattern. The C(sp )-H activation step of the tertiary
amine moiety occurred with complete regioselectivity and the 6-endo cyclization took place in
a complete diastereoselective manner. In two cases, the enantiomers of the chiral condensed new
1,4-benzoxazepine systems were separated by chiral HPLC, HPLC-ECD spectra were recorded,
and absolute configurations were determined by time-dependent density functional theory- electronic
circular dichroism (TDDFT-ECD) calculations. In contrast, the analogue reaction of the regioisomeric
N-aryl-1,5-benzoxazepine derivative did not follow the above mechanism but instead the Knoevenagel
2
intermediate reacted in an S Ar reaction [C(sp )-H functionalization] resulting in a condensed acridane
E
derivative. The AChE inhibitory assays of the new derivatives revealed that the acridane derivative
had a 6.98 µM IC50 value.
Keywords:
domino Knoevenagel-[1,5]-hydride shift-cyclization;
1,4-benzoxazepine;
1
,5-benzoxazepine; TDDFT-ECD calculation; acetylcholinesterase inhibitory activity
1
. Introduction
C-H activation and functionalization of sp - and sp -hybridized carbons offer atom-economical
and step-efficient ways for the preparation of polyfunctionalized condensed heterocycles, which have
3
2
Molecules 2020, 25, 1265; doi:10.3390/molecules25061265
www.mdpi.com/journal/molecules

Molecules 2020, 25, 1265
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3
been intensely investigated recently [1–4]. The metal-free sp C-H functionalization via internal redox
processes or hydride transfer has attracted much attention due to its unique features. Instead of using
3
an external oxidant such as a high-valent transition metal [
by an internal [1,5]-hydride shift between a
5,6
], the sp C-H activation can be induced
π
electron-poor double bond as acceptor and a C-H
]. The resultant
bond adjacent to an oxygen or nitrogen as a hydride donor (A→B, Scheme 1a) [
7,8
zwitterionic intermediate B can undergo further cyclization producing condensed heterocycles C.
3
Scheme 1.
(
a
) General scheme for the C (sp )-H activation-cyclization sequence induced by
[1,5]-hydride shift of a tertiary amine or ether.
(b) [1,5]-Hydride shift-cyclization sequence of
N-aryl-1,4-benzoxazepines carried out in our present work.
In this work, the substrate (rac-
a Knoevenagel intermediate in the reaction of N-aryl-1,4-benzoxazepine derivatives rac-
active methylene reagents. The 5-H benzylic hydrogen of rac- , adjacent to a tertiary amine
nitrogen atom, acted as a hydride donor and a zwitterionic intermediate, formed in a [1,5]-hydride
2) able to undergo a [1,5]-hydride shift was obtained as
1
with
2
shift, cyclized affording the condensed tetracyclic 1,4-benzoxazepines rac-3 with complete regio-
and diastereoselectivity.
Condensed 1,4-benzoxazepines are common synthetic targets, since they are core structures in
numerous biologically active compounds possessing antihelmentic [ ], antitumor [10], anti-HIV [11],
9
transient receptor potential ankyrin 1 (TRPA1) agonist [12], Rab geranylgeranyl transferase (RabGGTase)
inhibitory [13], and antipsychotic [14] activities.
2
In reported examples, the C(sp )-H activation of 2-(N-arylamino)benzaldehyde derivatives
D
was
in an intramolecular cross-dehydrogenative coupling
CDC) reaction with PhI(OAc) or Sc(OTf) reagent (Scheme 2a) [15,16].
utilized to synthesize acridone derivatives
E
(
2
3

Molecules 2020, 25, 1265
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2
Scheme 2.
(a
) C(sp )-H activation and intramolecular cross-dehydrogenative coupling (CDC)
2
reaction for the preparation of acridones. (
b
) This work on the C(sp )-H functionalization of the
N-aryl-1,5-benzoxazepine 4; i: 1,3-dimethylbarbituric acid, MgSO , CHCl .
4
3
In this work, the N-aryl-1,5-benzoxazepine derivative
intermediate with 1,3-dimethylbarbituric acid in a Knoevenagel reaction, which cyclized with the
activated benzene ring to produce a condensed 9,10-dihydroacridine (acridane) derivative in an S Ar
4 was converted to the carbocationic
5
6
E
reaction. The different position of the nitrogen atom in the benzoxazepine scaffold induced a sequence
2
different from those depicted in Scheme 1b for the regioisomeric rac-
1
; a C(sp )-H functionalization took
place instead of the [1,5]-hydride shift-cyclization, which was observed for N-aryl-1,4-benzoxazepines.
The transformation of
reaction and a C(sp )-H functionalization during the S Ar reaction.
4
to
6
involves the activation of the carbonyl carbon during the Knoevenagel
2
E
Acridane derivatives have potent biological activity consisting of HIV reverse transcriptase
inhibitory [17] and neuroleptic activity [18], and activation of K2P potassium channels [19].
Moreover, acridanes have been utilized as host materials in OLEDs [20], chemiluminescent sensors in
immunoassays [21], as molecular motors [22] and NADH analogues in hydride transfer reactions [23].
Acetylchloninesterae (AChE) inhibitors are used as drugs for the symptomatic treatment of
Alzheimer’s disease (AD), and some of them such as galantamine contain condensed O,N-heterocyclic
skeleton [24]. AChE inhibitors prevent the action of cholinesterases (ChEs) and thus increase the levels
of acetylcholine in the brain and improve the cholinergic functions in AD patients [25]. The inhibition of
AChE is a potential therapeutic target for the treatment of AD but targeting ChEs alone is not sufficient
and thus exploration of multi-target molecules focusing also on other proposed molecular mechanisms
of AD such as β-amyloid cascade or oxidative stress is required. The multi-target approach was
pursued in recently reported works by exploring synthetic heterocyclic derivatives, which exhibited
both AChE and β-secretase inhibitory activity [26,27].
Oxidative stress, deriving from the accumulation of reactive oxygen species or an excess of
free radicals, is involved in the progression of several neurodegenerative diseases, including the
AD [28]. Recently, we reported the synthesis of condensed tetrahydro-1,4-benzoxazepines and an
isochroman-2H-chromene conjugate, which showed neuroprotective activities against hydrogen
peroxide (H O ) and
β
-amyloid25–35 (A
30]. In this work, acethylcholinesterase (AChE) inhibitory activity of new condensed
,4- and 1,5-benzoxazepines was tested as well as neuroprotective activities against hydrogen
peroxide (H O ), -amyloid25–35 fragment (A 25–35) and oxygen-glucose deprivation (OGD)-induced
β25–35)-induced cellular injuries in human neuroblastoma
2
2
SH-SY5Y cells [29
,
1
β
β
2
2

Molecules 2020, 25, 1265
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neurotoxicity in human neuroblastoma SH-SY5Y cells and a 1,5-benzoxazepine derivative was identified
to have AChE inhibitory activity with 6.98 × 10− mol/L IC50 value.
6
2
. Results and Discussion
2
.1. Knoevenagel-[1,5]-Hydride Shift-Cyclization Domino Reaction
The synthesis of 4-aryl-1,4-benzoxazepine derivatives rac-1a–c, the starting materials of the domino
Knoevenagel-[1,5]-hydride shift-cyclization reaction, was achieved in a simple three-step sequence
from the readily available chroman-4-one (rac-7a), 2-(1-naphthyl)-chroman-4-one (rac-7b) [31] and
2
-(2-naphthyl)-chroman-4-one (rac-7c) [31] (Scheme 3).
Scheme 3. i: (1) NaN /TFA or H SO (2) H O (rac-8a: 78%, rac-8b: 73%, rac-8c: 76%); ii:
3
2
4
2
LAH/THF, reflux (rac-9a: 80%, rac-9b: 91%, rac-9c: 94%); iii: 2-fluoro-5-nitrobenzaldehyde or
-chloro-5-nitrobenzaldehyde, K CO , toluene, reflux (rac-1a: 95%, rac-1b: 78%, rac-1c: 81%).
2
2
3
In the first step, a regioselective Schmidt reaction of rac-7a
affording the corresponding 3,4-dihydro-1,4-benzoxazepine-5(2H)-ones rac-8a
reduced with LiAlH under reflux to provide 2,3,4,5-tetrahidro-1,4-benzoxepines (rac-9a
–
c
was carried out with NaN3
(Scheme 3), which were
). In the
–
c
–
c
4
final step, the N-arylation of rac-9a was performed with 2-fluoro-5-nitrobenzaldehyde to result
in rac-1a in 95% yield. For the N-arylation of rac-9b and rac-9c, the more economical but less
reactive 2-chloro-5-nitrobenzaldehyde could be used instead. Furthermore, rac-1a–c were reacted
with 1,3-dimetylbarbituric and Meldrum’s acids, which initiated a Knoevenagel-[1,5]-hydride
shift-cyclization domino reaction (Scheme 4). The 1- and 2-naphthyl groups are known to adopt
different orientations relatively to the condensed heterocyclic skeleton and they also exhibit different
rotational energy barriers for their rotations, which may result in different bioactivities as demonstrated
recently for our synthetic pterocarpans having antiproliferative activity [32].

Molecules 2020, 25, 1265
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Scheme 4. i: 1,3-dimetylbarbituric acid, MgSO , CHCl , reflux, 6 h (10a: 95%, 10b: 36%, 10c: 52%); ii:
4
3
Meldrum’s acid, MgSO , CHCl , reflux, 6 h (11a: 87%, 11b: 50%, 11c: 98%); iii: malonitrile, MgSO4,
4
3
CHCl , reflux, 6 h (12a: 50%, 12b: 53% 12c: 61%).
3
The Knoevenagel intermediates 2A and 2B formed with 1,3-dimethylbarbituric acid and Meldrum’s
acid, respectively, underwent a regioselective [1,5]-hydride shift with the participation of the 5-H and
the resultant zwitterionic intermediate of type
-endo cyclization affording the rac-trans-10b
B
(Scheme 1a) reacted further in a diastereoselective
6
,c
, rac-trans-11b and rac-10a and rac-11a (Scheme 4).
,c
The formation of the other regio- or diastereomeric products was not observed. The complete
regioselectivity could be readily explained on the basis of the larger reactivity of the benzylic C-H
bond compared to that of the 3-C-H, while the trans-diastereoselectivity was favored by the attack
of the nucleophile from the face opposite to the orientation of the bulky naphthyl group linked at
C-2. The relative configuration of the C-2 and C-15a chirality centers could not be determined on
the basis of NOE correlations, since neither diastereomers would show NOE correlation between
2-H and 15a-H due to the large interatomic distance and orientation. In the trans-diastereomers,
the tetrahydrooxazepine ring is expected to adopt a boat conformation with trans-diaxial orientation
3
of the 2-Hax and 3-Hax protons giving rise to a large coupling J
constant (~11 Hz) similarly
-H,3-H
2
1
to the 2-phenyl analogues [29], which could be observed in the H NMR spectra of 10b
,
c
and 11b
,
c.
In contrast, the tetrahydrooxazepine ring of the cis diastereomer would adopt a twist boat conformation
3
with gauche arrangement of the 2-H and 3-Hs, which would produce small values for both J2-H,3-H
coupling constants.
With the malonitrile reagent, the reaction stopped at the stage of the Knoevenagel products 12a–c.
Stronger reaction conditions or microwave activation produced only partial cyclization or degradations.
Since the 1a starting material was achiral and its domino reaction introduced a new chirality center,
the formation of 10a and 11a offered the possibility to test enantioselective organocatalytic reactions
with non-covalent optically active organocatalysts. According to literature data, enantioselective
organocatalytic versions of [1,5]-hydride shift-cyclization sequences are limited to substrates, in which
the alkene double bond of the acceptor unit contains two alkoxycarbonyl substituents able to interact
with the organocatalyst in stereoselective manner [33–35]. In order to determine the absolute
configuration of the enantiomers of 10a and 11a and correlate it with the characteristic electronic
circular dichroism (ECD) transitions, the enantiomers of 10a and 11a were separated by chiral HPLC
using Chiralpack IC stationary phase and online HPLC-ECD spectra of the separated enantiomers were

Molecules 2020, 25, 1265
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recorded. HPLC-ECD measurements aided with time-dependent density functional theory electronic
circular dichroism (TDDFT-ECD) calculations represent an efficient method to study the enantiomers
in scalemic or racemic mixtures of natural [36,37] or synthetic derivatives [38,39]. The solution
TDDFT-ECD approach [40] was applied to determine the absolute configuration of the separated
enantiomers by comparing the experimental HPLC-ECD spectra with the computed ones. The Merck
Molecular Force Field (MMFF) conformational search of the arbitrarily chosen (S) enantiomers of 10a
and 11a resulted in 5 and 2 conformers in a 21 kJ/mol energy window, respectively. These conformers
were re-optimized at various density functional theory (DFT) levels (B3LYP/6-31G(d), B97D/TZVP
PCM/n-octanol and CAM-B3LYP/TZVP PCM/n-octanol) yielding only one major conformer at all the
applied levels (Figure 1).
Figure 1.
(a) Lowest-energy conformers of (S)-10a (99.1% population) and (b) (S)-11a (>99.9%
population). Level of DFT optimization: CAM-B3LYP/TZVP PCM/n-octanol.
ECD spectra were then calculated at the B3LYP/TZVP, BH&HLYP/TZVP, CAM-B3LYP/TZVP
and PBE0/TZVP levels with or without solvent model and all the applied combinations of levels
gave moderate to good agreement with the experimental HPLC-ECD spectra of the second-eluting
enantiomers allowing unambiguous determination of the absolute configuration of the second-eluting
enantiomer as (S)-10a and (S)-11a (Figure 2). The (S)-10a and (S)-11a enantiomers are correlated with
a broad negative Cotton effect (CE) above 350 nm in the HPLC-ECD spectra.
Figure 2.
(
a
) Experimental HPLC-ECD spectra of the second-eluting enantiomer of 10a (black line)
) Experimental
compared with the PBE0/TZVP PCM/n-octanol spectrum of (S)-10a (purple line). (
b
HPLC-ECD spectra of the second-eluting enantiomer of 11a (black line) compared with the B3LYP/TZVP
PCM/n-octanol spectrum of (S)-11a (red line). Level of DFT optimization: CAM-B3LYP/TZVP
PCM/n-octanol. Bars represent the computed rotational strength values.
Although enantioselective [1,4]-hydride shift-cyclization cascade reaction of Knoevenagel
intermediates prepared with dialkylmalonate were reported using optically active metal complexes [41
]

Molecules 2020, 25, 1265
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or organocatalysts [33
–
35], enantioselective transformations have not been published yet for
Knoevenagel intermediates prepared with 1,3-dimethylbarbituric acid and Meldrum’s acid.
Thus, we performed the 1a → 10a and 1a → 11a transformations in the presence of optically active
TADDOL- and chinchona-type non-covalent organocatalysts to test the possibility of enantioselective
reactions but unfortunately no notable enantiomeric excess (ee
and small conversion of the starting material (see Supporting Information for details).
≤
7.3%) could be achieved with slow
2
2
.2. Knoevenagel- C(sp )-H Functionalization Domino Reaction
The reaction condition of the Knoevenagel-[1,5]-hydride shift-cyclization cascade was also tested
on the analogous 1,5-benzoxazepine derivative
4, in which only a less activated C-4 methylene group
is available for the hydride shift. The N-aryl-1,5-benzoxazepine analogue
4
, starting material of the
domino reaction, was synthesized in four steps from chromanone (Scheme 5). The classical Beckmann
rearrangement of the (E)-ketoxime (13) afforded the 2,3-dihydro-1,5-benzoxazepin-4(5H)-one (14) [42],
which without isolation, could be readily reduced to 15 with DIBAL-H [43].
N-arylation of 15
with 2-fluoro-4-nitrobenzaldehyde could not be achieved in an S Ar reaction with potassium or
N
◦
cesium carbonate in dry DMF at 140 C due to the reduced nucleophilicity of the arylamine nitrogen.
Thus, Buchwald-Hartwig N-arylation of 15 was carried out with 2-bromobenzaldehyde, Pd(OAc)2,
a sterically hindered phosphine ligand and tetra-n-butylammonium bromide (TBAB) [44]. The reaction
was optimized by testing different phosphine ligands [SPhos (16), XPhos (17a), t-butyl XPhos (17b),
xantphos (18)] anhydrous solvents (1,4-dioxane, THF, toluene) and bases (Cs CO , K CO , KOtBu)
2
3
2
3
and the best condition [2-bromo-benzaldehyde, Pd(OAc) (7.5 mol%), SPhos (16, 10 mol%), Cs CO
2
2
3,
TBAB, anhydrous 1,4-dioxane, reflux] afforded the N-aryl derivative 4 with 87% yield.
Scheme 5. i: NH OH HCl, pyridine (94%); ii: DIBAL-H, anhydrous CH Cl (97% for two
·
2
2 2
steps); iii: 2-bromo-benzaldehyde, Pd(OAc) (7.5 mol%), S-Phos (16, 10 mol%), Cs CO TBAB,
2
2
3,
anhydrous 1,4-dioxane, reflux (87%).
The N-aryl derivative
domino Knoevenagel-[1,5]-hydride shift-cyclization sequence, the 19 precursor of the Knoevenagel
product formed a stabilized benzylic carbocation ( ), which initiated an S Ar reaction with the
activated benzene ring affording the condensed acridane derivative
Scheme 6). According to the NMR data, all the methylene protons of the oxazepine moiety
remained intact, while an aromatic C-H group was changed to a quaternary carbon. Two methine
4 was reacted with 1,3-dimethylbarbituric acid and instead of the expected
5
E
6
with 64% isolated yield
(
13
carbons appeared in the DEPT C NMR spectrum at 49.5 and 59.0 ppm corresponding to C-10 and
0
3
C-1 , respectively, the protons of wich had a 4.4 Hz J
0
coupling constant. The condensed
0-H,1 -H
1
2,3-dihydro-1H,8H-[1,4]oxazepino[2,3,4-de]acridine moiety has not been reported yet and direct

Molecules 2020, 25, 1265
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conversion of 2-(N-arylamino)benzaldehyde derivatives to acridanes under mild conditions represents
a new synthetic potential. The reaction of with malonitrile stopped at the stage of the Knoevenagel
product 20, which could not be converted to a cyclized product even under stronger reaction condition
higher temperature, microwave activation). The reaction with Meldrum’s acid produced a complex
4
(
reaction mixture, which has not been analyzed further.
O
N
O
O
CHO
N
N
O
H
N
N
i
O
N
O
HO
N
O
O
O
4
ii
5
19
S Ar
NC
E
3'
O
N 2'
9
CN
O
1'
1
0
6
4
N
N
N
O
5
O
0
12
O1
2
6
Scheme 6. i. 1,3-dimetylbarbituric acid, MgSO , CHCl , rt (64%); ii. malonitrile, MeNH2·HCl, CHCl3,
4
3
rt (96%).
2
.3. Bioactivity Studies
The neuroprotective and AChE inhibitory activities of the new compounds were tested to
compare neuroprotective activity with reported benzoxazepines and to identify candidates for
multi-target approach. Neuroprotective activities were tested against hydrogen peroxide (H O ),
2
2
β
-amyloid23-35 fragment (A
human neuroblastoma SH-SY5Y cells [45
compounds did not have remarkable neuroprotective activity at 10
that the lack of a C-2 aryl moiety or its extension to naphthyl groups results in the loss of activity [29].
β
23–35) and oxygen-glucose deprivation (OGD)-induced neurotoxicity in
46]. The preliminary screenings showed that the tested
M concentration, which suggested
,
µ
−5
Moderate AChE inhibitory activity was identified for the N-aryl-1,4-benzoxazepine 1a at 4.0
×
10
M
concentration (58.26% inhibition), while the acridane derivative
with 6.98 × 10− mol/L IC50 value.
6 showed AChE inhibitory activity
6
3
. Materials and Methods
Melting points were determined on a Kofler hot-stage apparatus (Wagner and Munz, Munich,
Germany) and are uncorrected. The reactions were monitored by thin layer chromatography (TLC).
TLC plates were visualized under a UV lamp and developed by phosphomolybdic acid solution.
1
13
The NMR spectra were recorded on Bruker-AMX 400 ( H: 400 MHz; C: 100 MHz, Bruker, Karlsruhe,
1
13
Germany; Billerica, MA, USA) and Bruker Aspect 3000 ( H: 360 MHz, C: 90 MHz, Bruker, Karlsruhe,
Germany; Billerica, MA, USA) spectrometers using TMS and the solvent peak as internal standard.
3
Chemical shifts were reported as
δ
in ppm and J
coupling constants in Hz. Chiral HPLC
H,H
separation of 10a and 11a were performed on a Jasco HPLC system with Chiralpak IC column (5 µm,
−
1
1
50 × 4.6 mm, hexan/propan-2-ol 1:1 eluent, 1 mLmin flow rate, Daicel Chemical Industries Ltd.,
Tokyo, Japan) and HPLC-ECD spectra were recorded in stopped-flow mode on a JASCO J-810 electronic
circular dichroism spectropolarimeter (JASCO Inc. Tokyo, Japan) equipped with a 10 mm HPLC flow
cell. ECD ellipticity (φ) values were not corrected for concentration. For an HPLC-ECD spectrum,

Molecules 2020, 25, 1265
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three consecutive scans were recorded and averaged with 2 nm bandwidth, 1 s response, and standard
sensitivity. The HPLC-ECD spectrum of the eluent recorded in the same way was used as background.
The concentration of the injected sample was set so that the HT value did not exceed 500 V in the HT
channel down to 230 nm. IR spectra were recorded on a JASCO FT/IR-4100 spectrometer (JASCO Inc.
−1
Tokyo, Japan) and absorption bands are presented in cm . Electrospay Quadrupole Time-of-Flight
HRMS measurements were performed with a MicroTOF-Q type QqTOF MS instrument equipped with
an ESI source from Bruker (Bruker Daltoniks, Bremen, Germany).
3
.1. Computational Section
Mixed torsional/low mode conformational searches were carried out by means of the Macromodel
9
.7.211 software using Merck Molecular Force Field (MMFF) force field with implicit solvent model for
chloroform applying a 21 kJ/mol energy window [47]. Geometry reoptimizations [B3LYP/6-31G(d)
level in gas phase, B97D/TZVP and CAM-B3LYP/TZVP levels with PCM solvent model for n-octanol]
and TDDFT-ECD calculations were performed with Gaussian 09 using various functionals (B3LYP,
BH&HLYP, CAM-B3LYP, PBE0) and TZVP basis set for ECD calculations [48]. ECD spectra
−
1
were generated as the sum of Gaussians with 1800–2400 cm half-height width (corresponding
to ca. 16–22 nm at 300 nm), using dipole-velocity computed rotational strength values [49].
Boltzmann distributions were estimated from the ZPVE corrected B3LYP energies in the gas phase
calculations and from the uncorrected B97D and CAM-B3LYP energies in the PCM ones. The MOLEKEL
software package was used for visualization of the results [50].
3
.2. Bioassay on AChE Inhibitory Activity
The AChE assay was performed using the method of Ellman et al. with slight modification [51].
The cortex of Sprague–Dawley rat (400–500 g, obtained from the Animal Center of Shanghai Institute
of Materia Medica) was homogenized in cold sodium phosphate buffer (75 mM, pH 7.4) as the AChE
source. All the experimental procedures were approved by the Animal Care and Use Committee of
Shanghai Institute of Materia Medica (#2012-02-ZHY-32 and 2015-03-ZHY-64). The assay solution
0
consisted of 50
Sigma), 109 L of deionized water, 10
iodide (Sigma) as the substrate of the AChE enzymatic reaction. An appropriate concentration of
compound (0.1 mM to 5 mM; 1 L) and the assay solution were incubated for 20 min at room
temperature and the reaction was terminated with 50 L of 3% (w/v) sodium dodecylsulfate (SDS).
µL of 0.1 M phosphate buffer, 50
µL of 0.2% 5,5 -dithiobis(2-nitrobenzoic acid) (DTNB,
µ
µL of rat cortex homogenate, and 30 µL of 2 mM acetylthiocholine
µ
µ
The production of the yellow anion of 5-thio-2-nitrobenzoic acid was measured with a microplate
reader (DTX 880, Beckman Coulter, Brea, CA, USA) at 450 nm. The inhibition percentage caused
by the presence of test compound was calculated, and the IC50 was defined as the concentration
of the compound that reduced 50% of the enzymatic activity without inhibitor. The bioassay on
neuroprotective activity was carried out according to the reference 25.
3
,4-Dihydro-1,4-benzoxazepin-5(2H)-one (rac-8a): To a stirred solution of chroman-4-one (7a) (10.0 g,
6
7.49 mmol) in water and sulfuric acid 1:1 (100 mL), sodium azide (6.6 g, 101.5 mmol) was added
◦
in two equal portions at 0 C and stirred at room temperature. The reaction was monitored by
TLC,visualized under a UV lamp and developed by phosphomolybdic acid solution. After 5 h,
the reaction mixture was neutralized with sodium hydroxide solution and the aqueous layer was
extracted with dichloromethane (5
×
50 mL). The combined organic layers were washed with water
(
50 mL), dried over MgSO , filtered and concentrated under reduced pressure. The crude product was
4
purified by column chromatography on silica (EtOAc/hexane 2:5) to afford the rac-8a product as white
◦
◦
1
solid [8.60 g, 52.71 mmol, 78%, mp 109–110 C (lit. [52] mp 115–116 C)]. H NMR (400 MHz, CDCl ):
3
δ
= 3.50 (dd, J = 9.6 Hz and 5.2 Hz, 3-H, 2 H), 4.39 (m, J = 9.6 Hz and 5.2 Hz, 2-H, 2 H), 7.03 (d, J = 8.0
Hz, 9-H, 1 H), 7.10 (m, 7-H, 1 H), 7.4 (m, 8-H, 1 H), 7.9 (dd, J = 8.0 Hz and 1.6 Hz, 6-H, 1 H), 8.2 (br s,
-H, 1 H). 1 C NMR (100 MHz, CDCl3):
3
δ
= 41.3 (C-3), 73.2 (C-2), 121.3 (C-9), 122.8 (C-7), 123.9 (C-5a),
4

Molecules 2020, 25, 1265
10 of 19
−
1
1
31.6 (C-6), 133.3 (C-8), 155.3 (C-9a), 170.9 (C-5). IR (KBr): 1661, 3060, 3183, 3287 cm . HRMS-ESI
+
(m/z): [M + Na] calc’d for C H NO Na, 186.053; found: 186.053.
9 9 2
2
,3,4,5-Tetrahydro-1,4-benzoxazepine (rac-9a): To a stirred solution of rac-8a (4.0 g, 24.51 mmol) in
dry THF (60 mL), 2.0 M lithium aluminium hydride solution in THF (5 mL, 0.38 g, 10.02 mmol) was
added dropwise and the mixture was refluxed for 3 h. After cooling to room temperature, ethyl-acetate
(5 mL), methanol (5 mL) and water (50 mL) were added and the mixture was concentrated under
reduced pressure. The residue was extracted with dichloromethane (3 50 mL). The combined organic
×
layers were washed with water (20 mL), dried over MgSO , filtered and concentrated under reduced
4
1
pressure. The rac-9a product was isolated as yellow oil (2.92 g, 80%) [53]. H NMR (400 MHz, CDCl ):
3
δ
= 2.17 (s, 4-H, 1 H), 3.15 (m, 3-H, 2 H), 3.90 (s, 5-H, 2 H), 3.96 (m, 2-H, 2 H), 6.92–7.00 (m, 7-H and 9-H,
2
H), 7.08–7.20 (m, 6-H and 8-H, 2 H). 13C NMR (100 MHz, CDCl3):
δ
= 52.0 (C-5), 52.8 (C-3), 74.8 (C-2),
1
2
20.8 (C-9), 123.2 (C-7), 128.1 (C-6), 129.1 (C-8), 134.6 (C-5a), 159.8 (C-9a). IR (KBr): 766, 1226, 1488,
−1
+
858, 2932, 3312 cm . HRMS-ESI (m/z): [M + Na] calc’d for C H NONa, 172.074; found: 186.074.
9
11
2-(2,3-Dihydro-1,4-benzoxazepin-4(5H)-yl)-5-nitrobenzaldehyde (rac-1a): To the stirred solution of
rac-9a (1.50 g, 9.19 mmol) in dry toluene (25 mL), anhydrous K CO (1.85 g, 13.39 mmol) and
2
3
2
-fluoro-5-nitrobenzaldehyde (2.04 g, 12.06 mmol) were added and the mixture was refluxed for 5 h.
After cooling to room temperature, the K CO was filtered off and toluene was removed under reduced
2
3
pressure. The residue was purified by column chromatography on silica gel (ethyl-acetate/hexane 4:1)
◦
1
to give rac-1a as yellow solid (2.61 g, 95%, mp 101–102 C). H NMR (400 MHz CDCl ):
δ = 3.79 (m,
3
J = 4.8 Hz, 3-H, 2 H), 4.35 (m, J = 4.8 Hz, 2-H, 1 H), 4.73 (s, 5-H, 2 H), 6.97 (d, J = 7.6 Hz, 9-H, 1 H),
0
7
.01 (d, J = 9.2 Hz, 6 -H, 1 H), 7.09 (m, 7-H, 1 H), 7.23–7.27 (m, 6-H and 8-H, 2 H), 8.13 (dd, J = 9.2 Hz
0
0
13
and 2.8 Hz, 5 -H, 1 H), 8.61 (d, J = 2.8 Hz, 3 -H, 1 H), 9.99 (s, 1H, -CHO). C-NMR (100 MHz, CDCl ):
3
0
0
δ
= 55.9 (C-3), 58.21 (C-5), 70.34 (C-2), 117.3 (C-9), 120.4 (C-6 ), 123.4 (C-7), 124.0 (C-6a), 126.7 (C-2 ),
0 0 0 0
1
*
29.0 (C-3 ), 129.3* (C-8), 129.4* (C-6), 129.8* (C-5 ), 139.7 (C-4 ), 156.7 (C-9a), 158.7 (C-1 ), 188.4 (-CHO).
−1
+
exchangable signals. IR (KBr): 761, 1330, 1491, 1600, 1684 cm . HRMS-ESI (m/z): [M + Na] calc’d for
C H N O Na, 321.085; found: 321.085.
16
14
2
4
2-(2,3-Dihydro-1,4-benzoxazepin-4(5H)-yl)-5-nitrobenzylidene]propanedinitrile (rac-12a): To a stirred
solution of rac-1a (100 mg, 0.34 mmol) in chloroform (10 mL), anhydrous MgSO (150 mg, 1.24 mmol)
4
and malononitrile (130 mg, 1.97 mmol) were added and the mixture was refluxed for 8 h. After cooling
to room temperature, the MgSO was filtered off and chloroform was removed under reduced pressure.
4
Water (10 mL) and dichloromethane (20 mL) were added, the two layers were separated and the
aqueous phase was washed with dichloromethane (2
×
10 mL). The combined organic layers were
washed with concentrated NaHCO solution, dried over MgSO , filtered and concentrated under
3
4
reduced pressure. The oily product was crystallized with ether to give rac-12a as brown solid (72 mg,
◦
1
6
5
(
2%, mp 246–248 C). H NMR (400 MHz CDCl ):
δ
= 3.75 (m, 3-H, 2 H), 4.34 (m, 2-H, 2 H), 4.45 (s,
3
0
-H, 2 H), 7.07 (d, J = 8.0 Hz, 6-H, 1 H), 7.15–7.20 (m, 3 -H,7-H, 9-H, 3 H), 7.26-7.33 (m, 8-H, 1 H), 7.73
s, 7 -H, 1 H), 8.2 (dd, J = 9.2 Hz and 2.4 Hz, 4 -H, 1 H), 8.84 (d, J = 2.4 Hz, 6 -H, 1 H). C NMR (100
0
0
0
13
MHz, CDCl ):
δ = 56.8 (C-3), 59.1 (C-5), 70.6 (C-2), 84.1 (C-2”),111.8 (CN), 112.9 (CN), 118.8 (C-9), 120.8
3
0
0
0
0
(
(
(
C-3 ), 121.5 (C-1 ), 124.1 (C-7),125.9 (C-6 ), 127.6 (C-5a), 128.9 (C-4 ), 129.4 (C-6), 129.8 (C-8), 140.9
C-5 ), 156.9 (C-7 ), 158.2 (C-9a), 159.2 (C-2 ). IR (KBr): 781, 1509, 1570, 2232, 2925 cm . HRMS-ESI
m/z): [M + Na] calc’d for C H N O Na, 369.096; found: 369.096.
0
0
0
−1
+
19
14
4
3
1
,3-Dimethyl-11’-nitro-1’,2’-dihydro-2H,7b’H,9’H-spiro[pyrimidine-5,8’-quinolino[1,2-d][1,4]benzoxazepine]
2,4,6(1H,3H)-trione (rac-10a): To a stirred solution of rac-1a (100 mg, 0.34 mmol) in chloroform (10 mL),
anhydrous MgSO (150 mg, 1.25 mmol) and 1,3-dimetylbarbituric acid (80 mg, 0.51 mmol) were
-
4
added and the mixture was refluxed for 6 h. After cooling to room temperature, the MgSO was
4
filtered off and chloroform was removed under reduced pressure. Water (10 mL) and dichloromethane
(20 mL) were added and two layers were separated. The aqueous phase was extracted with
dichloromethane (2 × 10 mL). The combined organic layers were washed with concentrated NaHCO3

Molecules 2020, 25, 1265
11 of 19
solution, dried over MgSO , filtered and concentrated under reduced pressure. The oily product
4
◦
1
was crystallized with ether to give rac-10a as yellow solid (139 mg, 95%, mp 247–250 C). H NMR
400 MHz DMSO-d6): = 2.76 (s, N-CH , 3 H), 2.89 (s, N-CH , 3 H), 3.20 (d, J = 17.2 Hz, 9-H , 1 H),
.48 (m, 3-H , 1 H), 3.71–3.76 (overlapping m, 9-H and 3-H , 2 H), 3.99–4.05 (m, 2-H , 1 H), 4.22 (m,
J = 3.6 Hz and 16.4 Hz, 2-H , 1 H), 4.82 (s, 15-H , 1 H), 6.98–7.02 (m, 16-H, 19-H, 2 H), 7.10 (d, J = 9.2
Hz, 5-H, 1 H), 7.17 (m, 17-H, 1 H), 7.39 (m, 18-H, 1 H), 7.97 (dd, J = 9.2 Hz and 2.8 Hz, 6-H, 1 H), 8.02
bs, 8-H, 1 H). 13C NMR (100 MHz, DMSO-d6):
= 28.0 (N-CH ), 28.1 (N-CH ), 33.6 (C-9), 42.8 (C-3),
1.3 (C-10), 69.8 (C-2), 70.5 (C-15a), 109.9 (C-5), 121.9 (C-15b), 122.4 (C-6), 123.1 (C-8), 124.4 (C-17, C-19),
27.2 (C-8a), 129.7 (C-18), 131.7 (C-16), 136.1 (C-7), 148.4 (C-13), 149.9 (C-19a), 152.9 (C-4a), 166.8 (C-15),
(
3
δ
a
3
3
a
b
b
a
b
a
(
5
1
1
4
δ
3
3
−1
+
68.8 (C-11). IR (KBr): 1320, 1680, 2924 cm . HRMS-ESI (m/z): [M + Na] calc’d for C H N O Na,
22
20
4
6
59.128; found: 459.128.
,2-Dimethyl-11’-nitro-1’,2’-dihydro-7b’H,9’H-spiro[1,3-dioxane-5,8’-quinolino[1,2-d][1,4]benzoxazepine]
4,6-dione (rac-11a): To the stirred solution of rac-1a (100 mg, 0.34 mmol) in chloroform (10 mL),
anhydrous MgSO (150 mg, 1.25 mmol) and Meldrum’s acid (98 mg, 0.68 mmol) were added and the
2
-
4
mixture was refluxed for 6 h. After cooling to room temperature, the MgSO was filtered off and
4
chloroform was removed under reduced pressure. Water (10 mL) and dichloromethane (20 mL) were
added and layers were separated. The aqueous phase was washed with dichloromethane (2 × 10 mL)
and the combined organic layers were washed with concentrated NaHCO solution, dried over
3
MgSO , filtered and concentrated under reduced pressure. The oily product was crystallized with
4
◦
1
ether to give rac-11a as yellow solid (123 mg, 87%, mp 236–238 C). H NMR (360 MHz, DMSO-d ):
6
δ
1
7
= 0.94 (s, CH 3 H), 1.58 (s, CH , 3 H), 3.57 (m, 3-H
a
, 9-H, 3 H), 3.71 (m, 2-H
a
, 1 H), 4.03 (m, 3-Hb,
3,
3
H), 4.20 (m, 2-H , 1 H), 5.01 (s, 15a-H, 1 H), 7.07-7.14 (m, H-16, H-17, H-19, 3 H), 7.21 (m, 18-H, 1 H),
b
13
.45 (m, 6-H, 1 H), 8.00 (m, 5-H, 8-H, 2 H). C NMR (90 MHz, CDCl3):
δ = 26.4 (CH ), 29.5 (CH ), 34.6
3 3
(
C-9), 43.2 (C-3), 49.3 (C-10), 68.9 (C-2), 69.7 (C-15a), 105.2 (C-13), 110.0 (C-19), 119.9 (C-8a), 122.8 (C-5),
1
1
23.7 (C-6), 124.6 (C-8), 124.7 (C-17), 130.4 (C-18), 131.5 (C-16), 135.9 (C-7), 148.3 (C-19a), 153.6 (C-4a),
63.6 (C-15), 167.7 (C-11). IR (KBr): 1262, 1313, 1736, 2924 cm .
−
1
2-(Naphthalen-1-yl)-chroman-4-one (rac-7b): To the stirred solution of the corresponding chalcone
derivative (4.3 g, 16mmol) in EtOH, 130 mL of cc. NaOAc solution was added and refluxed for 5 h.
After cooling it down to room temperature, EtOH was removed under reduced pressure. After addition
of water, the aqueous layer was extracted with dichloromethane (5
×
50 mL). The combined organic
layers were dried over MgSO , filtered and concentrated under reduced pressure. The oily crude product
4
◦
was crystallized with cold diisopropyl-ether affording yellow crystals (3.14 g, 73%, mp 74–76 C) [54].
1
H-NMR (360 MHz, CDCl3):
δ
= 3.05 (dd, J = 14.4 and 3.6 Hz, 1 H, 3-H
a
), 3.24 (dd, J = 14.4 and 10.8 Hz,
0
0
1
3
H, 3-H ), 6.19 (dd, J = 10.8 Hz and 3.6 Hz, 1 H, 2-H), 7.07-7.52 (m, 2 H, 6 -H, 7 -H), 7.53–7.57 (m, 4 H,
-H, 4 -H, 5 -H, 8 -H), 7.75 (d, 1 H, 8-H), 7.89 (m, 2 H, 2 -H, 6 -H), 8.00 (m, 2 H, 5-H, 7-H). C-NMR
b
0
0
0
0
0
0
13
0
(
(
(
90 MHz, CDCl ):
δ
= 43.9 (C-3), 76.8 (C-2), 118.2 (C-8), 121.1 (C-4a), 121.7 (C-6), 122.8 (C-8 ), 123.8
3
0
0
0
0
0
0
C-3 ), 125.3 (C-6 ), 125.9 (C-2 ), 126.6 (C-7 ), 127.1 (C-5), 129.1 (C-4 ), 129.3 (C-5 ), 130.1 (C-8a’), 133.8
−
1
C-4a’), 134.1 (C-1), 136.2 (C-7), 161.7 (C-8a), 192.2 (C-4). IR (KBr): 1222, 1302, 1606, 1684, 3050 cm .
-(Naphthalen-2-yl)-chroman-4-one (rac-7c): To a stirred solution of the chalcone derivative (4.3 g,
6 mmol) in EtOH, 130 mL of cc. NaOAc solution was added and refluxed for 5 h. After cooling it
2
1
down to room temperature, EtOH was removed under reduced pressure. The residue was taken in
water and extracted with dichloromethane (5 50 mL). The combined organic layers were dried over
MgSO , filtered and concentrated under reduced pressure. The oily crude product was crystallized
×
4
◦
1
with cold diisopropyl-ether affording yellow crystals (3.27 g, 76%, mp 110–112 C) [54]. H-NMR
360 MHz, CDCl3): = 2.90 (dd, J = 16.5 Hz and 2.5 Hz, 1 H, 3-H ) 3.09 (dd, J = 16.5 Hz and 13.0
Hz, 1 H, 3-H ). 5.56 (dd, J=13.0 Hz and 2.5 Hz, 1 H, 2-H). 7.01-7.07 (m, 2 H, 6 -H, 7 -H). 7.47–7.55
(
δ
a
0
0
b
0
0
0
0
0
(m, 4 H, 3 -H, 4 -H, 5 -H, 8 -H). 7.82–7.92 (m, 5 H, 5-H, 1 -H, 5-H, 6-H, 7-H), 7.93 (d, J = 7.6 Hz, 1 H,
8
-H). 13C-NMR (90 MHz, CDCl3):
δ
= 44.5 (C-3), 79.6 (C-2), 118.1 (C-8), 120.9 (C-4a), 121.6 (C-6), 123.6

Molecules 2020, 25, 1265
12 of 19
0 0 0 0 0 0 0
C-3 ), 125.3 (C-4 ), 126.4 (C-6 , C-7 ), 127.0 (C-1 ), 127.7 (C-5 ), 128.1 (C-5), 128.7 (C-8 ), 133.1 (C-8a’),
(
0
−1
1
33.3 (C-4a’), 135.9 (C-2 ), 136.2 (C-7), 161.4 (C-8a), 191.8 (C-4). IR (KBr): 1063, 1223, 1688, 3025 cm .
2-(Naphthalen-1-yl)-3,4-dihydrobenzo[f][1,4]oxazepin-5(2H)-one (rac-8b): To the stirred soluton of
rac-7b (3.0 g, 11 mmol) in acetic acid (30 mL), sodium azide (1.1 g, 17 mmol) was added in two parts
◦
at 0 C, then 3.0 mL of cc. H SO was added dropwise, and the reaction mixture was stirred at
2
4
room temperature for 5 h. The reaction mixture was neutralized with sodium hydroxide solution
and extracted with dichloromethane (5 50 mL). The combined organic layers were dried over
×
MgSO , filtered and concentrated under reduced pressure. The crude product was purified by column
4
chromatography on silica (hexane/EtOAc 4:1) to give the product as white powder (3.14 g, 73%,
◦
1
mp 74–76 C). H-NMR (400 MHz, CDCl ):
δ
a
b
= 3.57–3.62 (m, 1 H, 3-H ) 3.65–3.71 (m, 1 H, 3-H ), 5.58
3
(
7
m, 1 H, 2-H), 7.10 (d, J = 8.0 Hz 1 H, 9-H), 7.21 (m, 1 H, 7-H), 7.46-7.49 (m, 4 H, 2-H’, 3-H’, 6-H, 8-H),
0
0
0
0
0
13
.62 (s, 1 H, 4-H), 7.81–7.85 (m, 5 H, 4 -H, 5 -H, 6 -H, 7 -H, 8 -H), C-NMR (100 MHz, CDCl ):
δ
= 46.2
3
0
0
0
0
(
C-3), 85.9 (C-2), 122.5 (C-9), 123.8 (C-7), 124.0 (C-8 ), 125.5 (C-2 ), 125.9 (C-5a), 126.4 (C-6 ), 126.5 (C-3 ),
0
0
0
1
1
27.7 (C-7 ), 128.2 (C-4 ), 128.5 (C-5 ), 131.0 (C-6), 133.1 (C-8a’), 133.3 (C-4a’), 133.4 (C-8), 154.6 (C-9a),
−1
+
71.2 (C-5), IR (KBr): 1024, 1217, 1462, 1604, 1655, 3062, 3212, 3283 cm . HRMS-ESI (m/z): [M + Na]
calc’d for C H NO Na, 312.100; found: 312.099.
19
19
2
2-(Naphthalen-2-yl)-3,4-dihydrobenzo[f][1,4]oxazepin-5(2H)-one (rac-8c): To the stirred solution of
rac-7c (3.0 g, 11 mmol) in acetic acid (30 mL), sodium azide (1.1 g, 17 mmol) was added in two
◦
parts at 0 C, then 3.0 mL of cc. H SO was added dropwise and stirred at room temperature for
2
4
5
h. The reaction mixture was neutralized with sodium hydroxide solution and the aqueous mixture
was extracted with dichloromethane (5 50 mL). The combined organic layers were dried over
×
MgSO , filtered and concentrated under reduced pressure. The crude product was purified by column
4
chromatography on silica (hexane/EtOAc 4:1) to give the product as white powder (3.27 g, 76%, mp
◦
10–112 C). H-NMR (400 MHz, CDCl ) δ = 3.55–3.69 (m, 2 H, 3-H), 5.57 (br s, 1H, 2-H), 7.09 (d,
3
J = 8.0 Hz, 1 H, 9-H), 7.18 (m, 1 H, 7-H), 7.47 (m, 4 H, 2 -H, 3 -H, 6-H, 8-H), 7.82-7.84 (m, 5 H 4 -H,
1
1
0
0
0
0
0
0
0
13
0
5
1
1
-H, 6 -H, 7 -H, 8 -H), C-NMR (100 MHz, CDCl ):
δ
= 46.2 (C-3), 85.9 (C-2), 122.5 (C-9), 123.8 (C-1 ),
3
0
0
0
0
0
24.0 (C-9), 125.5 (C-7), 125.9 (C-5a), 126.4 (C-6 ), 126.5 (C-7 ), 127.7 (C-5 ), 128.2 (C-4 ), 128.5 (C-8 ),
31.0 (C-6), 133.1 (C-8a’), 133.3 (C-4a’), 133.4 (C-8), 136.4 (C-2 ), 154.6 (C-9a), 171.2 (C-5). IR (KBr):
064, 1223, 1299, 1460, 1696, 2958 cm . HRMS-ESI (m/z): [M + Na] calc’d for C H NO Na, 312.100;
0
−1
+
1
19
19
2
found: 312.099.
2-(Naphthalen-1-yl)-2,3,4,5-tetrahydrobenzo[f][1,4]oxazepine (rac-9b): To the stirred solution of rac-8b
(
2.0 g, 6.9 mmol) in dry THF (10 mL), lithium aluminum hydride solution in hexane (2.0 M) was added
dropwise (10 mL, 0.72 g, 20.04 mmol) and the mixture was refluxed for 1 h. After cooling to room
temperature, 20 mL 4 M NaOH solution was added and the mixture was concentrated under reduced
pressure. The residue was extracted with dichloromethane (3
×
50 mL). The combined organic layers
were dried over MgSO , filtered and concentrated under reduced pressure. The product was isolated
4
1
as brown oil (1.82 g, 91%). H-NMR (400 MHz, CDCl ):
Hz and 8.0 Hz, 1 H, 3-Ha), 3.44 (d, J = 12.0 Hz, 1 H, 3-H
δ
= 1.86 (br s, 1 H, 4-H) 3.24–3.45 (dd, J = 12.0
), 3.97 (d, J = 16.0 Hz, 1 H, 5-H ), 4.15 (d, J
12.0 Hz, 1 H, 5-H ), 4.80 (d, J = 8.0 Hz, 1 H, 2-H), 7.01–7.09 (m, 2 H, 7-H, 9-H), 7.16–7.21 (m, 2 H,
3
a
a
=
b
0
0 0 0 0 0 0
13
5
-H, 6-H), 7.46–7.52 (m, 3 H, 2 -H, 3 -H, 8-H), 7.82–7.88 (m, 4 H, 4 -H, 6 -H, 7 -H, 8 -H), C-NMR (100
0 0
δ = 52.6 (C-5), 59.0 (C-3), 86.5 (C-2), 121.7 (C-9), 123.8 (C-7), 124.1 (C-8 ), 124.7 (C-6 ),
MHz, CDCl ):
3
0
0
0
1
26.0 (C-2 ), 126.3 (C-3 ), 127.8 (C-7), 128.0 (C-4), 128.2 (C-8), 128.5 (C-6), 129.1 (C-5 ), 132.9 (C-5a), 133.3
0
−1
.
(
C-8a’), 135.7 (C-4a’), 137.9 (C-1 ), 159.2 (C-9a), IR (KBr): 1047, 1232, 1483, 1599, 2899, 3241, 3315 cm
-(Naphthalen-2-yl)-2,3,4,5-tetrahydrobenzo[f][1,4]oxazepine (rac-9c): To the stirred solution of rac-8c
2.0 g, 6.9 mmol) in dry THF (10 mL), lithium aluminum hydride solution in hexane (2.0 M) was added
2
(
dropwise (10 mL, 0.72 g, 20.04 mmol) and the mixture was refluxed for 1 h. After cooling to room
temperature, 20 mL 4 M NaOH solution was added and the mixture was concentrated under reduced
pressure. The residue was extracted with dichloromethane (3
×
50 mL). The combined organic layers

Molecules 2020, 25, 1265
13 of 19
were dried over MgSO , filtered and concentrated under reduced pressure. The product was isolated
4
1
as brown oil (1.88g, 94%). H-NMR (400 MHz, CDCl ):
δ
= 1.94 (br s, 1 H, 4-H). 3.25–3.47 (m, 1 H,
), 4.16 (d, J = 16.0 Hz 1 H, 5-Hb),
.81 (d, J = 8.0 Hz 1 H, 2-H), 7.02-7.10 (m, 2 H, 6-H, 8-H), 7.17–7.22 (m, 2 H, 7-H, 9-H), 7.45–7.52 (m, 3 H,
3
3
4
b
a a
-H ), 3.45 (d, J = 16.0 Hz, 1 H, 3-H ), 3.98 (d, J = 16.0 Hz, 1 H, 5-H
0
0
0
0
0
0
0
13
3
5
-H, 6 -H, 8 -H), 7.82-7.89 (m, 4 H, 1 -H, 4 -H, 5 -H, 7 -H), C-NMR (100 MHz, CDCl ):
δ
= 52.6 (C-5),
3
0
0
0
0
9.0 (C-3), 86.5 (C-2), 121.7 (C-9), 123.8 (C-7), 124.1 (C-3 ), 124.7 (C-1 ), 126.0 (C-6 ), 126.3 (C-7 ), 127.7
0
0
0
(
C-4 ), 128.1 (C-8), 128.2 (C-5 ), 128.5 (C-8 ), 129.1 (C-6), 132.9 (C-5a), 133.3 (C-8a’), 135.7 (C-4a’), 137.9
0
−1
(
C-2 ), 159.2 (C-9a), IR (KBr): 1078, 1241, 1470, 2963, 3240, 3350 cm .
-(Naphthalen-1-yl)-4-(4-nitrophenyl)-2,3,4,5-tetrahydrobenzo[f][1,4]oxazepine (rac-1b): To the stirred
solution of rac-9b (1.30 g, 4.70 mmol) in dry toluene (20 mL), 2-chloro-5-nitrobenzaldehyde (1.75 g
2
9
5
.4 mmol) and anhydrous K CO (3.2 g 2.3 mmol) were added and the mixture was refluxed for
2 3
h. After cooling to room temperature, the K CO was filtered off and toluene was removed under
2
3
reduced pressure. The residue was purified by column chromatography on silica gel (hexane/EtOAc
◦
:1) affording the product as yellow solid (1.01 g, 78%, mp 179–181 C). H-NMR (400 MHz, CDCl ):
3
1
4
δ
= 3.71 (dd, J = 14.0 Hz and 9.0 Hz, 1 H, 3-H
a
b
) 4.12 (dd, J = 14.0 Hz and 4.0 Hz, 1 H, 3-H ), 4.74 (d,
J = 16.0 Hz,1 H, 5-H
a
), 4.95 (d, J = 16.0 Hz, 1 H, 5-H ), 5.45 (dd, J = 9.0 Hz and 4.0 Hz, 1 H, 2-H), 7.05
b
0 0
(
4
(
m, 2 H, 7-H, 9-H), 7.15–7.17 (m, 1 H, 6”-H), 7.30-7.32 (m, 2 H, 6-H, 8-H), 7.49–7.52 (m, 3 H, 2 -H, 3 -H,
0
0 0 0 0
-H), 7.84–7.89 (m, 4 H, 5 -H, 6 -H, 7 -H, 8 -H), 8.13–8.16 (dd, J = 8.0 Hz and 2. 8 Hz, 1 H, 5”-H), 8.60
d, J = 2.8 Hz, 1 H, 3”-H), 9.95 (s, 1 H, CHO), 13C-NMR (100 MHz, CDCl ):
δ
= 56.3 (C-5), 64.5 (C-3),
3
0
0
0
8
2.9 (C-2), 117.8 (C-9), 121.1 (C-6”), 123.6 (C-7), 124.0 (C-8 ), 124.4 (C-5a), 125.1 (C-6 ), 126.5 (C-2 ), 126.6
0
0
0
0
(C-3 ), 127.8 (C-7 ), 128.1 (C-8), 128.7 (C-4 ), 129.2 (C-3”), 129.3 (C-5 ), 129.5 (C-6), 129.9 (C-5”), 133.1
0
(
C-8a’), 133.2 (C-4a’), 135.5 (C-4”), 140.0 (C-1 ), 156.8 (C-9a), 158.3 (C-1”), 188.4 (CHO). IR (KBr): 1489,
−
1
+
1600, 1684, 2750, 2917, 3053 cm . HRMS-ESI (m/z): [M + Na] calc’d for C H N O Na, 447.132;
26
20
2
4
found: 447.132.
2
-(Naphthalen-2-yl)-4-(4-nitrophenyl)-2,3,4,5-tetrahydrobenzo[f][1,4]oxazepine (rac-1c): To the stirred
solution of rac-9c (1.30 g, 4.70 mmol) in dry toluene (20 mL), 2-chloro-5-nitrobenzaldehyde (1.75 g,
.4 mmol) and anhydrous K CO (3.2 g, 2.3 mmol) were added and the mixture was refluxed for 5
9
2
3
h. After cooling to room temperature, the K CO was filtered off and toluene was removed under
2
3
reduced pressure. The residue was purified by column chromatography on silica gel (hexan/EtOAc 4:1)
◦
1
to give the product as yellow solid (1.05 g, 81%, mp 124–126 C). H-NMR (400 MHz, CDCl ):
δ
= 3.70
), 4.95 (d, J = 16.0 Hz, 1
H, 5-H ), 5.45 (d, J = 12.0 Hz, 1 H, 2-H), 7.02–7.16 (m, 3 H, 5 -H, 6”-H, 8 -H), 7.25–7.32 (m, 2 H, 7-H,
3
(
b
a a
m, 1 H, 3-H ), 4.12 (d, J = 12.0 Hz, 1 H, 3-H ), 4.73 (d, J = 16.0 Hz, 1H, 5-H
0
0
b
0 0 0 0 0 0 0
9
1
(
1
1
1
-H), 7.79–7.51 (m, 3 H, 6 -H, 7 -H, 8 -H), 7.83–7.89 (m, 4 H, 1 -H, 3 -H, 4 -H, 6 -H), 8.13 (dd, J = 8.0 Hz,
H, 5”-H), 8.59 (d, J = 2.8 Hz, 1H, C-3”), 9.94 (s, 1 H, CHO), 13C-NMR (100 MHz, CDCl ):
δ
= 56.3
3
0
0
0
C-5), 64.5 (C-3), 82.9 (C-2), 117.7 (C-9), 121.1 (C-6”), 123.6 (C-7), 123.9 (C-3 ), 124.4 (C-5a), 125.1 (C-1 ),
26.4 (C-6 ), 126.5 (C-6 ), 126.6 (C-7 ), 127.7 (C-2 ), 127.8 (C-4 ), 127.9 (C-8), 128.6 (C-3”), 129.1 (C-5 ),
29.2 (C-8 ), 129.4 (C-6), 129.8 (C-5”), 133.1 (C-8a’), 133.2 (C-4a’), 135.5 (C-4”), 139.9 (C-2 ’), 156.8 (C-9a),
58.3 (C-1”), 188.4 (CHO), IR (KBr): 1238, 1326, 1503, 1598, 1680, 2918, 3058 cm . HRMS-ESI (m/z):
0
0
0
0
0
0
0
−
1
+
[
M + Na] calc’d for C H N O Na, 447.132; found: 447.132.
26 20 2 4
1,3-Dimethyl-2’-(naphthalen-1-yl)-11’-nitro-1’,2’-dihydro-2H,7b’H,9’H-spiro[pyrimidine-5,8’-quinolino
[1,2-d][1,4]benzoxazepine]-2,4,6(1H,3H)-trione (rac-10b): To the stirred solution of rac-1b (100 mg,
0
.23 mmol) in chloroform (5 mL), anhydrous MgSO (150 mg, 1.25 mmol) and barbituric acid (38 mg,
4
0.29 mmol) were added and the mixture was refluxed for 24 h. After cooling to room temperature,
the MgSO was filtered off and chloroform was removed under reduced pressure. The residue was
4
purified by column chromatography on silica gel (hexane/EtOAc 1:1) affording the product as yellow
◦
1
solid (36 mg, 36%, mp 289–291 C) H-NMR (400 MHz, DMF-d ):
δ = 2.71 (s, 3 H, CH ), 2.98 (s, 3 H,
3
7
CH ), 3.31 (d, J = 16.0 Hz, 1 H, 9-Ha), 3.83 (d, J = 16.0 Hz, 1H, 9-Hb), 4.10 (m, 1 H, 3-Ha), 4.61 (d,
3
J = 16.0 Hz, 1 H, 3-Hb), 4.88 (s, 1 H, 15a-H), 5.79 (m, 1 H, 2-H), 6.09 (m, 1 H, 5-H), 7.00–7.04 (m, 5 H,
0
Ph-H), 7.26–7.33 (m, 3 H, Ph-H), 7.48–7.61 (m, 2 H, Ph-H), 7.85–7.93 (m, 2 H, Ph-H), 8.03 (s, 1H, 8 -H),

Molecules 2020, 25, 1265
14 of 19
8
.13 (d, J = 8.0 Hz, 1 H, 6-H). 13C-NMR (100 MHz, DMF-d7):
δ
= 29.0 (CH ) 29.1 (CH ), 46.7 (C-9), 53.1
3
3
(
(
(
(
2
C-15a), 72.2 (C-3), 76.6 (C-10), 111.6 (C-2), 105.5 (C-13), 123.7 (C-19), 124.2 (C-5), 124.6 (C-17), 124.7
0
0
0
0
0
C-15b), 124.8 (C-6) 125.7 (C-8), 125.8 (C-8 ), 124.8 (C-2 ), 127.1 (C-6 ), 127.8 (C-3 ), 128.8 (C-7 ), 129.9
0
0
0
C-18), 130.4 (C-4 ), 131.2 (C-5 ),132.3 (C-16) 132.7 (C-8a’), 133.7 (C-4a’), 135.1 (C-7), 138.3 (C-1 ), 149.9
C-13), 151.4 (C-19a), 152.4 (C-4a), 168.6 (C-15), 170.3 (C-11). IR (KBr): 1322, 1601, 1683, 1698, 2853,
−1
+
923 cm . HRMS-ESI (m/z): [M + Na] calc’d for C H N O Na, 585.175; found: 585.175.
32
26
4
6
1
,3-Dimethyl-2’-(naphthalen-2-yl)-11’-nitro-1’,2’-dihydro-2H,7b’H,9’H-spiro[pyrimidine-5,8’-quinolino
1,2-d][1,4]benzoxazepine]-2,4,6(1H,3H)-trione (rac-10c): To the stirred solution of rac-1c (100 mg,
.23 mmol) in chloroform (5 mL), anhydrous MgSO (150 mg, 1.25 mmol) and 1,3-dimethylbarbituric
[
0
4
acid (38 mg, 0.29 mmol) were added and the mixture was refluxed for 24 h. After cooling to room
temperature, the MgSO was filtered off and the chloroform was removed under reduced pressure.
4
The residue was crystallized with cold diisopropyl-ether affording the product as yellow solid (52 mg,
◦
5
1
2%, mp 312–314 C) The sample could not be dissolved in NMR solvents. IR (KBr): 1320, 1507, 1680,
−1
+
746, 2953, 3057 cm . HRMS-ESI (m/z): [M + Na] calc’d for C H N O Na, 585.175; found: 585.175.
32
26
4
6
2
,2-Dimethyl-2’-(naphthalen-1-yl)-11’-nitro-1’,2’-dihydro-7b’H,9’H-spiro[1,3-dioxane-5,8’-quinolino[1,2-d]
1,4]benzoxazepine]-4,6-dione (rac-11b): To the stirred solution of rac-1b (100 mg, 0.23 mmol) in
chloroform (5 mL), anhydrous MgSO (150 mg, 1.25 mmol) and Meldrum’s acid (43 mg, 0.29 mmol)
[
4
were added and the mixture was refluxed for 24 h. After cooling to room temperature, the MgSO was
4
filtered off and the chloroform was removed under reduced pressure. The residue was purified by
column chromatography on silica gel (hexane/EtOAc 2:1) affording the product as yellow solid (50 mg,
◦
1
5
0%, mp 160–162 C). H-NMR (400 MHz, CDCl ):
δ
= 1.05 (s, 3 H, CH ), 1.65 (s, 3 H, CH ), 3.24 (d,
3 3
3
J = 16.0 Hz, 1 H, 9-H
a
), 3.90 (d, J = 16.0 Hz, 1 H, 9-H ), 4.19 (m, 1 H, 3-H
a
), 4.33 (m, 1 H, 3-H ), 5.08 (s,
b
b
1
7
2
4
H, 15a-H), 6.08 (d, J = 8.0 Hz, 1 H, 2-H), 6.55 (d, J = 8.0 Hz, 1 H, 5-H), 6.88(d, J = 8.0 Hz, 1 H, 17-H),
.02 (m, 1 H, Ar-H), 7.21–7.34 (m, 4 H, Ar-H), 7.57–7.62 (m, 2 H, Ar-H), 7.89 (m, 1 H, 16-H), 8.10 (m,
H, 6-H, 8-H), 8.31 (m, 1 H, 18-H). 13C-NMR (100 MHz, CDCl3):
δ = 26.9 (CH ) 30.4 (CH ), 35.9 (C-9),
3 3
6.5 (C-3), 49.9 (C-10), 70.6 (C-15a), 74.8 (C-2), 105.5 (C-13), 109.9 (C-19), 119.5 (C-5), 123.1 (C-17), 123.6
0 0 0 0
C-6), 124.3 (C-8), 124.4 (C-8 ), 124.8 (C-2 ), 125.1 (C-8a), 125.5 (C-6 ), 126.1 (C-3 ), 126.9 (C-15b), 126.9
(
0
0
0
0
(C-7 ), 128.7 (C-18), 129.5 (C-4 ), 130.8 (C-16), 131.3 (C-5 ), 131.5 (C-8a’), 132.5 (C-4a’), 133.8 (C-7), 137.9
(
C-1 ), 147.8 (C-19a), 152.2 (C-4a), 164.4 (C-15), 168.2 (C-11). IR (KBr): 1195, 1509, 1603, 1737, 1775, 2930,
−1
+
3
056 cm . HRMS-ESI (m/z): [M + Na] calc’d for C H N O Na, 573.164; found: 573.163.
32
20
2
7
2
’,2’-Dimethyl-2-(naphtalene-2-yl)11-nitro-1,2,7b,9-tetrahydrospiro[benzo[6,7][1,4]oxazepine[4,5-
a]quinoline-8,5’-[1,3]dioxane]-4’,6’-dione (rac-11c): To the stirred solution of rac-1c (100 mg, 0.23 mmol) in
chloroform (5 mL), anhydrous MgSO (150 mg, 1.25 mmol) and Meldrum’s acid (43 mg, 0.29 mmol)
4
were added and the mixture was refluxed for 24 h. After cooling to room temperature, the MgSO was
4
filtered off and the chloroform was removed under reduced pressure. The residue was purified by
column chromatography on silica gel (hexane/EtOAc 2:1) affording the product as yellow solid (98 mg,
◦
1
9
8%, mp 188–190 C). H-NMR (400 MHz, CDCl ):
δ
= 1.06 (s, 3 H, CH ) 1.62 (s, 3 H, CH ), 3.18 (d,
3 3
3
J = 16.0 Hz, 1 H, 9-H
a
), 3.88 (d, J = 16.0 Hz, 1 H, 9-H ), 4.09 (m, 1 H, 3-H
a
), 4.29 (dd, J = 16.0 Hz and 4.0
d,
J = 8.0 Hz, 2 H, 5-H and 19-H), 7.15-7.24 (m, 4 H, Ar-H), 7.26-7.32 (m, 3 H, Ar-H), 7.34–7.58 (m, 3 H,
b
Hz, 1 H, 3-H ), 5.04 (s, 1H, 15a-H), 5.42 (dd, J = 12.0 Hz and 4.0 Hz, 1 H, 2-H), 6.81 and 6.89 (2
×
b
0
13
Ar-H), 8.12 (m, 2 H, 1 -H, 8-H). C-NMR (100 MHz):
δ = 27.0 (CH ), 30.5 (CH ), 35.7 (C-9), 47.0 (C-3),
3 3
0
5
0.1 (C-10), 70.6 (C-15a), 80.1 (C-2), 105.05 (C-13), 110.1 (C-19) 119.5 (C-5), 124.3 (C-17), 124.9 (C-3 ),
0
0
0
0
1
1
1
25,1 (C-1 ), 125.2 (C-6), 125.5 (C-8), 126.4 (C-8a), 126.5 (C-6 ), 126.6 (C-7 ), 126.8 (C-15b), 127.6 (C-4 ),
28.1 (C-5 ), 128.4 (C-8), 131.0 (C-8 ), 131.4 (C-16), 132.9 (C-8a’), 133.3 (C-4a’), 134.6 (C-7), 137.9 (C-2 ),
47.7 (C-19a), 152.2 (C-4a), 164.5 (C-15), 168.2 (C-11). IR (KBr): 1201, 1320, 1507, 1736, 1773, 3057 cm
0
0
0
−
1
.
+
HRMS-ESI (m/z): [M + Na] calc’d for C H N O Na, 573.164; found: 573.163.
32
20
2
7
(4E)-N-Hydroxy-2,3-dihydro-4H-chromen-4-imine (13): Hydroxylamine hydrochloride (2.81 g,
40.44 mmol) was added to the stirred solution of chroman-4-one (7a, 3.0 g, 20.25 mmol) in pyridine

Molecules 2020, 25, 1265
15 of 19
(
25 mL) and the mixture was stirred for 1.5 h. Cool water (100 mL) was added to the reaction mixture
and the aqueous phase was extracted with ethyl-acetate (3
×
50 mL). The combined organic layers
were dried over MgSO , filtered and concentrated under reduced pressure. The residue was purified
4
by column chromatography on silica gel (hexane/EtOAc 3:1) to give 13 as white solid (3.1 g, 94%, mp
◦
1
1
2
(
(
40–141 C). H NMR (360 MHz, CDCl ):
δ
= 3.01 (m, J = 6.1 Hz, 2 H, 3-H), 4.25 (m, J = 6.1 Hz, 2 H,
-H), 6.89–6.96 (m, 2 H, 6-H, 8-H), 7.25 (m, 1 H, 7-H), 7.81 (dd, J = 9.7 Hz and 1.8 Hz, 1 H, 5-H), 9.39
br s, 1 H, OH). 13C NMR (90 MHz, CDCl3):
= 23.5 (C-3), 64.9 (C-2), 117.8 (C-8), 118.1 (C-5a), 121.5
C-6), 123.9 (C-5), 131.2 (C-7), 149.9 (C-4), 156.7 (C-8a). IR (KBr): 1046, 1253, 1454, 1603, 3263 cm .
3
δ
−1
+
HRMS-ESI (m/z): [M + H] calc’d for C H NO H, 164.071; found: 164.071.
9
9
2
2
,3-Dihydro-1,5-benzoxazepin-4(5H)-one (15): The solution of 13 (1.0 g, 6.13 mmol) in dry
◦
dichloromethane (60 mL) was cooled to 5 C and added to DIBAL-H (40 mL, 1.0M in hexane)
under argon atmosphere and the mixture was stirred for 24 h. The reaction mixture was diluted with
ethyl-acetate (20 mL), and filtered through celite bench. The organic layer was dried over MgSO4,
filtered and concentrated under reduced pressure to afford 15 as brown solid (883 mg, 97%, mp 48–52
◦
1
C). H NMR (400 MHz, CDCl ):
δ
= 1.98 (m, J = 5.6 Hz, 2H, 3-H), 3.19 (m, J = 5.6 Hz, 2 H, 4-H), 3.57
br s, 1 H, -NH), 4.07 (m, J = 5.6 Hz, 2 H, 2-H), 6.73 (dd, J = 8.8 Hz and 1.2 Hz, 1 H, 6-H), 6.76 (m, 1
H, 7-H), 6.85 (m, 1 H, 8-H), 6.96 (dd, J = 9.2 Hz and 1.2 Hz, 1 H, 9-H). 13C NMR (100 MHz, CDCl3):
3
(
δ
= 31.9 (C-3), 45.9 (C-4), 71.4 (C-2), 119.5 (C-9), 120.7 (C-6), 121.8 (C-8), 123.3 (C-7), 142.0 (C-6a), 150.1
+
(C-9a). IR (KBr): 1053, 1250, 1595, 2952, 3282. HRMS-ESI (m/z): [M + Na] calc’d for C H NONa,
9
11
1
72.074; found: 172.074.
-(3,4-Dihydro-1,5-benzoxazepin-5(2H)-yl)benzaldehyde (
100 mg, 0.67 mmol) in dry 1,4-dioxane (4 mL), Pd(OAc) (11 mg, 0.05 mmol),
2
4): To the stirred solution of 15
(
2
2
0 0
-dicyclohexylphosphino-2 ,6 -dimetoxybiphenyl (28 mg, 0.07 mmol), Cs CO (328 mg, 1.00 mmol)
2 3
and 2-bromobenzaldehyde (0.12 mL, 1.00 mmol) were added and the mixture was refluxed for 18 h
under argon atmosphere. The reaction mixture was concentrated under reduced pressure and residue
was purified by column chromatography on silica gel (hexane/EtOAc 8:1) to give
(
4
as yellow solid
◦
97 mg, 87%, mp 89–92 C). H NMR (400 MHz, CDCl ): δ = 2.07 (m, J = 5.6 Hz, 2H, 3-H), 3.83 (m,
3
1
J = 5.6 Hz, 2 H, 4-H), 4.24 (m, J = 5.6 Hz, 2 H, 2-H), 6.52 (dd, J = 9.2 Hz and 1.2 Hz, 1 H, 9-H), 6.79 (m,
0
1
7
1
1
1
H, 7-H), 6.88 (m, 1 H, 8-H), 7.01 (dd, J = 9.2 Hz and 1.2 Hz, 1 H, 6-H), 7.17 (m, J = 7.2 Hz, 1 H, 4 -H),
0
0
0
.25 (d, J = 8.4 Hz, 1 H, 6 -H), 7.56 (m, 1 H, 5 -H), 7.81 (dd, J = 8.4 Hz and 1.2 Hz, 1 H, 3 -H), 10.14 (s,
H, -CHO). C NMR (100 MHz, CDCl ): δ = 29.9 (C-3), 52.6 (C-4), 70.1 (C-2), 121.9 (C-9), 123.4 (C-6),
23.5 (C-6 ), 123.6 (C-4 ), 124.0 (C-8), 124.7 (C-7), 129.1 (C-3 ), 129.9 (C-2 ), 134.8 (C-5 ), 142.6 (C-6a),
52.2 (C-9 ), 152.3 (C-1 ), 190.8 (CHO). IR (KBr): 1059, 1251, 1455, 1686. HRMS-ESI (m/z): [M + Na]
13
3
0
0
0
0
0
0
0
+
calc’d for C H NO Na, 276.100; found: 276.095.
16
15
2
[
2-(3,4-Dihydro-1,5-benzoxazepin-5(2H)-yl)benzylidene]propanedinitrile (20): To the stirred solution of
4
(100 mg, 0.39 mmol) in dry toluene (3 mL), dimethylamine-hydrochloride (128 mg, 1.58 mmol) and
malononitrile (156 mg, 2.37 mmol) were added and the mixture was stirred for 48 h. Water (10 mL) and
dichloromethane (20 mL) were added and two layers were separated. The aqueous phase was extracted
with dichloromethane (2
×
10 mL). The combined organic layers were washed with concentrated
NaHCO solution (3 10 mL), dried over MgSO , filtered and concentrated under reduced pressure.
×
3
4
◦
1
The product was isolated as red solid (115 mg, 3.38 mmol, 96%, mp 118–121 C). H NMR (400 MHz,
CDCl3):
δ
= 2.07 (m, 2 H, 3-H), 3.72 (m, 2 H, 4-H), 4.21 (m, 2 H, 2-H), 6.47 (d, J = 7.6 Hz, 1 H, 9-H), 6.87
0
0
(
m, 1 H, 7-H), 7.01 (m, 1H, 8-H), 7.09 (m, 1H, 6-H), 7.16 (m, 1 H, 4 -H), 7.31 (d, J = 7.6 Hz, 1 H, 6 -H),
0
0
13
7.57 (t, J = 7.6 Hz, 1 H, 5 -H), 7.82 (m, 2 H, 3 -H, 10-H). C NMR (90 MHz, CDCl ):
δ
= 30.3 (C-3), 51.7
3
0
0
(
C-4), 70.6 (C-2), 82.0 (C-11), 112.3 (-CN), 113.4 (-CN), 122.4 (C-9), 122.7 (C-6 ), 123.1 (C-6), 124.1 (C-4 ),
0
0
0
0
1
1
25.1 (C-8), 125.3 (C-7), 125.4 (C-2 ), 129.5 (C-5 ), 134.5 (C-3 ), 142.6 (C-6a), 151.0 (C-9a), 153.7 (C-1 ),
58.6 (C-10). IR (KBr): 1052, 1253, 1455, 2230.

Molecules 2020, 25, 1265
16 of 19
5
-(2,3-Dihydro-1H,8H-[1,4]oxazepino[2,3,4-de]acridin-8-yl)-1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)
trione ( ): To the solution of (100 mg, 0.40 mmol) in chloroform (6 mL), anhydrous MgSO (150 mg,
.25 mmol) and 1,3-dimethylbarbituric acid (370 mg, 2.42 mmol) were added and the mixture was
stirred for 10 days. The MgSO was filtered off and chloroform was removed under reduced pressure.
-
6
4
4
1
4
The residue was taken up in chloroform (30 mL) and extracted with concentrated NaHCO solution
3
(
3 × 10 mL), dried over MgSO , filtered and concentrated under reduced pressure. The resultant
4
1
product was isolated as purple solid (100 mg, 64%). H NMR (400 MHz, CDCl ):
δ = 2.26 (m, 1 H,
3
3
1
8
δ
-H
H, 2-H
a
), 2.36 (m, 1 H, 3-H ), 3.04 (s, 3 H, NMe), 3.10 (s, 3 H, NMe), 3.61 (d, J = 4.4 Hz, 1 H, 10-H), 3.93 (m,
b
a
), 4.10 (m, 2 H, 4-H), 4.38 (m, 1 H, 2-H ), 4.90 (d, J = 4.4 Hz, 1 H, 10-H), 6.90–6.96 (m, 6-H, 7-H,
b
13
-H, 11-H, 13-H, 5H), 7.03 (d, J = 6.8 Hz, 1 H, 9-H), 7.29 (m, 1 H, 12-H). C NMR (100 MHz, CDCl ):
= 27.7 (C-3), 28.0 (N-CH ), 28.2 (N-CH ), 47.4 (C-4), 49.5 (C-10), 59.0 (C-1 ), 70.4 (C-2), 112.3 (C-13),
3
0
3
3
1
1
20.4 (C-9a), 120.6 (C-6), 120.9 (C-8), 122.4 (C-11), 122.6 (C-12), 125.1 (C-10b), 128.1 (C-7), 129.2 (C-9),
34.5 (C-10a), 143.8 (C-13a), 149.2 (C-5a), 151.2 (C-4 ), 166.4 (C-6 ), 167.1 (C-2 ).
0
0
0
4
. Conclusions
N-aryl-1,4- and 1,5-benzoaxazepine derivatives were prepared with different substitution patterns
in short sequences and they were reacted with active methylene reagents to induce domino cyclization
reactions. The N-aryl-1,4-benzoaxazepines reacted with a Knoevenagel-[1,5]-hydride shift-cyclization
cascade providing condensed chiral O,N-heterocycles in regio- and diastereoselective manner.
Enantiomers of two products were separated by chiral HPLC, HPLC-ECD specra were recorded
and characteristic ECD transitions were correlated with the absolute configuration by TDDFT-ECD
calculations. The regioisomeric 1,5-benzoaxazepine derivative reacted with 1,3-dimethylbarbituric
2
acid in a domino Knoevenagel-C(sp )-H functionalization reaction resulting in a condensed acridane
derivative. Neuroprotective and AChE inhibitory activity of the products were tested. The condensed
1,4-benzoxazepine products did not have significant neuroprotective activity, which on the basis of
our previous results, suggested that lack of the C-2 phenyl group or replacement by naphthyl groups
resulted in the loss of activity. The condensed acridane derivative, containing a 1,5-benzoxazepine
moiety, was found to have AChE inhibitory activity with 6.98 × 10− mol/L IC50 value.
6
Supplementary Materials: The following are available online. Figure S1–S74: H and 13C NMR and IR spectra
1
of synthetic derivatives, Table S1: Organocatalytic transformations of 1a to trans-10a (columns A) and 1a to 11a
(columns B), Figure S75: Concentration-dependent curve of 6 for the inhibition of AChE activity.
Author Contributions: Investigation, D.S.V., L.T., B.B., Y.C.; synthesis and methodology, A.K.-S.; analytical
work, A.M.; software and ECD calculations, P.M., S.A., D.L.; writing—original draft preparation, L.T., H.Z.;
pharmacological investigation, T.K.; supervision and writing—review and editing. All authors have read and
agreed to the published version of the manuscript.
Funding: Financial support from the National Research Development and Innovation Office (Grant numbers:
K-112951, K-120181) is gratefully acknowledged. This research was supported by the EU and co-financed by the
European Regional Development Fund under the project GINOP-2.3.2-15-2016-00008. A.M. was supported by
the J
ános Bolyai Research Scholarship of the Hungarian Academy of Sciences and the ÚNKP-19-4 New National
Excellence Program of the Ministry for Innovation and Technology.
Acknowledgments: The Governmental Information-Technology Development Agency (KIFÜ) is acknowledged
for CPU time.
Conflicts of Interest: The authors declare no conflict of interest.
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