Triflimide-Catalysed Rearrangement of N-(1-Trimethylsilyl)allylhydrazones Results in the Formation of Vinylsilanes and Cyclopropanes

Article abstract of DOI:10.1002/ejoc.201501180

A synthesis of terminal vinylsilanes by triflimide-catalysed rearrangement of N-(1-trimethylsilyl)allylhydrazones is reported. This protocol provides a convenient access to versatile olefinic building blocks through a traceless bond construction. Hydrazones derived from aromatic aldehydes give cis-cyclopropanes in an unexpected side-reaction.

Full text of DOI:10.1002/ejoc.201501180

FULL PAPER
DOI: 10.1002/ejoc.201501180
Triflimide-Catalysed Rearrangement of N-(1-Trimethylsilyl)allylhydrazones
Results in the Formation of Vinylsilanes and Cyclopropanes
Sebastian Dittrich[a] and Franz Bracher*[a]
Keywords: Synthetic methods / Olefination / Sigmatropic rearrangement / Silanes / Hydrazones
A synthesis of terminal vinylsilanes by triflimide-catalysed
tile olefinic building blocks through a traceless bond con-
rearrangement of N-(1-trimethylsilyl)allylhydrazones is re- struction. Hydrazones derived from aromatic aldehydes give
ported. This protocol provides a convenient access to versa-
cis-cyclopropanes in an unexpected side-reaction.
struction” protocol by Thomson, and recently our group
extended this approach to the synthesis of geminally disub-
stituted olefins (Figure 1).[4] Thomson[5] and Tantillo[6] have
also described and calculated related rearrangements under
different reaction conditions.
However, this method is not applicable to the synthesis
of terminal monosubstituted olefins (R2 = R3 = H). To
remedy this shortcoming, we planned to substitute one pro-
ton in the newly generated olefinic group with an easily re-
movable, but also stable functional group.
Introduction
The [3,3]-sigmatropic rearrangement is a powerful tool
for the construction of carbon–carbon bonds, and it has
been used many times in organic synthesis.[1] The Stevens
rearrangement of N-allylhydrazones leads to a new carbon–
carbon bond with loss of dinitrogen, but due to the very
high temperatures required (up to 300 °C), this reaction is
limited in its applications.[2] Thomson and coworkers made
significant improvements in 2010 when they introduced two
modifications: the stability of the reaction substrates was
greatly enhanced by using N-Boc-N-allylhydrazones (A;
Boc = tert-butoxycarbonyl); and by using catalytic amounts
(10 mol-%) of the Brønsted acid triflimide (HNTf2) to trig-
ger the rearrangement, the reaction temperature could be
lowered to 125 °C.[3] Numerous olefins with vicinal disub-
stitution (B) were obtained using this “traceless bond con-
Results and Discussion
The required hydrazine building block (i.e., 4) was pre-
pared starting from known 1-(trimethylsilyl)allyl alcohol (1)
[7]
by coupling with easily available tert-butyl 4,5,6,7-tetra-
chloro-1,3-dioxoisoindolin-2-ylcarbamate (2) under Mitsu-
nobu conditions, followed by removal of the tetrachloro-
phthalimide protective group under standard conditions
(Scheme 1).[8] The structure of intermediate 3 was con-
firmed by X-ray crystallography.
Scheme 1. Synthesis of hydrazine 4. a) PPh3, DIAD (diisopropyl
azodicarboxylate), THF, 0 °C to room temp., 16 h, 77%. b) 1,2-
ethylenediamine, THF, 50 °C, 30 min, 97%.
The subsequent condensations of 4 with various alde-
hydes gave the required hydrazones (i.e., 5a–5q) in very
high, up to quantitative, yields. The choice of an appropri-
ate reaction temperature is a crucial factor in triflimide-cat-
alysed [3,3]-sigmatropic rearrangements, and this is heavily
dependent on the structure of the hydrazine building block
used.[9] We first determined the optimum temperature for
model hydrazone 5a (R = cyclohexyl). Surprisingly, the best
results were obtained at relatively low temperature (100 °C
Figure 1. Olefin synthesis through “traceless bond construction”
starting from Boc-protected N-allylhydrazones.
[a] Department für Pharmazie – Zentrum für Pharmaforschung,
Ludwig-Maximilians-Universität München,
Butenandtstr. 5–13, 81377 München, Germany
E-mail: Franz.Bracher@cup.uni-muenchen.de,
http://cup.uni-muenchen.de/dept/ph/pharmachemie/
bracher.php
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201501180.
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Eur. J. Org. Chem. 2015, 8024–8033

Rearrangement of N-(1-Trimethylsilyl)allylhydrazones
for 1 h). At 125 °C (for 1 h), the yield dropped, presumably identifiable products. The outcome of these reactions was
due to decomposition of the product. We went on to investi- obviously strongly dependent on the electronic properties
gate alternative solvents (1,4-dioxane, THF), but we found of the substituents on the phenyl ring. Some analogues
that anhydrous diglyme gave the best results. Varying bearing electron-donating functional groups (3-hydroxy 5f,
amounts of the starting materials were recovered under the 3-methoxy 5k) underwent smooth rearrangement, but the
optimized conditions.
4-hydroxyphenyl compound (i.e., 5e) did not give any vinyl-
Hydrazones 5a–5c derived from aliphatic aldehydes gave silane. For this latter compound, we hypothesize that the
the desired vinylsilanes (i.e., 6a–6c) with yields ranging from hydroxy group in the para position stabilizes the intermedi-
28 to 65%; these products had an E configuration predomi- ate protonated hydrazone cation, and that the resulting
1
nantly (E/Z ratios Ͼ20:1, determined by H NMR spec- mesomeric system does not undergo rearrangement.
troscopy; Scheme 2, Table 1).
In contrast, the meta-hydroxy analogue (i.e., 5f) cannot
show this type of stabilization, so vinylsilane 6f was formed
in an acceptable yield (39%).
With 4-nitro precursor 5n, we did not observe any re-
arrangement. Probably the very strong electron-with-
drawing effect of the nitro group prevents N-protonation of
the hydrazone by triflimide. The typical change in colour
of the solution, indicative of the initial N-protonation, was
not observed in this experiment. Aldehyde hydrazones bear-
ing acid-labile substituents (nitriles 5g and 5h, methoxy
compound 5k, ester 5m, and indole 5o) showed significant
decomposition under the reaction conditions.
Although the aliphatic hydrazones (i.e., 5a–5c) gave E-
configured vinylsilanes containing minor amounts of the Z
isomers, the aromatic rearrangement products were ob-
tained as pure E isomers (see Table 1).
An unexpected side-reaction was observed with hydraz-
ones derived from substituted benzaldehydes. The vinyl-
silane products contained cyclopropanes 7 (Scheme 2) as a
new type of poorly separable by-product (Ͻ10% for prod-
ucts containing electron-rich phenyl rings 6f and 6k, but
significant amounts for electron-poor products). In the re-
arrangements of hydrazones 5g, 5h, and 5l, bearing cyano
and trifluoromethyl groups, the cyclopropanes were formed
as the major products. Careful reinvestigation of the NMR
spectra of aliphatic vinylsilanes 6a–6c confirmed that this
side-reaction is exclusive to the aromatic series.
The relevant peaks of cyclopropanes 7 were clearly sepa-
rated, due to their typical high-field shifts (δ = 2.1 ppm for
benzylic protons, 1.2 to 1.0 and about 0.6 ppm for the
others),[10] from the peaks of the vinylsilanes in the 1H
NMR spectra. Thus, the structures of the cyclopropanes
could be solved unambiguously by NMR spectroscopic
analysis (DEPT, HMQC, and HMBC experiments) of the
product mixtures. The vinylsilane/cyclopropane ratios were
determined by 1H NMR spectroscopy, and ranged from
23:1 (6f/7f) to 1:10 (6h/7h). For the benzylic proton of the
arylcyclopropane products, we always found almost iden-
tical coupling constants, with 3J = 8.6, 8.6, and 6.0 Hz. Typ-
ical values resulting from 3J coupling with the neighbouring
methylene protons in cyclopropanes are about 8.6 and
6.0 Hz.[10a] The second 8.6 Hz coupling constant can be at-
tributed to a coupling with the other methine proton in the
1,2-disubstituted cyclopropane rings, as this is known to be
Scheme 2. Products of the triflimide-catalysed rearrangements of
N-Boc-N-allylhydrazones 5a–5p. For residues R, see Table 1. Reac-
tion conditions: HNTf2 (10 mol-%), diglyme, 100 °C, 1 h. TMS =
trimethylsilyl.
Table 1. Products obtained from rearrangement [using triflimide
(10 mol-%), 100 °C for 1 h] of N-Boc-hydrazones 5a–5p. For gene-
ral structures, see Scheme 2.
Starting material
Product(s) Yield [%] Product ratio[a]
5a
6a
6b
6c
65
28
40
E/Z Ͼ 22:1
E/Z Ͼ 20:1
E/Z Ͼ 22:1
6d/7d = 1:9.3
–
R = cyclohexyl
5b
R = 2-(phenyl)ethyl
5c
R = nonyl
5d
R = phenyl
5e
6d and 7d 13[b]
–
0
R = 4-hydroxyphenyl
5f
6f and 7f
6g and
39
40
6f/7f = 23:1
6g/7g = 1:2.8
6h/7h = 1:10
6i/7i = 1.1:1
6j/7j = 1:1.2
6k/7k = 12:1
6l/7l = 1:5
–
R = 3-hydroxyphenyl
5g
R = 4-cyanophenyl
5h
R = 3-cyanophenyl
5i
R = 4-bromophenyl
5j
R = 3-bromophenyl
5k
R = 3-methoxyphenyl
5l
R = 3-(trifluoromethyl)phenyl
5m
6h and 7h 18
6i and 7i
6j and 7j
36
21
6k and 7k 28
6l and 7l
22
–
(traces)
R =
4-(methoxycarbonyl)phenyl
5n
–
–
–
0
0
0
–
–
–
R = 4-nitrophenyl
5o
R = 3-indolyl
5p
R = ethoxycarbonyl
[a] E/Z ratios of vinylsilanes 6, or ratio vinylsilane 6/cyclopropane
7. [b] Yield diminished due to the volatility of the product.
Some unexpected results were obtained in the rearrange- a typical value for cis stereochemistry. Since we did not ob-
ments of hydrazones 5d–5n, derived from substituted benz- serve the other cyclopropane isomer in any of the spectra,
aldehydes, yields of successful rearrangements ranged from this side-reaction can be described as diastereoselective, giv-
18 to 40%, but hydrazones 5e, 5m, and 5n did not give ing the cis cyclopropanes only.
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S. Dittrich, F. Bracher
FULL PAPER
Another side-reaction was observed with the cinnam- amount of acid, increasing the reaction temperature, and
aldehyde hydrazone (i.e., 5q) (Figure 2). With this substrate, shortening the reaction time. Once again, only the 1,4-diene
the rearrangement did not give the expected 1,5-diene struc- (i.e., 6q; Figure 2) was formed.
ture, but diene 6q, bearing three nonconjugated π systems,
The influence of the reaction conditions on the vinyl-
was obtained in very low yield (10%). In contrast to our silane/cyclopropane ratio was examined, using hydrazone 5i
previous experiments on triflimide-catalysed rearrange- (R = 4-bromophenyl) (Table 2) as a test compound, since
ments of cinnamaldehyde hydrazones, we did not observe this substrate gave an almost 1:1 mixture (36% yield) under
the formation of a pyrazoline with this hydrazone.[4] We the standard conditions (Table 1). A slightly lower yield
speculate that after successful triflimide-catalysed re- (30%) was obtained at a higher reaction temperature
arrangement and cleavage of the N-Boc group, the elimi- (160 °C) with a dramatically shorter reaction time (5 min);
nation of dinitrogen takes place through an allylic diazene no difference in the product ratio was found, but the forma-
rearrangement (ADR) to give the E-configured internal ole- tion of numerous by-products complicated the work-up. In-
fin (Figure 2).[11] The vinylsilane residue was formed as a creasing the amount of triflimide from 10 mol-% to 30 or
Ͼ15:1 E/Z mixture. But we cannot exclude an alternative 100 mol-% led to an increase of the vinylsilane/cyclo-
pathway in which a styrylcyclopropane is formed first, fol- propane ratio in the product mixture, and the products were
lowed by an acid-catalysed retro-ene reaction.[12] A thermal also contaminated with significant amounts of a new by-
retro-ene reaction can be excluded, since this would give a product 8 (Figure 3). Compound 8 obviously arises from
Z-configured internal olefin.[13]
protodesilylation of vinylsilane 6i. In an acid-free control
experiment (diglyme, 100 °C) no rearrangement or cyclo-
propane formation was observed.
Figure 3. Desilylated by-product product 8 (see Table 2) formed
when higher amounts of acid were used for the rearrangement of
hydrazone 5i.
The results shown in Table 2 demonstrate that the out-
come of the rearrangements can be improved by tedious
optimization of the reaction conditions for the individual
substrates.
Figure 2. Rearrangement of cinnamaldehyde hydrazone 5q with
double-bond migration.
Thus, we can conclude that acid is necessary for cyclo-
propane formation, but that higher amounts of acid lower
the yields of this by-product, and changing the reaction
temperature has no significant effect. The substituents on
the phenyl ring and the TMS group that is present in our
compounds, but not in those investigated previously, have a
major influence on the reaction outcome.
Since the reaction conditions [triflimide (10 mol-%),
100 °C, 1 h] that had been optimized with an aliphatic
hydrazone (5a; R = cyclohexyl) gave (partial) decomposi-
tion with acid-labile substrates on the one hand, and forma-
tion of vinylsilane/cyclopropane mixtures on the other, we
tested some variations of the reaction conditions to try to
improve the yield and/or modify the product ratios
(Table 2). We found that the yield of acid-sensitive methoxy
compound 6k could be enhanced from 28 to 51% by short-
ening the reaction time to 10 min. The relative amount of
the cyclopropane by-product (i.e., 7k) was almost un-
changed. Surprisingly, the rearrangement of the cinnamal-
dehyde hydrazone (i.e., 5q) could be significantly improved
(yield rising from 10 to 49%) by slightly increasing the
Thomson and Tantillo calculated that the free-energy
barrier for the rearrangement of aliphatic hydrazones
should be lower than that for aromatic derivatives, and
stated that this may be the result of the decrease in conjuga-
tion during the rearrangement.[9] Our various results for the
aliphatic and aromatic compounds are in accordance with
these calculations. We suppose that for the aromatic deriva-
tives, the hydrazone cation that is initially formed in the
protonation step undergoes a stabilization reaction instead
of the [3,3]sigmatropic rearrangement (Figure 4). The out-
come of the reaction is heavily dependent on the substitu-
ents on the phenyl ring, and this pathway was found to be
most prevalent when cyano and trifluoromethyl substitu-
ents were present in the meta position. The highest relative
amounts of cyclopropanes were found for these examples.
TMS groups are known for their ability to stabilize cations
in the β position by hyperconjugation.[14] For the hypercon-
jugation to take place, the empty orbital has to be parallel
to the TMS group. Probably, this orientation determines the
observed stereoselectivity of the reaction. In the next step,
Table 2. Rearrangement results with different reaction parameters;
differences from standard conditions are underlined.
Starting Temp. Catalyst amount Time Yield Ratio of products
material [°C]
[mol-%]
[min]
[%]
5k
5q
5i
5i
5i
100
125
100
100
160
160
10
30
0
30
10
100
10
10
60
10
5
51
49
0[a]
38
30
28
6k/7k = 16:1
6q, E/Z Ͼ 15:1
–
6i/7i/8 = 3.8:1:0.8
6i/7i = 1:1[b]
6i/7i/8 = 12.7:1:6.3
5i
4
[a] 91% starting material recovered. [b] Numerous side-products
formed.
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Rearrangement of N-(1-Trimethylsilyl)allylhydrazones
were recorded at ambient temperature (298 K), using CDCl3 as sol-
vent. Chemical shifts (δ) are quoted in ppm, and spectra were cal-
ibrated using solvent signals [CHCl3: δ = 7.26 ppm (1H NMR) and
δ = 77.16 ppm (13C NMR)]. Coupling constants (2J, 3J, 4J) are
given with numbers indicating the number of bonds between the
coupling nuclei. Multiplicities are abbreviated as: s = singlet; d =
doublet; t = triplet; q = quartet; m = multiplet; br. s = broad sing-
let; dd = doublet of doublets; dt = doublet of triplets, and so on.
Infrared spectra were recorded with a Perkin–Elmer Paragon 1000
spectrometer using KBr pellets. High-resolution mass spectra
bicyclic cation E is formed. A similar structure was already
calculated by Thomson and Tantillo as a possible interme-
diate in the rearrangement.[9] For the next step, we suggest
the formation of a 1-pyrazoline. It is known that these com-
pounds undergo thermal decomposition to give cycloprop-
anes, the observed reaction products.[15] When higher
amounts of acid were used, less cyclopropane formation
was observed, and we think that this is the result of an
increased cleavage of the N-Boc group. As a result, the sp3-
hybridized nitrogen next to the TMS group can be proton- (HRMS) were recorded with a JEOL GCmate instrument in EI
mode, and with Finnigan MAT95 and MAT90 instruments op-
erating in EI and ESI modes. The crystal structure was recorded
and calculated with an Oxford XCalibur diffractometer by Dr.
Peter Mayer.
ated, and the rearrangement to the vinyl silane takes
place.[9]
N-tert-Butyloxycarbonylamino-N-(2-trimethylsilylprop-2-en-1-yl)-
4,5,6,7-tetrachlorophthalimide (3): DIAD (650 μL, 3.21 mmol) was
added to a solution of PPh3 (900 mg, 3.43 mmol) in THF (12 mL)
at 0 °C. After a white solid had formed, tert-butyl N-(4,5,6,7-tetra-
chloro-1,3-dioxoisoindolin-2-yl) carbamate (2; 1.2 g, 3.0 mmol) and
a solution of 1-(trimethylsilyl)prop-2-en-1-ol (1; 500 mg,
3.83 mmol) in THF (3 mL) were added. The mixture was stirred at
room temperature for 3 h, during which time the colour changed
to dark green. The solvent was then evaporated, and the residue
was purified by flash chromatography (pentane/diethyl ether,
9.5:0.5) to give 3 (1.19 g, 2.32 mmol, 77%) as a white solid. Rf
Figure 4. Proposed mechanism for cis-cyclopropane formation.
1
= 0.50 (pentane/diethyl ether, 9.5:0.5), m.p. 170–171 °C. H NMR
3
(400 MHz, CDCl3, 323 K): δ = 5.98 (ddd, J = 16.7, 9.9 Hz, 1 H,
Conclusions
HC=C), 5.25–4.84 (m, 2 H, C=CH2), 3.47 (s, 1 H, HCSi), 1.37 (s, 9
H, CCH3), 0.16 (s, 9 H, SiCH3) ppm. 13C NMR (100 MHz, CDCl3,
323 K): δ = 160.9 (CC=O), 152.8 (OC=O), 141.0 (CCl), 135.0
(HC=CH2), 130.5 (CCl), 125.9 (CCCl), 114.8 (C=CH2), 82.7
In conclusion, we have developed an extension of Thom-
son’s protocol for the triflimide-catalysed Stevens re-
arrangement of N-Boc-N-allylhydrazones. This method op-
ens a new route to terminal vinylsilanes through a traceless
bond construction approach. The resulting vinylsilanes
should be versatile building blocks for the synthesis of di-
versely substituted olefins. Moreover, we detected two un-
precedented side-reactions, leading to cis-cyclopropanes
(CCH ), 59.9 (HCSi), 28.2 (CCH ), –1.5 (SiCH ) ppm. IR: ν =
˜
3
3
3
2979, 1798, 1749, 1721, 1371, 1247, 1146, 913, 846 cm–1. HRMS
(ESI): calcd. for C14H15Cl4N2O2Si [M – C5H7O2]+ 412.9627; found
412.9624.
To obtain crystals for the crystal structure, the compound was
heated in isohexane to reflux, and chloroform was added dropwise
from benzaldehyde hydrazones, and deconjugated double through the reflux condenser until the sample was dissolved. This
mixture was then cooled, and stored in the fridge for several days,
after which slightly yellow crystals were obtained.
bonds from a cinnamaldehyde hydrazone.
CCDC-1055944 contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge
from The Cambridge Crystallographic Data Centre via http://
www.ccdc.cam.ac.uk/data_request/cif.
Experimental Section
General Information: All chemicals were purchased at high grade,
and were used without further purification. Bis(trifluoromethane)-
sulfonimide (“triflimide”) was purchased as colourless crystals in
1 g quantities. Diglyme was purchased in 100 mL quantities as
99+% extra-dry solvent packaged under nitrogen in a septum-
sealed bottle, and was used as supplied. All reaction flasks were
dried in a WTC Binder drying oven for at least 2 h at 200 °C. Thin-
layer chromatography was carried out on Polygram Sil G/UV254
from Machery-Nagel. Plates were visualized using UV light
(254 nm), phosphomolybdic acid hydrate (10 wt.-% in 99% eth-
anol) spray, and Ehrlich’s reagent. Flash column chromatography
was carried out with pentane and diethyl ether, using Geduran Si
60 (Merck) silica gel. Melting points were determined using a Büchi
B-540 melting-point apparatus. Every substance (or product mix-
ture) was fully characterized by nuclear magnetic resonance spec-
troscopy, including 1H, 13C, DEPT, COSY, HSQC, and HMBC
spectra, recorded with JEOL J NMR-GX 500 (500 MHz), Bruker
BioSpin Avance III HD (400 MHz), and Bruker BioSpin Avance
III HD (500 MHz) instruments. Unless otherwise stated, spectra
tert-Butyl 1-(2-Trimethylsilylprop-2-en-1-yl)hydrazinecarboxylate
(4): Compound 3 (800 mg, 1.56 mmol) was dissolved in THF
(5 mL), and ethylenediamine (150 μL, 135 mg, 2.25 mmol,
1.44 equiv.) was added at 50 °C. The solution was stirred for 30 min
at 50 °C. The mixture was cooled to room temperature, then
isohexane was added, and the mixture was filtered. The filtrate was
collected, and the solvent was removed with a rotary evaporator.
The resulting residue was purified by gradient flash chromatog-
raphy (pentane/diethyl ether, 9.5:0.5 to 8:2) to give 4 (370 mg,
1.51 mmol, 97%) as a pale yellow oil. Rf = 0.15 (pentane/diethyl
1
ether, 9.5:0.5). H NMR (500 MHz, [D6]DMSO): δ = 5.86 (ddd, 3J
= 17.1, 10.5, 6.5 Hz, 1 H, HC=C), 4.91 (d, 3J = 10.5 Hz, 1 H,
3
C=CH2), 4.83 (d, J = 17.2 Hz, 1 H, C=CH2), 4.54 (s, 2 H, NH2),
3.92 (s, 1 H, HCSi), 1.38 (s, 9 H, CCH3), 0.05 (s, 9 H, SiCH3)
ppm. 13C NMR (125 MHz, [D6]DMSO): δ = 157.2 (OC=O), 136.48
(HC=CH2), 110.7 (C=CH2), 78.8 (CCH3), 56.8 (HCSi), 28.1
(CCH ), –1.8 (SiCH ) ppm. IR: ν = 3329, 2977, 1690, 1630, 1367,
˜
3
3
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S. Dittrich, F. Bracher
FULL PAPER
1
1247, 1170, 842 cm–1. HRMS (ESI): calcd. for C11H25N2O2Si [M
colourless oil. Rf = 0.59 (pentane/diethyl ether, 9.5:0.5). H NMR
+ H]+ 245.1685; found 245.1681.
(500 MHz, CDCl3): δ = 8.57 (br. s, 1 H, N=CH), 7.81–7.46 (m, 2
H, CH), 7.47–7.28 (m, 3 H, CH), 5.92 (ddd, 3J = 17.1, 10.5, 6.5 Hz,
1 H, HC=C), 5.00 (ddd, 3J = 10.5, 2J = 1.5, 4J = 1.5 Hz, 1 H,
C=CH2), 4.91 (ddd, 3J = 17.1, 2J = 1.6, 4J = 1.6 Hz, 1 H, C=CH2),
4.22 (ddd, 3J = 6.5, 4J = 1.6, 1.6 Hz, 1 H, HCSi), 1.53 (s, 9 H,
CCH3), 0.15 (s, 9 H, SiCH3) ppm. 13C NMR (125 MHz, CDCl3):
δ = 153.9 (OC=O), 147.8 (N=CH), 135.7 (C), 135.3 (HC=CH2),
129.5 (CH), 128.7 (CH), 127.3 (CH), 112.1 (C=CH2), 81.4 (CCH3),
General Procedure for the Synthesis of the Hydrazones: The re-
quired aldehyde and hydrazine 4 were stirred in anhydrous ethanol
(1.5 mL per mmol aldehyde) at room temperature until TLC
showed that the conversion was complete. The ethanol was evapo-
rated, and the residue was purified by flash chromatography with
a mixture of pentane and diethyl ether as eluent to give the hydraz-
one.
56.5 (HCSi), 28.5 (CCH ), –1.2 (SiCH ) ppm. IR: ν = 2977, 1667,
˜
3
3
tert-Butyl 2-(Cyclohexylmethylene)-1-[3-(trimethylsilyl)prop-1-en-3-
yl]hydrazinecarboxylate (5a): Cyclohexanecarbaldehyde (80 mg,
0.71 mmol) and 4 (220 mg, 0.90 mmol) gave 5a (241 mg,
0.71 mmol, 100%) as a colourless oil. Rf = 0.56 (pentane/diethyl
1414, 1367, 1292, 1278, 1249, 1156, 1139, 972, 898, 867, 843, 749,
690 cm–1. HRMS (ESI): calcd. for C16H23N2O2Si [M + H]+
333.1993; found 333.1995.
1
tert-Butyl 2-(4-Hydroxybenzylidene)-1-[3-(trimethylsilyl)prop-1-en-
3-yl]hydrazinecarboxylate (5e): 4-Hydroxybenzaldehyde (85 mg,
0.70 mmol) and 4 (220 mg, 0.90 mmol) gave 5e (232 mg,
0.67 mmol, 96%) as a white solid. Rf = 0.41 (pentane/diethyl ether,
ether, 9.5:0.5). H NMR (500 MHz, CDCl3): δ = 7.72 (br. s, 1 H,
3
N=CH), 5.83 (ddd, J = 17.1, 10.5, 6.6 Hz, 1 H, HC=C), 4.95 (d,
3J = 10.5 Hz, 1 H, C=CH2), 4.85 (d, J = 17.3 Hz, 1 H, C=CH2),
3
4.11 (d, 3J = 6.7 Hz, 1 H, HCSi), 2.30–2.20 (m, 1 H, CH), 1.88–
1.79 (m, 2 H, CH2), 1.80–1.72 (m, 2 H, CH2), 1.70–1.63 (m, 1 H,
CH2), 1.46 (s, 9 H, CCH3), 1.38–1.14 (m, 5 H, CH2), 0.08 (s, 9 H,
SiCH3) ppm. 13C NMR (125 MHz, CDCl3): δ = 160.9 (N=CH),
154.0 (OC=O), 135.7 (HC=CH2), 111.7 (C=CH2), 80.7 (CCH3),
56.3 (HCSi), 41.8 (CH), 30.3 (CH2), 28.5 (CCH3), 26.2 (CH2), 25.7
1
6:4), m.p. 81–83 °C. H NMR (400 MHz, CDCl3): δ = 8.44 (br. s,
1 H, N=CH), 7.56–7.43 (m, 2 H, CH), 6.86–6.75 (m, 2 H, CH),
5.91 (ddd, 3J = 17.1, 10.5, 6.6 Hz, 1 H, HC=C), 5.69 (s, 1 H, OH),
4.99 (ddd, 3J = 10.5, 2J = 1.5, 4J = 1.5 Hz, 1 H, C=CH2), 4.92
3
2
4
3
(ddd, J = 17.2, J = 1.6, J = 1.6 Hz, 1 H, C=CH2), 4.23 (ddd, J
4
= 6.6, J = 1.6, 1.6 Hz, 1 H, HCSi), 1.52 (s, 9 H, CCH3), 0.13 (s,
(CH ), –1.3 (SiCH ) ppm. IR: ν = 2977, 2929, 2854, 1697, 1630,
˜
2
3
9 H, SiCH3) ppm. 13C NMR (100 MHz, CDCl3): δ = 157.4 (COH),
154.1 (OC=O), 151.1 (N=CH), 135.5 (HC=C), 129.2 (CH), 128.0
(C), 115.8 (CH), 112.1 (C=CH2), 81.5 (CCH3), 56.6 (HCSi), 28.5
1366, 1247, 842 cm–1. HRMS (ESI): calcd. for C18H34N2NaO2Si
[M + Na]+ 361.2287; found 361.2283.
tert-Butyl 2-(3-Phenylprop-1-ylidene)-1-[3-(trimethylsilyl)prop-1-en-
3-yl]hydrazinecarboxylate (5b): Hydrocinnamaldehyde (95% purity;
94 mg, 0.66 mmol) and 4 (240 mg, 0.98 mmol) gave 5b (206 mg,
0.57 mmol, 86%) as a colourless oil. Rf = 0.58 (pentane/diethyl
(CCH ), –1.3 (SiCH ) ppm. IR: ν = 3355, 2977, 1696, 1655, 1608,
˜
3
3
1516, 1368, 1248, 1161, 1147, 903, 840, 755 cm–1. HRMS (ESI):
calcd. for C14H21N2O3Si [M – C4H7]+ 293.1316; found 293.1315.
1
ether, 9.5:0.5). H NMR (500 MHz, CDCl3): δ = 7.88 (br. s, 1 H,
tert-Butyl 2-(3-Hydroxybenzylidene)-1-[3-(trimethylsilyl)prop-1-en-
3-yl]hydrazinecarboxylate (5f): 3-Hydroxybenzaldehyde (85 mg,
0.70 mmol) and 4 (240 mg, 0.98 mmol) gave 5f (229 mg, 0.66 mmol,
N=CH), 7.35–7.24 (m, 2 H, CH), 7.26–7.10 (m, 3 H, CH), 5.79
3
3
(ddd, J = 17.1, 10.5, 6.5 Hz, 1 H, HC=C), 4.94 (ddd, J = 10.5,
2J = 1.5, 4J = 1.5 Hz, 1 H, C=CH2), 4.81 (ddd, 3J = 17.2, 2J = 1.6,
1
94%) as a colourless oil. Rf = 0.52 (pentane/diethyl ether, 6:4). H
4J = 1.6 Hz, 1 H, C=CH2), 4.04 (d, J = 6.5 Hz, 1 H, HCSi), 2.86
3
NMR (400 MHz, CDCl3): δ = 8.46 (br. s, 1 H, N=CH), 7.22 (dd,
3
3
3J = 8.0 Hz, 1 H, CH), 7.18–7.12 (m, 2 H, CH), 6.82 (ddd, 3J =
(t, J = 7.1 Hz, 2 H, CH2), 2.61 (td, J = 7.0, 6.0 Hz, 2 H, CH2),
1.48 (s, 9 H, CCH3), 0.06 (s, 9 H, SiCH3) ppm. 13C NMR
(125 MHz, CDCl3): δ = 154.0 (N=CH), 153.2 (OC=O), 141.3 (C),
135.4 (HC=C), 128.6 (CH), 128.5 (CH), 126.2 (CH), 111.8
(C=CH2), 81.0 (CCH3), 56.2 (HCSi), 35.3 (HCCH2), 33.0 (CCH2),
4
3
7.9, J = 2.5, 1.3 Hz, 1 H, CH), 5.90 (ddd, J = 17.0, 10.5, 6.5 Hz,
3
2
4
1 H, HC=C), 5.44 (s, 1 H, OH), 5.00 (ddd, J = 10.5, J = 1.5, J
= 1.5 Hz, 1 H, C=CH2), 4.90 (ddd, 3J = 17.2, 2J = 1.6, 4J = 1.6 Hz,
3
4
1 H, C=CH2), 4.23 (ddd, J = 6.5, J = 1.6, 1.6 Hz, 1 H, HCSi),
1.53 (s, 9 H, CCH3), 0.14 (s, 9 H, SiCH3) ppm. 13C NMR
(100 MHz, CDCl3): δ = 156.1 (COH), 153.9 (OC=O), 148.0
(N=CH), 137.1 (C), 135.1 (HC=C), 129.9 (CH), 120.4 (CH), 116.9
(CH), 113.4 (CH), 112.2 (C=CH2), 81.7 (CCH3), 56.4 (HCSi), 28.5
28.5 (CCH ), –1.3 (SiCH ) ppm. IR: ν = 2977, 2953, 1696, 1630,
˜
3
3
1366, 1283, 1247, 1168, 1147, 900, 842 cm–1. HRMS (ESI): calcd.
for C16H25N2O2Si [M – C4H7]+ 305.1680; found 305.1680.
tert-Butyl 2-Decylidene-1-[3-(trimethylsilyl)prop-1-en-3-yl]-
hydrazinecarboxylate (5c): Decanal (109 mg, 0.70 mmol) and 4
(240 mg, 0.98 mmol) gave 3c (230 mg, 0.60 mmol, 86 %) as a
colourless oil. Rf = 0.59 (pentane/diethyl ether, 9.5:0.5). H NMR
(500 MHz, CDCl3): δ = 7.84 (br. s, 1 H, N=CH), 5.83 (ddd, J =
(CCH ), –1.2 (SiCH ) ppm. IR: ν = 3381, 2978, 1698, 1664, 1603,
˜
3
3
1579, 1453, 1368, 1249, 1145, 900, 842 cm–1. HRMS (ESI): calcd.
for C18H29N2O3Si [M + H]+ 349.1942; found 349.1944.
1
3
tert-Butyl 2-(4-Cyanobenzylidene)-1-[3-(trimethylsilyl)prop-1-en-3-
yl]hydrazinecarboxylate (5g): 4-Formylbenzonitrile (92 mg,
0.70 mmol) and 4 (220 mg, 0.90 mmol) gave 5g (247 mg,
0.69 mmol, 99%) as a white solid. Rf = 0.62 (pentane/diethyl ether,
3
2
4
17.1, 10.5, 6.6 Hz, 1 H, HC=C), 4.95 (ddd, J = 10.5, J = 1.5, J
= 1.5 Hz, 1 H, C=CH2), 4.84 (ddd, 3J = 17.1, 2J = 1.7, 4J = 1.7 Hz,
1 H, C=CH2), 4.07 (ddd, 3J = 6.6, 1.6 Hz, 1 H, HCSi), 2.27 (td, J
3
= 7.5, 5.5 Hz, 2 H, NCCH2), 1.56–1.40 (m, 11 H, CCH3, CH2),
1.41–1.13 (m, 12 H, CH2), 0.88 (t, J = 6.9 Hz, 3 H, CH3), 0.08 (s,
1
9.5:0.5), m.p. 101–102 °C. H NMR (500 MHz, CDCl3): δ = 8.60
3
(br. s, 1 H, N=CH), 7.77–7.68 (m, 2 H, CH), 7.68–7.56 (m, 2 H,
CH), 5.89 (ddd, 3J = 17.1, 10.5, 6.5 Hz, 1 H, HC=C), 5.02 (ddd,
3J = 10.5, 2J = 1.4, 4J = 1.4 Hz, 1 H, C=CH2), 4.88 (ddd, 3J =
9 H, SiCH3) ppm. 13C NMR (125 MHz, CDCl3): δ = 155.9
(N=CH), 154.0 (OC=O), 135.6 (HC=C), 111.7 (C=CH2), 80.8
(CCH3), 56.4 (HCSi), 33.5 (NCCH2), 32.0 (CH2), 29.7 (CH2), 29.5
(CH2), 29.4 (CH2), 28.5 (CH2), 26.7 (CH2), 22.8 (CH2), 14.3 (CH3),
2
4
3
4
17.2, J = 1.5, J = 1.5 Hz, 1 H, C=CH2), 4.20 (ddd, J = 6.5, J
= 1.6, 1.6 Hz, 1 H, HCSi), 1.54 (s, 9 H, CCH3), 0.15 (s, 9 H, SiCH3)
ppm. 13C NMR (125 MHz, CDCl3): δ = 153.6 (OC=O), 143.3
(N=CH), 140.3 (C), 134.8 (HC=C), 132.5 (CH), 127.4 (CH), 119.0
(CN), 112.4 (C=CH2), 112.3 (CCN), 82.1 (CCH3), 56.6 (HCSi),
–1.3 (SiCH ) ppm. IR: ν = 2955, 2926, 2856, 1697, 1630, 1366,
˜
3
1282, 1247, 1151, 867, 842 cm–1. HRMS (ESI): calcd. for
C17H35N2O2Si [M – C4H7]+ 327.2462; found 327.2462.
tert-Butyl 2-(Benzylidene)-1-[3-(trimethylsilyl)prop-1-en-3-yl]-
hydrazinecarboxylate (5d): Benzaldehyde (84 mg, 0.79 mmol) and
28.4 (CCH ), –1.2 (SiCH ) ppm. IR: ν = 2980, 2223, 1698, 1597,
˜
3 3
1418, 1246, 1148, 1062, 852, 768 cm–1. HRMS (ESI): calcd. for
4 (220 mg, 0.90 mmol) gave 5d (263 mg, 0.79 mmol, 100%) as a C15H20N3O2Si [M – C4H7]+ 302.1319; found 302.1319.
8028
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© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2015, 8024–8033

Rearrangement of N-(1-Trimethylsilyl)allylhydrazones
tert-Butyl 2-(3-Cyanobenzylidene)-1-[3-(trimethylsilyl)prop-1-en-3- SiCH3) ppm. 13C NMR (100 MHz, CDCl3): δ = 159.9 (COCH3),
yl]hydrazinecarboxylate (5h): 3-Formylbenzonitrile (89 mg,
153.8 (OC=O), 147.5 (N=CH), 137.2 (C), 135.4 (HC=C), 129.6
0.68 mmol) and 4 (240 mg, 0.98 mmol) gave 5h (236 mg, (CH), 120.7 (CH), 116.3 (CH), 112.1 (C=CH2), 110.7 (CH), 81.4
0.66 mmol, 97%) as a colourless oil. Rf = 0.48 (pentane/diethyl
ether, 9.5:0.5). H NMR (400 MHz, CDCl3): δ = 8.57 (br. s, 1 H,
(CCH3), 56.7 (HCSi), 55.4 (OCH3), 28.5 (CCH3), –1.2 (SiCH3)
1
ppm. IR: ν = 2954, 1613, 1602, 1585, 1489, 1259, 1247, 1152, 1045,
˜
4
3
N=CH), 7.91 (dd, J = 1.7, 1.7 Hz, 1 H, CH), 7.84 (ddd, J = 7.9,
990, 863, 837 cm–1. HRMS (ESI): calcd. for C19H31N2O3Si [M +
H]+ 363.2104; found 363.2107.
4J = 1.5, 1.5 Hz, 1 H, CH), 7.59 (ddd, J = 7.7, J = 1.4, 1.4 Hz, 1
H, CH), 7.47 (dd, 3J = 7.9 Hz, 1 H, CH), 5.89 (ddd, 3J = 17.0,
10.5, 6.4 Hz, 1 H, HC=C), 5.02 (ddd, 3J = 10.5, 2J = 1.4, 4J =
3
4
tert-Butyl 2-(3-Trifluoromethylbenzylidene)-1-[3-(trimethylsilyl)-
prop-1-en-3-yl]hydrazinecarboxylate (5l): 3-Trifluoromethylbenz-
aldehyde (121 mg, 0.69 mmol) and 4 (200 mg, 0.82 mmol) gave 5l
(270 mg, 0.67 mmol, 97%) as a colourless oil. Rf = 0.36 (pentane/
1.4 Hz, 1 H, C=CH), 4.88 (ddd, 3J = 17.2, J = 1.5, J = 1.5 Hz, 1
2
4
3
4
H, C=CH), 4.19 (ddd, J = 6.6, J = 1.6, 1.6 Hz, 1 H, HCSi), 1.54
(s, 9 H, CCH3), 0.15 (s, 9 H, SiCH3) ppm. 13C NMR (100 MHz,
CDCl3): δ = 153.7 (OC=O), 143.1 (N=CH), 137.3 (C), 134.8
(HC=C), 132.3 (CH), 131.1 (CH), 130.5 (CH), 129.5 (CH), 118.7
(CN), 113.0 (CCN), 112.4 (C=CH2), 82.0 (CCH3), 56.5 (HCSi),
1
diethyl ether, 9.5:0.5). H NMR (400 MHz, CDCl3): δ = 8.66 (br.
3
s, 1 H, N=CH), 7.94 (s, 1 H, CH), 7.79 (d, J = 7.8 Hz, 1 H, CH),
3
3
7.57 (d, J = 7.7 Hz, 1 H, CH), 7.48 (dd, J = 7.7 Hz, 1 H, CH),
5.91 (ddd, 3J = 17.1, 10.5, 6.5 Hz, 1 H, HC=C), 5.02 (ddd, 3J =
28.4 (CCH ), –1.2 (SiCH ) ppm. IR: ν = 2977, 2231, 1702, 1404,
˜
3
3
2
4
3
2
10.5, J = 1.5, J = 1.5 Hz, 1 H, C=CH2), 4.90 (ddd, J = 17.2, J
= 1.5, 4J = 1.5 Hz, 1 H, C=CH2), 4.20 (ddd, 3J = 6.5, 4J = 1.6,
1.6 Hz, 1 H, HCSi), 1.54 (s, 9 H, CCH3), 0.16 (s, 9 H, SiCH3) ppm.
13C NMR (100 MHz, CDCl3): δ = 153.8 (OC=O), 144.7 (N=CH),
136.8 (C), 135.1 (HC=C), 131.2 [q, J(C,F) = 33.5 Hz, CF3], 130.3
(CH), 129.2 (CH), 125.7 (CH), 125.5 [q, J(C,F) = 272.2 Hz, CF3],
1367, 1277, 1248, 1151, 842, 685 cm–1. HRMS (ESI): calcd. for
C15H20N3O2Si [M – C4H7]+ 302.1319; found 302.1319.
tert-Butyl 2-(4-Bromobenzylidene)-1-[3-(trimethylsilyl)prop-1-en-3-
yl]hydrazinecarboxylate (5i): 4-Bromobenzaldehyde (129 mg,
0.70 mmol) and 4 (240 mg, 0.98 mmol) gave 5i (270 mg, 0.66 mmol,
94%) as a colourless oil. Rf = 0.38 (pentane/diethyl ether, 9.5:0.5).
1H NMR (400 MHz, CDCl3): δ = 8.55 (br. s, 1 H, N=CH), 7.50
(m, 4 H, CH), 5.90 (ddd, 3J = 17.1, 10.5, 6.5 Hz, 1 H, HC=C), 5.00
2
1
123.8 (CH), 112.3 (C=CH2), 81.8 (CCH3), 56.8 (HCSi), 28.4
(CCH ), –1.2 (SiCH ) ppm. IR: ν = 2979, 1704, 1406, 1368, 1328,
˜
3
3
1275, 1250, 1166, 1148, 1131, 1070, 866, 842, 800, 697 cm–1. HRMS
(ESI): calcd. for C19H28F3N2O2Si [M + H]+ 401.1872; found
401.1872.
3
2
4
3
(ddd, J = 10.5, J = 1.5, J = 1.5 Hz, 1 H, C=CH2), 4.89 (ddd, J
2
4
3
4
= 17.2, J = 1.5, J = 1.5 Hz, 1 H, C=CH2), 4.19 (dt, J = 6.6, J
= 1.6, 1.6 Hz, 1 H, HCSi), 1.52 (s, 9 H, CCH3), 0.14 (s, 9 H, SiCH3)
ppm. 13C NMR (100 MHz, CDCl3): δ = 153.8 (OC=O), 145.8
(N=CH), 135.2 (HC=C), 134.8 (CBr), 131.9 (CH), 128.6 (CH),
123.5 (C), 112.2 (C=CH2), 81.6 (CCH3), 56.6 (HCSi), 28.4 (CCH3),
tert-Butyl 2-(4-Methoxycarbonylbenzylidene)-1-[3-(trimethylsilyl)-
prop-1-en-3-yl]hydrazinecarboxylate (5m): Methyl 4-formylbenzoate
(115 mg, 0.70 mmol) and 4 (220 mg, 0.90 mmol) gave 5m (268 mg,
0.69 mmol, 99%) as a colourless oil. Rf = 0.27 (pentane/diethyl
–1.2 (SiCH ) ppm. IR: ν = 2978, 1700, 1412, 1367, 1279, 1249,
˜
1
3
ether, 9.5:0.5). H NMR (500 MHz, CDCl3): δ = 8.69 (br. s, 1 H,
1147, 843 cm–1. HRMS (ESI): calcd. for C18H28BrN2O2Si [M +
HC=N), 8.18–7.94 (m, 2 H, CH), 7.81–7.60 (m, 2 H, CH), 5.90
H]+ 411.1098; found 411.1102.
3
3
(ddd, J = 17.0, 10.5, 6.5 Hz, 1 H, HC=C), 5.01 (ddd, J = 10.5,
2J = 1.5, 4J = 1.5 Hz, 1 H, C=CH2), 4.89 (ddd, 3J = 17.2, 2J = 1.5,
tert-Butyl 2-(3-Bromobenzylidene)-1-[3-(trimethylsilyl)prop-1-en-3-
yl]hydrazinecarboxylate (5j): 3-Bromobenzaldehyde (145 mg,
0.78 mmol) and 4 (240 mg, 0.98 mmol) gave 5j (317 mg, 0.77 mmol,
99%) as a colourless oil. Rf = 0.38 (pentane/diethyl ether, 9.5:0.5).
1H NMR (400 MHz, CDCl3): δ = 8.51 (br. s, 1 H, N=CH), 7.81
4J = 1.5 Hz, 1 H, C=CH2), 4.20 (ddd, J = 6.7, J = 1.6, 1.6 Hz, 1
H, HCSi), 3.92 (s, 3 H, OCH3), 1.54 (s, 9 H, CCH3), 0.15 (s, 9 H,
SiCH3) ppm. 13C NMR (125 MHz, CDCl3): δ = 166.9 (CC=O),
153.7 (OC=O), 144.7 (N=CH), 140.1 (C), 134.9 (HC=C), 130.5
(CC=O), 130.0 (CH), 127.0 (CH), 112.3 (C=CH2), 81.8 (CCH3),
3
4
4
3
4
(dd, J = 1.8 Hz, 1 H, CH), 7.54 (ddd, J = 7.8, J = 1.3, 1.3 Hz,
56.5 (HCSi), 52.3 (OCH ), 28.4 (CCH ), –1.2 (SiCH ) ppm. IR: ν
1 H, CH), 7.44 (ddd, 3J = 8.0, 4J = 2.1, 1.1 Hz, 1 H, CH), 7.23
˜
3
3
3
= 2978, 1725, 1702, 1408, 1275, 1249, 1146, 1110, 843, 768 cm–1.
HRMS (ESI): calcd. for C20H31N2O4Si [M + H]+ 391.2048; found
391.2052.
(dd, 3J = 7.9, 7.9 Hz, 1 H, CH), 5.90 (ddd, J = 17.0, 10.5, 6.5 Hz,
3
1 H, HC=C), 5.01 (ddd, 3J = 10.5, 2J = 1.5, 4J = 1.5 Hz, 1 H,
C=CH2), 4.89 (ddd, 3J = 17.2, 2J = 1.5, 4J = 1.5 Hz, 1 H, C=CH2),
4.19 (ddd, 3J = 6.6, 4J = 1.6, 1.5 Hz, 1 H, HCSi), 1.53 (s, 9 H,
CCH3), 0.15 (s, 9 H, SiCH3) ppm. 13C NMR (100 MHz, CDCl3):
δ = 153.8 (OC=O), 144.7 (N=CH), 138.0 (C), 135.0 (HC=C), 132.2
(CH), 130.2 (CH), 129.9 (CH), 125.9 (CH), 122.9 (CBr), 112.3
(C=CH2), 81.8 (CCH3), 56.5 (HCSi), 28.4 (CCH3), –1.2 (SiCH3)
tert-Butyl 2-(4-Nitrobenzylidene)-1-[3-(trimethylsilyl)prop-1-en-3-
yl]hydrazinecarboxylate (5n): 4-Nitrobenzaldehyde (105 mg,
0.69 mmol) and 4 (220 mg, 0.90 mmol) gave 5n (262 mg,
0.69 mmol, 100 %) as a yellow solid. Rf = 0.41 (pentane/diethyl
1
ether, 9.5:0.5), m.p. 105–106 °C. H NMR (400 MHz, CDCl3): δ =
ppm. IR: ν = 2978, 1702, 1403, 1367, 1278, 1249, 1148, 863, 842,
˜
8.65 (br. s, 1 H, N=CH), 8.32–8.15 (m, 2 H, CH), 7.85–7.69 (m, 2
H, CH), 5.90 (ddd, 3J = 17.0, 10.5, 6.4 Hz, 1 H, HC=C), 5.03 (ddd,
3J = 10.5, 2J = 1.4, 4J = 1.4 Hz, 1 H, C=CH2), 4.89 (ddd, 3J =
781, 684 cm–1. HRMS (ESI): calcd. for C18H28BrN2O2Si [M +
H]+ 411.1103; found 411.1103.
2
4
3
4
17.2, J = 1.5, J = 1.5 Hz, 1 H, C=CH2), 4.21 (ddd, J = 6.5, J
= 1.6, 1.6 Hz, 1 H, HCSi), 1.54 (s, 9 H, CCH3), 0.16 (s, 9 H, SiCH3)
ppm. 13C NMR (100 MHz, CDCl3): δ = 153.6 (OC=O), 148.0
(CNO2), 142.6 (N=CH), 142.1 (C), 134.7 (HC=C), 127.5 (CH),
124.1 (CH), 112.5 (C=CH2), 82.3 (CCH3), 56.7 (HCSi), 28.4
tert-Butyl 2-(3-Methoxybenzylidene)-1-[3-(trimethylsilyl)prop-1-en-
3-yl]hydrazinecarboxylate (5k): 3-Methoxybenzaldehyde (95 mg,
0.70 mmol) and 4 (240 mg, 0.98 mmol) gave 5k (251 mg,
0.69 mmol, 99%) as a colourless oil. Rf = 0.48 (pentane/diethyl
1
ether, 9.5:0.5). H NMR (400 MHz, CDCl3): δ = 8.60 (br. s, 1 H,
(CCH ), –1.2 (SiCH ) ppm. IR: ν = 2981, 1699, 1581, 1511, 1418,
˜
3
3
3
4
N=CH), 7.31–7.23 (m, 2 H, CH), 7.17 (dt, J = 7.5, J = 1.1 Hz,
1335, 1246, 1149, 1104, 902, 845, 694 cm–1. HRMS (ESI): calcd.
1 H, CH), 6.90 (ddd, 3J = 8.2, 4J = 2.7, 1.1 Hz, 1 H, CH), 5.91
for C14H20N3O4Si [M – C4H7]+ 322.1218; found 322.1217.
3
3
(ddd, J = 17.1, 10.5, 6.5 Hz, 1 H, HC=C), 5.00 (ddd, J = 10.5,
2J = 1.5, 4J = 1.5 Hz, 1 H, C=CH2), 4.91 (ddd, 3J = 17.1, 4J = 1.5,
tert-Butyl 2-(Indol-3-ylmethylene)-1-[3-(trimethylsilyl)prop-1-en-3-
yl]hydrazinecarboxylate (5o): 3-Formylindole (117 mg, 0.81 mmol)
4J = 1.5 Hz, 1 H, C=CH2), 4.22 (ddd, J = 6.5, J = 1.6, 1.6 Hz, 1
3
4
H, HCSi), 3.82 (s, 3 H, OCH3), 1.53 (s, 9 H, CCH3), 0.16 (s, 9 H, and 4 (220 mg, 0.90 mmol) were stirred in a mixture of ethanol
Eur. J. Org. Chem. 2015, 8024–8033
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
8029

S. Dittrich, F. Bracher
FULL PAPER
(1 mL), chloroform (1 mL), and acetic acid (0.1 mL) to give 5o
the reaction flask by syringe, the flask was put into a preheated oil
bath, and the mixture was stirred at 100 °C. To prevent overpres-
sure, a bubbler was added with a needle through the septum on the
(284 mg, 0.77 mmol, 95%) as a white solid after flash chromatog-
1
raphy. Rf = 0.40 (pentane/diethyl ether, 1:1), m.p. 148–149 °C. H
3
NMR (500 MHz, CDCl3): δ = 8.44 (d, J = 5.2 Hz, 1 H, N=CH), top of the reflux condenser. After 1 h, the flask was removed from
3
8.40 (s, 1 H, NH), 8.36 (br. s, 1 H, N=CH), 7.37 (d, J = 7.4 Hz, the oil bath, and the mixture was cooled down to room tempera-
2 H, CH), 7.26 (ddd, 3J = 8.1, 7.4, 4J = 1.1 Hz, 1 H, CH), 7.21 ture. Saturated aq. NaHCO3 (10 mL) and water (100 mL) were
3
(ddd, 3J = 8.1, 7.4, 4J = 1.1 Hz, 1 H, CH), 5.96 (ddd, J = 17.0,
added. The mixture was extracted with pentane (3ϫ 10 mL). The
combined pentane phases were dried with MgSO4, filtered, and
concentrated in vacuo. Flash chromatography with pentane and
diethyl ether as eluent was used to purify the products. Unless
10.5, 6.6 Hz, 1 H, HC=C), 5.03 (ddd, 3J = 10.5, 2J = 1.5, 4J =
3
2
4
1.5 Hz, 1 H, C=CH2), 4.98 (ddd, J = 17.1, J = 1.6, J = 1.6 Hz,
1 H, C=CH2), 4.18 (d, 3J = 6.1 Hz, 1 H, HCSi), 1.58 (s, 9 H,
CCH3), 0.16 (s, 9 H, SiCH3) ppm. 13C NMR (125 MHz, CDCl3): otherwise stated, the Rf values for the products are around 0.9 in
δ = 154.5 (OC=O), 136.9 (C), 134.8 (N=CH), 127.5 (CH), 125.0 pentane. All product ratios in the resulting mixtures were calculated
1
(C), 123.5 (CH), 123.0 (NCH), 121.3 (CH), 114.2 (C), 112.3
from their H NMR spectra.
(C=CH2), 111.1 (CH), 80.8 (CCH3), 53.8 (HCSi), 28.6 (CCH3),
4-Cyclohexyl-1-(trimethylsilyl)but-1-ene (6a): Prepared from
hydrazone 5a (171 mg, 0.51 mmol) according to the general pro-
cedure with HNTf2 (14 mg) and diglyme (10 mL). Flash
chromatography with pentane gave 6a (70 mg, 0.33 mmol, 65%, E/
Z Ͼ 22:1) as a colourless liquid, a mixture of two olefin isomers.
Starting material 5a (39 mg, 23%) was also recovered. Data for 6a:
–1.0 (SiCH ) ppm. IR: ν = 3264, 2972, 1701, 1534, 1416, 1248,
˜
3
1143, 1131, 1113, 902, 849, 748 cm–1. HRMS (ESI): calcd. for
C20H30N3O2Si [M + H]+ 372.2102; found 372.2103.
tert-Butyl 2-(Ethoxycarbonylmethylene)-1-[3-(trimethylsilyl)prop-1-
en-3-yl]hydrazinecarboxylate (5p): Ethyl glyoxylate (50% in toluene;
0.5 mL, 2.52 mmol) and 4 (200 mg, 0.82 mmol) gave 5p (268 mg,
0.82 mmol, 100%) as a white solid. Rf = 0.38 (pentane/diethyl ether,
3
1H NMR (500 MHz, CDCl3): δ = 6.02 (dt, J = 18.5, 6.2 Hz, 1 H,
3
4
3
C=CH), 5.61 (dt, J = 18.5, J = 1.5 Hz, 1 H, SiCH), 2.10 (dtd, J
4
1
= 7.9, 6.2, J = 1.4 Hz, 2 H, CH2), 1.76–1.60 (m, 5 H), 1.34–1.08
9:1), m.p. 35–37 °C. H NMR (500 MHz, CDCl3): δ = 7.99 (br. s,
(m, 6 H), 0.93–0.78 (m, 2 H), 0.04 (s, 9 H, SiCH3) ppm. 13C NMR
(125 MHz, CDCl3): δ = 147.9 (C=CH), 129.3 (SiCH), 37.5 (CH),
36.6 (CH2), 34.3 (CH2), 33.5 (CH2), 26.9 (CH2), 26.6 (CH2), –1.0
1 H, N=CH), 5.80 (ddd, 3J = 17.1, 10.5, 6.6 Hz, 1 H, HC=C), 5.00
3
2
4
3
(ddd, J = 10.4, J = 1.3, J = 1.3 Hz, 1 H, C=CH2), 4.82 (ddd, J
2
4
3
= 17.2, J = 1.4, J = 1.4 Hz, 1 H, C=CH2), 4.26 (q, J = 7.1 Hz,
2 H, CH2), 4.06 (d, J = 6.3 Hz, 1 H, HCSi), 1.51 (s, 9 H, CCH3),
3
(CH ) ppm. IR: ν = 2923, 2852, 2359, 2342, 1617, 1449, 1247, 990,
˜
3
862, 837 cm–1. HRMS (EI+): calcd. for C13H26Si [M]+ 210.1804;
1.32 (t, 3J = 7.1 Hz, 3 H, CH3), 0.12 (s, 9 H, SiCH3) ppm. 13C
NMR (125 MHz, CDCl3): δ = 164.5 (CC=O), 153.0 (OC=O), 134.4
(HC=C), 133.3 (N=CH), 112.6 (C=CH2), 83.0 (CCH3), 61.1
(OCH2), 58.0 (HCSi), 28.2 (CCH3), 14.3 (CH3), –1.5 (SiCH3) ppm.
found 210.1797.
6-Phenyl-1-(trimethylsilyl)hex-1-ene (6b): Prepared from hydrazone
5b (179 mg, 0.50 mmol) according to the general procedure with
HNTf2 (15 mg) and diglyme (10 mL). Flash chromatography with
pentane gave 5b (32 mg, 0.14 mmol, 28%, E/Z Ͼ 11:1) as a colour-
less liquid, a mixture of two olefin isomers. Starting material 5b
(38 mg, 21%) was also recovered. Data for 6b: 1H NMR (500 MHz,
CDCl3): δ = 7.32–7.23 (m, 2 H, CH), 7.24–7.13 (m, 3 H,CH), 6.01
IR: ν = 2980, 1742, 1715, 1581, 1369, 1239, 1148, 845 cm–1. HRMS
˜
(ESI): calcd. for C15H32N3O4Si [M + NH4]+ 346.2159; found
346.2157.
tert-Butyl 2-(3-Phenylprop-2-en-1-ylidene)-1-[3-(trimethylsilyl)prop-
1-en-3-yl]hydrazinecarboxylate (5q): Cinnamaldehyde (105 mg,
0.79 mmol) and 4 (220 mg, 0.90 mmol) gave 5q (285 mg,
0.79 mmol, 100%) as a yellow oil. Rf = 0.59 (pentane/diethyl ether,
9.5:0.5). 1H NMR (400 MHz, CDCl3): δ = 8.35 (br. s, 1 H, N=CH),
7.50–7.41 (m, 2 H, CH), 7.38–7.31 (m, 2 H, CH), 7.31–7.22 (m, 1
H, CH), 6.95–6.75 (m, 2 H,CH), 5.88 (ddd, 3J = 17.0, 10.5, 6.3 Hz,
1 H, HC=C), 5.00 (ddd, 3J = 10.5, 2J = 1.5, 4J = 1.5 Hz, 1 H,
C=CH2), 4.87 (ddd, 3J = 17.2, 2J = 1.6, 4J = 1.6 Hz, 1 H, C=CH2),
4.13 (ddd, 3J = 6.4, 4J = 1.7, 1.7 Hz, 1 H, HCSi), 1.52 (s, 9 H,
CCH3), 0.13 (s, 9 H, SiCH3) ppm. 13C NMR (100 MHz, CDCl3):
δ = 153.7 (OC=O), 148.8 (N=CH), 137.8 (CH), 136.6 (C), 135.1
(HC=CH2), 128.9 (CH), 128.6 (CH), 127.1 (CH), 127.0 (CH), 112.0
(C=CH2), 81.6 (CCH3), 56.6 (HCSi), 28.4 (CCH3), –1.1 (SiCH3)
3
3
4
(dt, J = 18.5, 6.2 Hz, 1 H,CH), 5.63 (dt, J = 18.5, J = 1.6 Hz, 1
3
3
H, SiCH), 2.62 (t, J = 7.8 Hz, 2 H, CH2), 2.14 (tdd, J = 7.7, 6.2,
4J = 1.5 Hz, 2 H, CH2), 1.60 (tt, J = 7.9, 7.4 Hz, 2 H, CH2), 1.45
3
(tt, 3J = 7.9, 7.4 Hz, 2 H, CH2), 0.04 (s, 9 H, SiCH3) ppm. 13C
NMR (125 MHz, CDCl3): δ = 147.1 (CH2CH), 142.9 (C), 130.0
(SiCH), 128.6 (CH), 128.4 (CH), 125.8 (CH), 36.7 (CH2CH), 36.0
(CCH ), 31.1 (CH ), 28.4 (CH ), –1.0 (SiCH ) ppm. IR: ν = 3027,
˜
2
2
2
3
2954, 2932, 2856, 1616, 1496, 1453, 1247, 998, 863, 837 cm–1
.
HRMS (EI+): calcd. for C15H24Si [M]+ 232.1647; found 232.1647.
1-(Trimethylsilyl)tridec-1-ene (6c): Prepared from hydrazone 5c
(191 mg, 0.50 mmol) according to the general procedure with
HNTf2 (14 mg) and diglyme (10 mL). Flash chromatography with
pentane gave 6c (51 mg, 0.20 mmol, 40%, E/Z Ͼ 22:1) as a colour-
less liquid, a mixture of two olefin isomers. Starting material 5c
(75 mg, 39%) was also recovered. Data for 6c: 1H NMR (500 MHz,
ppm. IR: ν = 2978, 1697, 1414, 1278, 1248, 1156, 1140, 972,
˜
843 cm–1. HRMS (ESI): calcd. for C20H31N2O2Si [M + H]+
359.2155; found 359.2152.
3
3
CDCl3): δ = 6.02 (dt, J = 18.5, 6.2 Hz, 1 H, CH), 5.61 (dt, J =
General Procedure for the Rearrangement: A solution of triflimide
in diglyme was added by syringe to a septum-sealed and nitrogen-
purged two-necked flask equipped with a reflux condenser. This
solution was always freshly prepared as follows: triflimide crystals
were put into a separate flask under nitrogen. The crystals were
dissolved in diglyme, and an aliquot corresponding to 10 mol-%
triflimide was added to the reaction flask. The solution in the reac-
tion flask was then diluted with diglyme until 70% of the maximum
solvent volume was reached. The remaining solvent volume was
used to dissolve the desired hydrazone under nitrogen, and to rinse
the flask properly. The final concentration of the hydrazone in di-
glyme was 0.05 m. After the hydrazone solution had been added to
18.5, 4J = 1.5 Hz, 1 H, SiCH), 2.09 (dt, 3J = 7.7, 6.3 Hz, 2 H, CH2),
3
1.48–1.13 (m, 18 H, CH2), 0.87 (t, J = 6.7 Hz, 3 H, CH3), 0.04 (s,
9 H, SiCH3) ppm. 13C NMR (100 MHz, CDCl3): δ = 147.6
(CH2CH), 129.6 (SiCH), 36.9 (CH2CH), 32.1 (CH2), 29.8 (CH2),
29.8 (CH2), 29.8 (CH2), 29.7 (CH2), 29.5 (CH2), 29.4 (CH2), 28.9
(CH ), 22.9 (CH ), 14.3 (CH ), –1.0 (SiCH ) ppm. IR: ν = 2923,
˜
2
2
3
3
2852, 2359, 2342, 1617, 1449, 1247, 990, 862, 837 cm–1. HRMS
(EI+): calcd. for C16H34Si [M]+ 254.2430; found 254.2439.
4-Phenyl-1-(trimethylsilyl)but-1-ene (6d) and (؎)-cis-1-(Trimethyl-
silyl)methyl-2-phenylcyclopropane (7d): Prepared from hydrazone 5d
(169 mg, 0.51 mmol) according to the general procedure with
8030
www.eurjoc.org
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2015, 8024–8033

Rearrangement of N-(1-Trimethylsilyl)allylhydrazones
HNTf2 (14 mg) and diglyme (10 mL). Flash chromatography with
pentane gave a mixture of 6d and 7d (13 mg, 0.064 mmol, 13%, 6d/
7d = 1:9.3) as a volatile colourless liquid. Starting material 5d
(69 mg, 43%) was also recovered.
129.4 (CH), 119.3 (CN), 109.8 (CCN), 37.8 (CH2CH), 35.4
(CCH2), –1.1 (SiCH3) ppm.
NMR spectroscopic data for 7g: 1H NMR (500 MHz, CDCl3): δ =
3
7.60–7.52 (m, 2 H, CH), 7.31–7.20 (m, 2 H, CH), 2.09 (ddd, J =
3
NMR spectroscopic data for 6d: 1H NMR (400 MHz, CDCl3): δ =
7.33–7.22 (m, 2 H, CH), 7.19 (m, 3 H, CH), 6.09 (dt, 3J = 18.6,
6.1 Hz, 1 H, CH), 5.68 (dt, 3J = 18.6, 4J = 1.5 Hz, 1 H, SiCH),
2.72 (t, 3J = 8.6 Hz, 2 H, CCH2), 2.42 (dtd, 3J = 9.3, 6.3, 4J =
1.5 Hz, 2 H, CH2CH), 0.05 (s, 9 H, SiCH3) ppm. 13C NMR
(100 MHz, CDCl3): δ = 146.3 (CH2CH), 142.2 (C), 130.6 (SiCH),
128.6 (CH), 128.4 (CH), 125.9 (CH), 38.6 (CHCH2), 35.4 (CCH2),
–1.0 (SiCH3) ppm.
8.6, 8.6, 6.0 Hz, 1 H, CCH), 1.23 (ddddd, J = 10.2, 8.8, 8.8, 5.9,
4.4 Hz, 1 H, CH), 1.14 (ddd, 3J = 8.4, 8.4, 2J = 5.2 Hz, 1 H, CH2),
0.63 (ddd, 3J = 5.8, 5.7, 2J = 5.7 Hz, 1 H, CH2), 0.43 (dd, 2J =
3
14.8, J = 4.4 Hz, 1 H, SiCH2), –0.03 (s, 9 H, SiCH3), –0.08 (dd,
3
2J = 14.8, J = 10.2 Hz, 1 H, SiCH2) ppm. 13C NMR (125 MHz,
CDCl3): δ = 146.4 (C), 131.7 (CH), 129.7 (CH), 119.5 (CN), 109.2
(CCN), 22.0 (CCH), 16.4 (CH), 15.2 (SiCH2), 12.5 (CH2), –1.4
(SiCH3) ppm.
IR: ν = 3068, 2954, 2899, 2227, 1608, 1505, 1248, 862, 839 cm–1.
NMR spectroscopic data for 7d: 1H NMR (400 MHz, CDCl3): δ =
7.33–7.22 (m, 2 H, CH), 7.19 (m, 3 H, CH), 2.06 (ddd, J = 8.7,
˜
HRMS (EI+): calcd. for C14H19NSi [M]+ 229.1287; found 229.1264.
3
5.9, 5.9 Hz, 1 H, CCH), 1.17–1.07 (m, 1 H, CH), 1.06–0.98 (m, 1
4-(3-Cyanophenyl)-1-(trimethylsilyl)but-1-ene (6h) and cis-1-(Tri-
methylsilyl)methyl-2-(3-cyanophenyl)cyclopropane (7h): Prepared
from hydrazone 5h (177 mg, 0.49 mmol) according to the general
procedure with HNTf2 (14 mg) and diglyme (9.9 mL). Flash
chromatography with pentane gave a mixture of 6h and 7h (21 mg,
0.09 mmol, 18%, 6h/7h = 1:10) as a colourless liquid. Starting ma-
terial 5h (10 mg, 6%) was also recovered.
H, CH2), 0.56 (dd, 3J = 5.6 Hz, 1 H, CH2), 0.51 (dd, 2J = 14.7 Hz,
2
3J = 4.3 Hz, 1 H, SiCH2), –0.02 (s, 9 H, SiCH3), –0.07 (dd, J =
14.9 Hz, 3J = 10.4 Hz, 1 H, SiCH2). 13C NMR (100 MHz, CDCl3):
δ = 140.0 (C), 129.3 (CH), 127.9 (CH), 125.6 (CH), 21.4 (CCH),
15.3 (CH), 15.0 (SiCH2), 11.6 (CH2), –1.3 (SiCH3).
IR: ν = 2954, 2924, 2852, 1617, 1449, 1247, 990, 862, 837 cm–1.
˜
HRMS (EI+): calcd. for C12H17Si [M – CH3]+ 189.1100; found
189.1099.
NMR spectroscopic data for 7h: 1H NMR (500 MHz, CDCl3): δ =
3
2
3
7.47 (ddd, J = 7.3, J = 1.7 Hz, 1 H, CH), 7.43 (dd, J = 1.7 Hz,
1 H, CH), 7.42–7.32 (m, 2 H, CH), 2.06 (ddd, 3J = 8.6, 8.6, 5.9 Hz,
1 H, CCH), 1.18 (ddddd, 3J = 10.2, 8.8, 8.8, 5.8, 4.2 Hz, 1 H, CH),
4-(3-Hydroxyphenyl)-1-(trimethylsilyl)but-1-ene (6f) and (؎)-cis-1-
(Trimethylsilyl)methyl-2-(3-hydroxyphenyl)cyclopropane (7f): Pre-
pared from hydrazone 5f (188 mg, 0.54 mmol) according to the ge-
neral procedure with HNTf2 (15 mg) and diglyme (10.8 mL). Flash
chromatography with pentane/diethyl ether (8:2) gave a mixture of
6f and 7f (46 mg, 0.21 mmol, 39%, 6f/7f = 23:1) as a colourless
liquid. Starting material 5f (43 mg, 23%) was also recovered.
3
2
3
1.11 (ddd, J = 8.4, 8.4, J = 5.0 Hz, 1 H, CH2), 0.56 (ddd, J =
2
2
3
5.7, 5.7, J = 5.7 Hz, 1 H, CH2), 0.45 (dd, J = 14.6, J = 4.2 Hz,
1 H, SiCH2), –0.02 (s, 9 H, SiCH3), –0.17 (dd, 2J = 14.7, 3J =
10.4 Hz, 1 H, SiCH2) ppm. 13C NMR (125 MHz, CDCl3): δ =
141.8 (C), 133.9 (CH), 132.7 (CH), 129.4 (CH), 128.7 (CH), 119.4
(CN), 112.0 (CCN), 21.1 (CCH), 15.5 (CH), 15.4 (SiCH2), 12.0
(CH2), –1.3 (SiCH3) ppm.
1
NMR spectroscopic data for 6f: H NMR (500 MHz, CDCl3): δ =
7.15 (ddd, 3J = 7.4, 4J = 1.1, 1.1 Hz, 1 H, CH), 6.71 (ddd, 3J =
The NMR spectroscopic data for 6h could not be fully resolved.
Relevant resonances were identified, and the relative amount of the
by-product was calculated from the integrations.
4
7.3, J = 1.2, 1.2 Hz, 1 H, CH), 6.69–6.63 (m, 2 H, CH), 6.07 (dt,
3
4
3J = 18.6, 6.1 Hz, 1 H, CH), 5.67 (dt, J = 18.6, J = 1.5 Hz, 1 H,
4
3
SiCH), 4.69 (d, J = 1.5 Hz, 1 H, OH), 2.67 (dd, J = 9.2, 6.7 Hz,
IR: ν = 2954, 2229, 2227, 1601, 1580, 1484, 1248, 860, 840 cm–1.
3
4
˜
2 H, CH2), 2.40 (dt, J = 7.6, J = 1.4 Hz, 2 H, CCH2), 0.05 (s, 9
H, SiCH3) ppm. 13C NMR (125 MHz, CDCl3): δ = 155.5 (COH),
146.1 (CH2CH), 144.2 (C), 130.6 (SiCH), 129.6 (CH), 121.2 (CH),
115.5 (CH), 112.8 (CH), 38.4 (CCH2), 35.2 (CH2CH), –1.0 (SiCH3)
ppm.
HRMS (EI+): calcd. for C14H18NSi [M]+ 228.1203; found 228.1203.
4-(4-Bromophenyl)-1-(trimethylsilyl)but-1-ene (6i) and (؎)-cis-1-
(Trimethylsilyl)methyl-2-(4-bromophenyl)cyclopropane (7i): Pre-
pared from hydrazone 5i (212 mg, 0.51 mmol) according to the ge-
neral procedure with HNTf2 (14 mg) and diglyme (10.3 mL). Flash
chromatography with pentane gave a mixture of 6i and 7i (52 mg,
0.18 mmol, 36%, 6i/7i = 1.1:1) as a colourless liquid. Starting mate-
rial 5i (45 mg, 25%) was also recovered.
The NMR spectroscopic data for 7f could not be fully resolved.
Relevant resonances were identified, and the relative amount of the
by-product was calculated from the integrations.
IR: ν = 3330, 2954, 1615, 1589, 1455, 1247, 1155, 990, 864,
˜
1
NMR spectroscopic data for 6i: H NMR (500 MHz, CDCl3): δ =
837 cm–1. HRMS (EI+): calcd. for C13H20OSi [M]+ 220.1278; found
220.1250.
7.50–7.34 (m, 2 H, CH), 7.16–6.94 (m, 2 H, CH), 6.04 (dt, 3J =
18.5, 6.1 Hz, 1 H, CH), 5.66 (dt, 3J = 18.5, 4J = 1.5 Hz, 1 H, SiCH),
2.67 (dt, 3J = 9.0, 6.7 Hz, 2 H, CCH2), 2.38 (dtd, 3J = 7.6, 6.2, 4J =
1.5 Hz, 2 H, CH2), 0.05 (s, 9 H, SiCH3) ppm. 13C NMR (125 MHz,
CDCl3): δ = 145.66 (CH2CH), 141.06 (C), 131.07 (SiCH), 131.03
(CH), 130.38 (CH), 119.61 (CBr), 38.35 (CH2CH), 34.72 (CCH2),
–1.06 (SiCH3) ppm.
4-(4-Cyanophenyl)-1-(trimethylsilyl)but-1-ene (6g) and (؎)-cis-1-
(Trimethylsilyl)methyl-2-(4-cyanophenyl)cyclopropane (7g): Pre-
pared from hydrazone 5g (180 mg, 0.50 mmol) according to the
general procedure with HNTf2 (14 mg) and diglyme (10 mL). Flash
chromatography with pentane gave a mixture of 6g and 7g (46 mg,
0.20 mmol, 40%, 6g/7g = 1:2.8) as a colourless liquid. Starting ma-
terial 5g (40 mg, 22%) was also recovered.
1
NMR spectroscopic data for 7i: H NMR (500 MHz, CDCl3): δ =
3
7.50–7.33 (m, 2 H, CH), 7.16–6.86 (m, 2 H, CH), 1.99 (ddd, J =
NMR spectroscopic data for 6g: 1H NMR (500 MHz, CDCl3): δ =
7.60–7.54 (m, 2 H, CH), 7.32–7.18 (m, 2 H, CH), 6.01 (dt, 3J =
18.5, 6.2 Hz, 1 H, CH), 5.64 (dd, 3J = 18.6, 4J = 1.5 Hz, 1 H,
8.6, 8.6, 5.9 Hz, 1 H, CCH), 1.11 (ddddd, J = 10.0, 8.7, 5.7, 5.6,
3
4.2 Hz, 1 H, CH), 1.05 (ddd, 3J = 8.4, 8.4, 2J = 4.9 Hz, 1 H, CH2),
0.51 (ddd, 3J = 5.7, 5.6, 2J = 5.6 Hz, 1 H, CH2), 0.47 (dd, 2J =
3
3
3
SiCH), 2.77 (t, J = 7.8 Hz, 2 H, CCH2), 2.41 (dtd, J = 7.8, 6.2,
14.8, J = 4.2 Hz, 1 H, SiCH2), –0.02 (s, 9 H, SiCH3), –0.13 (dd,
4J = 1.6 Hz, 2 H, CH2), 0.03 (s, 9 H, SiCH3) ppm. 13C NMR 2J = 14.8, J = 10.3 Hz, 1 H, SiCH2) ppm. 13C NMR (125 MHz,
3
(125 MHz, CDCl3): δ = 147.7 (C), 144.9 (CH2CH), 132.2 (SiCH),
CDCl3): δ = 139.11 (C), 131.41 (CH), 130.94 (CH), 119.31 (CBr),
8031
Eur. J. Org. Chem. 2015, 8024–8033
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org

S. Dittrich, F. Bracher
FULL PAPER
20.95 (CCH), 15.37 (CH), 15.01 (SiCH2), 11.82 (CH2), –1.29
(SiCH3) ppm.
ing to the general procedure with HNTf2 (13 mg) and diglyme
(9.3 mL). Flash chromatography with pentane gave a mixture of 6l
and 7l (28 mg, 0.10 mmol, 22%, 6l/7l = 1:5) as a colourless liquid.
IR: ν = 2954, 1616, 1488, 1073, 1011, 839, 838 cm–1. HRMS (EI+):
˜
calcd. for C13H19BrSi [M]+ 282.0434; found 282.0427.
1
NMR spectroscopic data for 6l: H NMR (400 MHz, CDCl3): δ =
7.46–7.30 (m, 4 H, CH), 6.03 (dt, 3J = 18.5, 6.2 Hz, 1 H, CH), 5.65
4-(3-Bromophenyl)-1-(trimethylsilyl)but-1-ene (6j) and (؎)-cis-1-
(Trimethylsilyl)methyl-2-(3-bromophenyl)cyclopropane (7j): Pre-
pared from hydrazone 5j (285 mg, 0.69 mmol) according to the ge-
neral procedure with HNTf2 (19 mg) and diglyme (13.8 mL). Flash
chromatography with pentane gave a mixture of 6j and 7j (41 mg,
0.15 mmol, 21%, 6j/7j = 1:1.2) as a colourless liquid. Starting mate-
rial 5j (129 mg, 45%) was also recovered.
3
4
3
(dt, J = 18.6, J = 1.5 Hz, 1 H, SiCH), 2.78 (dd, J = 8.8, 6.8 Hz,
3
4
2 H, CCH2), 2.43 (dtd, J = 7.5, 6.2, J = 1.5 Hz, 2 H, CH2), 0.04
(s, 9 H, SiCH3) ppm. 13C NMR (100 MHz, CDCl3): δ = 145.3
(CH2CH), 142.9 (C), 132.5, 132.1, 131.5, 130.5, 130.1, 128.8, 128.3,
126.1, 126.0, 126.0, 125.9, 123.2, 122.5, 122.4, 38.2 (CH2CH), 35.1
(CCH2), –1.1 (SiCH3) ppm. Note: Unassigned 13C signals given for
both compounds.
1
NMR spectroscopic data for 6j: H NMR (500 MHz, CDCl3): δ =
1
NMR spectroscopic data for 7l: H NMR (400 MHz, CDCl3): δ =
7.36–7.28 (m, 2 H, CH), 7.18–7.11 (m, 1 H, CH), 7.11–7.04 (m, 1
7.47–7.30 (m, 4 H, CH), 2.09 (ddd, 3J = 8.6, 8.6, 5.9 Hz, 1 H,
CCH), 1.22–1.13 (m, 1 H, CH), 1.13–1.05 (m, 1 H, CH2), 0.59
(ddd, 3J = 5.6, 5.6, 5.5 Hz, 1 H, CH2), 0.46 (dd, 2J = 14.7, 3J =
3
3
H, CH), 6.03 (dt, J = 18.6, 6.2 Hz, 1 H, CH), 5.65 (dt, J = 18.6,
4J = 1.5 Hz, 1 H, SiCH), 2.68 (dd, J = 9.0, 6.7 Hz, 2 H, CCH2),
3
2.39 (dtd, 3J = 7.7, 6.2, 4J = 1.5 Hz, 2 H, CH2), 0.04 (s, 9 H, SiCH3)
ppm. 13C NMR (125 MHz, CDCl3): δ = 145.5 (CH2CH), 144.5
(C), 131.7 (CH), 131.2 (SiCH), 129.9 (CH), 129.0 (CH), 127.3
(CH), 122.42 (CBr), 38.28 (CH2CH), 34.95 (CCH2), –1.07 (SiCH3)
ppm.
2
4.3 Hz, 1 H, SiCH2), –0.03 (s, 9 H, SiCH3), –0.09 to –0.17 (m, J
= 14.7 Hz, 1 H, 3J = 10.8 Hz, SiCH2). 13C NMR (100 MHz,
CDCl3): δ = 141.1 (C), 132.5, 132.1, 131.5, 130.45, 130.1, 128.8,
128.3, 126.1, 126.0, 126.0, 125.9, 123.2, 122.5, 122.4, 122.4, 122.4,
21.4 (CCH), 15.4 (SiCH2), 15.3 (CH2), 11.9 (CH2), –1.3 (SiCH3)
ppm.
1
NMR spectroscopic data for 7j: H NMR (500 MHz, CDCl3): δ =
7.39–7.27 (m, 2 H, CH), 7.17–7.10 (m, 1 H, CH), 7.11–7.04 (m, 1
IR: ν = 2955, 1441, 1326, 1248, 1164, 1127, 1074, 862, 840 cm–1.
H, CH), 2.02 (ddd, 3J = 8.6, 8.6, 5.9 Hz, 1 H, CCH), 1.12 (ddddd,
˜
HRMS (EI+): calcd. for C14H18F3Si [M – H]+ 271.1124; found
271.1123.
3
3J = 10.1, 8.7, 5.7, 5.6, 4.2 Hz, 1 H, CH), 1.05 (ddd, J = 8.4, 8.4,
2
2J = 4.9 Hz, 1 H, CH2), 0.53 (ddd, 3J = 5.7, 5.6, J = 5.7 Hz, 1 H,
2
3
CH2), 0.49 (dd, J = 14.8, J = 4.2 Hz, 1 H, SiCH2), –0.02 (s, 9 H,
6-Phenyl-1-(trimethylsilyl)hexa-1,4-diene (6q): Prepared from
hydrazone 5q (100 mg, 0.29 mmol) similarly to the general pro-
cedure, but with triflime (25 mg, 0.089 mmol, 30 mol-%) at 125 °C,
and with a 10 min reaction time. The total amount of diglyme used
was 5.6 mL. The work-up procedure was the same as that described
above. Flash chromatography with pentane gave a mixture of two
olefin isomers 6q (33 mg, 0.14 mmol, 49%, E/Z Ͼ 15:1) as a colour-
SiCH3), –0.12 (dd, J = 14.7, J = 10.3 Hz, 1 H, SiCH2) ppm. 13C
NMR (125 MHz, CDCl3): δ = 142.7 (C), 132.4 (CH), 129.4 (CH),
128.7 (CH), 128.0 (CH), 122.1 (CBr), 21.2 (CCH), 15.4 (SiCH2),
15.2 (CH), 11.8 (CH2), –1.3 (SiCH3) ppm.
2
3
IR: ν = 2953, 1616, 1595, 1566, 1477, 1247, 862, 838 cm–1. HRMS
˜
(EI+): calcd. for C13H19BrSi [M]+ 282.0434; found 282.0406.
1
less liquid. H NMR (500 MHz, CDCl3): δ = 7.34–7.28 (m, 2 H,
4-(3-Methoxyphenyl)-1-(trimethylsilyl)but-1-ene (6k) and (؎)-cis-1-
(Trimethylsilyl)methyl-2-(3-methoxyphenyl)cyclopropane (7k): Pre-
pared from hydrazone 5k (208 mg, 0.57 mmol) similarly to the ge-
neral procedure, with triflime (16 mg, 0.057 mmol, 10 mol-%) at
100 °C, and with a 10 min reaction time. The total amount of di-
glyme used was 11.4 mL. The work-up procedure was the same as
that described above. Flash chromatography with pentane gave a
mixture of 6k and 7k (68 mg, 0.29 mmol, 51%, 6k/7k = 16.5:1) as
a colourless liquid.
CH), 7.24–7.18 (m, 3 H, CH), 6.04 (dt, 3J = 18.6, 5.9 Hz, 1 H,
CH), 5.68 (d, 3J = 18.5 Hz, 1 H, SiCH), 5.62 (dt, 3J = 15.5, 6.5 Hz,
1 H, CH), 5.54 (dt, 3J = 15.5, 6.3 Hz, 1 H, CH), 3.38 (d, 3J =
3
6.5 Hz, 2 H, CCH2), 2.86 (dd, J = 5.9 Hz, 2 H, CHCH2), 0.07 (s,
9 H, CH3) ppm. 13C NMR (125 MHz CDCl3): δ = 145.1 (CH),
141.0 (C), 130.8 (CH), 130.3 (CH), 129.4 (CH), 128.7 (CH), 128.5
(CH), 126.1 (CH), 39.7 (CHCH2), 39.2 (CCH2), –1.0 (SiCH3) ppm.
IR: ν = 2955, 1613, 1494, 1453, 1425, 1247, 988, 968, 861, 837, 744,
˜
697 cm–1. HRMS (EI+): calcd. for C15H22Si [M]+ 230.1491; found
230.1481.
NMR spectroscopic data for 6k: 1H NMR (400 MHz, CDCl3): δ
3
3
= 7.20 (dd, J = 8.9, 7.6 Hz, 1 H, CH), 6.78 (d, J = 7.9 Hz, 2 H,
CH), 6.76–6.71 (m, 2 H, CH), 6.09 (dt, 3J = 18.5, 6.1 Hz, 1 H,
CH), 5.68 (dt, 3J = 18.5, 4J = 1.5 Hz, 1 H, SiCH), 3.80 (s, 3 H,
OCH3), 2.70 (dd, 3J = 9.2, 6.7 Hz, 2 H, CCH2), 2.42 (tdd, 3J = 7.6,
Supporting Information (see footnote on the first page of this arti-
1
cle): Copies of H and 13C NMR spectra for all compounds, crys-
tallographic data for compound 3.
4
6.3, J = 1.6 Hz, 2 H, CH2), 0.05 (s, 9 H, SiCH3) ppm. 13C NMR
(100 MHz, CDCl3): δ = 159.8 (COCH3), 146.3 (CH2CH), 143.9
(C), 130.6 (SiCH), 129.4 (CH), 121.0 (CH), 114.3 (CH), 111.3
(CH), 55.3 (OCH3), 38.5 (CH2CH), 35.4 (CCH2), –1.0 (SiCH3)
ppm.
Acknowledgments
The authors thank Dr. Peter Mayer for the determination of the
crystal structure and Prof. Dr. Manfred Heuschmann for fruitful
discussions.
The NMR spectroscopic data for 7k could not be fully resolved.
Relevant resonances were identified, and the relative content of the
by-product was calculated from the integrations.
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˜
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4-(3-Trifluoromethylphenyl)-1-(trimethylsilyl)but-1-ene (6l) and (؎)-
cis-1-(Trimethylsilyl)methyl-2-[3-(trifluoromethyl)phenyl]cycloprop-
ane (7l): Prepared from hydrazone 5l (188 mg, 0.46 mmol) accord-
8032
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© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2015, 8024–8033

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Published Online: November 13, 2015
Eur. J. Org. Chem. 2015, 8024–8033
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
8033