Mendeleev
Communications
Mendeleev Commun., 2012, 22, 62–63
Base-catalyzed O-vinylation of tertiary propargylic
alcohols with acetylene: first examples
Boris A. Trofimov,* Elena Yu. Schmidt, Elena V. Skital’tseva,
Ivan A. Bidusenko, Nadezhda V. Zorina and Al’bina I. Mikhaleva
A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences,
6
64033 Irkutsk, Russian Federation. Fax: +7 3952 419 346; e-mail: boris_trofimov@irioch.irk.ru
DOI: 10.1016/j.mencom.2012.03.002
1
-Ethynylcyclohexanol and 1-ethynylcycloheptanol are O-vinylated with acetylene in KOH/DMSO superbase system (90°C, autoclave,
initial acetylene pressure of 14 atm, 1 h) to afford the corresponding vinyl ethers in 40 and 34% yields, respectively.
It is a common knowledge that tertiary propargylic alcohols in the
presence of bases readily undergo defragmentation to ketones and
acetylene (a classic reverse Favorsky reaction, Scheme 1).
The crude products contained mainly the target vinyl ether 2a
and starting alcohol 1a in various ratios depending on the reac-
tion conditions (Table 1).
1
The same conditions (90°C, 1 h) were proved to be valid for
vinylation of 1-ethynylcycloheptanol 1b, the non-optimized yield
of the expected vinyl ether 2b being 34% (Scheme 2).†
R2
R1
R2
,
base
R1
C
CH
+ HC CH
OH
O
†
1H and 13C NMR spectra were recorded on a Bruker AVANCE 400
Scheme 1
instrument (400.13 and 101.61 MHz respectively) equipped with inverse
gradient 5 mm probe in CDCl with HMDS as internal standard. All
3
No wonder that O-vinylation of such alcohols with acetylene
under basic conditions (another classic Favorsky reaction) was
not so far reported. Theoretically, such a vinylation is not im-
possible provided its rate being significantly greater than that of
the defragmentation.
2D NMR spectra were recorded using a standard gradient Bruker pulse
programs. IR spectra were obtained on a Bruker Vertex 70 spectrometer.
The reaction of 1-ethynylcyclohexanol 1a with acetylene in the KOH/
DMSO suspension. A mixture of alcohol 1a (2.00 g, 16.1 mmol) and
2
KOH·0.5H O (1.05 g, 16.1 mmol) in DMSO (50 ml) was placed into a
2
3
0.25 dm steel rotating autoclave. The latter was fed with acetylene under
In past few decades, the classic O-vinylation of alcohols with
acetylene was principally improved (with respect to its rate) due to
pressure of 14 atm and then decompressed to atmospheric pressure to
remove air. The autoclave was fed with acetylene again (initial pressure
at ambient temperature was 14 atm and heated to 90°C). The pressure
value reached maximum of 23–25 atm at the reaction temperature and
then dropped upon acetylene consumption during the reaction. The reaction
was processed at 90°C within 1 h. The reaction mixture, after cooling
to room temperature, was diluted with cold (5–10°C) water (50 ml),
neutralized with NH4Cl and extracted with diethyl ether (4×20 ml). The
combined organic extract was washed with water (3×15 ml) and dried
3
the application of superbasic catalytic systems like KOH/DMSO.
4
In particular, these catalysts allowed propargyl alcohol itself and
secondary propargyl alcohols to be successfully vinylated, though
5
the initially formed vinyl ethers were further prototropically iso-
merized to vinyloxyallenes and/or vinyloxy-1,3-dienes. Therefore,
one may expect that a superbase catalytic system will accelerate
the vinylation better than the reverse Favorsky reaction. Moreover,
the latter usually does not require too strong base for its implementa-
(
K CO ) overnight. After removal of the solvent, 2.30 g of a crude residue
2 3
6
was obtained, which was distilled in vacuo to collect a fraction (1.15 g),
tion (often, for this even traces of potassium carbonate are enough ).
1
bp 50–70°C (2 Torr) containing ( H NMR) starting alcohol 1a and vinyl
In view of these achievements, we have undertaken systematic
efforts towards O-vinylation of tertiary propargylic alcohols. Here
we report on preparatively meaningful procedure for the synthesis
of vinyl ether of such alcohols using 1-ethynylcyclohexanol 1a
as a standard compound.
ether 2a in 1:5 ratio. The fraction was diluted with Et O (30 ml) and
2
alcohol 1a was extracted with water (6×5 ml). After removal of Et O
2
pure vinyl ether 2a (0.96 g, 40% yield) was obtained.
1
-Ethynyl-1-(vinyloxy)cyclohexane 2a: colourless viscous liquid with smell
21
1
3
of pine needles, n 1.5184. H NMR, d: 6.65 (dd, 1H, H , J 13.7 Hz,
D
x
HxHb
When alcohol 1a was allowed to contact with acetylene in the
KOH/DMSO system (1:KOH molar ratio was 1:1) at 90°C for
3
3
2
J
6.1 Hz), 4.48 (dd, 1H, H , J
13.7 Hz, J
1.0 Hz), 4.11 (dd, 1H,
1.0 Hz), 2.56 (s, 1H, ºCH), 1.91–1.88, 1.70 –1.66,
HxHa
3
b
HbHx
HbHa
2
H , J
6.1 Hz, J
a
HaHx
HaHb
1
3
1
h under pressure, the earlier unknown vinyl ether 2a was formed
1.57–1.55 (m, 10H, CH2). C NMR, d: 146.7 (C-a), 91.7 (C-b), 84.3
(CºCH), 75.1 (C-1) 74.7 (CºCH), 37.4 (2C-2), 25.0 (C-4), 22.4 (2C-3).
†
in 40% isolated yield (Scheme 2).
–1
IR (film, nmax/cm ): 3307, 2934, 2859, 2108, 1752, 1673, 1629, 1448,
180, 1147, 1065, 974, 906. Found (%): C, 80.05; H, 9.47. Calc. for
C H O (%): C, 79.96; H, 9.39.
Initial acetylene pressure at room temperature was 14 atm
which reached its highest value (23–25 atm) and then rapidly
dropped, thus indicating the vinylation progress.
1
10 14
1
-Ethynyl-1-(vinyloxy)cycloheptane 2b was prepared from alcohol 1b
20
1
analogously. Colourless viscous liquid, n 1.4928. H NMR, d: 6.58 (dd,
1H, H , J
JHbHa 1.0 Hz), 4.09 (dd, 1H, H , J
ºCH), 2.02–1.98, 1.84–1.78, 1.65–1.53 (m, 12H, CH2). C NMR, d: 147.1
(C-a), 91.4 (C-b), 82.9 (CºCH), 74.9 (C-1) 74.2 (CºCH), 40.6, 29.2,
27.8, 22.2 (2C-2, 2C-3, 2C-4). IR (film, nmax/cm ): 3308, 2925, 2855,
108, 1700, 1654, 1448, 1380, 1138, 1031, 955, 916, 645, 627. Found (%):
C, 80.48; H, 9.50. Calc. for C H O (%): C, 80.44; H, 9.82.
CH
Hb
D
CH
3
3
3
KOH / DMSO
13.8 Hz, J
6.3 Hz), 4.43 (dd, 1H, H , J
13.7 Hz,
C
O
x
HxHb
HxHa
b
HbHx
C
+
HC CH
2
3
2
6.1 Hz, J
1.0 Hz), 2.45 (s, 1H,
a
HaHx
HaHb
n
n
OH
Ha
13
Hx
a n = 1
b n = 2
–1
1
a,b
2a,b
2
Scheme 2
11
16
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2012 Mendeleev Communications. All rights reserved.
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