Monoallylation and benzylation of dicarbonyl compounds with alcohols catalysed by a cationic cobalt(iii) compound

Article abstract of DOI:10.1039/d0ra09778k

Monoallylation and monoalkylation of diketones and β-keto esters with allylic and benzylic alcohols catalysed by [Cp*Co(CH₃CN)₃][SbF₆]₂(I) are reported. The method does not require any additive and affords regioselective products. The mechanistic investigations were done byin situ¹H NMR spectroscopy as well as control experiments. It has been shown that reactions proceedviaη³-allyl complex formation or ally ether intermediate. The alkylation takes placeviaonly ether intermediate. The resulting allylated and alkylated products have been used for the synthesis of eleven new trisubstituted pyrazoles and one pyrazolone.

Full text of DOI:10.1039/d0ra09778k

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Monoallylation and benzylation of dicarbonyl
compounds with alcohols catalysed by a cationic
Cite this: RSC Adv., 2021, 11, 9235
cobalt(III) compound†
*
Mohan Chandra Sau, Smita Mandal and Manish Bhattacharjee
Monoallylation and monoalkylation of diketones and b-keto esters with allylic and benzylic alcohols
catalysed by [Cp*Co(CH3CN)3][SbF6]2 (I) are reported. The method does not require any additive and
affords regioselective products. The mechanistic investigations were done by in situ 1H NMR
spectroscopy as well as control experiments. It has been shown that reactions proceed via h3-allyl
complex formation or ally ether intermediate. The alkylation takes place via only ether intermediate. The
resulting allylated and alkylated products have been used for the synthesis of eleven new trisubstituted
pyrazoles and one pyrazolone.
Received 18th November 2020
Accepted 19th February 2021
DOI: 10.1039/d0ra09778k
rsc.li/rsc-advances
[(crotyl)Co(CO)3], and Na[Co(CO)4] have been shown to catalyse
allylation using ally formate, chloride, and acetate. However,
the conversions were found to be low.11a Similarly, cobalt(III)
Introduction
Allylation and alkylation of active methylene compounds are
essential in synthetic organic chemistry. Usually, allyl halides
and alkyl halides are used for allylation in the presence of
a base. However, these reactions are not atom economical or
green, as a large amount of salts is generated. Allylation and
alkylation using the corresponding alcohol are attractive. The
reaction is green as only water is produced as the side product.1
The selective mono-allylated diketones are used as a precursor
for synthesising natural and unnatural bioactive molecules.2
The hydroxyl group is a weak leaving group. Usually, the
alcohols are converted into acetate, carbonate, or halide for
smooth allylation and alkylation reactions.3 In addition to the
Pd-catalysed Tsuji–Trost reaction,1a,1b which proceeds through
palladium p-allyl intermediate, complexes of palladium,4 plat-
inum,5 ruthenium,6 indium,1c molybdenum,7 gold,8 and
rhodium9 have been used as catalysts for this kind of allylation
reaction. The palladium-based catalysts predominantly afford
the linear allylated products, although some diallyl products are
also obtained. When complexes of iridium,3c,10 and rhodium,
are used as catalysts, branched allylation products were found
to be the primary products. Recently, Ohshima et al. reported
selective monoallylation of active methylene compound using
2 mol% [Pt(cod)Cl2] 2 mol% xantphos as the ligand along with
10 mol% each, of pyrrolidine, and acetic acid as co-catalysts.
However, this catalytic system is useful for only allylic alco-
hols.5b Cobalt compounds have been used as catalysts for ally-
lation reaction.11 For example, cobalt carbonyl compounds,
DMG (DMG ¼ dimethylglyoxime) complex was used as a catalyst
for the allylation using allyl alcohol.11b But the conversions were
low, and the catalyst loading was comparatively higher
(5 mol%), and acetic acid was used as the reaction medium.
Ackermann and coworkers have reported cobalt(III) catalysed
allylative C–H and C–F functionalisation.11e It may be pointed
out that most of the reported methods either require additives
or are not regioselective. Some of the methods afford a mixture
of diallylated and monoallylated products (Scheme 1). There-
fore, the development of an additive-free strategy for regiose-
lective allylic substitution is highly desirable.
I2
Recently a high valent cobalt complex, Cp*Co(CO)2 has
been used as a precatalyst for dehydrogenation of alcohols.12
High valent cationic cobalt complex has been shown to catalyse
directed C–H bond activation.13
Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur
721302, India. E-mail: mxb@iitkgp.ac.in
† Electronic supplementary information (ESI) available: 1H, 13C NMR spectra and
Scheme 1 Reported reactions catalysed various metal compounds.
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Table 1 Optimization table for diketone addition to cinnamyl alcohola
I
Temperature
(ꢀC)
Scheme 2 Reactions reported here.
Entry
(mol%)
Time (h)
Solvent
Yieldb (%)
1
2
3
4
5
6
7
8
—
1
1
1
1
1
1
1
1.5
2
90/110
90
24
12
12
12
12
8
8
8
8
8
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
DCE
CH3CN
Toluene
Toluene
Toluene
Toluene
—
49
58
Lewis acids or Brønsted acids,14 including InCl3,1c
Bi(OTf)3,15a FeCl3,15b carbon-supported iron – ionic liquid,15c and
PTSA,16 have been used for the benzylation of active methylene
compounds by benzylic alcohols. To the best of our knowledge,
there is only one report on the benzylation and allylation of b-
keto carbonyl compounds using the same catalyst. It has been
reported that Bi(OTf)3 can catalyse both allylation and alkyl-
ation of active methylene compounds.14 The yields of benzy-
lated products were found to be excellent. Allylation reactions
were found to be useful only for cinnamyl alcohol, and the
products were obtained in moderate yield. The selective allyla-
tion and alkylation reaction with cobalt complexes as catalysts
are preferable because its compounds are comparatively inex-
pensive than those of rhodium, iridium, and palladium.
Recently we have shown that [Cp*Co(CH3CN)3][SbF6]2 (I) is
an efficient catalyst for the Nakamura reaction.17 In continua-
tion of our studies on the catalytic activity of [Cp*Co(CH3CN)3]
[SbF6]2 (I), herein, we report the monoallylation and benzylation
of diketones and b-keto esters using allylic alcohols and
secondary benzyl alcohols, respectively. Eleven new pyrazoles
and one pyrazolone have been synthesized from the allylated
and alkylated products (Scheme 2).
110
110
110
110
110
100
110
110
110
110
19c
13d
72e
65e
e
—
9
76e
81e
80f
83f
10
11
12
1.5
1.7
8
8
a
1b (0.2 mmol), 2a (0.2 mmol), I (1 mol%, 0.0015 g), toluene (2 mL).
Isolated yield. In the presence of K2CO3 (1 equivalent). In the
b
c
d
e
presence of Na2CO3 (1 equivalent). 1b (0.2 mmol), 2a (0.3 mmol).
f
1b (0.2 mmol), 2a (0.34 mmol).
presence of 1 mol% I in toluene, using 1b and 2a in the 1 : 1.5
ratio. The yield was found to be 72% (entry 6, Table 1). The
reaction carried out in dichloroethane (DCE) afforded the
product in moderate yields (entry 7, Table 1). We could not detect
any product formation when CH3CN was used as a solvent (entry
8, Table 1). When 1.5 mol% of I was used, maintaining the 1b : 2a
ratio at 1 : 1.5, the product was obtained in 76% yield in eight
hours (entry 9, Table 1). Similarly, when the catalyst loading was
2 mol%, the product was isolated in 81% yield in eight hours
(entry 10, Table 1). When the reactants, 1b and 2a were used in
1 : 1.7 ratio, in the presence of 1.5 mol% of I, the product was
isolated in 80% yield (entry 11, Table 1). On increasing the
catalyst loading to 1.7 mol%, the product was isolated in 83%
yield (entry 12, Table 1).
Results and discussion
The optimization of the allylation reaction was done using 1-
phenyl-butane-1,3-dione (1b) and cinnamyl alcohol (2a) as model
substrates. In the preliminary stage, we did a blank reaction with
1-benzoyl acetone (1b) and cinnamyl alcohol (2a) at different
temperatures (room temperature to 110 ꢀC) in toluene for 24
hours. However, we did not get any desired product (entry 1,
Table 1). When we added the catalyst (1 mol%) and heated the
reaction solution to 90 ꢀC for 12 hours, the product was isolated
in 49% yield (entry 2, Table 1). Next, the reaction solution was
heated at 110 ꢀC for 12 hours, and the desired product, (3b), was
isolated in 58% yield (entry 3, Table 1). It was anticipated that the
addition of base to the reaction mixture would enhance the
reaction rate as a base can deprotonate the active methylene
–CH2 protons and enolisation of the b-dicarbonyl compounds
may happen faster. Thus, we carried out the reaction in the
presence of inorganic bases, K2CO3, and Na2CO3, but the yield
decreased unexpectedly (entries 4 and 5, Table 1). When we
added the base, the yield of the reaction drastically reduced. The
reduction in the yield could be due to the catalyst degradation
upon addition of the base. When the base was added, the reac-
tion mixture's colour changed, and within a few minutes, the
solution became hazy. Then we carried out the reaction in the
Aer optimizing the time, temperature, solvent, and catalyst
loading, we studied the effect of the leaving group. When cin-
namyl chloride was used, the product was isolated in a 91%
Table 2 Effect of leaving group on conversion to the producta
Entry
Leaving group (X)
Time (h)
Yield (%)
1
2
3
Cl
OAc
6
8
6
91
59
79
i
OCO2–CH2 Pr
a
1b (0.3 mmol), 2a (0.51 mmol), I (0.0040 g, 1.7 mol%), toluene (2 mL),
110–115 ꢀC.
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yield in six hours (entry 1, Table 2). The yield decreased dras- butane-1,3-dione (1b), 1,3-diphenyl propane-1,3-dione (1c),
tically to 59% in eight hours, when cinnamyl acetate was used as and 3-methyl pentane-2,4-dione (1d) on reaction with cinnamyl
the reactant (entry 2, Table 2). However, when carbonic acid alcohol (2a) afforded the monoallylated products 3a, 3b, 3c, and
isobutyl easter-3-phenyl-ally ester was used, the product was 3d in 72%, 83%, 89% in eight hours, and 61% in nine hours,
isolated in 79% in six hours (entry 3, Table 2). Although the respectively (Table 3). 3-Oxo-butyric acid-methyl ester (1e) and 3-
conversion to the product was higher in the case of chloride oxo-butyric acid-ethyl ester (1f) on reaction with cinnamyl
leaving group, we preferred to use allylic alcohols as the method alcohol (2a) afford the products, 3e and 3f in 33% and 45%
is green.
yield, respectively in nine hours (Table 3). The products, 3(1,3-
Aer the optimization of the reaction condition, we pro- diphenyl-ally)-pentane-2,4-dione (3g) and 2-(1,3-diphenyl-allyl)-
ceeded to investigate the scope of the reaction. Reactions were 1-phenyl-butane-1,3-dione (3h) were isolated in 79% and 87%
carried out between various diketones and b-keto esters with yield, respectively in seven hours form the reaction of (E)-1,3-
different allylic alcohols. Pentane-2,4-dione (1a), 1-phenyl- diphenyl-prop-2-en-1-ol (2b) with 1a and 1c (Table 3). Similarly,
Table 3 Regioselective monallylation reaction between different b-keto compounds with cinnamyl alcohola,b
a
1 (0.2 mmol), 2 (0.34 mmol), I (1.7 mol%). b All yields are isolated yield.
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(E)-but-2-en-1-ol (2c) on reaction with 1b and 1,4-diphenyl-2,3- OMe (4c), p-Cl (4d), and p-F (4e)} afforded the alkylated products
butanedione (1c) afforded the product 3i and 3j in 37% and 5a to 5e in excellent yields within four to ve hours. However, in
42% yield, respectively, in twelve hours (Table 3). 3-Methyl-2- the case of 1-(4-triouromethylphenyl)-ethan-1-ol (4f), the
buten-1-ol (2d), when reacted with 1b, and 1c, the products, conversion to the product 5f was found to be negligible, even
3k and 3l were isolated in 53%, and 65% yield, respectively in 12 aer ten hours of the reaction time. Interestingly, when 1a was
hours. 3,6-Dimethyl-2,6-octadiene-1-ol (2e) on reaction with 1a, reacted with diphenylmethanol (4g) the product, 5g was isolated
1b, and 1c afforded the corresponding products, 3m, 3n, and in almost quantitative yield (98%) in four hours. Similarly, 1b
3o, in twelve hours, in 27%, 45%, and 38%, respectively.
on reaction with 4a, 4b, and 4g afforded the products 5h, 5i, and
Thus, it was observed that in the cases of aliphatic allylic 5j, respectively, in excellent yields in 3.5 to 5 hours (Table 4).
alcohols, comparatively lower yields of the products were ob- When 1c was reacted with 4a and 4g, the products, 5k, and 5l
tained (Table 3). 2-Acetylcyclopentan-1-one (1g) and 2- were obtained in quantitative yields in 3.5 and 2.5 hours,
acetylcyclohexan-1-one (1h) on reaction with 2a, afforded the respectively. 3-Methylpentane-2,4-dione (1d) on reaction with 4g
products, 3p, and 3q in 65 and 71% yield, respectively.
afforded the product, 5m in 53% yield in nine hours. Cyclic
We then proceeded to study the alkylation of diketones using diketones, 1g, and 1h on reaction with 4g afforded the product,
secondary aromatic alcohols. There is only one report on both 5n, and 5o in 91% and 78%, respectively, in 5 hours.
allylation and alkylation of b-keto carbonyl compounds, cata-
The b-ketoester, 1e, was found to react with 4a and 4g to
lysed by the same catalyst.15 Thus, 1a on reaction with 1-phenyl- afford the corresponding products in 62% and 97% in 8 and 5
ethan-1-ol (4a) and substituted 1-phenyl-ethan-ols {p-Me (4b), p- hours, respectively. The b-Ketoester, 1f on reaction with 4a and
Table 4 Reaction of b-keto compounds with secondary alcoholsa,b
a
Nucleophile (1) (0.2 mmol), alcohol (4) (0.26 mmol), I (1.5 mg, 1 mol%), 110 ꢀC. b All yields are isolated yields. c 1 : 1 diastereomeric mixture.
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Scheme 5 Control experiments of alkylation.
Similarly, when diphenylmethanol (4g) was mixed with I and
stirred at room temperature. The corresponding ether was iso-
lated in a 37% yield in three hours. When the reaction was
Scheme 3 Gram scale reactions.
ꢀ
conducted at 110 C, the ether was isolated in a 71% yield in
4g afforded the products 5r, and 5s in 76% and 94% yield,
respectively, in 7 hours (Table 4). It may be noted that no
product could be isolated from the reaction of 1c with 2-prop-
anol and 1-(thiophen-2-yl)ethan-1-ol. From the data, it is clear
that the highest rate of conversion was found for the reactions
of diphenylmethanol (4g) with b-keto compounds. Similarly, the
highest conversion rate was observed in the reactions of 1-
phenyl-butane-1,3-dione (1b).
three hours (Scheme 4). The ether was isolated and was reacted
with 1c. In the absence of I, no product formation was detected.
Therefore, to investigate the reaction mechanism, we per-
formed two control experiments (Scheme 4). First, cinnamyl
alcohol was heated to different temperatures in the absence and
in the presence (1 mol%) of the catalyst. In the absence of the
catalyst, we could detect the formation of a trace amount of
ꢀ
ether (Scheme 4). In the presence of the catalyst, at 65 C, the
ether was isolated in a 67% yield. At 110 ꢀC, the observed yield
of the ether decreased to 30%. We then carried out a reaction
between the isolated ether and 1b. In the absence of I, no
product could be isolated. However, in the presence of the
catalyst, the product was isolated in 91% yield in 5 hours
(Scheme 4).
There are two possible pathways for allylation of 1,3-diketone
by allylic alcohol. One path is through activation of alcohol by
the metal centre via the formation of ether, followed by addi-
tion. The second pathway is h3-allyl metal complex formation.1c
We have carried out reactions between 1,3-diphenyl
propane-1,3-dione (1c) with cinnamyl alcohol (2a) and diphe-
nylmethanol (4g) on a gram scale to check the scalability of the
reaction. The allylation product 3c has been obtained in 68%
yield. The alkylation product 5l has been isolated in 93% yield
(Scheme 3).
However, in the presence I, the product was isolated in 95%
yield in 3 hours (Scheme 5).
Yasuda et al. reported InCl3 mediated alkylation of dike-
tones. They suggested that the reaction of alcohols proceed
through indium mediated ether formation and subsequent
alkylation.1c They have also suggested a direct activation of
alcohol for the alkylation. It may be mentioned that Fe(OTf)3
has been shown to catalyse dehydration of alcohols to ether.18
In a recent publication for this laboratory, we have shown
that when acetylacetone is added to the solution of
[Cp*Co(CH3CN)3][SbF6]2 (I), it forms [Cp*Co(acac)]+ (m/z ¼
293.1) in LCMS of the reaction mixture.17
1
The mechanism was studied by H NMR spectroscopy. The
solution of cinnamyl alcohol and I (1 mol%) was heated at
1
ꢀ
100 C for 18 hours, and the H NMR spectrum (Fig. S3, ESI†)
was recorded. The NMR spectrum shows a signal at 4.21 ppm
(doublet, J ¼ 6 Hz), which can be assigned to the –CH2 protons
of the ether (Scheme 3).
1
Similarly, the H NMR spectrum (Fig. S4, ESI†) of the solu-
tion of diphenylmethanol and I (1 mol%) was recorded aer
heating the reaction solution at 110 ꢀC. The NMR spectrum
shows a singlet at 5.43 ppm along with the signals of aromatic
protons. This signal is due to the –CH proton of the ether.
Scheme 6 Plausible mechanisms of allylation and alkylation of the
Scheme 4 Control experiments of allylation.
diketones.
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was obtained. The reaction of 3b and 3c with hydrazine hydrate
under the same reaction condition afforded the 1 : 1 mixture of
the allylated and alkylated pyrazoles 6k and 6l, respectively
(Scheme 7).
We have carried one-pot sequential reactions for the
synthesis of pyrazoles. For example, 1,3-diphenyl propane-1,3-
dione (1c) was rst reacted with cinnamyl alcohol (2a) and 4g
under optimized condition. Upon completion of the reaction
a few millilitre EtOH hydrazine hydrate was added, and the
corresponding product was isolated (Scheme 8).
Scheme 7 Synthesis of substituted pyrazoles and 4-benzhydryl-5-
methyl-1,2-dihydro-pyrazole-3-one.
Conclusion
In summary, allylation and alkylation of active methylene
compounds using the corresponding alcohol are reported. The
reaction is regioselective. Also, the method affords only mono-
allylated and monoalkylated products, unlike most of the re-
ported methods.
The reactions have been carried out under aerobic condi-
tions in toluene. These allylated and alkylated diketones and
a b-keto ester have been used for the synthesis of eleven new
pyrazoles and a new pyrazolone.
Based on the report from this laboratory17 and other reports,
it is proposed that rst, the diketone forms the intermediate A.
Which reacts with allyl alcohol to produce the intermediate B.
The intermediate B on reaction with another molecule of allylic
alcohol forms the ether, which is coordinated to the cobalt
centre (C). In the next step, the nucleophilic addition to the
enolized diketones occurs, followed by the release of the
product by proton transfer from another molecule of diketone
to produce the intermediate A (Scheme 6). We believe that the
alkylation also takes place via the same mechanism.
Experimental section
Aer the synthesis of substituted diketones, we thought of
using these for the synthesis of pyrazoles. Pyrazoles and pyr-
azolones are an important class of compounds having potential
medicinal use.19 Thus, we carried out the reaction of the
substituted diketones, 5c, 5g, and 5k with hydrazine in ethanol,
in the presence of acetic acid. The resulting pyrazoles were
isolated in excellent yields (Scheme 7). Similarly, ethyl-2-
benzhydryl-3-oxobutanoate (5s) on reaction with hydrazine
under the same condition, afforded 4-benzhydryl-5-methyl-1,2-
dihydro-pyrazole-3-one (6c) in 96% yield. Corresponding pyr-
azoles, 6e, and 6f were isolated from the reaction of phenyl-
hydrazine with the diketones, 5j & 5l (Scheme 7). The pyrazoles,
6g, 6h, and 6i, were isolated in excellent yield form the reaction
of 3b, 3c, and 3h with hydrazine hydrate in ethanol at room
temperature (Scheme 7). Interestingly, when the reaction of
diketones, 3g, 3b, and 3c with hydrazine hydrate were carried
out in the presence of one drop of acetic acid in ethanol for 12
hours, a 1 : 1 mixture of 4-(1,3-diphenyl-propyl)-3,5-dimethyl-
pyrazole and 4-(1,3-diphenyl-allyl)-3,5-dimethyl-pyrazole (6j)
General methods and materials
All the reactions are performed in the air without further puri-
cation of commercially available reagents and solvents. The
catalyst [Cp*Co(CH3CN)3][SbF6]2 was synthesized from the
literature procedure.16 The 1H NMR (400 MHz) and 13C NMR
(100 MHz) were recorded in CDCl3. The LCMS data of the
reaction mixture were recorded with a TOF mass spectrometer
in ESI+ mode in MeOH and acetonitrile solvent. The HRMS data
of newly synthesized compounds were recorded with a TOF
mass spectrometer in ESI+ mode in acetonitrile/water mixture.
Flash column chromatography was done in silica gel (60–120
mesh) for purication of product from the crude reaction
mixture.
General procedure for the reaction of allylic alcohols with
diketones and b-keto esters
The catalyst (0.0027 g, 1.7 mol%), toluene (2 mL), the b-keto
compound (0.2 mmol), and allylic alcohol (0.34 mmol, 1.7
equivalent) were taken in a screw-cap reaction tube. The reac-
ꢀ
tion tube was placed in an oil-bath at a temperature of 110 C
and continuously stirred for 8–12 hours. The reaction was
monitored by TLC. The solvent was removed in vacuo, and the
products were puried by silica gel (60–120 mesh) column
chromatography using hexane-ethyl acetate (1–5%) as eluent.
Synthesis of pyrazoles
The alkylated diketones, 5c, 5g, 5k, and 5s (0.2 mmol) were
dissolved in ethanol, and one drop of acetic acid was added to
this. The reaction solution was reuxed for 12 hours. The
solvent was removed in vacuo, and the products were puried by
Scheme 8 One pot synthesis of substituted pyrazoles 6h and 6a.
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silica gel (60–120 mesh) column chromatography using hexane- 7.20 (m, 10H), 6.43 (d, J ¼ 15.6 Hz, 1H), 6.20 (ddd, J ¼ 15.8, 5.6,
ethyl acetate (1–5%) as eluent.
2.2 Hz, 1H), 4.37–4.30 (m, 2H), 2.25 (s, 3H), 1.93 (s, 3H); 13C
The newly synthesized allylated compounds, 3b, 3c, and 3h NMR (100 MHz, DMSO) d 202.9, 202.7, 140.1, 136.5, 131.7,
(0.2 mmol) and hydrazine hydrate (0.4 mmol) were dissolved in 129.2, 129.0, 128.5, 127.9, 127.7, 127.3, 126.4, 74.5, 49.2, 30.1,
ethanol, and the reaction solution was stirred for 9 hours at 29.7.
room temperature. The solvent was removed in vacuo, and the
2-(1,3-Diphenyl-allyl)-1,3-diphenyl-propane-1,3-dione (3h).22
products were puried by silica gel (60–120 mesh) column Pale yellow liquid; yield 0.0724 g, 87%; 1H NMR (500 MHz,
chromatography using hexane-ethyl acetate (1–5%) as eluent. In CDCl3) d 8.04 (d, J ¼ 8.5 Hz, 2H), 7.82 (d, J ¼ 8.5 Hz, 2H), 7.55 (t, J
another set of reactions, the reaction solutions were stirred for ¼ 7.5 Hz, 1H), 7.48–7.43 (m, 3H), 7.36–7.31 (m, 4H), 7.23 (t, J ¼
12 hours in the presence of one drop of acetic acid.
7.7 Hz, 2H), 7.17 (d, J ¼ 8.0 Hz, 2H), 7.14–7.12 (m, 2H), 7.09 (d, J
3-(3-Phenyl-allyl)-pentane-2,4,done (3a).5b,15a Colourless ¼ 8.0 Hz 2H), 6.36–6.28 (m, 2H), 5.97 (d, J ¼ 10.5 Hz, 1H), 4.81
liquid; yield 0.0311 g, 72%; 1H NMR (400 MHz, CDCl3) d 7.34 (t, J (dd, J ¼ 10.5, 7.0 Hz, 1H); 13C NMR (100 MHz, CDCl3) d 194.4,
¼ 6.2 Hz, 2.7H), 7.31–7.27 (m, 5H), 7.24–7.20 (m, 2H), 6.45 (d, J 193.8, 140.9, 137.3, 136.9, 133.4, 133.2, 131.9, 129.9, 128.9,
¼ 15.6 Hz, 1H), 6.35 (d, J ¼ 16.0 Hz, 0.8H), 6.22 (dt, J ¼ 16.0, 128.8, 128.7, 128.6, 128.5, 128.4, 128.3, 127.3, 126.8, 126.2, 62.6,
5.2 Hz, 0.8H), 6.07 (dt, J ¼ 15.6, 7.2 Hz, 1H), 3.80 (t, J ¼ 7.4 Hz, 50.0.
1H), 3.16 (dd, J ¼ 5.2, 1.2 Hz, 1.7H), 2.75 (t, J ¼ 7.0 Hz, 2H), 2.21
2-But-2-enyl-1-phenyl-butane-1,3-dione (3i). Liquid; yield
(s, 6H), 2.16 (s, 5H); 13C NMR (100 MHz, CDCl3) d 203.6, 191.6, 0.0160 g, 37%; 1H NMR (500 MHz, CDCl3) d 7.98 (d, J ¼ 8.0 Hz,
137.1, 136.8, 132.8, 130.1, 128.6, 128.5, 127.6, 127.5, 127.3, 2H), 7.59 (t, J ¼ 7.5 Hz, 1H), 7.48 (t, J ¼ 7.7 Hz, 2H), 5.56–5.49 (m,
126.2, 126.1, 125.4, 107.4, 68.4, 31.6, 30.5, 29.4, 23.1.
1H), 5.39–5.33 (m, 1H), 4.48 (t, J ¼ 7.0 Hz, 1H), 2.68–2.65 (m,
2-Phenyl-2-(phenyl-allyl)-butane-1,3-dione (3b).5b,15a Colour- 2H), 2.14 (s, 3H), 1.60 (d, J ¼ 6.5 Hz, 3H); 13C NMR (125 MHz,
less liquid; yield 0.0463 g, 83%; 1H NMR (400 MHz, CDCl3) CDCl3) d 203.9, 196.0, 136.5, 133.6, 128.8, 128.7, 128.2, 126.8,
d 7.98 (d, J ¼ 7.6 Hz, 2H), 7.58 (t, J ¼ 7.2 Hz, 1H), 7.47 (t, J ¼ 63.5, 32.1, 28.0, 17.8. HRMS (ESI-TOF) m/z: [C14H16O2 + H]+
7.6 Hz, 2H), 7.27–7.23 (m, 4H), 7.19–7.17 (m, 1H), 6.44 (d, J ¼ calcd for C14H17O2 217.1224; found 217.1229.
16.0 Hz, 1H), 6.15–6.07 (m, 1H), 4.59 (t, J ¼ 7.0 Hz, 1H), 2.94–
2-But-2-enyl-1,3-diphenyl-propane-1,3-dione
(3j).
Light
2.82 (m, 2H), 2.16 (s, 3H); 13C NMR (125 MHz, CDCl3) d 203.5, yellow liquid; yield 0.0235 g, 42%; H NMR (600 MHz, CDCl3)
1
195.8, 136.9, 136.4, 133.8, 132.7, 128.9, 128.8, 128.5, 127.4, d 7.95 (d, J ¼ 8.4 Hz, 4H), 7.56 (t, J ¼ 7.2 Hz, 2H), 7.45 (t, J ¼
126.2, 125.9, 63.2, 32.4, 28.3.
7.2 Hz, 4H), 5.52–5.48 (m, 2H), 5.25–5.23 (m, 1H), 2.80 (t, J ¼
1,3-Diphenyl-2-(3-phenyl-ally)-propane-1,3-dione
(3c).5b,15a 6.3 Hz, 2H), 1.59 (d, J ¼ 5.4 Hz, 3H); 13C NMR (150 MHz, CDCl3)
Off white liquid; yield 0.0607 g, 89%; 1H NMR (400 MHz, CDCl3) d 195.8, 136.1, 133.5, 128.9, 128.7, 128.1, 127.7, 57.5, 32.6, 17.9.
d 7.99 (d, J ¼ 7.6 Hz, 4H), 7.57 (t, J ¼ 7.2 Hz, 2H), 7.46 (t, J ¼ Calc. [M + H]+ ¼ 279.1380, found [M + H]+ ¼ 279.1386.
7.8 Hz, 4H), 7.30–7.19 (m, 5H), 6.47 (d, J ¼ 15.6 Hz, 1H), 6.30–
2-(3-Methyl-but-2-enyl)-1-phenylbutane-1,3-dione
(3k).23
6.22 (m, 1H), 5.37 (t, J ¼ 6.6 Hz, 1H), 3.04 (t, J ¼ 6.8 Hz, 2H); 13
C
Light yellow liquid; yield 0.0244 g, 53%; 1H NMR (400 MHz,
NMR (100 MHz, CDCl3) d 195.6, 137.0, 135.9, 133.6, 132.5, 128.9, CDCl3) d 7.97 (d, J ¼ 7.2 Hz, 2H), 7.58 (t, J ¼ 7.4 Hz, 1H), 7.47 (t, J
128.6, 128.5, 127.4, 126.8, 126.2, 57.2, 33.0.
¼ 7.8 Hz, 2H), 5.03 (td, J ¼ 6.6, 1.2 Hz, 1H), 4.44 (t, J ¼ 7.4 Hz,
3-Methyl-3-(3-phenyl-allyl)-pentane-2,4-dione (3d).20 Colour- 1H), 2.68 (t, J ¼ 7.2 Hz, 2H), 2.14 (s, 3H), 1.63 (s, 3H), 1.61 (s,
less liquid; yield 0.0281 g, 61%; 1H NMR (400 MHz, CDCl3) 3H); 13C NMR (100 MHz, CDCl3) d 204.2, 196.3, 136.5, 134.7,
d 7.32–7.29 (m, 4H), 7.24–7.20 (m, 1H), 6.44 (d, J ¼ 15.6 Hz, 1H), 133.6, 128.8, 128.7, 120.0, 63.4, 29.7 (grease), 28.0, 27.8, 25.7,
6.01–5.93 (m, 1H), 2.75 (d, J ¼ 7.2 Hz, 2H), 2.15 (s, 6H), 1.38 (s, 17.8. HRMS (ESI-TOF) m/z: [C15H18O2 + H]+ calcd for C15H19O2
3H); 13C NMR (100 MHz, CDCl3) d 206.7, 136.9, 134.1, 128.5, 231.1380; found 231.1383.
127.5, 126.2, 123.9, 66.7, 38.1, 29.7, 26.7, 18.3.
2-(3-Methylbut-2-enyl)-1,3-diphenylpropane-1,3-dione (3l).
2-Acetyl-5-phenyl-pent-4-enoic acid methyl ester (3e).21 Col- Colourless liquid; yield 0.0381 g, 65%; 1H NMR (400 MHz,
1
ourless liquid; yield 0.0155 g, 33%; H NMR (400 MHz, CDCl3) CDCl3) d 7.95 (d, J ¼ 7.2 Hz, 4H), 7.56 (t, J ¼ 7.4 Hz, 2H), 7.44 (t, J
d 7.33–7.32 (m, 1H), 7.31–7.30 (m, 2H), 7.29–7.28 (m, 1H), 7.23– ¼ 7.6 Hz, 4H), 5.20 (t, J ¼ 6.8 Hz, 1H), 5.16–5.14 (m, 1H), 2.81 (t, J
7.21 (m, 1H), 6.46 (d, J ¼ 16.0 Hz, 1H), 6.11 (dt, J ¼ 15.7, 7.3 Hz, ¼ 7.0 Hz, 2H), 1.61 (s, 3H), 1.56 (s, 3H); 13C NMR (125 MHz,
1H), 3.75 (s, 3H), 3.61 (t, J ¼ 7.4 Hz, 1H), 2.75 (t, J ¼ 7.2 Hz, 2H), CDCl3) d 196.0, 136.2, 134.4, 133.4, 128.8, 128.6, 120.9, 57.5,
2.26 (s, 3H); 13C NMR (125 MHz, CDCl3) d 202.3, 169.7, 137.0, 28.3, 25.6, 17.8. HRMS (ESI-TOF) m/z: [C20H20O2 +H]+ Calcd for
132.8, 128.5, 127.4, 126.2, 125.6, 59.4, 52.5, 31.6, 29.7 (grease),
29.3.
C
20H21O2 293.1537; found 293.1543.
2-(3,7-Dimethyl-octa-2,6-dienyl)-pentane-2,4-dione
(3m).
2-Acetyl-5-phenyl-pent-4-enoic acid ethyl ester (3f).5b Light Light yellow liquid; yield 0.0128 g, 27%; 1H NMR (400 MHz,
1
yellow liquid; yield 0.0223 g, 45%; H NMR (400 MHz, CDCl3) CDCl3) d 5.09–4.93 (m, 3H; geraniol vinyl proton keto substrate
d 7.32–7.27 (m, 4H), 7.23–7.19 (m, 1H), 6.46 (d, J ¼ 15.6 Hz, 1H), 2H and enol form 1H), 3.64 (t, J ¼ 7.4 Hz, 1H; keto compound
6.15–6.08 (m, 1H), 4.21 (q, J ¼ 7.2 Hz, 2H), 3.59 (t, J ¼ 7.4 Hz, methylene proton), 2.90 (d, J ¼ 6.0 Hz, 1H; enol form geraniol
1H), 2.75 (t, J ¼ 7.2 Hz, 2H), 2.26 (s, 3H), 1.26 (t, J ¼ 7.2 Hz, 3H); CH2), 2.54 (t, J ¼ 7.2 Hz, 2H; ketone form geraniol CH2), 2.17 (s,
13C NMR (125 MHz, CDCl3) d 202.4, 169.2, 137.0, 132.7, 128.5, 6H, ketone form acetylacetone Me), 2.10 (s, 3H; enol form ace-
127.4, 126.2, 125.7, 61.5, 59.6, 31.5, 29.7 (grease), 29.2, 14.1.
tylacetone Me), 2.06–2.02 (m, 4H; ketone form geraniol CH2),
3-(1,3-Diphenyl-allyl)-pentane-2,4-dione (3g).1c Light yellow 1.99–1.95 (m, 2H; enol form geraniol CH2), 1.66 (s, 6H; ketone
1
liquid; yield 0.0462 g, 79%; H NMR (400 MHz, CDCl3) d 7.34– form geraniol Me), 1.62 (s, 3H; enol form geraniol Me), 1.59 (s,
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5H; ketone and enol form geraniol Me); 13C NMR (100 MHz,
CDCl3) d 204.3, 191.0, 138.5, 135.7, 131.7, 131.6, 124.0, 123.9,
123.0, 119.6, 109.8, 68.6, 39.6, 39.5, 29.3, 27.1, 26.5, 26.4, 26.2,
25.7, 25.6, 23.0, 17.6, 16.1. HRMS (ESI-TOF) m/z: [C15H24O2 + H]+
Calcd for C15H25O2 237.1850; found 237.1853.
2-(3,7-Dimethylocta-2,6-dienyl)-1-phenyl-butane-1,3-dione
(3n).24 Light yellow liquid; yield 0.0268 g, 45%; 1H NMR (400
MHz, CDCl3) d 7.97 (d, J ¼ 7.6 Hz, 2H), 7.58 (t, J ¼ 7.4 Hz, 1H),
7.47 (t, J ¼ 7.8 Hz, 2H), 5.05 (t, J ¼ 7.0 Hz, 1H), 5.00 (t, J ¼ 6.6 Hz,
1H), 4.46 (t, J ¼ 7.2 Hz, 1H), 2.70 (t, J ¼ 7.2 Hz, 2H), 2.14 (s, 3H),
1.97–1.93 (m, 4H), 1.63 (s, 3H), 1.61 (s, 3H), 1.55 (s, 3H); 13C
NMR (100 MHz, CDCl3) d 204.1, 196.4, 138.3, 136.6, 133.6, 131.5,
128.8, 128.7, 123.9, 119.9, 63.3, 39.6, 29.7 (grease), 28.1, 27.8,
26.4, 25.6, 17.6, 16.1.
3-[1-(4-Chlorophenyl-ethyl)]-pentane-2,4-dione (5d).22 Col-
ourless liquid; yield 0.0457 g, 96%; H NMR (400 MHz, CDCl3)
1
d 7.25 (d, J ¼ 8.4 Hz, 2H), 7.11 (d, J ¼ 8.4 Hz, 2H), 3.98 (d, J ¼
11.6 Hz, 1H), 3.57 (dq, J ¼ 13.7, 6.8 Hz, 1H), 2.24 (s, 3H), 1.85 (s,
3H), 1.17 (d, J ¼ 6.8 Hz, 3H); 13C NMR (100 MHz, CDCl3) d 203.1,
203.0, 141.6, 132.6, 128.9, 128.6, 76.6, 39.6, 29.8, 29.6, 20.7.
3-[1-(4-Fluorophenyl-ethyl)]-pentane-2,4-dione (5e).22 Col-
1
ourless liquid; yield 0.0436 g, 98%; H NMR (400 MHz, CDCl3)
d 7.13 (dd, J ¼ 8.4, 5.6 Hz, 2H), 6.95 (t, J ¼ 8.6 Hz, 2H), 3.97 (d, J
¼ 11.2 Hz, 1H), 3.57 (dq, J ¼ 13.6, 6.8 Hz, 1H), 2.23 (s, 3H), 1.82
(s, 3H), 1.16 (d, J ¼ 6.8 Hz, 3H); 13C NMR (100 MHz, CDCl3)
d 203.2, 203.1, 161.6 (d, J ¼ 244 Hz), 138.7 (d, J ¼ 3 Hz), 128.8 (d,
J ¼ 8 Hz), 115.6 (d, J ¼ 22 Hz), 76.8, 39.6, 29.8, 29.6, 20.8.
3-Benzhydry-lpentane-2,4-dione (5g).15c White solid; yield
0.0522 g, 98%; 1H NMR (400 MHz, CDCl3) d 7.26 (d, J ¼ 4.8 Hz,
8H), 7.20–7.14 (m, 2H), 4.82 (d, J ¼ 12.4 Hz, 1H), 4.75 (d, J ¼
12.4 Hz, 1H), 2.00 (s, 6H); 13C NMR (100 MHz, CDCl3) d 203.0,
141.3, 128.9, 127.7, 127.1, 74.5, 51.2, 29.7.
1-Phenyl-2-(1-pheny-ethyl)-butane-1,3-dione (diastereomer
with low polarity, 5ha).13a White solid; total yield of 5h 0.0513 g,
96%; 1H NMR (400 MHz, CDCl3) d 7.78 (d, J ¼ 7.2 Hz, 2H), 7.48
(t, J ¼ 9.4 Hz, 1H), 7.35 (t, J ¼ 7.6 Hz, 2H), 7.22–7.14 (m, 4H),
7.10–7.05 (m, 1H), 4.82 (d, J ¼ 11.2 Hz, 1H), 3.85 (dq, J ¼ 13.6,
6.8 Hz, 1H), 2.25 (s, 3H), 1.31 (d, J ¼ 7.2 Hz, 3H); 13C NMR (100
MHz, CDCl3) d 203.7, 195.3, 143.4, 137.0, 133.4, 128.6, 128.5,
127.4, 126.6, 71.5, 40.3, 27.5, 20.3.
2-(3,7-Dimethyl-octa-2,6-dienyl)-1,3-diphenyl-propane-1,3-
1
dione (3o).24 Light yellow liquid; yield 0.0274 g, 38%; H NMR
(400 MHz, CDCl3) d 7.95 (d, J ¼ 7.2 Hz, 4H), 7.55 (t, J ¼ 7.4 Hz,
2H), 7.44 (t, J ¼ 7.6 Hz, 4H), 5.20 (dt, J ¼ 15.4, 7.0 Hz, 2H), 5.00 (t,
J ¼ 6.0 Hz, 1H), 2.83 (t, J ¼ 7.0 Hz, 2H), 1.95–1.87 (m, 4H), 1.61
(s, 3H), 1.58 (s, 3H), 1.54 (s, 3H); 13C NMR (125 MHz, CDCl3)
d 195.9, 138.0, 136.3, 133.4, 128.8, 128.6, 127.5, 124.0, 120.7,
57.3, 39.6, 28.3, 26.5, 25.6, 17.6, 16.1.
2-Acetyl-2-(3-phenyl-allyl)-cyclopentanone (3p).24 Colourless
1
liquid; yield 0.0315 g, 65%; H NMR (400 MHz, CDCl3) d 7.32–
7.27 (m, 4H), 7.24–7.19 (m, 1H), 6.44 (d, J ¼ 15.6 Hz, 1H), 5.99–
5.90 (m, 1H), 2.85–2.79 (m, 1H), 2.68–2.57 (m, 2H), 2.34–2.27
(m, 2H), 2.25 (s, 3H), 1.91–1.83 (m, 3H); 13C NMR (100 MHz,
CDCl3) d 215.6, 203.9, 136.7, 134.1, 128.5, 127.6, 126.2, 123.8,
68.7, 38.6, 38.3, 30.3, 26.2, 19.3.
1-Phenyl-2-(1-phenyl-ethyl)butane-1,3-dione (diastereomer
1
with high polarity, 5hb).13a,22 White solid; H NMR (400 MHz,
CDCl3) d 8.09 (d, J ¼ 8.4 Hz, 2H), 7.61 (t, J ¼ 7.2 Hz, 1H), 7.50 (t, J
¼ 7.2 Hz, 2H), 7.34–7.18 (m, 5H), 4.91 (d, J ¼ 11.2 Hz, 1H), 3.88
(dq, J ¼ 13.6, 6.8 Hz, 1H), 1.89 (s, 3H), 1.22 (d, J ¼ 6.8 Hz, 3H);
13C NMR (100 MHz, CDCl3) d 203.2, 195.2, 143.2, 137.2, 133.8,
128.9, 128.8, 127.5, 127.0, 70.9, 40.9, 27.9, 21.6.
1-Phenyl-2-[1-(p-tolyl-ethyl)]-butane-1,3-dione (diastereomer
with low polarity, 5ia).25a White solid; total yield of 5i 0.0544 g,
97%; 1H NMR (400 MHz, CDCl3) d 8.09 (d, J ¼ 7.6 Hz, 2H), 7.61
(t, J ¼ 7.0 Hz, 1H), 7.50 (t, J ¼ 7.6 Hz, 2H), 7.17 (d, J ¼ 8.0 Hz,
2H), 7.12 (d, J ¼ 8.0 Hz, 2H), 4.89 (d, J ¼ 11.2 Hz, 1H), 3.84 (dq, J
¼ 13.6, 6.8 Hz, 1H), 2.31 (s, 3H), 1.91 (s, 3H), 1.19 (d, J ¼ 6.8 Hz,
3H); 13C NMR (100 MHz, CDCl3) d 203.4, 195.3, 140.1, 137.3,
136.6, 133.8, 129.5, 128.9, 128.8, 127.3, 71.0, 40.6, 27.8, 21.7,
21.0.
2-Acetyl-2-(3-phenyl-allyl)-cyclohexanone (3q).24 Pale yellow
1
liquid; yield 0.0364 g, 71%; H NMR (400 MHz, CDCl3) d 7.32–
7.27 (m, 4H), 7.22–7.18 (m, 1H), 6.39 (d, J ¼ 15.6 Hz, 1H), 6.06–
5.98 (m, 1H), 2.75–2.69 (m, 1H), 2.63–2.57 (m, 1H), 2.53–2.47
(m, 2H), 2.34–2.26 (m, 1H), 2.13 (s, 3H), 2.02–1.97 (m, 1H), 1.78–
1.65 (m, 3H), 1.58–1.50 (m, 1H); 13C NMR (100 MHz, CDCl3)
d 209.6, 206.1, 137.0, 133.5, 128.5, 127.4, 126.2, 124.4, 67.9, 41.8,
37.9, 34.1, 27.1, 26.4, 22.2.
3-(1-Phenyl-ethyl)-pentane-2,4-dione (5a).15a,22 Light yellow
1
liquid; yield 0.0362 g, 89%; H NMR (400 MHz, CDCl3) d 7.30–
7.26 (m, 2H), 7.22–7.16 (m, 3H), 4.03 (d, J ¼ 11.2 Hz, 1H), 3.58
(dt, J ¼ 13.6, 6.8 Hz, 1H), 2.26 (s, 3H), 1.82 (s, 3H), 1.20 (d, J ¼
6.8 Hz, 3H); 13C NMR (100 MHz, CDCl3) d 203.7, 203.6, 143.2,
129.0, 127.5, 127.2, 76.9, 40.6, 30.0, 29.9, 21.1.
3-(1-(p-Tolyl-ethyl))pentane-2,4-dione (5b).22 Off white solid;
yield 0.0411 g, 94%; 1H NMR (400 MHz, CDCl3) d 7.13–7.05 (m,
4H), 4.01 (d, J ¼ 11.2 Hz, 1H), 3.55 (dq, J ¼ 13.6, 6.8 Hz, 1H), 2.29
(s, 3H), 2.26 (s, 3H), 1.84 (s, 3H), 1.18 (d, J ¼ 6.8 Hz, 3H); 13C
NMR (100 MHz, CDCl3) d 203.7, 203.6, 139.9, 136.5, 129.5, 127.1,
76.82, 40.1, 29.8, 29.7, 20.9.
3-[1-(4-Methoxyphenyl-ethyl]-)pentane-2,4-dione (5c).22 Off
white solid; yield 0.0431 g, 92%; 1H NMR (400 MHz, CDCl3)
d 7.10 (d, J ¼ 8.4 Hz, 2H), 6.82 (d, J ¼ 8.8 Hz, 2H), 3.98 (d, J ¼
11.6 Hz, 1H), 3.76 (s, 3H), 3.54 (dq, J ¼ 13.7, 6.9 Hz, 1H), 2.25 (s,
3H), 1.83 (s, 3H), 1.18 (d, J ¼ 7.2 Hz, 3H); 13C NMR (100 MHz,
CDCl3) d 203.7, 203.6, 158.4, 135.0, 128.2, 114.1, 76.9, 55.2, 39.7,
29.8, 29.7, 20.9.
1-Phenyl-2-(1-(p-tolyl-ethyl))-butane-1,3-dione (diastereomer
with high polarity, 5ib).25a White solid; 1H NMR (400 MHz,
CDCl3) d 7.81 (d, J ¼ 7.6 Hz, 2H), 7.49 (dd, J ¼ 13.2, 7.2 Hz, 1H),
7.36 (t, J ¼ 7.6 Hz, 2H), 7.08 (d, J ¼ 8.0 Hz, 2H), 6.97 (d, J ¼
8.0 Hz, 2H), 4.81 (d, J ¼ 10.8 Hz, 1H), 3.82 (dq, J ¼ 14.2, 6.8 Hz,
1H), 2.23 (s, 3H), 2.20 (s, 3H), 1.28 (d, J ¼ 7.0 Hz, 5H), 1.28 (d, J ¼
7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3) d 203.8, 195.3, 140.5,
137.1, 136.1, 133.4, 129.1, 128.6, 128.5, 127.2, 71.6, 39.9, 27.4,
20.9, 20.4.
2-Benzhydryl-1-phenyl-butane-1,3-dione (5j).25b White solid;
1
yield 0.0647 g, 99%; H NMR (400 MHz, CDCl3) d 7.97 (d, J ¼
8.0 Hz, 2H), 7.53 (t, J ¼ 7.4 Hz, 1H), 7.41 (dd, J ¼ 13.3, 7.3 Hz,
4H), 7.31 (t, J ¼ 7.6 Hz, 2H), 7.28–7.19 (m, 3H), 7.14 (t, J ¼ 7.6 Hz,
2H), 7.05 (t, J ¼ 7.4 Hz, 1H), 5.64 (d, J ¼ 12.0 Hz, 1H), 5.13 (d, J ¼
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12.0 Hz, 1H), 2.05 (s, 3H); 13C NMR (100 MHz, CDCl3) d 203.0, 3.87 (q, J ¼ 7.1 Hz, 2H), 3.79 (d, J ¼ 11.2 Hz, 1H), 3.74 (d, J ¼
194.3, 141.7, 141.2, 136.9, 133.7, 129.0, 128.7, 128.7, 128.7, 11.2 Hz, 1H), 3.58–3.49 (m, 2H), 2.30 (s, 3H), 1.93 (s, 3H), 1.29 (d,
128.1, 127.7, 127.1, 126.7, 68.9, 51.5, 27.9.
J ¼ 6.8 Hz, 6H), 1.23 (t, J ¼ 6.8 Hz, 3H), 0.93 (t, J ¼ 7.2 Hz, 3H);
1,3-Diphenyl-2-(1-phenyl-ethyl)-propane-1,3-dione
(5k).22 13C NMR (100 MHz, CDCl3) d 202.4, 168.6, 168.2, 143.2, 143.1,
White solid; yield 0.0650 g, 99%; 1H NMR (400 MHz, CDCl3) 128.7, 128.4, 127.4, 127.3, 126.9, 126.8, 67.6, 67.0, 61.5, 61.1,
d 8.05 (d, J ¼ 8.0 Hz, 2H), 7.75 (d, J ¼ 8.0 Hz, 2H), 7.56 (t, J ¼ 40.0, 39.8, 29.9, 29.5, 20.5, 20.3, 14.1, 13.7.
7.2 Hz, 1H), 7.47–7.39 (m, 3H), 7.30–7.26 (m, 4H), 7.18 (t, J ¼
2-Benzhydryl-3-oxo-butyric acid ethyl ester (5s).25b White
1
7.6 Hz, 2H), 7.08 (t, J ¼ 7.4 Hz, 1H), 5.63 (d, J ¼ 10.0 Hz, 1H), 4.10 solid; yield 0.0558 g, 94%; H NMR (500 MHz, CDCl3) d 7.23–
(dq, J ¼ 14.0, 7.2 Hz, 1H), 1.36 (d, J ¼ 7.2 Hz, 3H); 13C NMR (100 7.14 (m, 8H), 7.09–7.05 (m, 2H), 4.69 (d, J ¼ 12.5 Hz, 1H), 4.45
MHz, CDCl3) d 195.0, 194.6, 143.8, 137.2, 136.9, 133.6, 133.1, (dd, J ¼ 12.2, 1.2 Hz, 1H), 3.91–3.87 (m, 2H), 2.01 (s, 3H), 0.91 (t,
128.9, 128.8, 128.5, 128.4, 128.4, 127.7, 126.6, 64.8, 41.2, 20.2.
2-Benzhydryl-1,3-diphenyl-propane-1,3-dione (5l).22 White 140.3, 127.8, 127.6, 126.8, 126.7, 125.9, 125.8, 64.2, 60.4, 49.9,
solid; yield 0.0771 g, 99%; 1H NMR (400 MHz, CDCl3) d 7.83 (d, J 28.9, 12.7.
J ¼ 7.2 Hz, 3H); 13C NMR (125 MHz, CDCl3) d 200.6, 166.6, 140.6,
¼ 7.6 Hz, 4H), 7.47 (t, J ¼ 7.4 Hz, 2H), 7.33 (t, J ¼ 7.6 Hz, 4H),
4-Benzhydryl-3,5-dimethyl-1H-pyrazole (6a). Off white solid;
1
7.25 (d, J ¼ 7.2 Hz, 4H), 7.15 (t, J ¼ 7.4 Hz, 4H), 7.05 (t, J ¼ 7.2 Hz, yield 0.0252 g, 96%; H NMR (400 MHz, CDCl3) d 7.28 (t, J ¼
2H), 6.36 (d, J ¼ 11.6 Hz, 1H), 5.33 (d, J ¼ 11.6 Hz, 1H); 13C NMR 7.2 Hz, 4H), 7.22 (d, J ¼ 7.1 Hz, 2H), 7.10 (d, J ¼ 7.4 Hz, 4H), 5.45
(100 MHz, CDCl3) d 194.1, 141.7, 136.9, 133.3, 128.7, 128.6, (s, 1H), 1.89 (s, 6H); 13C NMR (100 MHz, CDCl3) d 143.1, 129.1,
128.5, 128.3, 126.6, 62.3, 52.4.
128.2, 126.2, 117.3, 46.5, 11.6. HRMS (ESI-TOF) m/z: [C18H18N2 +
3-Benzhydryl-3-methyl-pentane-2,4-dione (5m).25c Colourless H]+ calcd for C18H19N2 263.1543; found 263.1547.
1
liquid; yield 0.0297 g, 53%; H NMR (400 MHz, CDCl3) d 7.25–
3,5-Diphenyl-4-(1-phenyl-ethyl)-1H-pyrazole (6b). Off white
1
7.21 (m, 4H), 7.18–7.16 (m, 6H), 5.64 (s, 1H), 1.95 (s, 6H), 1.56 (s, solid; yield 0.0308 g, 95%; H NMR (500 MHz, CDCl3) d 7.37–
3H); 13C NMR (100 MHz, CDCl3) d 206.2, 141.1, 129.7, 128.4, 7.20 (m, 15H), 4.44 (q, J ¼ 7.3 Hz, 1H), 1.46 (d, J ¼ 7.4 Hz, 3H);
126.7, 72.9, 52.3, 26.9, 16.8.
13C NMR (125 MHz, CDCl3) d 146.2, 132.5, 128.8, 128.3, 128.2,
2-Acetyl-2-benzhydryl-cyclopentanone (5n).15c White solid; 128.0, 127.4, 125.7, 117.2, 33.6, 20.0. HRMS (ESI-TOF) m/z:
1
yield 0.0530 g, 91%; H NMR (400 MHz, CDCl3) d 7.28 (t, J ¼ [C23H20N2 + H]+ calcd for C23H21N2 325.1700; found 325.1702.
7.2 Hz, 2H), 7.23–7.14 (m, 6H), 7.01 (d, J ¼ 7.2 Hz, 2H), 5.34 (s,
4-Benzhydryl-5-methyl-1H-pyrazol-3(2H)-one (6c). Off white
1H), 3.18–3.12 (m, 1H), 2.20–2.072 (m, 2H), 2.05 (s, 3H), 1.80– solid; yield 0.0254 g, 96%; 1H NMR (500 MHz, CD3OD) d 7.25 (t, J
1.65 (m, 2H), 1.40–1.33 (m, 1H); 13C NMR (100 MHz, CDCl3) ¼ 7.5 Hz, 4H), 7.17 (t, J ¼ 7.2 Hz, 2H), 7.12 (d, J ¼ 8.0 Hz, 4H),
d 215.2, 202.6, 140.5, 140.4, 129.9, 129.0, 128.8, 128.4, 127.0, 6.62 (s, 0.6H; NH), 5.42 (s, 1H), 1.73 (s, 3H); 13C NMR (125 MHz,
126.9,74.4, 55.2, 38.9, 27.5, 26.0, 19.6.
MeOD) d 163.1, 151.3, 144.8, 142.8, 130.2, 129.2, 127.2, 116.9,
2-Acetyl-2-benzhydryl-cyclohexanone (5o).25d White solid; 46.2, 11.5. HRMS (ESI-TOF) m/z: [C17H16N2O + H]+ calcd for
yield 0.0478 g, 78%; 1H NMR (400 MHz, CDCl3) d 7.29–7.24 (m,
5H), 7.22–7.19 (m, 4H), 7.17–7.12 (m, 1H), 5.46 (s, 1H), 2.78 (dd,
J ¼ 13.4, 2.6 Hz, 1H), 2.51 (d, J ¼ 15.2 Hz, 1H), 2.22–2.14 (m, 1H), (6d). Off white solid; yield 0.0211 g, 92%; H NMR (400 MHz,
1.93–1.88 (m, 2H), 1.85 (s, 3H), 1.73–1.66 (m, 2H), 1.53–1.41 (m, CDCl3) d 7.12 (d, J ¼ 8.8 Hz, 2H), 6.82 (d, J ¼ 8.8 Hz, 2H), 6.71 (s,
1H); 13C NMR (150 MHz, CDCl3) d 208.6, 204.4, 140.8, 140.2, 0.7H; NH), 4.04 (q, J ¼ 7.2 Hz, 1H), 3.78 (s, 3H), 2.10 (s, 6H), 1.56
130.4, 130.2, 128.4, 128.1, 126.9, 126.4, 73.5, 53.3, 42.3, 31.2, (d, J ¼ 7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3) d 157.6, 149.8,
26.9, 25.2, 22.8. HRMS (ESI-TOF) m/z: [C21H22O2 + Na]+ Calcd for 141.8, 137.5, 128.1, 119.7, 116.3, 113.5, 55.2, 33.2, 20.4, 11.6.
C
17H17N2O 265.1336; found 265.1337.
4-[1-((4-Methoxy-phenyl)ethy)]-3,5-dimethyl-1H-pyrazole
1
C
21H22O2Na 329.1512; found 329.1519.
3-Oxo-2-(1-phenyl-ethyl)-butyric acid methyl ester (5p).15c 231.1492; found 231.1496.
Colourless liquid; yield 0.0274 g, 62%; 1H NMR (400 MHz,
4-Benzhydryl-3-methyl-1,5-diphenyl-1H-pyrazole (6e). Off
HRMS (ESI-TOF) m/z: [C14H18N2O + H]+ calcd for C14H19N2O
1
CDCl3) d 7.30–7.26 (m, 4H), 7.22–7.18 (m, 6H), 3.81 (d, J ¼ white liquid; yield 0.0209 g, 52%; H NMR (400 MHz, CDCl3)
10.8 Hz, 1H), 3.76 (m, 3H), 3.75 (d, J ¼ 10.8 Hz, 1H), 3.58–3.49 d 7.29 (d, J ¼ 6.8 Hz, 4H), 7.26 (bs, 4H), 7.25–7.20 (m, 6H), 7.10
(m, 2H), 3.43 (s, 3H), 2.29 (s, 3H), 1.91 (s, 3H), 1.29 (d, J ¼ 6.8 Hz, (d, J ¼ 8.0 Hz, 4H), 7.02 (d, J ¼ 7.6 Hz, 2H), 5.41 (s, 1H), 1.92 (s,
3H), 1.24 (d, J ¼ 7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3) d 202.3, 3H); 13C NMR (125 MHz, CDCl3) d 148.7, 143.1, 141.4, 140.1,
202.3, 169.1, 168.6, 143.2, 143.0, 128.7, 128.5, 127.4, 127.3, 130.7, 130.2, 129.2, 128.6, 128.4, 128.3, 128.2, 126.4, 126.2,
127.0, 126.8, 67.4, 66.8, 52.4, 52.1, 40.1, 39.8, 29.9, 29.6, 20.6, 124.4, 121.2, 46.4, 29.7 (grease), 13.9. HRMS (ESI-TOF) m/z:
20.1.
2-Benzhydryl-3-oxo-butyric acid methyl ester (5q).15c White
[C29H24N2 + H]+ calcd for C29H25N2 401.2013; found 401.2013.
4-Benzhydryl-1,3,5-triphenyl-1H-pyrazole (6f). Off white
solid; yield 0.0548 g, 97%; H NMR (400 MHz, CDCl3) d 7.31– solid; yield 0.0190 g, 41%; 1H NMR (400 MHz, CDCl3) d 7.36 (dd,
7.24 (m, 8H), 7.20–7.15 (m, 2H), 4.80 (d, J ¼ 12.4 Hz, 1H), 4.57 (d, J ¼ 7.2, 2.4 Hz, 2H), 7.28–7.26 (m, 3H), 7.24–7.22 (m, 3H), 7.21–
J ¼ 12.0 Hz, 1H), 3.53 (s, 3H), 2.09 (s, 3H); 13C NMR (100 MHz, 7.15 (m, 4H), 7.14–7.05 (m, 7H), 7.00 (dd, J ¼ 7.6, 2.8 Hz, 4H),
CDCl3) d 201.7, 168.2, 141.6, 141.1, 128.9, 128.7, 127.9, 127.6, 6.86 (d, J ¼ 7.2 Hz, 2H), 5.66 (s, 1H); 13C NMR (100 MHz, CDCl3)
1
127.0, 126.9, 65.0, 52.5, 50.9, 30.1.
d 143.2, 130.6, 129.5, 129.1, 128.5, 128.0, 127.8, 127.6, 126.7,
3-Oxo-2-(1-phentyl-ethyl)-butyric acid ethyl ester (5r).16b Col- 125.9, 124.8, 120.9, 46.9, 29.7 (grease). HRMS (ESI-TOF) m/z:
1
ourless liquid; yield 0.0356 g, 76%; H NMR (400 MHz, CDCl3) [C34H26N2 + H]+ calcd for C34H27N2 463.2169; found 463.2173.
d 7.31–7.25 (m, 4H), 7.22–7.18 (m, 6H), 4.22 (q, J ¼ 7.2 Hz, 2H),
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0.0233 g, 69% w.r.t 6l1; 1H NMR (500 MHz, CDCl3) d 7.64 (d, J ¼
7.5 Hz, 3H), 7.52 (d, J ¼ 7.5 Hz, 2H), 7.41–7.35 (m, 7H), 7.33–7.28
(m, 3H), 7.23–7.20 (m, 1.6H), 7.17–7.14 (t, J ¼ 7.3 Hz, 0.5H), 7.01
(d, J ¼ 7.0 Hz, 1H), 6.49 (dt, J ¼ 16.0, 5.0 Hz, 1H), 6.36 (d, J ¼
16.0 Hz, 1H), 3.60 (dd, J ¼ 4.5, 2.0 Hz, 1H), 2.76 (t, J ¼ 8.0 Hz,
4-Cinnamyl-3-methyl-5-phenyl-1H-pyrazole (6g). White solid;
yield 0.0206 g, 75%; H NMR (400 MHz, CDCl3) d 7.55 (d, J ¼
1
8.4 Hz, 2H), 7.39 (t, J ¼ 7.4 Hz, 2H), 7.35–7.30 (m, 3H), 7.29 (bs,
1H), 7.26 (d, J ¼ 3.6 Hz, 1H), 7.20 (t, J ¼ 7.0 Hz, 1H), 6.36–6.28
(m, 2H), 3.45 (d, J ¼ 4.4 Hz, 2H), 2.23 (s, 3H); 13C NMR (100
MHz, CDCl3) d 146.2, 143.9, 137.5, 132.0, 130.2, 128.8, 128.6,
128.5, 127.9, 127.6, 127.0, 126.1, 112.6, 26.7, 10.8. HRMS (ESI-
TOF) m/z: [C19H18N2 + H]+ calcd for C19H19N2 275.1543; found
275.1546.
1H), 2.52 (t, J ¼ 7.5 Hz, 1H), 1.77 (dt, J ¼ 15.5, 7.5 Hz, 1H); 13
C
NMR (125 MHz, CDCl3) d 141.8, 137.5, 131.2, 129.7, 128.8, 128.7,
128.5, 128.4, 128.2, 128.1, 127.9, 127.8, 127.7, 127.1, 126.2,
125.7, 115.7, 112.4, 35.5, 31.8, 27.2, 22.9; DEPT 13C NMR (125
MHz, CDCl3) d 131.2, 129.7, 128.8, 128.7, 128.5, 128.4, 128.2,
128.1, 127.9, 127.8, 127.7, 127.1, 126.2, 125.7, 35.5, 31.8, 27.2,
22.9. HRMS (ESI-TOF) m/z: [C24H20N2 + H]+ & [C24H22N2 + H]+
calcd for C24H21N2 & C24H23N2 337.1700 & 339.1856; found
337.1784 & 339.1857.
4-Cinnamyl-3,5-diphenyl-1H-pyrazole (6h). White solid; yield
0.0281 g, 83%; 1H NMR (400 MHz, CDCl3) d 7.65 (d, J ¼ 6.8 Hz,
4H), 7.42–7.33 (m, 6H), 7.31–7.21 (m, 4H), 7.21 (t, J ¼ 6.8 Hz,
1H), 6.50 (dt, J ¼ 16.0, 4.8 Hz, 2H), 6.36 (d, J ¼ 16.0 Hz, 4H),
3.60–3.59 (m, 2H).; 13C NMR (100 MHz, CDCl3) d 147.3, 137.5,
131.7, 131.2, 129.7, 128.7, 128.5, 128.1, 127.6, 127.1, 126.1,
112.4, 29.7 (grease), 27.2. HRMS (ESI-TOF) m/z: [C24H20N2 + H]+
calcd for C24H21N2 337.1700; found 337.1707.
Oxybis(methanetriyl)tetrabenzene.16 Colourless semi-liquid;
1
yield 0.0994 g, 71%; H NMR (400 MHz, CDCl3) d 7.40 (d, J ¼
7.6 Hz, 8H), 7.34 (t, J ¼ 7.6 Hz, 4H), 7.30–7.26 (m, 4H), 5.44 (s,
2H); 13C NMR (100 MHz, CDCl3) d 142.2, 128.4, 127.4, 127.3,
80.1.
4-(1,3-Diphenylallyl)-3,5-diphenyl-1H-pyrazole (6i). White
1
solid; yield 0.0226 g, 55%; H NMR (400 MHz, CDCl3) d 7.39–
((1E,10E)-Oxybis(prop-1-ene-3,1-diyl))dibenzene.16 Off white
liquid; yield 0.0673 g, 67%; 1H NMR (500 MHz, CDCl3) d 7.43 (d,
J ¼ 7.5 Hz, 4H), 7.35 (dd, J ¼ 10.3, 4.8 Hz, 4H), 7.32–7.26 (m, 2H),
6.68 (d, J ¼ 16.0 Hz, 2H), 6.36 (dt, J ¼ 15.9, 6.0 Hz, 2H), 4.24 (dd,
J ¼ 6.0, 1.5 Hz, 4H); 13C NMR (125 MHz, CDCl3) d 136.7, 132.6,
128.6, 127.7, 126.5, 126.1, 70.8.
7.37 (m, 4H), 7.31 (d, J ¼ 6.8 Hz, 6H), 7.24–7.16 (m, 8H), 7.09 (d, J
¼ 7.2 Hz, 2H), 6.45–6.34 (m, 2H), 5.09 (d, J ¼ 6.8 Hz, 1H); 13C
NMR (100 MHz, CDCl3) d 147.3, 143.6, 137.2, 132.1, 131.6, 131.5,
128.8, 128.5, 128.4, 128.2, 128.2, 128.1, 127.2, 126.2, 117.3, 43.8,
29.7 (grease). HRMS (ESI-TOF) m/z: [C30H24N2 + H]+ calcd for
C
30H25N2 413.2013; found 413.2017.
4-(1,3-Diphenylallyl)-3,5-dimethyl-1H-pyrazole
&
4-(1,3-
diphenyl-propyl)-3,5-dimethyl-1H-pyrazole (6j) (1.2 : 1). Off
white liquid; yield 0.0149 g, 52% w.r.t 6j1; H NMR (500 MHz,
Conflicts of interest
1
There are no conicts to declare.
CDCl3) d 7.37 (d, J ¼ 7.5 Hz, 1H), 7.32–7.27 (m, 3H), 7.25–7.21
(m, 2H), 7.19 (d, J ¼ 7.0 Hz, 1.4H), 7.17 (d, J ¼ 7.0 Hz, 0.5H), 7.14
(d, J ¼ 7.0 Hz, 1H), 6.62 (dd, J ¼ 15.5, 7.0 Hz, 0.67H), 6.32 (d, J ¼
16 Hz, 0.64H), 4.84 (d, J ¼ 7.0 Hz, 0.65H), 3.88 (dd, J ¼ 10,
6.3 Hz, 0.53H), 2.65 (ddt, J ¼ 13.8, 9.4, 5.5 Hz, 1H), 2.45–2.39 (m,
0.55H), 2.35–2.27 (m, 0.62H), 2.15 (s, 2.3H), 2.11 (s, 3H); 13C
NMR (125 MHz, CDCl3) d 144.4, 142.7, 141.9, 137.3, 131.2, 130.8,
128.5, 128.4, 128.3, 128.3, 128.2, 128.1, 127.5, 127.3, 126.3,
126.2, 125.9, 125.8, 43.6, 39.8, 35.5, 34.2, 11.8, 11.7; DEPT 13C
NMR (125 MHz, CDCl3) d 131.2, 130.8, 128.5, 128.4, 128.4, 128.3,
128.2, 128.1, 127.5, 127.3, 126.3, 126.2, 125.9, 125.8, 43.6, 39.8,
35.5, 34.2, 11.8, 11.7. HRMS (ESI-TOF) m/z: [C20H20N2 + H]+ &
[C20H22N2 + H]+ calcd for C20H21N2 & C20H23N2 289.1700 &
291.1856; found 289.1681 & 291.1857.
Acknowledgements
We thank SERB for the NMR facility (grant number SR/FST/CSII-
026/2013).
Notes and references
1 (a) B. M. Trost, Acc. Chem. Res., 1996, 29, 355; (b) B. M. Trost
and D. L. Van Vranken, Chem. Rev., 1996, 96, 395; (c)
M. Yasuda, T. Somyo and A. Baba, Angew. Chem., Int. Ed.,
2006, 45, 793; (d) Z. Lu and S. Ma, Angew. Chem., Int. Ed.,
2008, 47, 258; (e) J. Zhang, J. Liao, Y. Wei, G. Cheng and
R. Luo, Mini-Rev. Org. Chem., 2018, 15, 476; (f) N. A. Butta
and W. Zhang, Chem. Soc. Rev., 2015, 44, 7929; (g)
G. Brahmachari, RSC Adv., 2016, 6, 64676.
2 B. M. Trost and M. L. Crawley, Chem. Rev., 2003, 103, 2921.
3 (a) A. Lei and X. A. Lu, Org. Lett., 2000, 2, 2357; (b) T. Konno,
T. Takehana, T. Ishihara and H. Yamanaka, Org. Biomol.
Chem., 2004, 2, 93; (c) R. Takeuchi and M. Kashio, J. Am.
Chem. Soc., 1998, 120, 8647; (d) K. Spielmann, G. Niel,
R. M. D. Figueiredo and J. M. Campagne, Chem. Soc. Rev.,
2018, 47, 1159.
4-Cinnamyl-3-methyl-5-phenyl-1H-pyrazole
&
3-methyl-5-
phenyl-4-(3-phenylpropyl)-1H-pyrazole (6k) (1 : 1). Off white
solid; yield 0.0154 g, 56% w.r.t 6k1; 1H NMR (500 MHz, CDCl3)
d 7.54 (d, J ¼ 7.5 Hz, 2H), 7.45 (d, J ¼ 7.0 Hz, 2H), 7.41–7.27 (m,
10H), 7.24 (bs, 1H), 7.21–7.16 (m, 2H), 7.12 (d, J ¼ 7.5 Hz, 2H),
6.39–6.29 (m, 2H), 3.45 (d, J ¼ 4.5 Hz, 2H), 2.62–2.55 (m, 4H),
2.24 (s, 3H), 2.21 (s, 3H), 1.82 (dt, J ¼ 15.4, 7.8 Hz, 2H); 13C NMR
(125 MHz, CDCl3) d 142.0, 137.5, 130.2, 128.8, 128.7, 128.6,
128.5, 128.4, 128.3, 127.9, 127.7, 127.6, 127.5, 127.0, 126.1,
125.7, 35.6, 32.0, 26.7, 22.8, 10.9. HRMS (ESI-TOF) m/z:
[C19H18N2 + H]+ & [C19H20N2 + H]+ calcd for C19H19N2
C19H21N2 275.1543 & 277.1700; found 275.1504 & 277.1700.
&
4 (a) B. C. Ranu, K. Chattopadhyay and L. Adak, Org. Lett.,
2007, 9, 4595; (b) H. Kinoshita, H. Shinokubo and
K. Oshima, Org. Lett., 2004, 6, 4085; (c) T. Nemoto,
T. Matsumoto, T. Masuda, T. Hitomi, K. Hatano and
Y. Hamada, J. Am. Chem. Soc., 2004, 126, 3690.
4-Cinnamyl-3,5-diphenyl-1H-pyrazole
& 3,5-diphenyl-4-(3-
phenyl-propyl)-1H-pyrazole (6l) (1.2 : 1). Off white solid; yield
9244 | RSC Adv., 2021, 11, 9235–9245
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RSC Advances
5 (a) H. Kurosawa, J. Chem. Soc., Dalton Trans., 1979, 939; (b) 15 (a) M. Rueping, B. J. Nachtsheim and A. Kuenkel, Org. Lett.,
R. Shibuya, L. Lin, Y. Nakahara, K. Mashima and
T. Ohshima, Angew. Chem., Int. Ed., 2014, 53, 4377.
2007, 9, 825; (b) Y. Yuan, Z. Shi, X. Feng and X. Liu, Appl.
Organomet. Chem., 2007, 21, 958; (c) P. Moriel and
´
A. B. Garcıa, Green Chem., 2014, 16, 4306.
6 (a) J. L. Renaud, C. Bruneau and B. Demerseman, Synlett,
´
´
´
2003, 3, 408; (b) C. Bruneau, J. L. Renaud and 16 (a) R. Sanz, A. Martınez, D. Miguel, J. M. Alvarez-Gutierrez
´
B. Demerseman, Pure Appl. Chem., 2008, 80, 861; (c)
S. Grubera and P. S. Pregosin, Adv. Synth. Catal., 2009, 351,
3235; (d) R. K. G. Siddappa, C. W. Chang and R. J. Chein,
Tetrahedron Lett., 2014, 55, 1031.
and F. Rodrıguez, Adv. Synth. Catal., 2006, 348, 1841; (b)
Z. S. Qureshi, K. M. Deshmukh, P. J. Tambade and B. M
Bhanage, Tetrahedron Lett., 2010, 51, 724.
17 M. C. Sau and M. Bhattacharjee, RSC Adv., 2020, 10, 36014.
7 H. Yang, L. Fang, M. Zhang and C. Zhu, Eur. J. Org. Chem., 18 P. K. Shaoo, S. S. Gawali and C. Gunanathan, ACS Omega,
2009, 666. 2018, 3, 124.
8 P. Kothandaraman, W. Rao, X. Zhang and P. W. H. Chan, 19 (a) M. J. Naim, O. Alam, F. Nawaz, Md. J. Alam and P. Alam, J.
Tetrahedron, 2009, 65, 1833.
Pharm. BioAllied Sci., 2016, 8, 2; (b) F. Keter and J. Darkwa,
BioMetals, 2012, 25, 9; (c) T. M. Beck and B. Breit, Eur. J.
Org. Chem., 2016, 5839; (d) P. Chauhan, S. Mahajan and
D. Enders, Chem. Commun., 2015, 51, 12890; (e)
M. C. Perez-Aguilar and C. Valdes, Angew. Chem., Int. Ed.,
2015, 54, 13729; (f) H. Wang, X. Sun, S. Zhang, G. Liu,
C. Wang, L. Zhu and H. Zhang, Synlett, 2018, 29, 2689; (g)
9 (a) S. B. Tang, X. Zhang, H. F. Tu and S. L. You, J. Am. Chem.
Soc., 2018, 140, 7737; (b) J. Zheng and B. Breit, Angew. Chem.,
Int. Ed., 2019, 58, 3392; (c) B. W. H. Turnbul and P. A. Evans,
J. Org. Chem., 2018, 83, 11463.
10 C. C. Bao, D. S. Zheng, X. Zhang and S. L. You,
Organometallics, 2018, 37, 4763.
´
11 (a) J. L. Roustan, J. Y. Merour and F. Houlihan, Tetrahedron
Lett., 1979, 20, 3721; (b) M. Mukhopadhyay and J. Iqbal,
Tetrahedron Lett., 1995, 36, 6761; (c) J. B. Baruah and
A. G. Samuelson, J. Organomet. Chem., 1989, 361, C57; (d)
K. Takizawa, T. Sekino, S. Sato, T. Yoshino, M. Kojima and
S. Matsunaga, Angew. Chem., Int. Ed., 2019, 58, 9199; (e)
S. Fustero, A. Simon-Fuentes and J. F. Sanz-Cervera, Org.
Prep. Proced. Int., 2009, 41, 253; (h) S. T. Heller and
S. R. Natarajan, Org. Lett., 2006, 8, 2675; (i) D. C. Schmitt,
A. P. Taylor, A. C. Flick and R. E. Kyne Jr, Org. Lett., 2015,
17, 1405; (j) N. Panda and A. K. Jena, J. Org. Chem., 2012,
77, 9401.
¨
D. Zell, V. Muller, U. Dhawa, M. Bursch, R. R. Presa, 20 C. Cazorla, M. Billamboz, H. Bricout, E. Monier and C. Len,
S. Grimme and L. Ackermann, Chem.–Eur. J., 2017, 23, Eur. J. Org. Chem., 2017, 1078.
12145; (f) Y. Suzuki, B. Sun, K. Sakata, T. Yoshino, 21 N. Gurbuz, S. Demir, I. Ozdemir, B. Cetinkaya and
S. Matsunaga and M. Kanai, Angew. Chem., Int. Ed., 2015, C. Bruneau, Tetrahedron, 2010, 66, 1346.
54, 9944; (g) H. Wang, M. M. Lorion and L. Ackermann, 22 P. N. Liu, Z. Y. Zhou and C. P. Lau, Chem.–Eur. J., 2007, 13,
¨
¨
¨
ACS Catal., 2017, 7, 3430; (h) U. Dhawa, C. Tian, W. Li and
L. Ackermann, ACS Catal., 2020, 10, 6457.
12 M. K. Gangwar, P. Dahiya, B. Emayavaramban and
B. Sundararaju, Chem.–Asian J., 2018, 13, 2445.
8610.
23 R. B. Watson, A. N. Golonka and C. S. Schindler, Org. Lett.,
2016, 18, 1310.
24 N. T. Patil and Y. Yamamoto, J. Org. Chem., 2004, 69, 6478.
13 (a) T. Yoshino, H. Ikemoto, S. Matsunga and M. Kanai, 25 (a) Y. Li, Z. Yu and S. Wu, J. Org. Chem., 2008, 73, 5647; (b)
Angew. Chem., Int. Ed., 2013, 52, 2207; (b) D. G. Yu,
X. Zhang, R. Qiu, C. Zhou, J. Yu, N. Li, S. Yin and X. Xu,
Tetrahedron, 2015, 71, 1011; (c) M. E. Lloris, N. Galvez,
J. Marquet and M. Moreno-Manas, Tetrahedron, 1991, 47,
8031; (d) S. A. Babu, M. Yasuda, Y. Tsukahara,
T. Yamauchi, Y. Wada and A. Baba, Synthesis, 2008, 11, 1717.
´
´
T. Gensch, F. de. Azambuja, S. Vasquez-Cespedes and
F. Glorius, J. Am. Chem. Soc., 2014, 136, 17722.
14 K. Motokura, N. Fujita, K. Mori, T. Mizugaki, K. Ebitani and
K. Kaneda, Angew. Chem., Int. Ed., 2006, 45, 2605.
© 2021 The Author(s). Published by the Royal Society of Chemistry
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