Bistricyclic aromatic enes annelated with nopinane fragment

Article abstract of DOI:10.1016/j.tet.2021.131979

Organic compounds, referred to as bistricyclic aromatic enes (BAE), are a subgroup among many sterically overcrowded alkenes and are widely studied as molecular switches. We have developed a new group of chiral BAE whose molecular structure combines dipinodiazafluorene fragment and chromophore/fluorophore (acridine, xanthene or thioxanthene moiety). The new compounds demonstrate mechanochromism, thermochromism, and solvatochromism/protonochromism. According to quantum chemical calculations (DFT PBE0/def2-TZVPP), the compounds synthesized are conformationally inhomogeneous, and the conformations should differ in the electronic absorption spectra, the population of conformational isomers should being dependent on the solvent and the acidity of the medium. The observed experimental facts (NMR data, UV spectra, chromism, X-ray data) are in good correlation with the calculated data.

Full text of DOI:10.1016/j.tet.2021.131979

Tetrahedron 83 (2021) 131979
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Bistricyclic aromatic enes annelated with nopinane fragment
,
*
Eugene S. Vasilyev a, Sergey N. Bizyaev a, Vladislav Yu Komarov b, Alexey V. Tkachev a
a N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Branch of Russian Academy of Sciences, 9 Academician Lavrentiev Ave., Novosibirsk,
630090, Russia
b Nikolaev Institute of Inorganic Chemistry, Siberian Branch of Russian Academy of Sciences, Novosibirsk, 630090, Russia
a r t i c l e i n f o
a b s t r a c t
Article history:
Organic compounds, referred to as bistricyclic aromatic enes (BAE), are a subgroup among many steri-
cally overcrowded alkenes and are widely studied as molecular switches. We have developed a new
group of chiral BAE whose molecular structure combines dipinodiazafluorene fragment and chromo-
phore/fluorophore (acridine, xanthene or thioxanthene moiety). The new compounds demonstrate
mechanochromism, thermochromism, and solvatochromism/protonochromism. According to quantum
chemical calculations (DFT PBE0/def2-TZVPP), the compounds synthesized are conformationally inho-
mogeneous, and the conformations should differ in the electronic absorption spectra, the population of
conformational isomers should being dependent on the solvent and the acidity of the medium. The
observed experimental facts (NMR data, UV spectra, chromism, X-ray data) are in good correlation with
the calculated data.
Received 26 August 2020
Received in revised form
18 January 2021
Accepted 23 January 2021
Available online 6 February 2021
Keywords:
Overcrowded alkenes
Nopinane-annelated pyridines
4,5-Diazafluorene
Mechanochromism
pH sensing
© 2021 Elsevier Ltd. All rights reserved.
1. Introduction
2. Results/discussion
We have recently shown that condensation of diazafluorene 1
with a number of aromatic ketones in the system TiCl4ePy leads to
tetra-substituted alkenes. The condensation product with anthra-
quinone showed solvatochromism and pleochroism, associated
with the existence of the sterically overcrowded alkene moiety in
various forms [1].
Inspired by the successful synthesis with anthraquinone [1], we
tried to conduct a condensation of dipinodiazafluorene 1 with
acridone
under
the
same
reaction
conditions
(TiCl4ePyeTHFeCCl4), nevertheless, we failed to isolate any
condensation product. However, condensation of diazafluorene 1
with 9-chloracridine resulted in product 2 (Scheme 1).
As can be seen from the literature, such compounds, referred to
as bistricyclic aromatic enes (BAE), are a subgroup among many
sterically overcrowded alkenes and are widely studied as molecular
switches. Molecular forms arising due to the impossibility of the
alkene fragment to be flat are often close in energy and depending
on the substituents and conditions, one form may be more stable
than the other, and at sufficiently high transition barriers, the forms
can be isolated in an individual state [2,3]. Design of chiral switches
in an enantiomerically pure form is of particular interest due to a
remarkable and unprecedented combination of switching proper-
ties including dynamic helicity, reversibility, selectivity, fatigue
resistance, and thermal stability [4,5].
Crystal structure of compound 2a was solved by X-ray analysis.
According to NMR data, the same substituted acridine structure is
predominate in solutions (CDCl3, DMSO‑d6), whereas in acidic
media the equilibrium is shifted towards protonated dihy-
droacridine form 2b (Scheme 1).
Condensation of dipinodiazafluorene 1 under the action of
TiCl4ePy was successful with xanthone and thioxantone. The cor-
responding condensation products 3 and 4 were prepared in 60 and
6% yields (Scheme 2).
The yield of the thioxantone derivative 4 was unacceptably low,
so we decided to try another method involving intermediate
diazocompound and episulfide (BartoneKellogg method [6]). We
generated in situ diazafluorene diazoderivative 5 [7], which was
then treated with a freshly prepared thioketone in the presence of
copper (I) iodide to produce episulfide 6, which was then reduced
with triphenylphosphine to afford the desired compounds 3 and 4.
The sequence of this type was previously used in the syntheses of
the simplest achiral xanthone derivatives [8,9] (Scheme 3).
* Corresponding author.
E-mail address: atkachev@nioch.nsc.ru (A.V. Tkachev).
https://doi.org/10.1016/j.tet.2021.131979
0040-4020/© 2021 Elsevier Ltd. All rights reserved.

E.S. Vasilyev, S.N. Bizyaev, V.Y. Komarov et al.
Tetrahedron 83 (2021) 131979
Scheme 1. Synthesis of acridine derivatives 2. The numbering of the carbons is given for NMR interpretation.
Ketazine 7 and ketone 8 are the main by-products of the
condensation. Azine 7 was previously described as the product of
condensation of ketone 8 with hydrazine [10], while dipinodiaza-
fluorenone 8 is known as the product of oxidation of compound 1
[11].
Scheme 2. Synthesis of xanthone and thioxantone derivatives. The numbering of the
carbons is given for NMR interpretation.
Scheme 3. Alternative synthesis of xanthone and thioxantone derivatives.
2

E.S. Vasilyev, S.N. Bizyaev, V.Y. Komarov et al.
Tetrahedron 83 (2021) 131979
frames C1,C2/C12 and C1a,C2a … C12a; 1,2-disubstituted benzene
rings C16,C17/C21 and C16a,C17a … C21a). Addition of trifluoro-
acetic acid leads to a simplification of the spectra due to the fact
that, in the protonated form, isomer 2a with the substituted acri-
dine moiety is unstable compared to the isomer 2b (see the
calculation section below). Fast (on the NMR time scale) exchange
involving diastereomeric twist forms as well as fast proton ex-
change lead to averaged spectrum having the single set of signals
(Fig. 2).
1H NMR spectra of both xanthene and thioxanthene derivatives
3 and 4 contain the single set of signals due to a fast exchange
probably due to degenerate butterfly type rearrangement of folded
conformations (Fig. 1). The exact mechanism of this kind of trans-
formation can be quite complex (see Ref. [12]).
Chemical structures of compounds 3 and 4 were proved by X-
ray crystallography (see below).
As for 13C NMR, the conformational exchange is not fast (in the
NMR time scale) for all signals. Thus, the signal intensity of aro-
matic carbons differs by an order of magnitude in the spectrum of
thioxanthone derivative 4, while not all signals of aromatic carbons
are visible in the spectrum of the xanthone derivative 3.
2.1. Spectra analysis
All the synthesized compounds are crystalline substances and
crystallize as solvates with solvents (CHCl3 or CH3CN), whose sig-
nals are always detected in NMR spectra. The solvates are unstable
at room temperature and are rapidly destroyed in air. For this
reason, it was not possible to obtain reproducible microanalysis and
melting point results. At the same time, the substances themselves
are quite stable and remain unchanged in the open air at room
temperature for several weeks. The substances are stable when
heated to a temperature of 230e290 ꢀC (differential scanning
calorimetry).
Chemical structures of new compounds were proved by spec-
troscopic data. In the electron impact ionization mass spectra of the
compounds synthesized, molecular ion is clearly visible, the exact
mass of which coincides (within the limits of acceptable deviations)
with the expected values.
2.2. X-ray study
Although compounds 2e4 are solid crystalline substances, it
was not an easy task to obtain crystals suitable for X-ray study. In
the end, for all the compounds we were able to obtain the suitable
crystals of solvates. Suitable crystals of compounds 2, 3, 4 and 9
were grown at recrystallization of the purified products from
appropriate solvent: CHCl3 (2), MeCN (3), and CHCl3 (4). Using
CHCl3eCH3CNeC6H6 mixed solvent we also managed to grow the
crystals of the condensation product with anthraquinone 9, which
was described earlier [1]. As it was mentioned above, the solvates
are unstable at room temperature and are rapidly destroyed in air.
According to X-ray data, all the molecules 2e4, 9 have a diaza-
fluorene structural unit that is more or less curved in crystal state.
In most cases, the pairs of molecules in the crystal are unfolded to
each other by the NN-sites of the diazafluorene units. All the
compounds in the crystal state are characterized by a very loose
packing with a significant amount of cavities that are either occu-
pied by solvent molecules or remain unoccupied or partially
occupied.
IR spectra of the new compounds contain all the characteristic
bands belong to the normal vibration modes of the functional
groups present:
n(CAreH), n(CAlkeH), n(C]N), n(C]C), and
d
(CAreH). There are two the most intensive bands in the spectra of
compounds 2e4. The first one is due to several specific skeletal
vibrational modes of the dipinodiazafluorene moiety, which merge
into one intensive asymmetric-shaped band at 1395e1399 cmꢁ1
.
This band is characteristic for dipinodiazafluorene derivatives
[10,11]. The second band at 740e760 cmꢁ1 arises due to out-of-
plane CeH bending vibrations 1,2-disubstituted benzene ring of
xanthon, thioxanthone and acridine fragments.
Compound 2 (Fig. 3) contains highly disordered solvate mole-
cules of CHCl3. The pairs of molecules are turned by NN-sites to
each other (NN…NN ~ 5.5 Å) with diazafluorene units lying almost
in the same plane, however, the cavities formed between the NN-
sites are sealed by benzene rings of the dihydroacridine fragment.
Each unit cell contains 3.8 CHCl3 molecules located in cavities with
an accessible volume of 1060.3 Å3 (29.4%) (based on the residual
electron density of 219.2 electrons per unit cell found in cavities
using the Olex2 solvent mask procedure).
The pairs of molecules 3 are turned by NN-sites to each other
(NN…NN ~ 5.3 Å) with diazafluorene units lying almost in the same
plane (Fig. 4). Cavities formed between the NN-sites of the diaza-
fluorene units are occupied by CH3CN molecules oriented by
methyl groups to the NN-sites due to dipole-dipole interaction. In
total, unit cell contains 16 positions of solvate molecules located in
Room temperature 1H NMR spectra of compounds 2e4 contain
narrow signals without signs of exchange. Analysis of high-field 2D
1He1H and 13Ce1H-correlation NMR spectra of the products
demonstrate that sets of proton and carbon chemical shifts and
proton-proton and carbon-proton spin-spin couplings for each
compound are similar to those of the previously reported struc-
turally relative dipinodiazafluorene derivatives [1,10,11]. Signals for
compounds 2a and 2b were assigned using calculated data (DFT).
However, some features in the spectra should be mentioned.
NMR spectra of the acridine derivative 2a contain 2 sets of
signals due to presence of pairs of diastereotopic fragments (pinane
Fig. 1. Degenerate butterfly type rearrangement of folded conformations of the xanthene and thioxanthene derivatives 3 and 4.
3

E.S. Vasilyev, S.N. Bizyaev, V.Y. Komarov et al.
Tetrahedron 83 (2021) 131979
Fig. 2. Room temperature (þ21 ꢀC) 1H NMR spectra of compound 2: set of signals and their chemical shifts in DMSO‑d6eCF3COOH correspond to the protonated form of the
acridone derivative 2a (top), while spectrum in DMSO‑d6 corresponds to the acridine derivative 2a (bottom).
cavities with an accessible volume of 873.8 Å3 (25.6%). The posi-
tions of solvate molecules outside the cavities between NN-sites of
the diazafluorene units either are partially occupied (s.o.f. 86%) or
have orientation disordering.
(19.5%) (Fig. 6). Some solvate molecules are oriented by the
hydrogen atom to the NN-sites of the diazafluorene units, the other
are disordered. All solvate molecule positions are partially
occupied.
The total volume of cavities in the unit cell of compound 4 is
321.7 Å3 (19.5% per unit cell), which is enough to 2 CHCl3 molecules
(Fig. 5). The solvate molecules are ordered and oriented by the
hydrogen atom to the NN-sites of the diazafluorene units.
Each unit cell of the compound 9 crystals contains 4.8 CHCl3
molecules located in cavities with an accessible volume of 926.5 Å3
2.3. Color change phenomena
All the compounds 2e4, 9 exhibit curious color properties. The
observed color changes are summarized in Table 1.
All the color change phenomena observed can be explained in
4

E.S. Vasilyev, S.N. Bizyaev, V.Y. Komarov et al.
Tetrahedron 83 (2021) 131979
Fig. 5. The molecular structure of 4 (Z’ ¼ 1). Non-H atoms are shown with ADP 50%
ellipsoids.
Fig. 3. The molecular structure of 2a (Z’ ¼ 2). Non-H atoms are shown with ADP 50%
ellipsoids.
Fig. 6. The molecular structure of 9 (Z’ ¼ 1). Non-H atoms are shown with ADP 50%
ellipsoids.
terms of conformational lability of the molecules.
According to quantum chemical calculations, for each substance
(compounds 2, 3, 4 and 9), there are several diastereomeric con-
formations that differ in the mutual orientation of the chromo-
phore fragments (Table 2). The conformations differ in the nature of
intramolecular conjugation of chromophore fragments and must
have different electronic absorption spectra. The population of
these conformations depends on the nature of the solvent and the
Fig. 4. The molecular structure of 3 (Z’ ¼ 2). Non-H atoms are shown with ADP 50%
ellipsoids.
5

Table 1
Color change phenomena.
Compound No.
Crystals
Mechanochromism
Thermochromism
Solvatochromism/Protonochromism
2
yellow crystals with slightly
greenish surface
yellow crystals become green
when grinding in a mortar
the yellow spot on a sorbent
(Al2O3, SiO2) turns blue when
heated, after cooling to room
temperature it gradually (in a
few minutes) turns yellow
again;
yellow solutions in CCl4, light
petroleum, colorless solution in
ethanol;
blue solution in AcOH or CF3COOH
becomes light yellow after addition of
Et3N;
yellow crystals become blue
when heated to 160 ꢀC
yellow crystals become red
when heated to 80 ꢀC
3
yellow crystals with slightly
brownish surface
yellow crystals become dark
purple when grinding in a
mortar, the crystals again turn
yellow in acetonitrile vapor
e
purple solutions in CHCl3 and DMSO;
blue solution in AcOH or CF3COOH
becomes light yellow after addition of
Et3N
yellowish solutions in any solvent
yellowish solutions in any solvent
purple solutions in CHCl3
4
9
10
yellow crystals
yellow crystals
dark yellow crystals
e
e
e
yellow crystals become dark
purple when grinding in a
mortar, the crystals again turn
yellow in acetonitrile vapor
yellow crystals become red
when heated to 120 ꢀC
Table 2
Energy differences and estimated populationsa of different form (conformations) of free amines and protonated forms of compounds 2, 3, 4 and 9.
acridine derivative 2
2a
2b (twist 1)
0.39
32.2
0.00
85.0
2b (twist 2)
1.55
4.4
1.01
15.0
2b (folded)
free amine
protonated
DDE(kcal/mol)
%
DDE(kcal/mol)
0.00
63.4
7.31
0
7.59
0.0
5.65
0
%
xanthene derivative 3
twist 1
0.00
75.6
0.00
73.0
twist 2
0.69
23.0
0.58
27.0
Folded
2.35
1.4
4.81
0.0
free amine
protonated
DDE(kcal/mol)
%
DDE(kcal/mol)
%
thioxanthene derivative 4
twist 1
8.43
0
3.97
0.1
Twist 2
7.15
0
3.69
0.2
Folded
0.00
100
0.00
99.7
free amine
protonated
DDE(kcal/mol)
%
DDE(kcal/mol)
%
2:1 condensation product with anthraquinone 9
twist 1
14.53
0
twist 2
12.98
0
twist 3
14.02
0
folded
0.00
100
free amine
DDE(kcal/mol)
%
a
At room temperature (293 K) according to DFT calculations for solutions in CHCl3 (free amines) and AcOH (protonated forms); PBE0/def2-TZVPP for 2, 3, and 4; PBE0/def2-
TZVP for 9.
6

E.S. Vasilyev, S.N. Bizyaev, V.Y. Komarov et al.
Tetrahedron 83 (2021) 131979
acidity of the medium.
In contrast to the research [13], the folded conformations are
less stable for both free and protonated forms of acridine and
xanthine derivatives 2 and 3. For the folded conformation, dihedral
angle (folding angle) between benzene rings is 135ꢀ for 2, 138ꢀ for
3, 139ꢀ for 4 and 124 for 9. Diazafluorene ring system in the folded
conformations is almost planar but slightly distorted towards anti-
folded form [12], (resembling an arc in the side view). In twisted
conformations of compound 9 diazafluorene moiety is planar,
whereas in twisted conformations of compounds 2e4 diaza-
fluorene moiety is slightly distorted towards zigzag (in the side
view). Linear tricyclic ring systems (acridane, xanthene, thio-
xanthene, and anthraquinone) is almost planar in most of all the
twisted form but it is slightly distorted towards propeller. Twist-1
conformation of thioxanthene-drivative 4 is an exception having
slightly folded thioxanthone moiety (the folding angle is about
169ꢀ). The dihedral angle between the propeller of the linear tri-
cyclic ring system and diazafluorene moiety is as follows: ꢁ42ꢀ (2b
twist-1), þ40ꢀ (2b twist-2), ꢁ42ꢀ (3 twist-1), þ42ꢀ (3 twist-
2), ꢁ38ꢀ (4 twist-1), þ40ꢀ (4 twist-2).
Calculated and experimental absorption spectra are given in
Figs. 7e10. The first 24 lowest energy electronic transitions were
calculated by TDDFT. To simplify the representation of the calcu-
lated results and for the convenience of comparing the calculated
and experimental data, the envelope of the spectrum simulated for
the width of the individual lines of 0.2 eV are drawn instead of
calculated wavelengths.
In crystal state, acridine derivative 2 exists as tautomer 2a
having no absorption bands above 380 nm according to quantum
chemical calculations (Fig. 7). Tautomer 2a is also the most stable
form in a solution (CCl4, CHCl3 and EtOH). As a result, crystals of
compound 2 and its solutions are yellow. Protonation leads to a
change in the relative stability of the forms, and the twist
Fig. 8. Experimental UVeVIS and calculated (DFT PBE0/def2-TZVPP) absorption
spectra of xanthene derivative 3.
Fig. 9. Experimental UVeVIS and calculated (DFT PBE0/def2-TZVPP) absorption
spectra of thioxanthene derivative 4.
conformations become the most stable forms, in the spectra of
which an intense absorption band at 620 nm should appear.
Fig. 7. Experimental UVeVIS and calculated (DFT PBE0/def2-TZVPP) absorption
spectra of acridine derivative 2.
7

E.S. Vasilyev, S.N. Bizyaev, V.Y. Komarov et al.
Tetrahedron 83 (2021) 131979
Fig. 11. Highest occupied molecular orbitals (HOMO) for the twisted conformation or
the type “twist 1” for xanthene derivative 3 (top) and thioxanthone derivative 4 ac-
cording to quantum chemical calculations (DFT PBE0/def2-TZVPP).
Fig. 10. Experimental UVeVIS and calculated (DFT PBE0/def2-TZVP) absorption
spectra of a 2:1 condensation product with anthraquinone 9.
conformation as a solvate, which loses the solvent upon grinding,
turning into a colored form, which decolours when kept in aceto-
nitrile vapor.
Experimental spectrum of compound 2a in AcOH is characterized
by intense band at 640 nm, which is in good agreement with the
calculated spectrum of the protonated twist-form of the acridone
derivative 2b. Heating of the yellow TLC spot of compound 2 can
lead to a simple increase in the population of the “colored” twisted
forms, resulting in a blue color that fades when cooled.
Xanthene derivative 3 crystallizes in the folded conformation.
According to the calculations, this form has no absorption bands
above 380 nm (Fig. 8). Twist forms are more stable in solution
compared to the folded form. The twist forms have intense ab-
sorption bands around 530e540 nm providing purple color of a
solution. Protonation of the twist forms results in bathochromic
shift (Dl ~60 nm), so solution of compound 3 in acetic acid has
intense blue color. Grinding of the yellow crystals of compound 3
(solvate with CH3CN) results in destruction of the packaging, leads
to solvent volatilization due to heating because of friction and
transformation of the folded conformation to more stable twist
forms that are responsible for the appearance of dark purple color.
Keeping the colored milled material in acetonitrile vapor leads to
the restoration of the crystal structure of the solvate.
In spite of minor differences in the molecules, xanthene and
thioxanthene derivatives 3 and 4 do have different color properties
(Table 1). The difference can be explained by the calculation results.
But the difference in the calculation results for 3 and 4 has no
simple explanation. Obviously, the difference arises from the
“simple” substitution of O by S. Due to differences between O and S
atoms, corresponding 6-membered heterocyclic systems differ in
geometry (bond lengths and intracyclic bond angles) affecting the
geometry and electronic structure of the whole molecule. As an
illustration, configuration of highest occupied molecular orbitals
(HOMO) depicted in Fig. 11 demonstrate these differences. For the
twisted conformation or the type “twist 1” HOMO is localized
mainly on the central C]C bond in case of xanthene derivative 3, in
thioxanthone derivative 4 HOMO is localized to a large extent on
the heteroatom (S).
3. Conclusions
Thus, the observed experimental facts (NMR data, UV spectra,
chromism, X-ray data) are in good correlation with the calculated
data. Two new compounds can be used as potential chiral molec-
ular switches and indicators because the distribution of tautomers
and conformational isomers dramatically depends on experimental
conditions (pH, solvent, crystallinity). Although chiral pinane
fragments are formally located in space far from the chromophore/
fluorophore (acridine, xanthene or thioxanthene moiety), never-
theless they have a noticeable asymmetric effect on the ratio of
diastereomeric forms of different helicity.
In contrast with acridine and xanthene derivatives 2 and 3
respectively, thioxanthene derivative 4 is always yellow (as crystals,
in a solution, in a protonated form, when grinding in a mortar).
These observations are in agreement with the calculated data
(Fig. 9). Thioxanthene derivative 4 is crystallized in the folded
conformation with no absorption above 400 nm. The “colored”
twisted conformations are significantly less stable both for free
amine and its protonated form.
Similar situation is realized in the case of a 2:1 condensation
product with anthraquinone 9: the folded conformation is much
more stable than the twist forms, so compound 9 remains yellow
under any conditions (as crystals, in a solution, in a protonated
form, when grinding in a mortar).
4. Experimental section
4.1. General information
A 1:1 condensation product with anthraquinone 10 behaves the
same as acridine and xanthone derivatives 2 and 3 respectively [1]:
more stable folded conformation and less stable “colored” twist
forms (Fig. 10). Compound 10 crystallizes in the “colorless” folded
All the organic solvents used were freshly distilled. Merck silica
gel 60 (0.063e0.100 mm) was used for preparative column chro-
matography. Analytical TLC was carried out on a ready-to-use
plates (SiO2 on Al foil, visualization by spraying with a solution of
8

E.S. Vasilyev, S.N. Bizyaev, V.Y. Komarov et al.
Tetrahedron 83 (2021) 131979
FeCl3 ꢂ 6H2O or under UV light (254 nm)).
diazabicyclo[5.4.0]undec-7-ene (DBU, Alfa Aesar, 99%), copper (I)
iodide (pure, ReaChim), titanium tetrachloride (extra pure,
ReaChim), boron trifluoride diethyl etherate (pure, ReaChim), thi-
onyl chloride (pure, ReaChim), phosphorus pentasulphide (pure,
ReaChim).
Thioxanthione and thioxanthone were prepared by treatment of
xanthone and thoixanthone respectively with phosphorus penta-
sulphide according to the published procedure [28]. 9-
Chloroacridine was prepared as described in the literature [29].
Compound 9 was prepared as previously described [1]. The
NMR spectra were recorded at 20e23 ꢀC for solutions (c
20e40 mg/mL) on a DRX-500, Avance 400 or Avance 300 spec-
trometer (Bruker Corporation, Billerica, MA, USA) locked to the
deuterium resonance of the solvent. The chemical shifts were
calculated relative to the solvent signals used as the internal stan-
dard: dC 76.90 ppm and dH 7.24 ppm for CDCl3; dC 39.50 ppm and dH
2.50 ppm for DMSO‑d6.
IR spectra were recorded on a Bruker TENSOR 27 spectropho-
tometer in KBr. UV-spectra were recorded on an 8453 instrument
(Agilent Technologies, Inc., Santa Clara, CA, USA). Optical rotation
was measured on a PolAAr 3005 polarimeter (Optical Activity Ltd,
Ramsey, Cambridgeshire, United Kingdom). Thermal stability was
studies by differential scanning calorimetry using a NETZSCH STA
409 instrument. Mass spectra were obtained on a Thermo Electron
DFS (electron impact ionization, EI, 70 eV), mass spectrometer
(Thermo Electron GmbH, Bremen, Germany). Excitation and lumi-
nescence spectra for chloroform solutions were detected using a
Cary Eclipse spectrofluorimeter (Varian Australia Pty Ltd, Mulgrave,
Victoria, Australia) at room temperature with averaging time of
0.1e0.5 s.
purified
product
was
crystallized
from
a
mixture
CHCl3eMeCNeC6H6 to give single crystals of a solvate with CHCl3
suitable for X-ray diffraction. Compound 10 was characterized
earlier [1].
4.2. (1R,3R,8R,10R)-12-(acridin-9-yl)-2,2,9,9-tetramethyl-
2,3,4,7,8,9,10,12-octahydro-1H-1,3:8,10-dimethanocyclopenta[1,2-
b:5,4-b’]diquinoline (2a)
Sodium hydride (60% suspension in oil, 0.0500 g, 1.25 mol) and
9-chloroacridine (0.220 g, 1.03 mol) were added to a solution of
diazafluorene 1 (0.356 g, 1.00 mol) in THF (5 mL), and the mixture
was stirred at r.t. Under argon for 24 h. The solvent was removed
under reduced pressure; the residue (green oil) was chromato-
graphed on a silica gel column. Elution with a mixture of
C6H6eCHCl3eTHF (50:3:1) followed by recrystallization from light
petroleum afforded the title compound (270 mg, 50% yield).
Yellow crystals with slightly greenish surface; TLC Rf ¼ 0.30
The unit cell parameters and experimental diffraction in-
tensities were measured with a Bruker Apex Duo four-circle
diffractometer with a 2-coordinate CCD detector using graphite
monochromated MoKa radiation at 220 K (compound 2) and 150 K
(compounds 3,4 and 9) (N2-flow cryostat). Experimental data
reduction was conducted routinely via APEX2 suite [14]. The
structures were solved by SHELXT [15] and refined by full-matrix
least-squares method against all F2 using the SHELXL [16] assisted
with Olex2 GUI [17].
Atomic displacement parameters of non-H atoms were refined
in anisotropic approximation. Geometric (SADI, DFIX) and ADP
(EADP, RIGU) restraints were used for refinement of disorder sol-
vent in 3 and 9. Positions of hydrogen atoms were determined
geometrically and refined in a rider model. Crystallographic data
and the description of the data collection are reported in Table 1 of
the file with Supporting Information; the structure of the principal
molecules and atom labeling are shown at Figs. 3e6. The CIFs with
an entire XRD information was deposited as CCDC 220 K 2003438
(2), 2003439 (3), 2003440 (4), 2003441 (9) and can be obtained
free of charge from The Cambridge Crystallographic Data Centre via
https://www.ccdc.cam.ac.uk/structures/.
Molecular modeling and spectra data calculations were carried
at the DFT level using ORCA program system [18] (ver. 4.1.0). Hybrid
exchange-correlation functional PBE0 was chosen because it
worked well in the calculations of heteroatomic derivatives of
terpenes [19,20]. The doubly polarized triple-zeta basis sets with
new polarization functions def2-TZVP or def2-TZVPP [21] and the
auxiliary basis def2/J [22] utilizing the atom-pairwise dispersion
correction with the Becke-Johnson damping scheme (D3BJ) [23,24]
were used. To speed up the calculations, the RIJCOSX approxima-
tion was applied [25]. Electronic absorption spectra in the visible
and near ultraviolet regions were estimated at the TD-DFT level of
theory (PBE0/def2-TZVPP, D3BJ, RIJCOSX, def2/J). NMR chemical
shifts calculations were carried out using the auxiliary basis def2/JK
[26] (PBE0/def2-TZVPP D3BJ). Solvation effects were calculated
using SMD model [27].
(CHCl3); ½a 2D5
ꢃ
ꢁ118 (c 0.61,CHCl3); m.p. 294 ꢀC (decomp.); 1H NMR
(400 MHz, CDCl3): d 0.52 (s, 3H, H8 or H8a), 0.66 (s, 3H, H8a or H8),
1.16 (ddd, 1H, J ¼ 9.2, 5.2 and 5.2 Hz, pro-R-H7a), 1.26 (s, 3H, H9 or
H9a), 1.28 (d, 1H, J ¼ 9.4 Hz, pro-R-H7), 1.31 (s, 3H, H9a or H9), 2.35
(m, 2H, H5, H5a), 2.52 (m, 2H, J ¼ 6.1 Hz, pro-S-H7, pro-S-H7a), 2.53
(dd, 1H, J ¼ 5.4, 5.4 Hz, H1 or H1a), 2.63 (dd, 1H, J ¼ 5.8, 5.8 Hz, H1a
or H1), 3.32 (d, 2H, J ¼ 2.5 Hz, H4 or H4a), 3.35 (d, 2H, J ¼ 2.5 Hz, H4a
or H4), 6.31 (s, 1H, H14), 6.73 (ddd, 1H, J ¼ 9.1, 1.4 and 0.7 Hz, H17 or
H17a), 6.86 (ddd, 1H, J ¼ 9.1, 6.5, 1.3 Hz, H18 or H18a), 6.90 (br, 2H,
H10 and H10a), 7.51 (ddd, 1H, J ¼ 8.8, 6.5, 1.4 Hz, H19 or H19a), 7.68
(ddd, 1H, J ¼ 8.9, 6.6, 1.4 Hz, H19a or H19), 7.86 (ddd, 1H, J ¼ 8.8, 6.6,
1.2 Hz, H18a or H18), 8.13 (d, 1H, J ¼ 8.7 Hz, H20 or H20a), 8.33 (dd,
1H, J ¼ 8.8,1.1 Hz, H17a or H17), 8.66 (d, 1H, J ¼ 8.8 Hz, H20a or H20)
ppm; 13C{1H} NMR (100 MHz, CDCl3):
d 20.82 (С8 or C8a), 21.18
(С8a or C8), 25.78 (С9 or C9a), 25.87 (С9a or C9), 31.78 (C7 or C7a),
31.82 (C7a or C7), 36.65 (C4 or C4a), 36.71 (C4a or C4), 39.30 (C6 or
C6a), 39.42 (C6a or C6), 39.83 (C5 or C5a), 39.99 (C5a or C5), 43.57
(C14), 46.86 (C1, C1a), 123.34 (C17 or C17a), 123.94 (C16 or C16a),
125.25 (C18 or C18a), 125.38 (C18a or C18), 126.67 (C17a or C17),
126.99 (C16a or C16), 129.03 (C19 or C19a), 129.22 (C19a or C19),
129.68 (C10, C10a), 130.03 (C20 or C20a), 130.83 (C20a or C20),
139.05 (C11 or C11a), 139.48 (C11a or C11), 141.44 (C21 or C21a),
141.52 (C21a or C21),141.75 (C15),148.68 (C2 or C2a),148.80 (C2a or
C2), 155.06 (C12 or C12a), 155.15 (C12a or C12), 157.79 (C3 or C3a),
157.87 (C3a or C3) ppm; UV (c 1.1 ꢂ 10ꢁ4 M, CСl4) lmax (log ε): 483
(2.65), 386 (3.83), 370 sh (4.06), 364 (4.11), 334 (4.48), 255 (4.90)
nm; UV (c 1.1 ꢂ 10ꢁ3 M, CHСl3) lmax (log ε): 517 (1.3), 389 (3.69),
363 (3.89), 338 (4.27) nm; UV (с 1.0 ꢂ 10ꢁ4 M, toluene) lmax (log ε):
516 (2.06), 387 (3.77), 363 (3.96), 334 (4.43) nm; UV (с
9.9 ꢂ 10ꢁ5 M, EtOH) lmax (log ε): 388 (3.73), 370 sh (3.89), 361
(3.99), 337 (4.50), 330 sh (4.45), 325 sh (440), 280 sh (4.02), 253
(5.07), 204 (4.69) nm; UV (c 1.0 ꢂ 10ꢁ4 M, AcOH) lmax (log ε): 640
(4.16), 590 sh (4.10), 398 (3.93), 360 (4.63), 280 (4.23), 255 (5.01)
nm; IR (KBr) nmax: 3064 and 3044 (weak) (CAreH), 2972, 2923 and
2869 (very strong) (CAlkeH), 1395 (strong), 750 (very strong) (CAreH)
cmꢁ1; HREIMS: m/z 533.2822 (calcd for C38 H35 Nþ3 ., 533.2826).
Chiral nopinane-annelated diazofluorene 1 was prepared from
(1S)-(ꢁ)-
a-pinene (ACROS ORGANICS, 98%) via pinocarvone oxime
as described earlier [11].
The following commercially available reagents were used
without any purification: xanthone (Vekton, pure, TU MChP
3447e53), thioxanthone (TCI, >98%, T2351, lot. 72XVA-QP), o-
dichlorobenzene (ACROS ORGANICS, 99%), sodium hydride 60%
dispersion in mineral oil, in soluble bags (ACROS ORGANICS), 1,8-
9

E.S. Vasilyev, S.N. Bizyaev, V.Y. Komarov et al.
Tetrahedron 83 (2021) 131979
The purified product was crystallized from CHCl3 to give single
benzene. Subsequent elution with THF resulted in a solution of the
reaction products, which was concentrated in vacuo. The residue
was extracted with light petroleum (4 ꢂ 20 mL), the combined
extract was chromatographed on a silica gel column (C6H6eEt2O) to
afford the title compound as blue oil which was treated with
acetonitrile to give yellow solid (285 mg, 53% yield).
crystals of a solvate suitable for X-ray diffraction.
1H NMR (400 MHz, DMSO‑d6):
d 0.48 and (s, 3H, H8 or H8a), 0.63
(s, 3H, H8a or H8), 1.04 (d, 1H, J ¼ 9.2 Hz, pro-R-H7 or pro-R-H7a),
1.20 (d, 1H, J ¼ 9.4 Hz, pro-R-H7a or pro-R-H7), 1.25 (s, 3H, H9 or
H9a), 1.30 (s, 3H, H9a or H9), 2.32 (dddd, J ¼ 6.0, 6.0, 3.0 and 3.0 Hz,
1H, H5 or H5a), 2.34 (dddd, J ¼ 6.0, 6.0, 3.0 and 3.0 Hz, 1H, H5a or
H5), 2.54 (ddd, 1H, J ¼ 9.7, 5.6 and 5.6 Hz, pro-S-H7 or pro-S-
H7a),2.64 (ddd, 1H, J ¼ 9.7, 5.6 and 5.6 Hz, pro-S-H7a or pro-S-H7),
2.63 (dd, 1H, J ¼ 5.7 and 5.7 Hz, H1 or H1a), 2.64 (dd, 1H, J ¼ 5.7 and
5.7 Hz, H1a or H1), 3.12e3.23 (m, 2H, H4 or H4a), 3.36 (s, 2H, H4a or
H4), 6.70 (s,1H, H14), 6.58 (d,1H, J ¼ 8.9 Hz, H17 or H17a), 6.99 (ddd,
1H, J ¼ 9.0, 6.5 and 1.1 Hz, H18 or H18a), 7.02 and 7.05 (br.s, 2H, H10
and H10a), 7.58 (ddd, 1H, J ¼ 8.7, 6.6 and 1.2 Hz, H19 or H19a), 7.76
(ddd, 1H, J ¼ 8.9, 6.5 and 1.1 Hz, H19a or H19), 7.95 (ddd, 1H, J ¼ 9.0,
6.5 and 0.7 Hz, H18a or H18), 8.09 (d, 1H, J ¼ 8.7 Hz, H20 or H20a),
8.27 (dd, 1H, J ¼ 8.8 and 0.7 Hz, H17a or H17), 9.04 (d, 1H, J ¼ 9.0 Hz,
H20a or H20) ppm;
4.4.2. Method B (for xanthone and thioxanthone derivatives)
Tosyl azide (0.300 g, 1.52 mmol) and DBU (0.182 g, 1.20 mmol)
where added to a solution of diazafluorene 1 (0.356 g,1.00 mmol) in
THF (4 mL) at room temperature immediately followed by addition
of CuI (20 mg, 0.1 mmol) and 9H-xanthene-9-thione (0.250 g,
1.18 mmol) or 9H-thioxanthene-9-thione (0.250 g, 1.10 mmol). The
mixture was stirred 6 h followed by addition of Ph3P (0.79 g,
35 mmol) and o-xylene (4 mL). The stirring mixture was slowly
heated to 100ꢀС to let the low-boiling solvent (THF) to evaporate
and then kept at 140ꢀС for 30 h at vigorous stirring. The mixture
was cooled down to room temperature and poured into a silica gel
column, and o-xylene was removed by elution with benzene.
Subsequent elution with THF resulted in a solution of the reaction
products, which was concentrated in vacuo. The residue was
extracted with light petroleum (4 ꢂ 20 mL), the combined extract
was chromatographed on a silica gel column (C6H6eEt2O) to afford
the title compound as blue oil which was treated with acetonitrile
to give yellow solid (208 mg, 33% yield of 3 or 212 mg, 35% yield of
4).
13C{1H} NMR (100 MHz, DMSO‑d6):
d 20.73 (С8 or C8a), 21.18
(С8a or C8), 25.59 (С9 or C9a), 25.70 (С9a or C9), 31.51C7 or C7a),
31.55 (C7a or C7), 36.28 (C4 or C4a), 36.36 (C4a or C4), 38.89 (C6 or
C6a), 38.98 (C6a or C6), 39.40 (C5 or C5a), 39.55 (C5a or C5), 43.15
(C14), 46.86 (C1, C1a), 124.48 (C17 or C17a), 123.45 (C16 or C16a),
124.96 (C18 or C18a), 125.26 (C18a or C18), 126.95 (C17a or C17),
127.12 (C16a or C16), 128.84 (C19 or C19a), 129.17 (C19a or C19),
129.69 (C10 or C10a), 130.16 (C10a or C10), 130.21 (C20 or C20a),
130.37 (C20a or C20), 140.05 (C11 or C11a), 140.53 (C11a or C11),
140.83 (C21 or C21a), 140.91 (C21a or C21), 142.17 (C15), 148.30 (C2
or C2a), 148.60 (C2a or C2), 154.78 (C12 or C12a), 154.82 (C12a or
C12), 156.35 (C3 or C3a), 156.43 (C3a or C3) ppm;
4.5. (1R,3R,8R,10R)-2,2,9,9-tetramethyl-12-(9H-xanthen-9-
ylidene)-2,3,4,7,8,9,10,12-octahydro-1H-1,3:8,10-
dimethanocyclopenta[1,2-b:5,4-b’]diquinoline (3)
4.3. (1R,3R,8R,10R)-12-(acridin-9(10H)-ylidene)-2,2,9,9-
tetramethyl-2,3,4,7,8,9,10,12-octahydro-1H-1,3:8,10-
dimethanocyclopenta[1,2-b:5,4-b’]diquinoline (2b)
Yellow crystals with slightly brownish surface, solvate with
CH3CN; TLC Rf ¼ 0.40 (CHCl3); ½a D
of a solution; m.p. 233 ꢀC (decomp.); 1H NMR (400 MHz, CDCl3):
0.64 (s, 3H, H8), 1.27 (d, 1H, J ¼ 9.6 Hz, pro-R-H7), 1.35 (s, 3H, H9),
ꢃ
25 is unavailable due to deep color
d
1H NMR (400 MHz, DMSO‑d6eCF3COOH 10:1 v/v):
d 0.63 (s, 3H,
1.96 (s, 3H, CH3CN), 2.34 (dddd, J ¼ 5.9, 5.9, 2.8 and 2.8 Hz, 1H, H5),
2.57 (dd, 1H, J ¼ 5.9, 5.9 Hz, H1), 2.64 (ddd, 1H, J ¼ 9.6, 5.9, 5.9 Hz,
pro-S-H7), 3.28 (s, 2H, H4), 3.96 (s, 0.2H, H2O), 7.15 (ddd, 1H, J ¼ 7.9,
7.5 and 1.4 Hz, H18), 7.34 (dd, 1H, J ¼ 8.3 and 1.1 Hz, H20), 7.38 (ddd,
1H, J ¼ 8.3, 7.5 and 1.4 Hz, H19), 7.64 (s, 1H, H10), 7.91 (dd, 1H, J ¼ 7.9
H8), 1.357 (d, 1H, J ¼ 9.9 Hz, pro-R-H7), 1.359 (s, 3H, H9), 2.44 (dddd,
2H, J ¼ 5.8, 5.8, 3.1 and 2.2 Hz, H5), 2.77 (ddd, 1H, J ¼ 9.9, 5.8 and
5.8 Hz, pro-S-H7), 2.87 (dd, 1H, J ¼ 5.8, 5.8 Hz, H1), 3.41 (dd, 1H,
J ¼ 18.7 and 2.2 Hz, H4a), 3.51 (dd, 1H, J ¼ 18.7 and 3.1 Hz, H4a), 7.54
(ddd, 1H, J ¼ 8.8, 6.9 and 1.0 Hz, H18), 7.87 (s, 1H, H10), 8.06 (m, 2H,
H17 and H19), 8.17 (d, 1H, J ¼ 8.6 Hz, H20) ppm;
and 1.4 Hz, H17) ppm; 13C{1H} NMR (100 MHz, CDCl3):
d 1.67
(CH3CN), 21.20 (С8), 25.92 (C9), 32.10 (C7), 36.55 (C7), 39.55 (C6),
13C{1H} NMR (100 MHz, DMSO‑d6eCF3COOH 10:1 v/v):
d 21.15
40.02 (C5), 47.24 (C1), 116.12 (CH3CN), 117.50 (C20), 122.60 (C18),
124.68 (C14), 128.61 (C19), 129.41 (С10), 130.00 (C17), 130.48 (С16),
139.54 (С2), 154.42 (C12), 157.14 (C3) ppm; UV (c 9.9 ꢂ 10ꢁ4 M,
CHСl3) lmax (log ε): 521 (3.58), 364 (4.26), 340 (4.42), 291 (4.12),
245 (4.60), 243 (4.60), 235 (4.35) nm; UV (c 1.0 ꢂ 10ꢁ4 M, AcOH)
lmax (log ε): 583 (4.14), 368 (4.28), 325 (4.32), 270 (4.30), 249 (4.52)
nm; IR (KBr) nmax: 3066 (weak) (CAreH), 2979, 2917, 2868 and 2834
(very strong) (CAlkeH), 1399 (very strong), 750 (strong) (CAreH)
cmꢁ1; HREIMS: m/z 534.2662 (calcd for C38 H34 N2 Oþ1. 534.2666).
(C8), 25.60 (С9), 31.92 (C7), 32.83 (C4), 38.93 (C5), 39.78 (C6), 46.36
(C1), 115.24 (q, JC-F ¼ 289 Hz, CF3COOH), 119.75 (C20), 123.84 (C14),
125.81 (C18), 126.72 (C16), 129.28 (С10), 130.73 (C19), 130.94 (C11),
135.50 (C17), 139.34e139.37 (C2, C15, C21), 139.37 (C15 or C2),
145.16 (C12), 153.33 (C3), 158.55 (q, JC-F ¼ 38 Hz, CF3COOH) ppm.
4.4. Syntheses of xanthone and thioxanthone derivatives 3 and 4
1H NMR (300 MHz, DMSO‑d6eCF3COOH 10:1 v/v):
d 0.63 (s, 3H,
4.4.1. Method A (for xanthone derivative)
TiCl4 (0.76 g, 40 mmol) was added to a solution of xanthone
(0.400 g, 2.04 mmol) in o-dichlorobenzene (4 mL), and the mixture
was stirred at r.t. For 2 h under argon atmosphere followed by
consequent addition of a solution of diazafluorene 1 (0.356 g,
H8), 1.30 (d, 1H, J ¼ 9.7 Hz, pro-R-H7), 1.37 (s, 3H, H9), 2.06 (s, 3H,
CH3CN), 2.40 (dddd, J ¼ 5.8, 5.8, 2.8 and 2.3 Hz, 1H, H5), 2.74 (ddd,
1H, J ¼ 9.7, 5.6, 5.6 Hz, pro-S-H7), 2.81 (dd, 1H, J ¼ 5.6, 5.6 Hz, H1),
3.25 (dd, 1H, J ¼ 18.8, 2.3 Hz, H40) 3.35 (dd, 1H, J ¼ 18.8, 2.8 Hz, H400),
7.33 (ddd, 1H, J ¼ 8.1, 7.0 and 1.4 Hz, H18), 7.62 (dd, 1H, J ¼ 8.4 and
1.3 Hz, H20), 7.71 (ddd, 1H, J ¼ 8.3, 7.0 and 1.5 Hz, H19), 8.00 (s, 1H,
H10), 8.04 (dd, 1H, J ¼ 8.2 and 1.4 Hz, H17) ppm;
1.00 mmol) in o-dichlorobenzene (4 mL) and BF3 ꢂ Et2O (140
0.157 g, 1.10 mmol). The reaction mixture was stirred for 30 min
followed by addition of pyridine (100 L, 0.0981 g,1.24 mmol). After
30 min of stirring, one more portion of pyridine was added (100 L,
0.0981 g, 1.24 mmol). After 1 h of stirring, another portion of pyr-
idine was added (100 L, 0.0981 g, 1.24 mmol), and the mixture was
mL,
m
m
13C{1H} NMR (75 MHz, DMSO‑d6eCF3COOH 10:1 v/v):
d 1.20
(CH3CN), 21.10 (С8), 25.53 (C9), 31.50 (C7), 34.34 (C7), 39.01 (C5),
39.39 (C6), 46.39 (C1), 115.24 (q, JC-F ¼ 289 Hz, CF3COOH), 118.25
(CH3CN), 118.39 (C20), 121.72 (C14), 124.52 (C18), 130.88 (С10),
m
finally stirred for 48 h. The mixture was poured into a silica gel
column, and o-dichlorobenzene was removed by elution with
10

E.S. Vasilyev, S.N. Bizyaev, V.Y. Komarov et al.
Tetrahedron 83 (2021) 131979
131.08 (C19), 132.87 (С16), 133.76 (C17), 141.18 (C15), 142.40 (C11),
144.54 (С2), 152.91 (C21), 152.98 (C3 and C12), 158.55 (q, JC-
118020290186-8, A.V.Tkachev). The research described was sup-
ported in part by the Russian Science Foundation (RSF), Grant 18-
73-00148 (mol). The authors would like to acknowledge the Multi-
Access Chemical Research Centre SB RAS for spectral and analytical
measurements and the Information Technology Centre of the
Novosibirsk State University for providing access to the cluster
computational resources to carry out quantum-chemical
calculations.
¼ 38 Hz, CF3COOH) ppm.
F
4.6. (1R,3R,8R,10R)-2,2,9,9-tetramethyl-12-(9H-thioxanthen-9-
ylidene)-2,3,4,7,8,9,10,12-octahydro-1H-1,3:8,10-
dimethanocyclopenta[1,2-b:5,4-b’]diquinoline (4)
Yellow crystals, solvate with CH3CN; TLC Rf ¼ 0.40 (CHCl3);
½
a 2D5
ꢃ
ꢁ18 (c 0.088, CHCl3); m.p. 265 ꢀC (decomp.); 1H NMR
References
(400 MHz, CDCl3):
d
0.62 (s, 3H, H8), 1.22 (d, 1H, J ¼ 9.7 Hz, pro-R-
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H7), 1.34 (s, 3H, H9), 1.56 (s, 1.6H, H2O), 1.99 (s, 0.29H, CH3CN), 2.31
(dddd, 2H, J ¼ 5.8, 5.8, 2.8 and 2.8 Hz, H5), 2.45 (dd, 1H, J ¼ 5.8 and
5.8 Hz, H1), 2.61 (ddd, 1H, J ¼ 9.7, 5.8 and 5.8 Hz, pro-S-H7), 3.23 (d,
2H, J ¼ 2.8 Hz, H4), 7.15 (s, 1H, H10), 7.33 (m, 2H, H18 and H19), 7.69
(m, 1H, H20), 7.77 (m, 1H, H17) ppm; 13C{1H} NMR (100 MHz,
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CDCl3):
d 21.22 (С8), 25.94 (C9), 32.09 (C7), 36.63 (C4), 39.48 (C6),
39.96 (C5), 47.18 (C1), 125.80 (C20), 127.28 (C14 or C15), 127.60
(C17), 128.41 (C18), 129.02 (C19), 129.28 (С10), 129.55 (C15 or C14),
136.15 (C16 or C21), 136.48 (C21 or C16), 138.52 (11), 139.62 (С2),
155.99 (C12), 157.97 (C3) ppm; UV (c 1.02 ꢂ 10ꢁ4 M, CHСl3) lmax
(log ε): 361 (4.02), 339 (4.42), 333 (4.42), 325 (4.41), 241 (4.55) nm;
UV (c 1.04 ꢂ 10ꢁ4 M, CH3COOH) lmax (log ε): 410 sh (3.51), 365
(4.05), 344 (4.08), 265 sh (4.03) nm; IR (KBr) nmax: 3066 and 3055
(weak) (CAreH), 2964, 291 and 2866 (very strong) (CAlkeH), 1398
(very strong), 742 (very strong) (CAreH) cmꢁ1; HREIMS: m/z
550.2440 (calcd for C38 H34 N322S1þ. 550.2437).
The purified product was crystallized from CHCl3 to give single
crystals of a solvate suitable for X-ray diffraction.
5. Supporting information summary
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Declaration of competing interest
The authors declare that they have no known competing
financial interests or personal relationships that could have
appeared to influence the work reported in this paper.
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This work was supported by Ministry of Science and Higher
Education of the Russian Federation (project AAAA-A18-
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