Six-membered silacycle odorants: Synthesis and olfactory characterization of Si analogues of artemone, β-dynascone, and herbac

Article abstract of DOI:10.1002/ejic.201402093

Si-Artemone (4a), Si-β-Dynascone (5a), and Si-Herbac 6a, which are Si analogues of the commercial fragrance ingredients Artemone (1), β-Dynascone (2), and Herbac (3), were synthesized expediently by the insertion of terminal alkynes into silacyclobutane 7a. The sensory characterization results revealed that 4a and 6a had quite similar odor qualities compared with those of 1 and 3, whereas 5a had a totally different odor character relative to that of 2. In terms of the odor threshold values, that of 4a was slightly more substantive than that of its carbon analogue 1, 6a was less potent than its carbon analogue 3, whereas that of 5a was approximately one-sixth that of its carbon analogue 2. The combination of the sila-substitution concept with the insertion reactions of terminal alkynes into silacyclobutane efficiently led to the sila-odorants Si-Artemone, Si-β-Dynascone, and Si-Herbac. Si-Artemone and Si-Herbac have sensory characters similar to those of their unsubstituted analogues, whereas Si-β-Dynascone has an odor quite different to that of its unsubstituted analogue.

Full text of DOI:10.1002/ejic.201402093

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DOI:10.1002/ejic.201402093
Six-Membered Silacycle Odorants: Synthesis and
Olfactory Characterization of Si Analogues of Artemone,
β-Dynascone, and Herbac
Junhui Liu,*[a] Qidong Zhang,[a] Peng Li,[a] Zhan Qu,[a]
Shihao Sun,[a] Yuping Ma,[a] Dongying Su,[a] Yongli Zong,[a] and
Jianxun Zhang*[a]
Keywords: Silanes / Fragrances / Cyclization / Pd catalysis / Silacycles
Si-Artemone (4a), Si-β-Dynascone (5a), and Si-Herbac 6a,
which are Si analogues of the commercial fragrance ingredi-
ents Artemone (1), β-Dynascone (2), and Herbac (3), were
synthesized expediently by the insertion of terminal alkynes
into silacyclobutane 7a. The sensory characterization results
revealed that 4a and 6a had quite similar odor qualities com-
pared with those of 1 and 3, whereas 5a had a totally dif-
ferent odor character relative to that of 2. In terms of the odor
threshold values, that of 4a was slightly more substantive
than that of its carbon analogue 1, 6a was less potent than
its carbon analogue 3, whereas that of 5a was approximately
one-sixth that of its carbon analogue 2.
pounds by sila substitution to give six-membered silacycle
odorants has rarely been explored. Therefore, the objective
of the present study was to synthesize and characterize the
six-membered silacycle odorants 4a, 5a, and 6a, for which
the carbon relatives 1,[10] 2,[1] and 3[11] are fragrance ingredi-
ents produced by Givaudan, Firmenich, and IFF, respec-
tively (Figure 1).
Introduction
The search to correlate the molecular structures and
odors of chemical compounds has captivated chemists since
the birth of synthetic organic chemistry in the middle of the
nineteenth century.[1,2] Despite a great deal of research on
structure–odor relationships, the hunt for new or improved
odorants remains heavily dependent on structural similari-
ties with known odorants rather than on knowledge of the
mechanism of olfaction.[2,3] In this context, sila substitu-
tion,[1] in which a gem-dimethyl-substituted carbon center
is replaced by a silicon atom, represents a promising avenue
for the exploration of structure–odor relationships and the
discovery of new odorants.[2b,4] The pioneering work of
Wannagat,[5] Tacke,[6] and their co-workers demonstrated
that sila substitution in known odorants would change and
ideally optimize their olfactory properties.[7] Evidence has
also accumulated that organosilicon molecules show no
special features in their toxicology profiles compared with
those of their parent carbon compounds.[8]
A gem-dimethyl-substituted six-membered ring motif is
present in numerous carotenoid-derived odorants as well as
many synthetic fragrance ingredients such as Artemone,
Dynascone, Herbac, Aphermate, Romandolide, and Helve-
tolide;[1,9] however, the incorporation of Si into these com-
Figure 1. Six-membered carbocycles and corresponding silacycle
odorants.
[a] Key Laboratory of Tobacco Flavor Basic Research, Zhengzhou
Tobacco Research Institute of CNTC,
Results and Discussion
No. 2, Fengyang Street, High-Tech Zone, 450001 Zhengzhou,
China
Four-membered silacycles are versatile building blocks in
organosilicon chemistry and have many applications in or-
ganic, organometallic, and polymer chemistry.[12] The inser-
tion reaction of alkynes into the Si–C bonds of four-mem-
bered silacycles,[13,14] that is, silacyclobutane and silacyclo-
E-mail: ljhpku@outlook.com
jxzh258@sina.com
http://www.ztri.com.cn/english/lofaf/index.shtml
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201402093.
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butene, is a short and elegant route to six-membered sila- piolates and acetylenic ketones. For propiolates, the alkoxy
cycles.[15]
group greatly influenced the insertion reaction yield. When
Our interest in six-membered silacycle odorants moti- HCϵCCH(OEt)2 and HCϵCOEt were employed, 7a and
vated us to further investigate this insertion reaction. A 7b disappeared, and six-membered silacycles were not de-
variety of transition-metal catalysts, phosphine ligands, and tected.
reaction conditions have been tested. The screening results
As a representative case, the structure of 10b was also
showed that among the nickel, palladium, and platinum confirmed by single-crystal analysis (Figure 2). The result
complexes tested, Pd(PPh3)4 gave the highest yields, clearly showed that the tosyl group was located at the β-
whereas other palladium catalysts only led to the formation position of the quaternary silicon center, which verifies that
of silacyclohexenes in less than 40% yields. No ring expan- the alkyne adopts a position to put the electron-deficient
sion occurred with nickel and platinum catalysts in the pres- group at the β-position to the Si atom during the insertion
ence of phosphine ligands. Under the optimized conditions, process.[13,14] To the best of our knowledge, the single-crys-
a variety of terminal alkynes with electron-deficient groups tal structure of a six-membered silacycle as the insertion
were subjected to the ring expansions of silacyclobutanes product of an unsymmetric alkyne into a four-membered
7a and 7b. These reactions occurred smoothly to afford the silacycle has never been reported.
six-membered silacycles 4 and 8–12 in good to excellent
yields (Scheme 1).
Figure 2. Crystal structure of 10b.
The regioselectivity for terminal alkyne insertion into the
Si–C bond of silacyclobutane could be explained by the
proposed mechanism shown in Scheme 2, which is similar
to those reported previously.[13,14] Firstly, the oxidative in-
Scheme 1. Insertion reaction of terminal alkynes with 7a and 7b.
The generally superior performance of silacyclobutane
7b to that of silacyclobutane 7a implies that the bulky silyl
group facilitates the reductive elimination rather than a β-
H elimination process to afford silacyclohexene products.
With a boiling point of 80 °C, silacyclobutane 7a readily
evaporated and escaped from the heating reaction systems.
With regard to the terminal alkyne, HCϵCSO2Tol (SO2Tol
= tosyl) is much more reactive than diphenylphosphinoyl-
ethyne, the reactivity of which is comparable to that of pro- Scheme 2. Proposed reaction mechanism.
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sertion of the Pd0 species into the Si–C bond of 7 affords grances in EtOH applied to smelling blotters. As can be
the five-membered palladasilacycle 13. Then, the alkyne co- seen from Figure 3, a herbal, agrestic, thujone odor charac-
ordinates to the Pd center and favors the conformation with ter was found for 1, a floral, fruity, green character was
less steric repulsion (14/14Ј), from which the insertion of found for 2, and a herbal, woody character was found for
the CϵC bond occurs to provide the seven-membered pal- 3; the odor character was herbal and cedarwood for 4a,
ladasilacycle 15. Finally, the reductive elimination of the pineapple for 5a, and herbal, minty for 6a. These results
PdII species gives the final six-membered silacycle and re- demonstrated that 4a and 6a had quite similar odor quali-
generates the Pd0 species.
ties compared with those of their carbon analogues 1 and
To further demonstrate the usefulness of this methodol- 3, whereas 5a had a totally different odor character than
ogy for the preparation of Si-based odorants, hept-6-en-1- that of 2. By application of GC olfactometry,[9a] the odor
yn-3-one was obtained from its alcohol precursor[16] and detection threshold values were assigned to be 3.6 ngL–1 air
subjected to the insertion process with 7a and 7b to provide for 1, 37 ngL–1 air for 2, and 0.74 ngL–1 air 3, whereas
the six-membered silacycles 5a and 5b (Scheme 3). Notably, those for 4a, 5a, and 6a were 1.4, 5.9, and 1.9 ngL–1 air,
5a is an Si analogue of β-Dynascone (2), which has a floral respectively. Therefore, 4a was slightly more substantive
fruity, allyl ionone type note. Compound 2 combined with than its carbon analogue 1, compound 6a was less potent
its stronger α isomer has been used as a captive material by than its carbon analogue 3, whereas the odor threshold of
Firmenich.[2b]
6a was approximately one-sixth that of its carbon analogue
2.
Scheme 3. Synthesis of Si analogues of β-Dynascone.
Furthermore, Artemone (1) is also known as dehydroher-
bac and has been employed as an ideal starting material for
the synthesis of some common fragrance ingredients, for
example, Dynascone, Herbac, Aphermate, Romandolide,
and Helvetolide.[1,15] Thus, 4a was considered likewise as
an intermediate for the synthesis of related six-membered
silacycle odorants. An initial attempt was made to synthe-
size Si-β-Dynascone (5a). As depicted in Scheme 4, 4a read-
ily reacted with allyl bromide in the presence of KH and
Et3B to furnish 5a in 80% isolated yield. As the laborious
preparation of a terminal acetylenic ketone is avoided, this
reaction procedure seems more convenient than the above-
mentioned insertion reaction. Moreover, 4a was subjected
to a Pd/C-catalyzed hydrogenation process,[17] and Si-Her-
bac (6a) was easily accessible in 87% yield (Scheme 4).
Compound 6a is an Si analogue of Herbac (3), which pos-
sesses a herbal, woody note and is commercially available
from IFF.[10]
Figure 3. Olfactory properties of 1, 2, 3, 4a, 5a, and 6a.
Conclusions
We have synthesized the six-membered silacycle odorants
4a, 5a, and 6a in high efficiency by insertion reactions of
terminal alkynes with silacyclobutane 7a; their carbon
counterparts 1, 2, and 3 demand much more laborious syn-
thetic procedures. With regard to their sensory character,
4a and 6a had quite similar odor qualities compared with
those of their carbon analogues 1 and 3, whereas 5a had a
totally different odor character relative to that of 2. In
terms of the odor detection threshold values, 4a was slightly
more substantive than its carbon analogue 1, 6a was less
potent than its carbon analogue 3, and that of 6a was ap-
proximately one-sixth that of its carbon analogue 2.
Experimental Section
General: Both silacyclobutanes 7a and 7b were conveniently synthe-
sized by bench-scale[18] and large-scale[19] processes. Artemone (1)
was also synthesized according to a published procedure.[20] Unless
otherwise noted, all other chemicals were commercially available
Scheme 4. Derivatization of Si-Artemone 4a.
The olfactory properties of 1, 2, 3, 4a, 5a, and 6a were
determined by using 10% solutions of the respective fra- and used without further purification. Toluene was heated to reflux
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and distilled from sodium benzophenone ketyl under nitrogen. Col-
umn chromatography was performed with silica gel (100–200 mesh,
J & K Scientific). 1H and 13C NMR spectra were recorded with
CDCl3 as the solvent (1H, 300 or 400 MHz; 13C 75.5 or 100 MHz).
Chemical shifts (ppm) were determined relative to internal CHCl3
(1H, δ = 7.26 ppm), internal CDCl3 (13C, δ = 77.00 ppm), or exter-
nal tetramethylsilane (TMS; 29Si, δ = 0.00 ppm). HRMS was per-
formed with a VG-ZAB-HS instrument. Elemental analysis of all
new compounds was performed with an Elementar Vario EL in-
strument. The sensory properties of all odorants were determined
by six expert perfumers with 10% solutions of the respective com-
pounds in ethanol applied to smelling blotters. The odor thresholds
were determined by GC olfactometry:[9a] different dilutions of the
sample substances were injected into a GC instrument in descend-
ing order until the six panelists evaluating the thresholds in blind
tests failed to detect the odor impression at the correct retention
time. The reported threshold values are the geometrical means of
the different values of all individual panelists, and the standard
deviations for each panelist are below 2.0.
10a: Colorless oil, isolated yield 63% (176 mg). 1H NMR (CDCl3):
δ = 7.72 (d, J = 8.0 Hz, 2 H), 7.32 (d, J = 8.0 Hz, 2 H), 7.07 (s, 1
H), 2.43 (s, 3 H), 2.29–2.26 (t, J = 5.3 Hz, 2 H), 1.78–1.76 (q, 2
H), 0.67–0.64 (m, 2 H), 0.14 (s, 6 H) ppm. 13C NMR (CDCl3): δ
= 155.67, 144.12, 135.88, 135.14, 129.74, 128.29, 27.34, 21.58,
21.18, 10.64, –2.54 ppm. HRMS: calcd. for C14H20O2SSi [M]+
280.0953; found 280.0953. C14H20O2SSi (280.46): calcd. C 59.96,
H 7.19; found C 59.99, H 7.14.
10b: Colorless crystals, isolated yield 71% (287 mg), m.p. 151–
153 °C. 1H NMR (CDCl3): δ = 7.76 (d, J = 8.5 Hz, 2 H), 7.50–
7.44 (m, 4 H), 7.42–7.36 (m, 8 H), 7.33 (d, J = 8.0 Hz, 2 H), 2.45–
2.44 (m, 5 H), 1.94–1.91 (q, 2 H), 1.22–1.19 (m, 2 H) ppm. 13C
NMR (CDCl3): δ = 157.98, 144.38, 135.59, 134.83, 133.68, 131.05,
130.04, 129.86, 128.38, 128.16, 27.49, 21.63, 21.03, 8.74 ppm.
HRMS: calcd. for C24H24O2SSi [M]+ 404.1266; found 404.1269.
C24H24O2SSi (404.60): calcd. C 71.25, H 5.98; found C 71.21, H
5.96.
11a: Colorless oil, isolated yield 65% (212 mg). 1H NMR (CDCl3):
δ = 7.70–7.65 (m, 4 H), 7.54–7.49 (m, 2 H), 7.49–7.45 (m, 4 H),
6.68 (d, J = 30.4 Hz, 1 H), 2.30–2.29 (d, J = 5.6 Hz, 2 H), 1.84–
1.82 (t, J = 5.8 Hz, 2 H), 0.76–0.72 (t, J = 6.4 Hz, 2 H), 0.11 (s, 6
H) ppm. 13C NMR (CDCl3): δ = 151.8 (JC,P = 81.7 Hz), 144.6,
132.0 (d, J = 10.4 Hz), 131.8 (d, J = 8.4 Hz), 130.7, 128.5 (d, J =
11.9 Hz), 29.9 (d, J = 13.9 Hz), 21.6 (d, J = 8.4 Hz), 11.5, –2.2 ppm.
31P NMR (200 MHz, CDCl3): δ = 30.77 ppm. HRMS: calcd. for
C19H23OPSi [M]+ 326.1256; found 326.1257. C19H23OPSi (326.45):
calcd. C 69.91, H 7.10; found C 69.95, H 7.06.
11b: Yellow solid, isolated yield 87% (392 mg). 1H NMR (CDCl3):
δ = 7.73–7.68 (m, 4 H), 7.56–7.52 (m, 2 H), 7.50–7.45 (m, 8 H),
7.43–7.34 (m, 6 H), 7.00 (d, J = 30 Hz, 1 H), 2.50–2.46 (q, 2 H),
2.01–1.96 (q, 2 H), 1.30–1.27 (t, J = 6.4 Hz, 2 H) ppm. 13C NMR
(CDCl3): δ = 155.22 (JC,P = 81.3 Hz), 139.60, 134.84, 132.03,
131.92 (d, J = 4.6 Hz), 131.70 (d, J = 99.4 Hz), 130.52, 129.74,
128.57 (d, J = 11.6 Hz), 128.06, 29.97 (d, J = 13.8 Hz), 21.41 (d, J
= 8.5 Hz), 9.67 ppm. 31P NMR (200 MHz, CDCl3): δ = 31.54 ppm.
HRMS: calcd. for C29H27OPSi [M]+ 450.1569; found 450.1566.
C29H27OPSi (450.59): calcd. C 77.30, H 6.04; found C 77.32, H
6.04.
Typical Procedure for the Insertion Reaction of Terminal Alkynes
with Silacyclobutanes in the Presence of Pd(PPh3)4: A catalytic
amount of Pd(PPh3)4 (12 mg, 0.01 mmol) was added to a solution
of silacyclobutane 7a or 7b (1.0 mmol) and a terminal alkyne
(1.0 mmol) in toluene (5 mL) under nitrogen. The pale yellow mix-
ture was then heated at 50 °C, stirred, and monitored by TLC or
GC. Once 7a, 7b, or the terminal alkyne had disappeared, the reac-
tion mixture was cooled and filtered through a thin pad of silica
gel, and the dark brown mixture was concentrated. The resulting
silacyclohexenes were obtained after flash chromatography (petro-
leum ether/diethyl ether, 10:1).
1
8a: Colorless oil, isolated yield 68% (135 mg). H NMR (CDCl3):
δ = 6.97 (s, 1 H), 4.21–4.16 (q, 2 H), 2.40–2.37 (t, J = 6.0 Hz, 2
H), 1.85–1.79 (m, 2 H), 1.32–1.28 (t, J = 7.0 Hz, 3 H), 0.69–0.66
(t, J = 6.6 Hz, 2 H), 0.11 (s, 6 H) ppm. 13C NMR (CDCl3): δ =
167.20, 148.22, 137.82, 60.63, 29.17, 21.14, 14.23, 11.04, –2.36 ppm.
HRMS: calcd. for C10H18O2Si [M]+ 198.1076; found 198.1075.
C10H18O2Si (198.34): calcd. C 60.56, H 9.15; found C 60.51, H
9.16.
12a: Colorless oil, isolated yield 68% (156 mg). 1H NMR (CDCl3):
δ = 7.72–7.71 (t, J = 4.0 Hz, 2 H), 7.54–7.50 (m, 1 H), 7.44–7.41
(t, J = 7.5 Hz, 2 H), 6.36 (s, 1 H), 2.51–2.49 (m, 2 H), 1.94–1.89 (m,
2 H), 0.78–0.75 (m, 2 H), 0.14 (s, 6 H) ppm. 13C NMR (CDCl3): δ
= 198.84, 155.92, 138.95, 137.35, 131.91, 129.60, 128.07, 29.50,
21.09, 11.36, –2.19 ppm. HRMS: calcd. for C14H18OSi [M]+
230.1127; found 230.1127. C14H18OSi (230.38): calcd. C 72.99, H
7.88; found C 72.95, H 7.92.
1
8b: Colorless oil, isolated yield 79% (254 mg). H NMR (CDCl3):
δ = 7.55–7.53 (m, 4 H), 7.42–7.32 (m, 7 H), 4.24–4.19 (q, 2 H),
2.57–2.54 (t, J = 6.4 Hz, 2 H), 2.00–1.94 (m, 2 H), 1.32–1.29 (t, J
= 6.0 Hz, 3 H), 1.24–1.21 (t, J = 6.6 Hz, 2 H) ppm. 13C NMR
(CDCl3): δ = 166.86, 150.46, 135.02, 134.93, 133.22, 129.65, 127.99,
60.86, 29.30, 20.98, 14.23, 9.11 ppm. HRMS: calcd. for C20H22O2Si
[M]+ 322.1389; found 322.1384. C20H22O2Si (322.48): calcd. C
74.49, H 6.88; found C 74.45, H 6.86.
1
12b: White solid, isolated yield 85% (301 mg). H NMR (CDCl3):
1
9a: Colorless oil, isolated yield 75% (170 mg). H NMR (CDCl3):
δ = 7.79–7.77 (m, 2 H), 7.54–7.51 (m, 5 H), 7.44–7.35 (m, 8 H),
6.70 (s, 1 H), 2.68–2.66 (t, J = 6.0 Hz, 2 H), 2.09–2.04 (m, 2 H),
1.33–1.30 (m, 2 H) ppm. 13C NMR (CDCl3): δ = 198.52, 158.17,
137.04, 135.05, 134.86, 133.90, 132.21, 129.72, 129.71, 128.21,
128.06, 29.75, 20.95, 9.51 ppm. HRMS: calcd. for C24H22OSi
[M]+ 354.1440; found 354.1437. C24H22OSi (354.52): calcd. C
81.31, H 6.25; found C 81.35, H 6.26.
δ = 6.86 (s, 1 H), 2.36–2.32 (q, 2 H), 1.84–1.76 (m, 2 H), 1.49 (s, 9
H), 0.67–0.63 (m, 2 H), 0.11 (s, 6 H) ppm. 13C NMR (CDCl3): δ =
166.57, 149.72, 136.52, 80.22, 29.19, 28.03, 21.19, 11.06, –2.28 ppm.
HRMS: calcd. for C12H22O2Si [M]+ 226.1389; found 226.1387.
C12H22O2Si (226.39): calcd. C 63.66, H 9.80; found C 63.69, H
9.81.
1
1
4a: Colorless oil, isolated yield 65% (109 mg). H NMR (CDCl3):
9b: White solid, isolated yield 88% (308 mg). H NMR (CDCl3): δ
δ = 6.80 (s, 1 H), 2.33–2.31 (t, J = 6.5 Hz, 5 H), 1.80–1.75 (m, 2
H), 0.68–0.66 (m, 2 H), 0.13 (s, 6 H) ppm. 13C NMR (CDCl3):
δ = 200.08, 156.35, 137.97, 27.64, 25.18, 20.85, 11.04, –2.42 ppm.
HRMS: calcd. for C9H16OSi [M]+ 168.0970; found 168.0973.
C9H16OSi (168.31): calcd. C 64.23, H 9.58; found C 64.22, H 9.54.
= 7.56–7.53 (m, 4 H), 7.42–7.23 (m, 6 H), 7.22 (s, 1 H), 2.53–2.50
(t, J = 6.0 Hz, 2 H), 1.99–1.93 (q, 2 H), 1.50 (s, 9 H), 1.23–1.19 (t,
J = 6.0 Hz, 2 H) ppm. 13C NMR (CDCl3): δ = 166.17, 152.02,
135.22, 134.94, 131.82, 129.58, 127.95, 80.55, 29.32, 28.02, 21.02,
9.09 ppm. HRMS: calcd. for C22H26O2Si [M]+ 350.1702; found
350.1703. C22H26O2Si (350.53): calcd. C 75.38, H 7.48; found C
75.34, H 7.52.
1
4b: Colorless oil, isolated yield 80% (234 mg). H NMR (CDCl3):
δ = 7.48–7.46 (m, 4 H), 7.37–7.29 (m, 6 H), 7.05 (s, 1 H), 2.44–2.42
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(q, 2 H), 2.32 (s, 3 H), 1.90–1.85 (m, 2 H), 1.18–1.15 (m, 2 H) ppm.
13C NMR (CDCl3): δ = 199.97, 158.34, 134.85, 134.76, 133.41,
129.72, 128.03, 27.82, 25.44, 20.75, 9.18 ppm. HRMS: calcd. for
C19H20OSi [M]+ 292.1283; found 292.1287. C19H20OSi (292.45):
calcd. C 78.03, H 6.89; found C 78.02, H 6.94.
Acknowledgments
This work was supported by the National Natural Science Founda-
tion of China (21102178).
1
5a: Colorless oil, isolated yield 61% (127 mg). H NMR (CDCl3):
δ = 6.78 (s, 1 H), 5.89–5.79 (m, 1 H), 5.06–4.96 (m, 2 H), 2.82–2.78
(t, J = 5.5 Hz, 2 H), 2.37–2.32 (m, 4 H), 1.82–1.76 (m, 2 H), 0.70–
0.67 (m, 2 H), 0.14 (s, 6 H) ppm. 13C NMR (CDCl3): δ = 201.47,
156.24, 137.58, 136.69, 114.92, 36.22, 28.53, 27.99, 20.96, 11.17,
–2.31 ppm. HRMS: calcd. for C12H20OSi [M]+ 208.1283; found
208.1282. C12H20OSi (208.38): calcd. C 69.17, H 9.67; found C
69.14, H 9.71.
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1
5b: Colorless oil, isolated yield 74% (246 mg). H NMR (CDCl3):
[3]
δ = 7.54–7.37 (m, 10 H), 7.12 (s, 1 H), 5.90–5.80 (m, 1 H), 5.08–
4.97 (m, 2 H), 2.90–2.87 (t, J = 5.5 Hz, 2 H), 2.54–2.51 (m, 2 H),
2.41–2.36 (m, 2 H), 1.99–1.93 (m, 2 H), 1.27–1.23 (m, 2 H) ppm.
13C NMR (CDCl3): δ = 201.30, 158.26, 137.46, 134.91, 132.09,
129.76, 128.08, 115.13, 36.47, 28.52, 28.14, 20.85, 9.32 ppm.
HRMS: calcd. for C22H24OSi [M]+ 332.1596; found 332.1598.
C22H24OSi (332.52): calcd. C 79.47, H 7.28; found C 79.45, H 7.28.
[4]
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[6]
Si-Herbac (6a): A solution of 4a (1.0 mmol, 169 mg) in dry MeOH
(20 mL) and 10% Pd/C (54 mg, 5 mol-%) were placed in a stainless-
steel autoclave, which was filled with dry nitrogen. The autoclave
was sealed, flushed three times with hydrogen, and pressurized with
H2 to 10 bar. The reaction mixture was stirred at room temperature
for 2 h. The solvent was evaporated, and the crude product was
purified by column chromatography (silica gel; petroleum ether) to
afford 6a as a colorless oil in 87% isolated yield (148 mg). 1H NMR
(CDCl3): δ = 2.46–2.40 (m, 1 H), 2.12 (s, 3 H), 2.07–2.01 (m, 1 H),
l.85–1.83 (d, J = 13.5 Hz, 1 H), 1.47–1.40 (m, 1 H), 1.20–1.12 (m,
1 H), 0.89–0.86 (d, J = 13.5 Hz, 1 H), 0.74–0.71 (d, J = 17.5 Hz, 1
H), 0.60–0.54 (t, J = 13.5 Hz, 1 H), 0.48–0.41 (m, 1 H), 0.07 (s, 3
H), 0.04 (s, 3 H) ppm. 13C NMR (CDCl3): δ = 212.47, 49.50, 31.01,
26.68, 22.91, 16.65, 13.17, –1.97, –4.41 ppm. HRMS: calcd. for
C9H18OSi [M]+ 170.1127; found 170.1129. C9H18OSi (170.33):
calcd. C 63.47, H 10.65; found C 63.45, H 10.69.
[7]
X-ray Crystallographic Studies of 10b: The data collection for 10b
was performed with a Rigaku RAXIS RAPID IP diffractometer
with graphite-monochromated Mo-Kα radiation (λ = 0.71073 Å).
The determination of the crystal class and unit-cell parameters was
performed by the Rapid-AUTO (Rigaku 2000) program package.
CCDC-95262410 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
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1
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Eur. J. Inorg. Chem. 0000, 0–0
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© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

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/KAP1
Date: 16-06-14 18:35:08
Pages: 7
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FULL PAPER
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Received: February 16, 2014
Published Online: ᭿
Eur. J. Inorg. Chem. 0000, 0–0
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© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Job/Unit: I42093
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Date: 16-06-14 18:35:08
Pages: 7
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FULL PAPER
Fragrances
J. Liu,* Q. Zhang, P. Li, Z. Qu, S. Sun,
Y. Ma, D. Su, Y. Zong, J. Zhang* ... 1–7
Six-Membered Silacycle Odorants: Syn-
thesis and Olfactory Characterization of Si
Analogues of Artemone, β-Dynascone, and
Herbac
Keywords: Silanes / Fragrances / Cycliz-
ation / Pd catalysis / Silacycles
The combination of the sila-substitution
concept with the insertion reactions of
terminal alkynes into silacyclobutane ef-
ficiently led to the sila-odorants Si-Arte-
mone, Si-β-Dynascone, and Si-Herbac. Si-
Artemone and Si-Herbac have sensory
characters similar to those of their unsub-
stituted analogues, whereas Si-β-Dynas-
cone has an odor quite different to that of
its unsubstituted analogue.
Eur. J. Inorg. Chem. 0000, 0–0
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© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim