Synthesis and Heck Reactions of Ethenyl- and (Z)-Butadien-1-yl Nonaflate
FULL PAPER
Synthesis of 1-Trimethylsiloxy-1,2-propadiene (10): A 2.43 solu-
tion of n-butyllithium in hexane (47.0 mL, 114 mmol) was slowly
added to a solution of 2,2-dimethyl-4-methylene-[1,3]dioxolane CMe
15.3 Hz, 1 H, 5-H), 7.34 (dd, J ϭ 11.2, 15.3 Hz, 1 H, 3-H). Ϫ 13C
NMR (67.5 MHz): δ ϭ 23.6, 25.6, 28.0 (3 t, CH ), 27.1, 32.1 (q, s,
), 44.0 (d, CH), 51.3 (q, OMe), 119.0, 122. 9, 135.6, 144.0,
2
3
(6.85 g, 60.0 mmol) in THF (50 mL) at Ϫ78 °C. The reaction mix-
24 2
145.7 (5 d, CH), 135.7 (s, C-1Ј), 167.7 (s, C-1). Ϫ C16H O (248.4):
ture was gradually warmed to Ϫ23 °C and stirred at this temper-
ature for 2 h. Diglyme (20 mL) was then added and the volatile
components were evaporated in vacuo (0.04Ϫ0.05 mbar) keeping
the flask in a cooling bath. At the end of the evaporation, the
cooling bath temperature rose to 0 °C. It was then recooled to Ϫ30
calcd. C 77.38, H 9.74; found C 77.26, H 9.68.
Synthesis of (E)-1-phenyl-1,3-butadiene (14): A mixture of KOAc
(
(
(
2 3 2
0.17 g, 1.7 mmol), K CO (0.30 g, 2.2 mmol) and Pd(OAc)
20 mg, 0.09 mmol) was added to a mixture of ethenyl nonaflate
1b) (0.82 g, 2.50 mmol) and DMF (5 mL). Styrene (0.27 g,
°
C and trimethylchlorosilane (14.9 g, 137 mmol) was added with
2
.60 mmol) was then added, and the resulting suspension was
vigorous stirring. The reaction mixture was allowed to warm to
ambient temperature for 2 h, stirred for further 15 h and then evap-
orated in vacuo (3 Ǟ 2 mbar) into a Ϫ78 °C cold trap. After warm-
ing to ambient temperature, the contents of the trap were subjected
to fractional distillation to give trimethylsiloxyallene 10 (3.65 g,
stirred at 70 °C (7 h). After cooling to ambient temperature, it was
subjected to aqueous workup (ethyl acetate/water). The aqueous
phase was then extracted with ethyl acetate, and the combined or-
2 4
ganic phase was washed with brine (20 mL) and dried (Na SO ).
8% yield) as a colourless liquid, b.p. 50 °C/104 mbar. 1H NMR
270 MHz): δ ϭ 0.21 (s, 9 H, SiMe ), 5.27 (d, J ϭ 6.0 Hz, 2 H, 3-
H), 6.57 (t, J ϭ 6.0 Hz, 1 H, 1-H); cf. ref.
67.5 MHz): δ ϭ Ϫ0.2 (q, SiMe ), 87.1 (t, C-3), 114.7 (d, C-1),
04.8 (s, C-2).
Filtration, removal of volatiles in vacuo followed by CC (hexane/
EtOAc 20:1) of the residue gave a colourless oil, which was further
exposed to vacuum to remove residual styrene, resulting in product
4
(
3
[21]
13
Ϫ
C NMR
1
4 (81 mg, 25% yield). The spectroscopic data of the product 14
(
3
[35]
were consistent with those described in the literature.
2
Synthesis of (3E,5E)-octa-3,5,7-trien-2-one (15): LiCl (1.29 g,
Attempts to Prepare 1,2-Propadienyl nonaflate (3): An interaction
of NfF with lithioxyallene 8 (Ϫ78 °C Ǟ 20 °C, overnight) using
both direct and reverse order of component mixing (slow addition
of NfF to the THF solution of 8 and 9 and vice versa) led to the
complete consumption of the starting materials but only a complex
mixture of decomposition products was observed by NMR spectro-
scopy. The same is true of attempts to prepare the nonaflate 3 from
trimethylsiloxyallene 10 as described above for the synthesis of non-
aflate 2 from the enol ether 7.
3
2
0.5 mmol), Et
1.0 mmol) and Pd(OAc)
3
N (2.91 g, 28.8 mmol), methyl vinyl ketone (1.47 g,
(0.10 g, 0.45 mmol) were added to an
2
emulsion of (Z)-buta-1,3-dien-1-yl nonaflate (2; 3.70 g, 10.5 mmol)
in DMF (11 mL). The reaction flask was then flushed with argon
for 2Ϫ3 min, closed tightly, and the reaction mixture was vigor-
ously stirred at ambient temperature for 15 h (complete conversion
of the starting nonaflate). After aqueous workup (hexane/satd. aq.
NH
hexane, the combined organic phase was washed with brine and
dried (Na SO ). After filtration and evaporation of the volatile
4
Cl ϩ ice), and triple extraction of the aqueous phase with
Synthesis of Methyl (E)-penta-2,4-dienoate (11): LiCl (0.50 g,
2
4
1
1
1.7 mmol), Et
5.6 mmol) and Pd(OAc)
3
N (1.58 g, 15.6 mmol), methyl acrylate (1.35 g,
(88 mg, 0.39 mmol) were added to a so-
components in vacuum, the crude product was purified by kugel-
rohr distillation at 65Ϫ70 °C (0.04 mbar) to give (3E,5E)-octa-
2
lution of ethenyl nonaflate (1b) (2.55 g, 7.80 mmol) in DMF
5.8 mL). The reaction flask was closed tightly, and the reaction
3
,5,7-trien-2-one (15) [0.92 g, 72% yield, (5E):(5Z) ratio ca. 14:1] as
(
[36]
[37]
a yellowish liquid which crystallises in the freezer at Ϫ18 °C.
mixture was vigorously stirred at ambient temperature (24 h). After
1
The crystalline material melts below room temperature. H NMR
500 MHz): δ ϭ 2.29 (s, 3 H, Me), 5.35 (d, J ϭ 10.0 Hz, 1 H, 8-
1
consumption of the starting nonaflate ( H NMR control) the mix-
(
ture was subjected to aqueous workup (40 mL pentane/25 mL satd.
H), 5.45 (d, J ϭ 16.8 Hz, 1 H, 8-H), 6.17 (d, J ϭ 15.5 Hz, 1 H, 3-
H), 6.35 (dd, J ϭ 11.1, 15.0 Hz, 1 H, 5-H), 6.45 (ddd, J ϭ 10.0,
aq. NH
with pentane (3 ϫ 10 mL) and the combined organic phase was
washed with brine (20 mL) and dried (MgSO ). After filtration, the
4 2 4
H PO ϩ 25 g ice). The water phase was then extracted
1
7
0.8, 16.8 Hz, 1 H, 7-H), 6.61 (dd, J ϭ 10.8, 15.0 Hz, 1 H, 6-H),
.16 (dd, J ϭ 11.1, 15.5 Hz, 1 H, 4-H); the coupling constants
4
volatile components were removed in vacuo (up to 30 mbar) and
the product was recondensed at 0.05 mbar in a Ϫ78 °C cold trap.
The spectroscopic data of 11 (0.54 g, 62% yield) were consistent
with those described in the literature.[
indicate an (E)-configuration of the C-3,C-4 and C-5,C-6 double
bonds. Ϫ C NMR (125 MHz): δ ϭ 27.3 (q, Me), 122.0 (t, C-8),
13
1
30.6, 130.8, 136.1, 141.7, 142.9 (5 d, CH), 198.4 (s, C-2).
34]
Evidence for the initial formation of the expected (3E,5Z)-15 (see
Scheme 4) was obtained by an experiment at room temperature
which was interrupted after 3 h [84% conversion of the starting
nonaflate, (5E):(5Z) ϭ 2.3:1]. Formation of (3E,5Z)-15 is indicated
by a downfield signal at δ ϭ 7.60 (ddd, J ϭ 0.9, 11.7, 15.3 Hz, 1
H, 4-H) with a larger coupling constant (15.3 Hz), which is due to
the (E)-configuration of the C-3,C-4 double bond. As a con-
sequence, the remaining possibility for the second isomer [other
than (3E,5E)-15] is (3E,5Z)-15. The conversion and E/Z ratio were
Synthesis of Methyl (2E,4E)-5-(4-tert-butylcyclohex-1-enyl)penta-
2,4-dienoate (13): Methyl (E)-penta-2,4-dienoate (11) was prepared
in situ (see above) from ethenyl nonaflate (1b) (0.93 g, 2.90 mmol)
and methyl acrylate (0.19 g, 2.20 mmol) in DMF (1.5 mL), in the
3
presence of LiCl (0.11 g, 2.60 mmol), Et N (0.55 g, 5.40 mmol) and
Pd(OAc) (20 mg, 0.09 mmol). Then, 4-tert-butylcyclohex-1-enyl
2
nonaflate (12) (0.78 g, 1.80 mmol) was added, and the resulting
mixture was stirred for 24 h at 85 °C. It was then subjected to
aqueous workup (20 mL hexane/10 mL satd. aq. NaHCO
3
ϩ
1
determined by H NMR spectroscopy on the crude reaction mix-
tures just after aqueous workup.
1
0 mL water). The water phase was extracted with hexane (2 ϫ
0 mL), and the combined organic phase was washed with brine
). Filtration, removal of volatiles in
vacuo, followed by CC (gradient elution: hexane Ǟ hexane/Et
00:1) of the residue gave product 13 (0.27 g, 60% yield) as a yel-
1
(20 mL) and dried (MgSO
4
2
O
Acknowledgments
1
1
lowish crystalline solid, m.p. 71Ϫ75 °C. H NMR (270 MHz): δ ϭ Generous support by the Deutsche Forschungsgemeinschaft and
.88 (s, 9 H, CMe ), 1.10Ϫ1.35, 1.89Ϫ2.40 (2 m, 2 H, 5 H, 3 CH the Alexander von Humboldt Foundation (research fellowship for
CH), 3.74 (s, 3 H, OMe), 5.86 (d, J ϭ 15.3 Hz, 1 H, 2-H), 5.99 (m, I. M. L.) is most gratefully acknowledged. We thank Prof. H. Mo-
0
3
2
,
1
H, 2Ј-H), 6.20 (dd, J ϭ 11.2, 15.3 Hz, 1 H, 4-H), 6.56 (d, J ϭ
retto (Bayer AG, Leverkusen) for generous donations of nona-
Eur. J. Org. Chem. 2001, 4189Ϫ4194
4193