Tin-Mediated One-Pot Synthesis of α,α-Disubstituted Homoallylic Hydrazides from Ketones, Acylhydrazines and Allyl Bromide

Article abstract of DOI:10.1055/s-0035-1560803

An efficient multicomponent one-pot reaction was developed for the synthesis of α,α-disubstituted homoallylic hydrazides by treating ketones, acylhydrazines and allyl bromide with tin powder in tetrahydrofuran under reflux. The reaction proceeds smoothly

Full text of DOI:10.1055/s-0035-1560803

SYNTHESIS
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© Georg Thieme Verlag Stuttgart · New York
2016, 48, 293–301
paper
293
A. Lu et al.
Paper
Synthesis
Tin-Mediated One-Pot Synthesis of α,α-Disubstituted Homoallylic
Hydrazides from Ketones, Acylhydrazines and Allyl Bromide
Ailing Lua
O
R3
Danfeng Huang*a
Ke-Hu Wanga
Yingpeng Sua
Junyan Maa
Yanli Xua
one pot
Sn
O
O
NH
Br
+
+
NH2
HN
R3
N
R1
R2
THF, reflux
H
R1
R2
R1, R2, R3 = aryl, heteroaryl, alkyl
31 examples
up to 93% yield
Yulai Hu*a,b
a College of Chemistry and Chemical Engineering, Northwest
Normal University, 967 Anning East Road, Lanzhou 730070,
P. R. of China
huangdf@nwnu.edu.cn
b State Key Laboratory of Applied Organic Chemistry, Lanzhou
University, Lanzhou 730000, P. R. of China
Received: 22.07.2015
Accepted after revision: 30.09.2015
Published online: 04.11.2015
logues. The indium-induced three-component allylation re-
action of ketones, acylhydrazine and allyl bromide was re-
cently reported to give the corresponding α,α-disubstituted
homoallylic hydrazides in high yields.19
DOI: 10.1055/s-0035-1560803; Art ID: ss-2015-h0449-op
Abstract An efficient multicomponent one-pot reaction was devel-
oped for the synthesis of α,α-disubstituted homoallylic hydrazides by
treating ketones, acylhydrazines and allyl bromide with tin powder in
tetrahydrofuran under reflux. The reaction proceeds smoothly without
any catalyst under mild conditions to give the corresponding products
in high yields.
Organotin compounds13,20 have received much attention
and have been applied extensively in organic synthesis due
to their stability toward heat, hydrolysis and oxidation,
their tolerance to functional groups, and their high selectiv-
ity. Allylic stannanes, especially allyltributyltin, have been
widely used to synthesize homoallylic amines.21–23 Howev-
er, most stannanes are very toxic and need to be prepared
beforehand by means of other organometallic compounds
such as magnesium, sodium and aluminum derivatives.24
Moreover, in conventional allylation using allyltributyltin,
only the allyl group is delivered into the product, with the
tributyltin group usually being discarded as waste after the
reaction; removal of the R3Sn residue from the reaction
mixture is required to obtain pure products. Thus, when al-
lyltributyltin is used as a nucleophile, the process is not
atom economic nor environmentally benign. To overcome
this drawback, tin-powder-promoted allylation processes
have been used as an alternative method.13,25–27 In this pro-
cess, the toxic allylic stannanes are replaced by tin powder
and allyl bromide, and the amount of the organic moiety is
much reduced.
Because of some advantages of tin-metal-promoted re-
actions, we are interested in tin-promoted organic reac-
tions, and have found that tin-mediated one-pot allylation
of aldehydes, amines and allyl bromide gives the homoallyl-
ic amines chemoselectively without the formation of ho-
moallylic alcohols from allylation of the aldehydes or allylic
amines from allylation of the amines (Scheme 1, a).28 How-
ever, this method cannot be applied to ketones; if ketones
are used instead of aldehydes under the same conditions,
allylation of the amines to give allylic amines is the major
reaction (Scheme 1, b).
Key words tin powder, one pot, allylation, ketones, α,α-disubstituted
homoallylic hydrazides
Homoallylic amines are versatile building blocks for ni-
trogen-containing compounds or related natural products,
which are usually biologically active.1–3 They can also be
easily transformed into a variety of other valuable function-
al groups.4–6 Thus, many synthetic processes have been de-
veloped for their synthesis.7–9 Among these methods, nuc-
leophilic addition of allylmetal reagents to the C=N bond of
imines or their analogues is an effective and widely used
method.10–12 However, α-deprotonation usually takes place
exclusively over the addition reactions when typical strong
nucleophiles such as allyllithium or allylmagnesium re-
agents react with ‘enolizable’ base-sensitive imines or their
derivatives. Low-reactive allylboronate, allylsilane and al-
lylic stannane reagents have been successfully used for the
preparation of homoallylic amines in high yields. Allylindi-
um reagents are particularly interesting for this purpose as
they display low basicity, high chemoselectivity and low
toxicity.10,13 However, Lewis acids or transition-metal cata-
lysts are often needed in this transformation. As for α,α-
disubstituted homoallylic amines, their synthesis is known
to be difficult. To date, there have been a few reports on the
synthesis of these compounds based on the addition of al-
lylsilanes14–17 or allylboronates18 to ketimines or their ana-
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Synthesis
R2
O
R3
O
Sn
Br
HN
R1
R2-NH2
+
+
O
(a)
O
Sn
R1
H
1,4-dioxane
r.t.
Br
NH
NH2
+
+
HN
R3
N
R1
R2
THF
reflux
R1
R2
H
1
2
3
R3
4
HN
R1
R2
Scheme 2 Homoallylation of ketones
O
Sn
3
Br
+
+
(b)
R -NH2
R1
R2
1,4-dioxane
r.t.
R3
We first investigated the one-pot reaction of cyclohexa-
none (1a), benzoylhydrazine (2a), allyl bromide (3) and tin
powder in tetrahydrofuran at room temperature. After 24
hours, the desired product 4a was obtained in 65% yield.
Considering ketimines are less reactive than aldimines, we
carried out the same reaction under reflux. To our delight,
the yield of 4a increased to 90% and the reaction time was
dramatically decreased to three hours (Scheme 3).
N
ketones
O
R2
O
O
Sn
Br
NH
+
+
NH2
R2
N
H
(c)
HN
R1
R1
H
THF
r.t.
Various ketones were then examined in the reaction,
and the results are summarized in Scheme 3. Various ali-
phatic cyclic ketones gave the products in good to excellent
yields (4a–e). Indanones also produced the products in high
yields (4f–i), but no target product 4j was detected when 1-
tetralone was used in the reaction. Further investigation in-
dicated that the corresponding hydrazone was formed in
23% yield from 1-tetralone and benzoylhydrazine, but could
not react further with allyl bromide and tin. Reaction with
acyclic aliphatic ketones occurred smoothly to give the cor-
responding products in good yields (4k–n). It is worth not-
ing that sterically hindered nonan-5-one gave product 4m
in reasonable yield, a result which has not been observed in
other metal-promoted reactions. Furthermore, the α,β-un-
saturated ketone showed exclusive 1,2-addition (product
4n). As for the aromatic ketones, most gave the products in
high yields; even the sterically more hindered ketone 2-
methyl-1-phenylpropan-1-one provided a 61% yield of
product 4v. However, ketones with two phenyl rings at-
tached to the carbonyl group such as benzophenone did not
afford the allylic product (4u). The electronic properties of
substituents on the phenyl ring of aromatic ketones had lit-
tle effect on the reaction, but their position on the phenyl
ring had a great influence on the results. For example, m-
bromoacetophenone and p-bromoacetophenone provided
the products 4q and 4r in high yields, but o-bromoace-
tophenone did not give the product 4p. This may be due to
steric hindrance. In any event, the results in Scheme 3 dis-
play a broad substrate scope for ketones.
Scheme 1 Homoallylation of aldehydes
Since it is known that N-acylhydrazones often serve as
imine equivalents which can react with various nucleo-
philes,29 we used acylhydrazines in our laboratory to re-
place the amines in the reaction. The one-pot reaction of al-
dehydes, acylhydrazines, allyl bromide and tin occurred
smoothly to give the corresponding homoallylic hydrazides,
as expected (Scheme 1, c).30 Literature reports indicate that
aldehyde-derived hydrazones are smoothly allylated with
different allylation reagents, such as allyltin,31 allylsilane32
and allylindium33 reagents. In contrast, allylations of steri-
cally hindered ketone-derived hydrazones have been
scarcely reported. In 2001, Kobayashi and co-workers re-
ported the allylation of ketone-derived hydrazones using al-
lyltrichlorosilane.34 In 2008, the same research group dis-
closed another allylation method for ketone-derived hydra-
zones which uses pinacolyl allylboronate with indium(I)
iodide catalysis.35 Recently, Lee and Jang reported an indi-
um-promoted three-component allylation of ketone-de-
rived hydrazones generated in situ in the presence of a cat-
alytic amount of zinc perchlorate hexahydrate.19 Based on
our previous research work, the allylation of ketone-derived
hydrazones generated in situ was explored. To our delight,
when ketones were reacted with acylhydrazines, allyl bro-
mide and tin, the α,α-disubstituted homoallylic hydrazides
could be obtained in high yields. Herein, we report a facile
one-pot synthesis of α,α-disubstituted homoallylic hydra-
zides from ketones, acylhydrazines and allyl bromide pro-
moted by tin powder (Scheme 2). It offers a convenient, in-
expensive and efficient method for the formation of α,α-
disubstituted homoallylic hydrazides, which can be easily
converted into the corresponding homoallylic amines by N–
N bond cleavage.34
To test the generality of acylhydrazines, different acyl-
hydrazines were reacted with different ketones in the pres-
ence of allyl bromide and tin powder under the above reac-
tion conditions (Scheme 4). The reactions of various aro-
matic acylhydrazines with various ketones gave the desired
products in excellent yields. However, the desired products
4ad, 4ae and 4al were not obtained when aliphatic acylhy-
drazines were used in the reaction.
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Further, to test the possibility of N–N bond cleavage in
homoallylic hydrazides, compound 4s was reacted with sa-
marium(II) iodide in tetrahydrofuran at room temperature
for two hours. The corresponding homoallylic amine 5 was
obtained in 85% yield (Scheme 5).
To investigate the mechanism of the reaction, some con-
trol experiments were conducted to determine the reaction
rate between the different reactants (Scheme 6). Firstly, p-
O
Ph
O
O
Sn
NH
Br
NH2
+
+
HN
Ph
N
H
R1
R2
THF, reflux
R1
1
2a
3
R2
4
O
O
O
O
O
H
H
H
H
H
N
N
N
N
N
N
H
N
H
N
H
N
H
N
H
4a
4b
4c
4d
4e
Time: 3 h; Yield: 90%
Time: 6 h; Yield: 78%
Time: 3 h; Yield: 92%
Time: 3 h; Yield: 82%
Time: 8 h; Yield: 58%
O
H
N
N
H
O
H
N
N
H
O
H
N
N
H
O
H
N
N
H
O
H
N
N
H
Cl
Br
4f
4g
4h
4i
4j
Time: 6 h; Yield: n.d.
Time: 3 h; Yield: 73%
Time: 3 h; Yield: 88%
Time: 3 h; Yield: 86%
Time: 3 h; Yield: 62%
O
H
N
N
H
O
H
O
H
O
H
N
N
H
O
H
N
N
H
N
N
4
3
3
N
H
N
H
4k
4l
4m
4n
4o
Time: 3 h; Yield: 73%
Time: 3 h; Yield: 85%
Time: 9 h; Yield: 52%
Time: 2 h; Yield: 80%
Time: 6 h; Yield: 56%
Br
O
H
N
N
H
O
H
N
N
H
O
H
N
N
H
O
H
N
N
H
O
H
N
N
H
Br
Br
4s
4t
4p
4q
4r
Time: 6 h; Yield: 80%
Time: 6 h; Yield: 84%
Time: 10 h; Yield: n.d.
Time: 6 h; Yield: 86%
Time: 6 h; Yield: 80%
O
O
H
N
H
N
N
N
H
H
4u
Time: 6 h; n.d.
4v
Time: 6 h; Yield: 51%
Scheme 3 One-pot reaction of various ketones with benzoylhydrazine. Reagents and conditions: ketone 1 (1 mmol), benzoylhydrazine (2a; 1.5 mmol),
allyl bromide (3; 2.0 mmol), Sn powder (2.5 mmol), THF (5 mL), reflux, 3–10 h; isolated yields are shown; n.d. = not detected.
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O
R3
O
O
Sn
NH
Br
NH2
+
+
HN
R3
N
R1
R2
THF, reflux
H
R1
R2
1
2
3
4
O
O
O
H
N
N
H
O
H
H
H
N
N
N
N
N
N
H
H
H
O
Cl
4aa
4ab
4ac
4ad
Time: 3 h; Yield: 82%
Time: 3 h; Yield: 83%
Time: 3 h; Yield: 84%
Time: 10 h; Yield: n.d.
O
H
N
O
H
N
N
H
O
H
N
N
H
O
H
N
N
H
O
N
16
H
Cl
F
4ae
4af
4ag
4ah
Time: 10 h; Yield: n.d.
Time: 3 h; Yield: 81%
Time: 3 h; Yield: 82%
Time: 3 h; Yield: 91%
O
H
N
N
H
O
H
N
N
H
O
H
N
N
H
O
H
O
Br
N
Br
Br
N
Br
H
F
4ai
4aj
4ak
4al
Time: 7 h; Yield: n.d.
Time: 7 h; Yield: 72%
Time: 7 h; Yield: 74%
Time: 7 h; Yield: 74%
Cl
O
H
N
N
H
N
H
N
N
N
4
4
4
H
H
H
O
O
O
4am
4an
4ao
Time: 3 h; Yield: 84%
Time: 3 h; Yield: 93%
Time: 3 h; Yield: 87%
Scheme 4 One-pot reaction of various ketones with various acylhydrazines. Reagents and conditions: ketone 1 (1 mmol), acylhydrazine 2 (1.5 mmol),
allyl bromide (3; 2.0 mmol), Sn powder (2.5 mmol), THF (5 mL), reflux, 3–10 h; isolated yields are shown; n.d. = not detected.
bromoacetophenone was refluxed in tetrahydrofuran with
benzoylhydrazine. It was obvious from TLC that the reac-
tion occurred after 30 minutes to give the corresponding
hydrazone 6, and the yield reached 81% after five hours
(Scheme 6, a). Hydrazone 6 reacted with allyl bromide and
tin powder under standard reaction conditions to give the
corresponding homoallylic hydrazide 4r in 82% yield
(Scheme 6, b). Secondly, when p-bromoacetophenone was
stirred with allyl bromide and tin powder in tetrahydrofu-
ran under reflux for six hours, no reaction was observed
(Scheme 6, c). Finally, the reaction between benzoylhydra-
zine and allyl bromide under the same conditions gave dou-
ble allylated product 7 in 26% yield (Scheme 6, d), with 48%
recovery of benzoylhydrazine. Apparently, the fastest reac-
tion between the reactants is the formation of acylhydra-
zone from the ketone and the hydrazine.
Based on the above experimental results and the litera-
ture,27,36 the proposed reaction mechanism is as follows
(Scheme 7): ketone 1 reacts with acylhydrazine 2 to form
acylhydrazone 8, which then reacts with allyltin bromide to
give intermediate 9. Then, hydrolysis of intermediate 9 pro-
duces the corresponding product 4.
H2N
O
SmI2
H
N
THF, r.t., argon
2 h
N
H
5
Yield: 85%
4s
Scheme 5 N–N Bond cleavage in homoallylic hydrazide 4s
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O
O
H
N
THF, reflux, 5 h
NH2
+
N
N
(a)
(b)
Yield: 81%
H
O
Br
Br
6
Br
H
N
Sn
reflux, 6 h
O
N
Br
H
N
+
O
Yield: 82%
N
H
6
Br
4r
Sn
O
OH
THF, reflux, 6 h
Br
+
+
(c)
(d)
no reaction after 6 h
Br
Br
O
O
THF, reflux, 6 h
Yield: 26%
NH2
Br
N
N
H
N
H
7
Scheme 6 Control experiments
cess has the following features: catalyst free, operational
simplicity, high yields and avoidance of the preparation of
allyltin reagents beforehand. It offers a novel method for the
synthesis of α,α-disubstituted homoallylic amines.
O
N
R3
O
O
NH
R2
+
NH2
R3
N
R1
R2
Br
H
R1
1
2
8
Sn
All reactions were performed under an atmosphere of dry nitrogen
gas. Flash chromatography was performed using silica gel 60 (230–
400 mesh). IR spectra were obtained using an Alpha Centauri FT-IR
spectrophotometer. High-resolution mass spectra were recorded on a
Bruker APEX II Fourier transform ion cyclotron resonance mass spec-
trometer. 1H NMR and 13C NMR spectra were recorded at 400 MHz
and 100 MHz, respectively, on a Varian Mercury 400 plus spectrome-
ter or at 600 MHz and 150 MHz, respectively, on an Agilent DD2-600
spectrometer. Chemical shifts are reported as δ values (ppm) relative
BrSn
Br2Sn
2
O
R3
NH
O
HN
R2
R3
NH
H2O
1
to TMS for H NMR and chloroform for 13C NMR data. Melting points
BrSnN
were determined on a Beijing Taike X-4 apparatus and are uncorrect-
ed. Chemicals and solvents were either purchased from commercial
suppliers or purified by standard techniques.
R1
R2
R1
4
9
α,α-Disubstituted Homoallylic Hydrazides 4; General Procedure
Scheme 7 Proposed reaction mechanism
A solution of a ketone 1 (1.0 mmol), an acylhydrazine37 2 (1.5 mmol),
allyl bromide (3; 2.0 mmol) and Sn powder (2.5 mmol) in THF (5 mL)
was stirred under reflux for 3–10 h (monitored by TLC). Then, the re-
action mixture was quenched with saturated aq NH4Cl (10 mL). The
organic layer was separated, and the aqueous phase was extracted
with EtOAc (3 × 15 mL). The combined organic layers were dried over
anhydrous MgSO4 and then concentrated under reduced pressure.
The residue was purified by column chromatography on silica gel
(petroleum ether–EtOAc) to afford the desired product.
In conclusion, we have developed an effective tin-medi-
ated one-pot reaction for the synthesis of α,α-disubstituted
homoallylic hydrazides from ketones, acylhydrazines and
allyl bromide. This approach tolerates a broad substrate
scope, including sterically hindered ketones. Compared
with reactions using other metals, this tin-promoted pro-
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N′-(1-Allylcyclohexyl)benzohydrazide (4a)36
13C NMR (100 MHz, CDCl3): δ = 166.7, 144.4, 144.3, 133.7, 132.7,
131.6, 128.6, 128.1, 126.7, 126.4, 125.0, 123.6, 118.7, 72.0, 42.6, 33.8,
30.0.
HRMS (ESI): m/z [M + Na]+ calcd for C19H20N2NaO: 315.1468; found:
315.1473.
Yield: 232.5 mg (90%); colorless syrup.
1H NMR (400 MHz, CDCl3): δ = 7.74 (d, J = 7.6 Hz, 2 H), 7.52 (t, J = 7.2
Hz, 1 H), 7.44 (t, J = 7.2 Hz, 2 H), 7.34 (s, 1 H), 6.09–5.96 (m, 1 H),
5.20–5.00 (m, 3 H), 2.28 (d, J = 7.2 Hz, 2 H), 1.67 (d, J = 4.8 Hz, 2 H),
1.61–1.36 (m, 8 H).
N′-(1-Allyl-5-chloro-2,3-dihydro-1H-inden-1-yl)benzohydrazide
(4g)
13C NMR (100 MHz, CDCl3): δ = 166.8, 134.8, 133.0, 131.6, 128.6,
126.7, 117.4, 58.9, 41.5, 31.6, 25.7, 21.9.
Yield: 287.0 mg (88%); colorless syrup.
N′-(1-Allylcyclobutyl)benzohydrazide (4b)
1H NMR (400 MHz, CDCl3): δ = 7.60 (d, J = 7.6 Hz, 2 H), 7.48 (t, J = 7.2
Hz, 1 H), 7.38 (t, J = 7.6 Hz, 2 H), 7.35–7.24 (m, 2 H), 7.19 (d, J = 8.0 Hz,
2 H), 5.82–5.71 (m, 1 H), 5.41 (s, 1 H), 5.17–5.11 (m, 2 H), 2.99–2.89
(m, 1 H), 2.86–2.75 (m, 1 H), 2.62–2.51 (m, 2 H), 2.21–2.10 (m, 2 H).
13C NMR (100 MHz, CDCl3): δ = 167.0, 146.2, 143.0, 133.8, 133.3,
132.5, 132.4, 131.8, 128.6, 126.7, 125.2, 124.8, 118.9, 71.6, 42.6, 33.9,
29.8.
Yield: 180.1 mg (78%); colorless syrup.
1H NMR (600 MHz, CDCl3): δ = 7.75 (d, J = 8.4 Hz, 3 H), 7.49 (t, J = 7.2
Hz, 1 H), 7.42 (t, J = 7.2 Hz, 2 H), 5.96–5.91 (m, 1 H), 5.16 (t, J = 14.4
Hz, 3 H), 2.40 (d, J = 7.2 Hz, 2 H), 2.09–2.04 (m, 2 H), 1.84 (t, J = 9.6 Hz,
2 H), 1.76–1.63 (m, 2 H).
13C NMR (150 MHz, CDCl3): δ = 167.5, 134.2, 132.8, 131.8, 128.7,
126.9, 117.9, 62.5, 41.7, 30.1, 13.1.
HRMS (ESI): m/z [M + Na]+ calcd for C19H19ClN2NaO: 349.1078; found:
349.1080.
HRMS (ESI): m/z [M + H]+ calcd for C14H19N2O: 231.1492; found:
231.1493.
N′-(1-Allyl-5-bromo-2,3-dihydro-1H-inden-1-yl)benzohydrazide
(4h)
N′-(1-Allylcyclopentyl)benzohydrazide (4c)36
Yield: 319.0 mg (86%); colorless syrup.
Yield: 224.0 mg (92%); colorless syrup.
1H NMR (400 MHz, CDCl3): δ = 7.61 (s, 2 H), 7.53–7.18 (m, 7 H), 5.84–
5.70 (m, 1 H), 5.42 (s, 1 H), 5.18–5.14 (m, 2 H), 3.01–2.89 (m, 1 H),
2.88–2.76 (m, 1 H), 2.57 (s, 2 H), 2.16 (s, 2 H).
13C NMR (100 MHz, CDCl3): δ = 167.0, 146.6, 143.5, 133.2, 132.5,
131.8, 129.6, 128.6, 128.2, 126.7, 125.2, 122.0, 119.0, 71.7, 42.6, 33.8,
29.8.
1H NMR (400 MHz, CDCl3): δ = 7.85–7.70 (m, 3 H), 7.49 (t, J = 7.2 Hz, 1
H), 7.41 (t, J = 7.6 Hz, 2 H), 6.04–5.91 (m, 1 H), 5.21–4.75 (m, 3 H), 2.32
(d, J = 7.2 Hz, 2 H), 1.83–1.48 (m, 8 H).
13C NMR (100 MHz, CDCl3): δ = 167.0, 135.4, 132.8, 131.6, 128.5,
126.8, 117.4, 69.0, 42.8, 35.0, 24.4.
HRMS (ESI): m/z [M + Na]+ calcd for C19H19BrN2NaO: 393.0573; found:
393.0585.
N′-(1-Allylcycloheptyl)benzohydrazide (4d)
Yield: 223.0 mg (82%); white solid; mp 67–68 °C.
1H NMR (400 MHz, CDCl3): δ = 7.72 (d, J = 7.2 Hz, 2 H), 7.54–7.38 (m, 4
H), 6.10–5.98 (m, 1 H), 5.20–5.00 (m, 3 H), 2.23 (d, J = 7.2 Hz, 2 H),
1.70–1.38 (m, 12 H).
13C NMR (100 MHz, CDCl3): δ = 166.7, 135.4, 132.9, 131.6, 128.6,
126.7, 117.3, 62.8, 43.8, 36.6, 30.7, 22.7.
N′-(1-Allyl-6-methyl-2,3-dihydro-1H-inden-1-yl)benzohydrazide
(4i)
Yield: 189.8 mg (62%); yellow solid; mp 86–87 °C.
1H NMR (400 MHz, CDCl3): δ = 7.60 (s, 2 H), 7.52–7.34 (m, 3 H), 7.28–
7.04 (m, 4 H), 5.90–5.75 (m, 1 H), 5.41 (s, 1 H), 5.24–5.10 (m, 2 H),
2.99–2.87 (m, 1 H), 2.85–2.74 (m, 1 H), 2.69–2.52 (m, 2 H), 2.37 (s, 3
H), 2.25–2.08 (m, 2 H).
HRMS (ESI): m/z [M + H]+ calcd for C17H25N2O: 273.1961; found:
273.1965.
13C NMR (100 MHz, CDCl3): δ = 166.6, 144.5, 141.4, 136.1, 133.8,
132.8, 131.6, 129.1, 128.6, 126.7, 124.7, 124.1, 118.6, 71.9, 42.8, 33.9,
29.7, 21.4.
N′-(1-Allylcyclooctyl)benzohydrazide (4e)
Yield: 166.8 mg (58%); colorless syrup.
1H NMR (600 MHz, CDCl3): δ = 7.70 (d, J = 7.2 Hz, 2 H), 7.47 (t, J = 6.6
Hz, 1 H), 7.40 (t, J = 7.2 Hz, 2 H), 7.32 (s, 1 H), 6.07–6.00 (m, 1 H),
5.15–5.10 (m, 2 H), 5.05 (s, 1 H), 2.20 (d, J = 7.2 Hz, 2 H), 1.73–1.69 (m,
2 H), 1.63 (s, 5 H), 1.54–1.51 (m, 4 H), 1.45–1.42 (m, 3 H).
13C NMR (150 MHz, CDCl3): δ = 166.6, 135.5, 133.0, 131.6, 128.6
126.7, 117.1, 62.1, 42.3, 31.9, 28.4, 25.3, 22.4.
HRMS (ESI): m/z [M + Na]+ calcd for C20H22N2NaO: 329.1624; found:
329.1631.
N′-(2-Methylpent-4-en-2-yl)benzohydrazide (4k)19
Yield: 159.2 mg (73%); colorless syrup.
1H NMR (400 MHz, CDCl3): δ = 7.80–7.72 (m, 2 H), 7.52 (t, J = 7.2 Hz, 2
H), 7.44 (t, J = 7.2 Hz, 2 H), 5.99–5.86 (m, 1 H), 5.19–5.10 (m, 3 H), 2.22
(d, J = 7.2 Hz, 2 H), 1.12 (s, 6 H).
HRMS (ESI): m/z [M + H]+ calcd for C18H27N2O: 287.2118; found:
287.2115.
13C NMR (100 MHz, CDCl3): δ = 167.2, 134.5, 132.9, 131.7, 128.6,
126.8, 117.8, 57.6, 44.8, 25.0.
N′-(1-Allyl-2,3-dihydro-1H-inden-1-yl)benzohydrazide (4f)
Yield: 213.2 mg (73%); white solid; mp 89–90 °C.
1H NMR (400 MHz, CDCl3): δ = 7.59 (d, J = 7.6 Hz, 2 H), 7.46 (t, J = 7.2
Hz, 1 H), 7.37 (t, J = 7.6 Hz, 3 H), 7.25 (s, 4 H), 5.88–5.75 (m, 1 H), 5.42
(s, 1 H), 5.21–5.09 (m, 2 H), 3.04–2.93 (m, 1 H), 2.90–2.79 (m, 1 H),
2.67–2.54 (m, 2 H), 2.24–2.09 (m, 2 H).
N′-(4-Methylnon-1-en-4-yl)benzohydrazide (4l)
Yield: 232.8 mg (85%); colorless syrup.
1H NMR (400 MHz, CDCl3): δ = 7.63 (d, J = 7.2 Hz, 2 H), 7.37 (s, 1 H),
7.23 (d, J = 7.2 Hz, 2 H), 5.99–5.87 (m, 1 H), 5.16–4.96 (m, 3 H), 2.34 (s,
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3 H), 2.22 (dd, J = 7.0, 2.9 Hz, 2 H), 1.49–1.20 (m, 8 H), 1.08 (s, 3 H),
0.89 (t, J = 7.2 Hz, 3 H).
13C NMR (100 MHz, CDCl3): δ = 167.0, 134.6, 132.9, 131.6, 128.5,
126.7, 117.5, 59.6, 42.5, 37.7, 32.4, 23.2, 22.7, 22.5, 21.4, 14.0.
HRMS (ESI): m/z [M + H]+ calcd for C17H27N2O: 275.2118; found:
N′-(2-(p-Tolyl)pent-4-en-2-yl)benzohydrazide (4s)
Yield: 235.0 mg (80%); white solid; mp 114–115 °C.
1H NMR (600 MHz, CDCl3): δ = 7.59 (d, J = 7.8 Hz, 2 H), 7.44–7.43 (m, 3
H), 7.36–7.32 (m, 3 H), 7.18 (d, J = 8.4 Hz, 2 H), 5.71–5.64 (m, 1 H),
5.41 (br s, 1 H), 5.10–5.05 (m, 2 H), 2.61 (dd, J = 13.8, 6.6 Hz, 1 H), 2.51
(dd, J = 13.8, 7.8 Hz, 1 H), 2.35 (s, 3 H), 1.53 (s, 3 H).
275.2122.
13C NMR (150 MHz, CDCl3): δ = 166.5, 141.2, 136.6, 133.7, 132.9,
N′-(5-Allylnonan-5-yl)benzohydrazide (4m)
131.6, 129.2, 128.6, 126.8, 126.4, 118.4, 62.2, 46.0, 22.8, 21.0.
HRMS (ESI): m/z [M + H]+ calcd for C19H23N2O: 295.1805; found:
Yield: 157.0 mg (52%); colorless syrup.
1H NMR (400 MHz, CDCl3): δ = 7.71 (d, J = 7.6 Hz, 2 H), 7.51–7.44 (m, 3
H), 7.18 (s, 1 H), 6.05–5.94 (m, 1 H), 5.17 (s, 1 H), 5.12 (d, J = 6.4 Hz, 2
H), 2.23 (d, J = 6.8 Hz, 2 H), 1.41–1.32 (m, 12 H), 0.93 (d, J = 6.4 Hz, 6
H).
13C NMR (150 MHz, CDCl3): δ = 166.5, 135.0, 133.1, 131.6, 128.7,
126.7, 117.4, 61.5, 40.7, 34.8, 25.4, 23.4, 14.1.
295.1806.
N′-(3-Phenylhex-5-en-3-yl)benzohydrazide (4t)32d
Yield: 247.0 mg (84%); colorless syrup.
1H NMR (400 MHz, CDCl3): δ = 7.61–7.23 (m, 10 H), 7.13 (s, 1 H),
5.91–5.80 (m, 1 H), 5.55 (d, J = 6.4 Hz, 1 H), 5.16–5.04 (m, 2 H), 2.66
(d, J = 7.2 Hz, 2 H), 1.94–1.77 (m, 2 H), 0.82 (t, J = 7.2 Hz, 3 H).
HRMS (ESI): m/z [M + H]+ calcd for C19H31N2O: 303.2431; found:
13C NMR (100 MHz, CDCl3): δ = 165.7, 142.8, 134.0, 132.8, 131.5,
303.2429.
128.5, 128.4, 126.9, 126.6, 126.5, 117.9, 65.0, 40.3, 29.2, 7.8.
N′-((E)-3-Methyl-1-phenylhexa-1,5-dien-3-yl)benzohydrazide (4n)
Yield: 245.0 mg (80%); yellow solid; mp 120–122 °C.
N′-(2-Methyl-3-phenylhex-5-en-3-yl)benzohydrazide (4v)
1H NMR (400 MHz, CDCl3): δ = 7.69 (d, J = 7.2 Hz, 2 H), 7.56–7.44 (m, 2
H), 7.42–7.34 (m, 4 H), 7.30 (t, J = 7.5 Hz, 2 H), 7.23 (t, J = 7.2 Hz, 1 H),
6.51 (d, J = 16.4 Hz, 1 H), 6.27 (d, J = 16.4 Hz, 1 H), 5.97–5.84 (m, 1 H),
5.48–5.10 (m, 3 H), 2.49–2.37 (m, 2 H), 1.34 (s, 3 H).
13C NMR (100 MHz, CDCl3): δ = 167.0, 136.9, 134.1, 133.6, 132.9,
131.6, 129.8, 128.6, 128.5, 127.5, 126.7, 126.4, 118.5, 61.2, 44.0, 22.2.
Yield: 157.0 mg (51%); colorless syrup.
1H NMR (600 MHz, CDCl3): δ = 7.57 (d, J = 7.2 Hz, 2 H), 7.52 (d, J = 7.2
Hz, 2 H), 7.45 (t, J = 7.2 Hz, 1 H), 7.40–7.35 (m, 4 H), 7.28 (t, J = 7.2 Hz,
1 H), 7.23 (d, J = 7.8 Hz, 1 H), 6.07–6.00 (m, 1 H), 5.67 (d, J = 8.4 Hz, 1
H), 5.20 (d, J = 16.8 Hz, 1 H), 5.10 (d, J = 10.8 Hz, 1 H), 2.91–2.80 (m, 2
H), 2.06–2.00 (m, 1 H), 0.89 (d, J = 6.6 Hz, 3 H), 0.85 (d, J = 6.6 Hz, 3 H).
13C NMR (100 MHz, CDCl3): δ = 165.2, 140.5, 134.9, 133.0, 131.5,
HRMS (ESI): m/z [M + Na]+ calcd for C20H22N2NaO: 329.1624; found:
128.6, 128.1, 127.7, 126.7, 126.6, 117.8, 67.6, 38.6, 35.2, 17.7, 17.2.
329.1625.
HRMS (ESI): m/z [M + H]+ calcd for C20H25N2O: 309.1961; found:
309.1969.
N′-(2-Phenylpent-4-en-2-yl)benzohydrazide (4o)38
Yield: 156.5 mg (56%); white solid; mp 93–94 °C.
N′-(1-Allylcyclohexyl)-4-methylbenzohydrazide (4aa)
1H NMR (400 MHz, CDCl3): δ = 7.57 (dd, J = 12.0, 7.8 Hz, 4 H), 7.46 (t,
J = 7.2 Hz, 1 H), 7.38 (q, J = 7.6 Hz, 4 H), 7.33–7.25 (m, 1 H), 7.16 (s, 1
H), 5.74–5.62 (m, 1 H), 5.44 (s, 1 H), 5.14–5.05 (m, 2 H), 2.66–2.57 (m,
1 H), 2.55–2.47 (m, 1 H), 1.55 (s, 3 H).
Yield: 223.0 mg (82%); white solid; mp 104–105 °C.
1H NMR (400 MHz, CDCl3): δ = 7.63 (d, J = 8.0 Hz, 2 H), 7.40 (s, 1 H),
7.22 (d, J = 8.0 Hz, 2 H), 6.07–5.95 (m, 1 H), 5.27–4.86 (m, 3 H), 2.39 (s,
3 H), 2.26 (d, J = 7.4 Hz, 2 H), 1.73–1.59 (m, 2 H), 1.58–1.35 (m, 8 H).
13C NMR (100 MHz, CDCl3): δ = 166.5, 144.3, 133.5, 132.8, 131.6,
13C NMR (100 MHz, CDCl3): δ = 166.8, 142.0, 134.8, 130.1, 129.2,
128.6, 128.4, 127.0, 126.7, 126.4, 118.5, 62.4, 46.1, 22.7.
126.7, 117.3, 58.8, 41.4, 33.6, 25.7, 21.9, 21.4.
N′-(2-(3-Bromophenyl)pent-4-en-2-yl)benzohydrazide (4q)
HRMS (ESI): m/z [M + H]+ calcd for C17H25N2O: 273.1961; found:
Yield: 308.8 mg (86%); colorless syrup.
273.1959.
1H NMR (400 MHz, CDCl3): δ = 7.71 (s, 1 H), 7.60 (s, 2 H), 7.51–7.18
(m, 7 H), 5.71–5.57 (m, 1 H), 5.42 (s, 1 H), 5.09 (d, J = 12.4 Hz, 2 H),
2.61–2.41 (m, 2 H), 1.52 (s, 3 H).
13C NMR (100 MHz, CDCl3): δ = 166.9, 147.1, 133.0, 132.6, 131.7,
130.1, 129.9, 129.8, 128.6, 126.7, 125.2, 122.8, 119.0, 62.4, 46.1, 22.5.
N′-(1-Allylcyclohexyl)-4-chlorobenzohydrazide (4ab)
Yield: 242.8 mg (83%); white solid; mp 113–115 °C.
1H NMR (400 MHz, CDCl3): δ = 7.66 (d, J = 8.4 Hz, 2 H), 7.50 (s, 1 H),
7.39 (d, J = 8.4 Hz, 2 H), 6.06–5.93 (m, 1 H), 5.24–4.89 (m, 3 H), 2.26
(d, J = 7.2 Hz, 2 H), 1.71–1.59 (m, 2 H), 1.55–1.36 (m, 8 H).
HRMS (ESI): m/z [M + H]+ calcd for C18H20BrN2O: 359.0754; found:
13C NMR (100 MHz, CDCl3): δ = 165.9, 137.8, 134.7, 131.3, 128.8,
359.0765.
128.2, 117.4, 58.9, 41.4, 33.6, 25.7, 21.9.
HRMS (ESI): m/z [M + H]+ calcd for C16H22ClN2O: 293.1415; found:
N′-(2-(4-Bromophenyl)pent-4-en-2-yl)benzohydrazide (4r)32d
Yield: 287.3 mg (80%); white solid; mp 100–101 °C.
293.1420.
1H NMR (400 MHz, CDCl3): δ = 7.60 (d, J = 7.6 Hz, 2 H), 7.52–7.34 (m, 7
H), 7.21 (s, 1 H), 5.70–5.57 (m, 1 H), 5.41 (s, 1 H), 5.12–5.04 (m, 2 H),
2.57–2.47 (m, 2 H), 1.52 (s, 3 H).
N′-(1-Allylcyclohexyl)furan-2-carbohydrazide (4ac)
Yield: 208.0 mg (84%); white solid; mp 76–77 °C.
13C NMR (100 MHz, CDCl3): δ = 166.8, 143.5, 133.0, 132.6, 131.7,
131.5, 128.6, 128.4, 126.7, 121.1, 118.9, 62.3, 46.0, 22.5.
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1H NMR (400 MHz, CDCl3): δ = 7.55 (s, 1 H), 7.45 (d, J = 0.7 Hz, 1 H),
7.11 (d, J = 3.2 Hz, 1 H), 6.51 (dd, J = 3.4, 1.7 Hz, 1 H), 6.06–5.93 (m, 1
H), 5.19–5.10 (m, 2 H), 4.92 (s, 1 H), 2.25 (d, J = 7.4 Hz, 2 H), 1.73–1.60
(m, 2 H), 1.54–1.37 (m, 8 H).
HRMS (ESI): m/z [M + H]+ calcd for C19H22BrN2O: 373.0910; found:
373.0908.
N′-(2-(3-Bromophenyl)pent-4-en-2-yl)-4-fluorobenzohydrazide
(4aj)
13C NMR (100 MHz, CDCl3): δ = 157.5, 146.8, 143.9, 134.4, 117.5,
114.3, 112.0, 58.9, 41.2, 33.5, 25.7, 21.8.
Yield: 279.5 mg (74%); white solid; mp 80–81 °C.
HRMS (ESI): m/z [M + H]+ calcd for C14H21N2O2: 249.1598; found:
249.1605.
1H NMR (400 MHz, CDCl3): δ = 7.71 (s, 1 H), 7.66–7.56 (m, 2 H), 7.50–
7.32 (m, 3 H), 7.23 (t, J = 7.6 Hz, 1 H), 7.03 (t, J = 8.0 Hz, 2 H), 5.69–5.56
(m, 1 H), 5.41 (br s, 1 H), 5.08 (d, J = 13.6 Hz, 2 H), 2.58–2.53 (m, 1 H),
2.49–2.44 (m, 1 H), 1.50 (s, 3 H).
N′-(1-Allyl-2,3-dihydro-1H-inden-1-yl)-3-methylbenzohydrazide
13C NMR (100 MHz, CDCl3): δ = 166.0, 163.5, 147.0, 132.9, 130.2,
129.9, 129.8, 129.2 (JC,F = 25.7 Hz), 128.7, 125.2, 122.8, 119.0, 115.7
(JC,F = 62.7 Hz), 62.3, 46.0, 22.4.
HRMS (ESI): m/z [M + H]+ calcd for C18H19BrFN2O: 377.0659; found:
377.0672.
(4af)
Yield: 248.0 mg (81%); yellow syrup.
1H NMR (400 MHz, CDCl3): δ = 7.45 (s, 1 H), 7.38–7.18 (m, 8 H), 5.87–
5.74 (m, 1 H), 5.40 (br s, 1 H), 5.18–5.10 (m, 2 H), 3.03–2.93 (m, 1 H),
2.88–2.79 (m, 1 H), 2.67–2.54 (m, 2 H), 2.34 (s, 3 H), 2.23–2.08 (m, 2
H).
13C NMR (100 MHz, CDCl3): δ = 166.9, 144.4, 144.3, 138.4, 133.7,
132.7, 132.3, 128.4, 128.1, 127.5, 126.4, 125.0, 123.6, 123.5, 118.5,
72.0, 42.6, 33.8, 30.0, 21.2.
N′-(2-(3-Bromophenyl)pent-4-en-2-yl)furan-2-carbohydrazide
(4ak)
Yield: 259.3 mg (74%); colorless syrup.
HRMS (ESI): m/z [M + Na]+ calcd for C20H22N2NaO: 329.1624; found:
329.1621.
1H NMR (400 MHz, CDCl3): δ = 7.70 (s, 1 H), 7.50–7.32 (m, 4 H), 7.25
(t, J = 7.6 Hz, 1 H), 7.09 (d, J = 3.2 Hz, 1 H), 6.47 (dd, J = 3.4, 1.7 Hz, 1 H),
5.69–5.57 (m, 1 H), 5.26 (s, 1 H), 5.13–5.05 (m, 2 H), 2.60–2.51 (m, 1
H), 2.50–2.42 (m, 1 H), 1.52 (s, 3 H).
N′-(1-Allyl-2,3-dihydro-1H-inden-1-yl)furan-2-carbohydrazide
13C NMR (100 MHz, CDCl3): δ = 157.5, 146.9, 146.4, 144.1, 132.8,
(4ag)
Yield: 231.5 mg (82%); colorless syrup.
130.2, 130.0, 129.7, 125.2, 122.8, 119.0, 114.7, 112.0, 62.4, 46.0, 22.6.
1H NMR (400 MHz, CDCl3): δ = 7.43 (s, 1 H), 7.38–7.32 (m, 2 H), 7.28–
7.20 (m, 3 H), 7.07 (d, J = 3.2 Hz, 1 H), 6.46 (dd, J = 3.2, 1.6 Hz, 1 H),
5.85–5.73 (m, 1 H), 5.34–5.07 (m, 3 H), 3.03–2.91 (m, 1 H), 2.88–2.78
(m, 1 H), 2.65–2.53 (m, 2 H), 2.22–2.08 (m, 2 H).
HRMS (ESI): m/z [M + H]+ calcd for C16H18BrN2O2: 349.0546; found:
349.0550.
4-Methyl-N′-(4-methylnon-1-en-4-yl)benzohydrazide (4am)
13C NMR (100 MHz, CDCl3): δ = 157.5, 146.5, 144.3, 144.2, 144.0,
133.6, 128.1, 126.4, 125.0, 123.5, 118.6, 114.5, 111.9, 72.0, 42.5, 33.9,
29.9.
HRMS (ESI): m/z [M + Na]+ calcd for C17H18N2NaO2: 305.1260; found:
305.1257.
Yield: 267.6 mg (93%); colorless syrup.
1H NMR (400 MHz, CDCl3): δ = 7.64 (d, J = 7.8 Hz, 2 H), 7.37 (s, 1 H),
7.23 (d, J = 7.8 Hz, 2 H), 5.98–5.89 (m, 1 H), 5.18–4.85 (m, 3 H), 2.39 (s,
3 H), 2.27–2.16 (m, 2 H), 1.50–1.20 (m, 8 H), 1.08 (s, 3 H), 0.89 (t, J =
7.0 Hz, 3 H).
13C NMR (100 MHz, CDCl3): δ = 167.0, 142.1, 134.8, 130.1, 129.3,
126.7, 117.5, 59.6, 42.6, 37.8, 32.5, 23.3, 22.8, 22.6, 21.4, 14.0.
HRMS (ESI): m/z [M + H]+ calcd for C18H29N2O: 289.2274; found:
289.2279.
N′-(1-Allyl-5-chloro-2,3-dihydro-1H-inden-1-yl)-4-fluorobenzo-
hydrazide (4ah)
Yield: 313.5 mg (91%); colorless syrup.
1H NMR (400 MHz, CDCl3): δ = 7.61 (dd, J = 7.2, 5.6 Hz, 2 H), 7.38 (br s,
1 H), 7.30–7.15 (m, 3 H), 7.05 (t, J = 8.3 Hz, 2 H), 5.82–5.69 (m, 1 H),
5.36 (br s, 1 H), 5.17–5.11 (m, 2 H), 2.99–2.88 (m, 1 H), 2.86–2.75 (m,
1 H), 2.62–2.50 (m, 2 H), 2.22–2.08 (m, 2 H).
13C NMR (100 MHz, CDCl3): δ = 166.1, 163.6, 146.3 142.9, 133.9,
133.2, 129.1, 129.0, 128.6, 126.7, 125.2 (JC,F = 122.6 Hz), 119.0, 115.8
(JC,F = 62.7 Hz), 71.6, 42.6, 33.9, 29.8.
4-Chloro-N′-(4-methylnon-1-en-4-yl)benzohydrazide (4an)
Yield: 267.8 mg (87%); white solid; mp 68–69 °C.
1H NMR (400 MHz, CDCl3): δ = 7.67 (d, J = 8.4 Hz, 2 H), 7.50 (br s, 1 H),
7.39 (d, J = 8.4 Hz, 2 H), 5.93–5.86 (m, 1 H), 5.15–4.85 (m, 3 H), 2.27–
2.15 (m, 2 H), 1.45–1.18 (m, 8 H), 1.07 (s, 3 H), 0.89 (t, J = 7.2 Hz, 3 H).
13C NMR (100 MHz, CDCl3): δ = 166.8, 134.8, 133.0, 131.6, 128.6,
126.7, 117.4, 58.9, 42.6, 37.8, 32.5, 24.2, 22.8, 22.6, 14.0.
HRMS (ESI): m/z [M + Na]+ calcd for C19H18ClFN2NaO: 367.0984;
found: 367.0986.
HRMS (ESI): m/z [M + H]+ calcd for C17H26ClN2O: 309.1728; found:
309.1733.
N′-(2-(3-Bromophenyl)pent-4-en-2-yl)-4-methylbenzohydrazide
(4ai)
N′-(4-Methylnon-1-en-4-yl)furan-2-carbohydrazide (4ao)
Yield: 269.0 mg (72%); white solid; mp 82–83 °C.
Yield: 221.0 mg (84%); colorless syrup.
1H NMR (400 MHz, CDCl3): δ = 7.71 (s, 1 H), 7.55–7.37 (m, 4 H), 7.28–
7.14 (m, 4 H), 5.70–5.57 (m, 1 H), 5.41 (s, 1 H), 5.13–5.04 (m, 2 H),
2.60–2.54 (m, 1 H), 2.49–2.44 (m, 1 H), 2.36 (s, 3 H), 1.51 (s, 3 H).
13C NMR (100 MHz, CDCl3): δ = 166.9, 147.1, 142.2, 133.0, 130.1,
129.9, 129.8, 129.7, 129.2, 126.7, 125.2, 122.7, 118.9, 62.3, 46.1, 22.4,
21.4.
1H NMR (400 MHz, CDCl3): δ = 7.55 (s, 1 H), 7.45 (d, J = 0.8 Hz, 1 H),
7.12 (d, J = 3.2 Hz, 1 H), 6.51 (dd, J = 3.2, 1.6 Hz, 1 H), 5.99–5.85 (m, 1
H), 5.17–5.08 (m, 2 H), 4.87 (br s, 1 H), 2.27–2.15 (m, 2 H), 1.47–1.23
(m, 8 H), 1.08 (s, 3 H), 0.89 (t, J = 7.0 Hz, 3 H).
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13C NMR (100 MHz, CDCl3): δ = 166.8, 134.8, 133.0, 131.6, 128.6,
126.7, 117.4, 59.6, 42.4, 37.7, 32.5, 23.4, 22.8, 22.5, 19.0.
(11) Kobayashi, S.; Mori, Y.; Fossey, J. S.; Salter, M. M. Chem. Rev.
2011, 111, 2626.
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7774.
HRMS (ESI): m/z [M + H]+ calcd for C15H25N2O2: 265.1911; found:
265.1917.
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Wiley & Sons: Chichester, 2008.
2-(p-Tolyl)pent-4-en-2-amine (5)
Yield: 50.0 mg (85%); colorless syrup.
1H NMR (400 MHz, CDCl3): δ = 7.34 (d, J = 8.4 Hz, 2 H), 7.14 (d, J = 8.4
Hz, 2 H), 5.62–5.52 (m, 1 H), 5.09–5.03 (m, 2 H), 2.56 (dd, J = 13.6, 6.8
Hz, 1 H), 2.41 (dd, J = 13.6, 8.0 Hz, 1 H), 2.33 (s, 3 H), 1.75 (s, 2 H), 1.46
(s, 3 H).
13C NMR (100 MHz, CDCl3): δ = 145.8, 135.9, 134.6, 129.1, 125.3,
118.7, 54.7, 49.8, 31.1, 21.1.
HRMS (ESI): m/z [M + H]+ calcd for C12H18N: 176.1434; found:
176.1439.
(21) Narsaiah, A. V.; Kumar, J. K.; Narsimha, P. Synthesis 2010, 1609.
(22) Li, X.; Liu, X.; Fu, Y.; Wang, L.; Zhou, L.; Feng, X. Chem. Eur. J.
2008, 14, 4796.
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Acknowledgment
(25) Lin, M.-H.; Lin, W.-C.; Liu, H.-J.; Chang, T.-H. J. Org. Chem. 2013,
78, 1278.
(26) Lin, M.-H.; Hung, S.-F.; Lin, L.-Z.; Tsai, W.-S.; Chang, T.-H. Org.
Lett. 2011, 13, 332.
(27) Chan, T. H.; Yang, Y.; Li, C. J. J. Org. Chem. 1999, 64, 4452.
(28) Li, J.; Lv, W.; Huang, D.; Wang, K.-H.; Niu, T.; Su, Y.; Hu, Y. Appl.
Organomet. Chem. 2014, 28, 286.
We are thankful for financial support from the National Natural Sci-
ence Foundation of China (Grant No. 21462037), Key Laboratory Poly-
mer Materials of Gansu Province (Northwest Normal University),
Bioactive Products Engineering Research Center for Gansu Distinctive
Plants, and State Key Laboratory of Applied Organic Chemistry, Lan-
zhou University.
(29) (a) Sugiura, M.; Kobayashi, S. Angew. Chem. Int. Ed. 2005, 44,
5176. (b) Friestad, G. K. Eur. J. Org. Chem. 2005, 3157.
(30) Lu, A.; Wang, F.; Huang, D.; Wang, K.; Su, Y.; Xü, Y.; Hu, Y. Chin. J.
Org. Chem 2014, 34, 948; (in Chinese).
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Synlett 1999, 138. (c) Kobayashi, S.; Hamada, H.; Manabe, K.
Synlett 2001, 1140.
Supporting Information
Supporting information for this article is available online at
http://dx.doi.org/10.1055/s-0035-1560803.
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© Georg Thieme Verlag Stuttgart · New York — Synthesis 2016, 48, 293–301