Reactivity of 3-silyloxy-1,4-enynes: Gold(III)-catalyzed regioselective nucleophilic substitution

Article abstract of DOI:10.1016/j.jorganchem.2008.09.062

Gold-catalyzed reactions of 3-silyloxy-1,4-enynes with alcohols afford primary, secondary, and tertiary pent-2-en-4-ynyl ethers in moderate to excellent yields. The substitution proceeds with high regioselectivity. An initial cyclization providing five-me

Full text of DOI:10.1016/j.jorganchem.2008.09.062

Journal of Organometallic Chemistry 694 (2009) 510–514
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Reactivity of 3-silyloxy-1,4-enynes: Gold(III)-catalyzed regioselective
nucleophilic substitution
Timm T. Haug, Tobias Harschneck, Alexander Duschek, Chang-Uk Lee, Jörg T. Binder, Helge Menz,
*
Stefan F. Kirsch
Department Chemie, Technische Universität München, Lichtenbergstr. 4, D-85747 Garching, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 10 June 2008
Received in revised form 4 September 2008
Accepted 30 September 2008
Available online 8 October 2008
Gold-catalyzed reactions of 3-silyloxy-1,4-enynes with alcohols afford primary, secondary, and tertiary
pent-2-en-4-ynyl ethers in moderate to excellent yields. The substitution proceeds with high regioselec-
tivity. An initial cyclization providing five-membered carbocycles instead was not observed under the
reaction conditions. Control experiments show that these reactions are also catalyzed by Brønsted-
and Lewis-acids, although scope and yields are markedly reduced.
Ó 2008 Elsevier B.V. All rights reserved.
Keywords:
Nucleophilic substitution
Regioselectivity
Catalysis
Gold
3-silyloxy-1,4-enynes
1. Introduction
nes in the presence of gold catalysts was not further investigated.
We disclose herein our observations when using 3-silyloxy-1,4-
Within the rapidly developing field of catalysis involving homo-
geneous gold-complexes as carbophilic Lewis-acids [1], the diverse
reactivity of enynes has attracted particularly much interest [2].
The two most prominent classes that were employed in catalyzed
cycloisomerization reactions are 1,5-enynes [3] and 1,6-enynes [4].
Recently, we have launched a research program that aims to sys-
tematically reveal the noble metal-catalyzed reactivity of 1,n-eny-
nes bearing either a free or a protected hydroxyl group at the 3-
position [5,6]. In 2007, we reported the construction of highly
substituted cyclopentenes from 3-silyloxy-1,5-enynes using cata-
lytic amounts of [(Ph3P)AuSbF6] and i-PrOH as a proton source
[7]. This product formation was explained by assuming a cascade
reaction consisting of 6-endo carbocyclization and pinacol-type
1,2-migration. For example, reaction of enyne 1 in CH2Cl2 at room
temperature produced the bicyclic compound 2 in good yield (93%)
(Eq. (1)). In a related cascade reaction, 3-silyloxy-1,6-enynes can
react through a pathway combining an initial 6-exo carbocycliza-
tion and a subsequent pinacol rearrangement (Eq. (2)) [8]. In
addition, 3-silyloxy-1,6-enynes were found to undergo a sequence
of heterocyclization followed by a Claisen rearrangement depend-
ing on the substitution pattern of the substrates and the electronic
properties of the gold-bound phosphane ligand. Despite the syn-
thetic value of these reactions, the reactivity of 3-silyloxy-1,4-eny-
enynes as substrates in gold-catalyzed reactions.
OSiEt3
[Au(PPh3)]Cl (10 mol%)
AgSbF6 (5 mol%)
i-PrOH
CHO
H
ð1Þ
ð2Þ
23 °C, CH2Cl2
(93%)
H
1
2
Ph
Ph
[Au(PPh3)]Cl (10 mol %)
AgSbF6 (5 mol %)
i-PrOH
O
Et3SiO
H
40 °C, CH2Cl2
(68%)
H
3
4
2. Results and discussion
We now report a regioselective nucleophilic substitution that
provides access to 5-alkoxy-pent-3-en-1-ynes from 3-silyloxy-
1,4-enynes and alcohols. In this work, gold(III) complexes are em-
ployed as precatalysts to activate the propargylic alcohol moiety
that is protected as a silyl ether. While gold(III) complexes have
received recent attention as catalysts for Friedel-Crafts-type
alkylations with benzylic alcohols and benzylic acetates,[9] their
* Corresponding author.
E-mail address: stefan.kirsch@ch.tum.de (S.F. Kirsch).
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.09.062

T.T. Haug et al. / Journal of Organometallic Chemistry 694 (2009) 510–514
511
use for the direct substitution of propargylic alcohols is rare. In this
K[AuCl4] (5 mol %)
OSiMe3
OR3
R3-OH (5 equiv)
context, Campagne and co-workers developed a protocol utilizing
Na[AuCl4] as catalyst for an efficient propargylic substitution with
various C-, O-, and S-nucleophiles [10]. Dyker and co-workers used
AuCl3 for the efficient propargylation of electron-rich arenes.[11]
Further catalytic methodologies [12] for the propargylic substitu-
tion take use of ruthenium [13], rhenium [14], bismuth [15], or
copper [16] catalysts. Simple Brønsted-acids such as p-toluenesul-
fonic acid were also found to catalyze the direct substitution of the
hydroxyl group in propargylic alcohols [17].
R1
R1
40 °C
CH2Cl2/CH3CN (10/1)
R2
: R1 = Me, R2 = Ph
R2
13
(98%; E:Z = 4:1)
R3 = Me
12
R
3 = i-Pr
14 (93%; E:Z = 3:1)
16 (85%; E:Z = 3:1)
17 (92%; E:Z = 3:1)
19
15: R1 = Me, R2 = 4-Me(C6H4) R3 = Me
3 = i-Pr
R3 = Me
3 = i-Pr
R
: R1 = Ph, R2 = Ph
(70%; E:Z = 1.5:1)
(70%; E:Z = 1.3:1)
18
20
R
21: R1 = Me, R2 = n-Pent
23: R1 = n-Pr, R2 = Ph
25: R1 = Ph, R2 = H
R3 = i-Pr
R3 = CH2Ph
R3 = i-Pr
22 (42%; E:Z > 95:5)
24 (92%; E:Z = 2:1)
26 (43%; E:Z = 2:1)
We began our investigation into the reactivity of 3-silyloxy-1,4-
enynes by utilizing catalyst and reaction parameters optimized for
the conversion of silyl ether 5 [18]. While in the case of 5 the inter-
nal oxygen nucleophile facilitates an initial cyclization that finally
leads to the formation of spirocyclic 3-furanone 6, a related 5-endo
cyclization was not observed when using the analogous methy-
lene-containing silyl ether 7. Instead, activation by AuCl3 afforded
enyne 8 in 70% yield as the product of an exclusive nucleophilic
substitution that proceeds with excellent regioselectivity (Scheme
1) [19]. The reaction of substrate 7 was monitored by 1H NMR
spectroscopy indicating that substitution was the sole pathway
(besides partial cleavage of the silyl ether). Unfortunately, the
monitoring did not detect any trace products that might have re-
sulted from a CꢀC-bond forming cyclization as envisaged initially.
Although this catalyst system did prove efficient with the conver-
sion of a variety of 3-silyloxy-1,4-enynes, the scope was somewhat
limited due to the fact that the etherification products were typi-
cally accompanied by significant amounts of the corresponding
alcohols. As exemplified for the reaction of 3-silyloxy-1,4-enyne
9 (Scheme 2), both methyl ether 10 and alcohol 11 were obtained
in 59% yield and 29% yield, respectively. This observation might be
attributed to the hygroscopicity of AuCl3 under the open-flask con-
ditions employed for the described transformations (see Section 4).
An extensive screen with commercially available gold(I) and
gold(III) catalysts produced K[AuCl4] to be the catalyst system of
choice for the conversion of 3-trimethylsilyloxy-1-phenylhex-4-
en-1-yne (12) into (5-methoxyhex-3-en-1-ynyl)benzene (13)
[5mol%K[AuCl4], 5 equiv. MeOH, 40 °C, CH3CN/CH2Cl2 (1/10),
98%] (Scheme 3). Under these reaction conditions, the propargylic
substitution was performed under experimentally simple open-
flask conditions. Unlike in the case of AuCl3, the introduction of
water was not observed. Other gold catalysts such as
HAuCl4 ꢁ 4H2O, AuCl, and [(Me3P)AuSbF6] resulted in markedly re-
K[AuCl4] (5 mol %)
R3-OH (5 equiv)
OSiMe3
OR3
40 °C
CH2Cl2/CH3CN (10/1)
Ph
Ph
27
R3 = Me
R3 = i-Pr
28 (68%; E:Z > 95:5)
29
(41%; E:Z > 95:5)
K[AuCl4] (5 mol %)
R3-OH (5 equiv)
OSiMe3
R3O
40 °C
Ph
Ph
CH2Cl2/CH3CN (10/1)
R3 = Me
(75%; E:Z > 95:5)
(71%; E:Z > 95:5)
30
31
32
R
3 = i-Pr
K[AuCl4] (5 mol %)
R3-OH (5 equiv)
OSiMe3
40 °C
Ph
Ph
R3O
CH2Cl2/CH3CN (10/1)
33
R3 = Me
34 (52%; Z:E = 5:1)
35 (54%; Z:E = 5:1)
R
3 = i-Pr
Scheme 3. Propargylic substitution of 3-silyloxy-1,4-enynes with alcohols cata-
lyzed by K[AuCl4].
K[AuCl4] (5 mol %)
OSiMe3
TsNH2 (5 equiv)
TsHN
40 °C
CH2Cl2/CH3CN (10/1)
Ph
Ph
30
36 (34%; E:Z > 95:5)
K[AuCl4] (5 mol %)
O
OSiMe3
(5 equiv)
Ph
40 °C
CH2Cl2/CH3CN (10/1)
Ph
O
Ph
i-PrO
33
37
(32%; Z:E = 3:1)
O
AuCl3 (5 mol %)
X
Ph
i-PrOH (1.1 equiv)
Scheme 4. Nucleophilic substitution with N- and C-nucleophiles.
OSiMe3
23 °C, CH2Cl2
O
Ph
5: X = O
6 (81%)
duced yields (or full recovery of the starting material). PtCl2
(5 mol%, 120 °C, toluene) gave the product of the regioselective
substitution in 35% yield. Interestingly, Brønsted- and Lewis-acid
catalysts [e.g., Bi(OTf)3 (67%), p-TsOH (61%), and HBF4 (52%)] were
effective, but they did not exhibit the wide applicability observed
in the case of K[AuCl4].
7
8
(70%)
: X = CH2
Scheme 1. Comparison between the reactivity of 5 and 7 in the presence of AuCl3.
The scope of the reaction of 3-silyloxy-1,4-enynes with alcohols
(5 equiv) in the presence of 5 mol% K[AuCl4] is summarized in
Scheme 3. At 40 °C, reactions of 3-silyloxy-1,4-enynes bearing a
1,2-disubstituted alkene moiety with various alcohols provided
the corresponding ethers with excellent regioselectivity and good
yields (42–98%). In general, the products of the nucleophilic
substitution were obtained as an inseparable mixture of cis- and
trans-double bond isomers. The presence of both aryl and alkyl
substituents at the alkyne terminus was tolerated, albeit with a
MeO
AuCl3 (5 mol %)
Me-OH (5 equiv)
Ph
Ph
OSiMe3
10
11
(59%)
+
40 °C, CH2Cl2
Ph
HO
9
(29%)
Scheme 2. Use of AuCl3 in the regioselective substitution of 3-silyloxy-1,4-enynes.

512
T.T. Haug et al. / Journal of Organometallic Chemistry 694 (2009) 510–514
reduced yield for substrate 21 (R2 = n-Pent). The reaction of termi-
nal alkynes such as 25 was low-yielding and slow. Enyne 27 con-
taining a trisubstituted alkene reacted to give the tertiary ether
28 in moderate yield, as did substrates containing a different al-
kene substitution pattern.
Several additional observations merit note. Our current results
do not question the mechanistic details of this substitution that
may involve a SN1- or SN20-like nucleophilic attack. Nevertheless,
the triple bond was beneficial to the reaction outcome since either
no conversion or complete decomposition was obtained in the ab-
sence of the propargylic alcohol moiety. For example, 1-trimethyl-
silyloxy-1-phenylprop-2-ene decomposed under the reaction
conditions while 3-trimethylsilyloxy-oct-1-ene did not react. It
was not necessary to take special precautions to exclude air and
moisture from the reaction mixture. The reactions shown in
Scheme 3 were remarkably regioselective, producing primary, sec-
ondary, and tertiary ethers without the formation of any regio-
and the residue was purified by flash-chromatography on silica
(pentanes/EtOAc = 98:2). The product was isolated as a pale yellow
oil (82.8 mg, 0.29 mmol, 92%) containing the E and Z diastereoiso-
mer of 24 in a ratio of 2:1 (according to 1H NMR). 1H NMR
(250 MHz, CDCl3) d 0.88–0.95 (m, 3H E-isomer, 1.5H Z-isomer),
1.26–1.81 (m, 4H, E-isomer, 2H Z-isomer), 3.81–3.89 (m, 1H E-iso-
mer), 4.36–4.70 (m, 2H E-isomer, 1H Z-isomer), 5.87–5.93 (m, 1H
E-isomer, 0.5H Z-isomer), 6.16 (dd, J = 16.0, 7.4 Hz, 1H E-isomer),
7.27–7.46 (m, 10H E-isomer, 5H Z-isomer); 13C NMR (E-isomer,
90.6 MHz, CDCl3) d 14.1, 18.7, 37.8, 70.6, 79.3, 87.5, 90.1, 111.79,
123.4, 127.7, 127.9, 128.4, 128.5, 128.5, 131.7, 138.7, 144.4; MS
(70 eV) m/z (%): 290 (2) [M+], 247 (26), 204 (15), 91 (100), 71
(31). HRMS Calc. for C21H22O: 290.1671. Found: 290.1667.
4.3. Characterization data for the substitution products
4.3.1. (E/Z)-(5-Methoxyhex-3-en-1-ynyl)benzene (13)
1H NMR (360 MHz, CDCl3) d 1.28 (d, J = 6.4 Hz, 3H, E-isomer),
1.31 (d, J = 6.6 Hz, 0.69H, Z-isomer), 3.32 (s, 3H, E-isomer), 3.35
(s, 0.69H, Z-isomer), 3.78–3.85 (m, 1H, E-isomer), 4.40–4.48 (m,
0.23H, Z-isomer), 5.85–5.91 (m, 1H E-isomer, 0.46H Z-isomer),
6.11 (dd, J = 7.0, 15.9 Hz, 1H, E-isomer), 7.30–7.34 (m, 3H E-isomer,
0.70H Z-isomer), 7.43–7.45 (m, 2H E-isomer, 0.46H Z-isomer); 13C
NMR (E-isomer, 90.6 MHz, CDCl3) d 21.2, 56.5, 77.6, 87.4, 90.0,
111.1, 123.4, 128.4, 128.5, 131.7, 145.0. MS (70 eV) m/z (%): 186
(29) [M+], 171 (100), 153 (21), 128 (37), 115 (25). HRMS Calc. for
C13H14O: 186.1045. Found: 186.1048.
isomer. As
a
consequence of silyl ether cleavage, the
corresponding 3-hydroxy-1,4-enynes were occasionally identified
as significant by-products formed during the course of the reac-
tion. Nevertheless, the use of 3-hydroxy-1,4-enynes instead of 3-
silyloxy-1,4-enynes produced diminished yields (e.g., 78% for 14)
for the substitution whereas the reaction was slowed markedly.
With the corresponding propargylic acetate, substitution product
14 was obtained in 19% yield (E/Z = 2/1) under the reaction condi-
tions accompanied by a variety of undefined decomposition prod-
ucts. Enol ether or acetal formation [20] resulting from the direct
addition of the alcohols onto the alkyne moiety was not observed.
Other nucleophiles such as tosylamide [19] and furan reacted as
well with 3-silyloxy-1,4-enynes under gold catalysis; in these
cases, the substitution reactions proceeded with much lower yields
(Scheme 4).
4.3.2. (E/Z)-(5-Isopropoxyhex-3-en-1-ynyl)benzene (14)
1H NMR (360 MHz, CDCl3) d 1.14–1.21 (m, 6H E-isomer, 1.8H Z-
isomer), 1.25–1.30 (m, 3H E-isomer, 0.9H Z-isomer), 3.63–3.75 (m,
1H E-isomer, 0.3H Z-isomer), 4.01–4.08 (m, 1H, E-isomer), 4.61–
4.70 (m, 0.3H, Z-isomer), 5.77 (d, J = 11.1 Hz, 0.3H, Z-isomer),
5.85–5.92 (m, 1H E-isomer, 0.3H Z-isomer), 6.15 (dd, J = 6.8,
15.9 Hz, 1H, E-isomer), 7.29–7.34 (m, 3H E-isomer, 0.9H Z-isomer),
7.42–7.44 (m, 2H E-isomer, 0.6H Z-isomer); 13C NMR (E-isomer,
90.6 MHz, CDCl3) d 21.4, 21.8, 23.4, 69.1, 72.9, 87.6, 89.8, 109.9,
123.4, 128.4, 128.5, 131.5, 146.3. MS (70 eV) m/z (%): 214 (12)
[M+], 199 (28), 171 (51), 157 (100), 128 (51). HRMS Calc. for
C13H14O: 214.1358. Found: 214.1357.
3. Conclusion
In summary, we have studied gold-catalyzed reactions of 3-
silyloxy-1,4-enynes with alcohols. An attempted CꢀC-bond form-
ing cyclization failed, which clearly excludes 3-silyloxy-1,4-enynes
as precursors for five-membered carbocycles. Instead, a highly reg-
ioselective nucleophilic substitution was observed in the presence
of gold(III)-precatalysts. This reaction provides access to primary,
secondary, and tertiary pent-2-en-4-ynyl ethers.
4.3.3. (E/Z)-1-(5-Methoxyhex-3-en-1-ynyl)-4-methylbenzene (16)
1H NMR (360 MHz, CDCl3) d 1.28 (d, J = 6.4 Hz, 3H E-isomer),
1.31 (d, J = 6.4 Hz, 1H Z-isomer), 2.33 (s, 3H E-isomer), 2.34 (s, 1H
Z-isomer), 3.31 (s, 3H E-isomer), 3.35 (s, 1H Z-isomer), 3.78–3.85
(m, 1H E-isomer), 4.40–4.48 (m, 0.3H Z-Isomer), 5.84–5.89 (m,
1H E-isomer, 0.6H Z-isomer), 6.10 (dd, J = 15.9, 7.2 Hz, 1H E-iso-
mer), 7.11–7.27 (m, 4H E-isomer, 1.3H Z-isomer), 13C NMR (E-iso-
mer, 90.6 MHz, CDCl3) d 21.2, 21.4, 56.5, 77.6, 87.0, 90.2, 111.2,
123.2, 128.4, 128.7, 129.3, 132.2, 138.1, 144.8; MS (70 eV) m/z
(%):200 (26) [M+], 185 (100), 169 (11), 153 (14), 142 (23), 129
(15), 115 (15). HRMS Calc. for C14H16O: 200.1201. Found:
200.1204.
4. Experimental
4.1. General experimental details
All commercially available chemicals were used without further
purification. The 3-silyloxy-1,4-enynes were synthesized from the
corresponding enones by nucleophilic addition of the lithiated
acetylenes followed by silyl protection of the hydroxyl group. All
the substitution reactions were performed under open-flask condi-
tions without the use of an inert gas. For all compounds, the assign-
ment of double bond geometry is based on NOESY data. The 13C
NMR data given show the signals of the major diastereoisomer un-
less otherwise noted.
4.3.4. (E/Z)-1-(5-Isopropoxyhex-3-en-1-ynyl)-4-methylbenzene (17)
1H NMR (360 MHz, CDCl3) d1.13–1.18 (m, 6H E-isomer, 2H Z-iso-
mer), 1.20 (d, J = 6.1 Hz, 1H Z-isomer), 1.26 (d, J = 6.6, 3H E-isomer),
1.28 (d, J = 6.6, 1H Z-isomer), 2.33 (s, 3H E-isomer), 2.34 (s, 1H Z-
isomer), 3.61–3.77 (m, 1H E-isomer, 0.3H Z-isomer), 4.00–4.08
(m, 1H E-isomer), 4.62–4.70 (m, 0.3H Z-isomer),5.75–5.90 (m, 1H
E-isomer, 0.6H Z-isomer), 6.14 (dd, J = 15.9, 6.8 Hz, 1H E-isomer),
7.10–7.26 (m, 4H E-isomer, 1.3H Z-isomer), 13C NMR (E-isomer,
90.6 MHz, CDCl3) d 21.3, 21.9, 22.0, 23.4, 69.1, 73.0, 87.3, 90.0,
110.0, 123.3, 128.3, 128.7, 129.2, 132.2, 138.1, 146.2; MS (70 eV)
m/z (%): 228 (12) [M+], 213 (20), 185 (46), 171 (100), 153 (17),
4.2. General procedure for the substitution
4.2.1. (E/Z)-(5-(Benzyloxy)oct-3-en-1-ynyl)benzene (24)
85.0 mg of (E)-trimethyl(1-phenyloct-4-en-1-yn-3-yloxy)silane
(0.31 mmol) were dissolved in 3 mL CH2Cl2 and 0.16 mL benzylic
alcohol (169 mg, 1.56 mmol) were added. A solution of 5.89 mg
KAuCl4 (0.02 mmol) 1 m in MeCN was added and the reaction
mixture was stirred at 40 °C for 1.5 h. The solvent was evaporated

T.T. Haug et al. / Journal of Organometallic Chemistry 694 (2009) 510–514
513
143 (34), 128 (35), 115 (20). HRMS Calc. for C16H20O: 228.1514.
Found: 228.1511.
128.3, 128.4, 131.6, 150.0; MS (70 eV) m/z (%): 228 (8) [M+], 213
(17), 171 (100), 152 (15), 128 (16). HRMS Calc. for C16H20O:
228.1514. Found: 228.1515.
4.3.5. (E/Z)-(5-Methoxypent-3-en-1-yne-1,5-diyl)dibenzene (19)
1H NMR (250 MHz, CDCl3) d 3.37 (s, 3H, E-isomer), 3.44 (s, 2.1H,
Z-isomer), 7.73 (dd, J = 1.1, 6.5 Hz, 1H, E-isomer), 5.48 (d, J = 8.9 Hz,
0.7H, Z-isomer), 5.88–6.11 (m, 1H E-isomer, 1.4H Z-isomer), 6.29
(dd, J = 6.5 15.8 Hz, 1H, E-isomer), 7.29–7.52 (m, 10H E-isomer,
7H Z-isomer); 13C NMR (E-isomer, 62.9 MHz, CDCl3) d 56.7, 83.7,
87.5, 90.6, 111.2, 123.3, 127.1, 128.1, 128.4, 128.6, 128.7, 131.7,
141.0, 143.3. MS (70 eV) m/z (%): 248 (32) [M+], 233 (100), 215
(66), 202 (38). HRMS Calc. for C18H16O: 248.1201. Found:
248.1203.
4.3.11. (E)-(5-Methoxy-4-methylpent-3-en-1-ynyl)benzene (31)
1H NMR (250 MHz, CDCl3) d 1.97 (s, 3H), 3.34 (s, 3H), 3.94 (d,
J = 0.5 Hz, 2H), 5.75 (d, J = 1.3 Hz, 1H), 7.29–7.34 (m, 3H), 7.43–
7.46 (m, 2H); 13C NMR (90.6 MHz, CDCl3) d 16.9, 58.2, 76.5, 86.8,
93.4, 106.5, 123.9, 128.1, 128.4, 131.5, 147.9. MS (70 eV) m/z (%):
186 (32) [M+], 171 (100), 128 (52), 115 (38). HRMS Calc. for
C13H14O: 186.1045. Found: 186.1044.
4.3.12. (E)-(5-Isopropoxy-4-methylpent-3-en-1-ynyl)benzene (33)
1H NMR (250 MHz, CDCl3) d 1.18 (d, J = 6.0 Hz, 6H), 1.97 (s, 3H),
3.56–3.66 (m, 1H), 3.98 (d, J = 0.8 Hz, 2H), 5.78 (d, J = 1.3 Hz, 1H),
7.29–7.32 (m, 3H), 7.42–7.46 (m, 2H); 13C NMR (90.6 MHz, CDCl3)
d 17.0, 22.2, 71.2, 71.9, 87.1, 93.2, 105.8. 124.0, 128.0, 128.4, 131.5,
148.8. MS (70 eV) m/z (%): 214 (32) [M+], 199 (15), 172 (38), 157
(58), 128 (100). HRMS Calc. for C15H18O: 214.1358. Found:
214.1359.
4.3.6. (E/Z)-(5-Isopropoxypent-3-en-1-yne-1,5-diyl)dibenzene (20)
1H NMR (250 MHz, CDCl3) d 1.17 (d, J = 6.2 Hz, 3 H, E-isomer),
1.22–1.28 (m, 3H E-isomer, 4.8H Z-isomer), 3.66–3.85 (m, 1H E-
isomer, 0.8H Z-isomer), 4.97 (dd, J = 1.3, 6.3 Hz, 1H, E-isomer),
5.64 (d, J = 9.0 Hz, 0.8H, Z-isomer), 5.82–6.10 (m, 1H E-isomer,
1.6H Z-isomer), 6.31 (dd, J = 6.3, 16.0 Hz, 1H, E-isomer), 7.28–
7.50 (m, 10H E-isomer, 8H Z-isomer); 13C NMR (E-isomer,
62.9 MHz, CDCl3) d 22.3, 22.6, 69.3, 79.0, 85.9, 87.7, 95.7, 110.5,
123.4, 126.5, 127.9, 128.3, 128.6, 131.6, 141.2, 144.5. MS (70 eV)
m/z (%): 276 (18) [M+], 233 (100), 215 (57), 205 (45). HRMS Calc.
for C20H20O: 276.1514. Found: 276.1510.
4.3.13. (Z/E)-1-(5-Methoxy-3-methylpent-3-en-1-ynyl)benzene (34)
1H NMR (CDCl3, 360 MHz) d 1.93 (s, 0.2H E-isomer), 1.99 (s,
1H Z-isomer), 3.37 (s, 3H Z-isomer, 0.6H E-isomer), 4.06 (d,
J = 6.6 Hz, 0.8H E-isomer), 4.21 (d, J = 6.8 Hz, 2H Z-isomer),
5.84–5.88 (m, 1H Z-isomer), 6.02–6.09 (m, 0.2H E-isomer),
7.31–7.33 (m, 3H Z-isomer, 0.6H E-isomer), 7.43–7.46 (m, 2H Z-
isomer, 0.4H E-isomer); 13C NMR (Z-isomer, CDCl3, 90 MHz) d
23.3, 58.2, 71.0, 87.8, 94.3, 121.9, 128.4, 128.4, 128.5, 131.6,
133.5; MS (70 eV) m/z (%): 186 (3) [M+], 171 (20), 158 (20),
142 (100), 128 (67), 115 (30).
4.3.7. (E)-2-Isopropoxy-5-methylundec-3-en-5-yne (22)
1H NMR (360 MHz, CDCl3) d 0.90 (t, J = 7.2 Hz, 3H), 1.10 (d,
J = 6.1 Hz, 3H), 1.13 (t, J = 6.1 Hz, 3H), 1.21 (d, J = 6.6 Hz, 3H),
1.28ꢀ1.42 (m, 4H), 1.48ꢀ1.56 (m, 2H), 2.29 (td, J = 7.2 Hz,
J = 2.0 Hz, 2H), 3.62 (sep, J = 6.1 Hz, 1H), 3.91ꢀ4.00 (m, 1H), 5.61
(dd, J = 15.9 Hz, J = 1.1 Hz, 1H), 5.94 (dd, J = 15.9 Hz, J = 7.0 Hz,
1H); 13C NMR (90.6 MHz, CDCl3) d 14.0, 19.5, 21.7, 22.0, 22.3,
23.3, 28.5, 31.2, 68.7, 72.9, 78.5, 91.0, 110.5, 144.6; MS (70 eV)
m/z (%): 208 (5), 151 (14), 109 (100), 95 (26), 81 (27). HRMS Calc.
for C14H24O: 208.1827. Found: 208.1828.
4.3.14. (Z/E)-1-(5-Isopropoxy-3-methylpent-3-en-1-ynyl)benzene
(35)
1H NMR (CDCl3, 360 MHz) d 1.19 (d, J = 6.1 Hz, 6H Z-isomer, 2H
E-isomer), 1.92 (m, 0.6H E-isomer), 1.97 (d, J = 1.1 Hz, 3H Z-iso-
mer), 3.65–3.69 (m, 1H Z-isomer, 0.2H E-isomer), 4.09 (dd,
J = 0.6 Hz, J = 6.8 Hz, 0.4H E-isomer), 4.25 (dd, J = 1.1 Hz,
J = 6.8 Hz, 2H Z-isomer), 5.85–5.89 (m, 1H Z-isomer), 6.00–6.10
(m, 0.2H, E-isomer), 7.28–7.34 (m, 3H Z-isomer, 0.6H E-isomer),
7.41–7.45 (m, 2H Z-isomer, 0.4H E-isomer); 13C NMR (Z-isomer,
CDCl3, 90 MHz) d 22.3, 23.3, 66.6, 70.9, 87.9, 94.1, 121.1, 123.5,
128.4, 128.5, 131.6, 134.5; MS (70 eV) m/z (%): 213 (1), 207 (10),
187 (30), 145 (100), 129 (28), 115 (15).
4.3.8. (E/Z)-(1-isopropoxypent-2-en-4-ynyl)benzene (26)
1H NMR (360 MHz, CDCl3) d 1.14 (d, J = 6.1 Hz, 3H E-isomer),
1.19–1.22 (m, 3H E-isomer, 1.8H Z-isomer), 1.23 (d, J = 6.1 Hz 3H
Z-isomer), 2.87 (d, J = 2.3 Hz, 1H E-isomer), 3.19 (dd, J = 2.3, 0.9,
0.6H Z-isomer), 3.60–3.69 (m, 1H E-isomer), 3.70–3.79 (m, 0.6H
Z-isomer), 4.91 (dd, J = 6.0, 1.2, 1H, E-isomer), 5.53–5.56 (m, 1H,
E-isomer), 5.58–5.62 (m, 0.6H, Z-isomer), 5.69–5.75 (m, 1H, E-iso-
mer), 6.05–6.11 (m, 0.6H, Z-isomer), 6.31 (dd, J = 15.9, 6.0, 1H, E-
isomer), 7.24–7.44 (m, 5H E-isomer, 3H Z-isomer); 13C NMR
(90.6 MHz, CDCl3) d 22.2, 22.6, 69.4, 78.1, 78.7, 82.7, 109.2, 126.5,
127.1, 127.9, 128.7, 140.8, 146.3; MS (70 eV) m/z (%): 200 (5)
[M+], 185 (5), 157 (57), 141 (76), 129 (83), 115 (100), 105 (54),
91 (30), 77 (32), 63 (14), 51 (19).
4.3.15. (E)-4-Methyl-N-(2-methyl-5-phenylpent-2-en-4-
ynyl)benzenesulfonamide (36)
1H NMR (360 MHz, CDCl3) d 1.90 (s, 3H), 2.43 (s, 3H), 3.62 (d,
J = 6.4 Hz, 2H), 4.45 (s, br, 1H), 5.63–5.64 (m, 1H), 7.28–7.34 (m,
5H), 7.38–7.44 (m, 2H), 7.75–7.77 (m, 2H); 13C NMR (90.6 MHz,
CDCl3) d 17.6, 21.7, 49.7, 86.2, 94.1, 108.1, 123.5, 127.3, 128.3,
128.5, 129.9, 131.5, 137.1, 143.8, 145.6; MS (70 eV): m/z (%):348
(100) [M++Na], 333 (29), 305 (9), 193 (10), 139 (25). HRMS Calc.
for C19H19N (M+ꢀ64): 261.1518. Found: 261.1517.
4.3.9. (E)-1-(5-Methoxy-5-methylhex-3-en-1-ynyl)benzene (28)
1H NMR (360 MHz, CDCl3) d 1.32 (s, 6H), 3.21 (s, 3H), 5.84 (d,
J = 16.4 Hz, 1H), 6.21 (d, J = 16.4 Hz, 1H), 7.28ꢀ7.33 (m, 3H),
7.41ꢀ7.47 (m, 2H); 13C NMR (90.6 MHz, CDCl3) d = 25.7, 50.8,
75.2, 87.6, 90.1, 109.6, 123.5, 128.3, 128.4, 131.6, 148.7; MS
(70 eV) m/z (%): 200 (25) [M+], 185 (100), 170 (23), 152 (38), 141
(14). HRMS Calc. for C14H16O: 200.1201. Found: 200.1201.
4.3.16. (Z)-2-(3-Methyl-5-phenylpent-2-en-4-ynyl)furan (37)
1H NMR (CDCl3, 360 MHz) d1.96–2.00 (m, 3H Z-isomer, 1H E-iso-
mer), 3.49 (d, J = 7.3 Hz, 0.6H E-isomer), 3.69 (d, J = 7.3 Hz, 2H Z-
isomer), 5.87 (qt, J = 1.6 Hz, 7.3 Hz, 1H Z-isomer), 6.04–6.05 (m,
1H Z-isomer), 6.08–6.13 (m, 0.3H E-isomer), 6.30 (dd, J = 2.0 Hz,
3.2 Hz, 1H, Z-isomer), 7.29–7.35 (m, 2H Z-isomer, 0.6H E-isomer),
7.42–7.47 (m, 3H, Z-isomer, 1H E-isomer); 13C NMR (Z-isomer,
CDCl3, 90.6 MHz) d 23.2, 29.9, 88.3, 93.8, 105.4, 110.4, 120.3,
123.6, 128.3, 128.4, 131.7, 132.5, 141.3, 154.1; MS (70 eV) m/z
(%): 222 (30) [M+], 207 (100) [M+ꢀCH3], 178 (100).
4.3.10. (E)-1-(5-Isopropoxy-5-methylhex-3-en-1-ynyl)benzene (29)
1H NMR (360 MHz, CDCl3) d 1.14 (d, J = 6.2 Hz, 6H), 1.32 (s, 6H),
3.70 (sep, J = 6.2 Hz, 1H), 5.82 (d, J = 16.4 Hz, 1H), 6.28 (d,
J = 16.4 Hz, 1H), 7.28ꢀ7.35 (m, 3H), 7.41ꢀ7.46 (m, 2H); 13C NMR
(90.6 MHz, CDCl3) d 25.2, 26.9, 65.3, 75.3, 87.8, 89.9, 108.9, 123.5,

514
T.T. Haug et al. / Journal of Organometallic Chemistry 694 (2009) 510–514
(c) C. Nieto-Oberhuber, M.P. Muñoz, E. Buñuel, C. Nevado, D.J. Cárdenas, A.M.
Acknowledgements
Echavarren, Angew. Chem., Int. Ed. 43 (2004) 2402;
(d) C. Nieto-Oberhuber, S. López, M.P. Muñoz, E. Jiménez-Núnez, E. Buñuel, D.J.
Cárdenas, A.M. Echavarren, Chem. Eur. J. 12 (2006) 1694.
[5] B. Crone, S.F. Kirsch, Chem. Eur. J. 14 (2008) 3514.
[6] (a) For further examples involving 3-hydroxy-1,n-enynes, see: C. Lim, J.-E.
Kang, J.-E. Lee, S. Shin, Org. Lett. 9 (2007) 3539;
This project was supported by the Fonds der Chemischen
Industrie (FCI) and the Deutsche Forschungsgemeinschaft (DFG).
We thank Prof. Dr. Th. Bach and his group for helpful discussions
and generous support.
(b) A.K. Buzas, F.M. Istrate, F. Gagosz, Angew. Chem., Int. Ed. 46 (2007) 1141;
(c) S. Wang, L. Zhang, J. Am. Chem. Soc. 128 (2006) 14274;
(d) H.J. Bae, B. Baskar, S.E. An, J.Y. Cheong, D.T. Thangadurai, I.-C. Hwang, Y.H.
Rhee, Angew. Chem., Int. Ed. 47 (2008) 2263.
Appendix A. Supplementary material
[7] S.F. Kirsch, J.T. Binder, B. Crone, A. Duschek, T.T. Haug, C. Liébert, H. Menz,
Angew. Chem., Int. Ed. 46 (2007) 2310.
[8] B. Baskar, H.J. Bae, S.E. An, J.Y. Cheong, Y.H. Rhee, A. Duschek, S.F. Kirsch, Org.
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(c) For related Friedel-Crafts reactions catalyzed by gold complexes, see: Z.
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[10] M. Georgy, V. Boucard, J.-M. Campagne, J. Am. Chem. Soc. 127 (2005) 14180.
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Supplementary material associated with this article can be
found, in the online version, at doi:10.1016/j.jorganchem.2008.09.
062.
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