Rh-Catalyzed Decarbonylative Addition of Salicylaldehydes with Vinyl Ketones: Synthesis of Taccabulins A–E

Article abstract of DOI:10.1002/ejoc.201901314

A rhodium-catalyzed decarbonylative addition of salicylaldehydes with vinyl ketones was developed to synthesize o-hydroxydihydrochalcones (2-hydroxyphenethyl ketones). These decarbonylative addition reactions afforded various functionalized o-hydroxydihydrochalcones in moderate to good yields with broad functional group tolerance and selectivity. This method was also applied further in the divergent synthesis of dihydrochalcone derived taccabulins A–E.

Full text of DOI:10.1002/ejoc.201901314

DOI: 10.1002/ejoc.201901314
Full Paper
Decarbonylative Addition
Rh-Catalyzed Decarbonylative Addition of Salicylaldehydes with
Vinyl Ketones: Synthesis of Taccabulins A–E
Maddali L. N. Rao*[a] and Boddu S. Ramakrishna[a]
Abstract: A rhodium-catalyzed decarbonylative addition of tionalized o-hydroxydihydrochalcones in moderate to good
salicylaldehydes with vinyl ketones was developed to synthe- yields with broad functional group tolerance and selectivity.
size o-hydroxydihydrochalcones (2-hydroxyphenethyl ketones). This method was also applied further in the divergent synthesis
These decarbonylative addition reactions afforded various func- of dihydrochalcone derived taccabulins A–E.
Introduction
Dihydrochalcones are valuable synthons possessing several bio-
logical applications.[1] In particular, molecules with o-hydroxydi-
hydrochalcone (HDHC) as a core have been studied in various
biological studies (Scheme 1).[2] Importantly, a family of tacca-
bulins extracted from Tacca species were found to show anti-
proliferative activity against various cancer cell lines.[2a] For in-
stance, taccabulin A possesses microtubule-destabilizing activ-
ity.[2b] The antiproliferative activity of taccabulins A and D in
HeLa cells showed IC50 values of 0.6 μ
tively. Whereas, taccabulins B, C and E exhibited IC50 values
greater than 50 μ in HeLa cells. Further, the structure-activity
M and 28.9 μM respec-
M
relationship studies of taccabulin family indicated improved
antiproliferative activity with dihydrochalcones containing addi-
tional hydroxy group.[2a]
Scheme 2. Salicylaldehydes in the synthesis of o-hydroxydihydrochalcones.
Other methods such as Pd-catalyzed Heck reaction of o-iodo-
phenols with allylic alcohols[4] and C–H alkylation of N-phenox-
yacetamides with allylic alcohols under Rh-catalysis also provide
HDHCs.[5] Thus, synthetic methods with the direct use of salicyl-
aldehydes in the preparation of HDHCs under metal-catalyzed
conditions are rare. There is a dire need to explore for such a
possibility keeping in view the significance of HDHCs.
Simple aldehydes in decarbonylative addition reactions are
known with olefins,[6] while salicylaldehydes react in hydroacyl-
ation process with olefins.[7] However, salicylaldehydes reactiv-
ity in decarbonylative addition reactions are scant.[8] In this
context, we recently reported the decarbonylative coupling of
salicylaldehydes with acrylates and acrylamides to synthesize
functionaly important o-hydroxycinnamates and o-hydroxy-
cinnamamides (Scheme 2b).[9] In literature the competition be-
tween ꢀ-hydride elimination and conjugate addition of alkyl
rhodium intermediates was reported in reaction with acrylates
and vinyl ketones respectively.[10] Thus, vinyl ketones are known
to predominently deliver saturated products while acrylates
gave unsaturated products.[11] Hence, it was of interest to ex-
plore the decarbonylative addition reactivity of salicylaldehydes
Scheme 1. Taccabulin family of natural products.
Taccabulins can be synthesized from the corresponding o-
hydroxychalcones (Scheme 2a).[3] This approach in general, is
problematic as the preparation of o-hydroxychalcones involves
tedius synthetic procedures often with low yields due to the
presence of free phenolic group.[3a] Further, synthesis of o-
hydroxydihydrochalcones with direct use of salicylaldehydes
was also reported with protection/deprotection synthetic ma-
noeuvring to obtain improved yields.[3]
[a] Department of Chemistry, Indian Institute of Technology Kanpur,
Kanpur 208016, India
E-mail: maddali@iitk.ac.in
http://www.iitk.ac.in
Supporting information and ORCID(s) from the author(s) for this article are
available on the WWW under https://doi.org/10.1002/ejoc.201901314.
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with vinyl ketones under rhodium catalysis and its possible ap- results are given in Table 2. From this study, it was clear that
plication in the synthesis of taccabulin natural products con- the desired decarbonylative addition underwent smoothly with
taining HDHCs. This attempt provided an opportunity for the electronically different salicylaldehydes 1a–1e in reaction with
direct synthesis of o-hydroxydihydrochalcones from salicylalde- vinyl ketone 2a delivering the corresponding HDHCs (3a–3e) in
hydes and vinyl ketones under Rh-catalyzed conditions moderate yields along with 4 as a minor side product in some
(Scheme 2c). Further the developed method was also applied cases.
in the synthesis of taccabulin natural products as elaborated
below.
Table 2. Scope of functionalized salicylaldehydes and vinyl ketones.[a]
Results and Discussion
The coupling of salicylaldehyde 1a with phenyl vinyl ketone
2a (4 equiv.) was investigated (Table 1) initially with catalytic
Rh(CO)2(acac) in DMF at 120 °C for 3 h (entry 1). This resulted
in the formation of o-hydroxydihydrochalcone 3a in 53 % yield
along with 4a as a side product in 25 % yield (entry 1). Evi-
dently, product 4a arose from 3a through carbonylative Michael
addition[12] involving vinyl ketone 2a. With the aim to improve
the yield of 3a, this reaction was further done with reduced
amounts of 2a (cf. entry 2 and 3). To some extent this helped
in improving the yield of 3a up to 61 % with the use of 2 equiv.
of vinyl ketone (entry 2). Further optimization with different
Rh-catalysts and solvent conditions did not improve the yield
(entries 4–8). Lowering the reaction temperature also gave poor
yield (entry 9). Thus, from this optimization study, the protocol
comprising phenyl vinyl ketone (2 equiv.), Rh(CO)2(acac)
(0.05 equiv.) in DMF at 120 °C for 3 h proved to be more effi-
cient and it was considered as an optimal one for our further
study (entry 2).
Table 1. Optimization studies.[a]
Entry
Catalyst
Solvent
3a [%]
4a [%]
1
2
3
4
5
6
7
8
9
Rh(CO)2(acac)
Rh(CO)2(acac)
Rh(CO)2(acac)
RhCl3/PPh3
DMF
DMF
DMF
DMF
DMF
DMF
DMA
NMP
DMF
53
61
46
20
33
37
39
46
28
25[b]
21
21[c]
9
RhCl(PPh3)3
17
8
16
RhCl(CO)(PPh3)2
Rh(CO)2(acac)
Rh(CO)2(acac)
Rh(CO)2(acac)
16
30[d]
[a] Conditions: 1a (0.5 mmol, 1 equiv.), 2a (1 mmol, 2 equiv.), catalyst
(0.025 mmol, 0.05 equiv.), solvent (2 mL), 120 °C, 3 h. [b] 2a (2 mmol, 4 equiv.).
[c] 2a (0.5 mmol, 1 equiv.). [d] Reaction was carried out at 100 °C.
[a] Conditions: 1a–1g (0.5 mmol, 1 equiv.), 2a–2g (1 mmol, 2 equiv.),
Rh(CO)2(acac) (0.025 mmol, 0.05 equiv.), DMF (2 mL), 120 °C, 3 h.
The above study thus established the direct synthesis of o-
The couplings of the functionalized aryl vinyl ketones (2b–
hydroxydihydrochalcone (HDHC) from readily available salicyl- 2e) with different salicylaldehydes (1a–c and 1f) also furnished
aldehyde and vinyl ketone under Rh-catalyzed conditions. Addi- the corresponding HDHCs (3f–3l) in moderate to good yields.
tionally, this method ensured protecting-group free coupling Further couplings using aliphatic variant such as methyl vinyl
and direct utilization of vinyl ketones as reactant. With these ketone 2f with salicylaldehydes (1e and 1g) also gave the corre-
advantages in hand, further exploration for general reactivity sponding functionalized HDHCs (3m and 3n) in good yields.
was explored.
Additional curiosity check was carried out with styryl vinyl
First the optimized Rh-catalyzed conditions was tested with ketone 2g in combination with functionalized salicylaldehydes
various functionalized salicylaldehydes and vinyl ketones. These 1b, 1c and 1g. In these cases, the respective functionaly loaded
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(E)-5-(2-hydroxyphenyl)-1-phenylpent-1-en-3-ones
(3o–3q) vinyl ketones 2i and 2j gave intermediates 5c and 5d which
were obtained in moderate yields. The direct synthesis of these are precursors for taccabulins A and E in 62 % and 68 % yields
multifunctional products in a one-pot operation involving de- respectively. Importantly, taccabulin C is also a precursor for
carbonylative addition is synthetically advantageous process. taccabulin D. Evidently the present Rh-catalyzed protocol thus
Importantly, the product 3p is known for its antiproliferative smoothly afforded these different intermediates required for
activity,[2c] and it was earlier synthesized from benzaldehyde the synthesis of the taccabulins A–E in a synthetically viable
involving multi-step sequence.[13] Importantly, the present de- and advantage manner (Scheme 4).
carbonylative addition of salicylaldehydes to vinyl ketones has
hitherto not been reported in the literature. It is to be noted
that in most cases, the side product 4 (4a, 4b, 4f, 4g, 4i–k, 4o
and 4p) was formed in minor amount as carbonylative Michael
addition[12] of product 3 with vinyl ketone (2).
Further, o-hydroxydihydrochalcone 5a was first methylated
to obtain taccabulin B in 78 % yield (Equation 4.1, Scheme 4).
Synthesis of taccabulin A and D required the protection and
deprotection sequence to achieve the selective methylations.
The selective acetylation of taccabulin C (5b) was initially car-
To demonstrate synthetic application of the present protocol, ried out to obtain monoacetylated product 5f in 73 % yield. It
we considered the preparation of taccabulins A–E that are was then methylated followed by deacetylation to afford tacca-
known for their numerable biological activities.[2] A concise plan bulin D (5g) in 80 % combined yield (Equation 4.2, Scheme 4).
was envisaged for the preparation of taccabulins A–E with Similarly, selective acetylation of o-hydroxydihydrochalcone 5c
salicylaldehydes (1h and 1i) in combination with vinyl ketones afforded monoacetylated product 5h in 86 % yield. Further
(2h, 2i and 2j).
methylation and deacetylation sequence gave taccabulin A (5i)
in 72 % combined yield (Equation 4.3, Scheme 4). Additionally,
taccabulin E (5k) was obtained from o-hydroxydihydrochalcone
5d involving methylation (5j) and reduction protocol in 80 %
yield (Equation 4.4, Scheme 4). Overall, these efforts thus
demonstrated a facile synthetic procedure for the synthesis of
o-hydroxydihydrochalcones containing taccabulin (A–E) natural
products. The selective monoacetylation strategy adopted in
the synthesis of taccabulin A and D enriched the overall syn-
thetic yields in a concise manner.
Accordingly, the first synthetic application was started with
the synthesis of taccabulin C employing salicylaldehyde 1i and
vinyl ketone 2h under Rh-catalyzed conditions (Scheme 3). Our
method thus proved to be very useful as the desired coupling
underwent smoothly without protection of the phenolic group
in salicylaldehyde 1i and vinyl ketone 2h.[3] This directly af-
forded taccabulin C (5b) in 62 % yield. The key intermediates
5a, 5c and 5d required for the synthesis of other taccabulins
were also synthesized in 62–69 % yields similary using salicyl-
aldehydes 1h and 1i with vinyl ketones 2h–2j. Clearly the
To gain insights into the reaction mechanism a few control
present protocol further demonstrated the tolerance for o-ster- reactions were carried out as given in Scheme 5. First, the role
ics as in 1h and 1i. In elaboration, the reaction of salicylalde- of the hydroxy group was investigated with benzaldehyde and
hyde 1h with vinyl ketone 2h afforded 5a, a precursor for tacca- 2-methoxybenzaldehyde (Scheme 5a). In these cases, the corre-
bulin B, in 69 % yield. Reactions of salicylaldehyde 1i with the sponding dihydrochalcones were not formed and starting alde-
Scheme 3. Synthesis of taccabulin C and other key intermediates.
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Scheme 4. Synthesis of taccabulin natural products.
Scheme 5. Mechanistic study.
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Scheme 6. Proposed mechanistic cycle.
hydes were recovered. This indicates the necessity of the preformed product 3 in ligand exchange with 6a giving the
presence of hydroxy group. Further, the reaction of partially intermediate 6f followed by its Michael addition[12] to vinyl ket-
deuterated salicylaldehyde (d-1a) with vinyl ketone 2a gave one generating 6g. This upon protonation involving salicylalde-
o-hydroxydihydrochalcone (3a) in 56 % yield along with 4a in hyde forms product 4. The formation of mono-deuterated prod-
16 % yield (Scheme 5b) without incorporation of deuterium in uct (d1-3a) and di-deuterated product (d2-4a) confirms the for-
the products. This shows that aldehydic proton is not involved mation of product 4 with the involvement of preformed prod-
for protonation during the catalytic cycle and the absence uct 3 as proposed in the catalytic cycle. The proposed carbonyl-
of H/D exchange between aldehyde and phenol during the re- ation in the formation of 6g also further confirms the initial
action course. Importantly, deuterium exchange between phen- decarbonylation step during the formation of 6c.
olic group of salicylaldehyde and CD3OD was known to give
salicylaldehyde with deuterium incorporation at phenolic
group.[14] This was proven with the reaction of salicylaldehyde
(1a) with vinyl ketone (2a) in DMF/CD3OD solvent mixture
(Scheme 5c) delivering mono-deuterated product (d1-3a) in
51 % yield along with di-deuterated product (d2-4a) in 10 %
yield. Additional two control experiments with product 3a us-
ing DMF/CD3OD solvent combination without (Scheme 5d) and
with Rh-catalyst (Scheme 5e) also delivered partial deuterium
exchange at alfa carbon of carbonyl group confirming the pos-
sibility of acidic proton exchange after the product formation.
However, the mono-deuterations in equal proportion found
both in products 3 and 4 (Scheme 5c) clearly indicates their
direct formation through catalytic cycle and not after acidic pro-
ton exchange (as seen in Scheme 5d and Scheme 5e).
Conclusions
In conclusion, we have developed a simple and straight forward
catalytic method for the decarbonylative addition of salicylalde-
hydes to vinyl ketones for the synthesis of o-hydroxydihydro-
chalcones. This protecting-group free and step-economic
method provides the direct preparation of o-hydroxydihydro-
chalcones in moderate to good yields. This method was further
applied in the Rh-catalyzed first time synthesis of the taccabulin
natural products which are important scaffolds with antiprolif-
erative activity against various cancer cell lines and other bio-
logical activities.
Based on the above experimentation, the probable mecha-
nistic cycle for the formation of product (3) along with minor
product (4) is given in Scheme 6. The initial ligand exchange of
the rhodium catalyst with salicylaldehyde (1) would form the
aryloxyrhodium 6a. It undergoes oxidative addition to give the
aroylrhodium hydride intermediate 6b followed by decarbonyl-
ation gives arylrhodium hydride 6c. This in turn undergoes in-
sertion of vinyl ketone (2) generates alkylrhodium 6d which
upon reductive elimination provides 6e/6e′. Further protona-
tion involving salicylaldehyde provides product o-hydroxydi-
hydrochalcone 3 with the regeneration of 6a. The formation of
Experimental Section
General: All the NMR (1H and 13C) spectra were recorded on a JEOL-
Lambda (400 MHz and 500 MHz) spectrometer in CDCl3 solvent. IR
spectra were recorded with a Perkin-Elmer FT/IR spectrometer.
HRMS spectra were recorded with a Waters GCT Premier-CAB155
and Waters-Q-Tof Premier-HAB213 instruments. Melting points were
determined using a Yamato melting point apparatus. All the cou-
pling reactions were performed in dry Schlenk tube under nitrogen
atmosphere conditions. Standard procedures were followed to dry
various solvents used in coupling reactions. Methyl vinyl ketone (2f)
was purchased commercially and used without further purification.
minor product 4 could be due to the further involvement of Salicylaldehyde (1a), 5-bromosalicylaldehyde (1d) and 2-hydroxy-1-
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naphthaldehyde (1f) were purchased from commercial suppliers.
The other substituted salicylaldehydes (1b,[15a] 1c,[15a] 1e,[15b]
1g,[15c] 1h,[15d] 1i[15d] and d-1a[7b]) were prepared by known proce-
dures.
7.54 (m, 2H), 7.18 (dd, J = 17.0, 10.6 Hz, 1H), 6.96 (d, J = 8.0 Hz, 1H),
6.43 (dd, J = 17.0, 1.8 Hz, 1H), 5.87 (dd, J = 10.5, 1.8 Hz, 1H), 5.56
(s, 1H), 3.95 (s, 3H) ppm. 13C NMR (100 MHz, CDCl3): δ = 189.3, 150.7,
147.0, 132.0, 130.2, 129.4, 124.2, 114.0, 110.6, 56.2 ppm. IR (KBr): ν =
˜
3378, 2936, 1659, 1588, 1515, 1464, 1427, 1275, 1201, 1172, 1024,
785 cm–1. HRMS (EI+): calcd. for C10H10O3 [M]+ 178.0630, found
178.0638.
General procedure for the synthesis of vinyl ketones (2): The
substituted aryl vinyl ketones were prepared from the correspond-
ing acetophenones by α-methylenation of carbonyls known in liter-
ature.[16] In an oven-dried 150 mL R.B flask, acetophenone was
taken in dry THF and paraformaldehyde (2 equiv.), diisopropyl-
ammonium 2,2,2-trifluoroacetate (1 equiv.), TFA (50 mol-%) were
added. The reaction mixture was stirred at reflux for 2 h in an open
atmosphere. The mixture will become clear, then the reaction mix-
ture is cooled down to room temperature and paraformaldehyde
(2 equiv.) was added. Next, the reaction mixture was stirred at reflux
for an additional 16 h. The reaction mixture was cooled to r.t. and
the solvent was removed under reduced pressure, extracted with
1-(3-Hydroxy-4-methoxyphenyl)prop-2-en-1-one (2i): Colourless
liquid (0.18 g, 33 %). 1H NMR (400 MHz, CDCl3): δ = 7.58–7.54 (m,
2H), 7.15 (dd, J = 17.0, 10.5 Hz, 1H), 6.91 (d, J = 8.9 Hz, 1H), 6.42
(dd, J = 17.0, 1.8 Hz, 1H), 5.87 (dd, J = 10.5, 1.8 Hz, 1H), 5.72 (s, 1H),
3.97 (s, 3H) ppm. 13C NMR (100 MHz, CDCl3): δ = 189.5, 150.8, 145.7,
132.1, 131.1, 129.6, 122.5, 114.9, 110.1, 56.2 ppm. IR (KBr): ν = 3393,
˜
2939, 2844, 1660, 1611, 1582, 1513, 1440, 1276, 1176, 1017, 890,
782 cm–1. HRMS (ESI+): calcd. for C10H11O3 [M + H]+ 179.0708, found
179.0702.
DCM and washed with 1
N HCl, 1 N NaOH and brine solution. The
1-(Benzo[d][1,3]dioxol-5-yl)prop-2-en-1-one (2j):[18c] Colourless
liquid (0.42 g, 19 %). 1H NMR (400 MHz, CDCl3): δ = 7.56 (dd, J =
8.2, 1.6 Hz, 1H), 7.46 (d, J = 1.7 Hz, 1H), 7.12 (dd, J = 17.2, 10.7 Hz,
1H), 6.86 (d, J = 8.2 Hz, 1H), 6.41 (dd, J = 17.2, 1.8 Hz, 1H), 6.05 (s,
2H), 5.87 (dd, J = 10.7, 1.7 Hz, 1H) ppm. 13C NMR (100 MHz, CDCl3):
δ = 189.0, 152.0, 148.4, 132.2, 129.6, 125.2, 108.6, 108.1, 102.0 ppm.
organic contents were dried with anhydrous MgSO4 and the sol-
vents evaporated to dryness. The crude was purified by silica gel
column chromatography.
The characterization data for vinyl ketones (2a–2e and 2g–2j) is
given below.
IR (KBr): ν = 3080, 2906, 1666, 1600, 1445, 1253, 1038, 779 cm–1
.
˜
1-Phenylprop-2-en-1-one (2a):[16] Colourless liquid (2.4 g, 44 %).
1H NMR (400 MHz, CDCl3): δ = 7.96–7.94 (m, 2H), 7.60–7.55 (m, 1H),
7.50–7.46 (m, 2H), 7.16 (dd, J = 17.1, 10.6 Hz, 1H), 6.44 (dd, J = 17.1,
1.7 Hz, 1H), 5.93 (dd, J = 10.6, 1.7 Hz, 1H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 191.2, 137.4, 133.1, 132.5, 130.4, 128.8, 128.8 ppm.
HRMS (ESI+): calcd. for C10H9O3 [M + H]+ 177.0552, found 177.0558.
Representative procedure for decarbonylative addition reac-
tions: The decarbonylative addition reaction was performed by
charging a dry Schlenk tube with salicylaldehyde (1a) (61 mg,
0.5 mmol), phenyl vinyl ketone (2a) (132 mg,
1 mmol),
1-p-Tolylprop-2-en-1-one (2b):[17a] Colourless liquid (3.3 g, 60 %).
1H NMR (400 MHz, CDCl3): δ = 7.86 (d, J = 8.2 Hz, 2H), 7.28 (dd, J =
8.6, 0.6 Hz, 2H), 7.16 (dd, J = 17.1, 10.6 Hz, 1H), 6.43 (dd, J = 17.1,
1.8 Hz, 1H), 5.90 (dd, J = 10.6, 1.8 Hz, 1H), 2.42 (s, 3H) ppm. 13C
NMR (100 MHz, CDCl3): δ = 190.7, 144.0, 134.9, 132.5, 129.9, 129.5,
129.0, 21.8 ppm.
1-(4-Methoxyphenyl)prop-2-en-1-one (2c):[17b] Colourless liquid
(2.3 g, 42 %). 1H NMR (400 MHz, CDCl3): δ = 7.96 (d, J = 9.0 Hz, 2H),
7.17 (dd, J = 17.1, 10.5 Hz, 1H), 6.96 (d, J = 9.0 Hz, 2H), 6.42 (dd, J =
17.1, 1.8 Hz, 1H), 5.87 (dd, J = 10.5, 1.8 Hz, 1H), 3.87 (s, 3H) ppm.
13C NMR (125 MHz, CDCl3): δ = 189.4, 163.7, 132.3, 131.2, 130.4,
129.4, 114.0, 55.6 ppm.
1-(4-Chlorophenyl)prop-2-en-1-one (2d):[18a] Colourless liquid
(3.16 g, 58 %). 1H NMR (400 MHz, CDCl3): δ = 7.88 (d, J = 8.7 Hz,
2H), 7.45 (d, J = 8.7 Hz, 2H), 7.11 (dd, J = 17.1, 10.6 Hz, 1H), 6.44
(dd, J = 17.1, 1.6 Hz, 1H), 5.94 (dd, J = 10.6, 1.6 Hz, 1H) ppm. 13C
NMR (100 MHz, CDCl3): δ = 189.9, 139.6, 135.7, 132.1, 130.8, 130.2,
129.1 ppm.
Rh(CO)2(acac) (6.4 mg, 0.025 mmol) and DMF (2 mL) solvent. This
mixture was stirred in an oil bath at 120 °C for 3 h. In the end, the
contents were brought to r.t., quenched with dil. HCl and extracted
with ethyl acetate (30 mL). The organic extract was washed with
water (15 mL), brine (15 mL), dried with anhydrous MgSO4 and
concentrated. The crude product was purified by silica gel column
chromatography using ethyl acetate/hexane as an eluent. The prod-
uct 3a and 4a were obtained in 61 % (69 mg) and 21 % (40 mg)
respectively.
The characterization data of all the products is given below.
3-(2-Hydroxyphenyl)-1-phenylpropan-1-one (3a):[19] Colourless
1
solid (69 mg, 61 %), m.p. 86–88 °C. H NMR (400 MHz, CDCl3): δ =
7.99–7.96 (m, 2H), 7.60–7.55 (m, 1H), 7.47–7.42 (m, 2H), 7.14–7.09
(m, 2H), 6.93–6.84 (m, 2H), 3.47–3.43 (m, 2H), 3.06–3.03 (m, 2H) ppm.
13C NMR (100 MHz, CDCl3): δ = 202.2, 154.6, 136.2, 133.9, 130.7,
128.8, 128.5, 128.1, 127.9, 120.8, 117.6, 40.5, 23.5 ppm. IR (KBr): ν =
˜
3355, 3064, 2926, 1670, 1596, 1490, 1449, 1365, 1235, 1207, 1098,
754, 741, 688 cm–1. HRMS (ESI+): calcd. for C15H15O2 [M + H]+
227.1072, found 227.1075.
1-(Naphthalen-2-yl)prop-2-en-1-one (2e):[17b] Colourless liquid
1
(1.41 g, 26 %). H NMR (400 MHz, CDCl3): δ = 8.47 (s, 1H), 8.04 (dd,
3-(2-Hydroxy-5-methylphenyl)-1-phenylpropan-1-one (3b): Col-
ourless liquid (62 mg, 52 %). 1H NMR (400 MHz, CDCl3): δ = 7.98
(dd, J = 8.5, 1.3 Hz, 2H), 7.59–7.54 (m, 1H), 7.47–7.42 (m, 2H), 6.93–
6.89 (m, 2H), 6.82 (d, J = 8.0 Hz, 1H), 3.46–3.42 (m, 2H), 3.02–2.98
(m, 2H), 2.25 (s, 3H) ppm. 13C NMR (100 MHz, CDCl3): δ = 202.1,
152.3, 136.2, 133.9, 131.2, 129.9, 128.8, 128.6, 128.5, 127.6, 117.4,
J = 8.6, 1.8 Hz, 1H), 7.98–7.88 (m, 3H), 7.63–7.54 (m, 2H), 7.33 (dd,
J = 17.1, 10.6 Hz, 1H), 6.51 (dd, J = 17.1, 1.7 Hz, 1H), 5.98 (dd, J =
10.6, 1.7 Hz, 1H) ppm. 13C NMR (100 MHz, CDCl3): δ = 191.0, 135.7,
134.7, 132.6, 132.5, 130.5, 130.2, 129.7, 128.7, 128.6, 127.9, 127.0,
124.6 ppm.
(E)-1-Phenylpenta-1,4-dien-3-one (2g):[16] Colourless liquid
40.6, 23.5, 20.6 ppm. IR (KBr): ν = 3354, 3060, 2924, 1671, 1597,
˜
1
1504, 1449, 1363, 1262, 1206, 1110, 815, 759, 689 cm–1. HRMS (ESI+):
calcd. for C16H17O2 [M + H]+ 241.1229, found 241.1234.
(1.68 g, 31 %). H NMR (400 MHz, CDCl3): δ = 7.68 (d, J = 16.0 Hz,
1H), 7.60–7.57 (m, 2H), 7.41–7.40 (m, 3H), 7.01 (d, J = 16.0 Hz, 1H),
6.72 (dd, J = 17.4, 10.6 Hz, 1H), 6.39 (dd, J = 17.4, 1.2 Hz, 1H), 5.89
(dd, J = 10.6, 1.2 Hz, 1H) ppm. 13C NMR (100 MHz, CDCl3): δ = 189.7,
144.1, 135.6, 134.7, 130.7, 129.1, 128.7, 128.5, 124.2 ppm.
1-(4-Hydroxy-3-methoxyphenyl)prop-2-en-1-one (2h):[18b] Col-
ourless liquid (2.65 g, 49 %). 1H NMR (400 MHz, CDCl3): δ = 7.57–
3-(5-Fluoro-2-hydroxyphenyl)-1-phenylpropan-1-one (3c): Col-
ourless solid (73 mg, 59 %), m.p. 86–88 °C. 1H NMR (400 MHz,
CDCl3): δ = 7.98 (d, J = 8.1 Hz, 2H), 7.86 (s, 1H), 7.59 (t, J = 7.3 Hz,
1H), 7.46 (t, J = 7.7 Hz, 2H), 6.87–6.77 (m, 3H), 3.47–3.43 (m, 2H),
3.03–2.99 (m, 2H) ppm. 13C NMR (100 MHz, CDCl3): δ = 201.92,
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157.17 (d, JC-F = 239.0 Hz), 150.65, 136.05, 134.11, 129.29 (d, JC-F
6.9 Hz), 128.87, 128.50, 118.67 (d, JC-F = 8.3 Hz), 116.51 (d, JC-F
=
=
1401, 1267, 1235, 1093, 1013, 832, 755 cm–1. HRMS (EI+): calcd. for
C15H13ClO2 [M]+ 260.0604, found 260.0608.
22.5 Hz), 114.44 (d, JC-F = 22.8 Hz), 40.39, 23.54 ppm. IR (KBr): ν =
˜
1-(4-Chlorophenyl)-3-(2-hydroxy-5-methylphenyl)propan-1-one
(3j): Colourless solid (66 mg, 48 %), m.p. 68–70 °C. 1H NMR
(400 MHz, CDCl3): δ = 7.92–7.89 (m, 2H), 7.43–7.39 (m, 2H), 6.91 (d,
J = 7.4 Hz, 2H), 6.80 (d, J = 8.5 Hz, 1H), 3.40–3.37 (m, 2H), 3.01–2.97
(m, 2H), 2.24 (s, 3H) ppm. 13C NMR (100 MHz, CDCl3): δ = 200.7,
152.2, 140.3, 134.6, 131.2, 130.0, 129.8, 129.1, 128.6, 127.4, 117.3,
3346, 3063, 1671, 1598, 1509, 1498, 1449, 1364, 1243, 1206, 1185,
971, 813, 759, 688 cm–1. HRMS (EI+): calcd. for C15H13FO2 [M]+
244.0900, found 244.0900.
3-(5-Bromo-2-hydroxyphenyl)-1-phenylpropan-1-one (3d): Col-
ourless solid (82 mg, 54 %), m.p. 93–95 °C. 1H NMR (400 MHz,
CDCl3): δ = 8.20 (s, 1H), 7.99–7.96 (m, 2H), 7.59 (t, J = 7.4 Hz, 1H),
7.48–7.44 (m, 2H), 7.24–7.18 (m, 2H), 6.80 (d, J = 8.6 Hz, 1H), 3.47–
3.44 (m, 2H), 3.01–2.97 (m, 2H) ppm. 13C NMR (100 MHz, CDCl3):
δ = 202.1, 154.0, 135.9, 134.2, 133.2, 131.0, 130.2, 128.9, 128.5, 119.7,
40.5, 23.6, 20.6 ppm. IR (KBr): ν = 3362, 2924, 1672, 1589, 1503,
˜
1401, 1263, 1205, 1092, 1013, 960, 817 cm–1. HRMS (EI+): calcd. for
C16H15ClO2 [M]+ 274.0761, found 274.0760.
1-(4-Chlorophenyl)-3-(5-fluoro-2-hydroxyphenyl)propan-1-one
(3k): Colourless solid (75 mg, 54 %), m.p. 104–106 °C. 1H NMR
(400 MHz, CDCl3): δ = 7.93–7.90 (m, 2H), 7.65 (s, 1H), 7.45–7.42 (m,
2H), 6.87–6.77 (m, 3H), 3.43–3.39 (m, 2H), 3.02–2.98 (m, 2H) ppm.
13C NMR (100 MHz, CDCl3): δ = 200.60, 157.18 (d, JC-F = 236.5 Hz),
150.52, 140.62, 134.39, 129.88, 129.21, 129.06 (d, JC-F = 7.1 Hz),
112.6, 40.5, 23.3 ppm. IR (KBr): ν = 3346, 2934, 1670, 1596, 1493,
˜
1448, 1362, 1271, 1235, 1208, 1111, 815, 743, 687 cm–1. HRMS (EI+):
calcd. for C15H13BrO2 [M]+ 304.0099, found 304.0092.
3-(5-Acetyl-2-hydroxyphenyl)-1-phenylpropan-1-one (3e): Col-
ourless solid (72 mg, 54 %), m.p. 132–134 °C. 1H NMR (400 MHz,
CDCl3): δ = 8.87 (s, 1H), 8.00–7.97 (m, 2H), 7.82 (d, J = 2.2 Hz, 1H),
7.74 (dd, J = 8.4, 2.3 Hz, 1H), 7.59 (t, J = 7.5 Hz, 1H), 7.46 (t, J =
7.8 Hz, 2H), 6.95 (d, J = 8.4 Hz, 1H), 3.51–3.47 (m, 2H), 3.09–3.05 (m,
2H), 2.53 (s, 3H) ppm. 13C NMR (100 MHz, CDCl3): δ = 202.6, 197.3,
159.7, 135.8, 134.3, 131.7, 130.3, 129.6, 128.9, 128.6, 127.9, 117.5,
118.56 (d, JC-F = 8.0 Hz), 116.54 (d, JC-F = 22.5 Hz), 114.50 (d, JC-F
=
22.4 Hz), 40.29, 23.57 ppm. IR (KBr): ν = 3374, 2917, 2849, 1673,
˜
1589, 1497, 1401, 1265, 1203, 1092, 1013, 819, 739 cm–1. HRMS (EI+):
calcd. for C15H12ClFO2 [M]+ 278.0510, found 278.0518.
3-(2-Hydroxyphenyl)-1-(naphthalen-2-yl)propan-1-one (3l): Col-
ourless solid (79 mg, 57 %), m.p. 105–106 °C. 1H NMR (400 MHz,
CDCl3): δ = 8.51 (s, 1H), 8.03 (dd, J = 8.6, 1.8 Hz, 1H), 7.95–7.85 (m,
4H), 7.63–7.53 (m, 2H), 7.17–7.10 (m, 2H), 6.94 (dd, J = 8.1, 1.2 Hz,
1H), 6.87 (td, J = 7.4, 1.3 Hz, 1H), 3.61–3.58 (m, 2H), 3.12–3.09 (m,
2H) ppm. 13C NMR (125 MHz, CDCl3): δ = 202.1, 154.7, 136.0, 133.6,
132.5, 130.8, 130.5, 129.8, 129.0, 128.7, 128.2, 127.9, 127.1, 123.9,
40.5, 26.5, 23.4 ppm. IR (KBr): ν = 3347, 3062, 1760, 1682, 1597,
˜
1449, 1359, 1278, 1208, 1130, 690 cm–1. HRMS (EI+): calcd. for
C17H16O3 [M]+ 268.1099, found 268.1099.
3-(2-Hydroxyphenyl)-1-p-tolylpropan-1-one (3f): Colourless solid
(73 mg, 60 %), m.p. 122–124 °C. 1H NMR (400 MHz, CDCl3): δ = 8.11
(s, 1H), 7.88 (d, J = 8.2 Hz, 2H), 7.24 (d, J = 8.0 Hz, 2H), 7.13–7.09
(m, 2H), 6.93–6.83 (m, 2H), 3.44–3.41 (m, 2H), 3.05–3.01 (m, 2H), 2.40
(s, 3H) ppm. 13C NMR (125 MHz, CDCl3): δ = 201.8, 154.7, 144.9,
133.8, 130.7, 129.5, 128.6, 128.1, 128.0, 120.8, 117.7, 40.5, 23.5,
120.9, 117.6, 40.7, 23.7 ppm. IR (KBr): ν = 3342, 3060, 2934, 1667,
˜
1627, 1594, 1490, 1456, 1372, 1230, 1184, 1125, 862, 822, 755,
475 cm–1. HRMS (ESI+): calcd. for C19H17O2 [M + H]+ 277.1229, found
277.1223.
21.8 ppm. IR (KBr): ν = 3349, 2935, 1667, 1605, 1456, 1361, 1235,
˜
1180, 975, 809, 755 cm–1. HRMS (EI+): calcd. for C16H16O2 [M]+
240.1150, found 240.1150.
4-(5-Acetyl-2-hydroxyphenyl)butan-2-one (3m): Yellow liquid
(75 mg, 73 %). 1H NMR (400 MHz, CDCl3): δ = 7.74–7.71 (m, 3H),
6.93–6.90 (m, 1H), 2.94–2.91 (m, 2H), 2.87–2.83 (m, 2H), 2.53 (s, 3H),
2.19 (s, 3H) ppm. 13C NMR (100 MHz, CDCl3): δ = 212.2, 197.3, 159.6,
131.5, 130.3, 129.6, 127.7, 117.3, 45.2, 29.8, 26.4, 23.3 ppm. IR (KBr):
3-(2-Hydroxyphenyl)-1-(4-methoxyphenyl)propan-1-one (3g):
Yellow solid (79 mg, 62 %), m.p. 58–60 °C. 1H NMR (400 MHz, CDCl3):
δ = 8.29 (s, 1H), 7.96 (d, J = 9.0 Hz, 2H), 7.13–7.08 (m, 2H), 6.93–
6.89 (m, 3H), 6.85 (td, J = 7.4, 1.2 Hz, 1H), 3.86 (s, 3H), 3.42–3.38 (m,
2H), 3.04–3.00 (m, 2H) ppm. 13C NMR (100 MHz, CDCl3): δ = 200.7,
164.2, 154.8, 130.8, 130.7, 129.2, 128.12, 128.06, 120.7, 117.7, 113.9,
ν = 3268, 2999, 2931, 1712, 1672, 1596, 1425, 1360, 1280, 1164,
˜
1116, 1086, 931, 827 cm–1. HRMS (ESI+): calcd. for C12H15O3 [M +
H]+ 207.1021, found 207.1023.
55.6, 40.2, 23.6 ppm. IR (KBr): ν = 3329, 2935, 1656, 1599, 1510,
˜
Methyl 4-hydroxy-3-(3-oxobutyl)benzoate (3n): Colourless solid
(79 mg, 71 %), m.p. 95–96 °C. 1H NMR (400 MHz, CDCl3): δ = 8.42
(s, 1H), 7.81–7.77 (m, 2H), 6.90 (d, J = 8.4 Hz, 1H), 3.86 (s, 3H), 2.95–
2.92 (m, 2H), 2.86–2.84 (m, 2H), 2.19 (s, 3H) ppm. 13C NMR (125 MHz,
CDCl3): δ = 212.2, 167.2, 159.2, 132.8, 130.2, 127.5, 122.6, 117.5, 52.0,
1457, 1261, 1172, 1028, 839, 755 cm–1. HRMS (EI+): calcd. for
C16H16O3 [M]+ 256.1099, found 256.1093.
3-(2-Hydroxynaphthalen-1-yl)-1-(4-methoxyphenyl)propan-1-
one (3h): Colourless solid (105 mg, 68 %), m.p. 128–130 °C. 1H NMR
(400 MHz, CDCl3): δ = 9.16 (s, 1H), 7.95 (d, J = 8.92 Hz, 2H), 7.89 (d,
J = 8.56 Hz, 1H), 7.78 (d, J = 7.92 Hz, 1H), 7.66 (d, J = 8.84 Hz, 1H),
7.54–7.49 (m, 1H), 7.35–7.31 (m, 1H), 7.23 (d, J = 8.8 Hz, 1H), 6.88
(d, J = 8.92 Hz, 2H), 3.84 (s, 3H), 3.59–3.56 (m, 2H), 3.46–3.43 (m,
2H) ppm. 13C NMR (100 MHz, CDCl3): δ = 200.9, 164.3, 152.7, 133.1,
130.9, 129.6, 129.07, 129.05, 128.6, 126.5, 122.9, 122.1, 120.3, 118.9,
45.3, 29.8, 23.2 ppm. IR (KBr): ν = 3358, 3066, 2953, 1704, 1607,
˜
1436, 1358, 1297, 1282, 1247, 1127, 993, 838, 775, 748, 634 cm–1
HRMS (EI+): calcd. for C12H14O4 [M]+ 222.0892, found 222.0897.
.
(E)-5-(2-Hydroxy-5-methylphenyl)-1-phenylpent-1-en-3-one
(3o): Colourless solid (76 mg, 57 %), m.p. 96–98 °C. 1H NMR
(400 MHz, CDCl3): δ = 7.81 (s, 1H), 7.63 (d, J = 16.2 Hz, 1H), 7.54–
7.51 (m, 2H), 7.41–7.38 (m, 3H), 6.92–6.90 (m, 2H), 6.82–6.71 (m, 2H),
3.15–3.12 (m, 2H), 2.94–2.91 (m, 2H), 2.25 (s, 3H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 202.1, 152.3, 144.2, 134.2, 131.1, 131.0, 129.9,
113.9, 55.6, 38.7, 18.6 ppm. IR (KBr): ν = 3241, 2936, 2840, 1656,
˜
1598, 1512, 1250, 1230, 1171, 1027, 817, 749 cm–1. HRMS (ESI+):
calcd. for C20H19O3 [M + H]+ 307.1334, found 307.1333.
129.2, 128.6, 127.7, 125.4, 117.5, 42.9, 23.4, 20.6 ppm. IR (KBr): ν =
˜
1-(4-Chlorophenyl)-3-(2-hydroxyphenyl)propan-1-one (3i): Col-
ourless solid (71 mg, 54 %), m.p. 138–140 °C. 1H NMR (400 MHz,
CDCl3): δ = 7.91 (d, J = 8.6 Hz, 2H), 7.62 (s, 1H), 7.42 (d, J = 8.6 Hz,
2H), 7.13–7.09 (m, 2H), 6.91–6.84 (m, 2H), 3.42–3.38 (m, 2H), 3.05–
3332, 3057, 2919, 1651, 1606, 1504, 1450, 1265, 1090, 976, 738,
690 cm–1. HRMS (EI+): calcd. for C18H18O2 [M]+ 266.1307, found
266.1307.
3.01 (m, 2H) ppm. 13C NMR (100 MHz, CDCl3): δ = 200.8, 154.5, (E)-5-(5-Fluoro-2-hydroxyphenyl)-1-phenylpent-1-en-3-one
140.4, 134.6, 130.7, 129.9, 129.1, 128.2, 127.7, 120.9, 117.5, 40.5,
(3p): Colourless solid (78 mg, 58 %), m.p. 77–79 °C. 1H NMR
(400 MHz, CDCl3): δ = 8.01 (s, 1H), 7.64 (d, J = 16.2 Hz, 1H), 7.54–
23.6 ppm. IR (KBr): ν = 3357, 2917, 2849, 1672, 1589, 1489, 1457,
˜
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7.51 (m, 2H), 7.41–7.37 (m, 3H), 6.88–6.72 (m, 4H), 3.16–3.13 (m, 2H),
25.0 ppm. IR (KBr): ν = 2936, 2840, 1757, 1675, 1601, 1511, 1258,
˜
2.94–2.91 (m, 2H) ppm. 13C NMR (100 MHz, CDCl3): δ = 201.9, 157.1 1212, 1138, 1028, 978, 834 cm–1. HRMS (ESI+): calcd. for C27H26NaO6
(d, JC-F = 236.1 Hz), 150.7 (d, JC-F = 2.2 Hz), 144.6, 134.1, 131.2, 129.3
(d, JC-F = 7.0 Hz), 129.2, 128.7, 125.1, 118.8 (d, JC-F = 8.2 Hz), 116.5
(d, JC-F = 22.3 Hz), 114.5 (d, JC-F = 22.6 Hz), 42.7, 23.5 ppm. IR (KBr):
[M + Na]+ 469.1627, found 469.1629.
2-(3-(4-Chlorophenyl)-3-oxopropyl)phenyl 4-(4-chlorophenyl)-
4-oxobutanoate (4i): Colourless solid (35 mg, 15 %), m.p. 84–86 °C.
1H NMR (400 MHz, CDCl3): δ = 7.89–7.85 (m, 2H), 7.80–7.76 (m, 2H),
7.40–7.36 (m, 4H), 7.30 (dd, J = 7.4, 1.7 Hz, 1H), 7.23 (dd, J = 7.7,
1.9 Hz, 1H), 7.18 (td, J = 7.4, 1.4 Hz, 1H), 7.06 (dd, J = 7.9, 1.3 Hz,
1H), 3.38–3.35 (m, 2H), 3.24–3.19 (m, 2H), 3.05–2.98 (m, 4H) ppm.
ν = 3314, 3061, 1651, 1606, 1495, 1449, 1369, 1191, 976, 813, 750,
˜
689 cm–1. HRMS (EI+): calcd. for C17H15FO2 [M]+ 270.1056, found
270.1057.
(E)-Methyl 4-hydroxy-3-(3-oxo-5-phenylpent-4-enyl)benzoate
(3q): Colourless solid (81 mg, 52 %), m.p. 111–113 °C. 1H NMR 13C NMR (125 MHz, CDCl3): δ = 198.1, 196.6, 171.8, 149.2, 140.0,
(400 MHz, CDCl3): δ = 8.88 (s, 1H), 7.84–7.79 (m, 2H), 7.66 (d, J =
139.6, 135.4, 134.7, 133.4, 130.7, 129.7, 129.5, 129.1, 129.0, 127.7,
16.2 Hz, 1H), 7.54–7.51 (m, 2H), 7.41–7.39 (m, 3H), 6.93 (d, J = 8.4 Hz, 126.5, 122.6, 39.3, 33.5, 28.4, 24.7 ppm. IR (KBr): ν = 3355, 3063,
˜
1H), 6.75 (d, J = 16.2 Hz, 1H), 3.87 (s, 3H), 3.20–3.16 (m, 2H), 2.99–
2918, 1757, 1686, 1590, 1489, 1401, 1208, 1174, 1141, 1092, 1013,
2.96 (m, 2H) ppm. 13C NMR (100 MHz, CDCl3): δ = 202.4, 167.2, 979, 821, 754, 524 cm–1. HRMS (ESI+): calcd. for C25H24Cl2NO4 [M +
159.4, 144.9, 134.0, 132.9, 131.3, 130.2, 129.2, 128.7, 127.7, 125.0, NH4]+ 472.1082, found 472.1082.
122.5, 117.7, 52.0, 42.7, 23.3 ppm. IR (KBr): ν = 3320, 2951, 1713,
˜
2-(3-(4-Chlorophenyl)-3-oxopropyl)-4-methylphenyl 4-(4-chloro-
1688, 1606, 1497, 1449, 1282, 1195, 1116, 977, 772, 690 cm–1. HRMS
phenyl)-4-oxobutanoate (4j): Colourless solid (41 mg, 17 %), m.p.
(EI+): calcd. for C19H18O4 [M]+ 310.1205, found 310.1202.
90–92 °C. 1H NMR (400 MHz, CDCl3): δ = 7.89–7.85 (m, 2H), 7.79–
2-(3-Oxo-3-phenylpropyl)phenyl 4-oxo-4-phenylbutanoate (4a):
Colourless solid (40 mg, 21 %), m.p. 86–88 °C. 1H NMR (400 MHz,
CDCl3): δ = 7.97–7.94 (m, 2H), 7.92–7.89 (m, 2H), 7.57–7.51 (m, 2H),
7.75 (m, 2H), 7.40–7.36 (m, 4H), 7.10 (d, J = 2.0 Hz, 1H), 7.05–7.02
(m, 1H), 6.93 (d, J = 8.2 Hz, 1H), 3.37–3.33 (m, 2H), 3.22–3.18 (m,
2H), 3.00–2.95 (m, 4H), 2.31 (s, 3H) ppm. 13C NMR (125 MHz, CDCl3):
7.44–7.40 (m, 4H), 7.32 (dd, J = 7.4, 1.8 Hz, 1H), 7.23 (dd, J = 7.7, δ = 198.1, 196.6, 172.0, 146.9, 139.9, 139.5, 136.1, 135.4, 134.8, 133.0,
1.9 Hz, 1H), 7.18 (td, J = 7.4, 1.5 Hz, 1H), 7.08 (dd, J = 7.9, 1.4 Hz,
1H), 3.43–3.39 (m, 2H), 3.29–3.25 (m, 2H), 3.06–3.00 (m, 4H) ppm.
13C NMR (100 MHz, CDCl3): δ = 199.3, 197.8, 171.9, 149.2, 137.0,
136.4, 133.6, 133.4, 133.1, 130.7, 128.73, 128.68, 128.24, 128.17,
131.3, 129.7, 129.5, 129.1, 129.0, 128.3, 122.3, 39.4, 33.5, 28.4, 24.7,
21.0 ppm. IR (KBr): ν = 3356, 3061, 2920, 1753, 1686, 1590, 1498,
˜
1401, 1203, 1143, 1092, 1013, 979, 833, 526 cm–1. HRMS (ESI+): calcd.
for C26H26Cl2NO4 [M + NH4]+ 486.1239, found 486.1238.
127.6, 126.4, 122.6, 39.3, 33.6, 28.5, 24.8 ppm. IR (KBr): ν = 3061,
˜
2-(3-(4-Chlorophenyl)-3-oxopropyl)-4-fluorophenyl 4-(4-chloro-
phenyl)-4-oxobutanoate (4k): Brown solid (31 mg, 13 %), m.p. 64–
66 °C. 1H NMR (400 MHz, CDCl3): δ = 7.89–7.85 (m, 2H), 7.79–7.75
(m, 2H), 7.41–7.37 (m, 4H), 7.04–7.00 (m, 2H), 6.95–6.89 (m, 1H),
3.37–3.34 (m, 2H), 3.23–3.19 (m, 2H), 3.03–2.97 (m, 4H) ppm. 13C
2921, 1758, 1685, 1597, 1449, 1361, 1209, 1138, 745, 690 cm–1
.
HRMS (ESI+): calcd. for C25H22NaO4 [M + Na]+ 409.1416, found
409.1411.
4-Methyl-2-(3-oxo-3-phenylpropyl)phenyl 4-oxo-4-phenyl-
butanoate (4b): Colourless solid (49 mg, 24 %), m.p. 86–88 °C. 1H
NMR (400 MHz, CDCl3): δ = 7.97–7.94 (m, 2H), 7.91–7.88 (m, 2H),
NMR (125 MHz, CDCl3): δ = 197.6, 196.6, 171.9, 160.5 (d, JC-F
=
243 Hz), 144.9, 140.0, 139.7, 135.5 (d, JC-F = 7.4 Hz), 135.2, 134.7,
7.56–7.51 (m, 2H), 7.44–7.39 (m, 4H), 7.12 (d, J = 1.8 Hz, 1H), 7.03 129.6, 129.5, 129.1, 129.0, 123.9 (d, JC-F = 8.7 Hz), 117.1 (d, JC-F
=
(dd, J = 8.2, 2.1 Hz, 1H), 6.96 (d, J = 8.2 Hz, 1H), 3.42–3.38 (m, 2H),
3.27–3.23 (m, 2H), 3.02–2.97 (m, 4H), 2.32 (s, 3H) ppm. 13C NMR
(125 MHz, CDCl3): δ = 199.3, 197.8, 172.1, 146.9, 137.0, 136.5, 136.0,
23.0 Hz), 114.3 (d, JC-F = 23.1 Hz), 38.9, 33.5, 28.3, 24.7 ppm. IR (KBr):
ν = 3070, 2921, 1757, 1686, 1590, 1491, 1401, 1206, 1178, 1139,
˜
1092, 980, 831, 792, 527 cm–1. HRMS (ESI+): calcd. for C25H23Cl2FNO4
133.4, 133.1, 131.3, 128.70, 128.65, 128.23, 128.15, 122.3, 39.4, 33.6, [M + NH4]+ 490.0988, found 490.0988.
28.5, 24.7, 21.0 ppm. IR (KBr): ν = 3060, 2921, 1755, 1687, 1597,
˜
(E)-4-Methyl-2-((E)-3-oxo-5-phenylpent-4-enyl)phenyl 4-oxo-6-
1498, 1449, 1360, 1196, 1140, 745, 690 cm–1. HRMS (ESI+): calcd. for
C26H24NaO4 [M + Na]+ 423.1572, found 423.1571.
phenylhex-5-enoate (4o): Colourless solid (41 mg, 18 %), m.p. 88–
1
90 °C. H NMR (500 MHz, CDCl3): δ = 7.60–7.48 (m, 6H), 7.37 (d, J =
2-(3-Oxo-3-p-tolylpropyl)phenyl 4-oxo-4-p-tolylbutanoate (4f):
Colourless solid (20 mg, 10 %), m.p. 86–88 °C. 1H NMR (400 MHz,
CDCl3): δ = 7.85 (d, J = 8.2 Hz, 2H), 7.81 (d, J = 8.2 Hz, 2H), 7.32–
7.30 (m, 1H), 7.24–7.20 (m, 5H), 7.19–7.14 (m, 1H), 7.08 (dd, J = 7.9,
1.4 Hz, 1H), 3.40–3.36 (m, 2H), 3.25–3.21 (m, 2H), 3.04–2.98 (m, 4H),
2.40 (s, 3H), 2.39 (s, 3H) ppm. 13C NMR (125 MHz, CDCl3): δ = 199.0,
197.4, 171.9, 149.2, 144.2, 143.8, 134.6, 134.1, 133.6, 130.7, 129.39,
129.35, 128.37, 128.30, 127.5, 126.4, 122.6, 39.2, 33.5, 28.6, 24.9,
6.8 Hz, 6H), 7.09 (s, 1H), 7.02 (d, J = 8.2 Hz, 1H), 6.94 (d, J = 8.2 Hz,
1H), 6.75 (d, J = 16.2 Hz, 2H), 3.13 (t, J = 6.5 Hz, 2H), 2.97–2.91 (m,
6H), 2.31 (s, 3H) ppm. 13C NMR (100 MHz, CDCl3): δ = 199.6, 197.7,
172.0, 146.8, 143.2, 142.8, 136.0, 134.7, 134.4, 133.0, 131.2, 130.7,
130.5, 129.0, 128.44, 128.40, 128.1, 126.4, 125.7, 122.2, 41.2, 35.4,
28.4, 24.8, 21.0 ppm. IR (KBr): ν = 3027, 2921, 1754, 1691, 1664,
˜
1612, 1496, 1450, 1363, 1194, 1139, 1094, 977, 750, 691 cm–1. HRMS
(ESI+): calcd. for C30H28NaO4 [M + Na]+ 475.1885, found 475.1881.
21.79, 21.75 ppm. IR (KBr): ν = 2922, 1758, 1682, 1607, 1490, 1207,
˜
(E)-4-Fluoro-2-((E)-3-oxo-5-phenylpent-4-enyl)phenyl 4-oxo-6-
phenylhex-5-enoate (4p): Brown solid (41 mg, 18 %), m.p. 70–
72 °C. 1H NMR (400 MHz, CDCl3): δ = 7.60–7.48 (m, 6H), 7.38–7.35
(m, 6H), 7.04–6.99 (m, 2H), 6.94–6.88 (m, 1H), 6.75 (d, J = 16.4 Hz,
2H), 3.15–3.12 (m, 2H), 2.97–2.93 (m, 6H) ppm. 13C NMR (125 MHz,
1180, 1138, 814 cm–1. HRMS (ESI+): calcd. for C27H27O4 [M + H]+
415.1909, found 415.1906.
2-(3-(4-Methoxyphenyl)-3-oxopropyl)phenyl 4-(4-methoxy-
phenyl)-4-oxobutanoate (4g): Colourless solid (31 mg, 14 %), m.p.
1
104–106 °C. H NMR (400 MHz, CDCl3): δ = 7.94–7.87 (m, 4H), 7.31 CDCl3): δ = 199.0, 197.6, 171.9, 160.4 (d, JC-F = 242.8 Hz), 144.91,
(dd, J = 7.5, 1.7 Hz, 1H), 7.23 (td, J = 7.6, 1.8 Hz, 1H), 7.16 (td, J =
7.4, 1.4 Hz, 1H), 7.07 (dd, J = 7.9, 1.3 Hz, 1H), 6.89 (dd, J = 9.0, 1.0 Hz,
144.89, 143.3, 143.0, 135.6, 135.5, 134.6, 134.4, 130.8, 130.6, 129.1,
128.5 (d, JC-F = 3.0 Hz), 126.2, 125.6, 123.9 (d, JC-F = 8.7 Hz), 117.0
4H), 3.85 (s, 3H), 3.84 (s, 3H), 3.38–3.34 (m, 2H), 3.22–3.17 (m, 2H), (d, JC-F = 23.0 Hz), 114.1 (d, JC-F = 23.2 Hz), 40.7, 35.4, 28.3, 24.7 ppm.
3.03–2.98 (m, 4H) ppm. 13C NMR (125 MHz, CDCl3): δ = 197.9, 196.2,
IR (KBr): ν = 3059, 2923, 1757, 1690, 1664, 1611, 1494, 1449, 1363,
172.0, 163.7, 163.5, 149.2, 133.7, 130.7, 130.5, 130.4, 130.1, 129.6, 1178, 1136, 1095, 976, 759, 690 cm–1. HRMS (ESI+): calcd. for
127.5, 126.3, 122.6, 113.83, 113.78, 55.58, 55.57, 39.0, 33.2, 28.6,
C29H25FNaO4 [M + Na]+ 479.1635, found 479.1630.
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3-(6-Hydroxy-2,3,4-trimethoxyphenyl)-1-(4-hydroxy-3-meth- Taccabulin D (5g): Compound 5b (50 mg, 0.15 mmol) was taken
oxyphenyl)propan-1-one (5a): Colourless solid (126 mg, 69 %),
m.p. 120–122 °C. 1H NMR (400 MHz, CDCl3): δ = 8.72 (s, 1H), 7.58
(dd, J = 8.4, 2.0 Hz, 1H), 7.53 (d, J = 2.0 Hz, 1H), 6.91 (d, J = 8.3 Hz,
1H), 6.34 (s, 1H), 6.19 (s, 1H), 3.94 (s, 3H), 3.91 (s, 3H), 3.79 (s, 3H),
3.77 (s, 3H), 3.39–3.36 (m, 2H), 2.93–2.90 (m, 2H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 201.7, 152.8, 152.2, 151.19, 151.16, 146.7,
135.9, 129.1, 124.2, 114.1, 113.5, 110.1, 97.6, 60.98, 60.93, 56.2, 55.9,
in RB flask with 5 mL DCM. It was cooled to 0 °C and DMAP (2 mg,
0.015 mmol), triethylamine (0.02 mL, 0.15 mmol) and acetyl chloride
(0.01 mL, 0.15 mmol) were added. The reaction mixture was stirred
at r.t. for 12 h. It was quenched with water, extracted with DCM
following the standard workup procedure. The crude product was
purified by column chromatography to obtain 4-(3-(2-hydroxy-4,6-
dimethoxyphenyl)propanoyl)-2-methoxyphenyl acetate (5f) as col-
ourless solid (41 mg, 73 %), m.p. 115–116 °C. 1H NMR (400 MHz,
CDCl3): δ = 8.53 (s, 1H), 7.60–7.58 (m, 2H), 7.11–7.08 (m, 1H), 6.18
(d, J = 2.4 Hz, 1H), 6.05 (d, J = 2.4 Hz, 1H), 3.87 (s, 3H), 3.79 (s, 3H),
3.74 (s, 3H), 3.38–3.35 (m, 2H), 2.95–2.93 (m, 2H), 2.32 (s, 3H) ppm.
13C NMR (100 MHz, CDCl3): δ = 202.4, 168.6, 160.0, 159.1, 156.3,
151.5, 144.4, 135.1, 123.0, 122.1, 111.7, 108.5, 94.7, 91.5, 56.2, 55.6,
39.3, 17.5 ppm. IR (KBr): ν = 3319, 2937, 2849, 1654, 1591, 1515,
˜
1463, 1426, 1276, 1197, 1126, 1088, 1033, 876, 785 cm–1. HRMS
(ESI+): calcd. for C19H22NaO7 [M + Na]+ 385.1263, found 385.1263.
1-(4-Hydroxy-3-methoxyphenyl)-3-(2-hydroxy-4,6-dimethoxy-
phenyl)propan-1-one (Taccabulin C, 5b):[2a] Colourless solid
(104 mg, 62 %), m.p. 133–135 °C. 1H NMR (400 MHz, CDCl3): δ =
8.92 (s, 1H), 7.58 (dd, J = 8.3, 2.0 Hz, 1H), 7.53 (d, J = 1.9 Hz, 1H),
6.91 (d, J = 8.3 Hz, 1H), 6.18 (d, J = 2.4 Hz, 1H), 6.04 (d, J = 2.4 Hz,
1H), 3.92 (s, 3H), 3.79 (s, 3H), 3.74 (s, 3H), 3.36–3.33 (m, 2H), 2.95–
2.92 (m, 2H) ppm. 13C NMR (100 MHz, CDCl3): δ = 202.0, 159.9,
159.1, 156.4, 151.1, 146.7, 129.2, 124.2, 114.0, 110.0, 108.8, 94.7, 91.4,
55.4, 39.1, 20.8, 16.7 ppm. IR (KBr): ν = 3311, 2926, 2853, 1768, 1671,
˜
1621, 1599, 1507, 1465, 1414, 1369, 1279, 1154, 1099, 820, 735 cm–1
.
HRMS (ESI+): calcd. for C20H23O7 [M + H]+ 375.1444, found 375.1447.
The compound 5f (40 mg, 0.069 mmol) was methylated to prepare
compound 5f′ (35 mg, 84 %) following the procedure given in the
synthesis of taccabulin B.
56.2, 55.6, 55.4, 38.6, 16.7 ppm. IR (KBr): ν = 3265, 2940, 2839, 1620,
˜
1590, 1515, 1426, 1274, 1202, 1147, 1099, 817 cm–1. HRMS (EI+):
calcd. for C18H20O6 [M]+ 332.1260, found 332.1268.
The compound 5f′ (30 mg, 0.07 mmol) was taken in RB flask with
3 mL methanol. To that, potassium carbonate (43 mg, 0.3 mmol)
was added and the reaction mixture was stirred at 50 °C for 5 h.
After cooled to r.t., methanol was evaporated and extracted with
DCM. The organic extract was washed with brine solution, dried
with anhydrous MgSO4 and concentrated. The crude product was
purified by column chromatography to obtain 1-(4-hydroxy-3-meth-
oxyphenyl)-3-(2,4,6-trimethoxyphenyl)propan-1-one (Taccabulin D,
5g)[2a] as yellow solid (25 mg, 95 %), m.p. 104–106 °C. 1H NMR
(400 MHz, CDCl3): δ = 7.59 (dd, J = 8.3, 1.7 Hz, 2H), 7.55 (s, 1H), 6.92
(d, J = 8.2 Hz, 1H), 6.14 (s, 2H), 3.94 (s, 3H), 3.81 (s, 3H), 3.78 (s, 6H),
3.05–3.02 (m, 2H), 2.99–2.95 (m, 2H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 199.6, 159.7, 158.9, 150.1, 146.6, 130.2, 123.8, 113.8,
3-(2-Hydroxy-4,6-dimethoxyphenyl)-1-(3-hydroxy-4-methoxy-
phenyl)propan-1-one (5c): Colourless solid (104 mg, 62 %), m.p.
122–124 °C. 1H NMR (400 MHz, CDCl3): δ = 8.89 (s, 1H), 7.59–7.54
(m, 2H), 6.85 (d, J = 8.4 Hz, 1H), 6.18 (d, J = 2.4 Hz, 1H), 6.04 (d, J =
2.4 Hz, 1H), 5.68 (s, 1H), 3.94 (s, 3H), 3.79 (s, 3H), 3.74 (s, 3H), 3.34–
3.31 (m, 2H), 2.93–2.90 (m, 2H) ppm. 13C NMR (100 MHz, CDCl3):
δ = 202.2, 159.9, 159.1, 156.4, 151.2, 145.4, 130.0, 122.2, 114.6, 109.9,
108.9, 94.7, 91.4, 56.2, 55.6, 55.4, 38.8, 16.6 ppm. IR (KBr): ν = 3299,
˜
2940, 2841, 1656, 1610, 1587, 1512, 1456, 1440, 1275, 1215, 1202,
1146, 1099, 816, 764 cm–1. HRMS (ESI+): calcd. for C18H20NaO6 [M +
Na]+ 355.1158, found 355.1159.
110.04, 109.99, 90.5, 56.2, 55.7, 55.5, 38.4, 18.7 ppm. IR (KBr): ν =
˜
1-(Benzo[d][1,3]dioxol-5-yl)-3-(2-hydroxy-4,6-dimethoxy-
phenyl)propan-1-one (5d): Brown solid (113 mg, 68 %), m.p. 124–
126 °C. 1H NMR (400 MHz, CDCl3): δ = 8.80 (s, 1H), 7.60 (dd, J = 8.2,
1.5 Hz, 1H), 7.44 (d, J = 1.4 Hz, 1H), 6.82 (d, J = 8.2 Hz, 1H), 6.18–
6.03 (m, 4H), 3.79 (s, 3H), 3.74 (s, 3H), 3.32–3.29 (m, 2H), 2.93–2.91
(m, 2H) ppm. 13C NMR (100 MHz, CDCl3): δ = 201.5, 159.9, 159.1,
156.4, 152.4, 148.3, 131.1, 125.1, 108.8, 108.2, 108.0, 102.1, 94.8, 91.4,
3375, 1594, 1515, 1499, 1456, 1424, 1295, 1274, 1205, 1151, 1115,
814, 788 cm–1. HRMS (ESI+): calcd. for C19H22NaO6 [M + Na]+
369.1314; found 369.1319.
Taccabulin A (5i): The procedure for the synthesis of taccabulin D
was followed with compound 5c through sequence of monoacetyl-
ation, methylation and deacetylation reactions to obtain taccabulin
A (5i).
55.6, 55.4, 38.9, 16.7 ppm. IR (KBr): ν = 3278, 2940, 2907, 2840, 1659,
˜
1620, 1603, 1503, 1443, 1358, 1258, 1148, 1099, 1038, 814 cm–1
.
5-(3-(2-Hydroxy-4,6-dimethoxyphenyl)propanoyl)-2-methoxy-
HRMS (ESI+): calcd. for C18H19O6 [M + H]+ 331.1182, found 331.1184.
phenyl acetate (5h): Colourless solid (29 mg, 86 %), m.p. 132–
1
134 °C. H NMR (400 MHz, CDCl3): δ = 8.73 (s, 1H), 7.90 (dd, J = 8.7,
Taccabulin B (5e): Compound 5a (25 mg, 0.069 mmol) was taken
in RB flask containing 5 mL of acetone. To this potassium carbonate
(95.4 mg, 0.69 mmol) and methyl iodide (0.02 mL, 0.36 mmol) were
added and stirred at 50 °C for 8 h. After the reaction, RB was cooled
to r.t., acetone was evaporated. The product mixture was extracted
with ethyl acetate, washed with brine solution, dried with anhy-
drous MgSO4 and concentrated. The crude was purified by column
chromatography to obtain 1-(3,4-dimethoxyphenyl)-3-(2,3,4,6-tetra-
methoxyphenyl)propan-1-one (Taccabulin B, 5e)[2a] as yellow solid
(21 mg, 78 %), m.p. 78–80 °C. 1H NMR (400 MHz, CDCl3): δ = 7.63
(dd, J = 8.4, 2.0 Hz, 1H), 7.55 (d, J = 2.0 Hz, 1H), 6.87 (d, J = 8.4 Hz,
1H), 6.28 (s, 1H), 3.94 (s, 3H), 3.93 (s, 3H), 3.88 (s, 3H), 3.87 (s, 3H),
3.82 (s, 3H), 3.78 (s, 3H), 3.11–3.07 (m, 2H), 2.99–2.95 (m, 2H) ppm.
13C NMR (100 MHz, CDCl3): δ = 199.2, 153.9, 153.1, 152.6, 152.0,
149.0, 136.5, 130.4, 122.9, 115.4, 110.4, 110.1, 92.6, 61.3, 61.1, 56.3,
2.2 Hz, 1H), 7.68 (d, J = 2.2 Hz, 1H), 6.97 (d, J = 8.7 Hz, 1H), 6.17 (d,
J = 2.4 Hz, 1H), 6.04 (d, J = 2.4 Hz, 1H), 3.89 (s, 3H), 3.79 (s, 3H), 3.74
(s, 3H), 3.33–3.31 (m, 2H), 2.94–2.91 (m, 2H), 2.32 (s, 3H) ppm. 13C
NMR (100 MHz, CDCl3): δ = 201.4, 168.9, 159.9, 159.1, 156.4, 155.9,
139.6, 129.4, 128.4, 123.4, 111.7, 108.7, 94.8, 91.4, 56.3, 55.6, 55.4,
38.8, 20.7, 16.6 ppm. IR (KBr): ν = 3286, 2942, 2904, 2841, 1768,
˜
1662, 1606, 1513, 1430, 1369, 1279, 1202, 1147, 1099, 1018,
817 cm–1. HRMS (ESI+): calcd. for C20H23O7 [M + H]+ 375.1444; found
375.1446.
1-(3-Hydroxy-4-methoxyphenyl)-3-(2,4,6-trimethoxyphenyl)-
propan-1-one (Taccabulin A, 5i):[2b] Colourless solid (8 mg, 72 %),
1
m.p. 132–134 °C. H NMR (500 MHz, CDCl3): δ = 7.62–7.57 (m, 2H),
6.87 (d, J = 8.4 Hz, 1H), 6.14 (s, 2H), 5.61 (s, 1H), 3.95 (s, 3H), 3.81 (s,
3H), 3.79 (s, 6H), 3.03–2.99 (m, 2H), 2.98–2.94 (m, 2H) ppm. 13C NMR
(125 MHz, CDCl3): δ = 199.8, 159.7, 158.9, 150.4, 145.4, 131.0, 121.7,
56.2, 56.1, 55.9, 38.9, 19.4 ppm. IR (KBr): ν = 2935, 2839, 1671, 1596,
˜
1515, 1463, 1410, 1267, 1241, 1108, 1024, 805 cm–1. HRMS (ESI+): 114.7, 110.1, 109.9, 90.6, 56.2, 55.7, 55.5, 38.7, 18.8 ppm. IR (KBr):
calcd. for C21H27O7 [M + H]+ 391.1757, found 391.1754.
ν = 3402, 2927, 2850, 2253, 1668, 1608, 1513, 1455, 1274, 1205,
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1150, 1112, 1024, 811 cm–1. HRMS (ESI+): calcd. for C19H22NaO6 [M
+ Na]+ 369.1314; found 369.1317.
[2] a) J. Peng, A. L. Risinger, C. Da, G. A. Fest, G. E. Kellogg, S. L. Mooberry,
J. Nat. Prod. 2013, 76, 2189–2194; b) A. L. Risinger, J. Peng, C. C. Rohena,
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1929; c) F.-F. Gan, K. K. Kaminska, H. Yang, C.-Y. Liew, P.-C. Leow, C.-L. So,
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Taccabulin E (5k): Compound 5d (50 mg, 0.069 mmol) was methyl-
ated by following the procedure given for taccabulin B to obtain 1-
(benzo[d][1,3]dioxol-5-yl)-3-(2,4,6-trimethoxyphenyl)propan-1-one
(5j) as yellow solid (42 mg, 81 %), m.p. 108–110 °C. 1H NMR
(400 MHz, CDCl3): δ = 7.60 (dd, J = 8.2, 1.7 Hz, 1H), 7.50 (d, J =
1.6 Hz, 1H), 6.83 (d, J = 8.2 Hz, 1H), 6.13 (s, 2H), 6.03 (s, 2H), 3.81 (s,
3H), 3.78 (s, 6H), 3.03–2.93 (m, 4H) ppm. 13C NMR (100 MHz, CDCl3):
δ = 199.1, 159.7, 158.9, 151.5, 148.1, 132.1, 124.5, 110.0, 108.3, 107.9,
[4] a) A. Briot, C. Baehr, R. Brouillard, A. Wagner, C. Mioskowski, J. Org. Chem.
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101.8, 90.6, 55.7, 55.5, 38.8, 18.8 ppm. IR (KBr): ν = 2940, 2838, 1673,
˜
[5] Y. Wang, Y. Chen, Y. Yang, B. Zhou, Org. Chem. Front. 2018, 5, 1844–1847.
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1609, 1500, 1455, 1440, 1293, 1260, 1246, 1205, 1161, 1150, 1116,
1038, 811 cm–1. HRMS (ESI+): calcd. for C19H21O6 [M + H]+ 345.1338;
found 345.1335.
The compound 5j (30 mg, 0.087 mmol) was taken in RB flask with
methanol (3 mL). It was cooled to 0 °C, NaBH4 (13.2 mg, 0.35 mmol)
was added portion wise and stirred for 1 h. The reaction mixture
was brought to r.t. and stirred for 10 h. It was then quenched with
water and extracted with chloroform and concentrated. The crude
product was purified by column chromatography to obtain 1-
(benzo[d][1,3]dioxol-5-yl)-3-(2,4,6-trimethoxyphenyl)propan-1-ol
(Taccabulin E, 5k)[2a] as colourless solid (24 mg, 80 %), m.p. 102–
104 °C. 1H NMR (400 MHz, CDCl3): δ = 6.86 (d, J = 1.6 Hz, 1H), 6.78–
6.72 (m, 2H), 6.16 (s, 2H), 5.92 (s, 2H), 4.41 (dd, J = 8.3, 5.2 Hz, 1H),
3.82–3.81 (m, 9H), 3.09 (s, 1H), 2.75–2.71 (m, 2H), 1.89–1.83 (m, 2H)
ppm. 13C NMR (100 MHz, CDCl3): δ = 159.6, 158.9, 147.6, 146.5,
138.9, 119.3, 109.9, 108.0, 106.7, 100.9, 90.8, 72.8, 55.9, 55.5, 38.8,
18.8 ppm. IR (KBr): ν = 3462, 2924, 2852, 1609, 1595, 1498, 1488,
˜
1455, 1417, 1245, 1205, 1160, 1149, 1039, 935, 811 cm–1. HRMS
(ESI+): calcd. for C19H22NaO6 [M + Na]+ 369.1314; found 369.1312.
Acknowledgments
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2012). B. S. R acknowledges the Council of Scientific and Indus-
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Keywords: Decarbonylative addition · Rhodium catalysis ·
Salicylaldehyde · o-Hydroxydihydrochalcones
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Received: September 4, 2019
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© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
Decarbonylative Addition
M. L. N. Rao,*
B. S. Ramakrishna ........................... 1–11
Rh-Catalyzed Decarbonylative Addi-
tion of Salicylaldehydes with Vinyl
Ketones: Synthesis of Taccabulins
A–E
A Rh-catalyzed decarbonylative addi- yields. This protocol was applied in the
tion of salicylaldehydes with vinyl ket- synthesis of taccabulin family of natu-
ones was developed for the synthesis ral products.
of o-hydroxydihydrochalcones in good
DOI: 10.1002/ejoc.201901314
Eur. J. Org. Chem. 0000, 0–0
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11
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim