Boron Trifluoride-Promoted Indium(III) Triflate-Catalyzed Sequential One-Pot Synthesis of (1,2-Diaryl-2-oxoethyl)malonates from trans-2-Aryl-3-nitrocyclopropane-1,1-dicarboxylates and Activated Arenes

Article abstract of DOI:10.1002/adsc.201500143

A sequential one-pot synthesis of Michael adducts of aroylmethylidenemalonates with activated aromatics is described. The method involves treatment of trans-2-aryl-3-nitro-cyclopropane-1,1-dicarboxylates with boron trifluoride etherate to form aroylmethyl

Full text of DOI:10.1002/adsc.201500143

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DOI: 10.1002/adsc.201500143
Boron Trifluoride-Promoted Indium(III) Triflate-Catalyzed
Sequential One-Pot Synthesis of (1,2-Diaryl-2-oxoethyl)malonates
from trans-2-Aryl-3-nitrocyclopropane-1,1-dicarboxylates and
Activated Arenes
Thangavel Selvia and Kannupal Srinivasana,*
a
School of Chemistry, Bharathidasan University, Tiruchirappalli – 620 024, Tamil Nadu, India
Fax: (+91)-431-240-7045; phone: (+91)-431-240-7053-538; e-mail: srinivasank@bdu.ac.in
Received: February 11, 2015; Revised: April 11, 2015; Published online: June 10, 2015
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/adsc.201500143.
Abstract: A sequential one-pot synthesis of Michael to the same reaction vessel. To prove the synthetic
adducts of aroylmethylidenemalonates with activated potential of the resulting Michael adducts, one of the
aromatics is described. The method involves treat- adducts was transformed into a pharmaceutically in-
ment of trans-2-aryl-3-nitro-cyclopropane-1,1-dicar- teresting dihydropyridazinone derivative.
boxylates with boron trifluoride etherate to form ar-
oylmethylidenemalonates in situ and then addition of
activated aromatics such as indoles, carbazole, pyr- Keywords: aromatic substitution; C C bond forma-
role, thiophenes, methoxybenzenes and benzodioxole tion; (1,2-diaryl-2-oxoethyl)malonates; Lewis acids;
followed by a catalytic amount of indium(III) triflate Michael addition; synthetic methods
À
Introduction
applications of 2-aryl-3-nitro-cyclopropane-1,1-dicar-
boxylates 1 (Scheme 1).[10] Upon treatment with
The rich and diverse reactivity of donor-acceptor cy- BF3·OEt2 or SnCl4, these nitrocyclopropanedicarboxy-
clopropanes has made them one of the most popular lates form aroylmethylidenemalonates (2) which serve
building blocks in organic synthesis.[1] They undergo as potential building blocks for various heterocy-
numerous ring-opening,[2] ring-enlargement[3] and an- cles.[10] During the course of our research, we ob-
nulation reactions[4] providing access to an assortment served that nitrocyclopropanedicarboxylate 1a when
of useful acyclic and cyclic compounds including natu-
ral products. Among various donor-acceptor cyclopro-
panes, nitro-substituted ones exhibit unique reactivity
and they often undergo ring-opening/expansion reac-
tions and rarely take part in annulation reactions.[5]
Nevertheless, a considerable amount of attention has
been paid to exploit the synthetic potential of differ-
ent types of nitro-substituted donor-acceptor cyclo-
propanes. Charette and co-workers have studied the
nucleophilic ring-opening reactions of 2-aryl-1-nitro-
cyclopropanecarboxylates for the synthesis of a-chiral
ethers and amines[6] and pyrroles.[7] The Werz group
has investigated the ring-enlargement reactions of this
type of cyclopropanes for the preparation of cyclic ni-
tronates (isooxazoline N-oxides).[8] Recently, Mattson
et al., have reported the first ever annulation reaction
of these cyclopropanes with nitrones as an access to
highly functionalized oxazinanes.[9] In this line, our
Scheme 1. Formation of aroylmethylidenemalonates and
group is focusing attention on exploring the synthetic subsequent Michael addition reaction.
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Thangavel Selvi and Kannupal Srinivasan
Table 1. Synthesis of Michael adducts from 1a using various
activated aromatics.[a,b]
Scheme 2. Methods of synthesis of Michael adducts of aroyl-
methylidenemalonates with activated aromatics.
reacted with thiophene-2-acetonitrile (3) in the pres-
ence of SnCl4 gave a b-ketomalonate 4 by the Michael
addition reaction of 3 to the in situ generated diethyl
benzoylmethylidenemalonate (2a) (Scheme 1).[10b]
Yamazaki and co-workers have extensively investi-
gated the synthetic potential of ethenetricarboxylates
5, including related aroylmethylidenemalonate 2a
[Scheme 2, Eq. (1)].[11] In their study, the ene
tri(di)esters 5/2a, prepared by the Wittig reaction of
oxomalonates with the corresponding triphenylmethy-
lenephosphoranes, have been subjected to asymmetric
Michael addition reactions with activated aromatic
compounds such as indoles, pyrroles and furans in the
presence of Cu(OTf)2 and chiral ligands to obtain the
Michael adducts 6.[11c,f] Obviously, our observation
outlined in Scheme 1 suggested to us that similar Mi-
chael adducts 7 could be obtained in a sequential
one-pot manner by the treatment of nitrocyclopro-
panedicarboxylates 1 with activated aromatics in the
presence of Lewis acids [Scheme 2, Eq. (2)]. Inspired
by the fact that b-ketomalonates are resourceful syn-
thetic intermediates,[12] we set out to investigate the
scope of the one-pot synthesis in detail as such
a study could furnish a number of synthetically useful
Michael adducts of aroylmethylidenemalonates with
activated aromatics.
[a]
Isolated yields.
Furan gave a complicated mixture.
Time in parenthesis indicates the time required for the
[b]
[c]
second step.
Yield obtained using SnCl4 (24 h).
[d]
Results and Discussion
We began the study by reacting nitrocyclopropanedi-
carboxylate 1a with indole (8a) (Table 1, entry 1). for thiophene-2-acetonitrile (3), Scheme 1],[10b] to our
When an equimolar mixture of 1a and 8a is heated surprise, the starting materials did not undergo any
under reflux in the presence of SnCl4 (1 equiv.) in 1,2- change even after 24 h. We reasoned that this might
dichloroethane [as per the conditions reported earlier be due to the strong coordination of SnCl4 to the
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Boron Trifluoride-Promoted Indium(III) Triflate-Catalyzed Sequential One-Pot Synthesis
Table 2. Synthesis of Michael adducts from various nitrocyclopropanedicarboxylates and representative activated
aromatics.[a]
[a]
Isolated yields.
[b]
Time in parenthesis indicates the total time required for both the steps.
indole nitrogen and hence we switched the Lewis acid the present reaction conditions. The reaction afforded
to BF3·OEt2 for effecting the reaction. Although 1a a higher yield of 4 (88%) as compared with the yield
was completely converted into diethyl benzoylmethy- (75%) obtained earlier using SnCl4 (Scheme 1). We
lidenemalonate (2a) with BF3·OEt2, the subsequent also tested the reactions of 1a with 2-bromothiophene
Michael addition reaction did not take place. Since (8g) and benzodioxole (8j) (entries 7 and 10) using
In(OTf)3 is a well-known catalyst for various organic SnCl4; even though the expected Michael adducts 7g
transformations,[13] we envisaged that by adding a cata- and 7j were produced in both cases, their yields (68%
lytic amount of In(OTf)3 to the reaction mixture after and 59%, respectively) were consistently low. Thus,
the formation of 2a, the desired result could be ach- the use of BF3·OEt2 and then In(OTf)3 seems to
ieved. Accordingly, when 1a was treated with effect the transformation more efficiently than using
BF3·OEt2 (1 equiv.) in DCM, it formed 2a in situ after SnCl4 alone. We also screened a number of other
24 h (judged by TLC) and then indole was added to Lewis acids [AlCl3, FeCl3, InCl3, TiCl4, ZnCl2, AgOTf,
the same reaction flask followed by In(OTf)3 Cu(OTf)2, Sc(OTf)3, Yb(OTf)3, Zn(OTf)2] under dif-
(5 mol%). Pleasingly, the reaction furnished the ex- ferent conditions, but none of them gave any reasona-
pected Michael adduct 3a in an excellent yield of ble results. It is worthwhile to mention that Yamazaki
91% (Table 1, entry 1). Satisfied with the results, we and co-workers had not used carbazole, thiophenes
started reacting 1a with other activated aromatics and benzodioxole previously as Michael partners in
such as 5-methoxyindole (8b), carbazole (8c), pyrrole their work.[11]
(8d), thiophene (8e), 2-methylthiophene (8f), 2-bro-
Next, we examined the scope of the reaction for ni-
mothiophene (8g), anisole (8h), 1,2-dimethoxyben- trocyclopropanedicarboxylates 1 having different aro-
zene (8i) and benzodioxole (8j) under the reaction matic rings with representative activated aromatics,
conditions (entries 2–10). In all cases, the expected namely, indole (8a), 2-bromothiophene (8g) and ben-
Michael adducts 7b–j were produced in good to excel- zodioxole (8j) (Table 2). The reactions tolerated
lent yields. We also repeated the reaction between 1a phenyl rings substituted with electron-releasing and
and thiophene-2-acetonitrile (3) (see Scheme 1) under halogen substituents, bulky naphthyl ring and hetero-
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Thangavel Selvi and Kannupal Srinivasan
Scheme 4. A synthetic application of Michael adduct 7i.
present study could serve as potential precursors for
this class of heterocycles. To prove this point, we
treated the Michael adduct 7i with hydrazine hydrate
in refluxing n-BuOH for 3 h, which afforded the dihy-
dropyridazinone derivative 9 in 81% yield through cy-
clocondensation and decarbethoxylation (Scheme 4).
Conclusions
In summary, we have developed a sequential one-pot
synthesis of Michael adducts of aroylmethylidenemal-
onates with the activated aromatics in the presence of
Lewis acids. Accordingly, the treatment of trans-
2-aryl-3-nitrocyclopropane-1,1-dicarboxylates
with
boron trifluoride etherate generates aroylmethyli-
denemalonates in situ and the addition of activated
aromatics such as indoles, carbazole, pyrrole, thio-
phenes, methoxybenzenes and benzodioxole followed
by a catalytic amount of indium(III) triflate to the
same reaction vessel gives Michael adducts of
Scheme 3. Synthesis of mono-and bis-Michael adducts using
2,2’-bithiophene.
aromatic thienyl ring on the nitrocyclopropanedicar- aroylmethylidenemalonates. These Michael adducts
boxylates. It may be noted that indole, thiophene and are versatile synthetic precursors as exemplified by
benzodioxole ring systems are found in numerous nat- the synthesis of a pharmaceutically interesting dihy-
ural products, drug/drug candidates and functional dropyridazinone derivative. Work is underway to de-
materials.[14]
velop a chiral version of the methodology.
We envisaged that when 2,2’-bithiophene is used as
an activated aromatic in the one-pot synthesis, mono-
and bis-Michael adducts could be obtained by varying Experimental Section
the amount of nitrocyclopropanedicarboxylates. Thus,
when 1.1 equiv. of phenylnitrocyclopropanedicarboxy- General Methods
late 1a or 2-thienylnitrocyclopropanedicarboxylate 1e
Melting points were determined by the open capillary tube
was employed in the transformation, the mono-Mi-
chael adducts 7u and 7v were produced in 89 and
72% yields, respectively (Scheme 3). On the other
hand, when 2.2 equiv. of 1a were used, the corre-
sponding bis-Michael adduct 7w was produced in
85% yield. It is worthy to note that many bithiophene
derivatives find use as active materials in organic
electronics.[15]
With the availability of a variety of Michael adducts
of aroylmethylidenemalonates with activated aromat-
ics, we next focused our attention on probing their
synthetic potential. The dihydropyridazinone is an im-
portant heterocyclic motif found in numerous cardio-
tonic agents including the drugs, levosimendan and pi-
method and are uncorrected. The H and 13C NMR spectra
1
were recorded on a 400 MHz NMR spectrometer. High res-
olution mass spectra (ESI) were recorded on a Q-TOF mass
spectrometer. IR spectra were recorded on an FT-IR spec-
trometer. Low resolution mass spectra (ESI) were recorded
on an LC mass spectrometer. Elemental analyses were per-
formed on a CHN analyzer. Thin layer chromatography
(TLC) was performed on pre-coated alumina sheets and de-
tected under UV light. Silica gel (100–200 mesh) was used
for column chromatography.
General Procedure for the Synthesis of Michael
Adducts 7a–w
To a solution of nitrocyclopropane 1 (1 mmol) (in the case
mobendan.[16] The Michael adducts prepared in the of 7w, 2.2 equiv, of 1a were used) in dichloromethane
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Boron Trifluoride-Promoted Indium(III) Triflate-Catalyzed Sequential One-Pot Synthesis
(5 mL) was added BF3·OEt2 (0.13 mL; 1 mmol) at room
temperature. The reaction mixture was stirred at room tem-
perature until the starting material disappeared completely
(as judged by TLC). To the same reaction flask, activated ar-
omatic 8 (1.1 mmol) was added followed by In(OTf)3
(28 mg; 5 mol%) and the reaction mixture was stirred at
room temperature. After completion of the reaction, it was
quenched with water. The organic layer was separated,
washed with water, dried (anhydrous Na2SO4) and the sol-
vent was removed under reduced pressure. The crude prod-
uct 7 was purified by column chromatography using 5–10%
ethyl acetate/hexane.
Diethyl 2-(2-oxo-2-phenyl-1-thiophen-2-yl-ethyl)malonate
(7e): yellow oil; yield: 281 mg (78%); H NMR (400 MHz,
1
CDCl3): d=8.02 (d, J=8.4 Hz, 2H), 7.51 (t, J=7.2 Hz, 1H),
7.41 (t, J=7.6 Hz, 2H), 7.17 (d, J=4.8 Hz, 1H), 6.95 (d, J=
3.2 Hz, 1H), 6.88 (t, J=4.4 Hz, 1H), 5.61 (d, J=11.2 Hz,
1H), 4.46 (d, J=11.6 Hz, 1H), 4.19–4.11 (m, 2H), 4.09–4.01
(m, 2H), 1.19 (t, J=7.2 Hz, 3H), 1.09 (t, J=7.2 Hz, 3H);
13C NMR (100 MHz, CDCl3): d=196.3, 167.8, 136.3, 135.6,
133.3, 128.9, 128.6, 127.6, 127.3, 126.2, 62.0, 61.6, 56.5, 47.4,
13.9, 13.85; IR (KBr): n=1733 (C=O, ester), 1684 (C=O)
cmÀ1; MS (ESI): m/z=383.09 [M+Na+]; anal. calcd. for
C19H20O5S: C 63.32, H 5.59; found: C 63.40, H 5.73.
Diethyl
2-[1-(1H-indol-3-yl)-2-oxo-2-phenylethyl]malo-
Diethyl
2-[1-(5-methylthiophen-2-yl)-2-oxo-2-phenyl-
nate (7a):[11c] yellow oil; yield: 357 mg (91%); 1H NMR
(400 MHz, CDCl3): d=8.26 (s, 1H), 7.98 (t, J=4.4 Hz, 2H),
7.79–7.76 (m, 1H), 7.44–7.40 (m, 1H), 7.33–7.25 (m, 3H),
7.17–7.14 (m, 2H), 7.03 (d, J=2.4 Hz, 1H), 5.64 (d, J=
11.6 Hz, 1H), 4.54 (d, J=11.6 Hz, 1H), 4.21–4.15 (m, 2H),
3.85–3.74 (m, 2H), 1.22 (t, J=7.2 Hz, 3H), 0.80 (t, J=
7.0 Hz, 3H); 13C NMR (100 MHz, CDCl3): d=197.3, 168.5,
136.3, 136.0, 132.9, 128.7, 128.5, 126.1, 124.0, 122.4, 120.1,
119.0, 111.3, 109.2, 61.8, 61.4, 55.8, 44.1, 14.0, 13.5.
ethyl]malonate (7f): yellow oil; yield: 325 mg (87%);
1H NMR (400 MHz, CDCl3): d=8.01 (d, J=8.8 Hz, 2H),
6.88 (d, J=8.8 Hz, 2H), 6.71 (t, J=3.2 Hz, 1H), 6.49 (t, J=
1.6 Hz, 1H), 5.45 (d, J=11.2 Hz, 1H), 4.40 (d, J=11.2 Hz,
1H), 4.17–4.02 (m, 4H), 2.33 (s, 3H), 1.17 (t, J=7.2 Hz,
3H), 1.10 (t, J=7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3):
d=194.7, 167.94, 167.85, 163.7, 140.6, 134.2, 131.3, 128.5,
127.3, 125.3, 113.8, 61.8, 61.6, 56.4, 47.3, 15.3, 13.91, 13.87;
IR (KBr): n=1740 (C=O, ester), 1674 (C=O) cmÀ1; HR-MS
(ESI): m/z=375.1261, calcd. for C20H22O5S: 375.1261 [M+
H+].
Diethyl 2-[1-(5-methoxy-1H-indol-3-yl)-2-oxo-2-phenyl-
ethyl]malonate (7b): dark brown oil; yield: 376 mg (89%);
1H NMR (400 MHz, CDCl3): d=8.37 (s, 1H), 7.98 (d, J=
7.6 Hz, 2H), 7.41 (t, J=7.4 Hz, 1H), 7.31 (t, J=7.6 Hz, 2H),
7.19 (d, J=2.0 Hz, 1H), 7.13 (d, J=8.8 Hz, 1H), 6.96 (d, J=
2.4 Hz, 1H), 6.80 (q, J=6.4 Hz, 1H), 5.59 (d, J=11.2 Hz,
1H), 4.54 (d, J=11.6 Hz, 1H), 4.21–4.13 (m, 2H), 3.87 (s,
3H), 3.85–3.78 (m, 2H), 1.21 (t, J=7.0 Hz, 3H), 0.81 (t, J=
7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3): d=197.3, 168.7,
168.6, 154.4, 136.1, 132.9, 131.5, 128.7, 128.5, 126.6, 124.8,
112.7, 112.2, 108.6, 100.6, 61.8, 61.4, 55.9, 55.6, 44.4, 14.0,
13.5; IR (KBr): n=3394 (N-H), 1732 (C=O, ester), 1679 (C=
O) cmÀ1; MS (ESI): m/z=446.07 [M+Na+]; anal. calcd. for
C24H25NO6: C 68.07, H 5.95, N 3.31; found: C 68.26, H 5.89,
N 3.36.
Diethyl
2-[1-(5-bromothiophen-2-yl)-2-oxo-2-phenyl-
ethyl]malonate (7g): yellow oil; yield: 390 mg (89%);
1H NMR (400 MHz, CDCl3): d=8.01 (d, J=7.6 Hz, 2H),
7.55 (t, J=7.4 Hz, 1H), 7.44 (t, J=7.4 Hz, 2H), 6.84 (d, J=
3.2 Hz, 1H), 6.72 (d, J=3.2 Hz, 1H), 5.51 (d, J=11.2 Hz,
1H), 4.41 (d, J=11.2 Hz, 1H), 4.18–4.07 (m, 4H), 1.21–1.13
(m, 6H); 13C NMR (100 MHz, CDCl3): d=195.8, 167.6,
167.5, 137.9, 135.4, 133.6, 130.1, 128.9, 128.7, 128.1, 112.8,
62.1, 61.8, 56.3, 47.5, 13.9; IR (KBr): n=1745 (C=O, ester),
1679 (C=O) cmÀ1; HR-MS (ESI): m/z=439.0209, calcd. for
C19H19BrO5S: 439.0209 [M+H+].
Diethyl 2-[1-(4-methoxyphenyl)-2-oxo-2-phenylethyl]mal-
onate (7h): yellow oil; yield: 353 mg (92%); 1H NMR
(400 MHz, CDCl3): d=7.97 (d, J=8.4 Hz, 2H), 7.47 (t, J=
7.4 Hz, 1H), 7.38 (t, J=7.4 Hz, 2H), 7.22 (d, J=8.4 Hz,
2H), 6.80 (d, J=8.8 Hz, 2H), 5.27 (d, J=11.2 Hz, 1H), 4.41
(d, J=11.2 Hz, 1H), 4.21–4.12 (m, 2H), 4.00 (q, J=7.2 Hz,
2H), 3.72 (s, 3H), 1.21 (t, J=7.2 Hz, 3H), 1.01 (t, J=7.2 Hz,
3H); 13C NMR (100 MHz, CDCl3): d=197.5, 168.2, 168.1,
159.3, 136.0, 133.0, 130.1, 128.9, 128.5, 126.4, 114.5, 61.8,
61.4, 56.0, 55.2, 52.1, 13.9, 13.8; IR (KBr): n=1733 (C=O,
ester), 1681 (C=O) cmÀ1; MS (ESI): m/z=407.13 [M+Na+];
anal. calcd. for C22H24O6: C 68.74, H 6.29; found: C 68.68, H
6.19.
Diethyl 2-[1-(9H-carbazol-3-yl)-2-oxo-2-phenylethyl]mal-
1
onate (7c): yellow semisolid; yield: 403 mg (91%); H NMR
(400 MHz, CDCl3): d=8.19 (s, 1H), 8.01 (t, J=15.6 Hz,
4H), 7.41–7.18 (m, 8H), 5.50 (d, J=11.6 Hz, 1H), 4.56 (d,
J=11.2 Hz, 1H), 4.20–4.13 (m, 2H), 3.90–3.82 (m, 2H), 1.22
(t, J=7.4 Hz, 3H), 0.86 (t, J=7.0 Hz, 3H); 13C NMR
(100 MHz, CDCl3): d=197.9, 168.5, 168.3, 139.9, 139.1,
136.1, 133.0, 129.0, 128.5, 126.5, 126.2, 125.2, 123.9, 122.9,
120.9, 120.4, 119.6, 111.2, 110.7, 61.9, 61.4, 56.6, 53.2, 14.0,
13.8; IR (KBr): n=3394 (N-H), 1733 (C=O, ester), 1677 (C=
O) cmÀ1
;
HR-MS (ESI): m/z=444.1809, calcd. for
C27H25NO5: 444.1806 [M+H+].
Diethyl 2-[1-(3,4-dimethoxyphenyl)-2-oxo-2-phenylethyl]-
malonate (7i): brown oil; yield: 344 mg (83%); 1H NMR
(400 MHz, CDCl3): d=7.99 (d, J=8.4 Hz, 2H), 7.48 (t, J=
7.4 Hz, 1H), 7.39 (t, J=7.6 Hz, 2H), 6.87 (d, J=8.4 Hz,
1H), 6.76 (t, J=1.0 Hz, 2H), 5.28 (d, J=11.6 Hz, 1H), 4.42
(d, J=11.6 Hz, 1H), 4.21–4.14 (m, 2H), 3.98 (q, J=7.2 Hz,
2H), 3.83 (s, 3H), 3.80 (s, 3H), 1.21 (t, J=7.2 Hz, 3H), 1.03
(t, J=7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3): d=197.6,
168.2, 168.1, 149.3, 148.8, 136.1, 133.1, 128.8, 128.5, 126.8,
121.7, 111.54, 111.50, 61.8, 61.4, 56.01, 55.96, 55.8, 52.5,
13.93, 13.88; IR (KBr): n=1733 (C=O, ester), 1680 (C=O)
cmÀ1; MS (ESI): m/z=437.16 [M+Na+]; anal. calcd. for
C23H26O7: C 66.61, H 6.32; found: C 66.80, H 6.16.
Diethyl 2-[2-oxo-2-phenyl-1-(1H-pyrrol-2-yl)-ethyl]malo-
nate (7d): dark brown oil; yield: 309 mg (90%); 1H NMR
(400 MHz, CDCl3): d=8.40 (s, 1H), 8.01 (d, J=7.2 Hz, 2H),
7.52 (t, J=7.4 Hz, 1H), 7.41 (t, J=7.8 Hz, 2H), 6.68 (q, J=
2.4 Hz, 1H), 6.07–6.03 (m, 2H), 4.95 (d, J=11.2 Hz, 1H),
4.40 (d, J=11.2 Hz, 1H), 4.18–4.04 (m, 4H), 1.18 (t, J=
7.2 Hz, 3H), 1.12 (t, J=7.2 Hz, 3H); 13C NMR (100 MHz,
CDCl3): d=197.2, 168.4, 168.0, 135.9, 133.3, 128.8, 128.6,
123.4, 119.1, 109.2, 109.0, 61.9, 61.7, 55.5, 46.0, 13.9; IR
(KBr): n=3392 (N-H), 1731 (C=O, ester), 1676 (C=O) cmÀ1
;
MS (ESI): m/z=366.13 [M+Na+]; anal. calcd. for
C19H21NO5: C 66.46, H 6.16, N 4.08; found: C 66.56, H 6.29,
N 4.16.
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Diethyl 2-(1-benzo[1,3]dioxol-5-yl-2-oxo-2-phenylethyl)-
malonate (7j): yellow oil; yield: 298 mg (75%); 1H NMR
(400 MHz, CDCl3): d=7. 98 (d, J=8.0 Hz, 2H), 7.49 (t, J=
7.4 Hz, 1H), 7. 40 (t, J=7.4 Hz, 2H), 6.78 (s, 2H), 6.69 (d,
J=8.4 Hz, 1H), 5.89 (d, J=6.8 Hz, 2H), 5.23 (d, J=11.2 Hz,
1H), 4.37 (d, J=11.2 Hz, 1H), 4.20–4.13 (m, 2H), 4.01 (q,
J=7.2 Hz, 2H), 1.21 (t, J=7.2 Hz, 3H), 1.06 (t, J=7.2 Hz,
3H); 13C NMR (100 MHz, CDCl3): d=197.3, 168.1, 168.0,
148.1, 147.4, 135.9, 133.1, 128.9, 128.6, 128.0, 122.7, 109.0,
108.7, 101.2, 61.9, 61.4, 56.0, 52.4 13.93, 13.90; IR (KBr): n=
1738 (C=O, ester), 1670 (C=O) cmÀ1; HR-MS (ESI): m/z=
399.1440, calcd. for C22H22O7: 399.1438 [M+H+].
(100 MHz, CDCl3): d=190.3, 168.4, 168.3, 142.6, 136.3,
133.7, 132.7, 128.1, 126.2, 124.2, 122.4, 120.1, 118.9, 111.6,
109.2, 61.9, 61.5, 55.5, 45.5, 14.0, 13.5; IR (KBr): n=3390
(N-H), 1730 (C=O, ester), 1657 (C=O) cmÀ1; MS (ESI): m/
z=422.00 [M+Na+]; anal. calcd. for C21H21NO5S: C 63.14,
H 5.30, N 3.51; found: C 63.29, H 5.29, N 3.65.
Diethyl 2-[1-(5-bromothiophen-2-yl)-2-oxo-2-tolylethyl]-
malonate (7o): yellow oil; yield: 290 mg (62%); 1H NMR
(400 MHz, CDCl3): d=7.91 (d, J=7.6 Hz, 2H), 7.24 (d, J=
8.0 Hz, 2H), 6.82 (d, J=3.6 Hz, 1H), 6.71 (d, J=3.6 Hz,
1H), 5.49 (d, J=11.2 Hz, 1H), 4.40 (d, J=11.2 Hz, 1H),
4.18–4.05 (m, 4H), 2.38 (s, 3H), 1.19 (t, J=7.0 Hz, 3H), 1.14
(t, J=7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3): d=195.4,
167.7, 167.5, 144.6, 138.3, 132.8, 130.0, 129.5, 129.0, 128.0,
112.7, 62.0, 61.8, 56.2, 47.4, 21.7, 13.9; IR (KBr): n=1745
(C=O, ester), 1679 (C=O) cmÀ1; MS (ESI): m/z=475.02
[M+Na+]; anal. calcd. for C20H21BrO5S: C 52.99, H 4.67;
found: C 53.10, H 4.49.
Diethyl 2-[1-(5-bromothiophen-2-yl)-2-(4-chlorophenyl)-
2-oxo-ethyl]malonate (7p): yellow oil; yield: 321 mg (68%);
1H NMR (400 MHz, CDCl3): d=7.94 (d, J=8.4 Hz, 2H),
7.41 (t, J=8.4 Hz, 2H), 6.84 (d, J=4.0 Hz, 1H), 6.70 (d, J=
3.6 Hz, 1H), 5.44 (d, J=11.2 Hz, 1H), 4.39 (d, J=11.2 Hz,
1H), 4.19–4.06 (m, 4H), 1.20 (t, J=7.2 Hz, 3H), 1.14 (t, J=
7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3): d=194.7, 167.5,
167.4, 140.1, 137.5, 133.7, 130.3, 130.1, 129.1, 128.2, 113.0,
62.2, 61.9, 56.2, 47.5, 13.9; IR (KBr): n=1735 (C=O, ester),
1680 (C=O) cmÀ1; MS (ESI): m/z=494.96 [M+Na+]; anal.
calcd. for C19H18BrClO5S: C 48.17, H 3.83; found: C 48.40,
H 3.69.
Diethyl 2-[1-(5-bromothiophen-2-yl)-2-naphthalen-1-yl-2-
oxoethyl]malonate (7q): yellow oil; yield: 297 mg (61%);
1H NMR (400 MHz, CDCl3): d=8.38 (d, J=7.2 Hz, 1H),
8.17 (d, J=7.2 Hz, 1H), 7.97 (d, J=8.4 Hz, 1H), 7.83 (d, J=
8.4 Hz, 1H), 7.57–7.47 (m, 3H), 6.80 (d, J=4.0 Hz, 1H),
6.72 (d, J=3.6 Hz, 1H), 5.56 (d, J=11.2 Hz, 1H), 4.50 (d,
J=11.2 Hz, 1H), 4.20 (q, J=5.2 Hz, 2H), 4.16–4.07 (m,
2H), 1.23 (t, J=7.2 Hz, 3H), 1.14 (t, J=7.2 Hz, 3H);
13C NMR (100 MHz, CDCl3): d=198.5, 167.8, 167.5, 137.5,
134.4, 133.9, 133.30, 133.29, 130.8, 130.0, 128.4, 128.3, 126.5,
125.5, 124.3, 112.8, 62.2, 61.9, 56.1, 51.1, 14.0, 13.9; IR
(KBr): n=1745 (C=O, ester), 1658 (C=O) cmÀ1; HR-MS
(ESI): m/z=489.0369, calcd. for C23H21BrO5S: 489.0366
[M+H+].
Diethyl 2-[1-(5-bromothiophen-2-yl)-2-oxo-2-thiophen-2-
yl-ethyl]malonate (7r): white solid; yield: 333 mg (75%); mp
96–988C; 1H NMR (400 MHz, CDCl3): d=7.83 (d, J=
3.6 Hz, 1H), 7.64 (d, J=4.8 Hz, 1H), 7.11 (t, J=4.4 Hz,
1H), 6.84 (d, J=3.6 Hz, 1H), 6.76 (d, J=3.6 Hz, 1H), 5.30
(d, J=11.2 Hz, 1H), 4.53 (d, J=11.2 Hz, 1H), 4.21–4.03 (m,
4H), 1.18 (t, J=7.2 Hz, 3H), 1.12 (t, J=7.2 Hz, 3H);
13C NMR (100 MHz, CDCl3): d=188.4, 167.4, 167.3, 141.9,
138.0, 134.8, 133.4, 130.0, 128.4, 128.1, 112.8, 62.2, 61.9, 55.8,
49.0, 13.89, 13.87; IR (KBr): n=1745 (C=O, ester), 1655 (C=
O) cmÀ1; MS (ESI): m/z=466.96 [M+Na+]; anal. calcd. for
C17H17BrO5S2: C 45.85, H 3.85; found: C 45.90, H 3.99.
Diethyl 2-[1-benzo[1,3]dioxol-5-yl-2-(4-chlorophenyl)-2-
oxoethyl]malonate (7s): yellow oil; yield: 293 mg (68%);
1H NMR (400 MHz, CDCl3): d=7.90 (d, J=8.4 Hz, 2H),
7.34 (d, J=8.8 Hz, 2H), 6.76–6.67 (m, 3H), 5.87 (d, J=
6.8 Hz, 2H), 5.15 (d, J=11.6 Hz, 1H), 4.34 (d, J=11.2 Hz,
1H), 4.19–4.09 (m, 2H), 4.03–3.97 (m, 2H), 1.19 (t, J=
Diethyl
2-[1-(1H-indol-3-yl)-2-oxo-2-(4-methylphenyl)-
ethyl]malonate (7k): yellow oil; yield: 334 mg (82%);
1H NMR (400 MHz, CDCl3): d=8.18 (s, 1H), 7.90 (d, J=
8.0 Hz, 2H), 7.77 (t, J=4.4 Hz, 1H), 7.28 (d, J=3.6 Hz,
1H), 7.16–7.11 (m, 4H), 7.05 (q, J=2.4 Hz, 1H), 5.63 (d, J=
11.2 Hz, 1H), 4.53 (d, J=11.2 Hz, 1H), 4.24–4.14 (m, 2H),
3.85–3.74 (m, 2H), 2.30 (s, 3H), 1.22 (t, J=7.0 Hz, 3H), 0.81
(t, J=7.0 Hz, 3H); 13C NMR (100 MHz, CDCl3): d=196.9,
168.54, 168.49, 143.7, 136.2, 133.5, 129.2, 128.8, 126.2, 123.9,
122.4, 120.1, 119.0, 111.3, 109.6, 61.7, 61.3, 55.8, 44.0, 21.5,
14.0, 13.5; IR (KBr): n=3389 (N-H), 1732 (C=O, ester),
1675 (C=O) cmÀ1; MS (ESI): m/z=430.16 [M+Na+]; anal.
calcd. for C24H25NO5: C 70.74, H 6.18, N 3.44; found: C
70.60, H 6.29, N 3.53.
Diethyl
2-[2-(4-chlorophenyl)-1-(1H-indol-3-yl)-2-oxo-
ethyl]malonate (7l): dark brown oil; yield: 320 mg (75%);
1H NMR (400 MHz, CDCl3): d=8.52 (s, 1H), 7.90 (d, J=
8.4 Hz, 2H), 7.73 (q, J=3.2 Hz, 1H), 7.23 (d, J=8.4 Hz,
3H), 7.13 (q, J=3.2 Hz, 2H), 6.95 (d, J=2.4 Hz, 1H), 5.58
(d, J=11.2 Hz, 1H), 4.54 (d, J=11.2 Hz, 1H), 4.22–4.12 (m,
2H), 3.84–3.74 (m, 2H), 1.20 (t, J=7.2 Hz, 3H), 0.79 (t, J=
7.0 Hz, 3H); 13C NMR (100 MHz, CDCl3): d=196.2, 168.6,
168.5, 139.4, 136.3, 134.3, 130.1, 128.8, 126.0, 124.2, 122.5,
120.2, 118.7, 111.6, 108.6, 61.9, 61.5, 55.7, 44.3, 14.0, 13.5; IR
(KBr): n=3395 (N-H), 1731 (C=O, ester), 1680 (C=O) cmÀ1
;
MS (ESI): m/z=449.93 [M+Na+]; anal. calcd. for
C23H22ClNO5: C 64.56, H 5.18, N 3.27; found: C 64.63, H
5.29, N 3.32.
Diethyl
2-[1-(1H-indol-3-yl)-2-naphthalen-1-yl-2-oxo-
ethyl]malonate (7m): yellow oil; yield: 346 mg (78%);
1H NMR (400 MHz, CDCl3): d=8.36–8.33 (m, 1H), 8.15–
8.13 (m, 2H), 7.84 (d, J=8.0 Hz, 1H), 7.75–7.73 (m, 2H),
7.44–7.21 (m, 3H), 7.20–7.08 (m, 4H), 5.68 (d, J=11.2 Hz,
1H), 4.68 (d, J=11.2 Hz, 1H), 4.27–4.21 (m, 2H), 3.84–3.79
(m, 2H), 1.26 (t, J=7.0 Hz, 3H), 0.80 (t, J=7.0 Hz, 3H);
13C NMR (100 MHz, CDCl3): d=200.4, 168.7, 168.4, 136.2,
135.5, 133.8, 132.4, 130.8, 128.2, 127.6, 126.3, 126.2, 125.6,
124.4, 124.0, 122.4, 120.0, 119.1, 111.2, 108.6, 61.9, 61.4, 55.5,
47.6, 14.1, 13.5; IR (KBr): n=3392 (N-H), 1730 (C=O,
ester), 1678 (C=O) cmÀ1; MS (ESI): m/z=466.02 [M+Na+];
anal. calcd. for C27H25NO5: C 73.12, H 5.68, N 3.16; found:
C 73.30, H 5.65, N 3.05.
Diethyl 2-[1-(1H-indol-3-yl)-2-oxo-2-thiophen-2-ylethyl]-
malonate (7n): yellow semisolid; yield: 355 mg (89%); mp
86–888C; 1H NMR (400 MHz, CDCl3): d=8.58 (s, 1H),
7.77–7.74 (m, 2H), 7.43 (d, J=4.4 Hz, 1H), 7.25 (d, J=
8.0 Hz, 1H), 7.14 (d, J=2.4 Hz, 2H), 7.04 (s, 1H), 6.90 (d,
J=3.6 Hz, 1H), 5.46 (d, J=11.6 Hz, 1H), 4.54 (d, J=
11.2 Hz, 1H), 4.20–4.16 (m, 2H), 3.84–3.73 (m, 2H), 1.20 (t,
J=7.0 Hz, 3H), 0.78 (t, J=7.0 Hz, 3H); 13C NMR
2116
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Adv. Synth. Catal. 2015, 357, 2111 – 2118

FULL PAPERS
Boron Trifluoride-Promoted Indium(III) Triflate-Catalyzed Sequential One-Pot Synthesis
7.2 Hz, 3H), 1.04 (t, J=7.2 Hz, 3H); 13C NMR (100 MHz,
CDCl3): d=196.2, 168.1, 167.8, 148.2, 147.6, 139.6, 134.2,
130.3, 128.9, 127.6, 122.7, 108.9, 108.8, 101.3, 61.9, 61.5, 55.9,
52.4, 13.93, 13.89; IR (KBr): n=1740 (C=O, ester), 1658 (C=
O) cmÀ1; MS (ESI): m/z=455.09 [M+Na+]; anal. calcd. for
C22H21ClO7: C 61.05, H 4.89; found: C 61.20, H 5.01.
Diethyl 2-(1-benzo[1,3]dioxol-5-yl-2-oxo-2-thiophen-2-yl-
ethyl)malonate (7t): yellow oil; yield: 303 mg (75%);
1H NMR (400 MHz, CDCl3): d=7.54 (d, J=0.8 Hz, 1H),
7.22 (q, J=3.2 Hz, 1H), 6.83–6.79 (m, 2H), 6.72–6.69 (m,
1H), 6.48 (q, J=2.0 Hz, 1H), 5.90 (d, J=6.8 Hz, 2H), 5.03
(d, J=12.0 Hz, 1H), 4.36 (d, J=11.6 Hz, 1H), 4.19–4.13 (m,
2H), 4.03–3.97 (m, 2H), 1.20 (t, J=7.2 Hz, 3H), 1.04 (t, J=
7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3): d=186.1, 168.0,
167.8, 151.6, 148.0, 147.5, 146.9, 127.8, 122.7, 118.6, 112.5,
109.1, 108.6, 101.2, 62.0, 61.5, 55.0, 52.4, 13.87, 13.85; IR
(KBr): n=1732 (C=O, ester), 1684 (C=O) cmÀ1; MS (ESI):
m/z=427.08 [M+Na+]; anal. calcd. for C20H20O7S: C 59.40,
H 4.98; found: C 59.51, H 5.10.
5-(3,4-Dimethoxyphenyl)-6-phenyl-4,5-dihydro-2H-
pyridazin-3-one (9)
To a solution of Michael adduct 7i (1 mmol) in n-BuOH
(5 mL) was added hydrazine hydrate (1.1 mmol) and the re-
action mixture was heated under reflux. After completion of
the reaction (3 h), the solvent was removed under reduced
pressure and the residue was extracted with DCM. The or-
ganic layer was washed with water, dried (anhydrous
Na2SO4) and the solvent was removed. The crude product
was purified by column chromatography using 20–30% ethyl
acetate/hexane as eluent to afford 9 as a pale yellow solid;
yield: 251 mg (81%); mp 141–1438C. 1H NMR (400 MHz,
CDCl3): d=8.83 (s, 1H), 7.71–7.68 (m, 2H), 7.37–7.34 (m,
3H), 6.77–6.71 (m, 3H), 4.42 (dd, J=1.2 Hz, & 7.6 Hz, 1H),
3.83 (s, 3H), 3.81 (s, 3H), 2.99 (dd, J=7.6 Hz & 16.8 Hz,
1H), 2.80 (dd, J=1.2 Hz
&
16.8 Hz, 1H); 13C NMR
(100 MHz, CDCl3): d=166.1, 151.8, 149.6, 148.7, 135.3,
129.92, 129.86, 128.6, 126.2, 119.2, 111.8, 110.2, 55.91, 55.90,
39.5, 35.4; IR (KBr): n=3436 (N-H), 1693 (C=O), 1592 (C=
N) cmÀ1; MS (ESI): m/z=311.1 [M+H+]; anal. calcd. for
C18H18N2O3: C 69.66, H 5.85, N 9.03; found: C 69.50, H 5.90,
N 9.22.
Diethyl 2-(1-[2,2’]bithiophenyl-5-yl-2-oxo-2-phenylethyl)-
malonate (7u): yellow semisolid; yield: 393 mg (89%);
1H NMR (400 MHz, CDCl3): d=8.05 (d, J=7.6 Hz, 2H),
7.53 (t, J=7.4 Hz, 1H), 7.44 (t, J=7.6 Hz, 2H), 7.17 (d, J=
5.2 Hz, 1H), 7.08 (d, J=3.6 Hz, 1H), 6.95 (q, J=4.2 Hz,
2H), 6.87 (d, J=3.6 Hz, 1H), 5.56 (d, J=11.2 Hz, 1H), 4.48
(d, J=11.2 Hz, 1H), 4.22–4.05 (m, 4H), 1.20 (t, J=7.2 Hz,
3H), 1.13 (t, J=7.0 Hz, 3H); 13C NMR (100 MHz, CDCl3):
d=196.0, 167.7, 167.7, 138.4, 136.9, 135.5, 135.1, 133.5, 129.0,
128.7, 128.4, 127.8, 124.6, 123.9, 123.7, 62.1, 61.8, 56.3, 47.5,
Acknowledgements
The authors thank Science and Engineering Research Board
(SERB), India for financial support; DST-FIST for NMR fa-
cility at School of Chemistry, Bharathidasan University and
Sophisticated Analytical Instrumentation Facility (SAIF),
Lucknow for HR-MS. T.S. thanks Department of Science and
Technology (DST) for an INSPIRE fellowship.
13.9; IR (KBr): n=1752 (C=O, ester), 1654 (C=O) cmÀ1
;
MS (ESI): m/z=465.08 [M+Na+]; anal. calcd. for
C23H22O5S2: C 62.42, H 5.01; found: C 62.49, H 5.12.
Diethyl 2-(1-[2,2’]bithiophenyl-5-yl-2-oxo-2-thiophen-2-yl-
ethyl)malonate (7v): yellow oil; yield: 323 mg (72%);
1H NMR (400 MHz, CDCl3): d=7.81 (dd, J=0.8 & 4.0 Hz,
1H), 7.62 (dd, J=1.2 & 4.8 Hz, 1H), 7.16 (dd, J=1.2 &
5.2 Hz, 1H), 7.10–7.18 (m, 2H), 6.96–6.94 (m, 2H), 6.90 (d,
J=3.6 Hz, 1H), 5.36 (d, J=11.6 Hz, 1H), 4.45 (d, J=
11.6 Hz, 1H), 4.18–4.07 (m, 4H), 1.19 (t, J=7.0 Hz, 3H),
1.10 (t, J=7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3): d=
188.6, 167.54, 167.52, 142.1, 138.3, 136.8, 135.2, 134.7, 133.4,
128.39, 128.36, 127.8, 124.7, 123.9, 123.6, 62.1, 61.8, 55.9,
48.9, 14.0, 13.9; IR (KBr): 1746 (C=O, ester), 1655 (C=O)
cmÀ1; MS (ESI): m/z=471.04 [M+Na+]; anal. calcd. for
C21H20O5S3: C 56.23, H 4.49; found: C 56.40, H 4.63.
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1688C; H NMR (400 MHz, CDCl3): d=8.00 (d, J=7.6 Hz,
2H), 7.49 (t, J=6.8 Hz, 1H), 7.40 (t, J=7.6 Hz, 2H), 6.86–
6.82 (m, 2H), 5.53 (d, J=11.2 Hz, 1H), 4.43 (d, J=11.2 Hz,
1H), 4.17–4.06 (m, 4H), 1.17 (t, J=7.2 Hz, 3H), 1.10 (t, J=
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(C=O) cmÀ1; MS (ESI): m/z=741.18 [M+Na+]; anal. calcd.
for C38H38O10S2: C 63.49, H 5.33; found: C 63.60, H 5.29.
Adv. Synth. Catal. 2015, 357, 2111 – 2118
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
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