One-pot desilylation/dimerization of terminal alkynes by ruthenium and acid-promoted (RAP) catalysis

Article abstract of DOI:10.1002/adsc.201000347

The dimerization of terminal arylalkynes promoted by the (p-cymene)ruthenium dichloride dimer/acetic acid system {[RuCl ₂(p-cymene)]₂/AcOH} can be performed starting from the trimethylsilylethynyl derivatives (12 substrates), deprotected in situ, to afford 1,4-disubstituted 1-en-3-ynes with high regio- and (E)-stereoselectivity, at room temperature. The extension of this unprecedented two-reaction sequence to a diyne substrate affords a fluorene-based conjugated oligomer. The reaction mixture resulting from the desylilation-dimerization process dimerizes additional aliquots of phenylacetylene. The one-pot protocol results in shorter reaction times due to the presence of acetate salts which increase the concentration of active catalytic species, in which the acetate ligand acts as base toward the bound alkyne. The ruthenium source is transformed into a new trihapto-hexa-1,3-dien-5-yn-3-yl complex, formed by metal-assisted coupling of the enyne product and the terminal alkyne, and still maintaining catalytic activity. Selectivity, endurance, medium and functional group compatibility are the key features of the catalytic system obtained from the p-cymene ruthenium dimer under the one-pot conditions.

Full text of DOI:10.1002/adsc.201000347

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DOI: 10.1002/adsc.201000347
One-Pot Desilylation/Dimerization of Terminal Alkynes by
Ruthenium and Acid-Promoted (RAP) Catalysis
Chiara Pasquinia and Mauro Bassettia,*
a
CNR, Istituto di Metodologie Chimiche, Sezione Meccanismi di Reazione, and Dipartimento di Chimica, Universitꢀ degli
Studi di Roma “La Sapienza”, P. le A. Moro 5, 00185 Roma, Italy
Fax : (+39)-06-490421; phone: (+39)-06-49913769; e-mail: mauro.bassetti@uniroma1.it
Received: May 4, 2010; Revised: August 24, 2010; Published online: October 12, 2010
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/adsc.201000347.
Abstract: The dimerization of terminal arylalkynes
promoted by the (p-cymene)ruthenium dichloride
dimer/acetic acid system {[RuCl2ACTHUNGRTNE(NUG p-cymene)]2/
the optimization of the reaction chemio-/regio-/ste-
reoselectivity, otherwise a major concern, and of cata-
lyst performance,[1,4] the application profile of this
process in organic synthesis remains limited.[1,3] With
respect to the catalyst, significant restrictions are rep-
resented by the need for the transition metal com-
plexes with the desired selectivity to be prepared ad
hoc, often requiring multistep organometallic synthe-
ses,[1b,4] and by the poor tolerance toward substrate
polar groups and moisture in the reaction medium.[5]
With regard to the organic substrate, the higher stabil-
ity of trialkylsilyl-protected ethynyl derivatives with
respect to the corresponding free alkynes would
imply significant advantages in using the former as
starting materials. In fact, the use of the terminal
alkyne generated in situ can avoid the separation pro-
cedures and any implicit handling or stability con-
cerns. Most of all, synthetic ethynyl substrates are
most conveniently accessed by Sonogashira-type reac-
tions between trialkylsilylacetylene and aromatic ha-
AcOH} can be performed starting from the trime-
thylsilylethynyl derivatives (12 substrates), depro-
tected in situ, to afford 1,4-disubstituted 1-en-3-ynes
with high regio- and (E)-stereoselectivity, at room
temperature. The extension of this unprecedented
two-reaction sequence to a diyne substrate affords a
fluorene-based conjugated oligomer. The reaction
mixture resulting from the desylilation-dimerization
process dimerizes additional aliquots of phenylace-
tylene. The one-pot protocol results in shorter reac-
tion times due to the presence of acetate salts
which increase the concentration of active catalytic
species, in which the acetate ligand acts as base
toward the bound alkyne. The ruthenium source is
transformed into a new trihapto-hexa-1,3-dien-5-yn-
3-yl complex, formed by metal-assisted coupling of
the enyne product and the terminal alkyne, and still
maintaining catalytic activity. Selectivity, endurance,
medium and functional group compatibility are the
key features of the catalytic system obtained from
the p-cymene ruthenium dimer under the one-pot
conditions.
AHCTUNGTRENNUNG
lides,[1b,6] the terminal triple bond being then liberated
by removal of the trialkylsilyl group [Eq. (1)].
À
Keywords: alkyne dimerization; C C coupling;
enynes; polyaddition; ruthenium catalysts
While there are no reports regarding the use of this
approach in the synthesis of enynes from terminal al-
The catalytic dimerization of terminal alkynes is in kynes, the in situ desilylation/oxidative coupling of tri-
principle a useful atom-economic methodology for alkylsilylacetylenes yielding symmetrically and un-
À
the synthesis of 1,4-disubstituted enynes via C(sp)
symmetrically substituted 1,3-diynes is a known pro-
C
A
of particular interest as the grouping occurs in natural conjugated polyyne materials.[7]
products[2] as well as in materials with optoelectronic
We reported recently that a catalytic system com-
properties.[1b,3] Notwithstanding the improvements in posed of the commercially available ruthenium com-
Adv. Synth. Catal. 2010, 352, 2405 – 2410
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tries 1 and 2), substrates bearing ortho or electron-
withdrawing groups were allowed to react for 24 h.
The steric hindrance of a methyl group in the ortho
position (entry 3) or the coordinating ability of the ni-
trile moiety toward ruthenium did not inhibit the cat-
alytic activity of the system (entry 6). 4-Ethynylben-
zaldehyde was converted selectively into the (E)-
enyne dimer (entry 7), while only the (Z)-isomer is
otherwise accessible by ruthenium catalysis.[5a] The di-
merization of the protic salicylaldehyde ethynyl deriv-
Scheme 1. Dimerization of arylalkynes catalyzed by I/
AcOH.
plex [RuCl2ACHTUNGTRENNUNG(p-cymene)]2 (I) and acetic acid promotes ative afforded a bifunctional aromatic enyne poten-
the dimerization of arylalkynes and affords 1,4-diaryl- tially useful for the coordination of transition metal
1-buten-3-ynes with high (E)-stereoselectivity under ions (entry 8).
mild reaction conditions (Scheme 1).[8]
Polycyclic derivatives gave decreased yields of
The catalytic species is formed upon interactions of enyne products and progressive loss of selectivity (en-
the three components: complex, acetic acid and tries 9 and 10), the gem isomer becoming favoured
alkyne. This methodology was then extended to upon increased congestion at the reaction center in
diynic starting materials, thus affording phenylene- the anthracene derivative. However, the reactions of
ethynylene-vinylene oligomers and polymers via a 2- and 3-(trimethylsilylethynyl)thiophene were char-
stepwise polyaddition process.[9]
acterized by competitive cyclotrimerization and dime-
We describe here that the two-reaction sequence in- rization processes (entries 11 and 12).
ꢀ
volving (i) the deprotection of ArC CSiMe3 sub-
strates and ii) the C C bond forming step promoted 2 afforded the corresponding fluorene-(E)-enyne oli-
The extension of the one-pot protocol to the diyne
À
by the I/AcOH system can be performed consecutive- gomer (2a, Scheme 2),[9b] as the first example of a
ly in the same reaction flask.
polyACTHGNUTERNNUaG ddition process performed on a trialkylsilyl-pro-
In the model substrate PhC CSiMe3, silyl deprotec- tected substrate.[1b,3b] Isolated as wholly soluble mate-
tion was performed using the common procedure rial in 55% yield, 2a is characterized by a number-
based on aqueous NaOH (5M) in MeOH/THF averaged molecular weight (Mn) of 2100 gmolÀ1 with
(method A):[10] a reaction time of 30 min at room a polydispersity index (Mw/Mn) of 1.8 (Mw =weight-
temperature ensured complete conversion into phe- averaged molecular weight), as determined by gel per-
nylacetylene (1). Without further manipulation, a so- meation chromatography, and by an average number
lution of complex I in acetic acid was then added into of repeat units (nAV) of 5.3, as determined by
the Schlenk tube, and the dimerization process al- 1H NMR spectroscopy. Due to the interest in using
lowed to proceed under argon. The yield of the enyne easily handled bis-ethynylsilanes under simplified pro-
product 1,4-diphenyl-1-buten-3-yne (1a, 60%, E:Z, cedures for the synthesis of conjugated polymers,[13]
ꢀ
1
99:1, determined by H NMR and GC) after 6 h was this finding opens the way to further developments.
higher than that observed from the catalytic dimeriza-
Following the one-pot desylilation-dimerization of
tion of 1 in neat AcOH after 45 h (55%).[8] This one- PhC CSiMe3, the reaction mixture remained catalyti-
ꢀ
ꢀ
pot protocol was then tested employing n-Bu4NF/ cally active. Sequential additions of PhC CH were
AcOH (1 equiv.) in THF (method B),[11,12] as alterna- converted in each run into 1a by the initial catalyst
tive to the desilylation step by NaOH. The same re- load, as shown in Table 2. The GC analysis of the re-
sults (within error limits) were obtained regarding action mixture performed after 46 h of overall reac-
yield and stereoselectivity of 1a. The use of the fluo- tion time showed 15 mol% of residual alkyne and
ride source avoids the aqueous highly basic medium 76 mol% conversion into the enyne (run 5). This cor-
ꢀ
which can be incompatible with some functional responds to the conversion of 3.5 mmol of PhC CH
groups such as nitriles or aldehydes. These results catalyzed by 1 mol% of the dinuclear ruthenium pre-
showed the compatibility of the I/AcOH catalytic catalyst I (or 2 mol% of a mononuclear ruthenium
system with the medium and by-products resulting species), with a turnover number (TON) of 73. The
from the desilylation step in either a basic or acidic residual alkyne was further converted into the enyne
medium as well as an unexpected higher activity (run 5’). These sequential transformations of 1 show
under the one-pot conditions.
In order to assess the functional group compatibili- cymene)]2/AcOH under the one-pot conditions.
ty and to expand the scope of the dimerization reac- Due to the moderate yields of dimers, we extended
the robustness of the catalytic system [RuCl2ACHTUNGTRENNUNG(p-
tion catalyzed by I/AcOH, the one-pot protocols were further the product analysis, and details are given
extended to a new set of various aromatic 1-alkynes. here for the reaction of 1-trifluoromethyl-3-trimethyl-
The results are summarized in Table 1. While 3,5- silylethynylbenzene (entry 5 in Table 1). Following
ꢀ
(MeO)2C6H4C CH was consumed within 7 h (en- the separation of the desired enyne from the chroma-
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One-Pot Desilylation/Dimerization of Terminal Alkynes
Table 1. One-pot desilylation/dimerization of aromatic 1-alkynes.
Entry
Substrate[a]
Step 1[b]
Time [h][c]
Yield[d] [%]
E:Z:gem[e]
1
2
A
B
7
7
48
47
99:1:0
90:10:0
3
4
5
A
A
A
24
24
24
47
69
35
96:4:0
99:0:0
84:16:0
6
7
B
B
6
42
47
99:1:0
96:4:0
24
8
9
B[f]
A
24
24
51
25
99:0:0
92:8:0
10
11
A
24
29
29:23:47
B
6
6
64[g]
67[h]
81:19:0
98:2:0
12
A
[a]
1.0–1.7 mmol (entry 8: 2.75 mmol).
Method of desilylation.
Step 2: reaction time after addition of I dissolved in AcOH.
[b]
[c]
[d]
[e]
[f]
Isolated yields.
Determined by H NMR.
1
3 h.
[g]
[h]
Combined yields of dimerization and cyclotrimerization products (22% of enynes).
Combined yields of dimerization and cyclotrimerization products (57% of enynes).
tographic column in hexane, a dark red solid was then posed by the doublets (5.16 and 4.67 ppm, J=
eluted using increasing portions of acetone. The 11.1 Hz) of two trans protons of a h3-allylic moiety.[4h]
1H NMR spectrum of this material showed the well The 13C NMR spectrum exhibited
a
signal at
À
defined signals of ruthenium-coordinated p-cymene, 181.8 ppm, due to a vinylic =C Ru carbon atom,
in the range 5.8–4.7 ppm, and a multiplet of 3- whereas the presence of an unbound triple bond was
CF3C6H4- moieties in the aromatic region, in the rela- observed as a band at 2202 cmÀ1 in the infrared spec-
tive ratio 1:3 (p-cymene/CF3C6H4). The signals at trum. These data are consistent with the structure of
lower frequencies of the p-cymene ring were superim- a h3-hexa-1,3-dien-5-yn-3-yl complex in which the or-
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still a dimerization catalyst, converting phenylacety-
lene into the enyne 1a (70%) after 24 h in acetic acid
(at room temperature). Red complexes with similar
spectroscopic features were isolated from the reac-
tions of other substrates in Table 1, and their charac-
terization will be reported in due course.
The dimerization processes proceed in the presence
of tetrabutylammonium or sodium acetate, which
form as the by-product of the desilylation by the fluo-
ride source (method B), or upon addition of I/AcOH
(method A), respectively. In attempts to rationalize
the observed faster conversion of the free alkynes
with respect to the reactions catalyzed by complex I
in neat acetic acid,[8] the reactivity of PhC CH was
ꢀ
checked upon addition of equimolar NaOAc, in order
to simulate the one-pot conditions, other factors such
as the precise medium composition remaining differ-
ent. The rates of consumption of the alkyne 1 and for-
Scheme 2. One-pot synthesis of oligo-fluorene-ethynylene-
vinylene 2a.
1
mation of the enyne (E)-1a, as followed by H NMR
Table 2. Series of catalytic cycles performed by [RuCl2ACTHNUTRGNE(UNG p-
in the presence or absence of NaOAc, are shown in
the plot of Figure 1. The first order analysis of the dis-
appearance of 1 yields half-life (t1/2) values of 394 and
44 min for the reactions in the absence or presence of
the acetate salt, respectively. A higher rate of forma-
tion of 1a was also observed in the presence of n-
Bu4NOAc (see the Supporting Information). In addi-
tion, there is no evidence for a slow activation stage,
which is otherwise apparent in the early stages of the
reaction without added acetate.
These results highlight the dramatic effect of the
acetate anion as a promoter of the catalytic activity.
More detailed kinetic and mechanistic studies will
allow us to distinguish the contributions of specific
cymene)]2 under the one-pot conditions, upon sequential ad-
ditions of phenylacetylene (1).[a]
Run
Alkyne
Time
[h][b]
1
A
Conversion
ACHTUNGTRENNUNG
[mmol][d]
[mmol][c]
ꢀ
1
PhC CSiMe3
4
4
15
5
18
8
0.03
0.10
0.18
0.47
0.69
0.57
0.72
1.81
2.31
2.70
3.50
3.63
2[e]
3[e]
4[e]
5[e]
5’
PhC CH
ꢀ
ꢀ
PhC CH
ꢀ
PhC CH
ꢀ
PhC CH
–
[a]
ꢀ
Reaction conditions in run 1: 1) PhC CSiMe3
(0.95 mmol), TBAF (1.0 mmol) in THF (1.05 mL),
AcOH (45 mL), bibenzyl (0.10 mmol), 30 min; 2)
(0.048 mmol), AcOH (5 mL).
Reaction time of each cycle.
Residual 1.
mmol of 1 (overall) converted into 1a, on the basis of
GC-analysis with reference to bibenzyl as internal stan-
dard.
I
[b]
[c]
[d]
[e]
1 (100 mL, 0.91 mmol).
ganic ligand arises by the coupling of three molecules
of alkyne. The ESI-TOF mass spectrum, with a cluster
of peaks centered at m/z=803.1 ([M+Na]+) and a
most intense one at m/z=745.2 ([MÀCl]+) establishes
the molecular formula {Ru(h6-p-cymene)Cl[h3-
ꢀ
ArCHCHC=C(Ar)C CAr]} (3, Ar=3-CF3C6H4) of
this new ruthenium complex. The isolated amount of
3 accounts for 51 mol% of the ruthenium source and
for 15 mol% of the terminal alkyne. Complex 3 was
1
observed by H NMR in the crude reaction mixture,
so that it did not form upon chromatography. A simi-
lar hexadienylyne complex with h3-allyl coordination
was isolated and fully characterized in the course of
the dimerization of phenylacetylene catalyzed by the
ꢀ
Figure 1. Time evolution of PhC CH (1, circles, 10 mL,
0.178m) and of (E)-PhCH=CH C CPh (1a, squares) in the
À ꢀ
reactions catalyzed by complex I (2.4 mg, 7.8 mM, 4.3%), in
the absence or presence of NaOAc (8 mg, 0.19M) in
CD3CO2H (0.50 mL), at 29.18C. The solid lines represent
(h5-C5Me5)Cl
vinylidene complex [RuACHTGNUTRENNNGU AHCTUNRTGEG(NNUN PPh3)ACHTNUGERTN(NUGN =C=
CHPh)] in the presence of Et3N.[4h] Compound 3 is the fitting with the first-order rate equation.
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One-Pot Desilylation/Dimerization of Terminal Alkynes
Scheme 3. Proposed activation stage in RAP catalysis.
Scheme 4. Proposed formation of complex 3 (Ar=3-CF3C6H4).
counteranions and of generic polarity effects. Howev-
In summary, 1,4-diarylsubstituted enynes with di-
er, it can be anticipated that the reaction of phenyl- verse functional groups can be obtained under mild
acetylene did not give any evidence of improved reac- conditions from silane substrates. The catalytic system
tivity in a saturated solution of n-Bu4NPF6. To explain resulting from [RuCl2A(p-cymene)]2/AcOH, active at
ACHTUNGTRENNUNG
CTHUNGTRENNUNG
the catalytic behaviour of the I/AcOH system, taking room temperature and (E)-stereoselective, tolerates
into account the role of acetic acid, we previously aqueous reagents, the by-products of the deprotection
proposed an initiation stage involving release of HCl step, and polar/protic substituents in the aryl ring.
from complex I and formation of monomeric [RuCl- The RAP procedure, based on readily available start-
ACHTUNGTRENNUNG(p-cymene)ACHTUNGTRENNUNG(OAc)] or [RuACHTUNEGRTG(NNUN p-cymene)ACHTNGURTEN(NUNG OAc)2]. Such ing materials and simple experimental protocols, can
complexes, in particular the chloride species, are therefore be regarded as a promising and practical
known to form under mild conditions from the ruthe- tool for the synthesis of E-enyne systems.
nium dimeric precursor in polar protic solvents.[14]
Fast exchange between bidentate (18-e) and mono-
dentate (16-e) acetato species allows then the coordi-
Experimental Section
nation of the alkyne and the onset of the catalytic
cycle.[9a] As depicted in Scheme 3, the new observa-
General Procedures of Desilylation/Dimerization
tions support this hypothesis: excess sodium acetate
provides a higher concentration of the active species,
thus enhancing the overall catalytic performance. The substrate in THF (1 equiv., 0.7M), an equal volume of a
To a stirring solution of the aromatic trimethylsilylethynyl
methanolic mixture of aqueous NaOH (1.25 equiv., 5M)
was added dropwise (method A). Alternatively, the sub-
strate, acetic acid (1 equiv.) and tetrabutylammonium fluo-
ride (1.1 equiv.) in THF (1M) were introduced into a
Schlenk tube (method B). The mixture was then stirred at
room temperature for 30 min. Unless stated otherwise (see
Table 1), the GC analysis of a sample withdrawn from the
reaction mixture showed quantitative transformation into
the corresponding terminal alkyne, under the conditions of
bound acetate can act as intramolecular base toward
the p-alkyne and generate AcOH and an arylacety-
lide derivative. Substitution by the second alkyne
molecule, most likely rapid p-alkyne-vinylidene tauto-
À
merization, and subsequent C C bond formation via
acetylide-vinylidene coupling, afford a s-enynyl spe-
cies, from which the organic enyne is then liberated
by protonation.[1b,8]
The same acetylide species involved in the catalytic
both methods A and B. Acetic acid and [RuCl2ACTHUNTRGNEU(GN p-cymene)]2
cycle accounts for the formation of the hexa-1,3-dien- (5 mol%) into separate Schlenk tubes were degassed by
argon/vacuum cycles. Then, (i) acetic acid (2.5 mL per mmol
of substrate) and (ii) a solution of I in acetic acid (3.1 mL
per mmol of substrate) were transferred in sequence into
the reaction tube via cannula. The solution was stirred at
room temperature and the reaction progress was followed
by means of GC and GC-MS analyses. Unless stated other-
wise, the reaction was interrupted when the conversion of
the terminal alkyne was estimated to be over 90%. The re-
action mixture was poored into dichloromethane, and ex-
tracted with water and aqueous NaHCO3. The organic
layers were dried over sodium sulfate, then filtered and
5-yn-3-yl complex 3, generated by alkyne insertion
into the ruthenium acetylide bond (Scheme 4).
The role of the acetate ligand in base-assisted
proton abstraction finds various analogies in the liter-
ature, in particular in the case of the activation of sp2-
À
C H bonds by oxygenated anions, a phenomenon
which is gaining increasing recognition and interest in
organometallic catalysis.[15] To the best of our knowl-
edge, this work reports the first case of activation of
terminal alkynes by bound acetate.
Adv. Synth. Catal. 2010, 352, 2405 – 2410
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Chiara Pasquini and Mauro Bassetti
COMMUNICATIONS
evaporated to dryness. The crude mixtures were then puri-
fied by column chromatography (silica/hexanes or silica/hex-
anes/CH2Cl2). See the Supporting Information for details on
each synthesis.
367; h) C. S. Yi, N. Liu, A. L. Rheingold, L. M. Liable-
Sands, Organometallics 1997, 16, 3910–3913.
[5] By contrast, the dimerization of 1-alkynes is feasible in
aqueous media by ruthenium catalysis: a) X. Chen, P.
Xue, H. H. Y. Sung, I. D. Williams, M. Peruzzini, C.
Bianchini, G. Jia, Organometallics 2005, 24, 4330–4332;
b) P. Novak, M. Kotora, Collect. Czech. Chem.
Commun. 2009, 74, 433–442; c) C.-K. Chen, H.-C.
Tong, C.-Y. C. Hsu, C.-Y. Lee, Y. H. Fong, Y.-S.
Chuang, Y.-H. Lo, Y.-C. Lin, Y. Wang, Organometallics
2009, 28, 3358–3368.
Supporting Information
Experimental procedures and characterization data of the
1
enyne products and of complex 3, with figures of H and
13C NMR spectra, plot for the reaction of 1 in the presence
of n-Bu4NOAc, synthesis and fluorescence spectra of 2a are
given in the Supporting Information.
À
[6] H. Plenio, A. Datta, in: Handbook of C H Transfor-
mations, Vol. 1, (Ed.: G. Dyker) Wiley-VCH, Wein-
heim, 2005, Chapter II.
Acknowledgements
[7] a) M. A. Heuft, S. K. Collins, G. P. A. Yap, A. G. Fallis,
Org. Lett. 2001, 3, 2883–2886; b) P. S. Siemsen, R. C.
Livingston, F. Diederich, Angew. Chem. 2000, 112,
2740–2767; Angew. Chem. Int. Ed. 2000, 39, 2632–
2657, and references cited therein.
The authors are grateful to Dr. Silvia Bartocci for the synthe-
sis of 4-(trimethylsilylethynyl)salicylaldehyde. The invitation
of the reviewers to describe the catalytic activity in additional
cycles and the fate of the ruthenium catalyst is greatly appre-
ciated.
[8] M. Bassetti, C. Pasquini, A. Raneri, D. Rosato, J. Org.
Chem. 2007, 72, 4558–4561.
[9] a) C. Pasquini, I. Fratoddi, D. Capitani, L. Mannina, M.
Bassetti, J. Org. Chem. 2008, 73, 3892–3899; b) C. Pas-
quini, I. Fratoddi, M. Bassetti, Eur. J. Org. Chem. 2009,
5224–5231.
[10] a) S. J. Harris, D. R. M. Walton, Tetrahedron 1978, 34,
1037–1042; b) H. Meier, D. Ickenroth, U. Stalmach, K.
Koynov, A. Bahtiar, C. Bubeck, Eur. J. Org. Chem.
2001, 4431–4443.
References
[1] Reviews: a) B. M. Trost, A. McClory, Chem. Asian J.
2008, 3, 164–194; b) E. Bustelo, P. H. Dixneuf, in:
Handbook of C-H Transformations, Vol. 1, (Ed.: G.
Dyker), Wiley-VCH, Weinheim, 2005, Chapter II; c) V.
Ritleng, C. Sirlin, M. Pfeffer, Chem. Rev. 2002, 102,
1731–1769.
[11] A. L. Korich, T. S. Hughes, Org. Lett. 2008, 10, 5405–
5408.
[2] a) Chemistry and Biology of Naturally Occurring Acety-
lenes and Related Compounds, (Eds.: J. Lam, H. Bretel-
er, T. Arnason, L. Hansen), Elsevier, Amsterdam,
1998; b) N. Li, Z. Shi, Y. Tang, J. Chen, X. Li, Beilstein
J. Org. Chem. 2008, 4, 48.
[3] a) Y. Liu, M. Nishiura, Y. Wang, Z. Hou, J. Am. Chem.
Soc. 2006, 128, 5592–5593; b) H. Katayama, M. Na-
kayama, T. Nakano, C. Wada, K. Akamatsu, F. Ozawa,
Macromolecules 2004, 37, 13–17.
[4] Selected references concerning the catalytic dimeriza-
tion of 1-alkynes: a) A. Hijazi, K. Parkhomenko, J.-P.
Djukic, A. Chemmi, M. Pfeffer, Adv. Synth. Catal.
2008, 350, 1493–1496; b) W. Weng, C. Guo, R. C¸ elenli-
gil-C¸ etin, B. M. Foxman, O. V. Ozerov, Chem.
Commun. 2006, 197–199; c) H. Katayama, H. Yari, M.
Tanaka, F. Ozawa, Chem. Commun. 2005, 4336–4338;
d) M. Nishiura, Z. Hou, Y. Wakatsuki, T. Yamaki, T.
Miyamoto, J. Am. Chem. Soc. 2003, 125, 1184–1185;
e) K. Melis, T. Opstal, F. Verpoort, Eur. J. Org. Chem.
2002, 3779–3784; f) C. Yang, S. P. Nolan, J. Org. Chem.
2002, 67, 591–593; g) T. Ohmura, S. Yorozuya, Y. Ya-
mamoto, N. Miyaura, Organometallics 2000, 19, 365–
[12] The deprotection of the trimethylsilylethynyl substrate
needs to be complete before addition of the dimeriza-
tion promoters, since excess acetic acid consumes the
hydroxide or quenches the nucleophilicity of the fluo-
ride ions.
[13] T. Dutta, K. B. Woody, M. D. Watson, J. Am. Chem.
Soc. 2008, 130, 452–453.
[14] a) D. A. Tocher, R. O. Gould, T. A. Stephenson, M. A.
Bennett, J. P. Ennett, T. W. Matheson, L. Sawyer, V. K.
Shah, J. Chem. Soc. Dalton Trans. 1983, 1571–1581;
b) D. L. Davies, O. Al-Duaij, J. Fawcett, M. Giardiello,
S. T. Hilton, D. R. Russell, Dalton Trans. 2003, 4132–
4138; c) M. Melchart, A. Habtemariam, S. Parsons,
S. A. Moggach, P. J. Sadler, Inorg. Chim. Acta 2006,
359, 3020–3028.
[15] a) D. Garcꢂa-Cuadrado, P. de Mendoza, A. A. C. Braga,
F. Maseras, A. M. Echavarren, J. Am. Chem. Soc. 2007,
129, 6860–6886; b) I. ꢃzdemir, S. Demir, B. C¸ etinkaya,
C. Gourlaouen, F. Maseras, C. Bruneau, P. H. Dixneuf,
ˇ
J. Am. Chem. Soc. 2008, 130, 1156–1157; c) F. Pozgan,
P. H. Dixneuf, Adv. Synth. Catal. 2009, 351, 1737–1743.
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