Ligand-free palladium-catalyzed tandem pathways for the synthesis of 4,4-diarylbutanones and 4,4-diaryl-3-butenones under microwave conditions

Article abstract of DOI:10.1002/aoc.4870

Two efficient Pd-catalyzed tandem pathways for the synthesis of 4,4-diaryl-2-butanones and 4,4-diaryl-3-buten-2-ones were elaborated. The first step in both procedures was the Heck coupling of methyl vinyl ketone (MVK) and various aryl iodides leading to 4-aryl-3-buten-2-one with the yield of up to 92% in 1?hr. The second step performed with the same catalyst and a new portion of aryl iodide in the presence K₂CO₃ as a base produced 4,4-diaryl-3-buten-2-ones in high yield. Reaction selectivity changed completely to saturated 4,4-diaryl-2-butanones, reductive Heck products, when a tertiary amine was used instead of K₂CO₃. Due to the application of microwave irradiation (MW), the desired products were obtained in high yield in a short time (4?hr), using 0.5?mol% of the Pd (OAc)₂ catalyst without additional ligands.

Full text of DOI:10.1002/aoc.4870

Received: 16 December 2018
DOI: 10.1002/aoc.4870
Revised: 27 January 2019
Accepted: 28 January 2019
F U L L P A P E R
Ligand‐free palladium‐catalyzed tandem pathways for the
synthesis of 4,4‐diarylbutanones and 4,4‐diaryl‐3‐butenones
under microwave conditions
Anna Wirwis | Anna M. Trzeciak
Faculty of Chemistry, University of
Two efficient Pd‐catalyzed tandem pathways for the synthesis of 4,4‐diaryl‐2‐
butanones and 4,4‐diaryl‐3‐buten‐2‐ones were elaborated. The first step in both
procedures was the Heck coupling of methyl vinyl ketone (MVK) and various
aryl iodides leading to 4‐aryl‐3‐buten‐2‐one with the yield of up to 92% in 1 hr.
The second step performed with the same catalyst and a new portion of aryl
iodide in the presence K2CO3 as a base produced 4,4‐diaryl‐3‐buten‐2‐ones in
high yield. Reaction selectivity changed completely to saturated 4,4‐diaryl‐2‐
butanones, reductive Heck products, when a tertiary amine was used instead
of K2CO3. Due to the application of microwave irradiation (MW), the desired
products were obtained in high yield in a short time (4 hr), using 0.5 mol%
of the Pd (OAc)2 catalyst without additional ligands.
Wrocław, 14 F. Joliot‐Curie, 50‐383
Wrocław, Poland
Correspondence
Anna M. Trzeciak, University of Wrocław,
Faculty of Chemistry, 14 F. Joliot‐Curie,
50‐383 Wrocław, Poland.
Email: anna.trzeciak@chem.uni.wroc.pl
Funding information
National Science Centre (NCN, Poland),
Grant/Award Number: 2014/15/B/ST5/
02101
KEYWORDS
diaryl‐ketones, Heck coupling, MW irradiation, palladium, reductive Heck coupling
1 | INTRODUCTION
reductive Heck reaction (conjugate addition).[24–33] Both
of those strongly related reactions,[22,31,32] proceeding
Mono‐ and diarylated ketones are a class of compounds
with a wide potential of application. Especially important
among them are chalcones[1–7] and β‐aryl‐α,β‐unsaturated
enones; for example, 4‐aryl‐3‐buten‐2‐ones.[8–10] The high
biological activity of many chalcone derivatives makes
them important materials for the fabrication of drugs
against cancer or atherosclerosis.[1–4] They can also be
used in the production of fluorescent probes[5,6] or optical
materials.[7] Moreover, β‐substituted carbonyl compounds
are the backbone of active biomolecules, such as
enokipodine B (fungal biomarker) or paroxetine (antide-
pressant).[11] Synthetic methods used for the preparation
of β‐arylketones are usually based on a coupling between
methyl vinyl ketone (MVK) and various aryl reagents in
the presence of palladium catalysts.[12–19] Further
functionalization, leading to appropriate β‐diarylketones,
can be performed using synthetic tools that form a new
carbon–carbon bond: the Heck reaction[20–23] or the
with the formation of the same alkyl‐palladium‐halide
transition complex, have been the subject of intensive
research for many years.[24,25,27] The currently available
data confirm that the Heck arylation is a much recognized
method, especially due to the possibility of using various
easily available aryl halides.[22]
In contrast, in palladium‐catalyzed reductive Heck
arylation, mostly different organometallic compounds
have been applied as the source of the aryl group.
Grignard
compounds,[34,35]
organoboron
com-
pounds,[36,37] organozincs,[38] organosilicons[39–41] and
other organometallic reagents have been used in the pres-
ence of copper, rhodium, or palladium catalysts. However,
due to the high cost of these reagents, their low stability in
reaction conditions or in the presence of water, replacing
them with aryl halides is a favorable alternative. For the
first time efficient palladium‐catalyzed reductive Heck
arylation with aryl halides was described in 1983 by Cacchi
Appl Organometal Chem. 2019;e4870.
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https://doi.org/10.1002/aoc.4870

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WIRWIS AND TRZECIAK
and co‐workers.[24] The method they developed involved
the use of iodobenzene derivatives and corresponding
enones or enals with the application of reducing agents
such as NEt3, Bu4NI, or HCOOH.[24] They observed that
the nature of the base had a significant effect on the selec-
tivity of the reaction and the type of product obtained. In
the presence of inorganic bases like NaHCO3 or
CH3COONa, vinyl substitution occurred, while in the case
of a tertiary amine, the reaction course changed towards a
reductive Heck product.[25] A similar result was obtained
by Minnaard et al., who reported an efficient Pd‐NHC‐
catalyzed Heck reaction and the conjugate addition of aryl
iodides and β‐substituted‐α,β‐unsaturated enones in the
presence of CsOPiv and NBu3, respectively.[27] It is note-
worthy that, in recent years, the progress of studies on con-
jugate addition has aided the search for different arylating
agents, such as sodium arylsulfinates,[42] arylsulfonyl
hydrazides[43] or benzenesulfonyl chlorides.[44] Neverthe-
less, the direct palladium‐catalyzed reductive arylation of
ketones with aryl halides has been scarcely reported.
The broad application of aryl ketones[8–10] and their
derivatives strongly motivates the development of selec-
tive and efficient synthetic methods leading to these com-
pounds. In most cases reported in the literature, the
arylation of aryl ketone to get β,β‐diarylketone has been
studied, while the synthesis of the first aryl ketone has
not been discussed in this context. Our approach, pre-
sented in this paper, was based on a tandem process
involving two arylation steps with the same catalyst,
without the isolation of the first aryl ketone (Figure 1).
The second modification consisted in the application of
MW irradiation instead of conventional heating.[12,45–47]
It was expected that this would shorten the reaction time
and save energy.
2 | EXPERIMENTAL
1. Arylation of 3‐buten‐2‐one followed by
reductive Heck reaction
a
The reaction was carried out in a special microwave tube
under microwave irradiation. The reagents, aryl iodide
(1.34 mmol), NaHCO3 (1.25 mmol; 0.1050 g), Pd (OAc)2
(0.5 mol%, 0.001504 g), 3‐buten‐2‐one (2.01 mmol;
0.163 cm3), and DMF/H2O = 3/2 (2.5 cm3) were intro-
duced to the microwave tube. Next, the tube with the
reaction mixture was stirred under microwave conditions
at 120 °C for the 1 hr. After that time, more aryl iodide
(1.34 mmol) and tripropylamine (1.25 mmol; 0.236 cm3)
were added and microwave heating continued for 3 hr
at the same temperature. When the reaction time was fin-
ished, the organic products were separated by extraction
with diethyl ether (10 cm3 and three times with 5 cm3).
The products were GC–MS‐analyzed (Hewlett Packard
8454 Å) with mesitylene (75 μl) as the internal standard.
2. Arylation of 3‐buten‐2‐one followed by a Heck
reaction
The reaction was carried out in a special microwave tube
under MW irradiation. The reagents, aryl iodide
(1.34 mmol), NaHCO3 (1.25 mmol; 0.1050 g), Pd (OAc)2
(0.5 mol%, 0.001504 g), 3‐buten‐2‐one (2.01 mmol;
0.163 cm3), and DMF/H2O = 3/2 (2.5 cm3) were intro-
duced to the microwave tube. Next, the tube with the
reaction mixture was stirred under microwave conditions
at 120 °C for 1 hr. After that time, more aryl iodide
(1.34 mmol) and K2CO3 (1.25 mmol; 0.1728 g) were
added and MW heating continued for 2 hr at the same
FIGURE 1 Two tandem syntheses of diarylketones

WIRWIS AND TRZECIAK
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temperature. After that time, the organic products were
separated by extraction with diethyl ether (10 cm3 and
three times with 5 cm3). The products were GC–MS‐
analyzed (Hewlett Packard 8454 Å) with mesitylene
(75 μl) as the internal standard.
3 | RESULTS AND DISCUSSION
3.1 | Heck arylation of methyl vinyl
ketone (MVK)
The Heck arylation of 3‐buten‐2‐one (MVK) by PhI was
studied as the first reaction to obtain a substrate for fur-
ther functionalization. Under the applied conditions,
using MW, the formation of the desired product, 4‐phe-
nyl‐3‐buten‐2‐one 3R, was quite efficient already in
1 hr; however, some amount of another product,
diarylated ketone, 4RR, was also observed (Figure 2).
Thus, the optimization of the reaction parameters aimed
at an increase of 3R yield.
FIGURE 3 Optimization of the palladium catalyst for the Heck
arylation of 3‐buten‐2‐one.Reaction conditions: 1.34 mmol 3‐
buten‐2‐one (MVK); 1.34 mmol PhI; 0.5 mol% Pd (OAc)2;
1.25 mmol NaHCO3; 1 hr; 160 °C; MW; 2.5 cm3 DMF, 0.5–3 bar
First, different palladium catalysts were tested
(Figure 3), and Pd (OAc)2 was found superior to the
others, giving the highest yield of 3R, 81%. Interestingly,
palladium complexes without phosphorus ligands were
more active than complexes bearing phosphito ligands.
The oxidation state of palladium did not influence the
reaction course, and similar results were obtained with
Pd (II) (Pd (acac)2, PdCl2(CH3CN)2) and with Pd(0)
(Pd2(dba)3) (Figure 3).
The screening of different bases enabled the selection
of NaHCO3 as the best one for the synthesis of 3R, while
other bases, such as carbonates, promoted the formation
of diarylated ketone. For example, the application of
K2CO3 or Cs2CO3 made it possible to produce symmetric
4,4‐diphenyl‐3‐buten‐2‐one with yields of up to 30%
(Figure 4).
FIGURE 4 Optimization of the base for the Heck arylation of 3‐
buten‐2‐one.Reaction conditions: 1.34 mmol 3‐buten‐2‐one (MVK);
1.34 mmol PhI; 0.5 mol% Pd (OAc)2; 1.25 mmol base; 1 hr; 160 [°C];
MW; 2.5 cm3 DMF, 0.5–3 bar
3.2 | Tandem synthesis of 6RR'
Thus, optimized conditions for the efficient synthesis
of 3R were defined as 0.5 mol% of Pd (OAc)2, NaHCO3
as a base, 160 °C, and 1 h under MW. These conditions
were applied to obtain the substrate 3R for a tandem
reaction, aimed at the synthesis of diarylated butanone
containing two different aryl groups.
A tandem experiment focused on the synthesis of 6RR'
was performed, in the first step applying optimized condi-
tions for the synthesis of 3R, which was obtained with a
yield of 81% (Figure 5). Next, without the isolation of
3R, another aryl iodide, p‐iodoanisole, was introduced
FIGURE 2 Heck arylation of methyl
vinyl ketone with phenyl iodides

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WIRWIS AND TRZECIAK
FIGURE 5 Tandem Heck reaction
leading to 4‐(4‐methoxyphenyl)‐4‐phenyl‐
2‐butanone
TABLE 2 Testing of different additives in the reductive Heck
reaction
to the same vessel together with amine. Amine was cho-
sen for this reaction because, according to the literature
data, the presence of alkyl amine should facilitate reduc-
tive coupling and the formation of saturated
diarylketone.[24,25,27]
Entry
Reducing agent [mmol]
T[oC]
4RR' [%]
1a
2
‐
160
75
4
6
iPrOH (6.54)
iPrOH (32.70)
H2O (27.78)
CH3COOH (1.25)
The
results
obtained
with
tripropylamine,
tributylamine, and diisopropyl‐ethylamine are presented
in Table 1.
3
75
4
4
75
10
12
The yield of the desired product, 6RR' (R = H;
R' = OMe), was similar for the three tested amines,
amounting to 69–72%. The second product, unsaturated
ketone, was formed with a yield of up to 27% as a mixture
of E and Z isomers with the E/Z ratio of ca. 2. For com-
parison, reactions were performed at a lower tempera-
ture, 75 °C, using NEt3 and NPr3; however, only ca. 6%
of 6RR' was formed in these conditions. Attempts to use
other additives with potentially reducing activity instead
of alkyl amines failed. In the presence of water, iPrOH,
or CH3COOH, only 4–12% of 4RR' was obtained, while
6RR' was not found (Table 2).
5
120
Reaction conditions: Step I: 1.34 mmol 3‐buten‐2‐one (MVK); 1.34 mmol PhI;
0.5 mol% Pd (OAc)2; 160 °C; 1 hr; MW; 0.5–3 bar
Step II: 1.34 mmol p‐iodoanisole; 120 °C; 1 hr; MW
aResults obtainedafter the first step.
was based on our earlier studies on the arylation of allylic
alcohols, where water improved the yield of the prod-
uct.[19] It was found that water increased the conversion
of MVK to ca. 100%; however, selectivity to 3R decreased
due to the formation of a diarylated ketone, 4RR
(R = H), with a yield of 13–16% (SI, Table 2). The
increase of the amount of water promoted a decrease in
the yield of 3R to 76% at the DMF/H2O ratio of 3/2.
Concerning the effect of the base, similar results were
obtained for three bases, NaHCO3, Na2CO3, and KHCO3
at DMF/H2O = 4/1 (SI, Table 2). Thus, the kind of base
did not influence the reaction course.
The ratio of the substrates, [PhI]/[MVK], was the next
parameter changed during the optimization of the reac-
tion conditions. Figure 6 presents the dependence of the
yield of 3R on the substrate ratio and the water amount.
With an increase in the amount of MVK, PhI conver-
sion increased, and only the product 3R (R = H) was
formed with the yield of 90% at [PhI]/[MVK] = 1/1.5 in
DMF. In a DMF/H2O mixture, the conversion of PhI
reached 100%, and the yield of 3R was 95%.
3.3 | Coupling reactions in the presence of
water
The introduction of water to the reaction medium aimed
at the improvement of both steps of the catalytic reaction,
starting from the first coupling leading to 3R. That idea
TABLE 1 Heck synthesis of β,β‐diaryl‐2‐butanones under MW
conditions in the presence of different amines
Amine
[mmol]
Conversion
3R [%]
6RR'
[%]
4RR' (E/Z)
[%]
Entry
1
2
3
NBu3
89
95
88
69
68
72
14/6
20/7
11/5
(iPr)2NEt
NPr3
Considering the ratio DMF/H2O = 3/2 as the best one,
different temperatures were tested (Figure 7).
It was found that the yield of 3R was only slightly
lower at 130 °C and 120 °C than at 160 °C, while only
74% of 3R was obtained at 110 °C (Figure 7). In all cases,
Reaction conditions: Step I: 1.34 mmol 3‐buten‐2‐one (MVK); 1.34 mmol PhI;
0.5 mol% Pd (OAc)2; 160 °C; 1 hr; MW; 0.5–3 bar
Step II: 1.34 mmol p‐iodoanisole; 1.25 mmol amine, 120 °C; 1 hr; MW

WIRWIS AND TRZECIAK
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FIGURE 6 Influence of the PhI: MVK ratio and water on the
yield of the productsReaction conditions: 1.34 mmol PhI; 0.5 mol%
Pd (OAc)2; 1.25 mmol NaHCO3; 1 hr; 160 [°C]; MW; 2.5 cm3 DMF
or DMF/H2O, 0.5–3 bar
FIGURE 8 Heck arylation between methyl vinyl ketone and p‐
substituted phenyl iodidesReaction conditions: 2.01 mmol 3‐buten‐
2‐one (MVK); 1.34 mmol ArI; 0.5 mol% Pd (OAc)2; 1.25 mmol
NaHCO3; 1 hr; 120 °C; 2.5 cm3 DMF/H2O (3/2), MW; 0.5–3 bar
added to the reaction mixture obtained after the first
Heck coupling (Figure 9).
During the reaction, the undesirable arylation of the
remaining MVK by the aryl iodide 2R' was also observed.
To eliminate this side process, unreacted MVK was
removed under vacuum before the introduction of the
second aryl iodide. After this improvement, only two
products were detected in the reaction mixture, namely
6RR' and 4RR'. Moreover, 6RR' was the main one with
the yield of 57–83% (Table 3).
Reactions were carried out in a mixture DMF/H2O
(3/2), and a total conversion of the aryl iodide 2R was
achieved in all cases. It was found that the amount of
NPr3 influenced the product composition in reactions with
p‐iodoanisole, and a higher yield of 6RR' was obtained in
most cases using 1.58 mmol of amine than using
1.25 mmol. However, for p‐iodotoluene, the amount of
amine influenced the yield of 6RR' much less.
FIGURE 7 Optimization of the Heck reaction temperature at
PhI/MVK = 1/1.5Reaction conditions: 2.01 mmol 3‐buten‐2‐one
(MVK); 1.34 mmol PhI; 0.5 mol% Pd (OAc)2; 1.25 mmol NaHCO3;
1 hr; MW; 2.5 cm3 DMF/H2O (3/2), 0.5–3 bar
In reactions with p‐iodotoluene and iodobenzene, the
final composition of the products was practically the
same regardless of the order in which the reagents were
added. Interestingly, in reactions with p‐iodoanisole and
iodobenzene, a much lower yield of 6RR' (63%) was
obtained when p‐iodoanisole was used in the first step
of the tandem reaction than in the second one (77%)
(Table 3, runs 3 and 10). The E/Z ratio of 4RR'
isomers obtained in these reactions also differed from
16/15 to 13/8.
a small amount of biphenyl, up to 6%, was also formed.
The reaction at 120 °C was also performed using conven-
tional heating, and after 6 hr the yield of 3R was 94%. The
same result was obtained under MW already after 1 hr
confirming the high efficiency of MW irradiation.
Conditions optimized for the synthesis of 3R in the
DMF/H2O medium under MW irradiation were also
applied for other aryl iodides, p‐iodoanisole and p‐
iodotoluene. Very good results were obtained, as shown
in Figure 8.
Having optimized the conditions for 3R synthesis in
hand, the second step of the tandem reaction was studied
without the isolation of 3R. First, reductive Heck cou-
pling was carried out, in order to fabricate saturated
non‐symmetric ketone 6RR'. Another portion of the aryl
iodide 2R' and the NPr3 amine as a reducing agent were
3.4 | Tandem synthesis of 4RR'
The process presented in Figure 9 led to the saturated
non‐symmetric ketone 6RR' as the main product, while
the unsaturated ketone 4RR' was formed in a smaller

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WIRWIS AND TRZECIAK
FIGURE 9 Synthesis of β,β‐diaryl‐2‐
butanones under MW conditions in the
presence of NPr3
TABLE 3 Results of tandem Heck reactions with different aryl iodides and NPr3 as a reducing agent
Entry
NPr3 [mmol]
R
R'
Conversion 3R [%]
t [h]
6RR' [%]
4RR'(E/Z) [%]
1
2
1.25
1.25
1.58
1.25
1.58
1.25
1.58
1.25
1.58
1.58
H
H
OMe
OMe
OMe
Me
94
95
2
3
3
3
3
3
3
3
3
3
57
69
77
83
81
82
80
69
76
63
24/13
19/7
13/8
11/6
12/7
9/4
3
H
98
4
H
100
100
95
5
H
Me
6
Me
Me
Me
Me
OMe
H
7
H
96
8/8
8
OMe
OMe
H
98
10/19
10/14
16/15
9
100
94
10
Reaction conditions: Step I: 2.01 mmol 3‐buten‐2‐one 1.34 mmol ArI – 2R; 0.5 mol% Pd (OAc)2; 1.25 mmol NaHCO3; 1 hr; 120 °C; 2.5 cm3 DMF/H2O = 3/2;
MW; 0.5–3 bar
Step II: 1.34 mmol ArI‐2R', 120 °C; 2–3 hr; MW
quantity. In the next step of our studies, attempts were
undertaken to reverse the reaction selectivity by changing
the reaction conditions.
Two different protocols were tested for this purpose
(Figures 10 and 11). In both of them, the substrate 3R
was obtained according to an optimized procedure with
MW irradiation with a yield of 94%. Under the first
method, 4RR' was prepared using conventional heating
(Figure 10). It was found that the formation of the unsatu-
rated ketone 4RR' is strongly dependent on the kind
of base, and in these experiments carbonates of group I
elements were used. In contrast to amines, carbonates
have no reducing properties, and they therefore promoted
the formation of Heck products, 4RR'.
FIGURE 10 Synthesis of 4‐(4‐
methoxyphenyl)‐4‐phenyl‐3‐buten‐2‐ones
with conventional heating in the presence
of an inorganic base

WIRWIS AND TRZECIAK
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FIGURE 11 Synthesis of β,β‐diaryl‐3‐
buten‐2‐ones under MW conditions in the
presence of a K2CO3 base
The introduction of a new portion of the base and p‐
iodoanisole to the DMF/H2O solution containing 3R
obtained in the first step and heating it for ca. 16 hr made
it possible to obtain 4RR' in a moderate to very good yield
(Figure 10, Table 4). The data presented in Table 4 show
that potassium bases were better that sodium ones, and
K2CO3 was superior to KHCO3. Very similar results, ca.
80% of 4RR', were obtained in DMF/H2O mixtures in
4/1 and 3/2 ratios. The yield of 6RR' was as low as 3–
8%. The desired product, 4RR', was obtained with good
yield in the tandem reaction presented in Figure 10; how-
ever, the second step of this process was relatively slow
and reaction time as long as 16 hr was needed. Therefore,
an improvement of this procedure was tested based on
using MW irradiation in both steps (Figure 11).
As can be concluded from the data presented in Table 5,
the coupling of 3R with p‐iodoanisole was quite efficient
and, already after 2 hr, 97% of 4RR' was obtained
(Table 5, entry 1). When 3R reacted with p‐iodotoluene,
a lower yield of 4RR', 69%, was achieved after 2 hr. It
increased to 87% when a larger amount of K2CO3 was used
(Table 5, entry 4). Even better results, 95% of 4RR', were
obtained after 3 hr of the reaction (Table 5, entry 3). Inter-
estingly, the introduction of iodide substrates in a reversed
order (R = Me, R' = H) gave a lower yield of the same prod-
uct. In contrast, a very good yield of 4RR' (94%) was
TABLE 5 Results for tandem Heck reactions with different aryl
iodides and a K2CO3 base
K2CO3
Entry [mmol] R R'
Conversion t
3R [%]
4RR'(E/Z) 6RR'
[h] [%] [%]
1
2
3
4
5
6
7
8
1.25
1.25
1.25
1.58
1.25
1.25
1.25
1.25
H
H
H
H
OMe 100
2
2
3
2
2
3
2
3
65/32
49/20
61/34
55/32
29/46
30/43
18/45
33/61
3
2
‐
Me 71
Me 95
Me 89
2
‐
Me H
Me H
75
73
‐
Me OMe 66
Me OMe 94
3
‐
Reaction conditions: Step I: 1.34 mmol ArI‐2R; 2.01 mmol 3‐buten‐2‐one;
0.5 mol% Pd (OAc)2; 1.25 mmol NaHCO3; 120 °C; 1 hr; DMF/H2O = 3/2;
MW, 0.5–3 bar
Step II: 1.34 mmol ArI‐2R'; 120 °C; 2–3 hr; MW
obtained when R = Me and R' = OMe, indicating the elec-
tronic effect of the substituents (Table 5, entry 8).
Considering the stereoselectivity, E/Z ratio for 4RR' iso-
mers changed when the order of iodides introduction was
changed. In the reaction with R = H and R' = Me the iso-
mer E dominated and E/Z ratio was equal ca. 2 (Table 5,
entry 2–4). However in the reverse sequence, with
R = Me and R' = H, E/Z ratio was lower than 1 (Table 5,
entry 5,6). Thus, the structure of intermediate 3R (E) was
not preserved during the second arylation performed
according to Figure 11. In contrast, the E isomer was
formed as the main one under conditions presented on
Figure 9. The mixtures of stereoisomers were also obtained
TABLE 4 The effect of different inorganic bases on the yield of
4RR' in tandem Heck arylation
Conversion
3R [%]
4RR'(E/Z)
[%]
6RR'
[%]
DMF/H2O
Base
4/1
4/1
4/1
3/2
22
54
85
86
NaHCO3
KHCO3
K2CO3
11/7
4
4
3
8
[1]
in chalcones arylation with Pd (OAc)2 and P(o‐Tol)3.
34/16
56/26
52/26
K2CO3
4 | CONCLUSIONS
Reaction conditions: Step I: 1.34 mmol ArI‐2R; 1.34 mmol 3‐buten‐2‐one;
0.5 mol% Pd (OAc)2; 1.25 mmol NaHCO3; 120 °C; 6 hr
New, efficient palladium‐catalyzed tandem methods for
the preparation of 4,4‐diarylbutanones and 4,4‐diaryl‐3‐
Step II: 1.34 mmol ArI‐2R'; 1.25 mmol base, 120 °C; 16 hr

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WIRWIS AND TRZECIAK
butenones using MW heating have been developed. Each
of the methods consists of two reactions proceeding one
after the other in the same vessel with the same ligand‐
free catalyst and with 4‐aryl‐3‐buten‐2‐one (3R) as an
intermediate.
ORCID
Anna M. Trzeciak https://orcid.org/0000-0002-4388-2109
REFERENCES
Advantageously, high yields of non‐symmetric
diarylketones were obtained in 2–3 hr from methyl vinyl
ketone and aryl iodides without the isolation of 3R. The
reactions were catalyzed by Pd (OAc)2 (0.5 mol%) without
additional ligands or additives. For comparison, the
arylation of MVK with iodobenzene was completed (74–
83%) in 24 hr at 100 °C using conventional heating.[19]
The positive effect of MW in the conjugate addition and
the Heck coupling was only shortly noted earlier.[27]
Recently arylation of chalcones was completed in 8 h
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ACKNOWLEDGEMENTS
Financial support of National Science Centre (NCN,
Poland) with grant 2014/15/B/ST5/02101 is gratefully
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SUPPORTING INFORMATION
Additional supporting information may be found online
in the Supporting Information section at the end of the
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How to cite this article: Wirwis A, Trzeciak AM.
Ligand‐free palladium‐catalyzed tandem pathways
for the synthesis of 4,4‐diarylbutanones and 4,4‐
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