Protection/deprotection-free syntheses and structural analysis of (keto-aryl)diynes

Article abstract of DOI:10.1002/ejoc.200800350

The reactions of precursors 4-BrC₆H₄COR with TMSC≡CH (Sonogashira coupling) followed by in situ deprotection and subsequent dimerization gave thermally stable dimeric ketodiynes RCOC ₆H₄(C≡C)₂C_6<

Full text of DOI:10.1002/ejoc.200800350

FULL PAPER
DOI: 10.1002/ejoc.200800350
Protection/Deprotection-Free Syntheses and Structural Analysis of
(Keto-aryl)diynes
Karolina Osowska,[a] Tadeusz Lis,[a] and Sławomir Szafert*[a]
Keywords: Polyynes / Homocoupling / Dimerization / Halogenation / Alkynes
The reactions of precursors 4-BrC6H4COR with TMSCϵCH
(Sonogashira coupling) followed by in situ deprotection and
subsequent dimerization gave thermally stable dimeric keto-
diynes RCOC6H4(CϵC)2C6H4COR (8–11) as yellow powders
in 25–85% yields without the necessity of carbonyl group
protection/deprotection steps. Compounds 8–11 were also
by X-ray crystallography. Careful analysis of the crystal data
revealed a surprisingly high degree of chain curvature.
Moreover, compounds 9 (R = Me) and 10 (R = Et) were ex-
tremely flat, which greatly facilitates electronic communica-
tion throughout the whole molecule. Deeper analysis of the
packing motifs showed 9 to have a great potential for topo-
synthesized by an alternative method that utilized α-haloal- chemical 1,4-polymerization.
kynes previously obtained directly from TMS-protected 4-
RCOC6H4CϵCTMS alkynes. The resulting diynes were
characterized by spectroscopic methods and in most cases
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2008)
In 2000 Mori, Hiyama and co-workers described a new
method of coupling of alkynylsilanes that did not involve
a deprotection step.[11] Later, similar pathways with in situ
deprotection were introduced although some of the reaction
conditions have to be chosen in a particularly astute man-
ner.
All the above-mentioned methods are largely chemose-
lective and tolerate many substituents within an alkyne end-
group. To our surprise we have found just a few reports that
deal with carbonyl-containing (aldehydes or ketones) end-
groups, which are, unarguably, one of the most versatile
functionalities. The combination of their functional versatil-
ity and activity renders them an ideal “anchor” for further
transformations especially in asymmetric synthesis. From
that standpoint the synthesis of carbonyl-containing po-
lyynes in a simple manner would open the door to chiral
polyyne derivatives.
Alkynones are very interesting compounds. For instance,
α-alkynones undergo cyclization by Ni-catalyzed cyanation
to give hydroxy lactams.[12] They can also be added organo-
catalytically to β-dicarbonyl compounds[13] or used for the
synthesis of pyroglutamic acid derivatives.[14] They also find
use in the synthesis of organometallic ketovinylidenes.[15]
Further separation of C=O and CϵC groups allows the
synthesis of interesting and practically very important het-
erocycles.[16]
In the examined multistep syntheses of different alky-
nones the carbonyl group is usually created from a hydroxy
group at the final stage of the synthesis. For instance, in
the synthesis of an oxidized derivative of panaxytriol,[17] the
major constituent responsible for the biological activity of
red ginseng that helped to establish the relative and absolute
Introduction
Conjugated organic, organometallic and metal-contain-
ing polyynes have attracted a great deal of attention from
several standpoints. The polyyne[1] motif is, for instance,
ubiquitous in many natural organic products,[2] which often
show remarkable biological activities.[3] Organic diynes are
also useful precursors for different types of conjugated
polymers,[4] including those that result from topochemical
crystal-to-crystal polymerization.[5] Polyynes that bear re-
dox-active moieties are another group of compounds that
are envisioned to be highly useful in nanotechnology as mo-
lecular-scale devices like wires and switches.[6] This group
of compounds includes organometallic complexes of the
LmMCxMLm type[7] as well as metal-containing species in
which the metal atom is not bound directly to the carbon
atoms of a polyyne chain. The latter group mostly includes
ferrocene derivatives[8] although other types of compounds
are known.[9]
There are now many synthetic strategies that enable the
introduction of a CϵC fragment as well as unsaturated car-
bon-chain elongation.[10] These range from an already his-
torical Glaser-type coupling to new modifications of the
Cadiot–Chodkiewicz cross-coupling protocols. Neverthe-
less, the great majority of these methods involve the use
of terminal alkynes, which for longer chains are often of
moderate-to-low stability, which, as a consequence, lowers
the yield of the final product.
[a] Department of Chemistry, University of Wrocław,
14 Joliot-Curie, 50-383 Wrocław, Poland
Fax: +48-71-328-23-48
E-mail: szaf@wchuwr.chem.uni.wroc.pl
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Syntheses and Structural Analysis of (Keto-aryl)diynes
configuration of panaxytriol, the carbonyl group was intro- Synthesis of RCOC6H4CϵCX (R = H, CH3, C2H5;
duced in the last synthetic step by oxidation of a hydroxy X = Br or I)
group at the 3-position. Very often it comes from acetal
hydrolysis which protects the carbonyl group through the
α-Haloalkynes are important starting materials in nu-
merous organic transformations. The specific properties of
whole synthetic procedure. This approach usually lowers
a triple bond modified by a halo atom make them very
the final yield as conjugated triple bonds are sensitive
susceptible to the addition of nucleophilic agents.[23] More
interestingly they are excellent substrates for simultaneous
addition/substitution reactions.[24] Traditionally, α-haloal-
kynes are key substrates in heterocoupling reactions in the
synthesis of asymmetric polyynes.[25] They are also used in
the synthesis of 1-bromovinylboranes, which, by transme-
tallation followed by C=O addition in one pot, are trans-
formed into (Z)-substituted allylic alcohols[26] and are great
substrates for the synthesis of α-keto acid esters.[27] From
our perspective an important paper was published in 2003
by Lee and co-workers that described the successful homo-
coupling reaction of 1-iodoalkynes.[28]
Syntheses of α-haloalkynes are usually based on the use
of terminal alkynes as starting materials. These are often
unstable, which lowers the final yield. Lately, the syntheses
of α-haloalkynes directly from R3Si-protected alkynes have
been published.[29] These protocols obviate the need of de-
protection and, as a consequence, save one preparation step.
Bromo- and iodo-derivatives 5–7 were obtained in the
reaction of trimethylsilyl-substituted precursors 1–3 with
NBS or NIS, as shown in Scheme 1. Work-up gave the ana-
lytically pure target α-iodo- (5–7-I) and α-bromoalkynes (5–
7-Br) in 80–90 and 94–97% yields, respectively. Interest-
ingly, this method did not allow the substitution of 4, which
surprisingly has also proven resistant to other halogenation
methods.[30] Compounds 5–7-X are yellow powders that are
soluble in most common organic solvents. In the solid state
they are stable for extended periods, but in solution iodoal-
kynes partially decompose over a period of a few days.
These compounds were characterized by 1H and 13C
NMR spectroscopy, which gave routine spectra. The signals
of the acetylenic α-carbon atoms of 5–7-Br were shifted by
around 23 ppm to lower values compared with the iodo de-
rivatives. Signals from the β-carbon atoms were observed at
values lower by ca. 14 ppm, as shown in the Exp. Sect.
towards electrophilic attack.[18,19]
In some other cases the carbonyl group was introduced
into the already formed oligoacetylene, for instance, in the
excellent work of Frauenrath and co-workers on diacetylene
copolymers[5g] or in a more general acylation of trimethyl-
silyl-substituted[20] or terminal alkynes.[21]
Although the published procedures are claimed to be ge-
neral we have found the homocoupling reaction of aryl al-
dehydes and ketones to be quite tricky. This is probably due
to the common use of primary and secondary amines in the
majority of synthetic protocols which are known to easily
react with the C=O group. In this paper, we report the suc-
cessful synthesis of a series of diynes with aryl aldehyde/
ketone containing end-groups. The presented strategies in-
volve no protection/deprotection steps.
Results and Discussion
Synthesis of RCOC6H4CϵCTMS (R = C2H5, C6H5)
Following the previously described procedure for
HCOC6H4CϵCTMS (1) and CH3COC6H4CϵCTMS
(2),[22] the trimethylsilylacetylenic derivatives C2H5COC6-
H4CϵCTMS (3) and C6H5COC6H4CϵCTMS (4) were
synthesised as shown in Scheme 1. Work-up by column
chromatography gave 3 (brown oily solid) and 4 (pale yel-
low powder) in 90 and 98% yields, respectively. Both com-
pounds are readily soluble in CH2Cl2, acetone and THF
and poorly soluble in hexanes.
Synthesis of RCOC6H4(CϵC)2C6H4COR (R = H, CH3,
C2H5 or C6H5)
The straightforward synthesis and characterization of
symmetric ketodiynes formed a major goal of our research.
One obvious route would require the deprotection of 1–4
and subsequent dimerization. This approach was tested for
ethynylbenzaldehyde and gave target HCOC6H4(CϵC)2-
Scheme 1. Synthesis of aryl trimethylsilylacetylenic and haloacetyl-
enic derivatives.
1
Compounds 3 and 4 were characterized by H and 13C C6H4CHO (8) in 66% yield.[31] Although this protocol has
NMR spectroscopy and gave the correct elemental analysis. proven useful we were looking for other expedient syntheses
The 1H and 13C NMR spectroscopic data were routine. The that would give satisfactory yields and exclude the deprotec-
1H NMR spectra revealed signals of the TMS group at δ = tion step. First, in accord with the report of Mori, Hiyama
0.20 and 0.25 ppm for 3 and 4, respectively. The signals of and co-workers,[11] we tried the homocoupling of trimethyl-
the carbonyl carbon atoms were at 199.6 (3) and 195.9 ppm silyl-protected (keto-aryl)acetylenes 1 and 2 in DMF at
(4).
60 °C catalyzed by CuCl. Although this approach gave ex-
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K. Osowska, T. Lis, S. Szafert
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cellent results for alkyl- and phenyl-substituted acetyl-
enes[11] and diacetylenes,[32] the resulting yields were as low
as 15% and most of the starting material was recovered.
In another thrust, we tried two alternative approaches.
The first one utilized SiMe3-protected 1–4, which were sub-
jected to homocoupling with in situ deprotection by using
TBAF followed immediately by the addition of Me3SiCl (as
an F– ion scavenger) and the CuI/TMEDA/acetone catalytic
system. Although this approach gave targets 8–11, the
yields were considerably obscured (in the cases of 1–3 they
were less than 10%) by the aldol side-reaction of the start-
ing aldehyde or ketone with acetone, presumably promoted
by the Lewis acidic Me3SiCl. The products of this reaction
were unambiguously identified by GC–MS. Modification of
the catalytic system by exchanging acetone for THF al-
lowed the synthesis of 9–11 in yields of 75–85% as yellow
powders (Table 1). Surprisingly, this approach repeatedly
gave a much lower yield (25% best) for 8, which might be
related to the possible oxidation of the aldehyde by
TBAF.[33]
Scheme 2. Synthesis of (keto-aryl)diynes.
The 13C NMR spectra showed CϵC–CϵC signals
(CDCl3) at δ = 82.1, 82.0, 81.8 and 81.8 ppm for CCPh and
at δ = 76.4, 76.5, 76.3 and 76.3 ppm for CCPh for 8–11,
respectively. These values are in accord with the chemical
shifts of other diynes.
Table 1. Yields and spectroscopic data for 8–11.
Complex
8
9
10
11
Yield from CϵCTMS [%]
Yield from CϵCI [%]
Yield from CϵCBr [%]
IR [cm–1]
25
5
72
2210
1928
1697
191.2
75
29
90
2213
1934
1677
197.0
82.0
76.5
85
28
85
2213
1936
1685
199.7
81.8
76.3
75
–
–
2105
1941
1650
195.6
81.8
76.3
Crystal Structures of 9–11
The crystal structures of 9–11 were determined as out-
lined in Table 2 and Table 3 and described in the Exp. Sect.
Figure 1 presents two views of the centrosymmetric mole-
cule of 9. As can be seen in the bottom view the molecule
is almost planar. Both phenyl rings as well as the two planes
13C NMR of C=O [ppm]
13C NMR of CϵCPh [ppm] 82.1
13C NMR of CϵCPh [ppm] 76.4
Table 2. Bond lengths [Å] and angles [°] for 9–11.
An alternative approach was next tried. This was based
on the protocol of Lee and co-workers who utilized 1-
iodoalkynes for the homocoupling.[28] In a typical reaction,
one of the halogen-terminated 5–7-X (X = I or Br) was
placed in DMF and [Pd(PPh3)4] was added as the cata-
Complex
9
10
11
C(11)–C(1)
C(1)–C(2)
C(2)–C(2Ј)
C(3)–O(1)
1.439(2)
1.205(2)
1.369(3)
1.227(2)
176.3(2)
179.0(2)
120.7(2)
1.430(1)
1.212(1)
1.367(2)
1.223(1)
176.6(1)
179.7(1)
119.7(1)
1.428(4)
1.208(3)
1.384(6)
1.234(3)
174.3(4)
179.5(6)
119.4(3)
lyst.[28] The reactions proceeded at 100 °C. Work-up gave C(11)–C(1)–C(2)
C(1)–C(2)–C(2Ј)
O(1)–C(3)–C(14)
analytically pure 8–10 in 72–90% yields when 5–7-Br were
used as the substrates (Scheme 2). Surprisingly, the yields
were much lower (5–29%) with the iodoalkynes 5–7-I.
Compounds 8–11 are stable, light-yellow solids that are
Table 3. Crystallographic data for 9–11.
readily soluble in most common organic solvents. All the
1
diynes were characterized by IR, H and 13C NMR spec-
Complex
9
10
11
Chemical formula
Formula weight
Temp. [K]
Space group
a [Å]
b [Å]
c [Å]
C20H14O2
286.31
100(2)
P21/c
5.409(2)
4.942(2)
27.23(2)
90.12(5)
727.9(7)
2
1.306
0.083
0.0647
0.1312
C22H18O2
314.36
100(2)
P21/c
9.807(4)
12.142(5)
7.103(3)
97.36(3)
838.8(6)
2
1.245
0.078
0.0574
0.1464
C30H18O2
410.44
100(2)
C2/c
45.52(3)
3.902(3)
11.399(8)
93.74(5)
2020(2)
4
1.349
0.083
0.0752
0.0737
troscopy and mass spectrometry and the data are summa-
rized in the Exp. Sect.
Compounds 9–11 melted without decomposition at 176,
156 and 185 °C, respectively, whereas 8 melted with decom-
position at 123 °C. The mass spectra in each case showed
strong parent ions and fragmentation of the carbonyl sub-
stituent.
β [°]
V [Å3]
The IR spectra for each compound showed two weak
Z
νCϵC bands at ν = 2210, 2213, 2213 and 2105 cm–1 and
Ρ [gcm–3]
M(Mo-Kα) [mm–1]
R1 (Ͼ2σ)
wR2 (Ͼ2σ)
˜
1928, 1934, 1936 and 1941 cm–1 for 8–11, respectively. Also
νCϵO bands were observed at ν = 1697, 1677, 1685 and
˜
1650 cm–1.
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Syntheses and Structural Analysis of (Keto-aryl)diynes
Figure 1. Crystal structure of 9.
of the carbonyl groups, defined by C(14)C(3)C(4)O(1) and twisted by 6.2° from the plane of the adjacent phenyl ring.
C(14a)C(3a)C(4a)O(1a) atoms, are mutually coplanar, The bond lengths within the carbon chain are 1.205(2) Å
which is a consequence of the fact that the molecule lies on for C(1)ϵC(2) and 1.369(3) Å for C(2)–C(2A) and are sim-
a symmetry centre, but the plane of the carbonyl group is ilar to those found in other diynes.[34]
Figure 2. Crystal structure of 10.
Figure 3. Crystal structure of 11.
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K. Osowska, T. Lis, S. Szafert
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A similar situation is observed for 10 and 11. The struc- Packing Motifs
tures of the two molecules are shown in Figures 2 and 3,
The three structures 9–11 crystallize in the monoclinic
system in the P21/c (9 and 10) and C2/c (11) space groups.
As a consequence, the molecules pack to form two non-
parallel sets of parallel chains. These sets form an angle of
88.9° in 9, 36.0° in 10 and 23.4° in 11. Figure 4 shows the
packing diagram for 9 with nearly perpendicular sets of
molecules.
The closest chain–chain separation was analyzed. As de-
formation of chains takes place we understand the closest
chain–chain distance to be the closest carbon–carbon dis-
tance between two neighbouring carbon chains.[7c] Accord-
ingly, the closest chains with parallel orientation for 9 are
only 3.527 Å apart and this separation is slightly smaller
than the sum of the van der Walls radii (3.56 Å). Interest-
ingly, of the longer chain examples analyzed to date,[7c] only
two have a shorter chain–chain distance: tellurium Me-
Te(CϵC)4TeMe (3.486 Å)[35] and ferrocenyl Fc(CϵC)6Fc
(3.512 Å).[36]
respectively. The bottom views illustrate their high degree
of planarity although the carbonyl group in 11 is a little
more twisted out of the plane and forms an angle of 15.1°
with the phenyl ring that bears the carbon chain. The angle
between the C=O group and the second phenyl is 38.4° (the
phenyl rings of one end-group are twisted by 49.8°). The
planarity of 10 is almost identical to that of 9 with the
C=O/phenyl angle of 5.4°. The bond lengths within the car-
bon chain are 1.212(1) (10) and 1.208(3) Å (11) for
C(1)ϵC(2) and 1.367(2) (10) and 1.384(6) Å (11) for the
C(2)–C(2A) single bond.
Although the C4 chains are believed to be too short to
have a distinctive bending, closer inspection shows percepti-
ble deformation. This is confirmed by an analysis of the
carbon chain bond angles C11–C1–C2 and C1–C2–C2A.
These values for 9 are 176.3(2) and 178.96(17)° (average
177.7°), which is unexpectedly low. The corresponding bond
angles in 10 are 176.6(1) and 179.7(1)° (average 178.1°) and
they are 174.3(4) and 179.5(6)° for 11 (average 176.9°). Note
that these values are often even higher for much longer
chains.[7c] Based on the bond angles and visualization of the
molecules, the chain conformations for 9–11 can be de-
scribed as kinked.[7c]
In spite of the bulkier end-group the distance is similarly
low for 11 (3.814 Å, Figure 5). Surprisingly, it is signifi-
cantly different for 10 even though it has a structure very
similar to 9 (7.036 Å) and it is even longer than the separa-
tion for the closest non-parallel chains (5.993 Å). Table 4
summarizes all the geometrical data for 9–11. Figure 5
shows the closest chain–chain distances in 11.
Figure 5. Shortest chain–chain distances for parallel and non-par-
allel neighbours of 11. The distances [Å] are: C(1AD)–C(2AC),
3.815; C(2AD)–C(2D), 3.825; C(2E)–C(1D), 3.814; C(1E)–C(1D),
3.902 Å; C(1C)–C(1AD), 4.296; C(1C)–C(2AD), 4.473. Symmetry
operations for related atoms are: C(1C): 0.5 – x, 0.5 + y, 0.5 – z;
C(1D) and C(2D): 0.5 – x, 0.5 – y, 1 – z; C(2AC): x – 0.5, y – 0.5,
z; C(1AD) and C(2AD): x – 0.5, y + 0.5, z; C(1E) and C(2E): 0.5 –
x, 1.5 – y, 1 – z.
Figure 4. Packing diagram and shortest chain–chain contacts for
9. The distances are 3.527 Å for C(1)–C(1I) and 3.623 Å for C(2)–
C(1I). Symmetry operation for C(1I): 1 – x, 2 – y, 1 – z.
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Syntheses and Structural Analysis of (Keto-aryl)diynes
Table 4. Packing parameters for diynes 9–11.
Complex
9
10
11
Chain–chain contact (parallel) [Å]
Angle between parallel chains [°]
Offset distance [Å]
Fractional offset
Angle between non-parallel chains [°]
3.527
45.5
4.66
0.70
88.9
7.036
33.4
8.19
1.23
36.0
5.993
3.814
78.3
0.79
0.12
23.4
4.296
Chain–chain contact (non-parallel) [Å] 12.233
Next, we calculated the offset values,[7c] which is a mea-
sure of the mutual position of the neighbouring molecules/
carbon chains. These values are 4.663 Å for 9, 8.187 Å for
10 and 0.791 Å for 11, which correspond to fractional off-
sets[7c] (an offset divided by the C11–C11A distance) of 0.70
for 9, 1.23 for 10, and 0.12 for 11.
Implications for Reactivity
Figure 7. The mutual orientation of molecules of 9 in the crystal
lattice. Symmetry operation for related atoms: x, y + 1, z.
1,4-Topochemical polymerization is one of the possible
transformations that organic diynes or polyynes in general
can undergo. As illustrated in Figure 6 this occurs most
readily when the closest parallel chains are separated by
around 3.5 Å and the φ angle is close to 45°. These require-
ments fulfil the need of a close geometric match of the buta-
diyne and polybutadiyne crystal lattices. By screening the
geometrical properties of 9–11 it can easily be seen that 9
is an example of an ideal candidate for such polymerization
(chain–chain separation: 3.527 Å and φ = 45.5°; Figure 7).
tylenes gave the desired products with much lower yields.
The resulting diynes are stable solids with a high degree of
planarity, as evidenced by X-ray crystallography. Owing to
this feature and the presence of carbonyl groups they form
a group of attractive ligands for different metals. Their com-
plexes would most likely allow electronic communication
between the metal atoms, which is of great interest for
nanoscale electronics. This will certainly be the subject of
ongoing investigations.
Experimental Section
General: All reactions were conducted under N2 by using standard
Schlenk techniques. The solvents were treated as follows: hexanes,
distilled from Na; CH2Cl2 and acetone, distilled from P2O5; THF
and Et2O, predried with NaOH and then distilled from Na/benzo-
phenone; DMF, distilled from CaH2 and degassed; NEt3, distilled
from NaOH; CH3CN, used as received. CDCl3, vacuum transferred
from CaH2; C6D6, vacuum transferred from Na.
Figure 6. Geometrical conditions for 1,4-topochemical polymeriza-
tion.
4-Bromobenzaldehyde (99%), 4-bromoacetophenone (98%), 4-bro-
mopropiophenone (97%), 4-bromobenzophenone (98%), N-bro-
mosuccinimide (NBS; 99%), Pd(CH3COO)2 (99.9+%), [Pd-
(PPh3)4] (99%), TMSCϵCH (98%), AgF (99.9+%), CuCl
(99.995+%), PPh3 (99%), tetramethylethylenediamine (TMEDA;
99%; distilled from NaOH) and tetrabutylammonium fluoride
Compound 11, although it possesses an appropriate
chain–chain separation, has a much more ladder-type struc-
ture (φ = 78.3°; for an ideal ladder-type structure, φ = 90°).
Compound 10, however, is far from the required geometry. (TBAF; 1.0  in THF) were obtained from Aldrich and used with-
out further purification unless stated otherwise. N-Iodosuccinimide
(NIS; Fluka; 97%), Na2SO4 (AppliChem, pure), AgNO3 (POCh,
pure by analysis) and Me3SiCl (Fluka, 99%) were used as received.
4-(Trimethylsilylethynyl)benzaldehyde, 4-ethynylbenzaldehyde and
4-(trimethylsilylethynyl)acetophenone were prepared according to
the literature.[22]
It is worth adding that even though 9 crystallizes in the
C2/c space group, which creates two sets of parallel chains,
the additional translational requirement in this case is also
met.
Conclusions
Infrared spectra were recorded in a KBr cell with a Bruker 66/s
FTIR spectrometer. TG-DTA analyses were carried out with a Set-
aram SETSYS 16/18 spectrometer. NMR spectra were obtained
with Bruker ESP 300E and 500 spectrometers. GC–MS analyses
were performed with a gas chromatograph equipped with a mass
detector HP 5971A or an infrared detector HP5965B (Hewlett–
We have demonstrated that (keto-aryl)diynes can easily
be synthesized in good-to-high yields without protection/
deprotection steps by two methods: (1) from trimethyl-
silylacetylene and (2) from bromoacetylene by palladium-
catalyzed homocoupling. A little to our surprise, iodoace- Packard). Microanalyses were conducted with an ARL Model 3410
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+ ICP spectrometer (Fisons Instruments) and a VarioEL III CHNS
instrument (both in-house).
CHOC6H4CϵCBr (5-Br):[36] 4-(Trimethylsilylethynyl)benzaldehyde
(0.200 g, 0.988 mmol), AgF (0.125 g, 0.988 mmol) and NBS
(0.176 g, 0.988 mmol) were combined in a procedure analogous to
Method A for 5-I. Analogous work-up gave 5-Br as a yellow pow-
der in 94% yield (0.194 g, 0.929 mmol). 1H NMR (500 MHz,
CDCl3): δ = 9.95 (s, 1 H, CHO), 7.78 (d, JHH = 8 Hz, 2 H, Ph),
7.53 (d, JHH = 8 Hz, 2 H, Ph) ppm. 13C{1H} NMR (125 MHz,
CDCl3): δ = 191.2 (s, 1 C, CO), 135.6 (s, 1 C, p-Ph), 132.5 (s, 2 C,
o-Ph), 129.4 (s, 2 C, m-Ph), 128.7 (s, 1 C, i-Ph), 79.2 (s, 1 C, CCPh),
54.6 (s, 1 C, CCPh) ppm. C9H5BrO (209.041): calcd. C 51.71, H
2.41; found C 51.89, H 2.32.
C2H5COC6H4CϵCTMS (3): 4-Bromopropiophenone (0.500 g,
2.347 mmol) and PPh3 (0.018 g, 0.070 mmol) were dissolved in
NEt3 (50 mL). Next Pd(CH3COO)2 (0.005 g, 0.023 mmol; 1 mol-
%) and trimethylsilylacetylene (0.497 mL, 3.520 mmol) were added.
The solution was heated at reflux and the reaction was monitored
by TLC. After 6 h the mixture was filtered to remove NEt3·HBr
(0.418 g, 98%) and solvent was removed under oil-pump vacuum
leaving a brown oil. This was dissolved in a mixture of hexane/
CH2Cl2 (5 mL; v/v 1:1) and passed through a silica gel plug (2 cm).
The solvent was removed under oil-pump vacuum to give 3 as a
brown sticky solid (90%; 0.487 g, 2.114 mmol). 1H NMR
(500 MHz, CDCl3): δ = 7.80 (d, JHH = 8 Hz, 2 H, Ph), 7.45 (d,
JHH = 8 Hz, 2 H, Ph), 2.88 (q, JHH = 7 Hz, 2 H, CH2), 1.14 (t, JHH
= 7 Hz, 3 H, CH3), 0.20 [s, 9 H, Si(CH3)3] ppm. 13C{1H} NMR
(125 MHz, CDCl3): δ = 199.6 (s, 1 C, CO), 136.0 (s, 1 C, p-Ph),
131.9 (s, 2 C, o-Ph), 127.6 (s, 2 C, m-Ph), 127.5 (s, 1 C, i-Ph), 104.0
(s, 1 C, CCPh), 97.7 (s, 1 C, CCPh), 31.6 (s, 1 C, CH2), 8.0 (s, 1 C,
CH3), –0.3 [s, 3 C, Si(CH3)3] ppm. C14H18OSi (230.381): calcd. C
72.99, H 7.88; found C 73.14, H 7.66.
CH3COC6H4CϵCI (6-I): 4-(Trimethylsilylethynyl)acetophenone
(0.210 g, 0.971 mmol), AgF (0.123 g, 0.971 mmol) and NIS
(0.218 g, 0.971 mmol) were combined in a procedure analogous to
Method A for 5-I. Analogous work-up gave 6-I as a yellow powder
1
in 87% yield (0.228 g, 0.845 mmol). H NMR (500 MHz, CDCl3):
δ = 7.89 (d, JHH = 8 Hz, 2 H, Ph), 7.50 (d, JHH = 8 Hz, 2 H, Ph),
2.59 (s, 3 H, CH3) ppm. 13C{1H} NMR (125 MHz, CDCl3): δ =
197.1 (s, 1 C, CO), 136.6 (s, 1 C, p-Ph), 132.4 (s, 2 C, o-Ph), 128.1
(s, 2 C, m-Ph), 128.0 (s, 1 C, i-Ph), 93.3 (s, 1 C, CCPh), 76.7 (s, 1
C, CCPh), 26.5 (s, 1 C, CH3) ppm. C10H7IO (270.068): calcd. C
44.47, H 2.61; found C 45.14, H 2.49.
C6H5COC6H4CϵCTMS
(4):
Benzophenone
(1.000 g,
CH3COC6H4CϵCBr (6-Br):[36] 4-(Trimethylsilylethynyl)acetophe-
none (0.130 g, 0.601 mmol), AgF (0.076 g, 0.601 mmol) and NBS
(0.107 g, 0.601 mmol) were combined in a procedure analogous to
Method A for 5-I. Analogous work-up gave 6-Br as a yellow pow-
der in 97% yield (0.130 g, 0.583 mmol). 1H NMR (500 MHz,
CDCl3): δ = 7.86 (d, JHH = 8 Hz, 2 H, Ph), 7.49 (d, JHH = 8 Hz,
2 H, Ph), 2.56 (s, 3 H, CH3) ppm. 13C{1H} NMR (125 MHz,
CDCl3): δ = 197.2 (s, 1 C, CO), 136.6 (s, 1 C, p-Ph), 132.2 (s, 2 C,
o-Ph), 128.2 (s, 2 C, m-Ph), 127.5 (s, 1 C, i-Ph), 79.4 (s, 1 C, CCPh),
53.8 (s, 1 C, CCPh), 26.6 (s, 1 C, CH3) ppm. C10H7BrO (223.069):
calcd. C 53.85, H 3.16; found C 53.44, H 3.36.
3.830 mmol), PPh3 (0.030 g, 0.115 mmol), Pd(CH3COO)2 (0.017 g,
0.0757 mol; 2 mol-%) and (trimethylsilyl)acetylene (0.812 mL,
5.745 mmol) were combined in a procedure analogous to that for
3. Analogous work-up gave 4 as a pale-yellow powder in 98% yield
(1.045 g, 3.753 mmol). 1H NMR (300 MHz, CDCl3): δ = 7.74–7.41
(m, 9 H, Ph), 0.25 [s, 9 H, Si(CH3)3] ppm. 13C{1H} NMR (75 MHz,
CDCl3): δ = 195.9 (s, 1 C, CO), 137.4 (s, 1 C, iЈ-Ph), 137.0 (s, 1 C,
p-Ph), 132.5 (s, 1 C, pЈ-Ph), 131.8 (s, 2 C, o-Ph), 129.9 (s, 2 C, oЈ-
Ph), 129.9 (s, 2 C, m-Ph), 128.3 (s, 2 C, mЈ-Ph), 127.3 (s, 1 C, i-Ph),
104.1 (s, 1 C, CCPh), 97.8 (s, 1 C, CCPh), –0.2 [s, 3 C, Si-
(CH3)3] ppm. C18H18OSi (278.425): calcd. C 77.65, H 6.53; found
C 77.34, H 6.45.
C2H5COC6H4CϵCI (7-I): 4-(Trimethylsilylethynyl)propiophenone
(0.215 g, 0.933 mmol), AgF (0.118 g, 0.933 mmol) and NIS
(0.210 g, 0.933 mmol) were combined in a procedure analogous to
Method A for 5-I. Analogous work-up gave 7-I as a yellow powder
CHOC6H4CϵCI (5-I). Method A: 4-(Trimethylsilylethynyl)benzal-
dehyde (0.300 g, 1.482 mmol) and AgF (0.188 g, 1.482 mmol) was
placed in round-bottomed flask and CH3CN (15 mL) was added.
The flask was wrapped in aluminium foil and NIS (0.333 g,
1.482 mmol) was added. The mixture was stirred for 5 h at room
temperature after which time it was passed through a 2cm plug
of silica gel. The solvent was removed by rotary evaporation. The
resulting residue was dissolved in Et2O and washed with H2O
(2ϫ5 mL). The organic part was separated and dried with Na2SO4.
The solution was filtered, the Na2SO4 was rinsed with Et2O
(2ϫ5 mL) and the solvent was removed under oil-pump vacuum
to give 5-I in 90% yield (0.341 g, 1.334 mmol).
1
in 80% yield (0.210 g, 0.746 mmol). H NMR (500 MHz, CDCl3):
δ = 7.83 (d, JHH = 8 Hz, 2 H, Ph), 7.43 (d, JHH = 8 Hz, 2 H, Ph),
2.91 (q, JHH = 7 Hz, 2 H, CH2), 1.15 (t, JHH = 7 Hz, 3 H,
CH3) ppm. 13C{1H} NMR (125 MHz, CDCl3): δ = 199.7 (s, 1 C,
CO), 136.3 (s, 1 C, p-Ph), 132.3 (s, 2 C, o-Ph), 127.7 (s, 2 C, m-Ph),
127.6 (s, 1 C, i-Ph), 93.3 (s, 1 C, CCPh), 76.7 (s, 1 C, CCPh), 31.7
(s, 1 C, CH2), 8.1 (s, 1 C, CH3) ppm. C11H9IO (284.096): calcd. C
46.51, H 3.19; found C 46.39, H 3.15.
C2H5COC6H4CϵCBr (7-Br): 4-(Trimethylsilylethynyl)propiophen-
one (0.150 g, 0.651 mmol), AgF (0.082 g, 0.651 mmol) and NBS
(0.116 g, 0.651 mmol) were combined in a procedure analogous to
Method A for 5-I. Analogous work-up gave 7-Br as a yellow pow-
der in 95% yield (0.146 g, 0.618 mmol). 1H NMR (500 MHz,
CDCl3): δ = 7.87 (d, JHH = 8 Hz, 2 H, Ph), 7.49 (d, JHH = 8 Hz,
2 H, Ph), 2.95 (q, JHH = 7 Hz, 2 H, CH2), 1.19 (t, JHH = 7 Hz, 3
H, CH3) ppm. 13C{1H} NMR (125 MHz, CDCl3): δ = 199.9 (s, 1
C, CO), 136.3 (s, 1 C, p-Ph), 132.1 (s, 2 C, o-Ph), 127.9 (s, 2 C, m-
Ph), 127.2 (s, 1 C, i-Ph), 79.4 (s, 1 C, CCPh), 53.6 (s, 1 C, CCPh),
31.8 (s, 1 C, CH2), 8.1 (s, 1 C, CH3) ppm. C11H9BrO (237.095):
calcd. C 55.72, H 3.83; found C 55.53, H 3.83.
Method B: Ethynylbenzaldehyde (0.140 g, 1.076 mmol) was dis-
solved in acetone (10 mL) and AgNO3 (0.055 g, 0.323 mmol) was
added. After 0.5 h Et2O (30 mL) and NIS (0.242 g, 1.076 mmol)
were added. The mixture was stirred for 12 h after which time it
was filtered and washed with ice-cold H2O (30 mL). The organic
layer was separated. The aqueous layer was washed with Et2O
(2ϫ5 mL) and the combined organic parts were dried with
Na2SO4. The solvent was removed under oil-pump vacuum and the
residue was purified by chromatography on silica gel (20 cm; hex-
ane/CH2Cl2 v/v, 1:1) to give 5-I as a yellow powder in 90% yield
(0.248 g, 0.968 mmol). 1H NMR (500 MHz, CDCl3): δ = 9.96 (s, 1
H, CHO), 7.80 (d, JHH = 8 Hz, 2 H, Ph), 7.55 (d, JHH = 8 Hz, 2
H, Ph) ppm. 13C{1H} NMR (125 MHz, CDCl3): δ = 191.3 (s, 1 C,
CHOC6H4(CϵC)2C6H4CHO (8). Method A: A Schlenk flask was
charged with CuCl (0.010 g, 0.101 mmol) and TMEDA (0.009 mL,
CO), 135.7 (s, 1 C, p-Ph), 132.9 (s, 2 C, o-Ph), 129.4 (s, 2 C, m-Ph), 0.060 mmol). THF (6 mL) was added and the mixture was stirred
129.3 (s, 1 C, i-Ph), 93.3 (s, 1 C, CCPh), 77.2 (s, 1 C, CCPh) ppm.
C9H5IO (256.041): calcd. C 42.22, H 1.97; found C 42.66, H 1.87.
for 0.5 h. A blue supernatant formed over the green solid. In a
separate flask 4-ethynylbenzaldehyde (0.064 g, 0.492 mmol) was
4604
www.eurjoc.org
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2008, 4598–4606

Syntheses and Structural Analysis of (Keto-aryl)diynes
dissolved in THF (15 mL). O2 was bubbled through the solution
for 15 min and the blue supernatant was added in portions. After
4 h the solvent was evaporated by oil pump vacuum. The residue
was treated with a 1:1 mixture of hexane/CH2Cl2 (5 mL) and the
solution was filtered through a 5 cm plug of alumina. The solvent
was evaporated by oil-pump vacuum to give 8 as a yellow solid in
66% yield (0.042 g, 0.162 mmol).
(125 MHz, CDCl3): δ = 197.0 (s, 1 C, CO), 137.1 (s, 1 C, p-Ph),
132.6 (s, 2 C, o-Ph), 128.3 (s, 2 C, m-Ph), 126.2 (s, 1 C, i-Ph), 82.0
(s, 1 C, CCPh), 76.5 (s, 1 C, CCPh), 26.6 (s, 1 C, CH3) ppm. IR
(KBr): ν = 2213 (w, νCϵC), 1934 (w, νC=O) 1677 (s) cm–1. MS: m/z
˜
= 286 [M]+, 271 [M – CH3]+, 243 [M – CH3 – CO]+, 228 [M –
2CH3 – CO]+, 200 [M – 2CH3 – 2CO]+. C20H14O2 (286.329): calcd.
C 83.90, H 4.93; found C 83.67, H 4.87.
Method B:
A Schlenk flask was charged with 1 (0.200 g,
C2H5COC6H4(CϵC)2C6H4COC2H5 (10). Method B: Compound 3
(0.360 g, 1.563 mmol), wet TBAF (0.313 mL, 1.0  solution in
THF, 20 mol-%), Me3SiCl (0.197 mL, 1.559 mmol), CuCl (0.155 g,
1.563 mmol) and TMEDA (0.094 mL, 0.625 mmol) were combined
in a procedure analogous to that for 8 (Method B). Analogous
work-up gave 10 as a yellow powder in 85% yield (0.209 g,
0.664 mmol). Method C: 7-I (0.203 g, 0.714 mmol) and [Pd-
(PPh3)4] (0.033 g, 0.028 mmol, 4 mol-%) were combined in a pro-
cedure analogous to that for 8 (Method C). Analogous work-up
gave 10 as a yellow powder in 28% yield (0.031 g, 0.100 mmol).
0.988 mmol) and THF (10 mL) was added. The solution was
purged with N2 and wet TBAF (1.0  solution in THF, 0.198 mL,
20 mol-%) was added dropwise. After 20 min Me3SiCl (0.125 mL,
0.988 mmol) was added. After 15 min O2 was bubbled through the
solution for 10 min. In a separate Schlenk flask CuCl (0.098 g,
0.989 mmol) and TMEDA (0.059 mL, 0.390 mmol) were mixed in
THF (5 mL). The blue supernatant that emerged after 0.5 h was
added in portions to the first Schlenk flask. O2 was bubbled
through the reaction. After 5 h the solvent was removed by oil
pump vacuum. The residue was dissolved in a minimum of CH2Cl2
and filtered through a 5 cm plug of alumina and then through a
3 cm plug of silica gel. The solvent was removed by oil-pump vac-
uum to give a yellow solid residue in 25% yield (0.032 g,
0.123 mmol).
Method D: 7-Br (0.065 g, 0.274 mmol) and [Pd(PPh3)4] (0.013 g,
0.011 mmol, 4 mol-%) were combined in a procedure analogous to
that for 8 (Method D). Analogous work-up gave 9 as a yellow pow-
der in 85% yield (0.037 g, 0.116 mmol). M.p. 156 °C. 1H NMR
(500 MHz, CDCl3): δ = 7.91 (d, JHH = 8 Hz, 2 H, Ph), 7.58 (d,
JHH = 8 Hz, 2 H, Ph), 2.97 (q, JHH = 7 Hz, 2 H, CH2), 1.20 (t,
JHH = 7 Hz, 3 H, CH3) ppm. 13C{1H} NMR (125 MHz, CDCl3):
δ = 199.7 (s, 1 C, CO), 136.8 (s, 1 C, p-Ph), 132.5 (s, 2 C, o-Ph),
127.8 (s, 2 C, m-Ph), 125.9 (s, 1 C, i-Ph), 81.8 (s, 1 C, CCPh), 76.3
(s, 1 C, CCPh), 31.8 (s, 1 C, CH2), 8.0 (s, 1 C, CH3) ppm. IR (KBr):
Method C: 5-I (0.080 g, 0.312 mmol) was dissolved in DMF
(2 mL). Next [Pd(PPh3)4] (0.014 g, 0.012 mmol, 4 mol-%) was
added. The mixture was heated at 100 °C for around 14 h. DMF
was evaporated under oil-pump vacuum and the residue was dis-
solved in CH2Cl2 (1 mL) and filtered through a silica plug (ca.
6 cm). The second fraction was pure 8 (5% yield, 0.002 g,
0.008 mmol).
ν = 2213 (w, νCϵC), 1936 (w, νC=O) 1685 (s) cm–1. MS: m/z = 314
˜
[M]+, 285 [M – CH2CH3]+, 228 [M – 2CH2CH3 – CO]+, 200 [M –
2CH2CH3 – 2CO]+. C22H18O2 (314.382): calcd. C 84.05, H 5.77;
found C 83.87, H 5.67.
Method D: 5-Br (0.060 g, 0.287 mmol) was dissolved in DMF
(2 mL). Next [Pd(PPh3)4] 0.013 g, 0.011 mmol, 4 mol-%) was
added. The mixture was heated at 100 °C for around 20 h. DMF
was evaporated under oil-pump vacuum and the residue was dis-
solved in CH2Cl2 (1 mL) and filtered through a silica plug (ca.
6 cm) to give 8 as a yellow powder in 72% yield (0.027 g,
0.103 mmol). M.p. 123 °C (decomp.). 1H NMR (500 MHz,
CDCl3): δ = 10.01 (s, 1 H, CHO), 7.85 (d, JHH = 8 Hz, 2 H, Ph),
7.67 (d, JHH = 8 Hz, 2 H, Ph) ppm. 13C{1H} NMR (125 MHz,
CDCl3): δ = 191.2 (s, 1 C, CO), 136.2 (s, 1 C, p-Ph), 133.1 (s, 2 C,
o-Ph), 129.6 (s, 2 C, m-Ph), 127.5 (s, 1 C, i-Ph), 82.1 (s, 1 C, CCPh),
C6H5COC6H4(CϵC)2C6H4COC6H5 (11). Method B: Compound 3
(0.300 g, 1.077 mmol), wet TBAF (0.216 mL, 1.0  solution in
THF, 20 mol-%), Me3SiCl (0.136 mL, 1.077 mmol), CuCl (0.106 g,
1.077 mmol) and TMEDA (0.064 mL, 0.424 mmol) were combined
in a procedure analogous to that for 8 (Method B). Analogous
work-up gave 11 as a yellow powder in 75% yield (0.166 g,
0.404 mmol). M.p. 185 °C. 1H NMR (500 MHz, CDCl3): δ = 7.82–
7.50 (m, 9 H, Ph) ppm. 13C{1H} NMR (125 MHz, CDCl3): δ =
195.6 (s, 1 C, CO), 137.7 (s, 1 C, iЈ-Ph), 137.0 (s, 1 C, p-Ph), 132.7
(s, 1 C, pЈ-Ph), 132.3 (s, 2 C, o-Ph), 130.0 (s, 2 C, oЈ-Ph), 129.8 (s,
2 C, m-Ph), 128.3 (s, 2 C, mЈ-Ph), 125.5 (s, 1 C, i-Ph), 81.8 (s, 1 C,
76.4 (s, 1 C, CCPh) ppm. IR (KBr): ν = 2210 (w, νCϵC), 1928 (w,
˜
νC=O) 1697 (s) cm–1. MS: m/z = 258 [M]+, 229 [M – HCO]+, 200
[M – 2HCO]+. C18H10O2 (258.068): calcd. C 83.70, H 3.91; found
C 83.54, H 3.87.
CCPh), 76.3 (s, 1 C, CCPh) ppm. IR (KBr): ν = 2105 (w, νCϵC),
˜
1941 (w, νC=O), 1650 (s) cm–1. C30H18O2 (410.470): calcd. C 87.78,
H 4.42; found C 87.32, H 4.51.
CH3COC6H4(CϵC)2C6H4COCH3 (9). Method B:
2 (0.230 g,
1.063 mmol), wet TBAF (0.213 mL, 1.0  solution in THF, 20 mol-
%), SiMe3SiCl (0.134 mL, 1.063 mmol), CuCl (0.421 g,
4.252 mmol) and TMEDA (0.257 mL, 1.700 mmol) were combined
in a procedure analogous to that for 8 (Method B). Analogous
work-up gave 9 as a yellow powder in 75% yield (0.114 g,
0.398 mmol).
Details of X-ray Data Collection and Reduction: X-ray diffraction
data were collected by using a KUMA KM4 CCD (ω scan tech-
nique) diffractometer equipped with an Oxford Cryosystem cryos-
tream cooler.[37] The space groups were determined from systematic
absences and subsequent least-squares refinement. Lorentz and po-
larization corrections were applied. The structures were solved by
direct methods and refined by full-matrix least-squares on F2 using
the SHELXTL Package.[38] Non-hydrogen atoms were refined with
anisotropic thermal parameters. Hydrogen atom positions were cal-
culated and added to the structure factor calculations, but were not
refined.
Method C: 6-I (0.065 g, 0.241 mmol) and [Pd(PPh3)4] (0.011 g,
0.010 mmol, 4 mol-%) were combined in a procedure analogous to
that for 8 (Method C). Analogous work-up gave 9 as a yellow pow-
der in 29% yield (0.010 g, 0.035 mmol).
Method D: 6-Br (0.082 g, 0.368 mmol) and [Pd(PPh3)4] (0.017 g,
0.015 mmol, 4 mol-%) were combined in a procedure analogous to
that for 8 (Method D). Analogous work-up gave 9 as a yellow pow-
der in 90% yield (0.047 g, 0.165 mmol). M.p. 176 °C. 1H NMR
(500 MHz, CDCl3): δ = 7.91 (d, JHH = 8 Hz, 2 H, Ph), 7.59 (d,
CCDC-682769 (for 9), CCDC-682770 (for 10), and CCDC-682771
(for 11) contain the supplementary crystallographic data for this
paper. These data can be obtained free of charge from The Cam-
bridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
JHH = 8 Hz, 2 H, Ph), 2.59 (s, 3 H, CH3) ppm. 13C{1H} NMR data_request/cif.
Eur. J. Org. Chem. 2008, 4598–4606
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
4605

K. Osowska, T. Lis, S. Szafert
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Acknowledgments
[17]
[18]
The authors would like to thank the Polish State Committee for
Scientific Research (Grants N204 140 31/3236 and N204 134 31/
3125) for support of this research.
[1] In this paper the term polyyne is used for compounds with two
or more conjugated CϵC bonds.
[2] a) F. Bohlmann, H. Burkhardt, C. Zdero, Naturally Occurring
Acetylenes, Academic Press, New York, 1973; b) A. L. K. S.
Shun, R. R. Tykwinski, Angew. Chem. Int. Ed. 2006, 45, 1034,
and references cited therein.
[3] a) H. G. Cutler (Ed.), Biologically Active Natural Products -
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Published Online: August 5, 2008
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