Sonogashira cross-coupling of 3-bromo-1,2-diones: An access to 3-alkynyl-1,2-diones

Article abstract of DOI:10.1016/j.tet.2014.06.037

A new general method for the synthesis of enols of cyclic 3-alkynyl-substituted 1,2-diketones is developed. Sonogashira cross-coupling of silyl enolates of cyclic 3-bromo-cyclopentane- and 3-bromo-cyclohexane-1,2-diones with variety of substituted acetylenes afforded enols of cyclic 3-alkynyl-1,2-diones with good yields (up to 93%) in a short reaction time. The starting 3-bromo-1,2-diones are easily obtainable by direct bromination of 1,2-diones with NBS.

Full text of DOI:10.1016/j.tet.2014.06.037

Accepted Manuscript
Sonagashira cross-coupling of 3-bromo-1,2-diones: an access to 3-alkynyl-1,2-diones
Anne Paju, Tõnis Kanger, Aleksander-Mati Müürisepp, Tiina Aid, Tõnis Pehk, Margus
Lopp
PII:
S0040-4020(14)00897-7
10.1016/j.tet.2014.06.037
TET 25703
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 31 March 2014
Revised Date: 28 May 2014
Accepted Date: 10 June 2014
Please cite this article as: Paju A, Kanger T, Müürisepp A-M, Aid T, Pehk T, Lopp M, Sonagashira cross-
coupling of 3-bromo-1,2-diones: an access to 3-alkynyl-1,2-diones, Tetrahedron (2014), doi: 10.1016/
j.tet.2014.06.037.
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a
a
a
a
b
a
Anne Paju , Tõnis Kanger , Aleksander-Mati Müürisepp , Tiina Aid , Tõnis Pehk and Margus Lopp *
a
Department of Chemistry, Tallinn University of Technology, Akadeemia tee 15, 12618 Tallinn, Estonia
National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, 12618 Tallinn, Estonia
b

1
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Tetrahedron
journal homepage: www.elsevier.com
Sonagashira cross-coupling of 3-bromo-1,2-diones: an access to 3-alkynyl-1,2-diones
a
a
a
a
b
a
Anne Paju , Tõnis Kanger , Aleksander-Mati Müürisepp , Tiina Aid , Tõnis Pehk and Margus Lopp *
a
Department of Chemistry, Tallinn University of Technology, Akadeemia tee 15, 12618 Tallinn, Estonia
National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, 12618 Tallinn, Estonia
b
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
A new general method for the synthesis of enols of cyclic 3-
alkynyl-substituted 1,2-diketones is developed. Sonogashira
cross-coupling of silyl enolates of cyclic 3-bromo-
cyclopentane- and 3-bromo-cyclohexane-1,2-diones with
variety of substituted acetylenes afforded enols of cyclic 3-
alkynyl-1,2-diones with good yields (up to 93%) in a short
reaction time. The starting 3-bromo-1,2-diones are easily
obtainable by direct bromination of 1,2-diones with NBS.
Available online
Keywords:
Sonagashira cross-coupling
2
009 Elsevier Ltd. All rights reserved.
3
3
-bromo-1,2-dione
-alkynyl-1,2-dione
6
1
. Introduction
1,4-naphthoquinone-3-halides by Sonagashira coupling, bromine
7
replacement in 3-bromoisotetronic acid by Suzuki coupling and
-triflate replacement in 2-arylchromones by Stille coupling.
Cross-coupling reactions are among the most frequently used1
8
3
tools for creating new C-C bonds of organic molecule skeletons.
Vinyl halides and other functionalized alkenes are the common
substrates for these transformations. Thus, the vinylic α- and β-
leaving groups (halide, triflate etc) at the double bond of α,β-
unsaturated carbonyl compounds can be replaced by alkyl,
alkenyl, alkynyl or aryl groups. There are some examples in the
literature of the replacement of enol ester groups and 2-halides of
enol ethers of ketones by the cross-coupling reaction. Also, there
LG-substituted enolates of 1,2-diketones have not been used
as the substrates in cross-coupling reactions, although 3-
substituted 1,2-dicarbonyl compounds are useful intermediates
9
for the synthesis of different valuable compounds. To find a
2
simple approach to 3-substituted 1,2-diketones a possibility to
use the enolate of 3-LG-1,2-diketone as substrate for cross-
coupling reaction needs to be investigated. (Scheme 1)
3
are references on the substitution of 2-halides (Br, I) of enol
ethers of 1,3-dicarbonyl compounds by alkynyl groups in
Sonogashira coupling.
We decided first to study Sonagashira coupling of 3-bromo-
cyclopentane- and cyclohexane-1,2-diones with alkynes in order
to prepare cyclic 3-alkynyl-substituted 1,2-diones. These
compounds are very rare: there is only one reference on the
formation of 3-alkynylcyclopentane-1,2-diones by Au-catalyzed
4
2g
a common
R''
Nazarov cyclization.
3-Alkynyl-cyclohexane-1,2-diketones
coupling reaction
R''
R
O
R
have not been described in literature so far.
LG
R
R'
R'
O
O
O
O
OH
OR
LG
OR
OH
O
coupling reaction
R
R
LG
LG
Scheme 1. Cross-coupling reaction of generated from 1,2-
diketones vinylic compounds to form 3-substituted 1,2-
dicarbonyl compounds.
To the best of our knowledge, there are only a few specific
references on the cross-coupling reactions of enol ethers of 1,2-
dicarbonyl compounds having leaving groups (LG) in position 3:
iodine replacement in 2-hydroxy-3-iodo-1,4-naphthoquinone by
Scheme 2. Sonogashira cross-coupling reaction of cyclic 3-bromo-1,2-
dicarbonyl compounds.
5
Heck reaction, bromine and iodine replacement in 2-hydroxy-

2
Tetrahedron
ACCEPTED MANUSCRIPT
2
. Results and Discussion
coupling reaction. Therefore both, enols (1, 3) and tert-
butyldimethylsilyl enolates (2, 4), were prepared. The enol
hydroxyl group was converted to tert-butyldimethylsilyl enol
ether 2 in 90% yield. 1,2-Cyclohexanedione 10 was brominated
with NBS in a 4:1 mixture of CH Cl -MeOH. The isolated yield
In the present work Sonagashira coupling of the enolate of 3-
bromo-cyclopentane-1,2-dione 1, of silyl enolate of 3-bromo-
cyclopentane-1,2-dione 2 and of silyl enolate of 3-bromo-
cyclohexane-1,2-dione 4 with acetylenic compounds 11 was
studied (Scheme 2).
2
2
of 3-bromo cylohexane-1,2-dione enol derivative 4 was slightly
lower: 62% for two steps. (Scheme 3).
The substrate for coupling, 3-bromoenol 1, had been
previously prepared by bromination of cylcopentanone with Br
2
10
followed by hydrolysis in 47% yield in two steps. Bromoenol 3
was prepared from 2-bromo-cyclohexanone by α-oxidation with
11
DMSO in 34% yield, and by a direct bromination of 1,2-
11,12
cyclohexanedione in up to 90% yield.
We prepared 3-bromo
enol 1 by direct bromination of dione 9 with NBS in a 4:1
mixture of acetone-water, in 89% yield, using a slightly modified
13
procedure for the halogenation of vinylic ethers. Protection of
the enol hydroxyl group might not be necessary for the cross-
Scheme 3. Synthesis of cyclic 3-bromo-1,2-diones.
Table 1. Investigation of reaction conditions for the cross-coupling reaction.
No
Substrate
Alkyne
Catalyst (5 mol%)
THF/Et N
(molar ratio)
Temp
reflux
Time h
1
Yield %
3
1
1
6
a
1
1
a (2)
Pd(PPh ) Cl /CuI
Et N
3
13
3
2
2
b
2
3
1
2
b (3)
a (2)
Pd(PPh3)4
Et N
reflux
reflux
3
1
15
3
Pd(PPh) Cl /CuI
Et N
3
90
83
3
2
4
2
b (3)
Pd(PPh) Cl /CuI
Et N
3
reflux
1
3
2
5
6
2
2
a (2)
a (2)
Pd(PPh ) Cl /CuI
THF/Et N
rt
24
1
28
79
3
2
2
3
(3.6/1)
Pd(PPh ) Cl /CuI
THF/Et N
reflux
3
2
2
3
(3.6/1)
7
8
2
2
a (2)
b (2)
Pd(PPh ) Cl /CuI
Et N
rt
rt
21
24
7
3
2
2
3
Pd(PPh ) Cl /CuI
THF/Et N
85
3
2
2
3
(3.6/1)
9
2
2
2
b (3)
a (2)
a (2)
Pd(PPh3)4
Et N
reflux
reflux
reflux
1
1
1
54
83
88
3
1
0
1
Pd(PPh ) OAc /CuI
Et N
3
3
2
2
1
Pd(PPh ) /CuI
Et N
3
3
4
a
33% of enol 9 was isolated
b
2
0% of enol 9 was isolated
In order to find optimal conditions for Sonogashira cross-
4). Therefore, in the following experiments only protected
substrates 2 and 4 were used in cross-coupling experiments.
14
coupling of cyclic 3-bromo-1,2-diones its reaction with
acetylenic compounds 11a and 11b was investigated (Table 1).
Phenylacetylene 11a and trimethylsilylacetylene 11b with
unprotected substrate 1 gave a low yield of acetylenic compound
The presence of a base is essential for the cross-coupling
14
reaction. The most common bases are secondary and tertiary
amines and carbonates of alkali metals. In many cases, the bases
5
(13% for 5a and 15% for 5b, Table 1, entries 1 and 2; 5 mol%
14,15
(e.g. amines) also acts as reaction media.
When using a
of Pd(PPh ) Cl , in the presence of 5 mol% of CuI for 11a, and of
3
2
2
mixture of THF/Et N, we found that the yield of the reaction
3
5
mol% of Pd(PPh ) for 11b). Always, a considerable amount of
3 4
reduction product 9 (33% and 20%, correspondingly) was
isolated. At the same time, the bromide of silyl enol ether 2
depended only slightly on the Et N and THF ratio (Table 1,
3
entries 3 and 6 for 11a; 4 and 8 for 11b). The reaction
temperature had a significant effect on the yield: at room
temperature even in long reaction times, the yields of coupling
for 11a remained low (Table 1, entries 5 and 7). Alkyne 11b is
more reactive at room temperature, so the temperature increase
reacted
smoothly
with
phenylacetylene
11a
and
trimethylsilylacetylene 11b in the same reaction conditions,
affording 6a in 90% and 6b in 83% yield (Table 1, entries 3 and

3
did not have a notable effect on the yield, but only had an effect
on the reaction rate (Table 1, entry 4 and 8). Stable yields for
TBS group is both, acid- and base-sensitive and acetylenic and
ACCEPTED MANUSCRIPT
propargylic TBS groups have different sensitivities to acid. For
silyl acetylene 6b mono-desilylation was achieved in acidic
conditions with 3M HCl in THF, affording silyl acetylene
derivative 5b in 72% yield. For 6c a selective mono-desilylation
of the enol ether moiety succeeded only by using basic treatment
with K CO /MeOH, affording mono silyl derivative 5c in 82%
both reagents, 11a and 11b, were obtained by using boiling Et N
3
as a reaction medium. Although a boiling mixture of THF/Et N
3
afforded a similar yield of the products (Table 1, entry 6), in the
following experiments Et N at reflux was used (Table 1, entries
3
3
, 4, 9-11; all entries of Table 2).
2
3
yield, while in acidic conditions both silyl groups cleaved.
Scheme 4).
(
Table 2. Cross-coupling reaction of cyclic 3-bromo-1,2-
diketones with alkynes.
No
Substrate
11 (eq)
Product
Yield %
1
2
4
2
2
2
2
4
2
2
2
4
4
a (3)
a (2)
b (3)
c (3)
c (3)
d (2)
d (2)
e (3)
e (3)
f (3)
f (3)
f (3)
6a
8a
6b
6c
6c
6d
8d
6e
6e
6f
93
91
83
64
83
93
80
59
68
85
59
70
2
3
4
Scheme 4. Desilylation of silyl enol ethers.
a
5
6
7
8
3. Conclusions
A simple and efficient Sonogashira cross-coupling reaction of
cyclic 3-bromo-1,2-diketones 2 and 4 with substituted acetylenes
1
1 was developed. The protocol affords enols of 3-alkynyl-
a
9
substituted 1,2-diketones 6 and 8 in a short reaction time with
good yield. Easy access of the starting bromoenols 1 and 3 from
available compounds makes the whole approach convenient and
practical. The use of 3-bromo-1,2-diketones in other coupling
reactions is currently under study.
1
1
0
1
2
8f
a1
8f
a
3 2
Pd(PPh) Cl (10 mol%); CuI (10 mol%)
4
. Experimental section
1
13
H and C NMR spectra were recorded in deuterated solvents
on a 400 MHz spectrometer. Deuterated solvent peaks were used
as references. 2D FT methods were used for the full assignment
of H and C chemical shifts. Mass spectra were measured on a
GC-MS spectrometer using EI (70 eV). TLC was performed
using 60 F254 silica gel plates. For column chromatography 40-
The presence of copper (CuI) in a reaction medium supported the
reaction (compare Table 1, entries 4 and 9). There are many
1
13
14
different Pd sources and ligands used for Sonogashira coupling.
The most common Pd catalysts are Pd(PPh ) , Pd(PPh ) Cl and
3
4
3 2
2
Pd(PPh ) (OAc) . In our case these catalysts worked almost
3
2
2
1
00 ꢀm and 100-160 ꢀm silica gel was used. All reactions
equally well for the coupling reaction (Table 1, entries 3, 10-11).
Twofold and threefold excess of acetylenic compound 11 to
substrate 2 was found to result in stable good yields of 6.
sensitive to oxygen or moisture were conducted under argon
atmosphere in oven-dried glassware. Commercial reagents were
generally used as received. THF was distilled from LiAlH4
before use. CH Cl was distilled from CaH .
To elucidate the scope of the method different terminal alkynes
2
2
2
1
3
1 were subjected to cross-coupling reactions with protected enol
-bromides of cyclopentane- and cylohexane-1,2-diones 2 and 4
3
-Bromo-2-hydroxy-cyclopent-2-enone (1). To a solution of
1
,2-cyclopentanedione 9 (98 mg, 1 mmol) in acetone (4 mL) and
in boiling triethyl amine using Pd(PPh) Cl /CuI as a catalyst. A
3
2
water (1 mL) NBS (214 mg, 1.2 mmol) was added and the
mixture was stirred for 16 h at room temperature. Water (4 mL)
was then added, acetone was removed under reduced pressure
smooth reaction afforded 3-substituted cyclopentane- and
cylohexane-1,2-diones 6 and 8 up to 93% isolated yield, although
cyclopentane-1,2-diones 2 gave slightly better yields than the
corresponding cyclohexane substrates 4 (Table 2). The less
reactive alkynes 11c and 11e demanded higher catalyst loadings
to afford acceptable yields (Table 2, entries 5 and 9).
and the aqueous phase was extracted with CH Cl (1x8 mL and
2
2
4
x5 mL). The combined extracts were dried (Na SO ) and
2 4
concentrated. Flash chromatography (silica gel, heptanes/EtOAc
1
1
0:2) gave compound 1 as a white solid (158 mg, 89%); mp 151-
Desilylation of silyl enol ethers was performed with
ο
53 C; [Found: C, 34.02; H, 2.90. C H BrO requires C, 33.93;
5
5
2
K CO /MeOH affording enols 5 in almost quantitative yield
-1
2
3
H, 2.85]; νmax (KBr, cm ): 3205, 2921, 1703, 1657, 1372, 1301,
261, 1228, 1135, 875; δ (400 MHz, CDCl ) 6.40 (s, 1H, OH),
(96% for 5a and 94% for 7a). For the disilyl products 6b and 6c,
1
H
3
a problem of selective mono-desilylation arises because the enol-

4
Tetrahedron
2
.86-2.84 (m, 2H, H-4), 2.60-2.58 (m, 2H, H-5); δ (101 MHz,
2-(tert-Butyl-dimethyl-silanyloxy)-3-phenylethynyl-cyclopent-
ACCEPTED MANUSCRIPT
C
CDCl ) 198.7 (C-1), 151.2 (C-2), 127.8 (C-3), 33.8 (C-5), 30.0
2-enone (6a). Obtained as a white solid (87 mg, 93%); mp 103-
3
+
ο
(C-4). m/z (EI) 178 and 176, (M , 39.9 and 41.6), 97 (94.0), 69
105 C; [Found: C 73.05; H, 7.77. C H O Si requires C, 73.03;
19
24
2
-
1
(100).
H, 7.74.]. νmax (KBr, cm ): 3058, 2928, 2855, 2195, 1698, 1613,
591, 1488, 1380, 1308, 1249, 1165, 1109, 856, 788, 755, 688.
δH (400 MHz, CDCl ) 7.50-7.47 (m, 2H, o-Ph), 7.37-7.35 (m,
1
3
-Bromo-2-hydroxy-cyclohex-2-enone (3). To a solution of
3
1
,2-cyclohexanedione 10 (162 mg, 1.45 mmol) in MeOH (5.8
3
1
H, m, p-Ph), 2.68-2.65 (m, 2H, H-4), 2.44-2.42 (m, 2H, H-5),
.03 (s, 9H, C(CH ) ), 0.26 (s, 6H, Si(CH ) ); δ (101 MHz,
mL) and CH Cl (1.45 mL) NBS (310 mg, 1.74 mmol) was added
and the mixture was stirred for 3 h at room temperature. Then a
solution of Na S O (2%, 6.5 mL) was added and the mixture
was extracted with CH Cl (4x10 mL). The combined extracts
were dried (Na SO ) and concentrated. Flash chromatography
2
2
3
3
3 2
C
CDCl ) 202.9 (C-1), 155.7 (C-2), 131.8 (2C, o-Ph), 131.2 (C-3),
3
2
2
3
1
8
29.2 (1C, p-Ph), 128.6 (2C, m-Ph), 122.7 (s-Ph), 104.4 (C-2’)
4.7 (C-1’), 32.3 (C-5), 25.7 (C(CH ) ), 25.65 (C-4), 18.5
2
2
3
3
2
4
+
(
C(CH ) ), -4.0 (Si(CH ) ). m/z (EI) 297 (M −15, 1.3), 255
3 3 3 2
+
(silica gel, heptanes/EtOAc 10:1 to 10:1.5) gave compound 3 as a
(M −57, 100).
white solid (183 mg, 66%), which physical and spectroscopic
properties correspond to the literature data,
NMR spectra in Supporting information).
11,12a
1
13
(see H and
C
2-(tert-Butyl-dimethyl-silanyloxy)-3-trimethylsilanylethynyl-
cyclopent-2-enone (6b). Obtained as a white solid (77 mg, 83%);
mp 64-66 C. [Found: C 62.33; H, 9.10. C H O Si requires C,
ο
16
28
2
2
3
-Bromo-2-(tert-butyl-dimethyl-silanyloxy)-cyclopent-2-enone
2). To a solution of 3-bromocyclopentane-1,2-dione 1 (446 mg,
.52 mmol) and imidazole (343 mg, 5.04 mmol) in CH Cl (12.5
-1
6
1
2.28; H, 9.15]. νmax (KBr, cm ): 2954, 2934, 2858, 2139, 1713,
613, 1474, 1365, 1250, 1198, 1125, 845, 786, 758, 693. δ (400
(
2
H
2
2
MHz, CDCl ) 2.56-2.54 (m, 2H, H-4), 2.37-2.35 (m, 2H, H-5),
3
mL) TBDMSCl (571 mg, 3.78 mmol) was added. After stirring at
room temperature for 30 min, water (25 mL) was added, CH Cl2
layer was separated and the aqueous phase was extracted with
CH Cl (2 x 15 mL). The combined extracts were washed with
brine (15 mL), dried (Na SO ) and concentrated. The residue was
0
.98 (s, 9H, C(CH ) ), 0.22 (s, 9H, Si(CH ) ), 0.22 (s, 6H,
3 3 3 3
2
Si(CH ) ); δ (101 MHz, CDCl ) 203.2 (C-1), 156.6 (C-2), 130.7
3
2
C
3
(C-3), 111.0 (C-2’), 99.6 (C-1’) 32.2 (C-5), 25.7 (C(CH ) ), 25.5
3 3
2
2
(C-4), 18.5 (C(CH ) ), -0.16 (Si(CH ) ), -4.0 (Si(CH ) ). m/z (EI)
3
3
3 3
3 2
2
4
+
+
2
93 (M −15, 3.3), 251 (M −57, 100).
purified by flash chromatography (silica gel, heptanes/EtOAc
6
9
0:1 to 50:1) to give target compound 2 as a white solid (662 mg,
2-(tert-Butyl-dimethyl-silanyloxy)-3-[3-(tert-butyl-dimethyl-
ο
0%); mp 54-55 C; [Found: C, 45.40; H, 6.58. C H BrO Si
silanyloxy)-prop-1-ynyl-cyclopent-2-enone (6c). Obtained as a
11
19
2
ο
requires C, 45.36; H, 6.621]. δH (400 MHz, CDCl ): 2.82-2.80
white solid (95 mg, 83%); mp 86-88 C. [Found: 63.18; H, 9.50,
3
-
1
(m, 2H, H-4), 2.51-2.49 (m, 2H, H-5), 0.98 (s, 9H, C(CH ) ),
C H O Si requires C, 63.10; H, 9.53]. ν (KBr, cm ): 2930,
3
3
20 36 3 2 max
0
.22 (s, 6H, Si(CH ) ); δ (101 MHz, CDCl ) 198.6 (C-1), 151.9
2858, 1705, 1620, 1474, 1409, 1374, 1256, 1140, 1085, 849, 784.
3
2
C
3
(
C-2), 136.1 (C-3), 34.1 (C-5), 30.0 (C-4), 25.7 (C(CH ) ), 18.5
δ (400 MHz, CDCl ) 4.54 (s, 2H, H-3’), 2.56-2.54 (m, 2H, H-4),
3
3
H
3
-
1
(C(CH ) ), -3.9 (Si(CH ) ). ν
(KBr, cm ): 2929, 2859, 1706,
2.38-2.36 (m, 2H, H-5), 0.97 (s, 9H, C(CH ) ), 0.91 (s, 9H,
3
3
3 2
max
3 3
1
632, 1474, 1408, 1332, 1156, 844, 785. m/z (EI) 277 and 275,
C(CH ) ), 0.21 (s, 6H, Si(CH ) ) 0.13 (s, 6H, Si(CH ) ); δ (101
3
3
3 2
3 2
C
+
+
(M −15, 1.6 and 1.5), 235 and 233 (M −57, 100 and 99.3), 154
MHz, CDCl ) 203.1 (C-1), 155.7 (C-2), 130.9 (C-3), 103.3 (C-
3
(14.0), 139 (10.8), 137 (10.4).
2’), 79.8 (C-1’) 52.4 (C-3’) 32.2 (C-5), 25.9 (C(CH ) ), 25.7
3
3
(
(
(
C(CH ) ), 25.6 (C-4), 18.46, (C(CH ) ) 18.44, (C(CH ) ), -3.9
3 3 3 3 3 3
+
3
-Bromo-2-(tert-butyl-dimethyl-silanyloxy)-cyclohex-2-enone
4). To a solution of 3-bromocyclohexane-1,2-dione 3 (275 mg,
.44 mmol) and imidazole (196 mg, 2.88 mmol) in CH Cl (7.2
Si(CH ) ), -5.0 (Si(CH ) ). m/z (EI) 365 (M −15, 2.5), 323
3
2
3 2
(
1
+
M −57, 100).
2
2
mL) TBDMSCl (326 mg, 2.16 mmol) was added. After stirring at
room temperature for 1 h, water (15 mL) was added and the
work-up was performed as described for bromoenone 2, resulting
2-(tert-Butyl-dimethyl-silanyloxy)-3-(3-hydroxy-3-methyl-but-
1-ynyl)-cyclopent-2-enone (6d). Obtained as a white solid (82
ο
mg, 93%); mp 110-112 C. [Found: C, 65.33; H, 8.91, C H O Si
1
6
26
3
-
1
in the target compound 4 as a white solid (413 mg, 94%); mp 60-
requires C, 65.26; H, 8.90]. νmax (KBr, cm ): 2930, 3470, 2953,
2933, 2859, 2205, 1708, 1693, 1610, 1472, 1374, 1248, 1184,
1126, 958, 847, 782. δ (400 MHz, CDCl ) 2.55-2.53 (m, 2H, H-
ο
6
1 C; [Found: C, 47.25; H, 6.95. C H BrO Si requires C, 47.21;
12
21
2
-
1
H, 6.93]. νmax (KBr, cm ): 2932, 2856, 1678, 1616, 1473, 1335,
H
3
1
2
2
311, 1249, 1206, 1179, 939, 840, 783. δ (400 MHz, CDCl )
4), 2.39-2.36 (m, 2H, H-5), 2.05 (s, 1H, OH), 1.58 (s, 6H, (CH3)2,
H
3
.89 (t, J = 6.1Hz, 2H. H-4), 2.48 (dd, J = 7.4, 6.0 Hz, 2H, H-6),
.03-1.97 (m, 2H, H-5), 0.98 (s, 9H, C(CH ) ), 0.20 (s, 6H,
0.98 (s, 9H, C(CH ) ), 0.22 (s, 6H, Si(CH ) ); δ (101 MHz,
3
3
3 2
C
CDCl ) 203.0 (C-1), 155.9 (C-2), 130.7 (C-3), 108,9 (C-2’), 77.4
3
3
3
Si(CH ) ); δ (101 MHz, CDCl ) 192.0 (C-1), 146.9 (C-2), 128.3
(C-1’) 66.0 (C-3’) 32.2 (C-5), 31.4 (CH ) , 25.7 (C(CH ) ), 25.6
3
2
C
3
3 2
3 3
+
(
C-3), 38.0 (C-6), 35.8 (C-4), 26.0 (C(CH ) ), 23.0 (C-5), 19.1
(C-4), 18.5, (C(CH ) ) -4.0 (Si(CH ) ). m/z (EI) 279 (M −15,
3 3 3 2
+
3
3
+
(C(CH ) ), -3.7 (Si(CH ) ). m/z (EI) 291 and 289 (M −15, 3.7 and
1.6), 237 (M −57, 100), 219 (26.0).
3
3
3 2
+
3
1
.8), 249 and 247 (M −57, 100 and 99.3), 167 (14.8), 139 (45.2),
2
-(tert-Butyl-dimethyl-silanyloxy)-3-hex-1-ynyl-cyclopent-2-
37 (45.9).
enone (6e). Obtained as a colorless oil (60 mg, 68%); [Found: C,
69.71; H, 9.65, C H O Si requires C, 69.81; H, 9.65]. ν (neat,
General procedure for the coupling of cyclic 3-bromo-1,2-
1
7
28
2
max
-
1
diketones with terminal alkynes. A mixture of bromo-diketone (2
or 4; 0.3 mmol), Pd(PPh ) Cl (10.5 mg, 0.015 mmol) and CuI
cm ): 2932, 2859, 2215, 1711, 1615, 1462, 1372, 1252, 1216,
1134, 845, 787. δ (400 MHz, CDCl ): 2.52-2.50 (m, 2H, H-4),
3
2
2
H
3
(
2.9 mg, 0.015 mmol) in 10-ml flask equipped with septum was
2.45 (t, J = 7.0 Hz, 2H, H-3’), 2.36-2.33 (m, 2H, H-5), 1.60-1.52
(m, 2H, H-4’) 1.49-1.40 (m, 2H, H-5’) 0.97 (s, 9H, C(CH ) ),
flushed with argon for 10 min. Triethylamine (6 mL) was then
added and the flask flushed again with argon for 10 min. Finally,
alkyne 11 (0.6-0.9 mmol) was added and the reaction mixture
3
3
0.92 (t, J = 7.3 Hz, 3H, H6’), 0.20 (s, 6H, Si(CH ) ); δ (101
3
2
C
MHz, CDCl ) 203.2 (C-1), 155.1 (C-2), 132.8 (C-3), 107.0 (C-
3
was heated at reflux for 1h. Subsequently, saturated NH Cl
2’), 76.1 (C-1’) 32.2 (C-5), 30.6 (C-4’) 26.0 (C-4), 25.7
(C(CH ) ), 22.1 (C-5’) 19.9 (C-3’) 18.4, (C(CH ) ) 13.7 (C-6’), -
4
solution (12 mL) was added to the cooled mixture and extracted
with EtOAc (2x10 mL). The extracts were washed with brine (5
mL), dried (Na SO ) and the solvent was evaporated. The residue
3
3
3 3
+
+
4.0 (Si(CH ) ). m/z (EI) 277 (M −15, 2.0), 235 (M −57, 100).
3
2
2
4
2
-(tert-Butyl-dimethyl-silanyloxy)-3-(3-methoxy-prop-1-ynyl)-
was purified by flash chromatography (silica gel,
heptanes/EtOAc or heptanes/toluene) to give target compounds.
cyclopent-2-enone (6f). Obtained as a white solid (71 mg, 85%);

5
ο
mp 42-43 C; [Found: C, 64.36, H, 8.68, C H O Si requires C,
extracted with EtOAc (1x10 mL and 2x5 mL). The extracts
15
ACCEPTED MANUSCRIPT
24
3
-
1
6
1
4
2
4.24; H, 8.63]. νmax (KBr, cm ): 2928, 2857, 1703, 1622, 1472,
367, 1251, 1214, 1132, 1100, 844, 788. δ (400 MHz, CDCl )
.34 (s, 2H, H-3’), 3.42 (s, 3H, OCH3), 2.58-2.55 (m, 2H, H-4),
.39-2.37 (m, 2H, H-5), 0.97 (s, 9H, C(CH ) ), 0.21 (s, 6H,
were washed with brine (5 mL), dried (Na SO ) and the solvent
2 4
was evaporated. The residue was purified by flash
chromatography on silica gel (heptane/acetone 10:2) giving the
target compound.
H
3
3
3
Si(CH ) ) δ (101 MHz, CDCl ) 203.0 (C-1), 156.1 (C-2), 130.4
3
2
C
3
2
-Hydroxy-3-phenylethynyl-cyclopent-2-enone (5a). Obtained
(
C-3), 100.3 (C-2’), 81.5 (C-1’), 60.6 (C-3’), 57.9 (OCH ), 32.2
3
from 6a (54 mg, 0.17 mmol) and K CO (26 mg, 0.19 mmol) in
MeOH (2.2 mL) as a white solid (33 mg, 96%); mp 163-166 C.
Found: C, 78.69; H, 5.19, C H O requires C, 78.77; H,
.09]. νmax (KBr, cm ): 3285, 2924, 2193, 1680, 1631, 1489,
1407, 1391, 1341, 1240, 1142, 1114, 777, 688. δH (400 MHz,
DMSO-d6) 10.31 (s, 1H, OH), 7.53-7.51 (m, 2H, o-Ph), 7.44-
7.42 (m, 3H, m, p-Ph), 2.58-2.56 (m, 2H, H-4), 2.41-2.39 (m, 2H,
H-5); δ (101 MHz, DMSO-d6) 202.3 (C-1), 156.3 (C-2), 131.3
(2C, o-Ph), 129.2 (p-Ph), 128.9 (2C, m-Ph), 122.1 (s-Ph), 121.4
(C-3), 102.4 (C-2’), 84.9 (C-1’), 31.9 (C-5), 25.0 (C-4). m/z (EI)
2
3
(
C-5), 25.64 (C(CH ) ), 25.57 (C-4), 18.4, (C(CH ) ), -4.0
ο
3
3
3 3
+
+
(Si(CH ) ). m/z 265 (M −15, 1.7), 223 (M −57, 100), 208 (7.1),
3 2
[
5
13
10
2
1
93 (22.8), 179 (11.5), 155 (26.9).
-(tert-Butyl-dimethyl-silanyloxy)-3-phenylethynyl-cyclohex-
-1
2
2
8
-enone (8a). Obtained as a white solid (86 mg, 88%); mp 84-
ο
6 C. [Found: C, 73.64; H, 8.05, C H O Si requires C, 73.57;
20
26
2
-
1
H, 8.03]. νmax (KBr, cm ): 2936, 2854, 2186, 1676, 1601, 1586,
488, 1471, 1367, 1205, 1179, 929, 831, 779, 755. δ (400 MHz,
C
1
H
CDCl ) 7.49-7.45 (m, 2H, o-Ph), 7.36-7.33 (m, 3H, m, p-Ph),
3
+
2
2
.62 (t, J = 6.0 Hz, 2H, H-4), 2.51 (dd, J = 7.4, 5.9 Hz, 2H, H-6),
.04-1.98 (m, 2H, H-5), 1.02 (s, 9H, C(CH ) ), 0.23 (s, 6H,
198 (M 93.9), 170 (7.1), 141 (38.4), 128 (100).
3
3
3
-[3-(tert-Butyl-dimethyl-silanyloxy)-prop-1-ynyl]-2-hydroxy-
Si(CH ) ); δ (101 MHz, CDCl ) 194.1 (C-1), 150.4 (C-2), 131.7
3
2
C
3
cyclopent-2-enone (5c). Obtained from 6c (38 mg, 0.1 mmol) and
K CO (15 mg, 0.11 mmol) in MeOH (1.5 mL) as a white solid
22 mg, 83%); mp 107-109 C; [Found: C, 63.12; H, 8.27,
(
(
(
3
2C, o-Ph), 128.9 (p-Ph), 128.5 (2C, m-Ph), 123.2 (s-Ph), 120.6
C-3), 102.6 (C-2’) 87.6 (C-1’), 38.5 (C-6), 30.4 (C-4), 26.0
C(CH ) ), 22.8 (C-5), 19.0 (C(CH ) ), -3.9 (Si(CH ) ). m/z (EI)
2
3
ο
(
C
2
3
3
3 3
3 2
-1
+
+
14
H
22
O
3
Si requires C, 63.12; H, 8.32]. νmax (KBr, cm ): 3275,
11 (M −15, 32.6), 269 (M −57, 100).
929, 2857, 1689, 1646, 1455, 1389, 1085, 838, 776. δH (400
2
-(tert-Butyl-dimethyl-silanyloxy)-3-(3-hydroxy-3-methyl-but-
MHz, CDCl ): δ 6.29 (s, 1H, OH), 4.57 (s, 2H, H-3’), 2.60-2.58
3
1
8
-ynyl)-cyclohex-2-enone (8d). Obtained as a white solid (74 mg,
(m, 2H, H-4), 2.47-2.45 (m, 2H, H-5), 0.92 (s, 9H, C(CH ) ),
3
3
ο
0%); mp 99-101 C; [Found: C, 66.20; H, 9.14, C H O Si
0.15 (s, 6H, Si(CH ) ). δ (101 MHz, CDCl ) 202.7 (C-1), 154.4
17
28
3
3 2 C 3
-
1
requires C, 66.19; H, 9.15]. νmax (KBr, cm ): 3419, 2928, 2854,
209, 1656, 1586, 1462, 1372, 1259, 1210, 1182, 1148, 936, 830.
δH (400 MHz, CDCl ) 2.50-2.45 (m, 4H, H-4, H-6), 2.01-1.92
(C-2), 122.9 (C-3), 103.9 (C-2’), 78.8 (C-1’) 52.6 (C-3’) 31.7 (C-
5), 26.0 (C(CH ) ), 25.7 (C-4), 18.4, (C(CH ) ), -5.0 (Si(CH ) ).
2
3
3
3 3
3 2
+
+
m/z (EI) 251 (M −15, 1.8), 209 (M −57, 100), 193 (10.5), 179
3
(
m, 3H, H-5, OH), 1.56 (s, 6H, (CH )2, 0.98 (s, 9H, C(CH ) ),
(41.3).
3
3 3
0
.19 (s, 6H, Si(CH ) ); δ (101 MHz, CDCl ) 194.2 (C-1), 150.4
3 2 C 3
2
-Hydroxy-3-phenylethynyl-cyclohex-2-enone (7a). Obtained
(C-2), 119.8 (C-3), 106,9 (C-2’), 80.2 (C-1’) 66.0 (C-3’) 38.4 (C-
from 8a (65 mg, 0.2 mmol) and K CO (61 mg, 0.44 mmol) in
MeOH (3 mL) as a white solid (40 mg, 94%); mp 106-109 C.
[Found: C, 79.42; H, 5.78, C14 requires C, 79.22; H, 5.70].
νmax (KBr, cm ): 3390, 2946, 2185, 1651, 1607, 1489, 1378,
1166, 1133, 887, 756, 690. δ (400 MHz, CDCl ) 7.54-7.49 (m,
2
3
6
), 31.4 (CH ) , 30.4 (C-4), 26.0 (C(CH ) ), 22.7 (C-5), 18.9,
ο
3
2
3 3
+
(
C(CH ) ) -3.9 (Si(CH ) ). m/z (EI) 293 (M −15, 2.4), 251
3 3 3 2
+
H O
12 2
(M −57, 85.9), 233 (100), 193 (19.1), 177 (12.2).
-1
2
-(tert-Butyl-dimethyl-silanyloxy)-3-(3-methoxy-prop-1-ynyl)-
H
3
cyclohex-2-enone (8f). Obtained as a colorless oil (62 mg, 70%).
2H, o-Ph), 7.36-7.31 (m, 3H, m,p-Ph), 6.63 (s, 1H, OH), 2.63-
[
Found: C, 65.31; H, 8.88, C H O Si requires C, 65.26; H,
2.57 (m, 4H, H-4, H-6), 2.08-2.02 (m, 2H, H-5); δ (101 MHz,
16
26
3
C
8
1
2
1
.90]. νmax (neat, cm-1): 2931, 2857, 1683, 1592, 1464, 1364,
252, 1175, 1102, 1006, 936, 841. δ (400 MHz, CDCl ): 4.29 (s,
CDCl ) 193.9 (C-1), 149.5 (C-2), 131.9 (2C, o-Ph), 129.1 (p-Ph),
3
128.5 (2C, m-Ph), 122.8 (s-Ph), 112.4 (C-3), 103.5 (C-2’), 85.6
H
3
+
H, H-3’), 3.39 (s, 3H, OCH3), 2.52-2.45 (m, 4H, H-4, H-6),
.98-1.92 (m, 2H, H-5), 0.96 (s, 9H, C(CH ) ), 0.18 (s, 6H,
(C-1’) 36.2 (C-6), 29.3 (C-4), 22.8 (C-5). m/z (EI) 212 (M 79.1),
197 (3.2), 184 (15.7), 156 (11.4), 141 (19.3), 128 (100).
3
3
Si(CH ) ); δ (101 MHz, CDCl ) 194.2 (C-1), 150.9 (C-2), 119.8
3
2
C
3
2
-Hydroxy-3-trimethylsilanylethynyl-cyclopent-2-enone (5b).
(
C-3), 98.3 (C-2’), 84.3 (C-1’), 60.7 (C-3’), 57.9 (OCH ), 38.4
3
To a solution of 6b (62 mg, 0.2mmol) in THF (2 mL) a solution
of HCl (3N, 0.8 mL) was added and the mixture was stirred for
5 h at room temperature. Then water (6 mL) was added, the
mixture was extracted with EtOAc (2x10 mL), the extracts were
washed with brine (5 mL), dried (Na SO ) and concentrated. The
(
4
2
C-6), 30.1 (C-4), 25.8 (C(CH ) ), 22.7 (C-5), 18.8, (C(CH ) ), -
3
3
3 3
+
+
.0 (Si(CH ) ). m/z (EI) 279 (M −15, 2.5), 237 (M −57, 100),
3 2
2
22 (33.3), 207 (18.7), 193 (5.7), 169 (17.2).
Procedure for cross-coupling in a mixture of THF/Et N. A
3
2
4
mixture of bromo diketone (2 or 4; 1 mmol), Pd(PPh ) Cl (35.1
residue was purified by flash chromatography on silica gel
3
2
2
mg, 0.05 mmol) and CuI (9.5 mg, 0.05 mmol) in a 10-ml flask,
equipped with septum was flushed with argon for 10 min. Then,
(heptane/acetone 15:1 to 10:1) giving compound 5b as a white
ο
solid (28 mg, 72%); mp 135-137 C. [Found: C, 61.84; H, 7.28,
-
1
THF (5mL), Et N (1.39 mL, 10 mmol) and alkyne 11 (2 mmol)
C H O Si requires C, 61.81; H, 7.26]. ν
(KBr, cm ): 3324,
3
10 14
2
max
were added and the mixture was stirred for 24 h for 6b or
2962, 2127,1690, 1640, 1380, 1249, 1121, 847, 689. δH (400
refluxed for 1 h for 6a. Then saturated NH Cl solution (30 mL)
MHz, CDCl ) 6.43 (s, 1H, OH), 2.61-2.59 (m, 2H, H-4), 2.46-
4
3
and EtOAc (30 mL) were added, the layers were separated, the
organic phase was washed with brine (15 mL), dried (Na SO )
and the solvents evaporated. The residue was purified by flash
chromatography.
2.44 (m, 2H, H-5), 0.24 (s, 9H, Si(CH ) ); δ (101 MHz, CDCl )
3
3
C
3
203.0 (C-1), 154.8 (C-2), 123.1 (C-3), 111.8 (C-2’), 98.0 (C-1’)
2
4
+
31.8 (C-5), 25.9 (C-4), -0.1 (Si(CH ) ). m/z (EI) 194 (M 34.7),
3
3
179 (100), 151 (14.2).
Procedure for deprotection of silyl enol ethers in basic
conditions. To a solution of (6a or 6c or 8a (0.1-0.2 mmol) in
MeOH (1.5-3 mL) K CO (0.1-0.4 mmol) was added and the
mixture was stirred for 2 h at room temperature. Then water was
added, the mixture was acidified with 1N HCl to pH~3 and
Acknowledgements.
2
3
The authors thank the Estonian Ministry of Education and
Research (Grants No. YUT 19-32 and ETF 8880) and EU
European Regional Development Fund (3.2.0101.08-0017) for

6
Tetrahedron
ACCEPTED MANUSCRIPT
Moroz, A. A.; Shvartsberg, M. S. Russ. Chem. Bull. Int. Ed. 2005,
financial support. The authors are grateful to Mrs. Tiiu Kailas
5
4, 1686-1689.
for IR spectra and elemental analysis.
7
.
Chen, H. S.; Ma, X. P.; Li, Z. M.; Wang, Q. R.; Tao, F. G.
Chinese Chem. Lett. 2008, 19, 1309-1311.
Dahglen, K.; Wallen, E.A.A.; Grøtli, M.; Luthman, K. J. Org.
Chem. 2006, 71, 6863-6871.
Supporting information
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1
13
H, C NMR and IR spectra.
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ACCEPTED MANUSCRIPT
Sonogashira cross-coupling of 3-bromo-1,2-diones: an access to 3-alkynyl-1,2-diones
†
†
†
†
‡
†*
Anne Paju ; Tõnis Kanger ; Aleksander-Mati Müürisepp ; Tiina Aid ; Tõnis Pehk and Margus Lopp
†Department of Chemistry, Tallinn University of Technology, Akadeemia tee 15, 12618 Tallinn, Estonia
‡National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, 12618 Tallinn, Estonia
margus.lopp@ttu.ee
Supporting Information
Table of Contents
1
13
H NMR and C NMR data for synthesized compounds
S2-S33
S34-S49
IR spectra for synthesized compounds
S1

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1H NMR data for compound 1
S2

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13C NMR data for compound 1
S3

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1H NMR data for compound 2
S4

ACCEPTED MANUSCRIPT
13C NMR data for compound 2
S5

ACCEPTED MANUSCRIPT
1H NMR data for compound 4
O
OTBS
Br
S6

ACCEPTED MANUSCRIPT
13C NMR data for compound 4
O
OTBS
Br
S7

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1H NMR data for compound 6a
S8

ACCEPTED MANUSCRIPT
13C NMR data for compound 6a
S9

ACCEPTED MANUSCRIPT
1H NMR data for compound 6b
S10

ACCEPTED MANUSCRIPT
13C NMR data for compound 6b
S11

ACCEPTED MANUSCRIPT
1H NMR data for compound 6c
S12

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13C NMR data for compound 6c
S13

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1H NMR data for compound 6d
S14

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13C NMR data for compound 6d
S15

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1H NMR data for compound 6e
S16

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13C NMR data for compound 6e
S17

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1H NMR data for compound 6f
S18

ACCEPTED MANUSCRIPT
13C NMR data for compound 6f
S19

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1H NMR data for compound 8a
S20

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13C NMR data for compound 8a
S21

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1H NMR data for compound 8d
S22