Triflic Acid Promoted Transformations of Linear-Conjugated Enynones and their Reactions with Arenes. Synthesis of Dihydropyranones, Conjugated Dienones, and Indanes

Article abstract of DOI:10.1002/ejoc.202100280

Linear-conjugated enynones,1,5-diarylpent-4-en-2-yn-1-ones [Ar²?CH=CH?C≡C?C(=O)Ar¹], have been cyclized into 2,6-diaryl-2,3-dihydropyran-4-ones in triflic acid TfOH (CF₃SO₃H). Reactions of these enynones with ar

Full text of DOI:10.1002/ejoc.202100280

Full Papers
doi.org/10.1002/ejoc.202100280
Triflic Acid Promoted Transformations of Linear-
Conjugated Enynones and their Reactions with Arenes.
Synthesis of Dihydropyranones, Conjugated Dienones, and
Indanes
Anna S. Zalivatskaya,[a, b] Alexander A. Golovanov,[c] Irina A. Boyarskaya,[a]
Mariya A. Kruykova,[d] Olesya V. Khoroshilova,[a] and Aleksander V. Vasilyev*[a, b]
Linear-conjugated
enynones,1,5-diarylpent-4-en-2-yn-1-ones
cyclized into alkylidene indanes. Plausible reaction mechanisms
have been proposed. According to quantum chemical calcu-
lations by DFT method, initial key reactive intermediates are
vinyl type dications [Ar2À CH=CHÀ C+=CHÀ C(=O+H)Ar1], gener-
ated under the protonation of carbonyl oxygen and acetylene
bond of starting enynones in TfOH.
[Ar2À CH=CHÀ C�CÀ C(=O)Ar1], have been cyclized into 2,6-
diaryl-2,3-dihydropyran-4-ones in triflic acid TfOH (CF3SO3H).
Reactions of these enynones with arenes Ar3H in TfOH have
afforded, at first stage, products of hydroarylation of the
acetylene
bond,
1,3,5-triarylpent-2,4-dien-1-ones
[Ar2À CH=CHÀ C(Ar3)=CHÀ C(=O)Ar1], which have been further
Introduction
tigation on TfOH-promoted transformations of the series of 1,5-
diarylpent-4-en-2-yn-1-ones.
Nowadays, different linear- and cross-conjugated enynones are
widely used in organic synthesis (see recent reviews[1–5] on this
topic). However, among all enynone structures, the linear-
conjugated pent-4-en-2-yn-1-ones [>C=C(R)À C�CÀ C(R’)=O]
still remain sparsely investigated. One of the reasons of that is a
difficult synthesis of such compounds. There are just a few
examples of reactions of these enynones with nucleophiles,[6–7]
and their intramolecular cyclization into various carbocycles.[8]
Based on our recent studies on reactions of other types of
linear- and cross-conjugated enynones under the superelectro-
philic activation conditions[9–12] and on our short preliminary
communication on the cyclization of 1-aryl-5-phenylpent-4-en-
2-yn-1-ones into 6-aryl-2-phenyl-2,3-dihydropyran-4-ones in
triflic acid TfOH (CF3SO3H),[13] we undertook a special inves-
Protonation of enynones 1 in Brønsted acids may give rise
to various cationic species (Scheme 1). First protonation of
carbonyl oxygen affords cations A. The second consequent
protonation of triple or double carbon-carbon bonds may result
in the formation of dications B or C correspondingly. The
species A, B and C exist in several mesomeric forms having
delocalized positive charge on carbon atoms C1, C3 and C5,
that can be reactive electrophilic centers. Hypothetically, the
protonation of carbonyl oxygen and both unsaturated carbon-
carbon bonds leads to trications D, which can be considered as
three electrophilic synthons generated from enynones 1.
The main goal of this work was to investigate trans-
formations of 1,5-diarylpent-4-en-2-yn-1-ones under superelec-
trophilic activation conditions in Brønsted superacid TfOH,
including reactions with aromatic nucleophiles. Apart from that,
a quantum chemical calculation study of electronic character-
istics and reactivity of intermediate cations generated from
these enynones was performed by DFT method.
[a] A. S. Zalivatskaya, Dr. I. A. Boyarskaya, O. V. Khoroshilova,
Prof. Dr. A. V. Vasilyev
Department of Organic Chemistry, Institute of Chemistry,
Saint Petersburg State University,
Universitetskaya nab., 7/9, Saint Petersburg, 199034, Russia
E-mail: aleksvasil@mail.ru
a.vasilyev@spbu.ru
Results and discussion
http://chem.spbu.ru/research/nauchnye-gruppy/237-scientific-activities/
research-groups/951-nauchnaya-gruppa-professora-a-v-vasileva.html
[b] A. S. Zalivatskaya, Prof. Dr. A. V. Vasilyev
Department of Chemistry,
Saint Petersburg State Forest Technical University,
Institutsky per., 5, Saint Petersburg, 194021, Russia
[c] Dr. A. A. Golovanov
Laboratory of Organic Synthesis and Analysis no. 13,
Togliatti State University,
Belorusskaya ul., 14, Togliatti, 445667, Russia
[d] M. A. Kruykova
Starting 1,5-diarylpent-4-en-2-yn-1-ones 1a–i used in this study
are shown in Figure 1 (see their synthesis and characterization
in Experimental part and SI).
In the beginning of this study, we undertook theoretical
quantum chemical calculations of intermediate cations A, B, C
and D (see Scheme 1) derived under protonation of enynones 1
in order to estimate electrophilic properties and reactivity of
these species. Gibbs energies ΔG298 of protonation reactions
1!A!B!C!D, electronic and orbital characteristics (charge
distribution, HOMO/LUMO energies, contribution of atomic
orbitals into LUMO, global electrophilicity index ω[14]) of cations
Research Center for X-ray Diffraction Studies, Research park,
St. Petersburg State University,
Universitetskiy pr. 26, Saint Petersburg, Petrodvoretz, 198504, Russia
Supporting information for this article is available on the WWW under
https://doi.org/10.1002/ejoc.202100280
Eur. J. Org. Chem. 2021, 2634–2649
2634
© 2021 Wiley-VCH GmbH

Full Papers
doi.org/10.1002/ejoc.202100280
Scheme 1. Generating of various cationic species from linear-conjugated enynones 1 under the protonation in Brønsted acids.
Figure 1. Starting 1,5-diarylpent-4-en-2-yn-1-ones 1a–i used in this study.
A, B, C, D were calculated using DFT method. Cations A0–A7,
B0–B7, C0–C7, D0–D7 generated from enynones 1a, 1f, 1g,
1h, 1e, 1b, 1c, 1d correspondingly were studied. As an
example, see data for species A0–D0 generated from 1a in
Table 1. Calculation for other cations A1–D7 are presented in
Table S12 in SI.
Table 1. Selected electronic characteristics (DFT calculations) of cations A0, B0, C0, D0 derived from protonation of enynone 1a, and calculated Gibbs
energies ΔG298 of protonation reactions.
[c]
[c]
[c]
Cation
EHOMO
[eV]
ELUMO
[eV]
ω[a]
[eV]
q(C1),[b]
e
q(C3),[b]
e
q(C5),[b]
e
k(C1)LUMO
[%]
k(C3)LUMO
[%]
k(C5)LUMO
[%]
A0
B0
C0
D0
À 7.00
À 8.20
À 8.17
À 8.61
À 4.18
À 4.99
À 4.92
À 6.06
5.5
6.8
6.6
10.5
0.48
0.61
0.53
0.61
0.19
0.36
0.24
0.66
À 0.02
0.12
0.21
25.5
2.1
8.0
17.2
15.5
10.6
38.2
14.5
22.2
9.5
0.16
10.5
2.1
[a] Global electrophilicity index ω=(EHOMO +ELUMO)2/8(ELUMOÀ EHOMO). [b] Natural charges. [c] Contribution of atomic orbital into LUMO.
Eur. J. Org. Chem. 2021, 2634–2649
www.eurjoc.org
2635
© 2021 Wiley-VCH GmbH

Full Papers
doi.org/10.1002/ejoc.202100280
Calculations of Gibbs energies of protonation reactions
Thus, based on DFT calculations, taking into account
thermodynamical data on the most favorable formation of vinyl
dications B, and their electronic and orbital characteristics, one
may expect that these species should be key electrophilic
intermediates in reactions of enynones 1 in Brønsted super-
acids.
showed that the first protonation onto carbonyl oxygen leading
to species A0–A7 was thermodynamically very favorable. The
ΔG298 values of this step are À 86–À 57 kJ/mol (see scheme in
Table 1, and Table S12 in SI). The formation of dications B from
A by protonation of atom C2 of carbon-carbon triple bond is
also thermodynamically favorable; the corresponding
ΔG298values of protonation reactions A0–A7!B0–B7 are À 28–
À 5 kJ/mol. Alternative protonation of atom C4 of carbon-
carbon double bond in species A leading to dications C is much
more unfavorable (values ofΔG298for reactions A0–A7!C0–C7
are 18–47 kJ/mol), compared to the formation of dications B0–
B7. The third protonation of both B and C affording trications D
is completely impossible due to the very high ΔG298 values of
the corresponding protonation reactions B0–B7!D0–D7 (190–
211 kJ/mol) and C0–C7!D0–D7 (144–158 kJ/mol) (see Table 1,
and Table S12 in SI). Thus, the thermodynamical calculations
pointed out that a generating of dications B0–B7 is highly
likely.
Then, reactions of enynones 1 in the superacid TfOH were
carried out. Analogously to transformations of other types of
linear-[9] and cross-[11] conjugated enynones in TfOH, one would
expect a formation of the corresponding vinyl triflates, as
product of addition of TfOH to the acetylenic bond of enynones
1. We run reactions of several enynones 1 with 1.5 equiv. of
TfOH in CH2Cl2 at room temperature for 0.5–1 h and obtained
complex mixture of reaction products containing just traces of
1
vinyl triflates according to H, 19F and 13C NMR data. These vinyl
triflates were found to be unstable and were easily hydrolyzed
into the corresponding enolic forms of 1,3-diketones, which
were also detected among the reaction products in TfOH.
However, the enols 2a–d were obtained in good yields in
reactions of compounds 1c, 1d, 1f, 1h with H2SO4 (Scheme 2).
Structure of compound 2a was confirmed by X-ray analysis (see
SI). It should be specially mentioned that such 1,5-diaryl-3-
hydroxypent-2,4-diene-1-ones are very important substances.
They not only exhibit antiproliferative effect,[15] but also they are
precursors for the preparation of various pharmaceutically
significant drugs. In particular, they are used in the synthesis of
2-styrylchromones.[16]
It was found that enynones 1a, f, c, d were cyclized into 2,3-
dihydropyran-4-ones 3a–d correspondingly in excess of TfOH at
room temperature for 1 h (Scheme 3, see also our preliminary
communication[13]). The position of the double bond in
dihydropyranone structures 3a–d was confirmed by NOESY
correlations between vinyl proton and ortho-protons of neigh-
bor aromatic system (see SI). The same dihydropyranones were
obtained from enynones 1 in H2SO4; however, the reaction
proceeded much longer (2-3 days), compared to TfOH (1 h).
Then NMR study of intermediate cationic species generated
from enynones 1 was carried out. Dissolving of enynones 1c, d
in H2SO4 directly in NMR tube showed the formation of the
corresponding O-protonated forms of vinyl sulfates Ea, b at
room temperature in 3 h (see selected 1H and 13C NMR chemical
shifts in Scheme 4, and full spectral data in SI). Extending these
reactions in NMR tubes till 3 days afforded O-protonated forms
of dihydropyranones Fa, b (Scheme 4, and see spectral data in
SI). Similar protonated dihydropyranones, generated from cross-
conjugated enynones (1,5-diarylpent-1-en-4-yn-3-ones), were
observed by ourselves previously.[11] We also took NMR spectra
of enynones 1 in neat TfOH, however these spectra had more
complex character, they contained impurities of oligomeric
products of transformations of these compounds in the super-
acid.
Calculations of electrophilic properties of species A, B, C
showed that dications B and C had higher values of electro-
philicity index
ω 6.3–7.1 eV and 6.0–6.9 eV, respectively,
compared to cations A with ω 5.4–6.4 eV (see Table 1, and
Table S12 in SI). Cations A, B and C have positive charge
localization mainly on all three carbons C1, C3 and C5, which
may behave as reactive electrophilic centers (see Scheme 1).
Investigation of charge distribution revealed that the largest
positive charge was localized on atom C1: 0.42–0.48 e in A0–
A7, 0.58–0.62 e in B0–B7, 0.52–0.55 e in C0–C7. However,
contribution of C1 atomic orbital into LUMO is rather low in
B0–B7 (1.8–5.5%) and C0–C7 (0.9–8%) that pointed out a weak
orbital control in reactivity of this electrophilic center.
In species A0–A7, carbon C1 is the most reactive electro-
philic center, since other carbons bear less charge (À 0.30–0.21
e for C3; À 0.49–0.01 e for C5) and give less contribution into
LUMO (14.0–17.2% for C3; 12.4–14.5% for C5, compared to
21.8–25.5% for C1). However, no reactions took place at carbon
C1 (see below data on chemical transformations of enynones 1
in Brønsted acids), therefore it is unlikely that cations A may be
reactive species.
Concerning dications C0–C7, they have large positive
charges on carbons C3 and C5, 0.23–0.27 e and 0.18–0.21 e,
respectively. However, these carbons have low contributions
into LUMO: 3.0–11.2% for C3 and 8–31.3% for C5, that reveals
low orbital control. There is no coincidence in charge and
orbital controls for reactivity of atoms C3 and C5 in species C.
Thus, their participation in reactions has low probability.
Electronic properties of vinyl type dications B0–B7 show
that these species may have reactive electrophilic centers both
on carbon C3 and C5. Atom C3 possesses a big positive charge
0.15–0.36 e and gives a substantial contribution (12.1–15.5%)
into LUMO. Carbon C5 have a wide charge value from À 0.14 to
0.86 e, depending on substituents in aromatic rings; and this
carbon gives a big contribution into LUMO, 17.0–22.2% (see
Table 1, and Table S12 in SI). To clarify this point, which of
carbons C3 or C5 would be a reactive center, we conducted
reactions of enynones 1 in TfOH (vide infra).
The data obtained on the formation of vinyl sulfates
(triflates) Ea, b (Scheme 4) and enols 2 (Scheme 2), and their
cyclization into dihydropyranones 3 (Scheme 3 and 4) have
allowed proposing plausible reaction mechanisms of the
formation of these compounds (Scheme 5). Protonation of
carbonyl oxygen and acetylene bond of 1 gives rise to dication
Eur. J. Org. Chem. 2021, 2634–2649
www.eurjoc.org
2636
© 2021 Wiley-VCH GmbH

Full Papers
doi.org/10.1002/ejoc.202100280
Scheme 2. Transformation of enynones 1c, d, f, h into enols 2a–d correspondingly in H2SO4.
Scheme 3. Cyclization of enynones1a, f, c, d into dihydropyranones 3a–d correspondingly in TfOH.
B, which interacts with acid counter anions (HSO4 or TfOÀ )
leading to the corresponding O-protonated forms of vinyl
sulfates or triflates E. Hydrolysis (or transformation on silica gel
for vinyl triflates) of the later at this early reaction stage results
enols 2. Longer reaction time has finally led to cyclization of
species E (in its resonance form E’) into dihydropyranones 3
through an intermediate formation of species G and F. See also
a detailed discussion on mechanism of such dihydropyranone
formation in our previous studies[11,13] and in works.[17,18]
The next step of this study was investigation of reactions of
enynones 1 with arenes in TfOH. It was found that reaction of
1a with benzene in the excess of TfOH and CH2Cl2, as co-
solvent, furnished a mixture of isomeric alkylidene indanes Z-/E-
5a (Scheme 6). Taking into account that a key reactive
intermediate could be dication B0 (see data of DFT calculations
in Table 1), it was not clear how the indane 5a was formed.
À
Namely, which carbon C3 or C5 in the species B0 participated in
the first stage of electrophilic aromatic substitution with
benzene. In other words, at which carbon C3 or C5 phenyl
moiety was attached in interaction with species B0; the next
stage was cyclization into indane. To clarify this point, we run
the series of reactions of enynones 1a–d with polymethylated
arenes, mesitylene (1,3,5-trimethylbenzene), durene (1,2,4,5-
tetramethylbenzene), and para-xylene (1,4-dimethylbenzene),
under the action of TfOH (1.5 equiv.) in CH2Cl2 at room
temperature for 0.5 h (Scheme 7). These sterically hindered
arenes, giving ortho-methyl substituted aryl ring upon their
electrophilic substitution, were chosen to avoid a consequent
cyclization into indane after the first step of the reaction. These
reactions afforded dienones 4a–h, that unambiguously re-
Eur. J. Org. Chem. 2021, 2634–2649
www.eurjoc.org
2637
© 2021 Wiley-VCH GmbH

Full Papers
doi.org/10.1002/ejoc.202100280
Scheme 4. NMR study on the formation of O-protonated forms vinyl sulfates Ea, b and dihydropyranones Fa, b generated from enynones 1c, d in H2SO4.
Scheme 5. Plausible reaction mechanism for transformations of enynones1 in TfOH and H2SO4 leading to enols 2 and dihydropyranones 3.
Scheme 6. Reaction of enynone 1a with benzene in TfOH leading to E-/Z-indanes 5a.
vealed a hydroarylation of the acetylene bond in compounds 1
and participation of electrophilic center C3 of species B (see
Table 1) in reaction with aromatic molecules.
between vinyl protons of diene system with methyl groups and
protons of neighbor aryl rings (see spectra in SI). Dienones 4a,
b were obtained as pure 2Z-isomers, other compounds 4c–h
The obtained dienones 4 have 4-E-configuration of C4=C5
double bond and 2-E-or 2-Z-configuration of C2=C3 bond.
Structure of 4e was confirmed by X-ray analysis (see SI).
Stereochemical configuration of both carbon-carbon bonds in
compounds 4 was determined by HÀ H NOESY correlations
were mixtures of 2E-/Z-isomers. It should be noted that, in H
1
NMR spectra, signals of vinyl protons H4 (~7.20 ppm) and H5 (~
3
6.33 ppm) with JH4-H5 ~15.8 Hz for 2Z-isomers of 4 have been
down field shifted in comparison with the same signals for 2E-
Eur. J. Org. Chem. 2021, 2634–2649
www.eurjoc.org
2638
© 2021 Wiley-VCH GmbH

Full Papers
doi.org/10.1002/ejoc.202100280
Scheme 7. Hydroarylation of enynones 1a–f by arenes in TfOH leading to dienones 4a–l.
3
isomers, H4 (~8.64 ppm) and H5 (~6.41 ppm) with JH4-H5
~16.0 Hz (see spectra in SI).
Then, reactions of enynones 1a–i with other arenes
[benzene, xylenes (dimethylbenzenes), pseudocumene (1,2,4-
E-configuration of alkylidene exocyclic double bond, the stereo-
chemistry of that was unambiguously determined by HÀ H
NOESY correlations between vinyl proton with CH2 group of
indane ring (for Z-isomers) or aromatic protons (for E-isomers)
(see spectra in SI). E-Stereochemistry may be explained by
spatial factors. Trans-orientation of 3-aryl-3-oxopropylidene
group to aryl moiety of indane may be more favorable,
especially, for indanes 5j–z, 5aa–ae having substituents in
position 7 (peri-position to propylidene group).
To have additional proof on intermediate formation of
dienones 4 in the synthesis of indanes 5, the consequent
formation of E-/Z-dienones 4h and E-/Z-indanes 5j from
enynone 1a and para-xylene in TfOH was carried out
(Scheme 9). Compounds E-/Z-4h were obtained from 1a and
para-xylene in reaction with 1.5 equiv. of TfOH. Then E-/Z-4h
trimethylbenzene),
veratrole
(1,2-dimethoxybenzene),
naphthalene] in the excess of TfOH resulting alkylidene indanes
5a–5am in good yields were performed (Scheme 8). Yields of
compounds 5ae–al that were obtained in reactions with good
electron-donating arenes, veratrole and naphthalene, were
moderate 30–55%, perhaps, due to secondary electrophilic
reactions of the obtained electron rich indanes under super-
acidic conditions leading to oligomeric compounds. Structures
of 5b, c, d, w, xz, aa, ab, ac were confirmed by X-ray analysis
(see SI). In general, the reaction proceeded highly stereo-
selectively with the predominant formation of indanes 5 having
Eur. J. Org. Chem. 2021, 2634–2649
www.eurjoc.org
2639
© 2021 Wiley-VCH GmbH

Full Papers
doi.org/10.1002/ejoc.202100280
Scheme 8. Reaction of enynones 1a–i with arenes inTfOH leading to indanes5a–al.
Eur. J. Org. Chem. 2021, 2634–2649
www.eurjoc.org
2640
© 2021 Wiley-VCH GmbH

Full Papers
doi.org/10.1002/ejoc.202100280
Scheme 9. Consequent formation ofdienone 4h and indane 5j from enynone 1a and para-xylene in TfOH.
were transformed into E-/Z-5j in the excess of TfOH (15 equiv.). Conclusions
Apart from that, running reaction of 1a and para-xylene in the
excess of TfOH resulted directly E-/Z-5j.
Novel methods of synthesis of compounds of the series of 2,3-
Summarizing all the data obtained on the synthesis of
dienones 4 and indanes 5 (Schemes 6–9), one may propose a
plausible reaction mechanism of the formation of these
compounds (Scheme 10). Interaction of dication B with arene
affords O-protonated form of dienone H, hydrolysis of which
results in the formation of dienone 4. In the excess of TfOH,
species H may be protonated at carbon-carbon bond giving
dihydropyran-4-ones, conjugated dienones, alkylidene indanes,
have been developed on the basis of transformations of linear-
conjugated enynons, 1,5-diarylpent-4-en-2-yn-1-ones, under
superelectrophilic activation conditions in Brønsted superacid
TfOH.
dication I, which is finally cyclized into indane 5. The formation Experimental Section
of indanes 5 reveals that enynones 1 in reactions with arenes in
TfOH behave as 1,3-dielectrophile J (Scheme 10; see also
Scheme 1 in Introduction).
General information. The NMR spectra of solutions of compounds
in CDCl3 were recorded on Bruker AVANCE III 400 (at 400and
1
100 MHz for Hand 13C NMR spectra respectively) spectrometer at
1
°
25 C. The residual proton-solvent peak CDCl3 (δ 7.26 ppm) for H
It should be noted that synthesis of indanes and indenes is
very important since these compounds have a lot of practical
applications, as functional materials, biologically active sub-
stances, pharmaceuticals, ligands for metal complexes (see
recent reviews[19–21] on synthesis and properties of indanes and
indenes). However, in this field, synthesis of alkylideneindanes
has not been very much developed. These indane derivatives
are still hardly available compounds.[22–24]
NMR spectra and the carbon signal of CDCl3 (δ 77.0 ppm) for 13C
NMR spectra were used as references. HRMS was carried out at
instruments Bruker maXis HRMS-ESI-QTOF and Varian 902-MS
MALDI Mass Spectrometer. The preparative reactions were moni-
tored by thin-layer chromatography carried out on silica gel plates
(Alugram SIL G/UV-254), using UV light for detection. Preparative
TLC was performed on silica gel Chemapol L 5/40 with petroleum
ether-ethyl acetate mixture eluation.
X-Ray analysis. Single crystal X-ray analysis was performed at single
crystal diffractometer Agilent Technologies (Oxford Diffraction)
«Supernova». A suitable crystal was selected and studied on the
diffractometer. The crystal was kept at 100(2) K during data
collection. Using Olex2[25] the structure was solved with the
ShelXS[26] structure solution program using Direct Methods and
Scheme 10. A plausible reaction mechanism of the formation of dienones 4 and indanes 5 from enynones 1 and arenes in TfOH.
Eur. J. Org. Chem. 2021, 2634–2649
www.eurjoc.org
2641
© 2021 Wiley-VCH GmbH

Full Papers
doi.org/10.1002/ejoc.202100280
refined with the ShelXL refinement package using Least Squares
minimisation. DFT calculations. All computations were carried out
at the DFT/HF hybrid level of theory using hybrid exchange
functional B3LYP by using GAUSSIAN 2009 program packages.[27]
The geometries optimization were performed using the 6-311+
G(2d,2p) basis set (standard 6-311G basis set added with polar-
ization (d,p) and diffuse functions). Optimizations were performed
on all degrees of freedom and solvent phase optimized structures
were verified as true minima with no imaginary frequencies. The
Hessian matrix was calculated analytically for the optimized
structures in order to prove the location of correct minima and to
estimate the thermodynamic parameters. Solvent-phase calcula-
tions used the Polarizable Continuum Model (PCM, solvent=water).
(E)-1-Phenyl-5-(4-Methylphenyl)pent-4-en-2-yn-1-one (1f): Light
1
°
yellow needles, mp 68–69 C. H NMR (400 MHz, CDCl3) δ 2.38 (s,
3H), 6.34 (d, J=16.2 Hz, 1H), 7.20 (d, J=8.0 Hz, 2H), 7.34 (d, J=
16.2 Hz, 1H), 7.38 (d, J=8.0 Hz, 2H), 7.49–7.53 (m, 2H), 7.60–7.64 (m,
2H), 8.17–8.20 (m, 2H).13C NMR (101 MHz, CDCl3) δ 21.60, 89.03,
93.62, 104.33, 127.16, 128.71, 129.68, 129.84, 132.68, 134.07, 137.17,
140.72, 148.16, 178.06. HRMS (ESI) calcd. for C18H15O+ [M+H]+
247.1117; found 247.1112.
(E)-5-(4-Chlorophenyl)-1-phenylpent-4-en-2-yn-1-one (1g): Light
1
°
yellow needles, mp 93–94 C. H NMR (400 MHz, CDCl3) δ 6.36 (d,
J=16.3 Hz, 1H), 7.29 (d, J=16.3 Hz, 1H), 7.34–7.40 (m, 4 H), 7.49–
7.53 (m, 2H), 7.60–7.65 (m, 1H), 8.16–8.18 (m, 2H).13C NMR
(101 MHz, CDCl3) δ 89.39, 92.44, 106.17, 128.28, 128.74, 129.38,
129.68, 133.81, 134.22, 136.12, 137.01, 146.40, 177.94. HRMS (ESI)
calcd. for C17H12ClO+ [M+H]+ 267.0571; found 267.0578.
Preparation and characterization of compounds
(E)-5-(4-Bromophenyl)-1-phenylpent-4-en-2-yn-1-one (1h): Light
General procedure for synthesis of starting1,5-diarylpent-4-en-2-
yn-1-ones 1a–i. Synthesis was carried out according to literature
procedure.[28] Mixture of Pd(OAc)2 (0.03 mmol) and PPh3
(0.07 mmol) and CuI (0.17 mmol) in THF (20 ml) was stirred in argon
atmosphere at room temperature for 15 min. Then benzoic acid
chloride (1.6 mmol), 1-aryl-but-1-en-3-yne (1.9 mmol) and triethyl-
amine (1.6 mmol) were consequently added. Reaction mixture was
stirred at room temperature for 3 h. Then solvent was removed in
vacuo, the obtained residue was subjected to column chromatog-
raphy on silica gel [eluent: petroleum ether (fraction with bp 40–
1
°
yellow needles, mp 101–102 C. H NMR (400 MHz, CDCl3) δ 6.38 (d,
J=16.3 Hz, 1H), 7.27 (d, J=16.3 Hz, 1H), 7.34 (d, J=8.4 Hz, 2H),
7.49–7.53 (m, 4H). 7.60–7.64 (m, 1H), 8.16–8.18 (m, 2H).13C NMR
(101 MHz, CDCl3) δ 89.43, 92.40, 106.30, 124.43, 128.50, 128.75,
129.68, 132.35, 134.23, 137.01, 146.45, 177.94. HRMS (ESI) calcd. for
C17H12BrO+ [M+H]+ 311.0066; found 311.0061
(E)-1-(5-Bromofuran-2-yl)-5-phenylpent-4-en-2-yn-1-one
(1i):
1
°
Light yellow plates, mp 97–98 C. H NMR (400 MHz, CDCl3) δ 6.33
(d, J=16.3 Hz, 1H), 6.54 (d, J=3.6 Hz, 1H), 7.30 (d, J=3.6 Hz, 1H),
7.33 (d, J=16.3 Hz, 1H), 7.38–7.40 (m, 3H), 7.46–7.48 (m, 2H). 13C
NMR (101 MHz, CDCl3) δ 87.79, 92.64, 105.09, 114.90, 122.33, 127.21,
129.13, 130.41, 130.53, 135.19, 148.59, 154.90, 163.33. HRMS (ESI)
calcd. for C17H12BrO+ [M+H]+ 300.9859; found 300.9854.
°
70 C) – ethyl acetate].
(E)-1,5-Diphenylpent-4-en-2-yn-1-one (1a):[28] Light yellow needles,
1
°
mp 64–65 C. H NMR (400 MHz, CDCl3) δ 6.39 (d, J=16.3 Hz, 1H),
7.36 (d, J=16.3 Hz, 1H), 7.38–7.41 (m, 3H), 7.47–7.49 (m, 2H), 7.52
(d, J=7.8 Hz, 2H), 7.60–7.64 (m, 1H), 8.18–8.20 (m, 2H). 13C NMR
(101 MHz, CDCl3) δ 89.10, 93.06, 105.49, 127.15, 128.71, 129.10,
129.67, 130.24, 134.13, 135.32, 137.08, 147.99, 178.01. HRMS (ESI)
calcd. For C17H13O+ [M+H]+ 233.0961; found 233.0966.
General procedure for synthesis of (2Z,4E)-3-hydroxy-1,5-diary-
lpenta-2,4-dien-1-ones 2a–d from enynones 1in H2SO4. H2SO4
(0.1 ml, 1.9 mmol) was added with vigorous stirring at room
temperature to a solution of enynone1 (0.086 mmol) in CH2Cl2
(0.1 ml).The mixture was stirred for 2–3 h. Then the reaction mixture
was poured into H2O (50 ml), extracted with CHCl3 (3×25 ml). The
combined extracts were consequently washed with H2O (50 ml),
saturated aqueous solution ofNaHCO3(25 ml), again with H2O
(25 ml) and dried with Na2SO4. The solvent was removed under
reduced pressure, the product was isolated by preparative TLC on
LS 5/40 μm silica gel plates, eluent-petroleum ether-EtOAc, 95:5
vol. The separated fractions were washed off from the sorbent with
CH2Cl2.
(E)-5-Phenyl-1-(4-methylphenyl)pent-4-en-2-yn-1-one
(1b):[28]
1
°
Light yellow needles, mp 56.5–57.5 C. H NMR (CDCl3, 500 MHz) δ,
ppm: 2.32 (s, 3H), 6.25 (d, J=16.3 Hz, 1H), 7.18–7.22 (m, 3H), 7.26–
7.35 (m, 5H), 7.64 (d, J=8.5 Hz, 2H), 7.99 (d, J=7.9 Hz, 2H).13C NMR
(126 MHz, CDCl3) δ 21.5, 88.9, 92.2, 105.1, 126.7, 128.7, 128.7, 129.4,
129.8, 134.4, 134.9, 144.8, 147.3, 177.2. HRMS (ESI) calcd. For
C18H15O+ [M+H]+ 247.1117; found 247.1123.
(E)-1-(4-Chlorophenyl)-5-phenylpent-4-en-2-yn-1-one
(1c):[28]
Brown oil.1H NMR (400 MHz, CDCl3) δ 6.38 (d, J=16.3 Hz, 1H), 7.36
(d, J=16.3 Hz, 1H), 7.38–7.41 (m, 3H), 7.47–7.49 (m, 4H), 8.11 (d, J=
8.6 Hz, 2H). 13C NMR (101 MHz, CDCl3) δ 88.78, 93.62, 105.24, 127.19,
129.08, 129.12, 130.36, 130.96, 135.21, 135.49, 140.71, 148.39,
176.62.HRMS (ESI) calcd. For C17H12ClO+ [M+H]+ 267.0571; found
267.0576.
(2Z,4E)-1-(4-Chlorophenyl)-3-hydroxy-5-phenylpenta-2,4-dien-1-
°
one (2a): Yield 17 mg (78%). Yellow crystals. M.p. 100–102 C. The
structure was confirmed by X-ray analysis. 1H NMR (400 MHz, CDCl3)
δ, ppm: 6.30 (s, 1H), 6.64 (d, 3J=15.8 Hz, 1H), 7.38–7.42 (m, 3H), 7.45
3
(d, J=8.5 Hz, 2H), 7.56–7.58 (m, 2H), 7.70 (d, J=15.8 Hz, 1H), 7.90
(d, J=8.5 Hz, 2H), 16.06 (bsr, 1H). 13C NMR (100 MHz, CDCl3) δ, ppm:
(E)-1-(4-Bromophenyl)-5-phenylpent-4-en-2-yn-1-one (1d): Yellow
97.6, 123.2, 128.2, 128.9, 129.1, 130.3, 134.5, 135.1, 139.0, 140.6,
1
+
179.7, 188.3 HRMS (ESI) calcd. for C17H14ClO2 [M+H]+ 285.0677;
°
needles, mp 89–90 C. H NMR (400 MHz, CDCl3) δ 6.38 (d, J=
16.1 Hz, 1H), 7.36 (d, J=16.1 Hz, 1H), 7.38–7.41 (m, 3H), 7.47–7.50
(m, 2H), 7.65 (d, J=8.6 Hz, 2H), 8.03 (d, J=8.6 Hz, 2H). 13C NMR
(101 MHz, CDCl3) δ 88.78, 93.68, 105.25, 127.21, 129.14, 129.57,
130.39, 131.05, 132.09, 135.23, 135.90, 148.44, 176.84. HRMS (ESI)
calcd. For C17H12BrO+ [M+H]+ 311.0066; found 311.0075.
found 285.0680.
(2Z,4E)-1-(4-Bromophenyl)-3-hydroxy-5-phenylpenta-2,4-dien-1-
one (2b): Yield 13 mg (60%). Green oil. 1H NMR (400 MHz, CDCl3) δ,
3
ppm: 6.30 (s, 1H), 6.64 (d, J=15.8 Hz, 1H), 7.39–7.41 (m, 3H), 7.55–
3
7.58 (m, 2H), 7.62 (d, J=8.6 Hz, 2H), 7.70 (d, J=15.8 Hz, 1H), 7.82
(d, J=8.6 Hz, 2H), 16.06 (bsr, 1H). 13C NMR (100 MHz, CDCl3) δ, ppm:
(E)-1-(4-Nitrophenyl)-5-phenylpent-4-en-2-yn-1-one (1e): Brown-
1
ish oil. H NMR (CDCl3, 500 MHz) δ, ppm: 6.41 (d, J=16.3 Hz, 1H),
97.6, 123.3, 127.6, 128.2, 129.0, 129.1, 130.3, 132.1, 135.1, 135.3,
7.41–7.43 (m, 4H), 7.49–7.51 (m, 2H), 7.34–7.36 (m, 4H). 13C NMR
(126 MHz, CDCl3) δ 88.7, 95.5, 104.8, 123.9, 127.3, 129.2, 130.5,
130.7, 135.0, 141.2, 149.5, 151.0, 175.8. HRMS (ESI) calcd. for
+
140.6, 179.8, 188.3.HRMS (ESI) calcd. for C17H14BrO2 [M+H]+
329.0172; found 329.0177.
+
(2Z,4E)-3-Hydroxy-5-(4-methylphenyl)-1-phenyl-penta-2,4-dien-1-
C17H12NO3 [M+H]+ 278.0812; found 278.0817.
1
one (2c): Yield 14 mg (60%). Green oil. H NMR (400 MHz, CDCl3) δ,
3
ppm: 2.39 (s, 3H), 6.34 (s, 1H), 6.62 (d, J=15.8 Hz, 1H), 7.21 (d, J=
Eur. J. Org. Chem. 2021, 2634–2649
www.eurjoc.org
2642
© 2021 Wiley-VCH GmbH

Full Papers
doi.org/10.1002/ejoc.202100280
7.8 Hz, 2H), 7.46–7.49 (m, 4H), 7.53–7.57 (m, 1H), 7.68 (d, 3J=
mixture was stirred for 0.5 h. Then reaction mixture was poured
into H2O (50 ml), extracted with CHCl3 (3×25 ml). The combined
extracts were consequently washed with H2O (50 ml), saturated
aqueous solution of NaHCO3(25 ml), again with H2O (25 ml) and
dried with Na2SO4. The solvent was removed under reduced
pressure, the product was isolated by preparative TLC on LS
5/40 μm silica gel plates, eluent petroleum ether-EtOAc, 95:5, vol.
The separated fractions were washed off from the sorbent with
CH2Cl2.
15.8 Hz, 1H), 7.94–7.97 (m, 2H), 16.20 (bsr, 1H). 13C NMR (100 MHz,
CDCl3) δ, ppm: 21.6, 97.6, 122.5, 127.5, 128.2, 128.8, 129.8, 132.5,
132.6, 136.5, 140.3, 140.6, 180.1, 189.1 HRMS (ESI) calcd. for
+
C18H17O2 [M+H]+ 265.1223; found 265.1227.
(2Z,4E)-5-(4-Bromophenyl)-3-hydroxy-1-phenylpenta-2,4-dien-1-
one (2d): Yield 17 mg (80%). Green oil. 1H NMR (400 MHz, CDCl3) δ,
ppm: 6.34 (s, 1H), 6.63 (d, J=15.8 Hz, 1H), 7.42 (d, J=8.5 Hz, 2H),
7.46–750 (m, 2H), 7.52–7.57 (m, 3H), 7.61 (d, J=15.8 Hz, 1H), 7.94–
7.99 (m, 2H). 13C NMR (100 MHz, CDCl3) δ, ppm: 98.0, 124.1, 124.3,
127.5, 128.8, 129.5, 132.3, 132.8, 134.2, 136.4, 138.7, 178.9, 189.9.
(2Z,4E)-3-(2,4,6-Trimethylphenyl)-1,5-diphenylpenta-2,4-dien-1-
one (4a): Yield 21 mg (70%). Green oil. 1H NMR (400 MHz, CDCl3) δ,
ppm: 2.11 (s, 6H), 2.34 (s, 3H), 6.39 (d, J=15.7 Hz, 1H), 6.92 (s, 2H),
7.20 (d, J=15.7 Hz, 1H), 7.29–7.36 (m, 4H), 7.43–7.46 (m, 4H), 7.51–
7.54 (m, 1H), 7.95–7.97 (m, 2H).13C NMR (101 MHz, CDCl3) δ, ppm:
19.8, 21.4, 124.8, 127.4, 128.2, 128.3, 128.6, 128.8, 128.9, 130.7,
132.6, 133.7, 134.8, 136.5, 136.6, 137.5, 138.9, 154.2, 189.6. HRMS
(ESI) calcd. for C26H25O+ [M+H]+ 353.1900, found 353.1903.
+
HRMS (ESI) calcd. for C17H14BrO2 [M+H]+ 329.0172; found
329.0180.
General procedure for synthesis of 2,6-diaryl-2,3-dihydro-4H-
pyran-4-ones 3a–d from enynones1 in TfOH. TfOH (0.1 ml,
1.29 mmol) was added with vigorous stirring at room temperature
to a solution of enynone 1 (0.086 mmol) in CH2Cl2 (0.1 ml).The
mixture was stirred for 1 h. Then reaction mixture was poured into
H2O (50 ml), extracted with CHCl3 (3×25 ml). The combined extracts
were consequently washed with H2O (50 ml), saturated aqueous
solution of NaHCO3(25 ml), again with H2O (25 ml) and dried with
Na2SO4. The solvent was removed under reduced pressure, the
product was isolated by preparative TLC on LS 5/40 μm silica gel
plates, eluent-petroleum ether-EtOAc, 95:5 vol. The separated
fractions were washed off from the sorbent with CH2Cl2.
(2Z,4E)-3-(2,4,6-Trimethylphenyl)-5-phenyl-1-(4-methylphenyl)
1
penta-2,4-dien-1-one (4b): Yield 26 mg (90%). Green oil. H NMR
(400 MHz, CDCl3) δ, ppm: 2.10 (s, 6H), 2.34 (s, 3H), 2.41 (s, 3H), 6.37
(d, J=15.7 Hz, 1H), 6.91 (s, 2H), 7.18 (d, J=15.7 Hz, 1H), 7.23–7.26
(m, 3H), 7.28–7.35 (m, 3H), 7.43 (d, J=7.2 Hz, 2H), 7.87 (d, J=8.2 Hz,
2H). 13C NMR (101 MHz, CDCl3) δ, ppm: 19.8, 21.4, 21.7, 124.9, 127.4,
128.1, 128.5, 128.8, 129.3, 130.8, 133.7, 134.8, 136.3, 136.5, 136.6,
+
137.2, 143.3, 153.8, 189.2. HRMS (ESI) calcd. for C27H27O+ [M+H]
367.2056, found 367.2058.
2,6-Diphenyl-2,3-dihydro-4H-pyran-4-one (3a):11 Yield 11 mg
1
°
(50%). Pale-yellow solid. Mp 94–95 C. H NMR (400 MHz, CDCl3) δ,
(2E-,4E-)/(2Z-,4E-)-1-(4-Chlorophenyl)-3-(2,4,6-trimethylphenyl)-5-
phenylpenta-2,4-dien-1-one (4c): 2E-,4E-/2Z-,4E- in a ratio of 5:4.
General yield of 20 mg (70%).
3
4
2
ppm: 2.75 (ddd, 2J=16.9, J=3.4, J=0.8 Hz, 1H), 2.97 (dd, J=16.9,
3J=14.1 Hz, 1H), 5.59 (dd, 3J=14.1, 3J=3.4 Hz, 1H), 6.13 (d, 4 J=
0.8 Hz, 1H), 7.41–7.47 (m, 4H), 7.48–7.52 (m, 3H), 7.77–7.80 (m, 2H).
13C NMR (100 MHz, CDCl3) δ, ppm: 43.1, 81.2, 102.5, 126.3, 126.8,
128.9, 129.0, 131.9, 132.7, 138.5, 170.5, 193.1. HRMS (ESI) calcd. for
2Z-,4E-4c:1H NMR (400 MHz, CDCl3), selected signals δ, ppm: 2.09 (s,
6H), 2.35 (s, 3H), 6.40 (d, J=15.6 Hz, 1H), 6.93 (s, 2H), 7.19 (d, J=
15.6 Hz, 1H), 7.20 (s, 1H), 7.29–7.36 (m, 3H), 7.40–7.45 (m, 4H), 7.89
(d, J=8.5 Hz, 2H). 13C NMR (101 MHz, CDCl3) selected signals δ,
ppm: 19.8, 21.4, 124.2, 127.5, 128.2, 128.9, 129.7, 129.7, 130.5, 133.5,
C17H15O2 [M+H]+ 251.1067; found 251.1073.
+
6-(4-Chlorophenyl)-2-phenyl-2,3-dihydro-4H-pyran4-one
(3b):
Yield 13 mg (60%). Brown oil. 1H NMR (400 MHz, CDCl3) δ, ppm:
2.75 (ddd, 2J=16.9, 3J=3.4, 4J=0.9, 1H), 2.96 (dd, 2J=16.9, 3J=14.1,
134.7, 136.4, 136.7, 137.2, 138.0, 138.9, 154.9, 188.3. 2E-,4E-4c: H
1
NMR (400 MHz, CDCl3), selected signals δ, ppm: 2.22 (s, 6H), 2.38 (s,
3H), 6.46 (d, J=16.0 Hz, 1H), 6.68 (s, 1H), 6.98 (s, 2H), 7.28–7.34 (m,
3H), 7.44 (d, J=8.6 Hz, 2H), 7.48–7.50 (m, 2H), 7.92 (d, J=8.6 Hz,
2H), 8.61 (d, J=16.0 Hz, 1H). 13C NMR (101 MHz, CDCl3), selected
signals δ, ppm: 20.0, 21.2, 122.5, 126.0, 127.9, 128.4, 128.8, 129.0,
129.2, 129.8, 135.7, 136.5, 137.2, 140.1, 156.0, 189.9. HRMS (ESI)
calcd. for C26H24ClO+ [M+H]+: 387.1510, found 387.1513.
3
3
4
1H), 5.58 (dd, J=14.1, J=3.4 Hz, 1H), 6.09 (d, J=0.9 Hz, 1H), 7.41
(d, J=8.8 Hz, 2H), 7.44–7.48 (m, 5H), 7.71 (d, J=8.8, 2H). 13C NMR
(100 MHz, CDCl3) δ, ppm: 43.1, 81.4, 102.6, 126.4, 128.1, 129.0,
129.1, 129.2, 131.2, 138.1, 138.3, 169.2, 192.8. HRMS (ESI) calcd. for
+
C17H14ClO2 [M+H]+ 285.0677; found 285.0683.
6-(4-Bromophenyl)-2-phenyl-2,3-dihydro-4H-pyran4-one
(3c):
Yield 10 mg (50%). Brown oil. 1H NMR (400 MHz, CDCl3) δ, ppm:
(2E-,4E-)/(2Z-,4E-)-1-(4-Bromophenyl)-3-(2,4,6-trimethylphenyl)-5-
phenylpenta-2,4-dien-1-one (4d): (2E,4E)/(2Z-,4E-)- in a ratio of
5:4. General yield of 22 mg (80%). 2Z-,4E-4d:1H NMR (400 MHz,
CDCl3), selected signals δ, ppm: 2.07 (s, 6H), 2.37 (s, 3H), 6.39 (d, J=
15.6 Hz, 1H), 6.91 (s, 2H), 7.17 (d, J=15.6 Hz, 1H), 7.18 (s, 1H), 7.28–
7.35 (m, 3H), 7.42–7.44 (m, 2H), 7.57 (d, J=8.5 Hz, 2H), 7.80 (d, J=
8.5 Hz, 2H).
2
3
4
2
3
2.75 (ddd, J=17.0, J=3.4, J=0.9 Hz, 1H), 2.96 (dd, J=17.0, J=
3
3
4
14.1 Hz, 1H), 5.58 (dd, J=14.1, J=3.4 Hz, 1H), 6.10 (d, J=0.9 Hz,
1H), 7.42–7.50 (m, 5H), 7.57 (d, J=8.8 Hz, 2H), 7.64 (d, J=8.8 Hz,
2H). 13C NMR (100 MHz, CDCl3) δ, ppm: 43.0, 81.4, 102.6, 126.4,
126.6, 128.3, 129.1, 132.2, 138.2, 169.4, 192.9. HRMS (ESI) calcd. for
+
C17H14BrO2 [M+H]+ 329.0172; found 329.0180.
6-(4-Methylphenyl)-2-phenyl-2,3-dihydro-4H-pyran4-one
(3d):
2E-,4E-4d:1H NMR (400 MHz, CDCl3), selected signals δ, ppm:2.21 (s,
6H), 2.37 (s, 3H), 6.44 (d, J=16.0 Hz, 1H), 6.66 (s, 1H), 6.97 (s, 2H),
7.28–7.35 (m, 3H), 7.47–7.49 (m, 2H), 7.60 (d, J=8.6 Hz, 2H), 7.83 (d,
J=8.6 Hz, 2H), 8.59 (d, J=16.0 Hz, 1H).
Yield 10 mg (50%). Brown oil. 1H NMR (400 MHz, CDCl3) δ, ppm:
2
3
4
2.40 (s, 3H), 2.73 (ddd, J=16.9, J=3.4, J=0.9 Hz, 1H), 2.96 (dd,
2J=16.9, 3J=14.1 Hz, 1H), 5.56 (dd, 3J=14.1, 3J=3.4 Hz, 1H), 6.12 (d,
4J=0.9 Hz, 1H), 7.25–7.27 (m, 2H), 7.39 (d, J=8.0 Hz, 2H), 7.42–7.44
(m, 2H), 7.47–7.51 (m, 2H), 7.76–7.79 (m, 2H). 13C NMR (100 MHz,
CDCl3) δ, ppm: 21.4, 43.0, 81.2, 102.4, 126.4, 126.8, 128.8, 129.7,
131.9, 132.8, 135.4, 139.0, 170.6, 193.3. HRMS (ESI) calcd. for
13C NMR (CDCl3, 100 MHz) δ, ppm (for mixture of (2E-,4E-)/(2Z-,4E-
)-isomers): 19.8, 20.0, 21.2, 21.4, 122.4, 124.1, 126.1, 127.5, 127.6,
127.8, 128.0, 128.2, 128.4, 128.8, 128.9, 129.1, 129.2, 129.8, 129.9,
130.5, 131.9, 132.0, 133.5, 134.7, 135.7, 136.4, 136.5, 136.7, 136.8,
137.4, 137.6, 138.1, 138.5, 140.2, 155.0, 156.1, 188.5, 190.0. HRMS
(ESI) calcd. for C26H23BrNaO[M+Na]: 453.0830, found 453.0835.
+
C18H17O2 [M+H]+ 265.1223; found 265.1230.
General procedure for synthesis of 1,3,5-triarylpenta-2,4-dien-1-
one 4a- from enynones 1in TfOH. TfOH (0.129 mmol) was added
with vigorous stirring at room temperature to a solution of
enynone 1 (0.086 mmol), arene (0.103 mmol) in CH2Cl2 (0.1 ml).The
(2E-,4E-)/(2Z-,4E-)-3-(2,4,6-Trimethylphenyl)-1-(4-nitrophenyl)-5-
phenylpenta-2,4-dien-1-one (4e): (2E,4E)/(2Z-,4E-)- in a ratio of
9:10. General yield of 24 mg (83%). (2Z,4E)-4e: Green crystals. M.p.
Eur. J. Org. Chem. 2021, 2634–2649
www.eurjoc.org
2643
© 2021 Wiley-VCH GmbH

Full Papers
doi.org/10.1002/ejoc.202100280
1
°
146–148 C. The structure was confirmed by X-ray analysis. H NMR
(400 MHz, CDCl3), selected signals δ, ppm: 2.09 (s, 6H), 2.34 (s, 3H),
6.46 (d, J=15.8 Hz, 1H), 6.92 (s, 2H), 7.20 (s, 1H), 7.21 (d, J=15.8 Hz,
1H), 7.31–7.37 (m, 3H), 7.44–7.46 (m, 2H), 8.04 (d, J=8.8 Hz, 2H),
8.27 (d, J=8.8 Hz, 2H). 13C NMR (101 MHz, CDCl3) selected signals δ,
ppm: 19.8, 21.3, 123.8, 127.6, 128.3, 128.9, 129.1, 130.2, 134.7, 139.3,
133.9, 136.9, 137.2, 139.62, 139.64, 143.4, 156.0, 191.0. HRMS (ESI)
calcd. for C28H28NaO [M+Na] 403.2038, found 403.2043.
(2E-,4E-)/(2Z-,4E-)-3-(2,5-Dimethylphenyl)-1,5-diphenylpenta-2,4-
dien-1-one (4i): Green oil. (2E-,4E-)/(2Z-,4E-)- in a ratio of 10:7.
1
General yield of 17 mg (60%). (2Z,4E)-4i: H NMR (400 MHz, CDCl3),
selected signals δ, ppm: 2.16 (s, 3H), 2.33 (s, 3H), 6.39 (d, J=15.8 Hz,
1H), 6.85 (s, 1H), 7.16 (s, 1H), 7.20 (d, J=15.8 Hz, 1H), 7.30–7.36 (m,
1
149.9, 156.7, 188.1. (2E,4E)-4e: H NMR (400 MHz, CDCl3), selected
signals δ, ppm: 2.22 (s, 6H), 2.38 (s, 3H), 6.53 (d, J=16.0 Hz, 1H),
6.70 (s, 1H), 6.98 (s, 2H), 7.19 (s, 1H), 7.31–7.37 (m, 3H), 7.50–7.52 (m,
2H), 8.10 (d, J=8.8 Hz, 2H), 8.31 (d, J=8.8 Hz, 2H), 8.66 (d, J=
16.0 Hz, 1H). 13C NMR (101 MHz, CDCl3) selected signals δ, ppm:
20.0, 21.2, 121.7, 125.8, 158.0, 189.2.13C NMR (101 MHz, CDCl3) δ,
ppm (for mixture of (2E,4E)/(2Z-,4E-)-isomers): 19.8, 20.0, 21.2, 21.3,
121.7, 123.7, 123.8, 123.9, 125.8, 127.6, 128.1, 128.3, 128.5, 128.9,
129.0, 129.1, 129.3, 129.4, 129.6, 130.2, 133.1, 134.7, 135.6, 136.2,
136.5, 137.1, 137.6, 139.3, 141.6, 143.7, 144.5, 149.9, 156.7, 158.0,
188.1. HRMS (ESI) calcd. for C26H23NNaO3 [M+Na]: 420.1576, found
420.1570.
4H), 7.43–7.47 (m, 4H), 7.50 (d, J=8.0 Hz, 2H), 7.93–7.95 (m, 2H). 13
C
NMR (101 MHz, CDCl3), selected signals δ, ppm: 19.2, 19.5, 21.1,
21.2, 122.9, 124.9, 126.8, 127.4, 127.8, 128.4, 128.5, 128.7, 128.8,
128.9, 129.0, 129.1, 129.8, 129.9, 130.2, 131.6, 132.5, 132.7, 134.9,
135.3, 136.5, 136.8, 136.9, 138.7, 139.1, 139.7, 139.9, 140.9, 154.5,
1
156.0, 190.3, 191.4. (2E,4E)-4i: H NMR (400 MHz, CDCl3), selected
signals δ, ppm: 2.27 (s, 3H), 2.40 (s, 3H), 6.47 (d, J=16.1 Hz, 1H),
6.78 (s, 1H), 7.15 (s, 1H), 8.02 (d, J=8.4 Hz, 2H), 8.60 (d, J=16.1 Hz,
1H). 13C NMR (101 MHz, CDCl3), selected signals δ, ppm: 19.2, 19.5,
21.1, 21.2, 122.9, 124.9, 126.8, 127.4, 127.8, 128.4, 128.5, 128.7,
128.8, 128.9, 129.0, 129.1, 129.8, 129.9, 130.2, 131.6, 132.5, 132.7,
134.9, 135.3, 136.5, 136.8, 136.9, 138.7, 139.1, 139.7, 139.9, 140.9,
154.5, 156.0, 190.3, 191.4. HRMS (ESI) calcd. for C25H23O+ [M+H]+
339.1743, found 339.1748.
(2E-,4E-)/(2Z-,4E-)-3-(2,4,6-Trimethylphenyl)-5-(4-methylphenyl)-1-
phenylpenta-2,4-dien-1-one (4f): (2E-,4E-)/(2Z-,4E-)- in a ratio of
10:8. General yield of 70%. Green oil. (2E,4E)-4f: 1H NMR (400 MHz,
CDCl3), selected signals δ, ppm: 2.22 (3, 6H), 2.34 (s, 3H), 2.36 (s, 3H),
6.41 (d, J=16.1 Hz, 1H), 6.70 (s, 1H), 6.97 (s, 2H), 7.38 (d, J=8.1 Hz,
2H), 7.10–7.57 (m, 5H), 7.97–8.00 (m, 2H), 8.59 (d, J=16.1 Hz, 1H).
(2E-,4E-)/(2Z-,4E-)-1-(4-methylphenyl)-3-(2,5-dimethylphenyl)-5-
phenylpenta-2,4-dien-1-one (4j): (2E-,4E-)/(2Z-,4E-)- in a ratio of
6:10. General yield of 70%. Green oil. (2Z,4E)-4j: 1H NMR (400 MHz,
CDCl3), selected signals δ, ppm: 2.13 (s, 3H), 2.30 (s, 3H), 2.40 (s, 3H),
6.34 (d, J=15.7 Hz, 1H), 6.83 (s, 1H), 7.05–7.08 (m, 1H), 7.11–7.36 (m,
8H), 7.42 (d, J=8.2 Hz, 2H), 7.84 (d, J=8.2 Hz, 2H). (2E,4E)-4j: 1H
NMR (400 MHz, CDCl3), selected signals δ, ppm: 2.24 (s, 3H), 2.38 (s,
3H), 2.42 (s, 3H), 6.42 (d, J=16.1 Hz, 1H), 6.74 (s, 1H), 7.05 (s, 1H),
7.12–7.36 (m, 7H), 7.48 (d, J=8.2 Hz, 2H), 7.90 (d, J=8.2 Hz, 2H),
8.56 (d, J=16.1 Hz, 1H). 13C NMR (101 MHz, CDCl3) δ, ppm (for
mixture of (2E,4E)/(2Z-,4E-)-isomers): 19.2, 19.5, 21.1, 21.2, 21.7,
21.8, 123.1, 125.0, 126.9, 127.3, 127.8, 128.5, 128.6, 128.8, 128.9,
129.3, 129.4, 129.7, 129.9, 130.2, 131.8, 132.5, 132.8, 134.9, 135.3,
136.5, 136.6, 136.9, 137.0, 137.1, 138.4, 140.0, 140.5, 143.3, 191.0,
143.5, 147.7, 154.0, 154. 9, 155.6, 189.8. HRMS (ESI) calcd. for
C26H25O+ [M+H]+ 353.1900, found 353.1905.
1
(2Z,4E)-4f: H NMR (400 MHz, CDCl3), selected signals δ, ppm: 2.09
(3, 6H), 2.34 (s, 3H), 2.35 (s, 3H), 6.36 (d, J=15.8 Hz, 1H), 6.91 (s, 2H),
7.23 (s, 1H), 7.33 (d, J=8.1 Hz, 2H), 7.09–7.57 (m, 6H), 7.92–7.96 (m,
2H). 13C NMR (101 MHz, CDCl3) δ, ppm (for mixture of (2E,4E)/(2Z-
,4E-)-isomers): 191.33, 189.60, 155.68, 154.63, 139.81, 139.78, 139.34,
139.17, 138.98, 137.64, 137.18, 136.76, 136.54, 135.77, 134.77,
134.07, 133.82, 133.80, 132.61, 132.50, 129.76, 129.60, 129.51,
128.69, 128.59, 128.38, 128.32, 128.30, 128.15, 127.91, 127.40,
125.30, 124.23, 122.70, 21.50, 21.47, 21.37, 21.22, 20.01, 19.79. HRMS
(ESI) calcd. for C27H27O+ [M+H] 367.2056, found 367.2061.
+
(2E-,4E-)/(2Z-,4E-)-1,5-Diphenyl-3-(2,3,5,6-tetramethylphenyl)
penta-2,4-dien-1-one (4g): (2E-,4E-)/(2Z-,4E-)- in a ratio of 2:5.
General yield of 60%. Green oil. (2Z,4E)-4g: 1H NMR (400 MHz,
CDCl3), selected signals δ, ppm:2.00 (s, 6H), 2.24 (s, 6H), 6.33 (d, J=
15.7 Hz, 1H), 6.96 (s, 1H), 7.20 (d, J=15.7 Hz, 1H), 7.24 (s, 1H), 7.27–
7.35 (m, 3H), 7.41–7.46 (m, 4H), 7.48–7.52 (m, 1H), 7.90–7.93 (m,
2H).13C NMR (CDCl3, 100 MHz), selected signals δ, ppm: 16.4, 20.2,
(2E-,4E-)/(2Z-,4E-)-1-(4-Bromophenyl)-3-(2,5-dimethylphenyl)-5-
phenylpenta-2,4-dien-1-one (4k): (2E-,4E-)/(2Z-,4E-)- in a ratio of
10:6. General yield of 72%. Green oil. (2E,4E)-4k: 1H NMR (400 MHz,
CDCl3), selected signals δ, ppm: 2.23 (s, 3H), 2.37 (s, 3H), 6.47 (d, J=
16.1 Hz, 1H), 6.69 (s, 1H), 7.03 (s, 1H), 7.05–7.37 (m, 5H), 7.46–7.50
(m, 2H), 7.60 (d, J=8.6 Hz, 2H), 7.85 (d, J=8.6 Hz, 2H), 8.57 (d, J=
16.1 Hz, 1H). 13C NMR (101 MHz, CDCl3), selected signals δ, ppm:
19.5, 21.1, 122.0, 126.7, 127.4, 127.9, 128.8, 130.0, 132.0, 132.7,
1
155.2, 190.0. (2E,4E)-4g: H NMR (400 MHz, CDCl3), selected signals
δ, ppm: 2.13 (s, 6H), 2.29 (s, 6H), 6.41 (d, J=16.0 Hz, 1H), 8.64 (d, J=
16.0 Hz,1H). 13C NMR (CDCl3, 100 MHz), selected signals δ, ppm:
16.8, 20.2, 156.6, 191.4. 13C NMR (101 MHz, CDCl3) δ, ppm (for
mixture of (2E,4E)/(2Z-,4E-)-isomers): 123.3, 125.0, 126.6, 127.4,
127.9, 128.3, 128.4, 128.5, 128.7, 128.8, 128.9, 129.0, 129.1, 130.8,
130.9, 131.4, 131.7, 132.5, 132.7, 133.2, 133.9, 136.5, 136.6, 136.9,
137.8, 139.0, 140.0. HRMS (ESI) calcd. for C27H27O+ [M+H]+
367.2056, found 367.2061.
1
135.4, 136.7, 138.4, 139.8, 141.5, 156.9, 190.1. (2Z,4E)-4k: H NMR
(400 MHz, CDCl3), selected signals δ, ppm: 2.12 (s, 3H), 2.30 (s, 3H),
6.37 (d, J=15.8 Hz, 1H), 6.80 (s, 1H), 7.37–7.06 (m, 7H), 7.44–7.39 (m,
2H), 7.55 (d, J=8.6 Hz, 2H), 7.77 (d, J=8.6 Hz, 2H). 13C NMR
(101 MHz, CDCl3), selected signals δ, ppm: 19.1, 21.2, 124.2, 127.6,
127.8, 128.7, 128.8, 129.1, 129.8, 131.4, 132.4, 135.0, 136.4, 136.6,
137.8, 139.3, 155.2, 189.3. HRMS (ESI) calcd. for C25H22BrO+ [M+H]+
417.0849, found 417.0854.
(2E-,4E-)/(2Z-,4E-)-1-(4-Methylphenyl)-5-phenyl-3-(2,3,5,6-
tetramethylphenyl)-penta-2,4-dien-1-one (4h). (2E-,4E-)/(2Z-,4E-)-
in a ratio of 1:4. General yield of 25 mg (80%). Green oil. (2Z,4E)-
4h: H NMR (400 MHz, CDCl3), selected signals δ, ppm: 2.01 (s, 6H),
2.25 (s, 6H), 2.40 (s, 3H), 6.32 (d, J=15.7 Hz, 1H), 7.19 (d, J=15.8 Hz,
1H), 7.22 (s, 1H), 7.25–7.36 (m, 5H), 7.42–7.45 (m, 2H), 7.84 (d, J=
8.1 Hz, 2H). 13C NMR (101 MHz, CDCl3), selected signals δ, ppm: 16.4,
20.2, 21.7, 125.1, 127.4, 128.4, 128.80, 128.82, 129.3, 130.8, 131.2,
133.1, 136.4, 136.6, 136.7, 137.5, 143.2, 154.7, 189.5.
1
(2E-,4E-)/(2Z-,4E-)-1-(4-Chlorophenyl)-3-(2,5-dimethylphenyl)-5-
phenylpenta-2,4-dien-1-one (4l): (2E-,4E-)/(2Z-,4E-)- in a ratio of
1
10:7. General yield of 40%. (2E,4E)-4l: H NMR (400 MHz, CDCl3),
selected signals δ, ppm: 2.23 (s, 3H), 2.37 (s, 3H), 6.46 (d, J=16.1 Hz,
1H), 6.69 (s, 1H), 7.03 (s, 1H), 7.42–7.05 (m, 5H), 7.44 (d, J=8.6 Hz,
2H), 7.46–7.50 (m, 2H), 7.93 (d, J=8.6 Hz, 2H), 8.57 (d, J=16.1 Hz,
1
1
(2E,4E)-4h: H NMR (400 MHz, CDCl3), selected signals δ, ppm: 2.13
1H). (2Z,4E)-4l: H NMR (400 MHz, CDCl3), selected signals δ, ppm:
(s, 6H), 2.30 (s, 6H), 2.42 (s, 3H), 6.39 (d, J=16.1 Hz, 1H), 6.70 (s, 1H),
7.27–7.33 (m, 5H), 7.89 (d, J=8.2 Hz, 2H), 8.64 (d, J=16.0 Hz, 1H).
13C NMR (101 MHz, CDCl3), selected signals δ, ppm: 16.8, 20.2, 21.8,
123.5, 126.6, 127.4, 127.9, 128.6, 128.7, 129.0, 129.4, 130.9, 131.7,
2.12 (s, 3H), 2.30 (s, 3H), 6.37 (d, J=15.7 Hz, 1H), 6.80 (s, 1H), 7.05–
7.52 (m, 9H), 7.39 (d, J=8.6 Hz, 2H), 7.84 (d, J=8.6 Hz, 2H). 13C NMR
(101 MHz, CDCl3) δ, ppm (for mixture of (2E,4E)/(2Z-,4E-)-isomers):
19.2, 19.5, 21.1, 21.2, 122.1, 124.3, 126.7, 127.4, 127.9, 128.8, 128.9,
Eur. J. Org. Chem. 2021, 2634–2649
www.eurjoc.org
2644
© 2021 Wiley-VCH GmbH

Full Papers
doi.org/10.1002/ejoc.202100280
129.0, 129.1, 129.2, 129.8, 129.8, 130.3, 131.4, 132.4, 132.7, 135.0,
100 MHz) δ, ppm: 43.6, 49.6, 111.4, 121.7, 126.6, 126.8, 127.6, 127.8,
128.8, 129.0, 129.6, 132.1, 138.2, 138.7, 140.4, 144.9, 153.3, 163.6,
189.4. HRMS (ESI) calcd. for C23H18BrO+ [M+H]+ 389.0536, found
389.0539.
135.4, 136.4, 136.7, 136.7, 137.4, 138.0, 138.9, 139.1, 139.2, 139.8,
141.4, 155.1, 156.8, 189.1, 189.9. HRMS (ESI) C25H22ClO+ [M+H]+
calcd. for 373.1354, found 373.1359.
General procedure for synthesis of 1-aryl-2-(3-aryl-2,3-dihydro-
1H-inden-1-ylidene)ethan-1-ones 5a-am from enynones1 in
TfOH. TfOH (0.1 ml, 1.29 mmol) was added with vigorous stirring at
room temperature to a solution of enynone1 (0.086 mmol), arene
(0.103 mmol) in CH2Cl2 (0.1 ml), the mixture was stirred for 1–3 h.
The reaction mixture was poured into H2O (50 ml), extracted with
CHCl3 (3×25 ml). The combined extracts were consequently
washed with H2O (50 ml), saturated aqueous solution of NaH-
CO3(25 ml), again with H2O (25 ml) and dried with Na2SO4. The
solvent was removed under reduced pressure, the product was
isolated by preparative TLC on LS 5/40 μm silica gel plates, eluent
petroleum ether-EtOAc, 95:5, vol. The separated fractions were
washed off from the sorbent with CH2Cl2.
(E)-1-(4-Nitrophenyl)-2-(3-phenyl-2,3-dihydro-1H-inden-1-ylidene)
1
ethan-1-one (5e): Yield 15 mg (60%). Brown oil. H NMR (400 MHz,
CDCl3) δ, ppm: 3.43 (ddd, 4J=2.4, 3J=3.6, 2J=20.5 Hz, 1H), 4.07
4
3
2
3
3
(ddd, J=2.4, J=8.0, J=20.5 Hz, 1H), 4.57 (dd, J=3.6, J=8.0 Hz,
1H), 7.12–7.14 (m, 2H), 7.21–7.25 (m, 2H), 7.28–7.32 (m, 2H), 7.36–
7.48 (m, 2H), 7.51 (t, J4 =2.4 Hz, 1H), 8.16 (d, J=8.8 Hz, 2H), 8.34 (d,
J=8.8 Hz, 2H). 13C NMR (CDCl3, 100 MHz) δ, ppm: 43.8, 49.5, 111.1,
121.8, 123.9, 126.7, 126.9, 127.7, 127.8, 128.9, 129.1, 132.6, 140.1,
144.6, 144.7, 149.9, 153.7, 165.6, 188.8. HRMS (ESI) calcd. for
+
C23H18NO3 [M+H]+ 356.1281; found 356.1286.
(E)-2-(3-(4-Methylphenyl)-2,3-dihydro-1H-inden-1-ylidene)-1-
phenyl-ethan-1-one (5f): Yield 15 mg (56%). Brown oil. 1H NMR
4
3
(400 MHz, CDCl3) δ, ppm: 2.32 (s, 3H), 3.41 (ddd, J=2.5, J=3.9,
4
3
2
1-Phenyl-2-(3-phenyl-2,3-dihydro-1H-inden-1-ylidene)ethan-1-
one (5a): E-/Z-5a in a ratio of5:1. General yield of 16 mg (60%).
2J=20.3 Hz, 1H), 4.04 (ddd, J=2.5, J=8.1, J=20.3 Hz, 1H), 4.51
(dd, 3J=3.9, 3J=8.1 Hz, 1H), 6.84 (s, 1H), 7.03 (d, J=8.0 Hz, 2H), 7.10
(d, J=8.0 Hz, 2H), 7.17–7.19 (m, 1H), 7.33–7.40 (m, 2H), 7.50 (d, J=
7.6 Hz, 2H), 7.54–7.56 (m, 2H), 7.81–7.83 (m, 1H), 8.02–8.04 (m,
2H).13C NMR (100 MHz, CDCl3) δ, ppm: 21.0, 43.4, 49.1, 111.7, 121.4,
126.4, 127.3, 127.6, 128.7, 128.0, 128.5, 129.3, 131.7, 132.2, 136.1,
139.7, 140.4, 141.9, 153.2, 162.8, 190.7. HRMS (ESI) calcd. for
C24H21O+ [M+H]+ 325.1587, found 325.1592.
1
Yellow oil. E-5a: H NMR (400 MHz, CDCl3), selected signals δ, ppm:
4
3
2
4
3
3.44 (ddd, J=2.5, J=4.0, J=20.3 Hz, 1H), 4.07 (ddd, J=2.5, J=
2
3
3
8.2, J=20.3 Hz, 1H), 4.55 (dd, J=4.0, J=8.21 Hz, 1H), 7.13–7.15
(m, 2H), 7.19–7.24 (m, 1H), 7.26–7.33 (m, 3H), 7.34–7.42 (m, 2H),
7.47–7.52 (m, 2H), 7.54–7.58 (m, 2H), 7.82–7.84 (m, 1H), 8.04–8.06
(m, 2H). 13C NMR (CDCl3, 100 MHz), selected signals δ, ppm: 43.4,
49.6, 111.9, 121.6, 126.5, 126.7, 127.6, 127.8, 128.1, 128.7, 128.8,
131.8, 132.4, 139.8, 140.6, 145.0, 153.1, 162.8, 190.8. Z-5a: H NMR
(400 MHz, CDCl3), selected signals δ, ppm: 3.55 (ddd, J=17.2, J=
8.0, J=1.9 Hz, 1H), 4.47 (dd, J=5.2, J=8.0 Hz, 1H), 7.00 (t, J=
1.9 Hz, 1H). HRMS (ESI) calcd. for C23H19O+ [M+H]+ 311.1430; found
311.1433.
(E)-2-(3-(4-Chlorophenyl)-2,3-dihydro-1H-inden-1-ylidene)-1-phe-
nylethan-1-one (5g): Yield 15 mg (57%).Green oil.1H NMR
(400 MHz, CDCl3) δ, ppm: 3.40 (ddd, 4J=2.5, 3J=3.9, 2J=20.2 Hz,
1
2
3
4
3
3
4
4
3
2
3
1H), 4.05 (ddd, J=2.5, J=8.2, J=20.2 Hz, 1H), 4.52 (dd, J=3.9,
3J=8.2 Hz, 1H), 7.06 (d, J=8.4 Hz, 2H), 7.17–7.22 (m, 1H), 7.26 (d,
J=8.4 Hz, 2H), 7.36–7.40 (m, 2H), 7.50–7.55 (m, 3H), 7.56 (t, 4J=
2.5 Hz, 1H) 7.82–7.84 (m, 1H), 8.03–8.05 (m, 2H). 13C NMR (100 MHz,
CDCl3) δ, ppm: 43.3, 48.9, 112.1, 121.7, 126.4, 127.8, 128.1, 128.7,
129.0, 129.2, 131.9, 132.4, 132.5, 139.7, 140.5, 143.6, 152.5, 162.3,
190.8. HRMS (MALDI) calcd. for C23H18ClO+ [M+H]+ 345.1041 found
345.1044.
(E)-1-(4-Methylphenyl)2-(3-phenyl-2,3-dihydro-1H-inden-1-
ylidene)-ethan-1-one (5b): Yield 20 mg (77%). Yellow crystals. M.p.
1
°
133–135 C. The structure was confirmed by X-ray analysis. H NMR
4
3
(400 MHz, CDCl3) δ, ppm: 2.43 (s, 3H), 3.43 (ddd, J=2.5, J=3.9,
2J=20.2 Hz, 1H), 4.06 (ddd, J=2.5, J=8.2, J=20.2 Hz, 1H), 4.55
4
3
2
3
3
(dd, J=3.9, J=8.2 Hz, 1H), 7.13–7.15 (m, 2H), 7.17–7.23 (m, 2H),
(E)-2-(3-(4-Bromophenyl)-2,3-dihydro-1H-inden-1-ylidene)-1-phe-
4
7.27–7.31 (m, 4H), 7.32–7.40 (m, 2H), 7.55 (t, J=2.5 Hz, 1H), 7.82–
1
nylethan-1-one (5h): Yield 24 mg (96%). Brown oil. H NMR (400
7.84 (m, 1H), 7.94–7.97 (d, J=8.2 Hz, 2H). 13C NMR (100 MHz, CDCl3)
δ, ppm: 21.7, 43.4, 49.6, 112.0, 121.6, 126.5, 126.7, 127.5, 127.8,
128.2, 128.8, 129.4, 131.7, 137.3, 140.6, 143.0, 145.1, 152.9, 162.3,
190.4. HRMS (ESI) calcd. for C24H21O+ [M+H]+ 325.1587, found
325.1590.
MHz, CDCl3) δ, ppm: 3.40 (ddd, 4J=2.5, 3J=3.9, 2J=20.2 Hz, 1H),
4
3
2
3
3
4.05 (ddd, J=2.5, J=8.2, J=20.2 Hz, 1H), 4.52 (dd, J=3.9, J=
8.2 Hz, 1H), 7.06 (d, J=8.4 Hz, 2H), 7.17–7.22 (m, 1H), 7.26 (d, J=
4
8.4 Hz, 2H), 7.36–7.40 (m, 2H), 7.50–7.55 (m, 3H), 7.56 (t, J=2.5 Hz,
1H) 7.82–7.84 (m, 1H), 8.03–8.05 (m, 2H). 13C NMR (100 MHz, CDCl3)
δ, ppm: 43.3, 48.9, 112.1, 121.7, 126.4, 127.8, 128.1, 128.7, 129.0,
129.2, 131.9, 132.4, 132.5, 139.7, 140.5, 143.6, 152.5, 162.3, 190.8.
HRMS (MALDI) calcd. for C23H18BrO+ [M+H]+ 389.0536 found
389.0541.
(E)-1-(4-Chlorophenyl)-2-(3-phenyl-2,3-dihydro-1H-inden-1-
ylidene)ethan-1-one (5c): Yield 21 mg (80%).Yellow crystals. M.p.
1
°
159–161 C. The structure was confirmed by X-ray analysis. H NMR
(400 MHz, CDCl3) δ, ppm: 3.42 (ddd, 4J=2.5, 3J=3.8, 2J=20.3 Hz,
4
3
2
3
1H), 4.04 (ddd, J=2.5, J=8.1, J=20.3 Hz, 1H), 4.55 (dd, J=3.8,
3J=8.1 Hz, 1H), 7.12–7.14 (m, 2H), 7.18–7.24 (m, 2H), 7.27–7.31 (m,
2H), 7.34–7.42 (m, 2H), 7.47 (d, J=8.6 Hz, 2H), 7.50 (t, 4J=2.5 Hz,1H),
7.82 (d, J=7.1 Hz, 1H), 7.98 (d, J=8.6 Hz, 2H). 13C NMR (100 MHz,
CDCl3) δ, ppm: 43.6, 49.6, 111.4, 121.7, 126.6, 126.8, 127.6, 127.8,
128.8, 129.0, 129.6, 132.1, 138.2, 138.7, 140.4, 144.9, 153.3, 163.6,
189.4. HRMS (MALDI) calcd. for C23H18ClO+ [M+H]+ 345.1041 found
345.1044.
(E)-1-(5-Bromofuran-2-yl)-2-(3-phenyl-2,3-dihydro-1H-inden-1-
ylidene)ethan-1-one (5i): Yield 25 mg (98%). Brown oil. 1H NMR
4
3
2
(400 MHz, CDCl3) δ, ppm: 3.41 (ddd, J=2.5, J=3.7, J=20.4 Hz,
4
3
2
3
1H), 4.05 (ddd, J=2.5, J=8.1, J=20.4 Hz, 1H), 4.53 (dd, J=3.7,
3J=8.1 Hz, 1H), 6.51 (d, 3J=3.5 Hz, 1H), 7.11–7.13 (m, 2H), 7.17–7.19
(m, 1H), 7.19 (d, 3J=3.5 Hz, 1H), 7.21–7.23 (m, 1H), 7.27–7.30 (m,
2H), 7.34–7.41 (m, 3H), 7.84–7.86 (m, 2H). 13C NMR (100 MHz, CDCl3)
δ, ppm: 43.4, 49.6, 110.7, 114.6, 117.9, 122.0, 126.5, 126.8, 127.0,
127.6, 127.8, 128.8, 132.1, 140.3, 144.9, 153.3, 156.6, 163.8, 177.8.
(E)-1-(4-Bromophenyl)-2-(3-phenyl-2,3-dihydro-1H-inden-1-
+
ylidene)ethan-1-one (5d): Yield 18 mg (72%). Yellow crystals. M.p.
HRMS (ESI) calcd. for C21H16BrO2 [M+H]+ 379.0328, found
1
°
132–135 C. The structure was confirmed by X-ray analysis. H NMR
379.0332.
(CDCl3, 400 MHz) δ, ppm: 3.41 (ddd, 4J=2.5, 3J=3.8, 2J=20.3 Hz,
2-(4,7-Dimethyl-3-phenyl-2,3-dihydro-1H-inden-1-ylidene)-1-phe-
nylethan-1-one (5j): E-/Z-5 in a ratio of 3:1. General yield of 20 mg
(60%). Yellow oil. E-5j: 1H NMR (400 MHz, CDCl3), selected signals δ,
4
3
2
3
1H), 4.04 (ddd, J=2.5, J=8.1, J=20.3 Hz, 1H), 4.55 (dd, J=3.8,
3J=8.1 Hz, 1H), 7.12–7.14 (m, 2H), 7.18–7.23 (m, 2H), 7.27–7.31 (m,
4
2H), 7.36–7.40 (m, 2H), 7.49 (t, J=2.5 Hz, 1H), 7.63 (d, J=8.6 Hz,
4
3
2
ppm: 1.99 (s, 3H), 2.7 (s, 3H), 3.50 (dt, J=2.2, J=2.2, J=19.8 Hz,
2H), 7.81–7.83 (m, 1H), 7.90 (d, J=8.6 Hz, 2H). 13C NMR (CDCl3,
4
3
2
3
1H), 3.90 (ddd, J=2.2, J=8.6, J=19.8, Hz, 1H), 4.52 (dd, J=8.6,
Eur. J. Org. Chem. 2021, 2634–2649
www.eurjoc.org
2645
© 2021 Wiley-VCH GmbH

Full Papers
doi.org/10.1002/ejoc.202100280
4
3J=2.2 Hz, 1H), 7.59 (t, J=2.2 Hz, 1H). 13C NMR (CDCl3, 100 MHz),
selected signals δ, ppm: 18.9, 22.5, 44.5, 48.6, 116.2, 126.3, 127.4,
128.1, 128.7, 128.7, 131.0, 132.22, 132.4, 133.4, 133.6, 138.9, 140.2,
4J=2.3 Hz, 1H), 8.10 (d, J=8.8 Hz, 2H), 8.32 (d, J=8.8 Hz, 2H). 13C
NMR (CDCl3, 100 MHz) δ, ppm: 18.9, 22.5, 44.9, 48.5, 115.2, 124.0,
126.5, 127.4, 128.8, 129.0, 131.3, 133.2, 133.7, 133.9, 138.4, 144.9,
1
+
145.2, 151.9, 164.6, 191.1. Z-5j: H NMR (400 MHz, CDCl3), selected
145.1, 149.8, 152.5, 167.6, 189.1. HRMS (ESI) C25H21NNaO3 [M+Na]
signals δ, ppm: 2.30 (s, 3H), 2.71 (s, 3H), 3.40–3.46 (m, 1H), 4.01–4.09
(m, 1H), 4.41–4.44 (m, 1H). 13C NMR (CDCl3, 100 MHz), selected
signals δ, ppm: 21.5, 22.4, 44.1, 49.1, 115.1, 124.5, 126.5, 127.8,
128.6, 131.5, 132.0, 140.1, 141.4, 145.3, 154.6, 154.6, 164.0. HRMS
(ESI) C25H23O+ [M+H]+calcd. for 339.1743, found 339.1748.
calcd. for 406.1419, found 406.1412.
(E)-2-(4,7-Dimethyl-3-(4-methylphenyl)-2,3-dihydro-1H-inden-1-
ylidene)-1-phenylethan-1-one (5o): Yield 20 mg (70%). Green oil.
1H NMR (CDCl3, 400 MHz) δ, ppm: 2.00 (s, 3H), 2.29 (s, 3H), 2.73 (s,
4
3
2
4
3H), 3.49 (dt, J=2.0, J=2.4, J=19.7 Hz, 1H), 3.89 (ddd, J=2.4,
2
3
3
(E)-2-(4,7-Dimethyl-3-phenyl-2,3-dihydro-1H-inden-1-ylidene)-1-
(4-methylphenyl)ethan-1-one (5k): E-/Z-5k in a ratio of 5:1.
3J=8.5, J=19.7 Hz, 1H), 4.49 (dd, J=2.0, J=8.5 Hz, 1H), 6.90 (d,
J=8.0 Hz, 2H), 7.03 (d, J=8.0 Hz, 2H), 7.08–7.13 (m, 2H), 7.46–7.50
(m, 2H), 7.52–7.56 (m, 2H), 7.59 (t, J4 =2.4 Hz, 1H), 7.98–8.00 (m, 2H).
13C NMR (CDCl3, 101 MHz) δ, ppm: 18.9, 21.1, 22.4, 44.6, 48.1, 116.2,
127.3, 128.1, 128.6, 129.3, 130.9, 132.2, 132.4, 133.4, 133.6, 135.7,
138.8, 140.2, 142.2, 152.0, 164.8, 191.1. HRMS (ESI) C26H25O+ [M+
H]+calcd. for 353.1900, found 353.1905.
1
General yield of 14 mg (50%). Yellow oil. E-5k: H NMR (400 MHz,
CDCl3), selected signals δ, ppm: 1.98 (s, 3H), 2.42 (s, 3H), 2.73 (s, 3H),
3.44 (dt, 4J=2.3, 3J=2.3, 2J=19.7 Hz, 1H), 3.89 (ddd, 4J=2.3, 3J=8.6,
2J=19.7 Hz, 1H), 4.51 (dd, 3J=2.3, 3J=8.6 Hz, 1H), 6.99–7.01 (m, 2H),
7.08–7.10 (m, 1H), 7.12–7.16 (m, 2H), 7.19–7.3 (m, 2H), 7.26–7.28 (m,
4
2H), 7.57 (t, J=2.3 Hz, 1H), 7.89 (d, J=8.1 Hz, 2H). 13C NMR (CDCl3,
2-(3-(4-Chlorophenyl)-4,7-dimethyl-2,3-dihydro-1H-inden-1-
ylidene)-1-phenylethan-1-one (5p):E-/Z-5p in
100 MHz), selected signals δ, ppm: 18.9, 21.7, 22.4, 44.4, 48.6, 116.3,
126.3, 127.4, 128.3, 128.7, 129.4, 131.0, 132.3, 133.3, 133.6, 137.6,
138.9, 142.9, 151.3, 151.8, 164.1, 190.9. HRMS (ESI) C26H25O+ [M+
H]+calcd. for 353.1900, found 353.1903. Z-5k: 1H NMR (400 MHz,
CDCl3), selected signals δ, ppm: 3.42 (m, 1H), 4.04 (m, 1H), 4.42 (m,
1H), 7.57 (m, 1H). 13C NMR (CDCl3, 100 MHz), selected signals δ,
ppm: 21.6, 22.5, 44.1, 49.3, 115.4. HRMS (ESI) C26H25O+ [M+H]+
calcd. for 353.1900, found 353.1903.
a ratio of 5:1.
1
General yield of 18 mg (66%). Green oil. E-5p: H NMR (400 MHz,
CDCl3), selected signals δ, ppm: 1.98 (s, 3H), 2.72 (s, 3H), 3.46 (dt,
4J=2.1, 3J=2.1, 2J=19.6 Hz, 1H), 3.88 (ddd, 4J=2.1, 3J=8.6, 2J=
19.6 Hz, 1H), 4.49 (dd, 3J=2.1, 3J=8.6 Hz, 1H), 6.94 (d, J=8.4 Hz,
2H), 7.07–7.14 (m, 2H), 7.19 (d, J=8.4 Hz, 2H), 7.46–7.50 (m, 2H),
7.53–7.55 (m, 1H), 7.59 (t, 4J=2.3 Hz, 1H), 7.97–7.99 (m, 2H). 13C
NMR (CDCl3, 100 MHz), selected signals δ, ppm: 18.9, 22.4, 44.3,
47.9, 116.4, 128.1, 128.7, 128.8, 128.9, 129.1, 131.2, 132.3, 132.5,
1-(4-Chlorophenyl)-2-(4,7-dimethyl-3-phenyl-2,3-dihydro-1H-in-
den-1-ylidene)ethan-1-one 5l:. E-/Z-5l in a ratio of 5:1. General
1
133.5, 133.6, 138.8, 140.1, 143.8, 151.3, 164.0, 191.2. Z-5p: H NMR
1
yield of 18 mg (65%). Yellow oil. E-5l: H NMR (400 MHz, CDCl3),
(400 MHz, CDCl3), selected signals δ, ppm:1.94 (s, 3H), 2.70 (s, 3H),
4
3
2
selected signals δ, ppm:1.98 (s, 3H), 2.72 (s, 3H), 3.48 (dt, J=2.3,
3.35–3.41 (m, 1H), 4.03 (ddd, 3J=2.5, J=8.5, J=19.6 Hz, 1H), 4.39–
4.41 (m, 1H). 13C NMR (101 MHz, CDCl3) selected signals δ, ppm:
18.5, 22.3, 44.3, 47.6, 120.0, 191.9. HRMS (MALDI) cald. for
C25H22ClO+ [M+H]+ 373.1354, found 373.1356.
3J=2.3, 2J=19.7 Hz, 1H), 3.88 (ddd, 4J=2.3, 3J=8.6, 2J=19.7 Hz,
3
3
1H), 4.51 (dd, J=2.3, J=8.6 Hz, 1H), 6.98–7.00 (m, 2H), 7.09–7.11
(m, 2H), 7.13–7.17 (m, 1H), 7.20–7.23 (m, 2H), 7.44 (d, J=8.6 Hz, 2H),
4
7.52 (t, J=2.3 Hz, 1H), 7.91 (d, J=8.6 Hz, 2H). 13C NMR (CDCl3, 100
(E)-1-(5-Bromofuran-2-yl)-2-(4,7-dimethyl-3-phenyl-2,3-dihydro-
1H-inden-1-ylidene)ethan-1-one (5q): E-/Z-5q in a ratio of 5:1.
General yield of 16 mg (70%). Green oil. E-5q: H NMR (400 MHz,
MHz), selected signals δ, ppm: 18.9, 22.5, 44.5, 48.5, 115.6, 126.4,
127.4, 128.7, 128.9, 129.5, 131.1, 132.6, 133.5, 133.7, 138.4, 138.7,
1
1
142.9, 145.1, 152.0, 165.5, 189.7. (Z)-5l: H NMR (400 MHz, CDCl3),
CDCl3), selected signals δ, ppm: 1.98 (s, 3H), 2.72 (s, 3H), 3.51 (dt,
selected signals δ, ppm: 2.05 (s, 3H), 2.70 (s, 3H), 3.38–3.44 (m, 1H),
4J=2.3, 3J=1.8, 2J=19.9 Hz, 1H), 3.87 (ddd, (4J=2.3, 3J=8.5, 2J=
3
3
2
4.03 (ddd, J=2.1, J=8.2, J=19.6 Hz, 1H), 4.41–4.45 (m, 1H). 13C
NMR (CDCl3, 100 MHz), selected signals δ, ppm: 18.5, 22.3, 44.3,
48.2, 164.9, 190.8. HRMS (MALDI) calcd. for C25H22ClO+ [M+H]+
373.1354, found 373.1356.
3
3
3
19.8 Hz, 1H), 4.50 (dd, J=1.8, J=8.5 Hz, 1H), 6.48 (d, J=3.5 Hz,
3
1H), 6.97–7.00 (m, 2H), 7.10 (d, J=3.4 Hz, 2H), 7.12 (d, J=3.5 Hz,
1H), 7.14–7.17 (m, 1H), 7.19–7.23 (m, 2H), 7.43 (t, 4J=2.3 Hz, 1H). 13
C
NMR (101 MHz, CDCl3) selected signals δ, ppm: 18.9, 22.3, 44.4,
1-(4-Bromophenyl)-2-(4,7-dimethyl-3-phenyl-2,3-dihydro-1H-in-
den-1-ylidene)ethan-1-one (5m): E-/Z-5m in a ratio of 5:1. General
48.59, 114.5, 114.7, 117.6, 126.3, 127.4, 128.7, 128.8, 131.1, 132.7,
133.6, 133.8, 138.6, 145.1, 152.1, 156.8, 165.6, 178.1. Z-5q: H NMR
1
1
yield of 17 mg (65%). Yellow oil. E-5m: H NMR (400 MHz, CDCl3),
(400 MHz, CDCl3), selected signals δ, ppm: 1.98 (s, 3H), 2.73 (s, 3H),
4
4
3
2
3
3
selected signals δ, ppm:1.98 (s, 3H), 2.71 (s, 3H), 3.48 (dt, J=2.3,
3.42 (ddd, J=2.3, J=4.0, J=19.8 Hz, 1H), 4.04 (ddd, J=2.3, J=
2 3 3 4
3J=2.3, 2J=19.8 Hz, 1H), 3.88 (ddd, 4J=2.3, 3J=8.5, 2J=19.8 Hz,
8.1, J=19.8 Hz, 1H), 4.42 (dd, J=4.0, J=8.1 Hz, 1H), 7.38 (t, J=
2.3 Hz, 1H). HRMS (MALDI) cald. for C23H20BrO+ [M+H]+ 407.0641,
found 407.0646.
3
3
1H), 4.51 (dd, J=2.3, J=8.5 Hz, 1H), 6.98–7.00 (m, 2H), 7.10–7.11
(m, 2H), 7.12–7.17 (m, 1H), 7.20–7.23 (m, 2H), 7.51 (t, 4J=2.3 Hz, 1H),
7.61 (d, J=8.6 Hz, 2H), 7.84 (d, J=8.6 Hz, 2H). 13C NMR (CDCl3, 100
MHz), selected signals δ, ppm: 18.9, 22.5, 44.6, 48.5, 115.6, 126.4,
127.4, 128.7, 129.7, 131.1, 132.0, 132.6, 133.5, 133.7, 138.7, 138.9,
145.1, 152.1, 165.6, 189.9.
(E)-2-(5,7-Dimethyl-3-phenyl-2,3-dihydro-1H-inden-1-ylidene)-1-
phenylethan-1-one (5r): Yield 11 mg (45%). Green oil. 1H NMR
(CDCl3, 400 MHz) δ, ppm: 2.30 (s, 3H), 2.70 (s, 3H), 3.43 (ddd, 4J=2.5,
3J=4.0, 2J=20.3 Hz, 1H), 4.07 (ddd, 4J=2.5, 3J=8.2, 2J=20.3 Hz,
1H), 4.55 (dd, 3J=4.0, 3J=8.21 Hz, 1H), 6.83 (s, 1H), 6.97 (s, 1H),
7.12–7.14 (m, 2H), 7.21–7.23 (m, 1H), 7.27–7.28 (m, 2H), 7.47–7.56
(m, 4H), 7.98–8.00 (m, 2H). 13C NMR (CDCl3, 100 MHz) δ, ppm: 21.6,
22.5, 44.2, 49.3, 115.3, 124.7, 126.6, 128.0, 128.1, 128.7, 128.7, 131.7,
132.2, 135.9, 136.0, 140.3, 141.6, 145.4, 154.8, 164.1, 191.2. HRMS
(ESI) C25H23O+ [M+H]+calcd. for 339.1743, found 339.1746.
1
Z-5m: H NMR (400 MHz, CDCl3), selected signals δ, ppm: 3.38–3.44
4
3
2
3
(m, 1H), 4.03 (ddd, J=2.2, J=8.1, J=19.6 Hz, 1H), 4.43 (dd, J=
4.2, 3J=8.1 Hz, 1H), 7.46 (t, 4J=2.2 Hz, 1H). 13C NMR (101 MHz,
CDCl3) selected signals δ, ppm: 21.7, 44.3, 48.5, 114.6. HRMS
(MALDI) calcd. for C25H22BrO+ [M+H]+ 417.0849, found 417.0852.
(E)1-(4-Nitrorophenyl)-2-(4,7-dimethyl-3-phenyl-2,3-dihydro-1H-
inden-1-ylidene)ethan-1-one (5n): Yield 14 mg (50%). Green oil. 1H
NMR (CDCl3, 400 MHz) δ, ppm: 1.98 (s, 3H), 2.73 (s, 3H), 3.50 (dt, 4J=
(E)-2-(5,7-Dimethyl-3-phenyl-2,3-dihydro-1H-inden-1-ylidene)-1-
(4-methylphenyl)ethan-1-one (5s): Yield 25 mg (86%). Green oil.
1H NMR (CDCl3, 400 MHz) δ, ppm: 2.30 (s, 3H), 2.43 (s, 3H), 2.70 (s,
3
2.3, 3J=2.0, 2J=20.0 Hz, 1H), 3.91 (ddd, 4J=2.3, J=8.6, 2J=20.0 Hz,
3
3
4
3
2
4
1H), 4.54 (dd, J=2.3, J=8.6 Hz, 1H), 6.98–7.00 (m, 2H), 7.09–7.11
3H), 3.43 (ddd, J=2.2, J=4.0, J=19.6 Hz, 1H), 4.04 (ddd, J=2.2,
2 3 3
(m, 2H), 7.13 (s, 1H), 7.16–7.18 (m, 2H), 7.21–7.24 (m, 2H), 7.54 (t,
3J=8.21, J=19.6 Hz, 1H), 4.42 (dd, J=4.0, J=8. 1 Hz, 1H), 6.83 (s,
Eur. J. Org. Chem. 2021, 2634–2649
www.eurjoc.org
2646
© 2021 Wiley-VCH GmbH

Full Papers
doi.org/10.1002/ejoc.202100280
1
1H), 6.97 (s, 1H), 7.14 (d, J=7.6 Hz, 2H), 7.19–7.23 (m, 1H), 7.52 (t,
oil. H NMR (CDCl3, 400 MHz) δ, ppm: 2.29 (s, 3H), 2.70 (s, 3H), 3.42
4
3
2
4
3
4J=2.2 Hz, 1H), 7.91 (d, J=8.0 Hz, 2H). 13C NMR (CDCl3, 100 MHz) δ,
ppm: 21.6, 21.7, 22.5, 44.1, 49.3, 115.4, 124.6, 126.6, 127.9, 128.2,
128.7, 129.4, 131.6, 135.8, 136.1, 137.7, 141.4, 142.8, 145.5, 154.6,
163.5,190.9. HRMS (ESI) C26H25O+ [M+H]+calcd. for 353.1900, found
353.1903.
(ddd, J=2.3, J=4.1, J=19.8 Hz, 1H), 4.04 (ddd, J=2.3, J=8.2,
2J=19.8 Hz, 1H), 4.42 (dd, 3J=4.1, 3J=8.2 Hz, 1H), 6.49 (d, 3J=
3
3.6 Hz, 1H), 6.82 (s, 1H), 6.97 (s, 1H), 7.11–7.13 (m, 2H), 7.14 (d, J=
4
3.6 Hz, 1H), 7.19–7.23 (m, 1H), 7.27–7.30 (m, 2H), 7.38 (t, J=2.3 Hz,
1H). 13C NMR (CDCl3, 100 MHz) δ, ppm: 21.7, 22.3, 44.1, 49.3, 113.7,
114.5, 117.6, 124.6, 126.6, 126.8, 127.9, 128.7, 131.7, 135.7, 136.2,
142.0, 145.3, 155.0, 156.9, 165.1, 178.1. HRMS (ESI) cald. for
C23H20BrO+ [M+H]+ 407.0641, found 407.0644.
(E)-1-(4-Chlorophenyl)-2-(5,7-dimethyl-3-phenyl-2,3-dihydro-1H-
1
inden-1-ylidene)ethan-1-one (5t): Yield 17 mg (60%). Green oil. H
NMR (CDCl3, 400 MHz) δ, ppm: 2.30 (s, 3H), 2.70 (s, 3H), 3.43 (ddd,
4J=2.3, 3J=4.1, 2J=19.6 Hz, 1H), 4.04 (ddd, 4J=2.3, 3J=8.1, 2J=
(E)-1-Phenyl-2-(4,5,7-trimethyl-3-phenyl-2,3-dihydro-1H-inden-1-
ylidene)ethan-1-one (5z):Yield 21 mg (70%). Yellow crystals. M.p.
128–130 C. The structure was confirmed by X-ray analysis. H NMR
3
3
19.6 Hz, 1H), 4.43 (dd, J=4.1, J=8.1 Hz, 1H), 6.84 (s, 1H), 6.98 (s,
1
°
1H), 7.12–7.14 (m, 2H), 7.22–7.24 (m, 1H), 7.27–7.32 (m, 2H), 7.46 (d,
4
J=8.5 Hz, 2H), 7.47 (t, J=2.3 Hz, 1H), 7.94 (d, J=8.5 Hz, 2H). 13C
(CDCl3, 400 MHz) δ, ppm: 1.93 (s, 3H), 2.27 (s, 3H), 2.70 (s, 3H), 3.52
(dt, 4J=2.3, 3J=2.3, 2J=19.7 Hz, 1H), 3.89 (ddd, 4J=2.3, 3J=8.61,
2J=19.7 Hz, 1H), 4.55 (dd, 3J=2.3, 3J=8.61 Hz, 1H), 6.98–7.00 (m,
2H), 7.02 (s, 1H), 7.12–7.16 (m, 1H), 7.19–7.23 (m, 2H), 7.45–7.49 (m,
2H), 7.51–7.55 (m, 2H), 7.97–7.99 (m, 2H). 13C NMR (CDCl3, 100 MHz)
δ, ppm: 15.5, 20.1, 22.3, 44.8, 48.7, 115.3, 126.2, 127.4, 128.1, 128.6,
128.7, 132.0, 132.1, 133.0, 133.1, 136.9, 140.3, 140.4, 145.8, 152.3,
165.0, 191.1. HRMS (ESI) C26H25O+ [M+H]+calcd. for 353.1900,
found 353.1904.
NMR (CDCl3, 100 MHz) δ, ppm: 21.6, 22.5, 44.3, 49.2, 114.7, 124.7,
126.7, 127.9, 128.7, 128.9, 129.5, 131.7, 135.8, 138.5, 138.6, 141.8,
141.6, 145.3, 155.0, 164.9, 189.8. HRMS (MALDI) C25H22ClO+ [M+H]+
calcd. for 373.1354, found 373.1356.
(E)-1-(4-Bromophenyl)-2-(5,7-dimethyl-3-phenyl-2,3-dihydro-1H-
inden-1-ylidene)ethan-1-one (5u): Yield 16 mg (60%). Green oil. 1H
NMR (CDCl3, 400 MHz) δ, ppm: 2.30 (s, 3H), 2.70 (s, 3H), 3.42 (ddd,
4J=2.3, 3J=4.2, 2J=19.7 Hz, 1H), 4.03 (ddd, 4J=2.3, 3J=8.1, 2J=
3
3
19.7 Hz, 1H), 4.43 (dd, J=4.2, J=8.1 Hz, 1H), 6.83 (s, 1H), 6.98 (s,
1H), 7.11–7.14 (m, 2H), 7.20–7.24 (m, 1H), 7.27–7.31 (m, 2H), 7.47 (t,
4J=2.3 Hz, 1H), 7.62 (d, J=8.6 Hz, 2H), 7.86 (d, J=8.6 Hz, 2H). 13C
NMR (CDCl3, 100 MHz) δ, ppm: 21.7, 22.5, 44.3, 49.2, 114.6, 124.7,
126.7, 127.1, 127.9, 128.8, 129.7, 131.7, 131.9, 135.8, 135.9, 139.0,
141.9, 145.3, 155.0, 165.0, 190.0. HRMS (MALDI) calcd. for
C25H22BrO+ [M+H]+ 417.0849, found 417.0854.
(E)-1-(4-Methylphenyl)-2-(4,5,7-trimethyl-3-phenyl-2,3-dihydro-
1H-inden-1-ylidene)ethan-1-one (5aa):Yield 24 mg (80%). Yellow
crystals. M.p. 135–137 C. The structure was confirmed by X-ray
analysis. H NMR (CDCl3, 400 MHz) δ, ppm: 1.92 (s, 3H), 2.27 (s, 3H),
2.42 (s, 3H), 2.70 (s, 3H), 3.51 (dt, J=2.3, J=2.3, J=19.6, 1H), 3.87
(ddd, J=2.3, J=8.6, J=19.6 Hz, 1H), 4.55 (dd, J=2.0, J=8.6 Hz,
1H), 6.98–7.99 (m, 2H), 7.02 (s, 1H), 7.11–7.15 (m, 1H), 7.19–7.22 (m,
°
1
4
3
2
4
3
2
3
3
4
2H), 7.26–7.28 (m, 2H), 7.52 (t, J=2.3 Hz, 1H), 7.89 (d, J=8.2 Hz,
(E)-2-(5,7-Dimethyl-3-phenyl-2,3-dihydro-1H-inden-1-ylidene)-1-
2H). 13C NMR (CDCl3, 100 MHz) δ, ppm: 15.5, 20.05, 21.71, 22.3, 44.7,
48.7, 115.4, 126.2, 127.4, 128.2, 128.7, 129.3, 131.9, 132.9, 133.0,
137.0, 137.7, 140.2, 142.7, 145.8, 152.1, 164.4, 190.8. HRMS (ESI)
C27H27O+ [M+H]+cald. for 367.2056, found 367.2060.
1
(4-nitrophenyl)ethan-1-one (5v): Yield 17 mg (63%). Brown oil. H
NMR (CDCl3, 400 MHz) δ, ppm.: 2.31 (s, 3H), 2.71 (s, 3H), 3.44 (ddd,
4J=2.2, 3J=4.0, 2J=19.9 Hz, 1H), 4.06 (ddd, 4J=2.2, 3J=8.0, 2J=
3
3
19.9 Hz, 1H), 4. 45 (dd, J=4.0, J=8.0 Hz, 1H), 6.85 (s, 1H), 6.99 (s,
1H), 7.11–7.13 (m, 2H), 7.21–7.24 (m, 1H), 7.28–7.31 (m, 2H), 7.49 (t,
J4 =2.2 Hz, 1H), 8.11 (d, J=8.8 Hz, 2H), 8.33 (d, J=8.8 Hz, 2H). 13C
NMR (CDCl3, 100 MHz) δ, ppm: 21.6, 22.4, 44.5, 49.1, 114.1, 123.8,
124.7, 126.6, 127.8, 128.7, 128.8, 131.7, 135.5, 136.0, 142.4, 144.9,
(E)-1-(4-Chlorophenyl)-2-(4,5,7-trimethyl-3-phenyl-2,3-dihydro-
1H-inden-1-ylidene)ethan-1-one (5ab):Yield 17 mg (60%). Yellow
°
crystals. M.p. 171–174 C. The structure was confirmed by X-ray
analysis.1H NMR (CDCl3, 400 MHz) δ, ppm: 1.92 (s, 3H), 2.27 (s, 3H),
+
4
3
2
4
145.1, 149.7, 155.4, 166.8, 188.9. HRMS (ESI) C25H22NO3 [M+H]+
2.70 (s, 3H), 3.49 (dt, J=2.3, J=2.3, J=19.7, 1H), 3.87 (ddd, J=
2.3, 3J=8.5, 2J=19.7 Hz, 1H), 4.55 (dd, 3J=2.3, 3J=8.5 Hz, 1H), 6.97–
7.00 (m, 2H), 7.02 (s, 1H), 7.12–7.15 (m, 1H), 7.19–7.22 (m, 2H), 7.43
calcd. for 384.1594, found 384.1699.
(E)-2-(5,7-Dimethyl-3-(p–tolyl)-2,3-dihydro-1H-inden-1-ylidene)-1-
phenylethan-1-one (5w): Yield 20 mg (71%). Yellow crystals. M.p.
(d, J=8.6 Hz, 2H), 7.47 (t, J=2.3 Hz, 1H), 7.91 (d, J=8.6 Hz, 2H). 13C
4
NMR (CDCl3, 100 MHz) δ, ppm: 15.5, 20.1, 22.3, 44.9, 48.7, 114.7,
126.2, 127.3, 128.7, 128.9, 129.5, 132.1, 133.0, 133.1, 136.7, 138.4,
138.6, 140.6, 145.7, 152.4, 165.8, 189.7. HRMS (ESI) C26H24ClO+ [M+
H]+calcd. for 387.1510, found 387.1512.
1
°
157–160 C. The structure was confirmed by X-ray analysis. H NMR
(CDCl3, 400 MHz) δ, ppm: 2.31 (s, 3H), 2.34 (s, 3H), 2.71 (s, 3H), 3.42
4
3
2
4
3
(ddd, J=2.2, J=4.2, J=19.5 Hz, 1H), 4.05 (ddd, J=2.2, J=8.1,
2J=19.5 Hz, 1H), 4.41 (dd, J=4.2, J=8.1 Hz, 1H), 6.84 (s, 1H), 6.97
(s, 1H), 7.04 (d, J=7.9 Hz, 2H), 7.11 (d, J=7.9 Hz, 2H), 7.48–7.57 (m,
4H), 8.01 (d, J=7.0 Hz, 2H). 13C NMR (CDCl3, 100 MHz) δ, ppm: 21.2,
21.6, 22.5, 44.2, 48.9, 115.2, 124.6, 127.8, 128.0, 128.7, 129.4, 131.6,
132.1, 135.8, 136.0, 136.1, 140.3, 141.5, 142.4, 155.0, 164.2, 191.2.
HRMS (ESI) C26H25O+ [M+H]+calcd. for 353.1900, found 353.1903.
3
3
(E)-1-Phenyl-2-(4,5,7-trimethyl-3-(4-methylphenyl)-2,3-dihydro-
1H-inden-1-ylidene)ethan-1-one (5ac):Yield 18 mg (60%). Yellow
crystals. M.p. 173–175 C. The structure was confirmed by X-ray
°
1
analysis. H NMR (CDCl3, 400 MHz) δ, ppm: 1.95 (s, 3H), 2.28 (s, 3H),
2.29 (s, 3H), 2.70 (s, 3H), 3.51 dt (4J=2.7, J=1.8, J=19.6 Hz, 1H),
3
2
3.87 ddd (4J=2.7, 3J=8.5, J=19.6 Hz, 1H), 4.53 (dd, 3J=1.8, 3J=
2
(E)-2-(3-(4-Chlorophenyl)-5,7-dimethyl-2,3-dihydro-1H-inden-1-
ylidene)-1-phenylethan-1-one (5x): Yield 21 mg (75%). Yellow
8.5 Hz, 1H), 6.89 (d, J=8.0 Hz, 2H), 7.02–7.04 (m, 3H), 7.45–7.49 (m,
2H), 7.51–7.55 (m, 2H), 7.97–8.00 (m, 2H). 13C NMR (CDCl3, 100 MHz)
δ, ppm: 15.5, 20.0, 21.1, 22.3, 44.9, 48.2, 115.3, 127.3, 128.1, 128.6,
129.3, 131.9, 132.0, 132.9, 133.0, 135.6, 136.8, 140.2, 140.3, 142.7,
152.4, 165.1, 191.0. HRMS (ESI) C27H27O+ [M+H]+cald. for 367.2056,
found 367.2061.
°
crystals. M.p. 169–172 C. The structure was confirmed by X-ray
1
analysis. H NMR (CDCl3, 400 MHz) δ, ppm: 2.31 (s, 3H), 2.70 (s, 3H),
4
4
2
4
3
3.38 (ddd, J=2.3, J=4.2, J=19.6 Hz, 1H), 4.04 (ddd, J=2.3, J=
2
3
3
8.2, J=19.6 Hz, 1H), 4.40 (dd, J=4.2, J=8.2 Hz, 1H), 6.79 (s, 1H),
6.98 (s, 1H), 7.06 (d, J=8.4 Hz, 2H), 7.24–7.26 (m, 2H), 7.47–7.55 (m,
4H), 7.98–8.00 (m, 2H). 13C NMR (CDCl3, 100 MHz) δ, ppm: 21.6, 22.5,
44.1, 48.6, 115.4, 124.6, 128.1, 128.7, 128.9, 129.3, 131.9, 132.3,
132.4, 135.9, 136.0, 140.2, 141.7, 144.0, 154.2, 163.6, 191.2. HRMS
(MALDI) C25H22ClO+ [M+H]+calcd. for 373.1354, found 373.1356.
(E)-2-(3-(4-Chlorophenyl)-4,5,7-trimethyl-2,3-dihydro-1H-inden-1-
ylidene)-1-phenylethan-1-one (5ad):Yield 23 mg (85%). Yellow oil.
1H NMR (CDCl3, 400 MHz) δ, ppm: 1.92 (s, 3H), 2.27 (s, 3H), 2.70 (s,
3H), 3.49 (dt, J=2.3, J=2.3, J2 =19.6 Hz, 1H), 3.87 (ddd, J=2.3,
4
3
4
3J=8.6, J=19.6 Hz, 1H), 4.55 (dd, J=2.3, J=8.6 Hz, 1H), 6.92 (d,
2
3
3
(E)-1-(5-Bromofuran-2-yl)-2-(5,7-dimethyl-3-phenyl-2,3-dihydro-
1H-inden-1-ylidene)ethan-1-one (5y): Yield 21 mg (80%). Green
J=8.4 Hz, 2H), 7.03 (s, 1H), 7.18 (d, J=8.4 Hz, 2H), 7.45–7.52 (m, 3H),
Eur. J. Org. Chem. 2021, 2634–2649
www.eurjoc.org
2647
© 2021 Wiley-VCH GmbH

Full Papers
doi.org/10.1002/ejoc.202100280
3
3
7.54 (t, 4J=2.3 Hz, 1H), 7.97–7.99 (m, 2H). 13C NMR (CDCl3, 100 MHz)
δ, ppm: 15.6, 20.1, 22.2, 44.6, 47.9, 115.5, 128.1, 128.6, 128.7, 128.8,
131.8, 131.9, 132.2, 133.1, 133.3, 136.8, 140.2, 140.5, 144.3, 151.6,
164.4, 191.1. HRMS (ESI) calcd. for C26H24ClO+ [M+H]+: 387.1510,
found 387.1513.
20.1 Hz, 1H), 4.45 (dd, J=3.3, J=7.9 Hz, 1H), 6.58 (s, 1H), 7.05 (d,
J=8.4 Hz, 2H), 7.20 (s, 1H), 7.26 (d, J=8.4 Hz, 1H), 7.35 (t, 4J=
2.3 Hz, 1H), 7.47–7.55 (m, 3H), 8.01–8.03 (m, 2H.). 13C NMR (CDCl3,
100 MHz) δ, ppm: 44.2, 48.9, 56.3, 56.4, 103.0, 107.7, 108.4, 109.9,
128.1, 128.6, 129.1, 132.2, 132.5, 133.0, 140.1, 143.7, 146.9, 149.8,
153.4, 163.1, 190.6. HRMS (ESI) C25H22ClO3 [M+H]+calcd. for
405.1252, found 405.1255.
+
(E)-2-(5,6-Dimethoxy-3-phenyl-2,3-dihydro-1H-inden-1-ylidene)-1-
phenylethan-1-one (5ae):Yield 16 mg (50%). Brown oil. 1H NMR
(CDCl3, 400 MHz) δ, ppm: 3.40 (ddd, 4J=2.2, 3J=3.1, 2J=20.2 Hz,
(E)-1-Phenyl-2-(3-phenyl-2,3-dihydro-1H-cyclopenta[a]
naphthalen-1-ylidene)ethan-1-one (5ak):Yield 16 mg (50%).
3
2
1H), 3.82 (s, 3H), 4.00 (s, 3H), 4.05 (ddd, 4J=2.2, J=7.9, J=20.2 Hz,
1H), 4.48 (dd, 3J=3.1, 3J=7.9 Hz, 1H), 6.63 (s, 1H), 7.10–7.15 (m, 2H),
Brown oil. H NMR (CDCl3, 400 MHz) δ, ppm: 3.51 (ddd, J=2.3, J=
1
4
3
4
7.19 À 7.24 (m, 2H), 7.27–7.32 (m, 2H), 7.35 (t, J=2.2 Hz, 1H), 7.46–
4.1, 2J=18.8 Hz, 1H), 4.19 (ddd, 4J=2.3, 3J=7.6, 2J=18.8 Hz, 1H),
7.56 (m, 3H), 8.00–8.06 (m, 2H). 13C NMR (CDCl3, 100 MHz) δ, ppm:
44.4, 49.5, 56.2, 56.3, 102.9, 107.8, 109.7, 126.7, 127.7, 128.04, 128.6,
128.8, 132.1, 133.0, 140.2, 145.1, 147.5, 149.6, 153.4, 163.7, 190.6.
4.60 (dd, J=4.1, J=7.6 Hz, 1H), 7.15–7.17 (m, 2H), 7.21–7.25 (m,
2H), 7.27–7.32 (m, 2H), 7.49–7.53 (m, 2H), 7.55–7.60 (m, 2H), 7.69–
7.73 (m, 1H), 7.85 (d, J=8.4 Hz, 1H), 7.95 (d, J=8.3 Hz, 1H), 8.01 (t,
4J=2.3, 1H), 8.04–8.07 (m, 2H), 8.64 (d, J=8.4 Hz, 1H). 13C NMR
(CDCl3, 100 MHz) δ, ppm: 44.7, 50.1, 116.7, 124.0, 124.2, 126.0,
126.9, 127.5, 128.1, 128.3, 128.7, 128.8, 129.6, 129.8, 132.3, 132.9,
133.9, 135.3, 140.1, 144.7, 153.7, 163.3, 191.5. HRMS (ESI) C27H21O+
[M+H]+calcd. for 361.1587, found 361.1590.
3
3
HRMS (ESI) calcd. for C25H23O3 [M+H]+ 371.1642, found 371.1647.
+
(E)-2-(5,6-Dimethoxy-3-phenyl-2,3-dihydro-1H-inden-1-ylidene)-1-
(4-methylphenyl)ethan-1-one (5af):Yield 16 mg (50%). Brown oil.
4
1H NMR (CDCl3, 400 MHz) δ, ppm: 2.42 (s, 3H), 3.40 (ddd, J=2.2,
2
3J=3.1, J=20.1 Hz, 1H), 3.82 (s, 3H), 4.00 (s, 3H), 4.05 (ddd, 4J=2.2,
2
3
3
3J=7.8, J=20.1 Hz, 1H), 4.47 (dd, J=3.1, J=7.8 Hz, 1H), 6.62 (s,
1H), 7.12 (d, J=7.2 Hz, 2H), 7.19–7.23 (m, 1H), 7.21 (s, 1H), 7.27–7.30
(m, 4H), 7.34 (t, 4J=2.2 Hz, 1H), 7.94 (d, J=8.1 Hz, 2H). 13C NMR
(CDCl3, 100 MHz) δ, ppm: 21.7, 44.3, 49.5, 56.2, 56.3, 103.9, 107.9,
109.8, 126.7, 127.8, 128.2, 128.8, 129.3, 133.1, 137.6, 142.7, 145.2,
(E)-1-(4-Chlorophenyl)-2-(3-phenyl-2,3-dihydro-1H-cyclopenta[a]
naphthalen-1-ylidene)ethan-1-one (5al): Yield 9 mg (30%). Yellow
oil. 1H NMR (CDCl3, 400 MHz) δ, ppm: 3.49 (ddd, 4J=2.3, 3J=4.1, 2J=
18.8 Hz, 1H), 4.17 (ddd, J=2.3, J=7.8, J=18.8 Hz, 1H), 4.60 (dd,
3J=4.1, 3J=7.6 Hz, 1H), 7.14–7.16 (m, 2H), 7.21–7.32 (m, 5H), 7.48 (d,
J=8.6 Hz, 2H), 7.56–7.60 (m, 1H), 7.69–7.73 (m, 1H), 7.86 (d, J=
4
3
2
+
147.3, 149.6, 153.3, 163.2, 190.3. HRMS (ESI) calcd. for C26H25O3 [M
+H]+ 385.1798, found 385.1800.
8.4 Hz, 1H), 7.94 (t, J=2.3, 1H), 7.98 (d, J=8.6 Hz, 2H), 8.45 (d, J=
4
8.4 Hz, 1H). 13C NMR (CDCl3, 100 MHz) δ, ppm: 44.7, 50.0, 116.0,
123.8, 124.0,126.0, 126.8,127.9, 128.2, 128.7, 128.9, 129.6, 129.7,
130.9, 133.0, 133.7, 135.0, 138.3, 138.5, 144.4, 153.8, 163.9, 189.9.
HRMS (ESI) C27H20ClO+ [M+H]+calcd. for 395.1197, found 395.1202.
(E)-1-(4-Chlorophenyl)-2-(5,6-dimethoxy-3-phenyl-2,3-dihydro-
1H-inden-1-ylidene)ethan-1-one (5ag):Yield 15 mg (50%). Brown
oil. 1H NMR (CDCl3, 400 MHz) δ, ppm: 3.39 (ddd, 4J=2.4, 3J=3.2, 2J=
20.2 Hz, 1H), 3.82 (s, 3H), 4.00 (s, 3H), 4.06 (ddd, 4J=2.4, 3J=7.8, 2J=
20.2 Hz, 1H), 4.48 (dd, 3J=3.2, 3J=7.8 Hz, 1H), 6.63 (s, 1H), 7.10–7.12
(m, 2H), 7.20 (s, 1H), 7.21–7.24 (m, 1H), 7.27–7.31 (t, 1H), 7.27–7.31
(m, 3H), 7.45 (d, J=8.6 Hz, 2H), 7.97 (d, J=8.6 Hz, 2H). 13C NMR
(CDCl3, 100 MHz) δ, ppm: 44.5, 49.5, 56.3, 56.4, 103.0, 107.9, 109.2,
126.8, 127.8, 128.9, 129.5, 129.3, 132.8, 138.4, 138.5, 145.0, 147.8,
2-(3-(4-Chlorophenyl)-2,3-dihydro-1H-cyclopenta[a]naphthalen-1-
ylidene)-1-phenylethan-1-one (5am): E-/Z-5am in a ratio of10:4.
General yield of 18 mg (60%). Yellow oil. E-5am: 1H NMR (400 MHz,
CDCl3), selected signals δ, ppm: 3.46 (ddd, 4J=2.2, 3J=4.0, 2J=
4
3
2
18.7 Hz, 1H), 4.18 (ddd, J=2.2, J=7.6, J=18.7 Hz, 1H), 4.57 (dd,
149.7, 153.7, 164.5, 189.1. HRMS (ESI) calcd. for C25H22ClO3 [M+H]+
3J=4.0, J=7.6 Hz, 1H), 6.98–7.00 (m, 2H), 7.10–7.11 (m, 2H), 7.12–
+
3
405.1252, found 405.1254.
7.17 (m, 1H), 7.20–7.23 (m, 2H), 7.09 (d, J=8.4 Hz, 2H), 7.22 (d, J=
8.3 Hz, 1H), 7.26 (d, J=8.4 Hz, 2H), 7.48–7.53 (m, 2H), 7.55–7.61 (m,
2H), 7.69–7.73 (m, 1H), 7.86 (d, J=8.4 Hz, 1H), 7.96 (d, J=8.0 Hz,
(E)-1-(4-Bromophenyl)-2-(5,6-dimethoxy-3-phenyl-2,3-dihydro-
1H-inden-1-ylidene)ethan-1-one (5ah): Yield 16 mg (55%). Green
4
1H), 8.01 (t, J=2.2 Hz, 1H), 8.04–8.07 (m, 2H), 8.63 (d, J=8.5 Hz,
1
4
2
oil. H NMR (CDCl3, 400 MHz) δ, ppm: 3.39 (dt, J=2.6, J=20.2 Hz,
1H). 13C NMR (CDCl3, 100 MHz), selected signals δ, ppm: 44.6, 49.4,
1H), 3.82 (s, 3H), 4.00 (s, 3H), 4.06 (ddd, 4J=2.6, J=7.8, J=20.2 Hz,
1H), 4.47 (dd, 3J=2.6, 3J=7.8 Hz, 1H), 6.62 (s, 1H), 7.11 (d, J=7.2 Hz,
2H), 7.20 (s, 1H), 7.26 (d, J=7.3 Hz, 1H) 7.27–7.30 (m, 3H), 7.61 (d,
J=8.4 Hz, 2H), 7.89 (d, J=8.4 Hz, 2H). 13C NMR (CDCl3, 100 MHz) δ,
ppm: 44.5, 49.5, 56.2, 56.3, 103.0, 107.9, 109.1, 126.8, 127.0, 127.7,
128.8, 129.6, 131.8, 132.8, 138.9, 145.0, 147.8, 149.7, 153.7, 149.82,
3
2
162.7, 191.4
Z-5am: 1H NMR (400 MHz, CDCl3), selected signals δ, ppm: 3.50–
4
3
3.55 (m, 1H), 4.07–4.14 (m, 1H), 4.98 (dd, J=2.2, J=8.1 Hz, 1H),
7.01 (d, J=8.4 Hz, 2H), 7.20 (d, J=8.4 Hz, 2H), 7.36–7.40 (m, 1H) .13C
NMR (101 MHz, CDCl3) selected signals δ, ppm: 44.5, 48.2, 163.0,
190.7
164.6, 189.3. HRMS (ESI) calcd. for C25H22BrO3 [M+H]+ 449.0747,
+
found 449.0752.
13C NMR (CDCl3, 100 MHz) δ, ppm (for mixture of (E-/Z-)-isomers):
112.0, 116.8, 118.8, 123.7, 124.1, 125.9, 126.2, 127.1, 127.5, 128.1,
128.3, 128.4, 128.7, 128.8, 128.79, 128.95, 128.99, 129.1, 129.4, 129.5,
129.6, 129.8, 130.3, 132.3, 132.38, 132.4, 132.6, 133.1, 133.9, 135.4,
135.8, 138.8, 139.8, 140.0, 143.2, 144.1, 149.5, 153.0. HRMS (ESI)
C27H20ClO+ [M+H]+calcd. for 395.1197, found 395.1200.
(E)-2-(5,6-Dimethoxy-3-phenyl-2,3-dihydro-1H-inden-1-ylidene)-1-
(4-nitrophenyl)ethan-1-one (5ai): Yield 16 mg (52%). Green oil. H
NMR (CDCl3, 400 MHz) δ, ppm: 3.41 (dt, J=2.6, J=20.4 Hz, 1H),
3.84 (s, 3H), 4.01 (s, 3H), 4.05 (ddd, J=2.6, J=7.7, J=20.4 Hz, 1H),
4.54 (dd, 3J=2.6, 3J=7.7 Hz, 1H), 6.64 (s, 1H), 7.11–7.13 (m, (2H),
7.21 (s, 1H), 7.23–7.25 (m, 1H), 7.28–7.32 (m, 3H), 8.15 (d, J=8.7 Hz,
2H), 8.33 (d, J=8.7 Hz, 2H). 13C NMR (CDCl3, 100 MHz) δ, ppm:
44.77, 49.51, 56.33, 56.38, 103.00, 107.89, 108.93, 123.88, 126.89,
127.74, 128.92, 128.96, 132.53, 144.77, 145.22, 148.55, 149.76,
1
4
2
4
3
2
Spectra of cations in H2SO4
((2Z,4E)-1-(4-Chlorophenyl)-3-(hydroxysulphonyloxy)-5-phenyl-
penta-2,4-dien-1-ylidene)oxonium Ea: 1H NMR (H2SO4, CH2Cl2,
400 MHz, 298 K) δ, ppm: 6.68 (s, 1H), 6.99 (d, J=15.4 Hz, 1H), 7.49 (t,
J=7.3 Hz, 2H), 7.58 (d, J=8.4 Hz, 3H), 7.72 (d, J=7.5 Hz, 2H), 7.97
(d, J=8.4 Hz, 2H), 8.14 (d, J=15.7 Hz, 1H). 13C NMR (H2SO4, CH2Cl2,
101 MHz, 298 K) δ, ppm selected signals: 96.7, 118.1, 126.0, 128.1,
128.7, 129.0, 129.9, 130.1, 132.3, 143.5, 153.9, 182.5, 183.3.
+
149.82, 154.15, 166.47, 188.51. HRMS (ESI) calcd. for C25H22NO5 [M
+H]+ 416.1492, found 416.1499.
(E)-2-(3-(4-Chlorophenyl)-5,6-dimethoxy-2,3-dihydro-1H-inden-1-
ylidene)-1-phenylethan-1-one (5aj): Yield 22 mg (72%). Brown oil.
1H NMR (CDCl3, 400 MHz) δ, ppm: 3.35 (ddd, J=2.3, J=3.3, J=
4
3
2
20.1 Hz, 1H), 3.82 (s, 3H), 4.00 (s, 3H), 4.06 (ddd, 4J=2.3, 3J=7.9, 2J=
Eur. J. Org. Chem. 2021, 2634–2649
www.eurjoc.org
2648
© 2021 Wiley-VCH GmbH

Full Papers
doi.org/10.1002/ejoc.202100280
[4] L. Chen, Z. Liu, S. Zhu, Org. Biomol. Chem. 2018, 16, 8884–8898.
[5] A. L. S. Kumari, A. S. Reddy, K. C. K. Swamy, Org. Biomol. Chem. 2016, 14,
((2Z,4E)-1-(4-Bromophenyl)-3-(hydroxysulphonyloxy)-5-phenyl-
penta-2,4-dien-1-ylidene)oxonium Eb: 1H NMR (H2SO4, CH2Cl2,
400 MHz, 298 K) δ, ppm selected signals: 6.66 (s, 1H), 6.97 (d, J=
15.8 Hz, 1H), 8.13 (d, J=15.8 Hz, 2H). 13C NMR (H2SO4, CH2Cl2,
101 MHz, 298 K) δ, ppm selected signals: 96.6, 118.1, 128.5, 129.0,
129.7, 130.1, 132.2, 132.5, 132.6, 153.9, 182.5, 183.3.
6651–6671.
[6] A. A. Golovanov, D. M. Gusev, S. S. Zlotskii, Russ. J. Org. Chem. 2016, 52,
1205–1206.
[7] D. M. Gusev, A. S. Bunev, A. A. Golovanov, Russ. J. Org. Chem. 2020, 90,
217–223.
[8] A. Mondal, R. Hazra, J. Grover, M. Raghu, S. S. Ramasastry, ACS Catal.
2018, 8, 2748–2753.
[9] S. Saulnier, A. A. Golovanov, A. Yu. Ivanov, I. A. Boyarskaya, A. V. Vasilyev,
J. Org. Chem. 2016, 81, 1967–1980.
[10] S. Saulnier, A. A. Golovanov, A. V. Vasilyev, RSC Adv. 2016, 6, 103546–
103555.
[11] S. Saulnier, S. V. Lozovskiy, A. A. Golovanov, A. Yu. Ivanov, A. V. Vasilyev,
Eur. J. Org. Chem. 2017, 3635–3645.
[12] M. I. Aleksandrova, S. V. Lozovskiy, S. Saulnier, A. A. Golovanov, I. A.
Boyarskaya, A. V. Vasilyev, Org. Biomol. Chem. 2018, 16, 7891–7902.
[13] A. S. Zalivatskaya, A.A. Golovanov, A. V. Vasilyev, Chem. Heterocycl.
Compd. 2020, 56, 953–956.
[14] R. G. Parr, L. V. Szentpaly, S. Liu, J. Am. Chem. Soc. 1999, 121, 1922–1924.
[15] L. V. Alves, M. M. Do Canto-Cavalheiro, L. Cysne-Finkelstein, L. Leon, Biol.
Pharm. Bull. 2003, 26, 453–456.
[16] J. B. Harborne, C.A Williams, Phytochemistry 2000, 55, 481–504.
[17] F. K. Mac Donald, D. J. Burnall, J. Org. Chem. 2009, 74, 6973–6979.
[18] F. Yang, K.-G. Ji, S.-C. Zhao, S. Ali, Y.-Y. Ye, X.-Y. Liu, Y.-M. Liang, Chem.
Eur. J. 2012, 18, 6470–6474.
[19] A. Rinaldi, D. Scarpi, E. G. Occhiato, Eur. J. Org. Chem. 2019, 7401–7419.
[20] Q. He, Z. Yin, H. Chen, Z. Zhang, X. Wang, G. Yue, Prog. Chem. 2016, 28,
801–813.
(6-(4-Chlorophenyl)-2-phenyl-2,3-dihydro-4H-pyran-4-ylidene)
oxonium Fa:1H NMR (H2SO4, CH2Cl2, 400 MHz, 298 K) δ, ppm
selected signals: 3.33 (dd, J=19.0, 4.5 Hz, 1H), 3.58 (dd, J=19.0,
15.1 Hz, 1H), 6.02 (dd, J=15.1, 4.5 Hz, 1H), 6.99 (s, 1H).
(6-(4-Bromophenyl)-2-phenyl-2,3-dihydro-4H-pyran-4-ylidene)
oxonium (Fb):1H NMR (H2SO4, CH2Cl2, 400 MHz, 298 K) δ, ppm
selected signals: 3.33 (dd, J=19.0, 4.5 Hz, 1H), 3.58 (dd, J=19.2,
15.2 Hz, 1H), 6.03 (dd, J=15.1, 4.6 Hz, 1H), 6.99 (s, 1H).
Deposition Numbers 2062816 (for 2a), 2060516 (for 4e), 2060521
(for 5b), 2062817 (for 5c), 2060519 (for 5d), 2060518 (for 5w),
2060515 (for 5x), 2060520 (for 5z), 2060513 (for 5aa), 2060514 (for
5ab), 2060517 (for 5ac) contain the supplementary crystallo-
graphic data for this paper. These data are provided free of charge
by the joint Cambridge Crystallographic Data Centre and Fachinfor-
mationszentrum Karlsruhe Access Structures service www.ccdc.ca-
m.ac.uk/structures.
[21] C. Borie, L. Ackermann, M. Nechab, Chem. Soc. Rev. 2016, 45, 1368–1386.
[22] Y. C. Fan, O. Kwon, Org. Lett. 2015, 17, 2058–2061.
[23] S. Kesavan, J. S. Panek, J. A. Porco, Org. Lett. 2007, 9, 5203–5206.
[24] L. N. Pridgen, K. Huang, S. Shilcrat, A. Tickner-Eldridge, C. DeBrosse, R. C.
Haltiwang, Synlett 1999, 10, 1612–1614.
[25] O. V. Dolomanov, L. J. Bourhis, R. J. Gildea, J. A. K. Howard, H. Pusch-
mann, J. Appl. Crystallogr. 2009, 42, 339–341.
[26] G. M. Sheldrick, Acta Crystallogr. 2008, A64, 112–122.
[27] M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb, J. R.
Cheeseman, G. Scalmani, V. Barone, B. Mennucci, G. A. Petersson, H.
Nakatsuji, M. Caricato, X. Li, H. P. Hratchian, A. F. Izmaylov, J. Bloino, G.
Zheng, J. L. Sonnenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J.
Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, T. Vreven,
Jr., J. A. Montgomery, J. E. Peralta, F. Ogliaro, M. Bearpark, J. J. Heyd, E.
Brothers, K. N. Kudin, V. N. Staroverov, T. Keith, R. Kobayashi, J.
Normand, K. Raghavachari, A. Rendell, J. C. Burant, S. S. Iyengar, J.
Tomasi, M. Cossi, N. Rega, J. M. Millam, M. Klene, J. E. Knox, J. B. Cross, V.
Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev,
A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, R. L. Martin, K.
Morokuma, V. G. Zakrzewski, G. A. Voth, P. Salvador, J. J. Dannenberg, S.
Dapprich, A. D. Daniels, O. Farkas, J. B. Foresman, J. V. Ortiz, J.
Cioslowski, D. J. Fox in Gaussian 09, Revision C.01, Gaussian, Inc.,
Wallingford CT, 2010.
Acknowledgements
This work was supported by Russian Scientific Foundation (grant
no. 21-13-00006). Spectral studies were performed at Center for
Magnetic Resonance, Center for Chemical Analysis and Materials
Research, and Research Center for X-ray Diffraction Studies of
Saint Petersburg State University, Saint Petersburg, Russia.
Conflict of Interest
The authors declare no conflict of interest.
Keywords: Conjugated dienones · Conjugated enynones ·
Dihydropyranones · Indanes · Triflic acid
[28] M. Hoshi, H. Yamazaki, M. Okimoto, Synlett. 2010, 2461–2464.
[1] A. Pankova, Chem. Heterocycl. Compd. 2020, 56, 829–836.
[2] A. A. Golovanov, I. S. Odin, S. S. Zlotskii, Russ. Chem. Rev. 2019, 88, 280–
318.
[3] A. A. Golovanov, D. M. Gusev, I. S. Odin, S. S. Zlotskii, Chem. Heterocycl.
Compd. 2019, 55, 333–348.
Manuscript received: March 5, 2021
Revised manuscript received: April 14, 2021
Eur. J. Org. Chem. 2021, 2634–2649
www.eurjoc.org
2649
© 2021 Wiley-VCH GmbH