Reactions of alkyl 4-hydroxybut-2-ynoates with arenes under superelectrophilic activation with triflic acid or HUSY zeolite: Alternative propargylation or allenylation of arenes, and synthesis of furan-2-ones

Article abstract of DOI:10.1016/j.tet.2019.130517

Reactions of alkyl 4-aryl(or 4,4-diaryl)-4-hydroxybut-2-ynoates [Ar(H or Ar')(OH)C⁴–C³≡C²–CO₂Alk] with arenes under the action of triflic acid TfOH or HUSY zeolite result in the formation of two main compounds, aryl substituted furan-2-ones or products of propargylation of electron rich arenes. Key reactive intermediates in these transformations are the corresponding O,O-diprotonated forms of starting butynoates, Ar(H or Ar')(⁺OH₂)C⁴–C³≡C²– C(=O⁺H)(OAlk), dehydration of which gives rise to mesomeric propargyl-allenyl cations Ar(H or Ar')(OH)⁴C⁺–C³≡C²–C(=O⁺H)(OAlk) ? Ar(H or Ar')(OH)⁴C = C³ = ²C⁺–C(=O⁺H)(OAlk), having two electrophilic centers on the carbons C4 and C2 respectively. Reactions of these species with arenes at C4 lead to products of arene propargylation, alternatively, reactions at C2 result in allenylation of arenes, followed by further transformation into furan-2-ones. Using quantum chemical calculations by the DFT method, it has been shown that the reactivity of such propargyl-allenyl cations is mainly explained by orbital factors. Plausible reaction mechanism is discussed.

Full text of DOI:10.1016/j.tet.2019.130517

Journal Pre-proof
Reactions of alkyl 4-hydroxybut-2-ynoates with arenes under superelectrophilic
activation with triflic acid or HUSY zeolite: Alternative propargylation or allenylation of
arenes, and synthesis of furan-2-ones
Natalia A. Devleshova, Stanislav V. Lozovskiy, Aleksander V. Vasilyev
PII:
S0040-4020(19)30850-6
https://doi.org/10.1016/j.tet.2019.130517
TET 130517
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 5 July 2019
Revised Date: 28 July 2019
Accepted Date: 12 August 2019
Please cite this article as: Devleshova NA, Lozovskiy SV, Vasilyev AV, Reactions of alkyl 4-
hydroxybut-2-ynoates with arenes under superelectrophilic activation with triflic acid or HUSY zeolite:
Alternative propargylation or allenylation of arenes, and synthesis of furan-2-ones, Tetrahedron (2019),
doi: https://doi.org/10.1016/j.tet.2019.130517.
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Reactions of alkyl 4-hydroxybut-2-ynoates with arenes under superelectrophilic
activation with triflic acid or HUSY zeolite: alternative propargylation or
allenylation of arenes, and synthesis of furan-2-ones
Natalia A. Devleshova,1 Stanislav V. Lozovskiy,1 Aleksander V. Vasilyev*1,2
1Department of Organic Chemistry, Institute of Chemistry, Saint Petersburg State University,
Universitetskaya nab., 7/9, Saint Petersburg, 199034, Russia
2Department of Chemistry, Saint Petersburg State Forest Technical University, Institutsky per., 5,
Saint Petersburg, 194021, Russia
*Corresponding author: Aleksander V. Vasilyev; e-mail: aleksvasil@mail.ru; a.vasilyev@spbu.ru
Tel.: 07 812 670 93 52; fax: 07 812 670 93 90
Keywords:
4-hydroxybut-2-ynoates; furan-2-one; propargylation; triflic acid; zeolites
Graphical Abstract
Ar3
Ar1
Ar3
TfOH or
O
HO
Ar1
O
zeolite CBV-720
Ar1
Ar3H
and/or
+
O
2
OAlk
H(or Ar2 )
up to 90%
OAlk
H (or Ar )
O
32 examples
up to 85%
Abstract
Reactions of alkyl 4-aryl(or 4,4-diaryl)-4-hydroxybut-2-ynoates [Ar(H or Ar')(OH)C4–C3≡C2–
CO2Alk] with arenes under the action of triflic acid TfOH or HUSY zeolite result in the formation
of two main compounds, aryl substituted furan-2-ones or products of propargylation of electron rich
arenes. Key reactive intermediates in these transformations are the corresponding O,O-diprotonated
forms of starting butynoates, Ar(H or Ar')(+OH2)C4–C3≡C2– C(=O+H)(OAlk), dehydration of which
gives rise to mesomeric propargyl-allenyl cations Ar(H or Ar')(OH)4C+–C3≡C2–C(=O+H)(OAlk) ↔
Ar(H or Ar')(OH)4C=C3=2C+–C(=O+H)(OAlk), having two electrophilic centers on the carbons C4
and C2 respectively. Reactions of these species with arenes at C4 lead to products of arene
propargylation, alternatively, reactions at C2 result in allenylation of arenes, followed by further
transformation into furan-2-ones. Using quantum chemical calculations by the DFT method, it has
been shown that the reactivity of such propargyl-allenyl cations is mainly explained by orbital
factors. Plausible reaction mechanism is discussed.
1

Introduction
Esters of 4-hydroxybut-2-ynoic acid (alkyl 4-hydroxybut-2-ynoates) are promising building
blocks in organic synthesis. The presence of three important functional groups, such as, acetylene
bond conjugated with ester substituent and hydroxyl group of the propargyl type, in the structure of
these compounds allows involving them in many useful synthetic transformations. They take part in
cycloaddition1,2 and addition of nucleophiles to the acetylene bond,3-5
Meyer-Schuster
rearrangement of propargyl fragment,6-8 Ritter reaction onto the hydroxyl carbon,9 cyclization into
furans,10,11 and metal catalyzed transformation into furan-2-ones.12-14
Based on our works on superelectrophilic activation of acetylene compounds,15 we undertook
a special study on transformations of alkyl 4-hydroxybut-2-ynoates under the action of various
acids. Protonation of these substrates in Brønsted superacids may proceed with a formation of O,O-
diprotonated species A, at the beginning.16,17 Then dehydration of cations A may give rise to
mesomeric propargyl-allenyl cations B↔B', which have two electrophilic centers on the carbons
C2 and C4 and, consequently, may possess a dual reactivity. These species A and B may take part
in interaction with nucleophiles, such as aromatic molecules.
OH
OH
R
O
R
R
R
OH
H+
4 3 2 1
4 3 2 1
4 3 2 1
4 3 2 1
-H2O
R'
OAlk
R'
R'
OAlk
Ar
OAlk
OAlk
OH
OH2
A
B
1
B'
Scheme 1. Protonation of alkyl 4-hydroxybut-2-ynoates in Brønsted acid leading to cations A and
B.
The main goal of this work was a study of reactions of alkyl 4-hydroxybut-2-ynoates 1 with
arenes under the electrophilic activation conditions with Brønsted and Lewis strong acids, or acidic
zeolites. The synthesis of starting butynoates 1a-I, bearing one or two aryl rings with various
substituents, is shown in Scheme 2.
2

ArCHO (or ArCOAr'),
THF, -78oC to r.t.
BuLi, THF, -78oC
OAlk
O
O
HO
Ar
O
Li
H (or Ar')
OAlk
OAlk
1a-i
HO
Ph
O
HO
O
HO
O
HO
Ph
O
HO
Ph
O
OEt
OEt
OEt
OMe
OEt
Ph
1a
1b
1d
1e
1c
Me
MeO
OH
Br
Me
OH
O
OH
OH
O
O
O
Ph
Ph
OEt
OEt
OEt
OEt
1i
1h
1g
1f
Br
Br
Me
MeO
Scheme 2. Synthesis of alkyl 4-hydroxybut-2-ynoates 1a-l used in this study.
Results and discussion
Reactions of alkyl butynoates 1 with arenes in TfOH at room temperature for 1.5 h are shown
in Table 1. The main reaction products are furan-2-ones 2 obtained in yields up to 90%. Benzene,
and its methylated and halogenated derivatives have been successfully involved in this reaction.
However, reactions of butynoates 1 with such donating arenes, as anisole (methoxybenzene) and
veratrole (1,2-dimethoxybenzene), in TfOH led to complex mixtures of reaction products. Apart
from that, monoaryl substituted butynoates 1c,d bearing donating aryl ring gave oligomeric
compounds in reactions with benzene and other arenes. Contrary to that, diaryl substituted
butynoates 1e-i formed the corresponding furanones 2d-p (entries 8-20, Table 1) in good yields,
mainly. Most probably, furanones 2 having one or two donating aryl rings in the position 5 are
unstable in TfOH and undergo oligomerization under superacidic conditions. Indication of that is
the low yields of compounds 2k,l obtained from 5,5-bis-(4-methylphenyl) butynoate 1h (entries 15,
16). Structures of some furanones, 2d-f,m,o,p were confirmed by X-ray analysis (see Table 1).
Apart from furanones 2, other compounds were obtained in this reaction. Thus, monoarylated
butynoates 1a,b gave rise to products of propargylation of arenes 3a-e (entries 1-4, 7) and allene 4a
(entry 4). The formation of compounds 3 and 4 may be explained by a generation and reactivity of
various cationic species derived from starting butynoates 1 under acidic conditions (see Scheme 1,
and discussion on reaction mechanism below).
3

It should be mentioned that other acids were not efficient in this reaction. Thus, interaction of
butynoates 1 with benzene under the action of H2SO4 or AlX3 (X = Cl, Br) resulted in the formation
of complex mixtures of oligomeric compounds.
Table 1. Reactions of alkyl 4-hydroxybut-2-ynoates 1 with arenes in TfOH at room temperature for
1.5 h leading to compounds 2, 3, and 4 (for X-ray structures of 2d-f,m,o,p ellipsoid contour of
probability levels are 50%).
O
Ar3
Ar1
Ar3
O
OAlk
HO
Ar1
O
TfOH
Ar1
H(or Ar2 )
Ar3H
1.5 h, r.t.
Ph
Ph
2
O
OAlk
OAlk
H (or Ar )
O
2
4a
3
1
Entry
1
Starting compounds
Butynoates, 1
Arenes, Ar3H
Reaction products, yields (%)
Me
Me
Me
Me
O
OMe
Ph
O
Ph
O
3a (18%)
2a (8%)
2
3
1a
1a
Ph
4
5
Ph
Ph
O
+
Ph
O
O
OEt
3d (30%)
2b (25%)
O
+
OEt
Ph
Ph
4a (30%)
1b
Me
Me
O
Ph
O
2a (90%)
4

6
1b
1b
7
8
X-ray of 2d
X-ray of 2e
9
1e
1e
10
X-ray of 2f
11
1e
12
13
1g
5

14
15
1g
Me
Me
16
17
1h
Me
Me
O
O
2l (10%)
Me
X-ray of 2m
18
19
1i
1i
X-ray of 2o
20
1i
X-ray of 2p
6

Then, reactions of butynoates 1 with arenes were studied under the action of acidic HUSY
zeolite CBV-720 in glass high pressure tube at 120°C for 1 h (Table 2). Zeolites are considered as
“green” reagents in organic synthesis, they act as effective acidic promoters and catalysts in many
reactions.18 Analogously to TfOH (Table 1), the main products in the zeolite-promoted reactions
were furanones 2 (Table 2, see X-ray structure for 2t). However, there are some differences in
reactions under the action of these two acidic reagents, TfOH and zeolite CBV-720. Monoaryl
substituted butynoates 1c,d having donating aryl groups led to furanones 2t-w with the zeolite
(entries 7-10, Table 2), contrary to the same reactions in TfOH. Therefore, the zeolite is more
tolerant to the structures of such 5-monoaryl substituted furanones 2t-w in comparison with TfOH.
On the other hand, surprisingly, reactions of diarylated butynoates 1e-i with various arenes
furnished oligomeric compounds! For these substrates, we were able to obtain only compound 2x in
the reaction of butynoates 1f with mesitylene (entry 12). Contrary to TfOH (vide supra), reactions
of butynoate 1b with anisole and 2-fluoroanisole led to arene propargylation products 3f,g (entries
4, 5). Also, in some cases, allenes 4b,c were isolated (entries 8, 11). However, in general, the yields
of target furanones 2 and esters 3 (Table 2) are less with the zeolite compared to the reactions in
TfOH (Table 1).
Table 2. Reactions of alkyl 4-hydroxybut-2-ynoates 1 with arenes under the action of acidic HUSY
zeolite CBV-720 at 120°C for 1 h in glass high pressure tube leading to compounds 2, 3, and 4 (for
X-ray structure of 2t ellipsoid contour of probability levels are 50%).
O
Ar3
Ar1
Ar3
O
OAlk
Ar3
HO
Ar1
O
CBV-720
120oC, 1 h
Ar1
H(or Ar2 )
Ar3H
Ar1
2
O
OAlk
OAlk
H (or Ar )
O
2
3
4
1
Entry
1
Starting compounds
Reaction products, yields
(%)
Butynoates, 1
Arenes, Ar3H
2
1b
7

Me
Me
3
4
5
1b
1b
1b
Me
O
Ph
O
2r (10%)
6
7
1b
X-Ray of 2t
8
1c
8

9
1c
10
11
Me
Me
1d
Me
O
EtO
4c (19%)
MeO
12
Additionally, we carried out the propargylation of meta- and para-xylenes by 4-
hydroxybutynoate 1b in hexafluoroisopropanol (HFIP) with catalytic amount of TfOH, that led to
esters 3e,h in high yields (Scheme 3). HFIP is widely used in activation of alcohols in Friedel-
Crafts alkylation of electron rich arenes.19 This reaction proceeds through an intermediate formation
of HFIP-ether I, followed by arene propargylation. It should be mentioned that the reaction did not
proceed without Brønsted acid.
F3C
CF3
(CF3)2CHOH,
H+ (TfOH)
HO
Ph
O
O
O
Ar
O
ArH
0oC, 0.5 h
-H2O
-(CF3)2CHOH
OEt
Ph
OEt
Ph
OEt
I
1b
3
Me
Me
Me
Me
O
O
Ph
OEt
Ph
3e (90%)
OEt
3h (92%)
Scheme 3. Propargylation of meta- and para-xylenes by 4-hydroxybutynoate 1b in the system
hexafluoroisopropanol (HFIP)-TfOH leading to compounds 3e,h.
9

Summarizing all the data obtained on reactions of butynoates 1 with arenes under the
electrophilic activation conditions (Tables 1, 2), one may propose the following plausible reaction
mechanism in Brønsted superacid (Scheme 4). Protonation of oxygen atoms of carbonyl and
hydroxyl groups in TfOH gives rise to species A, which may react with arenes by electrophilic
center at the carbon C4 in SN2 way leading to propargylation products 3. Dehydration of species A
results in the formation of mesomeric propargyl-allenyl cations B↔B', possessing two reactive
centers, carbons C4 and C2, correspondingly. Interaction of arenes with carbon C4 of species B
leads to compound 3. On the other hand, reaction at C2 gives products of allenylation of arenes, O-
protonated forms of allenes C, which form allenes 4 upon hydrolysis of reaction mixtures. Species
C may undergo consequent protonation on the central carbon of the allene system with formation of
allyl cations D. The latter is cyclized into species E, which are finally transformed into furanones 2.
Similar reaction mechanism should be realized with acidic zeolite, which has Brønsted and
Lewis acidic centers. Protonation or coordination of basic centers (oxygen atoms and unsaturated
carbon-carbon bonds) of substrates 1 with the zeolite acidic centers give rise to the corresponding
reactive cationic species.
Based on the proposed mechanism (Scheme 4), some features of this reaction could be
explained. Thus, diarylsubstituted butynoates 1e-i did not give products of propargylation 3 (see
Table 1). It happens, probably, due to spatial reason, since interaction of cations A or B (having aryl
ring R) with arene molecule should lead to the formation of sterically hindered triarylmethyl
fragment, that is unfavorable. Propargylation products are mainly formed with electron rich arenes,
such as xylenes (Table 1) or anisole and 2-fluoroanisole (Table 2), that, probably, shows
participation of species A in this reaction. Allenes 4, laying on a way of formation of compounds 2,
were isolated as intermediate compounds, when unstable furanones 2 were oligomerized under the
acidic reaction conditions.
Some other results of the studied reactions may be rationalized as well. There is a different
reactivity for methyl ester 1a and ethyl ester 1b (compare entries 2 and 6, Table 1). Taking into
account a reversibility of electrophilic process stages (Scheme 4), the formation of furanone 2c
from ethyl ester 1b may be explained by easy transformation of the corresponding species E with
Alk = Et into furanone 2c (entry 6, Table 1). Since, for cationoid transition state, an elimination of
ethyltriflate EtOTf from this species E should proceed easier, than in the case of species E having
Alk = Me, which is formed from methyl ester 1a. For the latter, the corresponding species E may
undergo back conversion into cation B, which finally gives alkyne 3b (entry 2, Table 1).
Apart from that, there are different results for the reactions of butynoate 1a with two aromatic
substrates para-xylene and benzene (entries 1 and 4, Table 1) having various nucleophilicity. In the
latter case, the formation of allene 4a was observed (entry 4, Table 1). Such allenes lie in the
10

reaction pathway (see species C in Scheme 4). Benzene is less π-nucleophilic compared to para-
xylene, consequently, reactions of intermediate cationic species with benzene run slower, and for
the reaction time 1.5 h, one could detect the formation of allene 4a (entry 4, Table 1). More active
para-xylene reacts faster with cationic species finally giving furanone 2a and alkyne 3a (entry 1,
Table 1).
To estimate electronic and electrophilic properties of intermediate species of this reaction we
carried out quantum chemical calculations (DFT method) for cations B1↔B1' and B2↔B2'
derived from butynones 1b and 1e, correspondingly (Table 3). Charge distribution, contribution of
atomic orbital into LUMO and global electrophilicity indices ω20,21 were calculated. Cations B1 and
B2 are rather strong electrophiles, since they have high values of electrophilicity indices ω 30.28 и
29.49 eV, respectively. It is noteworthy that carbons C2 and C4 do not bear a big positive charge.
The positive charge is mainly localized on the carbonyl carbon C1 and in phenyl rings. However,
atoms C2 and C4 give a substantial atomic orbital contributions into LUMO (see also view of
LUMO for B1 in Table 3). Thus, the electrophilic reactivity of atoms C2 and C4 is mainly ruled by
orbital factors, rather than charge ones.
HO
R
Ar
O
H2O
R
Ar
OH
R
OH
R
OH
2H+
-H2O
1
1
2
4
4
1 OAlk
2
3
3
2
Ar 4
3
OAlk
Ar
OAlk
1
OAlk
A
B
B'
R = H, Ar''
Ar'H
-H2O
-2H+
Ar'H
-2H+
Ar'H
-H+
R = H
R = H
O+H
Ar'
H+
R
Ar'
Ar
O
OAlk
Ar
OAlk
OAlk
R
3
H+O
D
C
Ar
H2O
-H+
Ar'
Ar'
1.TfO-, -AlkOTf
2. H2O, -H+
Ar'
R
Ar
Ar
O+H
O
O
O
Ar
OAlk
R
R
O
2
4
Alk
E
Scheme 4. Plausible Brønsted superacid-promoted mechanism of reaction of butynoates 1 with
arenes leading to compounds 2, 3, 4.
Table 3. Selected electronic characteristics (DFT calculations) of cations B1↔B1' and B2↔B2',
derived from butynones 1b and 1e, correspondingly. View of LUMO of species B1↔B1' showing
large contributions of atomic orbitals on the carbon C2 and C4 into LUMO.
11

C4
C2
с
с
Cation
EHOMO
eV
,
ELUMO
eV
,
ω,a
eV
q(C1),b q(C2),b q(C4),b k(C2)LUMO
,
k(C4)LUMO
%
,
e
e
e
%
-15.11 -12.06 30.28
0.82
-0.013 -0.013
16.0
31.2
OH
1
Ph 4
OEt
2
2
2
2
3
B1
OH
Ph4
1 OEt
3
B1'
-13.67 -11.08 29.49
0.83
-0.06
0.08
10.3
19.5
Ph
Ph 4
OH
1
3
OEt
B2
Ph
OH
Ph4
1 OEt
3
B2'
aGlobal electrophilicity index ω = (EHOMO + ELUMO) 2/8(ELUMO - EHOMO).
bNatural charges.
cContribution of atomic orbital into the molecular orbital.
Thus, one of the main results of the present work is a novel metal free synthesis of aryl
substituted furan-2-ones. It should be specially emphasized that preparation of furan-2-ones is an
actual goal of organic chemistry, since these compounds possess a broad range of biological
activities.22 The main methods of synthesis of these furan derivatives are mainly based on metal-
catalyzed transformations of alkynes12-14,23-29 and metal- or acid-promoted reactions of alkenes.30-43
Conclusion
We have developed a novel synthesis of aryl substituted furan-2-ones based on reactions of
alkyl 4-aryl(or 4,4-diaryl)-4-hydroxybut-2-ynoates with arenes under the action of triflic acid TfOH
or acidic zeolite CBV-720. It has been found that in order to obtain the corresponding furan-2-ones
from alkyl 4,4-diaryl-substituted 4-hydroxybut-2-ynoates better to use TfOH. On the other hand, for
the synthesis of furan-2-ones from alkyl 4-aryl-substituted 4-hydroxybut-2-ynoates one should take
12

the zeolite. Apart from furan-2-ones, these reactions give alternative products of propargylation of
donating arenes.
Experimental part
The NMR spectra of solutions of compounds in CDCl3 were recorded on Bruker AVANCE
1
19
13
III 400 (at 400, 376 and 100 MHz for H, F and C NMR spectra respectively) spectrometer at
1
25°C. The residual proton-solvent peak CDCl3 (δ 7.26 ppm) for H NMR spectra and the carbon
signal of CDCl3 (δ 77.0 ppm) for 13C NMR spectra were used as references. 19F NMR spectra were
indirectly referred to the signal of CFCl3 (δ 0.0 ppm). HRMS (ESI-TOF) was carried out at
instruments Bruker maXis-ESI-QTOF Mass Spectrometer. IR spectra of compounds were taken
with Bruker spectrometer. The preparative reactions were monitored 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. HUSY zeolite CBV-720 was purchased from the company Zeolist Int.
X-ray diffraction study. A suitable crystal was selected and studied on the diffractometer.
The crystal was kept at 100(2) K during data collection. Using Olex244 the structure was solved
with the ShelXS45 structure solution program using Direct Methods and refined with the ShelXL
refinement package using Least Squares minimization. CCDC 1919234 – (2d), CCDC 1919237 –
(2e), CCDC 1919238 – (2f), CCDC 1919240 – (2m), CCDC 1919241 – (2o), CCDC 1919242 –
(2p), CCDC 1919243 – (2t) contain the supplementary crystallographic data, which can be
obtained free of charge at www.ccdc.cam.ac.uk/conts/retrieving.htmL or from the Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; Fax: (internat.) + 44-
1223-336-033; E-mail: deposit@ccdc.cam.ac.uk.
DFT calculations. All computations were carried out at the DFT level of theory using
functional B3LYP by using GAUSSIAN 2009 program packages.46 The geometries optimization
were performed using the B3LYP basis set (standard 6-311 basis set added with polarization (d, p)
and diffuse functions). Optimizations were performed on all degrees of freedom and gas-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. Atomic charges and contributions
in LUMO for species B1, B2 were obtained using NBO analysis.
Starting alkyl 4-hydroxybutynoates 1a-i were obtained according the literature procedure.42
General procedure for the synthesis of starting butynoates 1a-i. Solution of BuLi in
hexanes (6.4 mmol, 4 mL, 1.6 M concentration) was added dropwise for 5 min to a solution of ethyl
(or methyl) propynoate (3.3 mmol) in THF (10 mL) at –78°С with vigorous magnetic stirring.
13

After 10 min the corresponding aromatic aldehyde or benzophenon (3.2 mmol) was added at –
78°С. Reaction mixture was slowly heated to room temperature for 2 h. Then mixture was treated
with saturated aqueous solution of NH4Cl (4 mL), extracted with EtOAc (3 × 10 mL). The
combined extracts were dried with Na2SO4. After evaporation of the solvent under the reduced
pressure, reaction product was isolated by preparative TLC using petroleum ether – ethyl acetate
mixture (4 : 1 vol.) as an eluent.
Methyl 4-hydroxy-4-phenylbut-2-ynoate (1a).47 Yield of 75%. Yellow oil.1H NMR (400 MHz,
13
CDCl3) δ, ppm: 3.50 t (1H), 3.76 s (3H), 5.52 s (1H), 7.32 – 7.40 m (3H), 7.47 – 7.50 m (2H). C
NMR (100 MHz, CDCl3) δ, ppm: 52.9, 64.1, 87.0, 126.7, 128.8, 128.8, 128.9, 138.6, 153.9. IR
(KBr), cm-1: 1717 (C=O), 2239 (C≡C), 3429 (O-H). HRМS (ESI) m/z: [М+Na]+ calcd. for
C11H10NaO3 213.0522, found 213.0522.
Ethyl 4-hydroxy-4-phenylbut-2-ynoate (1b).47 Yield of 75%. Yellow oil. 1Н NMR (400 MHz,
CDCl3) δ ppm: 1.30 t (3H, J 7 Hz), 2.88 s (1H, OH), 4.24 q (2H, J 7 Hz), 5.56 s (1H), 7.35 – 7.41 m
(3H), 7.50 – 7.52 m (2H).
1
Ethyl 4-hydroxy-(4-methylphenyl)but-2-ynoate (1с).47 Yield of 95%. Yellow oil. Н NMR
(400 MHz, CDCl3) δ ppm: 1.31 t (3H, J 7.1 Hz), 2.36 s (3H), 4.24 q (2H, J 7.1 Hz), 5.53 s (1H), 7.1
d (2H, J 8.0 Hz), 7.4 d (2H, J 8.0 Hz). 13C NMR (100 MHz, CDCl3) δ, ppm: 13.9, 21.1, 62.2, 64.1,
77.8, 86.2, 126.6, 129.5, 135.7, 138.8, 153.3. IR (KBr), cm-1: 1712 (C=O), 2235 (C≡C), 3397 (O-
H). HRМS (ESI) m/z: [М+Na]+ calcd. for C13H14NaO3 241.0835, found 241.0836.
Ethyl 4-hydroxy-4-(4-methoxyphenyl)but-2-ynoate (1d).47 Yield of 48%. Yellow oil. 1Н NMR
(400 MHz, CDCl3) δppm: 1.31 t (3H, J 7.14 Hz), 4.18 s (1H), 4.81 s (3H), 4.24 q (2H, J 7.13 Hz),
5.51 s (1H), 6.91 d (2H, J 8.8 Hz), 7.44 d (2H, J 8.8 Hz).
1
Ethyl 4-hydroxy-4,4-diphenylbut-2-ynoate (1e). Yield of 60%. Yellow oil. Н NMR (400
MHz, CDCl3) δ, ppm: 1.32 t (3H, J 7.1 Hz), 2.88 s (1H, ОН), 4.25 q (2H, J 7.1 Hz), 7.28 – 7.37 m
(6H), 7.57 – 7.59 m (4H). 13C NMR (100 MHz, CDCl3) δ, ppm: 14.0, 62.3, 74.4, 78.6, 88.6, 126.1,
128.2, 128.5, 143.2, 153.5. IR (KBr), cm-1: 1698 (C=O), 2238 (C≡C), 3441 (O-H). HRМS (ESI)
m/z: [М+Na]+ calcd. for C18H16NaO3 303.0992, found 303.0992.
Ethyl 4-hydroxy-4-(4-methoxyphenyl)-4-phenylbut-2-ynoate (1f). Yield of 70%. Yellow oil.1H
NMR (400 MHz, CDCl3) δ, ppm: 1.33 t (3Н, J 7.1 Hz), 3.26 s (1H, ОН), 3.80 s (3H), 4.27 q (2H, J
7.1 Hz), 6.86-6.90 m (2H), 7.32-7.39 m (3H), 7.48-7.50 m (2H), 7.58-7.60 m (2H).IR (KBr), cm-1:
1711 (C=O), 2233 (C≡C), 3434 (O-H). HRМS (ESI) m/z: [М+Na]+ calcd. for C19H18NaO4
333.1097, found 333.1092.
Ethyl 4-(4-bromophenyl)-4-hydroxy-4-phenylbut-2-ynoate (1g). Yield of 30%. Orange oil. 1H
NMR (400 MHz, CDCl3) δ, ppm: 1.31 t (3H, J 7.1 Hz), 3.31 s (1H, ОН), 4.25 q (2H, J 7.1 Hz),
7.31 – 7.35 m (3H), 7.42 – 7.48 m (4H), 7.53 – 7.55 m (2H). 13CNMR (100 MHz, CDCl3) δ, ppm:
14

14.0, 62.4, 74.0, 78.9, 87.8, 122.4, 126.0, 127.9, 128.5, 128.6, 131.6, 142.3, 142.7, 153.3. IR (KBr),
cm-1: 1712 (C=O), 2235 (C≡C), 3434 (O-H). HRМS (ESI) m/z: [М+Na]+ calcd. for C18H15BrNaO3
381.0097, found 381.0097.
Ethyl 4-hydroxy-4,4-di(4-methylphenyl)but-2-ynoate (1h). Yield of 40%. Orange oil. 1Н NMR
(400 MHz, CDCl3) δ, ppm: 0.93 t (3H, J 7.1 Hz), 2.34 s (6H), 3.11 m (1H, ОН), 4.25 q (2H, J 7.1
Hz), 7.15 d (4H, J 8.2 Hz), 7.45 d (4H, J 8.2 Hz).13C NMR (100 MHz, CDCl3) δ, ppm:14.1, 21.1,
62.2, 74.1, 78.4, 90.1, 126.0, 129.1, 138.0, 140.6, 153.6. IR (KBr), cm-1: 1713 (C=O), 2234 (C≡C),
3430 (O-H). HRМS (ESI) m/z: [М+Na]+calcd. forC20H20NaO3331.1305, found 331.1305.
Ethyl 4,4-di(4-bromophenyl)-4-hydroxybut-2-ynoate (1i). Yield of 45%. Orange oil.1H NMR
(400 MHz, CDCl3) δ, ppm:1.31 t (3H, J 7 Hz), 3.54 s (1H, ОН), 4.24 q (2H, J 7 Hz), 7.38 – 7.41 m
13
(4H), 7.45 – 7.47 m (4H). CNMR (100 MHz, CDCl3) δ, ppm: 14.0, 62.6, 73.5, 79.0, 87.2, 122.7,
127.7, 131.7, 141.9, 153.2. IR (KBr), cm-1: 1713 (C=O), 2236 (C≡C). HRМS (ESI) m/z: [М+Na]+
calcd. for C18H14Br2NaO3 458.9202, found 458.9202.
General procedure for reaction of butynoates 1 with arenes in TfOH. Synthesis of
compounds 2, 3, 4 (Table 1). TfOH (0.1 mL) was added to a solution of butynoate 1 (0.16 mmol)
in arene (1mL) at room temperature with vigorous magnetic stirring. Reaction mixture was stirred
at room temperature for 1.5 h. Then the reaction mixture was poured into water (10 mL), extracted
with CH2Cl2 (3 × 10 mL). Combined extracts were washed with saturated aqueous solution of
NaHCO3 (2 ×10 mL), water (10 mL), dried with Na2SO4. Organic solvents were distilled off under
the reduced pressure, reaction products were isolated by preparative TLC using petroleum ether –
ethyl acetate mixture (9 : 1 vol.) as an eluent. Yields of compounds 2, 3 and 4 are presented in
Table 1.
General procedure for reaction of butynoates 1 with arenes under the action of acidic
zeolite HUSY (CBV-720). Synthesis of compounds 2, 3, 4 (Table 2).
A mixture of butynoate 1 (0.15 mmol), 5 mL of arene and 250 mg of HUSY zeolite CBV-720
(commercially available material), which was pre-calcinated at 400-450°C for 2 h, was heated in
the high pressure glass tube at 120°C for 1 h with vigorous magnetic stirring. Then, the reaction
mixture was cooled down to room temperature. The zeolite was filtered off on a glass filter and
washed several times with СН2Cl2 (3 × 10 mL). Organic solutions were combined and were
distilled off under the reduced pressure. Reaction products were isolated by preparative TLC using
petroleum ether – ethyl acetate mixture (9 : 1 vol.) as an eluent. Yields of compounds 2, 3 and 4 are
presented in Table 2.
Procedure for reaction of butynoate 1b with xylenes in hexafluoroisopropanol (HFIP)
with a catalytic amount of TfOH. Synthesis of compounds 3e,h (Scheme 3). Butynoate 1b (0.15
mmol) was added to mixture of arene (0.05 mL) with HFIP (0.1 mL) and TfOH (catalytic amount)
15

at 0°С. The mixture was magnetically stirred 0.5 h at this temperature. Then the reaction mixture
was poured into water (10 mL), extracted with CHCl3 (3 × 10 mL). The combined extracts were
washed with saturated aqueous solution of NaHCO3 (2 ×10 mL), water (10 mL), dried with
Na2SO4. Evaporation of organic solvent under the reduced pressure gave pure reaction products 3e
(yield of 90%) or 3h (yield of 92%).
3-(2,5-Dimethylphenyl)-5-phenylfuran-2(5H)-one (2a). Yellow oil. 1H NMR(400 MHz,
CDCl3)δ, ppm: 2.33 s (3H), 2.34 s (3H), 6.07 d (1H, J 1.7 Hz), 7.12 d (1H, J 7.6 Hz), 7.16 d (1H, J
7.9 Hz), 7.23 s (1H), 7.36dd (2H, J 1.7 Hz J 7.6 Hz), 7.40 d (1H, J 1.7 Hz), 7.41 – 7.46 m
(3H).13CNMR(100 MHz, CDCl3) δ, ppm: 20.0, 20.9, 29.7, 82.1, 126.6, 129.0, 129.1, 129.3, 130.0,
130.1, 130.6, 133.0, 133.5, 135.0, 135.5, 150.6. IR (KBr), cm-1: 1766 (C=O). HRМS (ESI) m/z:
[М+Na]+calcd. for C18H16NaO2 287.1043, found 287.1043.
1
3,5-Diphenylfuran-2(5H)-one (2b). Yellow oil. H NMR (400 MHz, CDCl3) δ, ppm: 6.06 d
13
(1Н, J 1.8 Hz), 7.33-7.35 m (2H), 7.40-7.44 m (6H), 7.63 d (1H, J 1.8 Hz), 7.89-7.91 m (2H). C
NMR (100 MHz, CDCl3) δ, ppm: 29.7, 81.6, 126.6, 127.2, 128.7, 129.1, 129.3, 129.3, 129.5, 134.8,
147.3, 171.7. HRМS (ESI) m/z: [М+Na]+ calcd. for C16H12NaO2 259.0730, found 259.0733.
1
3-(3,4-Dimethylphenyl)-5-phenylfuran-2(5H)-one (2с). Yellow oil. H NMR (400 MHz,
CDCl3) δ, ppm: 2.29 s (3Н), 2.30 s (3Н), 5.75 d (1Н, J 1.6 Hz), 6.81 – 7.22 m (9Н), 7.59 d (1Н,J
13
1.6 Hz). C NMR (100 MHz, CDCl3) δ, ppm: 21.0, 21.9, 83.2, 127.7, 128.3, 128.8, 129.4, 130.2,
130.4, 131.0, 131.2, 131.6, 134.1, 134.5, 136.5, 150.5, 170. HRМS (ESI) m/z: [М+Na]+calcd. for
C18H16NaO2 287.1043, found 287.1045.
1
3,5,5-Triphenylfuran-2(5H)-one (2d). Colorless solid, mp147 °C. H NMR (400 MHz,
CDCl3) δ, ppm: 7.34 – 7.43 m (13H), 7.90 – 7.92 m (2H), 8.03 s (1H). 13C NMR (100 MHz, CDCl3)
δ, ppm: 89.1, 126.7, 127.3, 128.6, 128.7, 128.8, 129.3, 129.6, 129.8, 139.8, 150.3, 170.8. IR (KBr),
cm-1: 1755 (C=O). HRМS (ESI) m/z: [М+Na]+ calcd. for C22H16NaO2 335.1043, found 335.1043.
3-(2,5-Dimethylphenyl)-5,5-diphenylfuran-2(5H)-one (2e). Colorless solid, mp140°C.1H
NMR (400 MHz, CDCl3) δ, ppm: 2.31 s (3H), 2.33 s (3H), 7.11dd (1Н, J 1.4 Hz, J 7.9 Hz), 7.15 d
(1Н, J 7.9 Hz), 7.23 s (1H), 7.34 – 7.43 m (10H), 7.82 s (1H). 13C NMR (100 MHz, CDCl3) δ, ppm:
20.0, 20.8, 89.8, 126.7, 128.6, 128.8, 128.9, 130.0, 130.2, 130.6, 131.7, 133.5, 135.5, 139.9, 153.9,
171.3. IR (KBr), cm-1: 1762 (C=O). HRМS (ESI) m/z: [М+Na]+calcd. for C24H20NaO2 363.1356,
found 363.1356.
1
3-(1,3,5-Trimethylphenyl)-5,5-diphenylfuran-2(5H)-one (2f). Colorless solid, mp130°C. H
NMR (400 MHz, CDCl3) δ, ppm: 2.14 s (6H), 2.29 s (3H), 6.91 s (2H), 7.38 – 7.41 m (10H), 7.73 s
(1H). 13C NMR (100 MHz, CDCl3) δ, ppm: 20.3, 21.1, 90.4, 126.0, 126.7, 128.5, 128.6, 128.8,
131.7, 136.7, 138.6, 140.0, 155.2, 171.4. IR (KBr), cm-1: 1762 (C=O). HRМS (ESI) m/z: [М+Na]+
calcd. for C25H22NaO2 377.1512, found 377.1512.
16

3-(3-Fluoro-4-methylphenyl)-5,5-diphenylfuran-2(5H)-one (2g). Colorless solid, mp108°C.
1H NMR (400 MHz, CDCl3) δ, ppm: 2.31 d (3H, J 2.0 Hz), 7.04 t (1H, J 8.9 Hz), 7.34 – 7.39 m
13
(10H), 7.71 – 7.77 m (2H), 7.97 s (1H). C NMR (100 MHz, CDCl3) δ, ppm: 14.5 d (J 3.5 Hz),
89.1, 115.4 d (J 3.7 Hz), 125.1 d (J 3.7 Hz), 125.4 d (J 4.9 Hz), 126.6 d (J 4.9 Hz), 126.7, 128.6,
128.8, 128.9, 130.6 d (J 5.4 Hz), 139.8, 149.7, 162.1 d (J 284.9 Hz), 170.8. 19F NMR (376 MHz,
CDCl3)δ, ppm: -115.08. IR (KBr), cm-1: 1757 (C=O). HRМS (ESI) m/z: [М+Na]+calcd.
forC23H17FNaO2 367.1105, found 367.1105.
1
5-(4-Bromophenyl)-3,5-diphenylfuran-2(5H)-one (2h). Yellow oil. Н NMR (400 MHz,
CDCl3) δ, ppm: 7.25 – 7.27 m (2H), 7.35 – 7.38 m (5H), 7.41 – 7.43 m (2H), 7.49 – 7.52 m (3H),
13
7.89 – 7.91 m (2H), 7.98 c (1H). C NMR (100 MHz, CDCl3) δ, ppm: 88.6, 122.9, 126.6, 127.3,
128.4, 128.8, 128.8, 128.9, 129.7, 130.1, 130.1, 130.2, 131.9, 138.9, 139.3, 149.6. IR (KBr), cm-1:
1762 (C=O). HRMS (ESI) m/z: [M+Na]+ calcd. For C22H15BrNaO2 413.0148, found 413.0148.
5-(4-Bromophenyl)-3-(2,5-dimethylphenyl)-5-phenylfuran-2(5H)-one (2i). Yellow oil. 1Н
NMR (400 MHz, CDCl3) δ, ppm: 2.29 c (3H), 2.33 c (3H), 7.10 – 7.16 m (2H), 7.20 c (1H), 7.27 –
13
7.30 m (2H), 7.40 – 7.41 m (5H), 7.51 – 7.54 m (2H). C NMR (100 MHz, CDCl3) δ, ppm: 20.0,
20.8, 89.2, 122.9, 126.6, 128.3, 128.7, 128.8, 128.9, 130.1, 130.1, 130.6, 132.0, 132.0, 133.5, 135.5,
139.1, 139.4, 135.2, 171.0. IR (KBr), cm-1: 1765 (C=O). HRMS (ESI) m/z: [M+H]+ calcd. for
C24H19BrNaO2 419.0641, found 419.0641.
1
5-(4-Bromophenyl)-3-(1,3,5-trimethylphenyl)-5-phenylfuran-2(5H)-one (2j). Orange oil. Н
NMR (400 MHz, CDCl3) δ, ppm: 2.11 c (3H), 2.13 c (3H), 2.29 c (3H), 6.91 c (2H), 7.27 – 7.29 m
(2H), 7.35 – 7.42 m (5H), 7.51 – 7.55 m (2H), 7.68 c (1H). 13C NMR (100 MHz, CDCl3) δ, ppm:
20.3, 21.1, 89.8, 122.9, 125.8, 126.6, 128.3, 128.5, 128.9, 128.9, 132.0, 136.6, 136.7, 138.7, 139.2,
139.5, 154.6, 171.1. IR (KBr), cm-1: 1764 (C=O). HRMS (ESI) m/z: [M+H]+ calcd. for
C25H21BrNaO 2433.0798, found 433.0798.
1
5-Bis(4-methylphenyl)-3-(2,5-dimethylphenyl)-5-phenylfuran-2(5H)-one (2k). Orange oil. Н
NMR (400 MHz, CDCl3) δ, ppm: 2.29 c (3H), 2.32 c (3H), 3.36 c (3H), 7.09 d (1H, J 7.7 Hz), 7.14
d (1H, J 7.8 Hz), 7.18 d (5H, J 8.3 Hz), 7.27 d (4H + CDCl3, J 8.3 Hz). 13C NMR (100 MHz,
CDCl3) δ, ppm: 20.0, 20.8, 21.1, 89.7, 126.6, 129.1, 129.4, 129.8, 130.2, 130.5, 131.4, 133.5, 135.4,
137.1, 38.4, 154.2, 171.5. IR (KBr), cm-1: 1761 (C=O). HRMS (ESI) m/z: [M+H]+ calcd. for
C26H24NaO 2369.1849, found369.1849.
5-Bis(4-methylphenyl)-3-(1,3,5-trimethylphenyl)-5-phenylfuran-2(5H)-one (2l). Orange oil.
1Н NMR (400 MHz, CDCl3) δ, ppm: 2.14 s (3H), 2.28 c (2H), 2.37 c (3H), 2.45 c (6H), 6.90 c (1H),
7.19 d (2H, J 8.0 Hz), 7.28 d (4H, J 8.0 Hz), 7.71 d (4H, J 8.0 Hz). 13C NMR (100 MHz, CDCl3) δ,
ppm: 20.3, 21.1, 21.6, 126.6, 128.4, 128.9, 129.4, 130.2, 135.3, 136.8, 137.2, 138.4, 142.9, 155.5,
17

196.3. IR (KBr), cm-1: 1763 (C=O), 2922 (C=C). HRMS (ESI) m/z: [M+Na]+ calcd. for C27H26NaO
2405.1825, found 405.1825.
5-Bis(4-bromophenyl)-3-phenylfuran-2(5H)-one (2m). Orange solid, mp130°C. 1Н NMR (400
MHz, CDCl3) δ, ppm: 7.24 d (4H, J 8.6 Hz), 7.42 – 7.45 m (3H), 7.51 d (4H, J = 8.60 Hz), 7.88 –
7.90 m (2H), 7.93 c (1H). 13C NMR (100 MHz, CDCl3) δ, ppm: 88.1, 123.2, 127.3, 128.3, 128.8,
129.9, 130.4, 132.1, 138.4, 148.9, 170.2. IR (KBr), cm-1: 1762 (C=O). HRMS (ESI) m/z: [M+Na]+
calcd. for C22H14Br2NaO2 490.9253, found 490.9253.
5-Bis(4-bromophenyl)-3-(2,5-dimethylphenyl)furan-2(5H)-one (2n). Orange oil. 1Н NMR(400
MHz, CDCl3)δ, ppm: 2.28 c (3H), 2.33 c (3H), 7.11 – 7.16 m (2H), 7.19 c (1H), 7.25 d (4H, J 8.6
Hz), 7.53 d (4H, J 8.6 Hz), 7.72 c (1H). 13C NMR (100 MHz, CDCl3) δ, ppm: 20.0, 20.8, 88.6,
123.2, 128.3, 128.4, 130.1, 130.2, 130.7, 132.1, 132.3, 133.4, 135.6, 138.5, 152.6, 170.7. IR (KBr),
cm-1: 1763 (C=O). HRMS (ESI) m/z: [M+Na]+ calcd. for C24H18Br2NaO2 518.9566, found
518.9566.
5-Bis(4-bromophenyl)-3-(1,3,5-trimethylphenyl)furan-2(5H)-one
(2o).
Yellow
solid,
mp180°C. 1Н NMR (400 MHz, CDCl3) δ, ppm: 2.10 c (6H), 2.29 c (3H), 6.91 c (2H), 7.23 – 7.26 m
(4H), 7.52 – 7.55 m (4H), 7.64 c (1H). 13C NMR (100 MHz, CDCl3) δ, ppm: 20.3, 21.1, 89.2,
123.2, 125.5, 128.2, 128.6, 132.1, 132.4, 136.6, 138.6, 138.8, 153.9, 170.8. IR (KBr), cm-1: 1764
(C=O). HRMS (ESI) m/z: [M+Na]+ calcd. for C25H20Br2NaO2 532.9772, found 532.9772.
5-Bis(4-bromophenyl)-3-(3-fluoro-4-methylphenyl)furan-2(5H)-one(2p).
Yellow
solid,
mp100°C. 1Н NMR (400 MHz, CDCl3) δ, ppm: 2.31 d (3H, J 1.5 Hz), 7.05 t (1H, J 8.9 Hz), 7.22 –
7.24 m (4H), 7.50 – 7.52 m (4H), 7.69 – 7.75 m (2H), 7.86 c (1H). 13C NMR(100 MHz, CDCl3) δ,
ppm: 14.6 (J 3.3 Hz), 88.2, 115.5 (J 22.9 Hz), 123.2, 124.6 (J 3.8 Hz), 125.5 (J 17.8 Hz), 167.7 (J
19
8.4 Hz), 128.3, 129.6, 130.6 (J 5.6 Hz), 132.1, 138.3, 148.4, 162.3 (J 249.6 Hz), 170.4. F NMR
(CDCl3, 376 MHz) δ, ppm: -114.32. IR (KBr), cm-1: 1760 (C=O). HRMS (ESI) m/z: [M+Na]+
calcd. for C23H15Br2FNaO2 522.9315, found 522.9315.
1
3-(3,4-Dichlorophenyl)-5-phenylfuran-2(5H)-one (2q). Colorless oil. Н NMR (400 MHz,
CDCl3) δ, ppm: 6.05 d (1H, J 1.6 Hz), 7.31 – 7.33 m (2H), 7.40 – 7.44 m (3H), 7.50 – 7.52 m
(1H), 7.68 d (1H, J 2.0 Hz), 7.77 – 7.79 m (1H), 8.04 d (1H, J 2.0 Hz). 13C NMR (100 MHz,
CDCl3) δ, ppm: 81.6, 126.4, 126.5, 129.0, 129.0, 129.1, 129.2, 129.5, 130.7, 133.1, 133.8, 134.2,
148.4, 171.0. IR (KBr), cm-1: 1757 (С=О) HRMS (ESI) m/z: [M+Na]+ calcd. for C16H10Cl2NaO2
326.9950, found 326.9950.
1
3-(1,3,5-Trimethylphenyl)-5-phenylfuran-2(5H)-one(2r). Brown oil. Н NMR (400 MHz,
CDCl3) δ, ppm: 2.21 c (3H), 2.22 c (3H), 2.30 c (3H), 6.12 d (1H, J 1.5 Hz), 6.93 c (1H), 6.94 c
(1H), 7.31 d (1H, J 1.5 Hz), 7.36 – 7.38 m (2H), 7.41 – 7.44 m (3H). 13C NMR (100 MHz, CDCl3)
δ, ppm: 20.3, 20.5, 21.1, 82.7, 126.2, 126.6, 128.5, 128.5, 129.2, 129.3, 132.9, 135.0, 136.6, 136.6,
18

138.6, 151.9, 172.2. IR (KBr), cm-1: 1762 (С=О). HRMS (ESI) m/z: [M+Na]+calcd. forC19H18NaO2
310.1199, found 310.1199.
1
3-(3-Fluoro-4-methylphenyl)-5-phenylfuran-2(5H)-one (2s). Yellow oil. Н NMR (400 MHz,
CDCl3) δ, ppm: 2.32 d (3H, J 2.3 Hz), 6.02 c (1H), 7.05 t (1H), 7.32 – 7.34 m (2H), 7.38 – 7.43 m
(3H), 7.56 d (1H, J 7.6 Hz), 7.69 – 7.72 m (1H), 7.75 – 7.77 m (1H). 13C NMR (100 MHz, CDCl3)
δ, ppm: 14.6, 81.5, 115.4 d (J 22.7 Hz), 125.4 d (J 17.7 Hz), 126.5 d (J 8.5 Hz), 126.6, 129.1, 129.3,
19
129.4, 130.2, 130.5 d (J 5.5 Hz), 134.8, 146.7 d (J 1.4 Hz), 162.1 d (J 248.8 Hz), 171.7. F NMR
(376 MHz, CDCl3) δ, ppm: - 115.16. IR (KBr), cm-1: 1759 (C=O). HRMS (ESI) m/z:
[M+Na]+calcd. for C17H13FNaO2 291.0792, found 291.0793.
5-(4-Methylphenyl)-3-phenylfuran-2(5H)-one (2t). Colorless oil. 1Н NMR (400 MHz, CDCl3)
δ, ppm: 2.37 c (3H), 5.99 d (1H, J 1.8 Hz), 7.22 c (4H), 7.40-7.45 m (3H), 7.60 d (1H, J 1.8 Hz),
7.89-7.91 m (2H). 13C NMR (100 MHz, CDCl3) δ, ppm: 21.2, 81.5, 126.7, 127.2, 128.7, 129.4,
129.5, 129.7, 131.0, 131.8, 139.3, 147.4, 171.8. IR (KBr), cm-1: 1758 (С=О). HRMS (ESI)
m/z: [M+Na]+calcd. forC17H14NaO2 273.0886, found 273.0886.
1
5-(4-Methylphenyl)-3-(1,3,5-Trimethylphenyl)furan-2(5H)-one (2u). Yellow oil. Н NMR
(400 MHz, CDCl3) δ, ppm: 2.21 c (6H), 2.30 c (3H), 2.38 c (3H), 6.08 d (1Н, J 1.7 Hz,), 6.93 c
13
(2H), 7.25 c (4H), 7.29 d (1H, J 1.7 Hz). C NMR (100 MHz, CDCl3) δ, ppm: 20.3, 20.5, 21.1,
21.2, 82.7, 113.0, 126.3, 126.6, 128.5, 129.8, 131.9, 131.9, 132.8, 136.6, 138.5, 139.3, 152.1, 172.3.
IR (KBr), cm-1: 1759 (C=O). HRMS (ESI) m/z: [M+Na]+ calcd. for C20H20NaO2 315.1356, found
315.1356.
3-(3-Fluoro-4-methylphenyl)-5-(4-methylphenyl)furan-2(5H)-one (2v). Colorless oil.1Н NMR
(400 MHz, CDCl3) δ, ppm: 2.31 d (3H, J 1.8 Hz), 2.38 c (3H), 5.98 d (1H, J 1.9 Hz), 7.05 t (1H),
7.21 c (4H), 7.54 d (1H, J 1.9 Hz), 7.68 – 7.72 m (1H), 7.75 – 7.77 m (1H). 13C NMR (100 MHz,
CDCl3) δ, ppm: 14.6 d (J 3.6 Hz), 21.2, 81.5, 115.4 d (J 22.9 Hz), 125.4 d (J 17.7 Hz), 126.5 d (J
8.2 Hz), 126.6, 129.7, 130.1, 130.5 d (J 5.5 Hz), 131.7, 139.4, 146.8 d (J 1.3 Hz), 147.4, 162.0 d (J
284.4 Hz), 171.8. 19F NMR (376 MHz, CDCl3) δ, ppm: -115.26.IR (KBr), cm-1: 1754 (C=O).
HRMS (ESI) m/z: [M+Na]+ calcd. for C18H15FNaO2 305.0948, found 305.0948.
1
5-(4-Methoxyphenyl)-3-phenylfuran-2(5H)-one (2w). Brown oil. НNMR (400 MHz, CDCl3)
δ, ppm: 3.82 c (3H), 5.98 d (1H, J 1.7 Hz), 6.91-6.94 m (2H), 7.24 c (2H), 7.41 – 7.46 m (3H), 7.60
d (1H, J 1.93 Hz), 7.90-7.92 m (2H). 13C NMR (100 MHz, CDCl3) δ, ppm: 29.7, 55.4, 81.4, 113.7,
114.5, 126.6, 127.2, 128.3, 128.7, 129.4, 129.5, 130.4, 131.2, 147.2, 160.4, 171.7. IR (KBr), cm-1:
1758 (С=О). HRMS (ESI) m/z: [M+Na]+ calcd. for C17H14NaO3 289.0835, found 289.0835.
1
5-(4-Methoxyphenyl)-3-(1,3,5-trimethylphenyl)-5-phenylfuran-2(5H)-one (2x). Yellow oil. Н
NMR (400 MHz, CDCl3) δ, ppm: 2.11 c (3H), 2.17 c (3H), 2.29 c (3H), 3.82 c (3H), 6.90 – 6.92 m
(4H), 7.30 d (2H, J 8.8 Hz,), 7.35 – 7.40 m (5H), 7.68 c (1H). 13C NMR (100 MHz, CDCl3) δ, ppm:
19

20.3, 20.4, 21.1, 55.3, 90.3, 114.1, 126.1, 126.6, 128.2, 128.5, 128.8, 131.4, 132.0, 136.7, 136.8,
138.5, 140.2, 155.4, 159.7, 171.5. IR (KBr), cm-1: 1761 (С=О). HRMS (ESI) m/z: [M+Na]+ calcd.
for C26H24NaO3407.1618, found 407.1618.
Methyl 4-(2,5-dimethylphenyl)-4-phenylbut-2-ynoate (3a). Yellow oil .1НNMR (400 MHz,
CDCl3) δ, ppm: 2.23 c (3H), 2.32 c (3H), 3.78 c (3H), 5.27 c (1H), 7.00 – 7.06 m (2H), 7.19 c
(1H), 7.23 – 7.34 m (5H). 13C NMR (100 MHz, CDCl3) δ, ppm: 19.1, 21.1, 40.0, 52.6, 76.25, 88.7,
127.2, 127.9, 128.4, 128.7, 129.4, 130.8, 132.7, 136.0, 136.8, 138.6, 154.2. IR (KBr), cm-1: 1716
(C=O), 2234 (C≡C). HRMS (ESI) m/z: [M+Na]+calcd. For C19H18NaO2 301.1199, found 301.1199.
1
Methyl 4-(3,4-dimethylphenyl)-4-phenylbut-2-ynoate (3b). Yellow oil. НNMR (400 MHz,
CDCl3) δ, ppm: 2.23 c (3H), 2.24 c (3H), 3.78 c (3H), 5.07 c (1H), 7.08 – 7.10 m (3H), 7.30 – 7-34
m (2H), 7.35 – 3.37 m (3H). 13C NMR (100 MHz, CDCl3) δ, ppm: 19.4, 19.8, 42.6, 52.6, 76.4, 88.9,
125.2, 127.3, 127.8, 128.8, 129.1, 130.1, 135.8, 136.8, 137.1, 139.7, 154.2. IR (KBr), cm-1: 1716
(C=O), 2236 (C≡C). HRMS (ESI) m/z: [M+Na]+calcd. For C19H18NaO2 301.1199, found 301.1199.
1
Methyl 4-(3,5-dimethylphenyl)-4-phenylbut-2-ynoate (3с). Yellow oil. НNMR (400 MHz,
CDCl3) δ, ppm: 2.24 c (3H), 2.31 c (3H), 3.77 c (3H), 5.26 c (1H), 6.99 c (1H), 7.03 d (1H, J 8.0
13
Hz), 7.28 – 7.33 m (6H). C NMR (100 MHz, CDCl3) δ, ppm: 19.5, 20.9, 39.8, 52.6, 76.2, 88.7,
127.2, 127.2, 127.9, 128.7, 128.7, 131.7, 134.2, 135.7, 137.4, 138.7, 154.2. IR (KBr), cm-1: 1719
(C=O), 2924 (C≡C). HRMS (ESI) m/z: [M+Na]+ calcd. for C19H18NaO2 301.1200, found 301.1199.
Ethyl 4,4-diphenylbut-2-ynoate(3d). Yellow oil.1НNMR(400 MHz, CDCl3) δ, ppm: 1.36 t
(3Н, J 7.1 Hz), 4.29 q (2H, J 7.1 Hz), 5.17 s (1Н), 7.26-7.41 m (10Н). 13CNMR (100 MHz, CDCl3)
δ, ppm: 14.0, 42.9, 62.0, 81.6, 88.0, 126.6, 127.2, 127.4, 127.9, 139.4, 147.3, 153.8. HRMS(ESI)
m/z: [M+Na]+calcd. for C18H16NaO2 287.1035, found 287.1035.
Ethyl 4-(3,5-dimethylphenyl)-4-phenylbut-2-ynoate (3e). Yellow oil .1Н NMR (400 MHz,
CDCl3) δ, ppm: 1.33 t (3H, J 7.2 Hz), 2.27 c (3H), 2.33 c (3H), 4.25 q (2H, J 7.2 Hz), 5.29 c (1H),
13
6.97-7.10 m (3Н), 7.23-7.38 m (6H). C NMR (100 MHz, CDCl3) δ, ppm: 14.1, 19.5, 20.9, 39.7,
61.9б 76.5, 88.3, 127.2, 127.2, 127.9, 128.7, 128.8, 131.7, 134.3, 135.7, 137.3, 138.7, 153.8.IR
(KBr), cm-1: 1710 (C=O), 2231 (C≡C). HRMS (ESI) m/z: [M+Na]+ calcd. for C20H20NaO2
315.1352, found 315.1352.
1
Ethyl 4-(4-methoxyphenyl)-4-phenylbut-2-ynoate (3f). Orange oil. НNMR (400 MHz,
CDCl3) δ, ppm: 1.33 t (3H), 3.80 s (3H), 4.25 q (2H), 5.10 s (1H), 6.87 d (2H, J 8.7 Hz), 7.27 d
13
(2H, J 8.7 Hz), 7.27 s (1H), 7.31 – 7.36 m (4H). C NMR (100 MHz, CDCl3) δ, ppm: 14.1, 42.2,
55.3, 62.0, 76.7, 88.3, 114.2, 127.3, 127.8, 128.8, 129.0, 131.6, 139.8, 156.8, 158.9. IR (KBr), cm-1:
1708 (C=O), 2232 (C≡C). HRMS (ESI) m/z: [M+Na]+ calcd. for C19H18NaO3 317.1148, found
317.1148.
20

1
Ethyl 4-(3-fluoro-4-methoxyphenyl)-4-phenylbut-2-ynoate (3g). Orange oil. НNMR (400
MHz, CDCl3) δ, ppm: 1.33 t (3H, J 7.1 Hz), 3.88 s (3H), 4.26 q (2H, J 7.1 Hz), 5.07 s (1H), 6.92 t
(1H, J 8.6 Hz), 7.04 – 7.09 m (2H), 7.27 s (1H), 7.34 – 7.35 m (4H). 13CNMR (100 MHz, CDCl3) δ,
ppm: 14.0, 42.1, 56.3, 62.1, 77.2, 87.4, 113.6 d (J 1.8 Hz), 115.8 d (J 19.7 Hz), 123.5 d (J 3.7 Hz),
127.6, 127.8, 128.9, 132.4 d (J 5.7 Hz), 139.1, 147.0 d (J 10.6 Hz), 152.4 d (J 253.9 Hz), 153.6.
19FNMR(CDCl3, 376 MHz)δ, ppm: - 133.98.IR (KBr), cm-1: 1082 (С-F), 1708 (C=O), 2235 (C≡C).
HRMS(ESI) m/z: [M+Na]+ calcd. for C19H17FNaO3 335.1054, found 335.1054.
1
Ethyl 4-(2,5-dimethylphenyl)-4-phenylbut-2-ynoate (3h). Yellow oil. НNMR (400 MHz,
CDCl3) δ, ppm: 1.27 t (3H, J 7.1 Hz), 2.19 c (3H), 2.28 c (3H), 4.19 q (2H, J 7.2 Hz), 5.23 c (1H),
7.17 – 7.33 m (8H). 13C NMR (100 MHz, CDCl3) δ, ppm: 14.2, 40.0, 61.9, 82.1, 88.2, 127.2,
127.5, 127.9, 128.4, 128.7, 129.1, 129.5, 129.9, 130.2, 130.8, 138.6, 150.7, 153.8. HRMS (ESI)
m/z: [M+Na]+ calcd. for C20H20NaO2 315.1355, found 315.1356.
Ethyl 2,4-diphenylbut-2-diynoate (4a).1Н NMR (400 MHz, CDCl3) δ, ppm: 1.34 t (3H,J 7.1
Hz), 4.27 q (2H, J 7.1 Hz), 6.06 c (1H), 7.26-7.41 m (10H). 13C NMR (100 MHz, CDCl3) δ, ppm:
14.0, 42.9, 62.0, 81.6, 88.0, 128.7, 128.8, 129.1, 129.3, 139.4, 147.3, 153.8, 212.0. HRMS (ESI)
m/z: [M+Na]+ calcd. for C18H16NaO2 287.1035, found 287.1035.
1
Ethyl 2-(1,3,5-trimethylphenyl) -4-(4-methylphenyl)but-2-diynoate (4b). Yellow oil. НNMR
(400 MHz, CDCl3) δ, ppm: 1.28 t (3H, J 7.1 Hz ), 2.27 s (3H), 2.28 s (6H), 2.34 s (3H), 4.26 q (2H,
13
J 7.1 Hz), 6.56 s (1H), 6.89 s (2H), 7.14 d (2H, J 8.0 Hz), 7.22 d (2H, J 8.0 Hz). C NMR (100
MHz, CDCl3) δ, ppm: 14.3, 20.6, 21.0, 21.3, 61.3, 96.9, 103.7, 127.6, 128.4, 128.9, 129.4, 129.5,
136.7, 137.5, 137.7, 165.8, 212.7. IR (KBr), cm-1: 1735 (C=O), 2956 (C=C). HRMS (ESI) m/z:
[M+Na]+ calcd. for C22H24NaO2 343.1669, found 343.1669.
Ethyl 2-(1,3,5-trimethylphenyl)-4-(4-methoxyphenyl)but-2-diynoate (4c). Yellow oil. 1НNMR
(400 MHz, CDCl3) δ, ppm: 1.28 t (3H, J 7.1 Hz), 2.27 s (3H), 2.28 s (6H), 3.80 s (3H), 4.26 q (2H,
13
J 7.1 Hz), 6.55 s (1H), 6.87 d (2H, J 8.7 Hz), 6.89 s (2H), 7.26 d (2H, J 8.7 Hz). C NMR (100
MHz, CDCl3) δ, ppm: 14.3, 20.6, 21.0, 55.3, 61.3, 96.6, 103.7, 113.0, 114.3, 124.1, 128.4, 128.8,
129.5, 136.6, 137.5, 159.4, 165.8, 212.5. IR (KBr), cm-1: 1714 (C=O), 2922 (C=С). HRMS (ESI)
m/z: [M+Na]+ calcd. for C22H24NaO3 359.1618, found 359.1618.
Acknowledgment
This work was supported by Russian Scientific Foundation (grant no. 18-13-00008). 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.
21

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23

Highlights
• Metal-free synthesis of furan-2-ones
• Superelctrophilic activation of 4-hydroxybut-2-ynoates with Bronsted superacids and acidic
zeolites
• Reaction mechanism of electrophilic transformations of 4-hydroxybut-2-ynoates with arenes
into furan-2-ones