Palladium mediated one-pot synthesis of 3-aryl-cyclohexenones and 1,5-diketones from allyl alcohols and aryl ketones

Article abstract of DOI:10.1039/d0ob02515a

One-pot synthesis of Robinson annulated 3-aryl-cyclohexenones from allyl alcohols and ketones using palladium is reported. Long chain aliphatic or aryl substitutions at the C1 position of allyl alcohol result in the formation of 1,5-diketone products. This simple one-pot method avoids the use of highly electrophilic vinyl ketones.

Full text of DOI:10.1039/d0ob02515a

Organic &
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PAPER
Palladium mediated one-pot synthesis of
3-aryl-cyclohexenones and 1,5-diketones
from allyl alcohols and aryl ketones†‡
Cite this: Org. Biomol. Chem., 2021,
19, 1386
Shaikh Samser,
Priyabrata Biswal, Sushanta Kumar Meher and
Krishnan Venkatasubbaiah
*
Received 17th December 2020,
Accepted 13th January 2021
One-pot synthesis of Robinson annulated 3-aryl-cyclohexenones from allyl alcohols and ketones using
palladium is reported. Long chain aliphatic or aryl substitutions at the C1 position of allyl alcohol result in
the formation of 1,5-diketone products. This simple one-pot method avoids the use of highly electrophilic
vinyl ketones.
DOI: 10.1039/d0ob02515a
rsc.li/obc
ation of ketones using tandem isomerisation and C–H acti-
1. Introduction
vation of allyl alcohols.7 They also reported the synthesis of
There is considerable interest in the use of allylic alcohols as α-fluorinated ketones by combining the isomerisation of allyl
building blocks in organic synthesis since they react as alkylat- alcohols to ketones followed by α-fluorination.8 In addition,
ing or allylating compounds to yield diverse products.1 As the allylic alcohols also act as the enolate precursor as this moiety
hydroxyl group in allylic alcohols is considered to be a weak has a β-electrophilic centre that fosters nucleophilic addition
leaving group, usually they need a prefunctional transform- (1,4-addition), which results in β-functionalised carbonyl com-
ation of allylic alcohols into esters, halides, sulfonates, carbox- pounds. In this regard, it is worth mentioning that Kapur and
ylates, etc.2 A stoichiometric amount of Lewis acids such as co-workers reported the coupling of allyl alcohols with various
BEt3 or Ti(O-i-Pr)4 may optionally be triggered to activate anilines using a Pd-catalyst to afford β-amino ketones.9
them, but all these approaches lead to the production of sub-
Herein, we report the synthesis of 3-aryl-2-cyclohexenones
stantial wastes and affect the atom economy of the reaction, and 1,5-diketones by coupling allyl alcohols with a variety of
which can be prevented by direct catalytic activation.2 Allylic ketones using a palladium−BINOL phosphoric acid system.
alcohols can be used as enolate precursors in tandem reac-
tions leading to the formation of a new C–C bond.3 The enol
formed during the reaction tautomerizes to the corresponding
2. Results and discussion
carbonyl compounds, which can be achieved by simple metal-
catalysed isomerisation.3 This isomerization reaction is green,
We recently reported α-alkylation of ketones and N-alkylation
effective, safe and environment friendly, and occurs in one
of amines using alcohols as an alkylating agent.10 We were
step without generating by-products and without the need for
curious to investigate the reactivity of allyl alcohols as an alky-
toxic reagents, unlike the classical oxidation.4
lating agent. The reaction of 3-buten-2-ol with propiophenone
Grée and co-workers coupled allyl alcohols with various
was studied using palladium acetate, BINOL phosphoric acid
aldehydes using an iron carbonyl complex resulting in aldol
(BPA) and NaOH as the catalyst, ligand and base, respectively,
with the expectation to obtain a C-alkylated product. To our
surprise, we isolated 33% of 3-aryl-2-cyclohexenone (a
products.5 The same group reported the synthesis of
β-aminoketones from allyl alcohols and N-tert-butanesulfini-
mines using
a tandem isomerisation-Mannich reaction
Robinson annulated product11) from the reaction mixture
(Table 1, entry 1). As 3-aryl-2-cyclohexenones12 act as feedstock
for the synthesis of substituted phenols apart from acting as
structural motifs in bioactive molecules, we decided to explore
this reaction. Changing the palladium source to Pd2dba3 did
not yield any product (Table 1, entry 2); however, PdCl2
resulted in 29% of the product (Table 1, entry 3). Upon the
addition of 4 Å molecular sieves to the reaction mixture, the
product was isolated in 71% yield (Table 1, entry 4). Little or
approach.6 The Martín-Matute group reported the ortho-alkyl-
School of Chemical Sciences, National Institute of Science Education and Research
(NISER), HBNI, Bhubaneswar 752050, Odisha, India. E-mail: krishv@niser.ac.in
†Dedicated to Prof. T. K. Chandrashekar on his 65th birthday.
‡Electronic supplementary information (ESI) available: Characterization data
and X-ray analysis. CCDC 2023107. For ESI and crystallographic data in CIF or
other electronic format see DOI: 10.1039/d0ob02515a
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Table 1 Optimisation of Robinson’s annulation using allyl alcoholsa
Table 2 Substrate scope of Robinson’s annulation for aryl ketonesa
Palladium
(mol%)
Base
(equiv.)
Yieldc
(%)
S. no.
Ligand (mol%)
1
2
Pd(OAc)2(10)
Pd2dba3(10)
PdCl2(10)
BPA(10)
BPA(10)
BPA(10)
BPA(10)
BPA(20)
BPA(10)
BPA(10)
BPA(10)
BPA(10)
PPh3(10)
P(2-fur)3(10)
BPA(10)
—
NaOH(1)
NaOH(1)
NaOH(1)
NaOH(1)
NaOH(1)
LiOH(1)
Cs2CO3(1)
LiOtBu(1)
KOH(1)
NaOH(1)
NaOH(1)
NaOH(1)
NaOH(1)
NaOH(1)
NaOH(1)
NaOH(1)
NaOH(1)
33
ND
29
71
70
Trace
70
25
3
4b
Pd(OAc)2(10)
Pd(OAc)2(10)
Pd(OAc)2(10)
Pd(OAc)2(10)
Pd(OAc)2(10)
Pd(OAc)2(10)
Pd(OAc)2(10)
Pd(OAc)2(10)
—
Pd(OAc)2(10)
Pd(OAc)2(10)
Pd(OAc)2(10)
Pd(OAc)2(5)
Pd(OAc)2(7)
5b
6b
7b
8b
9b
45
10b
11b
12b
13b
14b
15b
16b
17b
Trace
ND
Trace
37
Trace
ND
53
dppe
1,10-Phenanthroline
BPA(5)
BPA(7)
61
a Reaction conditions: acetophenone (1 mmol), allyl alcohol (2 mmol)
and 0.8 mL of DCE (solvent) were stirred at room temperature for 24 h.
b 4 Å molecular sieves were used. c Isolated yield after column chrom-
atography. ND = not detected.
a Reaction conditions: 1 mmol ketone, 2 mmol allylic alcohol, 1 × 10−1
mmol Pd(OAc)2, 1 × 10−1 mmol of BINOL phosphoric acid, 1 mmol
NaOH, 4 Å molecular sieves and 0.8 mL of DCE were stirred at room
temperature for 24 h. b 6 mmol allylic alcohol − GC conversion.
no conversion was observed when phosphine or pyridine
ligands were used instead of BPA (Table 1, entries 10, 11, 14
and 15). A further decrease of catalyst loading resulted in
lower yields (Table 1, entries 16 and 17). With the optimised
conditions in hand, we checked the substrate scope of (Table 2, entries 2 and 17). On careful examination of the pro-
Robinson annulation with different aryl ketones and allylic ducts 2 and 17, we noticed the presence of two isomers, as is
alcohols. Acetophenone reacted with 3-buten-2-ol, 3-penten-2- evident by GC, GC-MS, and NMR. The peaks at RT 13.14 and
ol and 1-penten-3-ol to give the corresponding annulated pro- RT 12.63 (Fig. S40 and S41‡) correspond to the molecular
ducts in 77%, 67% and 45% isolated yield, respectively weight of 214 which is the molecular weight of the corres-
(Table 2, entries 4, 5 and 6). Acetophenone bearing fluorine at ponding annulated product of butyrophenone with 3-penten-2-
the para and ortho positions yielded the corresponding pro- ol. From GC, the ratio of the two isomers was found to be 4 : 1
ducts 7 and 8 in good yields. However, meta substituted aceto- (compound 17). Similarly, the ratio of isomers in the case of
phenone (3-fluoroacetophenone) resulted in a decrease in the the annulated product of propiophenone and 3-penten-2-ol
product yield (Table 2, entry 9). Our methodology has good tol- was 6.1 : 1 (compound 2). A heteroaromatic compound, 2-acet-
erance towards –CF3 and –Cl substitution on acetophenone ylthiophene, produced the annulated compound in 33% yield
(Table 2, entries 10–13). Electron donating –OMe at the ortho (Table 2, entry 19). A trace amount of conversion was observed
and meta positions gave lower yields (Table 2, entries 14 and in the case of 2-acetylpyridine possibly owing to the coordi-
15). Butyrophenone with 3-buten-2-ol resulted in 41% yield nation of the palladium metal to the N-atom of the pyridine
(Table 2, entry 16). Moreover, propiophenone and butyrophe- moiety. 2,6-Dimethoxyacetophenone failed to give the product,
none underwent annulation with 3-penten-2-ol to yield the whereas 4-bromoacetophenone underwent electrophilic substi-
corresponding products in 59% and 39% yields, respectively tution. 2-Acetylnaphthalene gave a moderate yield of 32%
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Table 3 Substrate scope of Robinson’s annulation for cyclic aryl
ketonesa
Table 4 Substrates scope for the synthesis of 1,5-diketonea
a Reaction conditions: 1 mmol ketone, 2 mmol allylic alcohol, 1 × 10−1
mmol Pd(OAc)2, 1 × 10−1 mmol of BINOL phosphoric acid, 1 mmol
NaOH, 4 Å molecular sieves and 0.8 mL of DCE were stirred at room
temperature for 24 h. b 6 mmol allylic alcohol − GC conversion.
(Table 2, entry 20). 1-Tetralone and 1-indanone with 3-penten-
2-ol resulted in 31% and 25% of the isolated product, respect-
ively (Table 3, entries 22 and 23). To our delight, compound 22
crystallized in a monoclinic system with a space group P21/n
which was analysed using single crystal X-ray crystallography.
The molecular structure of compound 22 is presented in
Table 3 and also in the ESI.‡
a Reaction conditions: 1 mmol ketone, 2 mmol allylic alcohol, 1 × 10−1
mmol Pd(OAc)2, 1 × 10−1 mmol of BINOL phosphoric acid, 1 mmol
NaOH, 4 Å molecular sieves and 0.8 mL of DCE were stirred at room
temperature for 24 h. b 6 mmol allylic alcohol − GC conversion.
Furthermore, 1-tetralone on reaction with 3-buten-2-ol gave
the corresponding annulated product in moderate yield
(Table 3, entry 21). The reaction did not proceed with aliphatic
and alicyclic systems such as 3-methylbutanone, acetone,
cyclopropylmethyl ketone and cyclohexyl methyl ketone. Under
the experimental conditions mentioned, a gram-scale experi-
ment of propiophenone (10 mmol) was performed. The reac-
tion proceeded smoothly and gave the desired product 1 in
58% yield (1.078 g).
without a base, the reaction of 1-penten-3-ol (without aceto-
phenone, using NMR) revealed the formation of 3-pentanone
along with 3-pentenone.15 (Scheme 1a). Yet another control
reaction carried out in the presence of a base resulted in,
To our surprise, increasing the alkyl chain from 1-penten-3-
ol to 1-hexen-3-ol resulted in 1,5-diketone as the only product.
Our attempts to make the annulated product from 1-hexen-3-ol
failed (Table S2, ESI‡). As 1,5 diketones play a significant role
in organic chemistry for the synthesis of many heterocycles,13
we screened the potential of this methodology. Propiophenone
and butyrophenone afforded the diketone in 58% and 33%
yield respectively (Table 4, entries 24 and 25). Interestingly,
acetophenone gave a low yield of 26% (Table 4, entry 27).
Substitution with electron-withdrawing and electron-donating
groups did not have much impact on the yield of the reaction
(Table 4, entries 28–30). 1-Tetralone resulted in 26% of the
product with 1-hexen-3-ol (Table 4, entry 26). Since cyclohexe-
nones acted as precursors for phenols as mentioned vide
supra, we attempted to prepare substituted phenols in one pot
using our methodology. However, our methodology failed to
yield aromatized phenols. A similar result was also observed
by Liu and co-workers14 when they used palladium acetate as a
catalyst.
To gain insight into the mechanism of the reaction, control
experiments were carried out. Under the optimized conditions, Scheme 1 Control experiments.
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3. Conclusion
In summary, we have developed a new palladium-BINOL phos-
phoric acid system for the synthesis of 3-aryl substituted cyclo-
hexenones or 1,5-diketones. The developed method has shown
good tolerance to different functional groups. The reaction of
aryl ketones with 3-buten-2-ol, 3-penten-2-ol or 1-penten-3-ol
resulted in Robinson’s annulated products; however, 1-hexen-
3-ol yielded 1,5-diketones as the only product.
4. Experimental section
General information
All reagents and solvents were obtained from commercial
sources. Solvents were purified according to standard pro-
cedures. BINOL phosphoric acid (BPA)19 and 2-methyl-1-phe-
nylheptane-1,5-dione (compound 33)20 were synthesized fol-
lowing the procedures reported in the literature. All 400 (or)
Scheme 2 Proposed mechanism.
1
700 MHz H and 100 (or) 176 MHz 13C spectra were recorded
exclusively, a saturated ketone. These results suggest that
under the reaction conditions, the allyl alcohol is converted to
the corresponding saturated ketone. The evolution of hydrogen
gas was studied as reported in the literature.16 As given in the
ESI,‡ we have taken 1-penten-3-ol under standard conditions
without the base and in another chamber, phenylacetylene
and palladium charcoal were taken in methanol. The crude
NMR of the reaction mixture of the second chamber showed
the presence of styrene along with ethyl benzene which sup-
ports that dehydrogenation takes place during the course of
the reaction. The base plays a major role in the conversion of
diketone to the corresponding annulated product. In order to
prove the role of the base, we stirred diketone (33) in the pres-
ence of NaOH which resulted in the annulated product 3 in
quantitative yield17 (crude NMR is given in the ESI‡). We
repeated a few reactions using 6 equivalents of allylic alcohols
under the optimized conditions. In most cases, we observed
higher conversions (Tables 2–4), suggesting that the formation
of species 32 limits the yield in these reactions.
on a spectrometer operating at 400 (or) 700 MHz. All
1H and 13C NMR spectra were referenced internally to
solvent signals. 19F NMR spectra were externally referenced to
α,α,α-trifluorotoluene in CDCl3 (δ = −63.73 ppm). 31P spectra
were referenced externally to H3PO4 in D2O (δ = 0). High-
resolution mass spectra (HRMS) were recorded using a Bruker
microTOF-QII mass spectrometer. Single-crystal X-ray diffrac-
tion data were collected at 114 K using Cu Kα radiation
(1.54184 Å). Crystallographic data for compound 22 (CCDC No.
2023107‡), and details of X-ray diffraction experiments and
crystal structure refinements are given in Table S1.‡ The struc-
tures were solved and refined with the SHELX suite of pro-
grams or Olex. All non-hydrogen atoms were refined with an-
isotropic displacement coefficients. The H atoms were placed
at calculated positions and refined as riding atoms. Sodium
hydroxide was ground to powder form using a mortar and
pestle and kept under vacuum when not in use.
General procedure for annulations and the diketone reac-
tion. Palladium acetate (0.022 g, 0.10 mmol), BINOL phospho-
ric acid (0.035 g, 0.10 mmol) and sodium hydroxide (0.039 g,
1.00 mmol) were taken in a scintillation vial. Aryl ketone
(1.00 mmol), allyl alcohol (2.00 mmol) and 0.8 mL of dichlor-
oethane (DCE) were added to it. Finally, 4 Å molecular sieves
were added to the reaction mixture and stirred at room temp-
erature for 24 hours. Then the reaction mixture was evaporated
under vacuum and purified by flash column chromatography
in ethyl acetate and n-hexane (1 : 4) as an eluent.
Based on the findings from the control experiments and
a
recent study,18 we propose the following mechanism
(Scheme 2). The palladium complex reacts with an allyl alcohol
to give the corresponding metal alkoxide B, which can undergo
β-hydride elimination to form the intermediate C. The inter-
mediate C can result in the formation of the corresponding
enol18a which can either undergo keto–enol tautomerisation to
form the observed species 32 or react with the ketone in the
presence of a base to form the enolic species E which results in
the diketone product F. The diketone in the presence of a base
undergoes aldol condensation to form the annulated product.
However, when we used 1-hexen-3-ol, the annulation did not
Analytical data for annulated compounds
6-Methyl-5,6-dihydro-[1,1′-biphenyl]-3(4H)-one21 (Table 2,
proceed (ESI, Table S2‡). The presence of α-hydrogen is essen- entry 1). Prepared from propiophenone (0.134 g, 1.00 mmol)
tial for the formation of an annulated product. To further and 3-buten-2-ol (0.144 g, 2.00 mmol). After purification by
support this hypothesis, we reacted propiophenone, acetophe- column chromatography, the compound was isolated as a
none and butyrophenone with phenylallyl alcohol under the yellow liquid (0.132 g, 71%). 1H NMR (700 MHz, CDCl3) δ =
optimized reaction conditions, which resulted in 1,5-diketones 7.49–7.48 (m, 2H), 7.41–7.37 (m, 3H), 6.25 (s, 1H), 3.18–3.13
(34–36) as the only product (Scheme 1c).
(m, 1H), 2.60 (ddd, J = 17.7, 12.9, 5.0, 1H), 2.44 (ddd, J = 17.2,
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4.6, 4.6, 1H), 2.34–2.29 (m, 1H), 2.04–1.90 (m, 1H), 1.18 (d, J = 7.39 (t, J = 7.5, 2H), 7.35–7.29 (m, 1H), 7.20 (d, J = 8.1, 2H),
7.2, 3H). 13C NMR (176 MHz, CDCl3) δ = 199.84, 165.40, 2.63 (t, J = 4.0, 2H), 2.53 (t, J = 4.0, 2H), 2.10 (p, J = 4.0, 2H),
138.41, 129.89, 128.91, 126.76, 125.22, 33.29, 31.27, 29.67, 1.72 (s, 3H). 13C NMR (101 MHz, CDCl3) δ = 200.08, 156.61,
18.44. HRMS (ESI): calculated for C13H14O ([M
187.1117, found: 187.1126.
+
H]+): 141.37, 131.88, 128.35, 127.85, 127.10, 37.80, 32.98, 22.83,
12.89. HRMS (ESI): calculated for C13H14O ([M
H]+):
+
5,6-Dimethyl-5,6-dihydro-[1,1′-biphenyl]-3(4H)-one (Table 2, 187.1117, found: 187.1104.
entry 2). Prepared from propiophenone (0.134 g, 1.00 mmol)
4′-Fluoro-5,6-dihydro-[1,1′-biphenyl]-3(4H)-one24 (Table 2,
and 3-penten-2-ol (0.172 g, 2.0 mmol). After purification by entry 7). Prepared from 4-fluoroacetophenone (0.138 g,
column chromatography, the compound was isolated as a 1.00 mmol) and 3-buten-2-ol (0.144 g, 2.0 mmol). After purifi-
yellow liquid (0.118 g, 59%). Data for the major isomer are cation by column chromatography, the compound was isolated
given. 1H NMR (400 MHz, CDCl3) δ = 7.54–7.52 (m, 2H), as a yellow liquid (0.10 g, 53%). 1H NMR (400 MHz, CDCl3) δ =
7.43–7.39 (m, 3H), 6.28 (s, 1H), 2.98 (dq, J = 8, 4, 1H), 7.55–7.49 (m, 2H), 7.12–7.08 (m, 2H), 6.37 (s, 1H), 2.75 (t, J =
2.54–2.41 (m, 2H), 2.37–2.29 (m, 2H), 1.13 (d, J = 6.8, 3H), 1.04 6.6, 2H), 2.48 (t, J = 6.7, 2H), 2.15 (p, J = 6.2, 2H). 13C NMR
(d, J = 7.1, 3H). 13C NMR (101 MHz, CDCl3) δ = 200.35, 166.64, (101 MHz, CDCl3) δ = 199.84, 163.91 (d, J = 251), 158.59,
138.17, 130.08, 128.96, 126.78, 124.50, 40.11, 36.87, 32.90, 134.99, 128.14 (d, J = 9), 125.41, 115.95 (d, J = 21), 37.28, 28.28,
18.78, 12.13. HRMS (ESI): calculated for C14H16O ([M + H]+): 22.89. HRMS (ESI): calculated for C12H11FO ([M + H]+):
201.1274, found: 201.1268.
2,6-Dimethyl-5,6-dihydro-[1,1′-biphenyl]-3(4H)-one (Table 2,
191.0867, found: 191.0871.
2′-Fluoro-5,6-dihydro-[1,1′-biphenyl]-3(4H)-one25 (Table 2,
entry 3). Prepared from propiophenone (0.134 g, 1.00 mmol) entry 8). Prepared from 2-fluoroacetophenone (0.138 g,
and 1-penten-3-ol (0.172 g, 2.0 mmol). After purification by 1.00 mmol) and 3-buten-2-ol (0.144 g, 2.00 mmol). After purifi-
column chromatography, the compound was isolated as color- cation by column chromatography, the compound was isolated
1
1
less oil (0.082 g, 41%). H NMR (400 MHz, CDCl3) δ = 7.39 (t, as a yellow liquid (0.129 g, 68%). H NMR (400 MHz, CDCl3) δ
J = 7.4, 2H), 7.32 (t, J = 7.1, 1H), 7.12 (d, J = 7.2, 2H), 2.84–2.76 = 7.38–7.32 (m, 2H), 7.19–7.16 (m, 1H), 7.10 (dd, J = 11.1, 8.5,
(m, 1H), 2.65 (ddd, J = 16.6, 11.4, 4.8, 1H), 2.46 (ddd, J = 16.9, 1H), 6.28 (s, 1H), 2.76 (t, J = 5.8, 2H), 2.50 (t, J = 8.0, 2H), 2.14
6.3, 4.8, 1H), 2.34–2.28 (m, 1H), 1.91–1.84 (m, 1H), 1.62 (s, (p, J = 6.2, 2H). 13C NMR (101 MHz, CDCl3) δ = 199.71, 159.96
3H), 1.02 (d, J = 7.1, 3H). 13C NMR (101 MHz, CDCl3) δ = (d, J = 251), 157.36 (d, J = 3), 134.60, 131.07 (d, J = 8), 128.98,
200.06, 161.53, 140.65, 131.23, 128.45, 127.74, 127.39, 35.73, 124.56 (d, J = 4), 116.650 (d, J = 23), 37.54, 29.81, 23.28. HRMS
34.34, 29.95, 18.20, 13.14. HRMS (ESI): calculated for C14H16O (ESI): calculated for C12H11FO ([M + H]): 191.0867, found:
([M + Na]+): 223.1093, found: 223.1093.
191.0879.
5,6-Dihydro-[1,1′-biphenyl]-3(4H)-one21 (Table 2, entry 4).
3′-Fluoro-5,6-dihydro-[1,1′-biphenyl]-3(4H)-one25 (Table 2,
Prepared from acetophenone (0.120 g, 1.00 mmol) and entry 9). Prepared from 3-fluoroacetophenone (0.138 g,
3-buten-2-ol (0.142 g, 2.0 mmol). After purification by column 1.00 mmol) and 3-buten-2-ol (0.144 g, 2.00 mmol). After purifi-
chromatography, the compound was isolated as a yellow liquid cation by column chromatography, the compound was isolated
(0.132 g, 77%). 1H NMR (400 MHz, CDCl3) δ = 7.56–7.52 (m, as a colorless liquid (0.068 g, 36%). 1H NMR (400 MHz, CDCl3)
2H), 7.43–7.39 (m, 3H), 6.42 (s, 1H), 2.81–2.74 (m, 2H), 2.49 (t, δ = 7.41–7.36 (m, 1H), 7.33–7.30 (m, 1H), 7.23–7.20 (m, 1H),
J = 8.0, 2H), 2.19–2.13 (m, 6.2, 2H). 13C NMR (101 MHz, CDCl3) 7.10 (tdd, J = 8.2, 2.5, 1.1, 1H), 6.39 (s, 1H), 2.74 (td, J = 6.2,
δ = 200.08, 159.96, 130.12, 128.90, 126.22, 125.59, 37.41, 28.26, 2H), 2.52–2.44 (m, 2H), 2.21–2.10 (m, 2H). 13C NMR (101 MHz,
22.96. HRMS (ESI): calculated for C12H12O ([M
173.0961, found: 173.0962.
+
H]+): CDCl3) δ = 199.81, 163.07 (d, J = 247), 158.36 (d, J = 2.6), 141.26
(d, J = 7.5), 130.44 (d, J = 8.4), 126.27, 121.89 (d, J = 2.9), 116.87
5-Methyl-5,6-dihydro-[1,1′-biphenyl]-3(4H)-one22 (Table 2, (d, J = 21.4), 113.23 (d, J = 22.3), 22.84, 28.21, 37.36. 19F NMR
entry 5). Prepared from acetophenone (0.120 g, 1.00 mmol) (376 MHz, CDCl3) δ = −112.15. HRMS (ESI): calculated for
and 3-penten-2-ol (0.172 g, 2.0 mmol). After purification by C12H11FO ([M + H]+): 191.0867, found: 191.0871.
column chromatography, the compound was isolated as a
4′-Chloro-5,6-dihydro-[1,1′-biphenyl]-3(4H)-one25 (Table 2,
yellow liquid (0.124 g, 67%). 1H NMR (400 MHz, CDCl3) δ = entry 10). Prepared from 4-chloroacetophenone (0.155 g,
7.55–7.52 (m, 2H), 7.43–7.39 (m, 3H), 6.41 (s,1H), 2.84 (dd, J = 1.00 mmol) and 3-buten-2-ol (0.144 g, 2.00 mmol). After purifi-
17.3, 3.8, 1H), 2.56 (dd, J = 16.1, 3.6, 1H), 2.49–2.42 (m, 1H), cation by column chromatography, the compound was isolated
2.38–2.26 (m, 1H), 2.17 (dd, J = 16.1, 12.1, 1H), 1.17 (d, J = 6.5, as a yellow liquid (0.10 g, 49%). 1H NMR (700 MHz, CDCl3) δ =
3H). 13C NMR (101 MHz, CDCl3) δ = 200.33, 159.24, 138.93, 7.46 (d, J = 8.6, 2H), 7.38 (d, J = 8.6, 2H), 6.38 (s, 1H), 2.73 (t, J
130.10, 128.89, 126.26, 125.26, 45.59, 36.68, 30.47, 21.44. = 6, 2H), 2.48 (t, J = 6.8, 2H), 2.15 (p, J = 6.2, 2H). 13C NMR
HRMS (ESI): calculated for C13H14O ([M + H]+): 187.1117, (176 MHz, CDCl3) δ = 199.79, 158.43, 137.31, 136.16, 129.13,
found: 187.1121.
2-Methyl-5,6-dihydro-[1,1′-biphenyl]-3(4H)-one23 (Table 2, C12H11ClO ([M + Na]+): 229.0391, found: 229.0402.
entry 6). Prepared from acetophenone (0.120 g, 1.00 mmol)
4′-(Trifluoromethyl)-5,6-dihydro-[1,1′-biphenyl]-3(4H)-one25
127.49, 125.76, 37.30, 28.13, 22.85. HRMS (ESI): calculated for
and 1-penten-3-ol (0.172 g, 2.0 mmol). After purification by (Table 2, entry 11). Prepared from 4′-(trifluoromethyl)aceto-
column chromatography, the compound was isolated as a phenone (0.188 g, 1.00 mmol) and 3-buten-2-ol (0.144 g,
yellow liquid (0.083 g, 45%). 1H NMR (400 MHz, CDCl3) δ = 2.00 mmol). After purification by column chromatography, the
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compound was isolated as a yellow gel (0.094 g, 39%). 1H NMR and 3-buten-2-ol (0.144 g, 2.00 mmol). After purification by
(700 MHz, CDCl3) δ = 7.66 (d, J = 8.3, 2H), 7.62 (d, J = 8.2, 2H), column chromatography, the compound was isolated as a
6.42 (s, 1H), 2.77 (t, J = 5.9, 2H), 2.50 (t, J = 6.8, 2H), 2.18 (p, J = yellow liquid (0.082 g, 41%). 1H NMR (400 MHz, CDCl3) δ =
6.3, 2H). 13C NMR (176 MHz, CDCl3) δ = 199.63, 158.20, 7.52–7.49 (m, 2H), 7.41–7.38 (m, 3H), 6.24 (s, 1H), 2.94–2.88
142.57, 131.71 (q, J = 32), 128.51, 127.03, 126.54, 125.85 (q, J = (m, 1H), 2.54 (ddd, J = 17.9, 12.2, 6.1, 1H), 2.47–2.40 (m, 1H),
3.5), 123.95 (q, J = 271), 37.32, 28.27, 22.85. 19F NMR 2.26–2.05 (m, 2H), 1.61–1.43 (m, 2H), 0.95 (t, J = 7.4, 3H). 13C
(376 MHz, CDCl3) δ = −62.58. HRMS (ESI): calculated for NMR (101 MHz, CDCl3) δ = 199.92, 165.07, 138.78, 129.88,
C13H11F3O ([M + H]+): 241.0835, found: 241.0849.
128.91, 126.74, 125.50, 38.11, 33.07, 29.84, 25.26, 24.71, 12.81.
2-Methyl-4′-(trifluoromethyl)-5,6-dihydro-[1,1′-biphenyl]-3(4H)- HRMS (ESI): calculated for C14H16O ([M + Na]+): 223.1093,
one (Table 2, entry 12). Prepared from 4′-(trifluoromethyl)aceto- found: 223.1076.
phenone (0.188 g, 1.00 mmol) and 1-penten-3-ol (0.172 g,
6-Ethyl-5-methyl-5,6-dihydro-[1,1′-biphenyl]-3(4H)-one (Table 2,
2.00 mmol). After purification by column chromatography, the entry 17). Prepared from butyrophenone (0.148 g, 1.00 mmol)
compound was isolated as a yellow liquid (0.063 g, 25%). 1H and 3-penten-2-ol (0.172 g, 2.00 mmol). After purification by
NMR (400 MHz, CDCl3) δ = 7.65 (d, J = 8.3, 2H), 7.31 (d, J = 7.9, column chromatography, the compound was isolated as a
2H), 2.63–2.58 (m, 2H), 2.54 (t, J = 8.0, 2H), 2.11 (p, J = 8.0, yellow liquid (0.083 g, 39%). Only the major isomer data are
1
2H), 1.69 (s, 3H). 13C NMR (101 MHz, CDCl3) δ = 199.66, presented. H NMR (400 MHz, CDCl3) δ = 7.51–7.46 (m, 2H),
154.83, 145.08, 132.74, 130.08 (q, J = 33), 125.60 (q, J = 4), 7.42–7.39 (m, 3H), 6.24 (s, 1H), 2.91–2.79 (m, 1H), 2.58–2.46
124.04 (q, J = 273) 37.83, 32.84, 22.91, 12.94. 19F NMR (m, 1H), 2.36 (d, J = 9.9, 2H), 1.78–1.65 (m, 2H), 1.50–1.39 (m,
(376 MHz, CDCl3) δ = −62.57. HRMS (ESI): calculated for 1H), 1.17 (d, J = 6.9, 3H), 0.75 (t, J = 7.5, 3H). 13C NMR
C14H13F3O ([M + H]+): 255.0991, found: 255.0987.
(101 MHz, CDCl3) δ = 200.60, 166.72, 139.87, 129.85, 128.89,
3′-(Trifluoromethyl)-5,6-dihydro-[1,1′-biphenyl]-3(4H)-one12b 126.72, 125.49, 43.51, 41.30, 33.62, 21.42, 18.85, 13.64. HRMS
(Table 2, entry 13). Prepared from 3′-(trifluoromethyl)aceto- (ESI): calculated for C15H18O ([M + Na]+): 237.1250, found:
phenone (0.188 g, 1.00 mmol) and 3-buten-2-ol (0.144 g, 237.1240.
2.00 mmol). After purification by column chromatography, the
6-Ethyl-2-methyl-5,6-dihydro-[1,1′-biphenyl]-3(4H)-one (Table 2,
compound was isolated as a yellow gel (0.079 g, 33%). 1H NMR entry 18). Prepared from butyrophenone (0.148 g, 1.00 mmol)
(400 MHz, CDCl3) δ = 7.76 (s, 1H), 7.71 (d, J = 7.8, 1H), 7.66 (d, and 1-penten-3-ol (0.172 g, 2.00 mmol). After purification by
J = 7.8, 1H), 7.54 (t, J = 7.8, 1H), 6.43 (s, 1H), 2.79 (td, J = 6.1, column chromatography, the compound was isolated as a
1.4, 2H), 2.51 (t, J = 8.0, 2H), 2.19 (p, J = 6.3, 2H). 13C NMR yellow liquid (0.071 g, 33%). 1H NMR (400 MHz, CDCl3) δ =
(101 MHz, CDCl3) δ = 199.61, 158.10, 139.87, 129.49, 129.39, 7.39 (t, J = 7.3, 2H), 7.32 (t, J = 7.3, 1H), 7.13 (d, J = 6.9, 2H),
126.71, 126.58 (q, J = 4), 123.029 (q, J = 4), 37.31, 28.23, 22.85. 2.64–2.52 (m, 2H), 2.46–2.39 (m, 1H), 2.28–2.19 (m, 1H),
19F NMR (376 MHz, CDCl3) δ = −62.69. HRMS (ESI): calculated 2.07–2.00 (m, 1H), 1.63 (s, 3H), 1.45–1.35 (m, 2H), 0.85 (t, J =
for C13H11F3O ([M + Na]+): 263.0654, found: 263.0651.
7.4, 3H). 13C NMR (101 MHz, CDCl3) δ = 200.17, 161.08,
2′-Methoxy-5,6-dihydro-[1,1′-biphenyl]-3(4H)-one25 (Table 2, 140.80, 131.36, 128.39, 127.78, 127.62, 42.50, 33.87, 25.25,
entry 14). Prepared from 2′-methoxyacetophenone (0.15 g, 23.94, 13.19, 12.64. HRMS (ESI): calculated for C15H18O ([M +
1.00 mmol) and 3-buten-2-ol (0.144 g, 2.00 mmol). After purifi- Na]+): 237.1250, found: 237.1265.
cation by column chromatography, the compound was isolated
3-(Thiophen-2-yl)cyclohex-2-en-1-one23 (Table 2, entry 19).
1
as a yellow gel (0.0586 g, 29%). H NMR (400 MHz, CDCl3) δ = Prepared from 2-acetylthiophene (0.126 g, 1.00 mmol) and
7.37–7.30 (m, 1H), 7.20 (dd, J = 7.2, 1.7, 1H), 7.00–6.90 (m, 3-buten-2-ol (0.144 g, 2.00 mmol). After purification by
2H), 6.20 (s, 1H), 3.84 (s, 3H), 2.74 (td, J = 6.2, 1.2, 2H), 2.48 (t, column chromatography, the compound was isolated as a
J = 8.0, 2H), 2.10 (p, J = 8.0, 2H). 13C NMR (101 MHz, CDCl3) δ yellow liquid (0.0587 g, 33%). H NMR (400 MHz, CDCl3) δ =
1
= 200.35, 161.89, 156.74, 130.46, 129.79, 128.89, 128.34, 7.44 (d, J = 5.0, 1H), 7.38 (d, J = 3.7, 1H), 7.09 (dd, J = 5.1,
120.88, 111.29, 55.59, 37.69, 30.21, 23.45. HRMS (ESI): calcu- 3.8, 1H), 6.43 (s, 1H), 2.79 (t, J = 6.0, 2H), 2.46 (t, J = 6.6,
lated for C13H14O2 ([M + H]+): 203.1067, found: 203.1087.
2H), 2.14 (p, J = 6.3, 2H). 13C NMR (101 MHz, CDCl3) δ =
3′-Methoxy-5,6-dihydro-[1,1′-biphenyl]-3(4H)-one25 (Table 2, 199.59, 152.58, 131.42, 128.89, 128.40, 127.45, 122.87, 37.37,
entry 15). Prepared from 3′-methoxyacetophenone (0.150 g, 28.17, 22.58. HRMS (ESI): calculated for C10H10OS ([M + H]+):
1.00 mmol) and 3-buten-2-ol (0.144 g, 2.00 mmol). After purifi- 179.0525, found: 179.0537.
cation by column chromatography, the compound was isolated
3-(Naphthalen-2-yl)cyclohex-2-en-1-one23 (Table 2, entry 20).
1
as a white solid (0.070 g, 35%). H NMR (400 MHz, CDCl3) δ = Prepared from 2-acetylnaphthalene (0.170 g, 1.00 mmol) and
7.32 (t, J = 8.0, 1H), 7.14–7.11 (m, 1H), 7.05–7.04 (m, 1H),6.41 3-buten-2-ol (0.144 g, 2.00 mmol). After purification by column
(s, 1H), 3.83 (s, 3H), 2.76 (td, J = 6.1, 1.5, 2H), 2.49 (t, J = 8.0, chromatography, the compound was isolated as a yellow liquid
2H), 2.15 (p, J = 4.0, 2H). 13C NMR (101 MHz, CDCl3) δ = (0.071 g, 32%). 1H NMR (400 MHz, CDCl3) δ = 8.01 (s, 1H),
200.19, 159.90, 140.41, 129.89, 125.73, 118.69, 115.56, 111.83, 7.89–7.82 (m, 3H), 7.65 (dd, J = 8.7, 1.9, 1H), 7.55–7.49 (m,
100.05, 55.48, 37.42, 28.33, 22.93. HRMS (ESI): calculated for 2H), 6.57 (s, 1H), 2.94–2.87 (m, 2H), 2.56–2.49 (m, 2H),
C13H14O2 ([M + H]+): 203.1067, found: 203.1075.
2.24–2.18 (m, 2H). 13C NMR (101 MHz, CDCl3) δ = 200.05,
6-Ethyl-5,6-dihydro-[1,1′-biphenyl]-3(4H)-one26 (Table 2, 159.60, 136.09, 134.11, 133.22, 128.82, 128.63, 127.80, 127.33,
entry 16). Prepared from butyrophenone (0.148 g, 1.00 mmol) 126.84, 126.27, 125.89, 123.44, 37.47, 28.23, 22.99. HRMS
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(ESI): calculated for C16H14O ([M + H]+): 223.1117, found: chromatography, the compound was isolated as a yellow liquid
223.1119.
(0.081 g, 33%). 1H NMR (400 MHz, CDCl3) δ = 8.00–7.97 (m,
1,9,10,10a-Tetrahydrophenanthren-3(2H)-one27 (Table 3, 2H), 7.15–7.10 (m, 3H), 2.97 (t, J = 8.0, 2H), 2.54–2.50 (m, 2H),
entry 21). Prepared from 1-tetralone (0.146 g, 1.00 mmol) 2.38 (t, J = 8.0, 2H), 2.00 (p, J = 8.0, 2H), 1.64–1.55 (m, 3H),
and 3-buten-2-ol (0.144 g, 2.00 mmol). After purification by 0.93–0.88 (m, 6H). 13C NMR (101 MHz, CDCl3) δ 210.93,
column chromatography, the compound was isolated as a 204.13, 137.45, 133.17, 128.80, 128.32, 46.44, 44.84, 40.01,
yellow gel (0.061 g, 31%). 1H NMR (400 MHz, CDCl3) δ = 25.59, 25.27, 17.35, 13.82, 11.82. HRMS (ESI): calculated for
7.78 (d, J = 8.3, 1H), 7.33 (t, J = 7.4, 1H), 7.29–7.23 (m, 1H), C16H22O2 ([M + H]+): 247.1693, found: 247.1688.
7.20 (t, J = 7.0, 1H), 6.66 (s, 1H), 3.05–2.87 (m, 2H),
2-(3-Oxohexyl)-3,4-dihydronaphthalen-1(2H)-one (Table 4,
2.71–2.42 (m, 3H), 2.24–2.18 (m, 1H), 2.10–2.04 (m, 1H), entry 26). Prepared from 1-tetralone (0.146 g, 1.00 mmol) and
1.88–1.77 (m, 1H), 1.62 (dq, J = 12.7, 5.3, 1H). 13C NMR 1-hexen-3-ol (0.200 g, 2.00 mmol). After purification by column
(101 MHz, CDCl3) δ = 200.37, 158.41, 139.93, 131.40, 130.68, chromatography, the compound was isolated as a white solid
129.76, 126.72, 125.31, 120.52, 37.52, 37.27, 30.68, 30.44, (0.0635 g, 26%). 1H NMR (400 MHz, CDCl3) δ = 8.00 (d, J = 7.8,
30.13. HRMS (ESI): calculated for C14H14O ([M + Na]+): 1H), 7.48–7.40 (m, 1H), 7.32–7.26 (m, 1H), 7.22 (d, J = 7.7, 1H),
221.0937, found: 221.0944.
3.03–2.96 (m, 2H), 2.59 (t, J = 7.5, 2H), 2.55–2.46 (m, 1H), 2.40
1-Methyl-1,9,10,10a-tetrahydrophenanthren-3(2H)-one (Table 3, (t, J = 7.3, 2H), 2.25–2.04 (m, 2H), 1.97–1.75 (m, 2H), 1.60 (sext,
entry 22). Prepared from 1-tetralone (0.146 g, 1.00 mmol) and J = 7.4, 2H), 0.91 (t, J = 7.4, 3H). 13C NMR (101 MHz, CDCl3) δ
3-penten-2-ol (0.172 g, 2.00 mmol). After purification by 211.20, 200.25, 144.00, 133.39, 132.54, 128.84, 127.48, 126.73,
column chromatography, the compound was isolated as a 46.85, 44.88, 40.37, 29.20, 28.59, 24.17, 17.45, 13.90. HRMS
1
white solid (0.066 g, 31%). H NMR (400 MHz, CDCl3) δ = 7.77 (ESI): calculated for C16H20O2 ([M + Na]+): 267.1356, found:
(d, J = 8.0, 1H), 7.32 (t, J = 8.0, 1H), 7.26–7.18 (m, 2H), 6.66 (s, 267.1369.
1H), 2.96–2.92 (m, 2H), 2.52 (dd, J = 12.0, 4.0, 1H), 2.38–2.33
1-Phenyloctane-1,5-dione17 (Table 4, entry 27). Prepared
(m, 3H), 2.05–1.93 (m, 1H), 1.51–1.40 (m, 1H), 1.19 (d, J = 4.0, from acetophenone (0.120 g, 1.00 mmol) and 1-hexen-3-ol
3H). 13C NMR (101 MHz, CDCl3) δ = 200.20, 158.23, 140.06, (0.200 g, 2.00 mmol). After purification by column chromato-
131.68, 130.60, 129.61, 126.76, 125.67, 120.79, 46.08, 44.25, graphy, the compound was isolated as a white solid (0.056 g,
35.35, 30.16, 27.38, 19.68. HRMS (ESI): calculated for C15H16O 26%). 1H NMR (400 MHz, CDCl3) δ = 7.97–7.95 (m, 2H),
([M + H]+): 213.1274, found: 213.1277.
7.58–7.52 (m, 1H), 7.48–7.44 (m, 2H), 3.01 (t, J = 8.0, 2H), 2.53
1-Methyl-1,2,9,9a-tetrahydro-3H-fluoren-3-one (Table 3, entry (t, J = 8.0, 2H), 2.39 (t, J = 7.4, 2H), 2.02 (p, J = 4.0, 2H),
23). Prepared from 1-indanone (0.132 g, 1.00 mmol) and 1.66–1.54 (m, 2H), 0.91 (t, J = 7.4, 3H). 13C NMR (101 MHz,
3-penten-2-ol (0.172 g, 2 mmol). After purification by column CDCl3) δ = 210.99, 200.00, 136.97, 133.21, 128.75, 128.20,
chromatography, the compound was isolated as a yellow gel 77.48, 77.16, 76.84, 44.91, 41.78, 37.66, 18.44, 17.45, 13.90.
(0.0495 g, 25%). 1H NMR (400 MHz, CDCl3) δ = 7.59 (d, J = 7.7, HRMS (ESI): calculated for C14H18O2 ([M + Na]+): 241.1199,
1H), 7.43–7.35 (m, 2H), 7.31 (t, J = 7.5, 1H), 6.33 (s, 1H), 3.30 found: 241.1205.
(dd, J = 15.8, 7.7, 1H), 2.87–2.78 (m, 1H), 2.73 (dd, J = 15.8, 6.8,
1-(4-(tert-Butyl)phenyl)octane-1,5-dione (Table 4, entry 28).
1H), 2.24–2.04 (m, 2H), 1.18 (d, J = 6.4, 3H). 13C NMR Prepared from 4′-tert-butylacetophenone (0.176 g, 1.00 mmol)
(101 MHz, CDCl3) δ = 200.37, 148.06, 138.37, 131.91, 127.54, and 1-hexen-3-ol (0.200 g, 2.00 mmol). After purification by
125.76, 123.13, 117.49, 100.07, 49.22, 46.90, 36.96, 35.95, column chromatography, the compound was isolated as color-
29.85, 20.11. HRMS (ESI): calculated for C14H14O ([M + Na]+): less oil (0.118 g, 43%). 1H NMR (400 MHz, CDCl3) δ = 7.90 (d, J
221.0937, found: 221.0939.
= 8.8, 2H), 7.47 (d, J = 8.8, 2H), 2.98 (t, J = 8.0, 2H), 2.52 (t, J =
8.0, 2H), 2.38 (t, J = 8.0, 2H), 2.02 (p, J = 8.0, 2H), 1.65–1.22 (m,
2H), 1.34 (s, 9H), 0.91 (t, J = 8.0, 3H). 13C NMR (101 MHz,
Characterisation data for diketone compounds
2-Methyl-1-phenyloctane-1,5-dione (Table 4, entry 24). CDCl3) δ = 211.02, 199.70, 156.94, 139.26, 134.41, 128.18,
Prepared from propiophenone (0.134 g, 1.00 mmol) and 125.68, 44.90, 41.84, 37.57, 35.25, 31.23, 18.56, 17.45, 13.90.
1-hexen-3-ol (0.200 g, 2.00 mmol). After purification by column HRMS (ESI): calculated for C18H26O2 ([M + Na]+): 297.1825,
chromatography, the compound was isolated as a yellow liquid found: 297.1818.
(0.135 g, 58%). 1H NMR (400 MHz, CDCl3) δ = 7.98–7.91 (m,
1-(4-Methoxyphenyl)-2-methyloctane-1,5-dione (Table 4,
2H), 7.53–7.49 (m, 1H), 7.44–7.41 (m, 2H), 3.52 (sext, J = 8.0, entry 29). Prepared from 4′-methoxypropiophenone (0.164 g,
1H), 2.49–2.41 (m, 1H), 2.38–2.23 (m, 3H), 2.08–1.99 (m, 1H), 1.00 mmol) and 1-hexen-3-ol (0.200 g, 2.00 mmol). After purifi-
1.78–1.66 (m, 1H), 1.52 (sext, J = 8.0, 2H), 1.15 (d, J = 8.0, 3H), cation by column chromatography, the compound was isolated
0.85 (t, J = 8.0, 3H). 13C NMR (101 MHz, CDCl3) δ 210.70, as a colorless oil (0.107 g, 41%). 1H NMR (400 MHz, CDCl3) δ =
203.87, 136.42, 133.03, 128.68, 128.31, 77.40, 77.08, 76.77, 7.95 (d, J = 8.8, 2H), 6.93 (d, J = 8.0, 2H), 3.86 (s, 3H), 3.50
44.74, 39.82, 39.49, 27.17, 17.43, 17.26, 13.70. HRMS (ESI): cal- (sext, J = 8.0, 1H), 2.51–2.43 (m, 1H), 2.38–2.30 (m, 2H),
culated for C15H20O2 ([M + Na]+): 255.1356, found: 255.1365.
2.09–2.00 (m, 2H), 1.76–1.68 (m, 1H), 1.55 (sext, J = 8.0, 2H),
2-Ethyl-1-phenyloctane-1,5-dione (Table 4, entry 25). 1.15 (d, J = 8.0, 3H), 0.87 (t, J = 8.0, 3H). 13C NMR (101 MHz,
Prepared from butyrophenone (0.148 g, 1.00 mmol) and CDCl3) δ = 210.82, 202.40, 163.50, 130.62, 129.40, 113.83,
1-hexen-3-ol (0.200 g, 2.00 mmol). After purification by column 55.45, 44.73, 39.90, 39.08, 27.39, 17.59, 17.28, 13.72. HRMS
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(ESI): calculated for C16H22O3 ([M + H]+): 263.1642, found: molecular sieves were added to the reaction mixture and
263.1611. stirred at room temperature for 24 hours. Then the reaction
1-(3-Fluorophenyl)octane-1,5-dione (Table 4, entry 30). mixture was evaporated under vacuum and purified by flash
Prepared from 3′-fluoroacetophenone (0.138 g, 1.00 mmol) column chromatography in ethyl acetate and n-hexane (1 : 4) as
and 1-hexen-3-ol (0.200 g, 2.00 mmol). After purification by an eluent. Yield = 1.078 g, (58%).
column chromatography, the compound was isolated as a
colorless oil (0.080 g, 34%). 1H NMR (400 MHz, CDCl3) δ =
7.75–7.73 (m, 1H), 7.65–7.62 (m, 1H), 7.46–7.41 (m, 1H),
7.28–7.23 (m, 1H), 2.99 (t, J = 7.0, 2H), 2.53 (t, J = 7.0, 2H), 2.39
Conflicts of interest
(t, J = 7.0, 2H), 2.01 (p, J = 7.0, 2H), 1.60 (sext, J = 7.0, 2H), 0.91 The authors declare no competing financial interest.
(t, J = 7.0, 3H). 13C NMR (101 MHz, CDCl3) δ = 210.51, 202.30,
163.14 (d, J = 247), 139.03 (d, J = 7), 139.06 (d, J = 7), 124.27,
120.45 (d, J = 21), 115.22 (d, J = 23), 44.96, 44.21, 39.64, 25.44,
Acknowledgements
17.40, 13.84. 19F NMR (376 MHz, CDCl3) δ −111.42. HRMS
(ESI): calculated for C14H17FO2 ([M + Na]+): 259.1105, found: K. V. thanks the Science & Engineering Research Board (SERB)
259.1110.
(EMR/2017/000620), New Delhi and the Department of Atomic
2-Methyl-1,5-diphenylpentane-1,5-dione (Scheme 1C, entry Energy (DAE) for financial support. S. S. thanks DST for an
34).27 Prepared from propiophenone (0.134 g, 1.00 mmol) and INSPIRE fellowship; S. K. M. and P. B. thank CSIR for a
1-phenylprop-2-en-1-ol (0.268 g, 2.00 mmol). The compound research fellowship. The authors also thank the reviewer for
was isolated as a white solid (0.162 g, 61%). 1H NMR the helpful suggestions.
(400 MHz, CDCl3) δ = 8.00–7.98 (m, 2H), 7.94–7.92 (m, 2H),
7.58–7.52 (m, 2H), 7.48–7.42 (m, 3H), 3.66 (sext, J = 7.0, 1H),
3.14–3.06 (m, 1H), 2.95–2.87 (m, 1H), 2.32–2.24 (m, 1H),
Notes and references
1.97–1.89 (m, 1H), 1.25 (d, J = 7.0, 3H). 13C NMR (101 MHz,
CDCl3) δ 204.05, 200.05, 136.94, 136.55, 133.20, 128.84, 128.73,
128.52, 128.19, 39.89, 35.99, 27.87, 17.78. HRMS (ESI): calcu-
lated for C18H18O2 ([M + Na]+): 289.1199, found: 289.1200.
1,5-Diphenylpentane-1,5-dione (Scheme 1C, entry 35).
Prepared from acetophenone (0.120 g, 1.00 mmol) and
α-vinylbenzyl alcohol (0.537 g, 4.00 mmol). After purification
by column chromatography, the compound was isolated as a
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1
white solid (0.108 g, 43%). H NMR (400 MHz, CDCl3) δ = 7.98
(d, J = 7.3, 4H), 7.56 (t, J = 7.4, 02H), 7.46 (t, J = 7.7, 4H), 3.13 (t,
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(ESI): calculated for C17H16O2 ([M + Na]+): 275.1043, found:
275.1024.
2-Ethyl-1,5-diphenylpentane-1,5-dione (Scheme 1C, entry
36). Prepared from butyrophenone (0.148 g, 1.00 mmol) and
α-vinylbenzyl alcohol (0.537 g, 4.00 mmol). After purification
by column chromatography, the compound was isolated as
colorless oil (0.132 g, 47%). 1H NMR (400 MHz, CDCl3). δ =
8.00–7.94 (m, 2H), 7.93–7.86 (m, 2H), 7.57–7.52 (m, 2H),
7.48–7.40 (m, 4H), 3.62–3.49 (m, 1H), 3.10–3.02 (m, 1H),
2.89–2.81 (m, 1H), 2.27–2.17 (m, 1H), 2.07–1.95 (m, 1H),
1.90–1.79 (m, 1H), 1.67–1.50 (m, 1H), 0.92 (t, J = 7.4, 3H). 13C
NMR (101 MHz, CDCl3) δ 11.84, 25.80, 36.08, 46.76, 128.18,
128.41, 128.71, 128.85, 133.18, 136.95, 137.48, 200.11, 204.10.
HRMS (ESI): calculated for C19H20O2 ([M + Na]+): 303.1356,
found: 303.1352.
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