Ruthenium-catalyzed synthesis of β-oxo esters in aqueous medium: Scope and limitations

Article abstract of DOI:10.1039/b914774h

The ability of the hydrosoluble ruthenium(ii) complexes [RuCl ₂(η⁶-arene)(PTA)] 3a-d, [RuCl₂(η ⁶-arene)(PTA-Bn)] 4a-d, [RuCl₂(η⁶-arene) (DAPTA)] 5a-d, [RuCl₂(η⁶-arene)(TPPMS)] 6a-d (arene = C₆H₆, p-cymene, 1,3,5-C₆H₃Me ₃, C₆Me₆) to promote the atom-economic formation of β-oxo esters, by addition of carboxylic acids to terminal propargylic alcohols in water has been explored. Scope, limitations and catalyst recycling have been evaluated using the most active catalyst [RuCl ₂(η⁶-C₆H₆)(TPPMS)], 6a.

Full text of DOI:10.1039/b914774h

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PAPER
www.rsc.org/greenchem | Green Chemistry
Ruthenium-catalyzed synthesis of b-oxo esters in aqueous medium: Scope
and limitations
Victorio Cadierno,* Javier Francos and Jose´ Gimeno*
Received 21st July 2009, Accepted 30th September 2009
First published as an Advance Article on the web 28th October 2009
DOI: 10.1039/b914774h
6
The ability of the hydrosoluble ruthenium(II) complexes [RuCl2(h -arene)(PTA)] 3a–d,
6
6
6
[RuCl2(h -arene)(PTA-Bn)] 4a–d, [RuCl2(h -arene)(DAPTA)] 5a–d, [RuCl2(h -arene)(TPPMS)]
6a–d (arene = C6H6, p-cymene, 1,3,5-C6H3Me3, C6Me6) to promote the atom-economic formation
of b-oxo esters, by addition of carboxylic acids to terminal propargylic alcohols in water has been
explored. Scope, limitations and catalyst recycling have been evaluated using the most active
6
catalyst [RuCl2(h -C6H6)(TPPMS)], 6a.
From a mechanistic point of view, these catalytic transforma-
tions are based on the well-known ability of ruthenium com-
Introduction
b-Oxo esters are important intermediates in organic synthesis
since they can be easily transformed into the corresponding
a-hydroxy ketones,1 which are structural units present in a
large variety of biologically active natural products.2 Several
procedures are presently available to prepare these types of
compounds, such as the carbonylation of a-halo ketones,3 the
anodic oxidation of enol acetates,4 the Cu catalyzed insertion
of a-diazo ketones into the O–H bond of carboxylic acids,5 the
two-step hydration/esterification of propargylic alcohols6 or the
oxidation of ketones with metal–acetate complexes.7 However,
the scope of most of these methods is rather low, and they also
suffer from environmental problems associated with the use of
harmful reagents.
≡
plexes to promote the addition of carboxylic acids to the C C
bond of terminal alkynes to afford enol esters.12,13 Thus, after
the initial Markovnikov addition of the carboxylate anion to
the p-alkyne intermediate A, intramolecular transesterification
of the resulting enol ester complex B readily takes place, leading
to the alkenyl derivative C. Final protonolysis of C liberates the
b-oxo ester 2 and regenerates the catalytically active ruthenium
species (Scheme 2).
The catalytic addition of carboxylic acids to terminal propar-
gylic alcohols, 1, represents an appealing and elegant alternative
to b-oxo esters, 2 (Scheme 1); an atom-economic transformation
that can be efficiently promoted by ruthenium complexes.8
Among the different catalysts employed, the best results in terms
of activity and selectivity have been described using the mononu-
6
clear arene–Ru(II) derivatives [RuCl2(h -arene)(PR3)] (arene =
p-cymene, C6Me6; PR3 = PPh3, PMe3, phosphoramidite),9
the dimeric complex [{Ru(m-O2CH)(CO)2(PPh3)}2]10 and the
5
catalytic system composed of [Ru(h -C8H11)2] (C8H11 = cyclooc-
tadienyl), a trialkyl phosphine and maleic anhydride.11
Scheme 1 b-Oxo ester formation by addition of carboxylic acids to
terminal propargylic alcohols
Scheme 2 Proposed mechanism for the Ru-catalyzed b-oxo ester
formation reactions
On the other hand, a crucial factor in realizing a “green
chemical” process involves the choice of a safe, non-toxic
and cheap solvent.14 Water is undoubtedly one of the most
appealing candidates.15 Therefore, the development of organic
Departamento de Qu´ımica Orga´nica e Inorga´nica. IUQOEM (Unidad
Asociada al CSIC), Universidad de Oviedo, Julia´n Claver´ıa 8, 33006,
Oviedo, Spain. E-mail: vcm@uniovi.es, jgh@uniovi.es;
Fax: (34)985103446; Tel: (34)985102985
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Table 1 Ruthenium-catalyzed synthesis of b-oxo ester 2a in watera
transformations in aqueous media has become one of the
major cornerstones in modern chemistry.16 Following this
general trend, the design of novel transition metal catalysts for
organic reactions in water has attracted a growing interest in
recent years,17 disclosing a wide variety of highly efficient and
selective synthetic approaches to date.16,17 In this context, in the
course of our current studies directed toward the application
of ruthenium catalysts in aqueous organic synthesis,18 we have
recently reported the preparation of half-sandwich ruthenium(II)
Entry Catalyst
Time/h Yieldb/%
6
1
2
3
4
5
6
7
8
[RuCl2(h -C6H6)(PTA)] 3a
24
24
24
24
24
24
64c
39d
54e
71c
38f
63
6
[RuCl2(h -p-cymene)(PTA)] 3b
6
complexes [RuCl2(h -arene)(PR3)] containing the hydrosoluble
6
[RuCl2(h -1,3,5-C6H3Me3)(PTA)] 3c
6
phosphine ligands PTA (3a–d), PTA-Bn (4a–d), DAPTA (5a–d)
and TPPMS (6a–d) (see Fig. 1),19 also showing that some of
them are excellent precatalysts for the selective hydration of
organonitriles to amides in aqueous medium under neutral
conditions.20 The availability of these compounds, along with
the known effectiveness of mononuclear arene–Ru(II) derivatives
[RuCl2(h -C6Me6)(PTA)] 3d
6
[RuCl2(h -C6H6)(PTA-Bn)] 4a
6
[RuCl2(h -p-cymene)(PTA-Bn)] 4b
6
[RuCl2(h -1,3,5-C6H3Me3)(PTA-Bn)] 4c 24
30
14
6
[RuCl2(h -C6Me6)(PTA-Bn)] 4d
24
24
24
6
9
[RuCl2(h -C6H6)(DAPTA)] 5a
62g
50e
61h
56g
87
6
10
11
12
13
14
15
16
17i
[RuCl2(h -p-cymene)(DAPTA)] 5b
6
[RuCl2(h -1,3,5-C6H3Me3)(DAPTA)] 5c 24
6
[RuCl2(h -arene)(PR3)] in b-oxo ester formation by addition of
6
[RuCl2(h -C6Me6)(DAPTA)] 5d
24
24
24
carboxylic acids to alkynols,9 prompted us to study this atom-
economic transformation in water. To the best of our knowledge,
no precedents on the use of environmentally benign aqueous
media in these catalytic addition reactions have been described
previously.
6
[RuCl2(h -C6H6)(TPPMS)] 6a
6
[RuCl2(h -p-cymene)(TPPMS)] 6b
85
79
76
95
6
[RuCl2(h -1,3,5-C6H3Me3)(TPPMS)] 6c 24
6
[RuCl2(h -C6Me6)(TPPMS)] 6d
24
3
6
[RuCl2(h -C6H6)(TPPMS)] 6a
a Reactions performed under N2 atmosphere at 60 ◦C using 1 mmol of
1-phenyl-2-propyn-1-ol (1 M in water) and 1 mmol of benzoic acid.
b Determined by GC. c 5% of styrene is formed. d 10% of styrene is
formed. e 7% of styrene is formed. f 1% of styrene is formed. g 2% of
styrene is formed. h 4% of styrene is formed. i Reaction performed at
100 ◦C.
of 2a in 76–87% GC yields (entries 13–16). In contrast, the
use of the PTA, PTA-Bn and DAPTA-based catalysts 3a–5d
(entries 1–12) resulted in lower yields of 2a (14–71%); in most
of these reactions the formation of minor amounts of styrene as
by-product was also observed (entries 1–5 and 9–11).
Formation of alkene side products, arising from the cleavage
≡
of the C C bond of the alkynol, has been recently observed in
related addition reactions promoted by (h -arene)ruthenium(II)-
6
phosphoramidite catalysts in organic media.9b Such a com-
petitive process involves the generation of a highly reactive
allenylidene–ruthenium intermediate E (Scheme 3) as the result
of an initial tautomerization of the p-alkyne complex A into
the 3-hydroxy-vinylidene D, and subsequent dehydration of
D. Then, the carbon–carbon cleavage process takes place via
nucleophilic addition of water to the electrophilic a-carbon
of the allenylidene chain, a well-known transformation in the
chemistry of metal–allenylidenes.22–24
Fig. 1 Structure of the water-soluble ruthenium(II) catalysts used in
this study.
Results and discussion
Table 1 provides a summary of our catalyst screening. We
used the addition of benzoic acid to the commercially available
alkynol 1-phenyl-2-propyn-1-ol 1a as a model reaction. In a
typical experiment, the alkynol (1 mmol) and the acid (1 mmol)
were suspended in water (1 mL), under a nitrogen atmosphere,
and treated with 2 mol% of the corresponding ruthenium
complex 3a–6d at 60 ◦C for 24 h. Under these conditions, all
the complexes checked were found to be active catalysts in the
addition process providing the b-oxo ester 1-phenyl-2-oxopropyl
benzoate 2a in moderate to good yields. Interestingly, the nature
of the hydrosoluble phosphine played an important role in
both the efficiency and selectivity of the process.21 Thus, the
best results were obtained with complexes 6a–d, all bearing the
sulfonated ligand TPPMS, which led to the selective formation
Scheme 3 Reaction pathway explaining the formation of styrene
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It is known that, due to its p-accepting properties, the
allenylidene ligand formation is favored by electron-rich metal
fragments.22 This fact could explain why the occurrence of
styrene takes place using those catalysts bearing the aliphatic
phosphines PTA, PTA-Bn and DAPTA, all of them more
basic than the aromatic sulfonated one, TPPMS. From this
1a (entry 1), other aromatic (1b–j; entries 2–10) and aliphatic
(1k–n; entries 11–14) secondary alkynols could be converted
into the corresponding b-oxo esters 2b–n in moderate to good
yields (36–84% GC yields; 25–78% isolated yields) after 3–6 h
of heating. Concerning the aromatic substrates, an influence of
the electronic properties of the aryl rings on the efficiency of the
process was observed. Thus, alkynols with electron-donating
groups showed less reactivity (entries 8–10) compared to sub-
strates with electron-withdrawing functionalities (entries 4–7),
even when, in cases of the latter, the minor formation of olefinic
6
general catalyst screening, the benzene derivative [RuCl2(h -
C6H6)(TPPMS)] 6a emerged as the top choice due to its
selectivity and efficiency (87% GC yield of 2a after 24 h; entry
13). In addition, both the yield and the rate of the process could
be significantly improved by increasing the working temperature
from 60 to 100 ◦C. Under these new reaction conditions, using
the same catalyst loading (2 mol% of 6a), the b-oxo ester 2a was
formed in 95% GC yield after only 3 h (entry 17). No appreciable
difference in activity was observed when an organic solvent
(toluene) was used instead of water. Subsequent purification by
column chromatography on silica gel provided an analytically
pure sample of 2a in 88% isolated yield.
Under these optimized reaction conditions (1 M solution of
the alkynol in water; [alkynol] : [6a] : [PhCO2H] ratio = 50 : 1 : 50;
100 ◦C) the ability of 6a to promote the addition of benzoic acid
to a number of other terminal propargylic alcohols was explored.
The results are summarized in Table 2. Thus, as observed for
≡
by-products, via the competitive C C bond scission process
discussed above was observed. As expected,9–11 this addition
process is not restricted to secondary alkynols. Thus, as shown
in entry 15, propargylic alcohol itself, 1o, can also participate in
this transformation leading to the known 2-oxopropyl benzoate
(2o)9a in 60% isolated yield after only 3 h. Regarding tertiary
alcohols (entries 16–22), the best results were obtained with
1-ethynyl-cycloalkanols (1q–s; entries 17–19) from which the
correspondingb-oxo esters 2q–s could besynthesized in excellent
yields (85–90% isolated yield; entries 17–19). The process is also
operative starting from 2-phenyl-3-butyn-2-ol (1p; entry 15) and
2-ethynyl-2-adamantanol (1t; entry 20). However, its efficiency
was found to be lower compared to the precedent cases (55–57%
yield). Solvent removal and chromatographic work-up on silica
gel provided analytically pure samples of all these b-oxo esters,
which were fully characterized by means of standard analytical
and spectroscopic techniques (see the Experimental section).
Remarkably, when the addition of PhCO2H to tertiary
diaromatic substrates, such as 1,1-diphenyl-2-propyn-1-ol (1u;
entry 21) or 1,1-bis(4-chlorophenyl)-2-propyn-1-ol (1v; entry
22), was attempted, only trace amounts of the expected b-oxo
esters could be detected by GC. In these cases, the reactions gave
the major products 1,1-diphenyl-ethene (80%) and 1,1-bis(4-
chlorophenyl)-ethene (63%), respectively.
Table 2 Ruthenium-catalyzed synthesis of b-oxo esters in water: gen-
erality on the propargylic alcohola
Entry Propargylic alcohol 1
Time/h
Yield of 2b/%
1
2
3
4
5
6
7
8
R1 = H, R2 = Ph 1a
3
3
3
6
6
6
6
6
6
6
3
3
6
6
3
6
2
3
3
8
3
3
2a; 95 (88)
2b; 76 (69)c
2c; 72 (63)d
2d; 84 (78)e
2e; 75 (63)f
2f; 75 (65)g
2g; 71 (60)h
2h; 57 (48)
2i; 59 (51)
2j; 36 (25)
2k; 67 (59)
2l; 82 (77)i
2m; 80 (72)
2n; 68 (63)j
2o; 71 (60)
2p; 65 (55)
2q; 99 (90)
2r; 99 (88)
2s; 92 (85)
2t; 63 (57)k
2u; 3l
R1 = H, R2 = 1-naphthyl 1b
R1 = H, R2 = 2-naphthyl 1c
R1 = H, R2 = 2-C6H4Cl 1d
R1 = H, R2 = 3-C6H4Cl 1e
R1 = H, R2 = 4-C6H4Cl 1f
R1 = H, R2 = C6F5 1g
We must also mention that, despite the ability of complex
6a to promote the addition of benzoic acid to 1-ethynyl-
cycloalkanols 1q–s (entries 17–19), attempts to synthesize b-oxo
esters derived from the hormonal steroids ethisterone, 1x, and
mestranol, 1y, also failed.25 Thus, we found that treatment of
1x–y with 1 equivalent of PhCO2H, under the same catalytic
conditions described above, led to the slow formation (48–60 h)
of the known 17,17-dimethyl-18-norandrosta-4,13-dien-3-one
726 and 3-methoxy-17,17-dimethyl-gona-1,3,5(10),13-tetraene
8,27 respectively, isolated in moderate yields (50–68%) after
appropriate chromatographic workup (Scheme 4). Compounds
7–8 most probably result from the initial ruthenium-catalyzed
dehydration and cleavage of the 2-propyn-1-ol function, via
the corresponding allenylidene intermediates,28 which affords
the olefinic intermediates F. Then, a classical acid-promoted
Wagner–Meerwein rearrangement can take place leading to the
final steroids 7–8.26,27 All these results seem to indicate that the
competitive p-alkynol to allenylidene rearrangement is governed
not only by the electronic nature of the catalyst, but also by the
steric requirements of the propargylic alcohol substituents, with
bulky substrates clearly favoring this undesirable side reaction.
Once the generality of this aqueous transformation with
respect to the propargylic alcohol had been evaluated, the scope
regarding the nature of the carboxylic acid was explored. Results
are collected in Fig. 2.
R1 = H, R2 = 2-C6H4OMe 1h
R1 = H, R2 = 3-C6H4OMe 1i
R1 = H, R2 = 4-C6H4OMe 1j
R1 = H, R2 = Me 1k
9
10
11
12
13
14
15
16
17
18
19
20
21
22
R1 = H, R2 = CH2Ph 1l
R1 = H, R2 = CH2CH2Ph 1m
R1 = H, R2 = C(H)MePh 1n
R1 = R2 = H 1o
R1 = Me, R2 = Ph 1p
R1R2 = –(CH2)4– 1q
R1R2 = –(CH2)5– 1r
R1R2 = –(CH2)6– 1s
R1R2 = Adamantane-2,2-diyl 1t
R1 = R2 = Ph 1u
R1 = R2 = 4-C6H4Cl 1v
2v; 8m
a Reactions performed under N2 atmosphere at 100 ◦C using 1 mmol of
the corresponding propargylic alcohol (1 M in water) and 1 mmol of
benzoic acid. b Determined by GC. Isolated yields are given in brackets.
c 15% of 1-vinyl-naphthalene is formed. d 10% of 2-vinyl-naphthalene is
formed. e 4% of 2-chloro-styrene is formed. f 6% of 3-chloro-styrene
is formed. g 6% of 4-chloro-styrene is formed. h 14% of 2,3,4,5,6-
pentafluoro-styrene is formed. i 7% of allyl-benzene is formed. j 4%
of (1-methylallyl)-benzene is formed. k 5% of 2-methylene-adamantane
is formed. l 80% of 1,1-diphenyl-ethene is formed. m 63% of 1,1-bis(4-
chlorophenyl)-ethene is formed.
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Scheme 4 Transformation of ethisterone and mestranol into steroids 7–8
Thus, we have found that using alkynol 1a as a model
compound, several aromatic acids, bearing functional groups
such as halide, alkoxy, ketone or sulfonamide, can be successfully
employed in this addition process, affording the corresponding
b-oxo esters 9a–g in good isolated yields (63–86%). Interestingly,
the reaction is also compatible with heteroaromatic substrates.
Thus, carboxylic acids derived from tetrahydrofuran, pyrrole,
thiophene, indole or 2-oxo-2H-chromene were efficiently (64–
91% yield) converted into the novel b-oxo esters 9h–m. In
addition, the clean formation of 9n–o, starting from the aliphatic
heptanoic and 3-cyclopentyl-propionic acid confirmed the wide
scope of this catalytic transformation.
triple bond instead of the desired addition. In summary, the
atom-economic nature of this catalytic transformation, which
allows access to valuable synthetic intermediates from readily
accessible or commercially available starting materials, along
with the remarkable activity of 6a, confer a genuine potential
for practical application in organic chemistry to the aqueous
protocol reported herein.
Experimental section
General methods
Infrared spectra were recorded on a Perkin-Elmer 1720-XFT
spectrometer. NMR spectra were recorded on a Bruker DPX-
300 instrument at 300 MHz (1H), 75.4 MHz (13C) or 282.4 (19F).
The chemical shift values (d) are given in parts per million and
are referred to the residual peak of the deuterated solvent used
(CDCl3). DEPT experiments have been carried out for all the
compounds reported. GC/MS measurements were performed
on a Agilent 6890 N equipment coupled to a 5973 mass
detector (70eV electron impact ionization) using a HP-1MS
column. ESI-TOF high-resolution mass spectra were provided
by the mass spectrometry service of the University of Santiago
de Compostela. Elemental analyses were performed with a
Perkin-Elmer 2400 microanalyzer. Flash chromatography was
performed using Merck silica gel 60 (230-400 mesh). Propargylic
alcohols 1a–y were obtained from commercial suppliers or
synthesized by following the classical Midland’s procedure.29
Ruthenium(II) complexes 3a–6d were prepared by following the
methods reported in the literature.20,30
Finally, the catalyst recycling has also been investigated using
the addition of benzoic acid to 1-phenyl-2-propyn-1-ol 1a as
model reaction (entry 1 in Table 2). Thus, we have found that
after a simple extraction of the final product 2a with hexane,
6
the aqueous phase, containing [RuCl2(h -C6H6)(TPPMS)] 6a,
can be re-used in at least two consecutive runs. However, an
important decrease of the activity was observed in the third cycle
(91% GC yield after 24 h) due to the partial decomposition of
the catalyst (release of the C6H6 ligand was observed by GC after
prolonged periods in solution at 100 ◦C).
Conclusions
We have demonstrated that b-oxo ester formation, by catalytic
addition of carboxylic acids to terminal propargylic alcohols,
can be conveniently performed in environmentally benign
aqueous medium using the water-soluble ruthenium(II) complex
6
[RuCl2(h -C6H6)(TPPMS)] 6a. The process showed a remark-
ably wide scope, tolerating the presence of several functional
groups in the substrates. In fact, its only limitation concerns
the use of bulky tertiary alkynols which, under the catalytic
General procedure for the catalytic reactions. Under nitro-
gen atmosphere, water (1 cm3), the corresponding propargylic
alcohol (1 mmol), carboxylic acid (1 mmol), and the ruthenium
catalyst 6a (12 mg, 0.02 mmol) were introduced into a sealed tube
≡
conditions employed, undergo hydrolytic cleavage of the C C
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Fig. 2 Structures of the b-oxo esters 9a–o.
and the resulting reaction mixture stirred at 100 ◦C for the time
indicated (see Table 2, Schemes 3 and 4, or Fig. 2). The course of
the reaction was monitored by regular sampling and analysis by
GC. After elimination of the solvent under reduced pressure, the
crude reaction mixture was purified by column chromatography
over silica gel using an ethyl acetate–hexane mixture (1 : 10 v/v)
1732 (C O) cm ; GC-MS (EI, 70eV): m/z 304 (30%, M ),
261 (30), 105 (100), 77 (25); Elemental analysis calcd (%) for
C20H16O3: C 78.93, H 5.30; found: C 78.81, H 5.23.
-1
+
=
1-(2-Naphthyl)-2-oxopropyl benzoate 2c. Pale yellow solid;
1H NMR (300.1 MHz, CDCl3): d 2.24 (s, 3H), 6.38 (s, 1H),
7.45–7.63 (m, 6H), 7.89–7.94 (m, 3H), 8.02–8.17 (m, 3H) ppm;
as eluent. Compounds 2a,31 2k,32 2o,9a 2p,9b 2q,9b 2r,9b 26 and 827
7
1
13C{ H} NMR (75.47 MHz, CDCl3): d 26.2, 81.4, 124.7, 126.7,
have been previously described in the literature. Characterization
data for the novel b-oxo esters synthesized in this work are as
follows:
126.9, 127.7, 127.8, 128.1, 128.4, 129.1, 129.2, 129.9, 130.6,
131.1, 133.4, 133.5, 165.8, 201.8 ppm; IR (nujol): n 1721 and
-1
+
=
1738 (C O) cm ; GC-MS (EI, 70eV): m/z 304 (30%, M ),
261 (30), 105 (100), 77 (25); Elemental analysis calcd (%) for
C20H16O3: C 78.93, H 5.30; found: C 78.77, H 5.36.
1-(1-Naphthyl)-2-oxopropyl benzoate 2b. Pale yellow solid;
1H NMR (300.1 MHz, CDCl3): d 2.16 (s, 3H), 6.88 (s, 1H),
7.41–7.71 (m, 7H), 7.91–7.95 (m, 3H), 8.01–8.12 (m, 2H) ppm;
1-(2-Chlorophenyl)-2-oxopropyl benzoate 2d. Colourless oil;
1H NMR (300.1 MHz, CDCl3): d 2.26 (s, 3H), 6.74 (s, 1H),
7.33–7.37 (m, 2H), 7.42–7.49 (m, 3H), 7.53–7.60 (m, 2H), 8.09–
8.12 (m, 2H) ppm; 13C{ H} NMR (75.47 MHz, CDCl3): d 26.8,
1
13C{ H} NMR (75.47 MHz, CDCl3): d 26.3, 80.0, 123.9, 125.3,
126.2, 127.2, 128.3, 128.4, 128.9, 129.2, 129.5, 129.9, 130.3,
1
131.3, 133.4, 134.2, 165.7, 201.8 ppm; IR (nujol): n 1716 and
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77.4, 127.5, 128.4, 129.1, 129.8, 129.9, 130.1, 130.6, 131.7, 133.5,
GC-MS (EI, 70eV): m/z 284 (1%, M+), 241 (10), 105 (100), 77
(30); HRMS (ESI-TOF): m/z 285.112687 [M+ + H], C17H17O4
requires 285.112684.
-1
=
133.9, 165.5, 200.1 ppm; IR (neat): n 1731 and 1785 (C O) cm ;
GC-MS (EI, 70eV): m/z 253 (3%, M+ - Cl), 245 (10), 211 (5),
105 (100), 77 (30); HRMS (ESI-TOF): m/z 289.063254 [M+ +
H], C16H14O3Cl requires 289.063147.
1-Benzyl-2-oxopropyl benzoate 2l. Colourless oil; 1H NMR
(300.1 MHz, CDCl3): d 2.14 (s, 3H), 3.22 (m, 2H), 5.45 (dd,
J = 7.7 and 5.1 Hz, 1H), 7.23–7.35 (m, 5H), 7.43–7.61 (m,
1-(3-Chlorophenyl)-2-oxopropyl benzoate 2e. Colourless oil;
1H NMR (300.1 MHz, CDCl3): d 2.22 (s, 3H), 6.16 (s, 1H),
7.30–7.43 (m, 4H), 7.45–7.61 (m, 3H), 8.10–8.12 (m, 2H) ppm;
1
3H), 8.04 (m, 2H) ppm; 13C{ H} NMR (75.47 MHz, CDCl3): d
26.9, 36.9, 79.5, 127.1, 128.5, 128.6, 129.1, 129.4, 129.7, 133.5,
1
13C{ H} NMR (75.47 MHz, CDCl3): d 26.1, 80.4, 125.9, 127.7,
-1
=
135.8, 165.9, 205.7 ppm; IR (neat): n 1720 (br, C O) cm ; GC-
MS (EI, 70eV): m/z 146 (40%, M+ - PhCO2), 105 (100), 77
(40); HRMS (ESI-TOF): m/z 269.117855 [M+ + H], C17H17O3
requires 269.117770.
128.5, 128.9, 129.5, 129.9, 130.3, 133.6, 134.9, 135.2, 165.5,
-1
=
201.4 ppm; IR (neat): n 1706 and 1732 (C O) cm ; GC-MS
(EI, 70eV): m/z 288 (1%, M+), 245 (10), 211 (2), 105 (100), 77
(30); HRMS (ESI-TOF): m/z 289.063007 [M+ + H], C16H14O3Cl
requires 289.063147.
1-Phenethyl-2-oxopropyl benzoate 2m. Colourless oil; 1H
NMR (300.1 MHz, CDCl3): d 2.24 (s, 3H), 2.30 (m, 2H), 2.85
(m, 2H), 5.27 (dd, J = 6.0 and 6.0 Hz, 1H), 7.22–7.35 (m, 5H),
1-(4-Chlorophenyl)-2-oxopropyl benzoate 2f. Colourless oil;
1H NMR (300.1 MHz, CDCl3): d 2.21 (s, 3H), 6.19 (s, 1H),
7.41–7.49 (m, 4H), 7.58–7.61 (m, 3H), 8.11–8.13 (m, 2H) ppm;
1
7.49–7.54 (m, 2H), 7.65 (m, 1H), 8.13 (m, 2H) ppm; 13C{ H}
NMR (75.47 MHz, CDCl3): d 26.2, 31.6, 32.1, 78.5, 126.4,
1
13C{ H} NMR (75.47 MHz, CDCl3): d 26.1, 80.5, 128.6, 129.2,
128.5, 128.6, 128.7, 129.3, 129.8, 133.5, 140.4, 166.0, 205.4 ppm;
129.4, 129.9, 132.0, 132.1, 135.2, 135.5, 135.9, 165.7, 201.6 ppm;
-1
=
IR (neat): n 1716 and 1734 (C O) cm ; GC-MS (EI, 70eV):
-1
=
IR (neat): n 1716 and 1737 (C O) cm ; GC-MS (EI, 70eV): m/z
m/z 282 (1%, M+), 105 (100), 77 (25); HRMS (ESI-TOF): m/z
288 (1%, M+), 245 (10), 105 (100), 77 (30); HRMS (ESI-TOF):
m/z 289.062991 [M+ + H], C16H14O3Cl requires 289.063147.
283.133166 [M+ + H], C18H19O3 requires 283.133420.
1-(1-Phenylethyl)-2-oxopropyl benzoate 2n. Colourless oil;
1H NMR (300.1 MHz, CDCl3): d 1.51 (d, J = 6.0 Hz, 3H),
2.00 (s, 3H), 3.45 (m, 1H), 5.31 (d, J = 5.7 Hz, 1H), 7.26–7.35
1-Pentafluorophenyl-2-oxopropyl benzoate 2g. Orange oil;
1H NMR (300.1 MHz, CDCl3): d 2.43 (s, 3H), 6.68 (s, 1H),
7.48–7.53 (m, 2H), 7.63–7.68 (m, 1H), 8.10–8.13 (m, 2H)
1
(m, 5H), 7.47–7.65 (m, 3H), 8.10 (m, 2H) ppm; 13C{ H} NMR
1
ppm; 13C{ H} NMR (75.47 MHz, CDCl3): d 26.4, 70.3, 109.8
(75.47 MHz, CDCl3): d 16.1, 27.9, 41.2, 82.8, 127.7, 127.8, 128.4,
(m), 128.5, 128.7, 130.2, 134.1, 134.2, 135.8-147.3 (m), 164.9,
200.1 ppm; 19F NMR (282.4 MHz, CDCl3): d -160.8 (m, 2F),
128.5, 128.7, 129.8, 133.5, 141.3, 166.0, 205.6 ppm; IR (neat):
-1
=
n 1721 and 1743 (C O) cm ; GC-MS (EI, 70eV): m/z 239
-151.2 (t, J = 22.0 Hz, 1F), -136.6 (m, 2F) ppm; IR (neat):
(1%, M+ - MeCO), 161 (15), 105 (100), 77 (25); HRMS (ESI-
TOF): m/z 283.133276 [M+ + H], C18H19O3 requires 283.133420.
-1
=
n 1712 and 1731 (C O) cm ; GC-MS (EI, 70eV): m/z 344
(1%, M+), 301 (30), 105 (100), 77 (25); HRMS (ESI-TOF): m/z
345.054946 [M+ + H], C16H10F5O3 requires 345.055011.
1
1-Acetyl-cycloheptyl benzoate 2s. Colourless oil; H NMR
(300.1 MHz, CDCl3): d 1.58–1.64 (m, 7H), 2.08–2.16 (m, 3H),
1-(2-Methoxyphenyl)-2-oxopropyl benzoate 2h. Colourless
oil; 1H NMR (300.1 MHz, CDCl3): d 2.20 (s, 3H), 3.92 (s, 3H),
6.70 (s, 1H), 6.87–7.02 (m, 4H), 7.28–7.62 (m, 3H), 8.09–8.14
2.12 (s, 3H), 2.23–2.33 (m, 2H), 7.44–7.62 (m, 3H), 8.05 (m, 2H)
1
ppm; 13C{ H} NMR (75.47 MHz, CDCl3): d 21.3, 23.6, 24.8,
27.7, 29.3, 89.3, 128.4, 129.7, 129.8, 133.3, 165.5, 206.9 ppm;
1
(m, 2H) ppm; 13C{ H} NMR (75.47 MHz, CDCl3): d 26.3, 55.6,
-1
=
IR (neat): n 1716 (br, C O) cm ; GC-MS (EI, 70eV): m/z 231
75.2, 111.1, 120.6, 121.1, 128.3, 128.4, 129.4, 129.9, 133.1, 133.7,
(5%, M+ - 2CH2), 105 (100), 77 (20); HRMS (ESI-TOF): m/z
-1
=
156.9, 171.7, 202.1 ppm; IR (neat): n 1683 and 1716 (C O) cm ;
261.148865 [M+ + H], C16H21O3 requires 261.149070.
GC-MS (EI, 70eV): m/z 284 (1%, M+), 241 (10), 105 (100), 77
(30); HRMS (ESI-TOF): m/z 285.112721 [M+ + H], C17H17O4
requires 285.112684.
1
2-Acetyl-adamantan-2-yl benzoate 2t. Yellow oil; H NMR
(300.1 MHz, CDCl3): d 1.70–1.91 (m, 8H), 2.13 (s, 3H), 2.22
(m, 4H), 2.57 (br, 2H), 7.47–7.64 (m, 3H), 8.10 (d, J = 7.2 Hz,
1-(3-Methoxyphenyl)-2-oxopropyl benzoate 2i. Colourless
oil; 1H NMR (300.1 MHz, CDCl3): d 2.21 (s, 3H), 3.84 (s, 3H),
6.18 (s, 1H), 6.94–7.12 (m, 4H), 7.35–7.61 (m, 3H), 8.11–8.14
1
2H) ppm; 13C{ H} NMR (75.47 MHz, CDCl3): d 24.1, 26.8,
26.9, 32.6, 33.7, 33.9, 37.7, 88.8, 128.6, 129.8, 130.0, 133.4,
-1
1
(m, 2H) ppm; 13C{ H} NMR (75.47 MHz, CDCl3): d 25.9, 55.3,
=
165.2, 205.9 ppm; IR (neat): n 1673 and 1722 (C O) cm ;
GC-MS (EI, 70eV): m/z 255 (20%, M+ - MeCO), 105 (100), 77
(30); HRMS (ESI-TOF): m/z 299.164630 [M+ + H], C19H23O3
requires 299.164720.
81.1, 113.4, 114.7, 120.2, 128.4, 129.2, 129.9, 130.1, 133.4, 133.7,
-1
=
159.9, 165.7, 201.7 ppm; IR (neat): n 1704 and 1732 (C O) cm ;
GC-MS (EI, 70eV): m/z 284 (1%, M+), 241 (10), 105 (100), 77
(30); HRMS (ESI-TOF): m/z 285.112563 [M+ + H], C17H17O4
requires 285.112684.
1-Phenyl-2-oxopropyl 2-chlorobenzoate 9a. Pale yellow oil;
1H NMR (300.1 MHz, CDCl3): d 2.21 (s, 3H), 6.22 (s, 1H), 7.31–
1
1-(4-Methoxyphenyl)-2-oxopropyl benzoate 2j. Colourless
oil; 1H NMR (300.1 MHz, CDCl3): d 2.19 (s, 3H), 3.86 (s,
3H), 6.17 (s, 1H), 6.82–7.11 (m, 4H), 7.43–7.64 (m, 3H), 8.09–
7.54 (m, 8H), 8.00 (m, 1H) ppm; 13C{ H} NMR (75.47 MHz,
CDCl3): d 25.7, 81.3, 126.2, 127.6, 128.4, 128.7, 129.0, 130.7,
131.6, 132.5, 132.7, 133.8, 164.2, 200.9 ppm; IR (neat): n 1738
1
-1
+
8.14 (m, 2H) ppm; 13C{ H} NMR (75.47 MHz, CDCl3): d 25.6,
(br, C O) cm ; GC-MS (EI, 70eV): m/z 245 (10%, M
-
=
55.1, 80.7, 114.0, 127.9, 129.1, 129.6, 129.8, 133.0, 133.6, 159.9,
COMe), 139 (100), 111 (20), 75 (15); HRMS (ESI-TOF): m/z
-1
=
171.9, 201.7 ppm; IR (neat): n 1709 and 1738 (C O) cm ;
289.063188 [M+ + H], C16H14O3Cl requires 289.063147.
140 | Green Chem., 2010, 12, 135–143
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1-Phenyl-2-oxopropyl 2-bromo-5-methoxybenzoate 9b. Or-
ange oil; H NMR (300.1 MHz, CDCl3): d 2.22 (s, 3H), 3.84
1-Phenyl-2-oxopropyl tetrahydrofuran-2-carboxylate 9h. Or-
ange oil; H NMR (300.1 MHz, CDCl3): d 1.89–2.04 (m, 2H),
1
1
(s, 3H), 6.22 (s, 1H), 6.92 (dd, J = 8.7 and 3.1 Hz, 1H), 7.43–
2.15 (s, 3H), 2.26–2.40 (m, 2H), 3.92–4.11 (m, 2H), 4.59–4.67 (m,
1
1
7.58 (m, 7H) ppm; 13C{ H} NMR (75.47 MHz, CDCl3): d 26.2,
1H), 6.03 (s, 1H), 7.42 (br, 5H) ppm; 13C{ H} NMR (75.47 MHz,
55.7, 81.9, 112.3, 117.2, 119.2, 128.1, 129.1, 129.5, 131.6, 132.8,
CDCl3): d 25.1, 26.2, 30.3, 69.5, 76.3, 80.9, 128.2, 129.1, 129.4,
-1
-1
=
=
135.2, 158.6, 165.1, 201.2 ppm; IR (neat): n 1730 (br, C O) cm ;
132.9, 172.8, 201.1 ppm; IR (neat): n 1731 and 1755 (C O) cm ;
GC-MS (EI, 70eV): m/z 364 (3%, M+), 321 (10), 213 (100), 187
(10), 170 (10); HRMS (ESI-TOF): m/z 363.023211 [M+ + H],
C17H16O4Br requires 363.023202.
GC-MS (EI, 70eV): m/z 205 (5%, M+ - MeCO), 177 (10), 105
(10), 71 (100), 43 (50); HRMS (ESI-TOF): m/z 249.112745 [M+
+ H], C14H17O4 requires 249.112692.
1-Phenyl-2-oxopropyl 3-bromo-5-iodobenzoate 9c. Orange
oil; 1H NMR (300.1 MHz, CDCl3): d 2.19 (s, 3H), 6.21 (s, 1H),
7.46–7.53 (m, 5H), 8.07 (dd, J = 1.7 and 1.7 Hz, 1H), 8.19
(dd, J = 1.7 and 1.7 Hz, 1H), 8.35 (dd, J = 1.7 and 1.7 Hz,
1-Phenyl-2-oxopropyl 1H-pyrrole-2-carboxylate 9i. Brown
oil; 1H NMR (300.1 MHz, CDCl3): d 2.20 (s, 3H), 6.16 (s, 1H),
6.31 (dd, J = 6.5 and 2.8 Hz, 1H), 7.00–7.09 (m, 2H), 7.42–7.53
1
(m, 5H), 9.24 (br, 1H) ppm; 13C{ H} NMR (75.47 MHz, CDCl3):
1
1H) ppm; 13C{ H} NMR (75.47 MHz, CDCl3): d 26.2, 81.8,
d 26.0, 80.6, 110.7, 116.5, 123.7, 127.9, 128.1, 128.7, 129.3, 133.5,
-1
94.0, 123.0, 128.2, 129.3, 129.7, 132.1, 132.4, 132.6, 137.3, 144.2,
=
160.0, 202.3 ppm; IR (nujol): n 1732 (br, C O), 3315 (NH) cm ;
-1
GC-MS (EI, 70eV): m/z 200 (20%, M+ - MeCO), 94 (100), 66
(20), 39 (20); HRMS (ESI-TOF): m/z 244.097459 [M+ + H],
C14H14O3N requires 244.097378.
=
163.1, 200.6 ppm; IR (neat): n 1716 and 1738 (C O) cm ; GC-
MS (EI, 70eV): m/z 415 (20%, M+ - MeCO), 309 (100), 281 (15),
182 (10), 156 (15); HRMS (ESI-TOF): m/z 458.909398 [M+ +
H], C16H13O3BrI requires 458.909284.
1-Phenyl-2-oxopropyl thiophene-2-carboxylate 9j. Red oil;
1H NMR (300.1 MHz, CDCl3): d 2.21 (s, 3H), 6.18 (s, 1H),
7.34 (dd, J = 5.1 and 3.1 Hz, 1H), 7.43-7.55 (m, 5H), 7.60 (dd,
J = 5.1 and 1.1 Hz, 1H), 8.24 (dd, J = 3.1 and 1.1 Hz, 1H)
1-Phenyl-2-oxopropyl pentafluorobenzoate 9d. Orange oil;
1H NMR (300.1 MHz, CDCl3): d 2.18 (s, 3H), 6.23 (s, 1H), 7.42-
1
7.54 (m, 5H) ppm; 13C{ H} NMR (75.47 MHz, CDCl3): d 28.0,
84.7, 130.0, 130.7-134.1 (m), 138.2-149.7 (m), 160.3, 201.9 ppm;
1
ppm; 13C{ H} NMR (75.47 MHz, CDCl3): d 26.1, 81.0, 126.3,
19F NMR (282.4 MHz, CDCl3): d -160.1 (m, 2F), -147.2 (m,
127.9, 128.0, 129.1, 129.4, 132.6, 133.4, 133.8, 161.8, 201.8 ppm;
-1
=
1F), -136.6 (m, 2F) ppm; IR (neat): n 1739 (br, C O) cm ;
-1
=
IR (nujol): n 1719 (br, C O) cm ; GC-MS (EI, 70eV): m/z 217
GC-MS (EI, 70eV): m/z 301 (20%, M+ - MeCO), 195 (100), 167
(10), 117 (5), 105 (5); HRMS (ESI-TOF): m/z 345.055126 [M+
+ H], C16H10F5O3 requires 345.055013.
(20%, M+ - MeCO), 111 (100), 83 (15), 39 (20); HRMS (ESI-
TOF): m/z 261.05846 [M+ + H], C14H13O3S requires 261.058541.
1-Phenyl-2-oxopropyl 3-(1H-indol-3-yl)propionate 9k. Or-
ange oil; H NMR (300.1 MHz, CDCl3): d 2.09 (s, 3H), 2.28
1
1-Phenyl-2-oxopropyl 4-benzoylbenzoate 9e. Yellow oil; H
1
NMR (300.1 MHz, CDCl3): d 2.23 (s, 3H), 6.26 (s, 1H), 7.46–
7.66 (m, 8H), 7.81–7.88 (m, 4H), 8.24 (d, J = 8.3 Hz, 2H) ppm;
(m, 2H), 3.17 (t, J = 7.3 Hz, 2H), 5.99 (s, 1H), 7.09-7.39 (m,
1
9H), 7.60 (d, J = 7.9 Hz, 1H), 7.97 (br, 1H) ppm; 13C{ H} NMR
13C{ H} NMR (75.47 MHz, CDCl3): d 26.2, 81.6, 128.1, 128.5,
1
(75.47 MHz, CDCl3): d 20.9, 26.4, 35.0, 81.3, 111.5, 115.1, 119.0,
129.2, 129.6, 129.8, 130.1, 132.3, 133.0, 133.1, 136.9, 141.8,
119.7, 121.9, 122.5, 127.8, 128.4, 129.5, 129.7, 133.7, 136.7,
165.1, 195.9, 201.2 ppm; IR (neat): n 1667, 1717 and 1738
=
173.0, 202.3 ppm; IR (nujol): n 1716 and 1738 (C O), 3412
-1
+
=
(C O) cm ; GC-MS (EI, 70eV): m/z 315 (10%, M - MeCO),
252 (5), 209 (100), 152 (10), 105 (20); HRMS (ESI-TOF): m/z
359.128577 [M+ + H], C23H19O4 requires 359.128334.
(NH) cm-1; GC-MS (EI, 70eV): m/z 321 (20%, M+), 188 (10),
146 (10), 130 (100), 105 (10), 77 (10); HRMS (ESI-TOF): m/z
322.144280 [M+ + H], C20H20O3N requires 322.144319.
1-Phenyl-2-oxopropyl 2-chloro-5-sulfamoylbenzoate 9f. Yel-
low solid; H NMR (300.1 MHz, CDCl3): d 2.16 (s, 3H), 5.44
1
1-Phenyl-2-oxopropyl
(5-methoxy-2-methyl-1H-indol-3-
1
yl)acetate 9l. Yellow oil; H NMR (300.1 MHz, CDCl3): d
2.04 (s, 3H), 2.38 (s, 3H), 3.80 (s, 3H), 3.83 (s, 2H), 5.97 (s, 1H),
6.77 (dd, J = 8.7 and 2.5 Hz, 1H), 7.01 (d, J = 2.5 Hz, 1H), 7.13
(br, 2H), 6.22 (s, 1H), 7.43–7.59 (m, 6H), 8.16 (dd, J = 8.3 and
1
2.1 Hz, 1H), 8.73 (d, J = 2.1 Hz, 1H) ppm; 13C{ H} NMR
(75.47 MHz, CDCl3): d 26.6, 82.4, 128.6, 129.1, 129.7, 130.2,
(d, J = 8.7 Hz, 1H), 7.39 (br, 5H), 7.82 (br, 1H) ppm; 13C{ H}
1
131.3, 132.4, 132.9, 134.9, 137.0, 140.5, 164.1, 201.4 ppm; IR
-1
NMR (75.47 MHz, CDCl3): d 11.8, 25.9, 30.1, 55.8, 81.1, 100.2,
=
(nujol): n 1714 (br, C O), 3390 (N–H) cm ; GC-MS (EI, 70eV):
m/z 324 (15%, M+ - MeCO), 218 (100), 138 (10), 105 (15), 77
(20); Elemental analysis calcd (%) for C16H14O5ClNS: C 52.25,
H 3.84, N 3.81; found: C 52.33, H 3.96, N 3.70.
103.9, 111.0, 111.2, 127.9, 128.9, 129.0, 129.2, 130.1, 133.3,
=
133.7, 154.2, 171.2, 202.0 ppm; IR (nujol): n 1719 (br, C O),
3391 (NH) cm-1; GC-MS (EI, 70eV): m/z 351 (30%, M+), 174
(100), 158 (15), 131 (15), 105 (10), 77 (10); HRMS (ESI-TOF):
m/z 352.154709 [M+ + H], C21H22O4N requires 352.154883.
1-Phenyl-2-oxopropyl 4-(4-chlorophenoxy)benzoate 9g. Yel-
1
low oil; H NMR (300.1 MHz, CDCl3): d 2.21 (s, 3H), 6.22
(s, 1H), 7.01 (m, 4H), 7.34–7.55 (m, 7H), 8.11 (m, 2H) ppm;
1-Phenyl-2-oxopropyl 2-oxo-2H-chromene-3-carboxylate 9m.
Orange oil; 1H NMR (300.1 MHz, CDCl3): d 2.20 (s, 3H), 6.21
1
13C{ H} NMR (75.47 MHz, CDCl3): d 26.1, 81.3, 117.5, 121.3,
1
124.0, 128.0, 129.1, 129.4, 130.1, 132.2, 133.4, 154.2, 161.8,
(s, 1H), 7.26–7.65 (m, 9H), 8.62 (s, 1H) ppm; 13C{ H} NMR
-1
=
165.2, 201.8 ppm; IR (neat): n 1715 (br, C O) cm ; GC-MS
(75.47 MHz, CDCl3): d 26.0, 81.7, 116.7, 117.0, 117.7, 124.9,
(EI, 70eV): m/z 337 (5%, M+ - MeCO), 231 (100), 168 (15), 139
(10), 105 (10); HRMS (ESI-TOF): m/z 381.089428 [M+ + H],
C22H18O4Cl requires 381.089363.
127.9, 129.1, 129.4, 129.7, 132.8, 134.7, 149.5, 155.2, 156.3,
-1
=
162.0, 201.4 ppm; IR (nujol): n 1713 (br, C O) cm ; GC-MS
(EI, 70eV): m/z 280 (10%, M+ - MeCO), 216 (10), 173 (100),
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146 (20), 105 (15), 89 (20); HRMS (ESI-TOF): m/z 323.092216
9 (a) D. Devanne, C. Ruppin and P. H. Dixneuf, J. Org. Chem., 1988,
53, 925; (b) S. Costin, N. P. Rath and E. B. Bauer, Adv. Synth. Catal.,
2008, 350, 2414.
[M+ + H], C19H15O5 requires 323.091949.
10 (a) C. Bruneau, Z. Kabouche, M. Neveux, B. Seiller and P. H.
Dixneuf, Inorg. Chim. Acta, 1994, 222, 155; (b) C. Darcel, C. Bruneau,
P. H. Dixneuf and G. Neef, J. Chem. Soc., Chem. Commun., 1994,
333.
1
1-Phenyl-2-oxopropyl heptanoate 9n. Yellow oil; H NMR
(300.1 MHz, CDCl3): d 0.87 (t, J = 6.9 Hz, 3H), 1.25–1.38 (m,
6H), 1.66 (m, 2H), 2.11 (s, 3H), 2.41 (m, 2H), 5.97 (s, 1H), 7.37–
7.42 (m, 5H) ppm; 13C{ H} NMR (75.47 MHz, CDCl3): d 14.0,
1
11 T. Mitsudo, Y. Hori, Y. Yamakawa and Y. Watanabe, J. Org. Chem.,
1987, 52, 2230.
22.4, 24.7, 26.1, 28.6, 31.3, 33.9, 80.7, 127.9, 129.0, 129.3, 133.3,
12 For general reviews on metal-catalyzed addition of heteroatom-
hydrogen bonds to alkynes, see: (a) F. Alonso, I. P. Beletskaya and M.
Yus, Chem. Rev., 2004, 104, 3079; (b) M. Beller, J. Seayad, A. Tillack
and H. Jiao, Angew. Chem., Int. Ed., 2004, 43, 3368.
-1
=
173.1, 201.8 ppm; IR (neat): n 1734 (br, C O) cm ; GC-MS
(EI, 70eV): m/z 219 (20%, M+ - MeCO), 134 (10), 113 (100),
105 (20), 85 (15), 77 (10); HRMS (ESI-TOF): m/z 263.164689
[M+ + H], C16H23O3 requires 263.164725.
13 For specific accounts covering the use ruthenium catalysts in this
type of transformations, see: (a) C. Bruneau, M. Neveux, Z.
Kabouche, C. Ruppin and P. H. Dixneuf, Synlett, 1991, 755; (b) C.
Fischmeister, C. Bruneau, and P. H. Dixneuf, in Ruthenium in
Organic Synthesis, ed. S.-I. Murahashi, Wiley-VCH, Weinheim, 2004,
pp.189-217.
14 See, for example: (a) P. T. Anastas, and J. C. Warner, in Green
Chemistry: Theory and Practice, Oxford University Press, Oxford,
1998; (b) A. S. Matlack, in Introduction to Green Chemistry, Marcel
Dekker, New York, 2001; (c) M. Lancaster, in Handbook of Green
Chemistry and Technology, eds. J. H. Clark, and D. J. Macquar-
rie, Blackwell Publishing, Abingdon, 2002; (d) M. Lancaster, in
Green Chemistry: An Introductory Text, RSC Editions, London,
2002.
1-Phenyl-2-oxopropyl 3-cyclopentylpropionate 9o. Yellow
oil; 1H NMR (300.1 MHz, CDCl3): d 1.10–1.89 (m, 11H), 2.11
(s, 3H), 2.47 (m, 2H), 5.97 (s, 1H), 7.40 (br, 5H) ppm; 13C{ H}
1
NMR (75.47 MHz, CDCl3): d 24.6, 25.7, 30.5, 31.9, 32.8, 39.1,
80.3, 127.6, 128.6, 128.8, 132.8, 172.7, 201.4 ppm; IR (neat): n
-1
+
=
1768 (br, C O) cm ; GC-MS (EI, 70eV): m/z 274 (2%, M ), 231
(40), 134 (10), 125 (100), 107 (60), 97 (10), 79 (50); HRMS (ESI-
TOF): m/z 275.164641 [M+ + H], C17H23O3 requires 275.164724.
15 See, for example: (a) W. M. Nelson, in Green Solvents for Chemistry:
Perspectives and Practice, Oxford University Press, New York, 2003;
(b) J. H. Clark and S. J. Taverner, Org. Process Res. Dev., 2007, 11,
149; (c) F. M. Kerton, in Alternative Solvents for Green Chemistry,
RSC Publishing, Cambridge, 2009.
Acknowledgements
This work was supported by the Ministerio de Educacio´n y
Ciencia (MEC) of Spain (Projects CTQ2006-08485/BQU and
Consolider Ingenio 2010 (CSD2007-00006)) and the Gobierno
del Principado de Asturias (FICYT Project IB08-036). J.F.
thanks MEC and the European Social Fund for the award of a
PhD grant.
16 See, for example: (a) C. J. Li, Chem. Rev., 1993, 93, 2023; (b) A.
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142 | Green Chem., 2010, 12, 135–143
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19 The abbreviations used for the hydrosoluble phosphines corre-
spond to the following IUPAC names: PTA = 1,3,5-triaza-7-
phosphatricyclo[3.3.1.13,7]decane; PTA-Bn = 1-benzyl-3,5-diaza-1-
azonia-7-phosphatricyclo[3.3.1.13,7]decane chloride; DAPTA = 3,7-
diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane; TPPMS = 3-
diphenylphosphanyl-benzenesulfonate sodium salt.
25 Addition of carboxylic acids to ethisterone and mestranol
could be successfully achieved in organic media using [{Ru(m-
O2CH)(CO)2(PPh3)}2] as catalyst: see ref. 10b.
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6601.
21 As observed in our previous work on nitrile hydrations using
catalysts 3a–6d, no direct relationship between the solubility of these
complexes in water and their catalytic activity exists. Detailed data
about the solubility of 3a–6d in water at 20 ◦C can be found in ref.
20.
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29 (a) M. M. Midland, J. Org. Chem., 1975, 40, 2250; (b) The secondary
propargylic alcohol 1-pentafluorophenyl-2-propyn-1-ol 1g, isolated
as a yellow oil in 78% yield, has not been previously described.
Characterization data for this new compound are as follows: 1H
NMR (300.1 MHz, CDCl3):d 2.66 (d, J = 2.4 Hz, 1H), 3.75 (br, 1H),
1
5.76 (d, J = 2.4 Hz, 1H) ppm; 13C{ H} NMR (75.47 MHz, CDCl3):
d 54.3, 74.8, 80.1, 114.1 (m), 135.7 (m), 139.6 (m), 143.3 (m) ppm;
19F NMR (282.4 MHz, CDCl3): d -161.7 (m, 2F), -153.8 (m, 1F),
≡
23 For specific examples of Ru-allenylidene Ca=Cb bond cleavage by
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-143.6 (m, 2F) ppm; IR (neat): n 2127 (C C), 3309 (br, OH and
∫C–H) cm-1; GC-MS (EI, 70eV): m/z 222 (30%, M+), 203 (70) 194
(100), 174 (50), 143 (20), 117 (20), 99 (15), 53 (20).
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32 M. B. Rubin and S. Inbar, J. Org. Chem., 1988, 53, 3355.
≡
24 Ruthenium-catalyzed cleavage of the C C bond of propargylic
alcohols to generate the corresponding alkenes and carbon monoxide
has been described by R.-S. Liu, and co-workers: (a) S. Datta,
C.-L. Chang, K.-L. Yeh and R.-S. Liu, J. Am. Chem. Soc., 2003,
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300.
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The Royal Society of Chemistry 2010
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©