A hydrate salt-promoted reductive coupling reaction of nitrodienes with unactivated alkenes

Article abstract of DOI:10.1039/C9OB00136K

Transition metal-catalyzed reductive coupling has emerged as a powerful method for the construction of C-C bonds. Herein, a crystalline hydrate, Na₂HPO₄·7H₂O, has been disclosed as an effective promoter for the reductive c

Full text of DOI:10.1039/C9OB00136K

Organic &
Biomolecular Chemistry
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A hydrate salt-promoted reductive coupling
reaction of nitrodienes with unactivated alkenes†
Cite this: Org. Biomol. Chem., 2019,
7, 2258
1
a
a
a
a
a,b
Mengmeng Zhang, Liming Yang, Chao Tian, Meng Zhou, Guanghui An
*
and
a
Guangming Li
*
Transition metal-catalyzed reductive coupling has emerged as a powerful method for the construction of
C–C bonds. Herein, a crystalline hydrate, Na HPO ·7H O, has been disclosed as an effective promoter for
the reductive coupling of nitrodienes with unactivated alkenes to afford diverse dienes with various func-
tionalities in an open-flask manner. The mechanism study has revealed that Na HPO ·7H O accelerates
the in situ generation of active silane PhSi(OEt)H and prevents the deactivation of catalyst. The approach
can increase the efficiency of previous reductive coupling reactions as well.
2
4
2
Received 18th January 2019,
Accepted 30th January 2019
2
4
2
DOI: 10.1039/c9ob00136k
2
rsc.li/obc
organometallic catalysts still remains highly desirable.
Herein, we report an inexpensive crystalline hydrate promoted
Introduction
The transition metal-catalyzed reductive cross coupling of Fe(acac) -catalyzed reductive coupling reaction via in situ
3
unactivated alkenes has emerged as a powerful and distinct generation of reactive silanes (Scheme 1).
method for the facile construction of C–C bonds that allows
1
divergent functionalization. These transformations revealed
that unactivated alkenes could be converted to a nucleophilic
radical species via an initial hydrogen atom transfer (HAT)
Results and discussion
from a transition metal hydride to an olefin, which is then Baran demonstrated that ethoxy(phenyl)silane PhSi(OEt)H2
trapped by a suitable electrophile. They also provide rapid would be the most effective silane species for the hydrogen
3
access to many compounds that were difficult or impossible to transfer process in the coupling reactions. The isolation of
access using other methods. Baran et al. have reported recently PhSi(OEt)H was not successful due to the moisture sensitivity
2
5
practical methods for olefin cross-coupling and hydromethyl- of this adduct according to Shenvi’s report. Thus, the in situ
ation of unactivated alkenes with subsequent discovery of a formed active silane would promote the reactivity of the HAT
2
versatile sulfone acceptor for homologation and a Minisci-type process. According to the literature, Na HPO and its crystal
2
4
3
functionalization. Shenvi disclosed a branch selective hydro- hydrates would potentially benefit the solvolysis of silanes in
4
12
arylation of olefins via iodoarenes. To elevate the efficiency in alcohol solvents. Hence, we commenced our investigation
manganese and iron-catalyzed reactions, Shenvi et al. revealed using the reductive cross-coupling reaction of nitrodiene 1 and
isopropoxy(phenyl)silane (Ph(i-PrO)SiH ) as an efficient reduc- styrene as a model reaction and Na HPO as an additive. This
2
2
4
5
tant. An alternative improvement has been disclosed by a process would afford important synthetic targets, conjugated
second-generation set of olefin cross-coupling conditions dienes, which are key structural motifs of many natural pro-
3
13
via addition of styrene from Baran’s group. Despite these ducts and pharmaceuticals and play important roles in
advances,
6
–11
the development of alternative protocols to
prevent catalyst deactivation and other issues problematic for
interfacing the direct radical generation method with existing
a
Key Laboratory of Functional Inorganic Material Chemistry (MOE),
School of Chemistry and Materials Science, Heilongjiang University, No. 74,
Xuefu Road, Nangang District, Harbin 150080, P. R. China.
E-mail: gmli@hlju.edu.cn, chemagh@163.com
b
College of Materials Science and Chemical Engineering,
Harbin Engineering University, Harbin, Heilongjiang 150001, P.R. China
†
Electronic supplementary information (ESI) available. See DOI: 10.1039/
Scheme 1 Strategies for the promotion of reductive cross coupling of
c9ob00136k
unactivated alkenes.
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1
4
15
organic synthesis and materials science. To our delight,
the diene formation process indeed occurred with Na HPO as
2
4
an additive, providing 2 in 48% yield in an open flask manner.
To further improve the reactivity, various catalysts were applied
for the coupling reaction, and Fe(acac) exhibited the highest
3
yields among all catalysts (Table 1, entries 1 and 2, and
1
1b
2c
Table S1,† entries 1–7). Ni(acac)
Table S1,† entries 4 and 5), which have been used previously,
afforded lower reactivity. The reaction was less efficient with
other silane reductants than PhSiH (Table 1, entry 1 vs.
entries 8–11). Further experiments on Na HPO and its crystal
2
and Fe(dibm)
3
(
3
2
4
2 4 2
hydrates revealed that Na HPO ·7H O could significantly
enhance the yield (Table 1, entry 9). A remarkable difference
was observed when the reaction was carried out in the
absence of Na
Na HPO ·7H O. The subsequent thorough survey of other
hydrates and inorganic bases didn’t improve the reactivity.
Notably, Na HPO ·12H O afforded a similar efficiency to that
of Na HPO ·7H O (Table 1, entry 10). To verify the role of
water, replacement of Na HPO 7H O with a combination of Scheme 2 Scope of reductive cross-coupling reactions.
2 4 2
HPO ·7H O, indicating the crucial role of
2
4
2
2
4
2
2
4
2
2
4
2
Na
that water in the crystalline hydrate prompted the reaction
Table 1, entry 11). Increasing the reaction temperature or
introducing the inert gas didn’t enhance the reaction yields The steric effect of styrene had a crucial impact on the reaction
Table S1,† entries 23 and 24). Extension of the reaction time yield, e.g. the yield of 2e was lower than those of 2f and 2g. The
resulted in the formation of by-products (Table S1,† entry 25).
cyclic styrene derivative indene also gave the product 2j under
To examine the substrate scope of this diene synthesis, the reaction conditions in a satisfactory yield.
2 4
HPO and water sharply reduced the reactivity, implying
(
(
various nitrodienes were explored under the optimal reaction
Encouraged by these results, the styrene derivative was
conditions (Scheme 2A). Both electron-donating and electron- extended to other alkenes (Scheme 2C and D). Both acyclic
withdrawing groups were tolerated in good yields. The nitro and cyclic alkenes can undergo the reaction smoothly with
group, which would be susceptible to reduction under reported reasonable yields (2k–2p). Notably, the quaternary carbon
3
conditions, was also tolerated, affording 2b in 69% yield. center can be readily assembled with good yield of 2o (81%).
γ-Alkyl nitrodienes were also viable substrates with good yields The bicyclic alkenes borbornenes could be also converted to
(
2d). Further investigation on diverse styrene derivatives was 2p, which is difficult to achieve with conventional methods. In
carried out under the optimal reaction conditions (Scheme 2B). addition to the above simple alkenes, functionalized alkenes
were also employed as substrates for the reductive coupling
reactions (Scheme 2E). The hydroxyl group, silane and silyl
ether were tolerated under the optimal conditions (2q–2u).
a
Table 1 Optimization experiments
Surprisingly, a substrate with a carbonyl group, a potential
reductive site, also successfully affords the desired product in a
satisfactory yield (2v). However, cinnamic acid didn’t undergo
this reductive cross-coupling reaction with nitrodiene 1a.
To better understand the protocol, a series of investigations
b
Entry
Catalyst
Fe(acac)
Reductant
Additive
Yield (%)
was conducted for the proposal of a mechanism. The addition
of a radical scavenger, TEMPO, effectively inhibits the reaction,
indicating a radical-mediated reaction pathway. In comparison
with additive-free conditions, the reaction released hydrogen
1
2
3
4
5
6
7
8
9
3
PhSiH
PhSiH
3
Na
2
Na
2
Na
2
Na
2
Na
2
Na
2
—
HPO
HPO
HPO
HPO
HPO
HPO
4
4
4
4
4
4
48
39
34
N.R.
N.R.
43
29
62
Fe(dibm)
3
3
Fe(acac)
Fe(acac)
Fe(acac)
Fe(acac)
Fe(acac)
Fe(acac)
Fe(acac)
Fe(acac)
Fe(acac)
3
3
3
3
3
3
3
3
3
(EtO)
Et SiH
Ph SiH
3
SiH
3
3
2 4 2
immediately upon the addition of Na HPO ·7H O. According
PMHS
PhSiH
PhSiH
PhSiH
PhSiH
PhSiH
12
to the previous report and our results, we rationalized that
3
3
3
3
3
Na
2
Na
2
Na
2
Na
2
HPO
HPO
HPO
HPO
4
·2H
4
·7H
4
4
2
O
O
Na HPO ·7H O accelerates the in situ generation of the active
2
4
2
2
89
83
12
2
silane PhSi(OEt)H and acts as a buffering agent to promote
the stability of silane and prevent the deactivation of catalyst.
Further investigation on generating PhSi(OEt)H2 during the
reaction revealed that the addition of Na HPO ·7H O signifi-
2 4 2
cantly accelerated the rate of active silane generation compared
10
1
·12H
·7H
2
O
1
2
O
a
Reaction conditions: 1 (0.2 mmol, 1 equiv.), styrene (2 equiv.), catalyst
30 mol%), reductant (2 equiv.) and additive (2 equiv.) were added to
mL of EtOH under air at 40 °C for 2 h. Isolated yields are given.
(
2
b
N.R. = No reaction.
with the Na HPO and additive free situation (Scheme S1d†).
2
4
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Moreover, the TG-DSC investigation of the solid additive
before and after the reaction revealed that the release of 6
water molecules per Na
reaction, which might promote the formation of PhSi(OEt)H
Scheme S1a–c†). Therefore, a mechanism was proposed as
shown in Scheme 3. Na HPO ·7H O mediated the rapid con-
version of PhSiH into PhSi(OEt)H , which will undergo hydro-
2 4 2
HPO ·7H O formula occurs during the
2
(
2
4
2
3
2
III
gen atom transfer (HAT), affording Fe complex (A). The
resulting intermediate A undergoes dissociation to afford
III
2
active catalyst species L Fe ·H (C), which adds hydrogen to
alkene (3), generating radical D. D is trapped by nitroalkene (1)
to generate the β-nitro radical E. The sequential fragmentation
of E would furnish the alkylated dienes (2) and a nitro radical,
III
which would reoxidize F to form Fe species, completing the
catalytic cycle.
Intrigued by the results, we envisioned that our protocol
might be a general improvement of various types of reductive
cross-coupling reactions and could be extended to the Fe-cata- Scheme 4 Literature comparison. Repeated results under the con-
lyzed reductive coupling of unactivated alkenes with ditions of ref. 16 and 3.
a
β-nitroalkenes and even catalytic reductive olefin coupling.
Disubstituted and trisubstituted alkenes served as viable
donor substrates with β-nitrostyrenes in an open flask manner
providing tertiary alkylated styrenes in good to excellent yields
Conclusions
(
Scheme 4, 4a–4d). For example, cyclohexene and 1-methyl- In summary, a crystalline hydrate promoted mild Fe(acac)
3
-
cyclohexene exhibit prompt reactivity under optimal con- catalyzed reductive coupling reaction of nitrodienes with unac-
1
6
ditions compared with the literature (4b and 4c). When the tivated alkenes has been developed. The mechanism analysis
more hindered norbornene was applied in this protocol, the revealed that Na HPO ·7H O plays an essential role in acceler-
reaction furnished the endocyclic tethered styrene 4d in a ating the in situ generation of the active silane PhSi(OEt)H and
2
4
2
2
1
6
better yield (of 74%) than 50%. Additionally, unactivated preventing the deactivation of catalyst. Such a protocol can
olefins reacted with α,β-unsaturated alkenes readily under the realize the reductive coupling of nitrodienes with unactivated
optimal conditions, providing increased outcome of the reac- alkenes for the first time. Remarkably, it can be applied not
3
tion (Scheme 4, 4e–4f). Furthermore, to rule out the possi- only to reductive coupling of unactivated alkenes to nitro-
bility of using different sources of catalyst or other reagents, dienes and nitroalkenes but also to olefin coupling reactions
we carried out the literature experiments and obtained a in an open flask other than under air and moisture free con-
3
,16
similar efficiency to Baran and Cui’s report.
ditions. Further extension of this protocol to other reductive
cross coupling reactions is under investigation.
Experimental
Materials and methods
Unless otherwise noted, all reagents were obtained from com-
mercial suppliers and used without further purification. The
reaction product was isolated by column chromatography on a
silica gel (236–400 mesh) column using petroleum ether (PE)
1
13
with a boiling range from 60 to 90 °C and EtOAc. H and
C
NMR spectra were recorded on 400 and 101 MHz NMR spec-
1
6 3
trometers using DMSO-d or CDCl as solvent. In addition, H
1
3
and C NMR spectra were recorded using tetramethylsilane as
the internal standard. Chemical shifts are reported in ppm
relative to the solvent signal. Multiplicity is indicated as
follows: s (singlet); d (doublet); t (triplet); q (quartet); m (multi-
plet); dd (doublet of doublets). HRMS were conducted using
an Agilent 6540 Q-TOF LC/MS equipped with an electrospray
ionization (ESI) probe operating in positive ion mode.
Thermogravimetric analyses (TG-DSC) were performed at
Scheme 3 The proposed mechanism.
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3
0–800 °C at heating rate of 10 °C min−1 using a PerkinElmer 15.6 Hz, 1H), 6.23 (ddd, J = 15.2, 10.3, 1.4 Hz, 1H), 6.00 (dd, J =
STA 6000 instrument. GC-MS were performed using an Agilent 15.2, 6.8 Hz, 1H), 3.58 (p, J = 7.0 Hz, 1H), 1.43 (d, J = 7.0 Hz,
1
3
6
890/5973 N GC. Unless otherwise noted, all reagents were 3H). C NMR (101 MHz, DMSO-d
6
) δ 145.9, 140.5, 137.6,
weighed and handled in air, and all reactions were carried out 131.2, 129.6, 129.4, 129.1, 128.9, 127.7, 127.5, 126.6, 126.5,
+
in air.
42.3, 21.6. HRMS (ESI) m/z: 235.1478 [M + H] ; Calcd for
+
C
18
H
19 : 235.1481.
General procedure for the synthesis of compounds 2a–2v
1
-Nitro-2-((1E,3E)-5-phenylhexa-1,3-dien-1-yl)benzene (2b).
A Schlenk tube containing nitrodiene (0.2 mmol, 1 equiv.), Colorless oil; 38.5 mg, 69% yield; R = 0.39 (petroleum ether);
f
1
alkene (0.4 mmol, 2 equiv.), Fe(acac)
(
(
3
(30 mol%), and PhSiH
2 equiv.) in EtOH (2 mL) was taken. Then, Na HPO ·7H
2 equiv.) was added as an additive. The solution was kept at 1H), 6.91–6.83 (m, 3H), 6.31 (dd, J = 15.2, 8.4 Hz, 1H), 6.02 (dd,
0 °C for 2 h. Then the solution was diluted and filtered J = 15.2, 6.8 Hz, 1H), 3.62 (p, J = 6.8 Hz, 1H), 1.46 (d, J =
3
H NMR (400 MHz, CDCl
3
) δ 7.48 (dd, J = 7.7, 1.5 Hz, 1H),
2
4
2
O
7.38–7.32 (m, 2H), 7.31–7.19 (m, 4H), 6.95 (td, J = 7.5, 1.1 Hz,
4
1
3
3
through Celite. The solvent was evaporated under vacuum. The 7.0 Hz, 3H). C NMR (101 MHz, CDCl ) δ 156.7, 145.8, 139.3,
purification was performed by flash column chromatography 130.0, 129.9, 128.5, 128.3, 127.4, 126.6, 126.3, 126.2, 125.8,
+
on silica gel using petroleum ether (for 2a–2p, 2t and 4b–4e) 120.7, 110.9, 42.5, 21.2. HRMS (ESI) m/z: 280.1328 [M + H] ;
+
or petroleum ether/EtOAc (9 : 1 to 2 : 1) (for 2q–2s, 2v–2u, 4a Calcd for C18
H
18NO
2
: 280.1332.
and 4f) as eluent to give the pure products.
1-Fluoro-4-((1E,3E)-5-phenylhexa-1,3-dien-1-yl)benzene (2c).
Colorless oil; 46.8 mg, 88% yield; R = 0.41 (petroleum ether);
) δ 7.35–7.29 (m, 4H), 7.27–7.19 (m,
f
General procedure for the synthesis of compounds 4a–4d
1
H NMR (400 MHz, CDCl
3
A Schlenk tube containing β-nitrostyrene (0.2 mmol, 1 equiv.), 3H), 6.99 (t, J = 8.7 Hz, 2H), 6.68 (dd, J = 15.7, 10.3 Hz, 1H),
alkene (0.4 mmol, 2 equiv.), Fe(acac)
3
(30 mol%), and PhSiH
3
6.45 (d, J = 15.7 Hz, 1H), 6.21 (dd, J = 15.3, 10.3 Hz, 1H), 6.00
(
(
2 equiv.) in EtOH (2 mL) was taken. Then, Na HPO ·7H O
2 equiv.) was added as an additive. The solution was kept at 7.0 Hz, 3H). C NMR (101 MHz, CDCl ) δ 162.1 (d, J =
2
4
2
(dd, J = 15.2, 6.8 Hz, 1H), 3.58 (p, J = 7.0 Hz, 1H), 1.43 (d, J =
1
3
3
4
0 °C for 2 h. Then the solution was diluted and filtered 246.8 Hz), 145.6, 139.9, 133.7 (d, J = 3.4 Hz), 129.7, 128.9 (d, J =
through Celite. The solvent was evaporated under vacuum. The 2.5 Hz), 128.5, 127.6 (d, J = 7.8 Hz), 127.3, 126.3, 115.6, 115.4,
+
purification was performed by flash column chromatography 42.5, 21.2. HRMS (ESI) m/z: 253.1389 [M + H] ; Calcd for
1
8 +
on silica gel using petroleum ether (for 4b–4d) or petroleum
ether/EtOAc (9 : 1 to 2 : 1) (for 4a) as eluent to give the pure
products.
C
18H F : 253.1387.
((1E,3E)-2-Methylhexa-1,3-diene-1,5-diyl)dibenzene
Colorless oil; 40.7 mg, 82% yield; R = 0.52 (petroleum ether);
H NMR (400 MHz, CDCl
H), 6.43 (d, J = 32.1 Hz, 1H), 6.28 (d, J = 15.6 Hz, 1H), 5.98
(2d).
f
1
3
) δ 7.36–7.27 (m, 6H), 7.25–7.14 (m,
General procedure for the synthesis of compound 4e
4
A Schlenk tube containing styrene (0.2 mmol, 1 equiv.), methyl (ddd, J = 20.6, 15.6, 7.1 Hz, 1H), 3.58 (dp, J = 20.8, 7.0 Hz, 1H),
1
3
vinyl ketone (0.6 mmol, 3 equiv.), Fe(acac)
PhSiH (2 equiv.) in EtOH (1 mL) was taken. Then, (101 MHz, CDCl
Na HPO ·7H O (2 equiv.) was added as an additive. The solu- 129.2, 128.5, 128.1, 127.3, 126.4, 126.2, 42.7, 21.5, 14.1. HRMS
3
(30 mol%), and 1.99 (t, J = 2.1 Hz, 3H), 1.42 (dd, J = 23.2, 7.0 Hz, 3H). C NMR
3
3
) δ 146.0, 135.8, 134.7, 133.9, 130.2, 129.4,
2
4
2
+
+
tion was kept at 40 °C for 2 h. Then the solution was diluted (ESI) m/z: 249.1634 [M + H] ; Calcd for C19
and filtered through Celite. The solvent was evaporated under 1-Chloro-2-((3E,5E)-6-phenylhexa-3,5-dien-2-yl)benzene (2e).
vacuum. The purification was performed by flash column Colorless oil; 40.0 mg, 75% yield; R = 0.70 (petroleum ether);
chromatography on silica gel using petroleum ether as eluent
to give the pure product.
H21 : 249.1638.
f
1
3
H NMR (400 MHz, CDCl ) δ 7.40–7.33 (m, 3H), 7.34–7.25 (m,
3H), 7.26–7.10 (m, 3H), 6.78 (dd, J = 15.7, 10.4 Hz, 1H), 6.50 (d,
J = 15.6 Hz, 1H), 6.26 (dd, J = 15.3, 10.3 Hz, 1H), 5.98 (dd, J =
General procedure for the synthesis of compound 4f
1
5.3, 6.3 Hz, 1H), 4.12 (p, J = 6.8 Hz, 1H), 1.41 (d, J = 6.9 Hz,
1
3
A Schlenk tube containing tert-butyl 4-methylenepiperidine-1- 3H). C NMR (101 MHz, CDCl
3
) δ 142.9, 138.0, 137.5, 133.5,
carboxylate (0.2 mmol, equiv.), methyl vinyl ketone 131.2, 129.8, 129.6, 129.0, 128.6, 128.2, 127.4, 127.3, 127.0,
1
+
(
(
(
0.6 mmol, 3 equiv.), Fe(acac)
2 equiv.) in EtOH (1 mL) was taken. Then, Na
2 equiv.) was added as an additive. The solution was kept at
0 °C for 2 h. Then the solution was diluted and filtered Colorless oil; 42.2 mg, 83% yield; R
3
(30 mol%), and PhSiH
3
126.2, 38.3, 19.9. HRMS (ESI) m/z: 269.1088 [M + H] ; Calcd for
+
2
HPO ·7H
4
2
O
C
18
H
18Cl : 269.1092.
1-Chloro-3-((3E,5E)-6-phenylhexa-3,5-dien-2-yl)benzene (2f).
= 0.40 (petroleum ether);
3
H NMR (400 MHz, CDCl ) δ 7.37 (d, J = 7.1 Hz, 2H), 7.30 (t, J =
4
f
1
through Celite. The solvent was evaporated under vacuum. The
purification was performed by flash column chromatography 7.6 Hz, 2H), 7.26–7.16 (m, 4H), 7.12 (dd, J = 7.5, 1.6 Hz, 1H),
on silica gel using petroleum ether/EtOAc (9 : 1 to 2 : 1) as 6.77 (dd, J = 15.7, 10.4 Hz, 1H), 6.50 (d, J = 15.7 Hz, 1H), 6.23
eluent to give the pure product.
(dd, J = 15.3, 10.4 Hz, 1H), 5.94 (dd, J = 15.2, 6.9 Hz, 1H), 3.56
13
((1E,3E)-Hexa-1,3-diene-1,5-diyl)dibenzene (2a). Colorless (p, J = 6.9 Hz, 1H), 1.41 (d, J = 7.0 Hz, 3H). C NMR (101 MHz,
1
f 3
oil; 41.7 mg, 89% yield; R = 0.69 (petroleum ether); H NMR CDCl ) δ 147.7, 138.7, 137.4, 134.3, 131.5, 129.8, 129.7, 128.9,
(
7
400 MHz, CDCl
3
) δ 7.40–7.34 (m, 2H), 7.34–7.25 (m, 4H), 128.6, 127.5, 127.4, 126.4, 126.3, 125.6, 42.2, 21.1. HRMS (ESI)
+
+
.27–7.15 (m, 4H), 6.77 (dd, J = 15.7, 10.3 Hz, 1H), 6.48 (d, J = m/z: 269.1088 [M + H] ; Calcd for C H Cl : 269.1092.
1
8
18
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1
3
1
-Chloro-4-((3E,5E)-6-phenylhexa-3,5-dien-2-yl)benzene (2g). 1.03 (d, J = 6.7 Hz, 3H), 0.91–0.85 (m, 3H). C NMR (101 MHz,
Colorless oil; 43.7 mg, 86% yield; R = 0.40 (petroleum ether); DMSO-d ) δ 141.9, 137.7, 130.4, 129.9, 129.2, 129.1, 127.6,
f
6
1
H NMR (400 MHz, CDCl
H), 7.25–7.13 (m, 3H), 6.76 (dd, J = 15.7, 10.3 Hz, 1H), 6.49 (d, [M + H] ; Calcd for C18
J = 15.7 Hz, 1H), 6.25–6.15 (m, 1H), 5.94 (dd, J = 15.2, 6.7 Hz, ((1E,3E)-5-Methylpentadeca-1,3-dien-1-yl)benzene
H), 3.56 (p, J = 6.9 Hz, 1H), 1.40 (d, J = 7.0 Hz, 3H). C NMR Colorless oil; 45.3 mg, 76% yield; R = 0.77 (petroleum ether);
) δ 7.41 (d, J = 7.3 Hz, 2H), 7.30
28.9, 128.7, 128.6, 128.6, 127.4, 126.2, 41.9, 21.1. HRMS (ESI) (m, J = 9.5, 5.7 Hz, 2H), 7.19 (t, J = 7.3 Hz, 1H), 6.88–6.78 (m,
3
) δ 7.40–7.33 (m, 2H), 7.34–7.24 (m, 126.5, 29.3, 27.3, 22.6, 20.9, 14.4. HRMS (ESI) m/z: 243.2109
+
+
4
H27 : 243.2107.
(2m).
1
3
1
f
1
(101 MHz, CDCl
3
) δ 144.1, 139.1, 137.4, 131.9, 131.3, 129.6,
H NMR (400 MHz, DMSO-d
6
1
+
+
m/z: 269.1088 [M + H] ; Calcd for C18
-Bromo-4-((3E,5E)-6-phenylhexa-3,5-dien-2-yl)benzene (2h). (dd, J = 15.3, 7.8 Hz, 1H), 2.19 (m, J = 13.7, 6.8 Hz, 1H), 1.22 (s,
Colorless oil; 50.7 mg, 85% yield; R = 0.39 (petroleum ether); 16H), 1.00–0.94 (m, 3H), 0.89 (m, J = 14.9, 7.4 Hz, 2H), 0.83 (t,
H
18Cl : 269.1092.
1H), 6.51–6.45 (m, 1H), 6.17 (dd, J = 15.2, 10.4 Hz, 1H), 5.74
1
f
1
13
3 6
H NMR (400 MHz, CDCl ) δ 7.44–7.41 (m, 2H), 7.39–7.34 (m, J = 6.7 Hz, 3H). C NMR (101 MHz, DMSO-d ) δ 142.0, 137.7,
2
2
6
3
H), 7.30 (t, J = 7.7 Hz, 2H), 7.22–7.17 (m, 1H), 7.14–7.08 (m, 132.0, 130.4, 129.9, 129.1, 127.6, 126.5, 37.0, 36.8, 31.8, 30.5,
H), 6.75 (dd, J = 15.7, 10.4 Hz, 1H), 6.49 (d, J = 15.7 Hz, 1H), 29.6, 29.5, 29.2, 27.3, 22.6, 20.9, 19.1, 14.4. HRMS (ESI) m/z:
+
+
.20 (dd, J = 15.2, 10.4 Hz, 1H), 5.93 (dd, J = 15.2, 6.7 Hz, 1H), 299.2730 [M + H] ; Calcd for C22
.54 (p, J = 6.9 Hz, 1H), 1.39 (d, J = 7.0 Hz, 3H). C NMR
H
35 : 299.2733.
13
((1E,3E)-4-Cyclohexylbuta-1,3-dien-1-yl)benzene (2n). Colorless
1
(101 MHz, CDCl ) δ 144.6, 139.0, 137.4, 131.6, 131.4, 129.6, oil; 34.0 mg, 80% yield; R = 0.77 (petroleum ether); H NMR
3
f
1
29.1, 128.9, 128.6, 127.4, 126.2, 120.0, 41.9, 21.1. HRMS (ESI) (400 MHz, CDCl
3
) δ 7.40–7.34 (m, 2H), 7.32–7.27 (m, 2H),
+
+
m/z: 313.0582 [M + H] ; Calcd for C18
-Methyl-4-((3E,5E)-6-phenylhexa-3,5-dien-2-yl)benzene (2i). 15.7 Hz, 1H), 6.17 (dd, J = 15.3, 10.4 Hz, 1H), 5.78 (dd, J = 15.3,
Colorless oil; 41.7 mg, 89% yield; R = 0.57 (petroleum ether); 6.9 Hz, 1H), 2.06 (dd, J = 12.0, 4.0 Hz, 1H), 1.74 (d, J = 9.4 Hz,
) δ 7.38 (d, J = 7.3 Hz, 2H), 7.31 (t, J = 4H), 1.66 (d, J = 12.7 Hz, 1H), 1.35–1.21 (m, 3H), 1.15 (ddd, J =
H
18Br : 313.0586.
7.22–7.16 (m, 1H), 6.74 (dd, J = 15.6, 10.4 Hz, 1H), 6.45 (d, J =
1
f
1
H NMR (400 MHz, CDCl
3
13
7
1
1
2
.6 Hz, 2H), 7.22 (d, J = 7.2 Hz, 1H), 7.15 (s, 4H), 6.79 (dd, J = 20.7, 10.3, 4.4 Hz, 2H). C NMR (101 MHz, CDCl ) δ 141.7, 137.8,
5.6, 10.3 Hz, 1H), 6.50 (d, J = 15.7 Hz, 1H), 6.24 (dd, J = 15.2, 130.0, 129.9, 128.5, 127.9, 127.0, 126.1, 40.9, 32.9, 26.2, 26.0.
0.4 Hz, 1H), 6.00 (dd, J = 15.2, 6.8 Hz, 1H), 3.62–3.52 (m, 1H), HRMS (ESI) m/z: 213.1635 [M + H] ; Calcd for C16
.35 (s, 3H), 1.43 (d, J = 7.0 Hz, 3H). C NMR (101 MHz,
3
+
+
H
21 : 213.1638.
((1E,3E)-4-(1-Methylcyclohexyl)buta-1,3-dien-1-yl)benzene (2o).
) δ 142.6, 140.2, 137.6, 135.7, 130.8, 129.3, 129.2, 129.0, Colorless oil; 36.7 mg, 81% yield; R = 0.65 (petroleum ether);
) δ 7.38 (d, J = 7.4 Hz, 2H), 7.30 (t, J =
7.6 Hz, 2H), 7.20 (t, J = 7.3 Hz, 1H), 6.79 (dd, J = 15.6, 10.3 Hz,
-((1E,3E)-4-Phenylbuta-1,3-dien-1-yl)-2,3-dihydro-1H-indene 1H), 6.48 (d, J = 15.7 Hz, 1H), 6.18 (dd, J = 15.6, 10.3 Hz, 1H),
1
3
CDCl
3
f
1
1
28.6, 127.2, 127.2, 126.2, 42.0, 21.2, 21.0. HRMS (ESI) m/z:
H NMR (400 MHz, CDCl
3
+
+
2
49.1634 [M + H] ; Calcd for C H : 249.1638.
1
9
21
1
1
3
(2j). Colorless oil; 35.9 mg, 73% yield; R
f
= 0.50 (petroleum 5.83 (d, J = 15.6 Hz, 1H), 1.56–1.33 (m, 10H), 1.04 (s, 3H).
C
1
ether); H NMR (400 MHz, CDCl ) δ 7.40 (d, J = 7.3 Hz, 2H), NMR (101 MHz, CDCl ) δ 146.1, 137.8, 130.2, 129.9, 128.5,
3
3
7
1
1
1
8
1
1
.32 (t, J = 7.6 Hz, 2H), 7.26–7.14 (m, 5H), 6.82 (dd, J = 15.7, 127.0, 126.8, 126.1, 38.0, 36.3, 27.6, 26.3, 22.5. HRMS (ESI) m/
+
+
0.4 Hz, 1H), 6.53 (d, J = 15.7 Hz, 1H), 6.36 (dd, J = 15.0, z: 227.1792 [M + H] ; Calcd for C17
0.4 Hz, 1H), 5.88 (dd, J = 15.1, 8.6 Hz, 1H), 3.87 (q, J = 8.2 Hz, 2-((1E,3E)-4-Phenylbuta-1,3-dien-1-yl)bicyclo[2.2.1]heptane
H), 2.99–2.85 (m, 2H), 2.44–2.34 (m, 1H), 1.90 (dq, J = 12.5, (2p). Colorless oil; 30.9 mg, 69% yield; R = 0.57 (petroleum
) δ 7.42–7.35 (m, 2H), 7.30 (d,
H23 : 227.1794.
f
1
3
1
3 3
.7 Hz, 1H). C NMR (101 MHz, CDCl ) δ 145.8, 143.9, 137.7, ether); H NMR (400 MHz, CDCl
37.5, 131.0, 130.9, 129.0, 128.6, 127.3, 126.7, 126.3, 126.2, J = 7.6 Hz, 2H), 7.18 (t, J = 7.4 Hz, 1H), 6.73 (dd, J = 15.7,
24.5, 124.5, 49.0, 33.6, 31.7. HRMS (ESI) m/z: 247.1479 10.3 Hz, 1H), 6.43 (d, J = 15.7 Hz, 1H), 6.13 (dd, J = 15.1,
+
+
[M + H] ; Calcd for C19
H
19 : 247.1481.
10.3 Hz, 1H), 5.74 (dd, J = 15.1, 8.1 Hz, 1H), 2.26 (s, 1H), 2.19
((1E,3E)-5-Methylhepta-1,3-diene-1,7-diyl)dibenzene
(2k). (q, J = 7.9 Hz, 1H), 2.11–2.04 (m, 1H), 1.50 (s, 2H), 1.39 (d, J =
Colorless oil; 39.3 mg, 75% yield; R
H NMR (400 MHz, CDCl ) δ 7.40–7.37 (m, 2H), 7.33–7.27 (m, J = 10.3 Hz, 1H). C NMR (101 MHz, DMSO-d ) δ 141.5, 137.7,
3 6
f
= 0.70 (petroleum ether); 9.9 Hz, 1H), 1.35–1.21 (m, 3H), 1.19 (d, J = 7.5 Hz, 1H), 1.14 (d,
1
13
4
1
5
H), 7.19 (qd, J = 7.4, 3.4 Hz, 5H), 6.77 (dd, J = 15.6, 10.4 Hz, 130.4, 129.9, 129.1, 128.6, 127.6, 126.4, 45.1, 42.7, 37.8, 36.5,
+
H), 6.47 (d, J = 15.6 Hz, 1H), 6.21 (dd, J = 15.2, 10.4 Hz, 1H), 35.9, 29.7, 29.0. HRMS (ESI) m/z: 225.1634 [M + H] ; Calcd for
+
.75 (dd, J = 15.2, 8.0 Hz, 1H), 2.68–2.56 (m, 2H), 2.28 (p, J = 7.1
C
17
H
21 : 225.1638.
1
3
Hz, 1H), 1.71–1.63 (m, 2H), 1.08 (d, J = 6.7 Hz, 3H). C NMR
101 MHz, DMSO-d ) δ 142.7, 141.5, 137.7, 130.6, 129.9, 129.6, oil; 32.7 mg, 81% yield; R
29.1, 128.8, 128.7, 127.7, 126.5, 126.1, 38.8, 36.4, 33.5, 20.8.
(3E,5E)-2,2-Dimethyl-6-phenylhexa-3,5-dien-1-ol (2q). Yellow
= 0.28 (EtOAc/petroleum ether 1 : 5);
H NMR (400 MHz, DMSO-d ) δ 7.41 (d, J = 7.3 Hz, 2H), 7.29 (t,
HRMS (ESI) m/z: 263.1792 [M + H] ; Calcd for C H : 263.1794. J = 7.6 Hz, 2H), 7.21–7.15 (m, 1H), 6.83 (dd, J = 15.7, 10.3 Hz,
(
1
6
f
1
6
+
+
23
2
0
(
(1E,3E)-5-Methylundeca-1,3-dien-1-yl)benzene (2l). Colorless 1H), 6.50 (d, J = 15.7 Hz, 1H), 6.16 (dd, J = 15.6, 10.3 Hz, 1H),
1
f
oil; 37.8 mg, 78% yield; R = 0.73 (petroleum ether); H NMR 5.87 (d, J = 15.6 Hz, 1H), 4.60 (t, J = 5.5 Hz, 1H), 3.17 (d, J =
400 MHz, CDCl ) δ 7.40–7.34 (m, 2H), 7.32–7.27 (m, 2H), 5.6 Hz, 2H), 0.95 (d, J = 11.4 Hz, 6H). C NMR (101 MHz,
1
3
(
3
7
1
7
6
.21–7.15 (m, 1H), 6.75 (dd, J = 15.6, 10.4 Hz, 1H), 6.45 (d, J = DMSO-d ) δ 144.0, 137.8, 130.6, 130.3, 129.1, 127.7, 127.6,
+
5.7 Hz, 1H), 6.16 (dd, J = 15.2, 10.4 Hz, 1H), 5.71 (dd, J = 15.2, 126.5, 70.6, 38.9, 24.5. HRMS (ESI) m/z: 203.1428 [M + H] ;
+
.8 Hz, 1H), 2.20 (q, J = 6.8 Hz, 1H), 1.26 (d, J = 6.5 Hz, 10H), Calcd for C H O : 203.1430.
1
4
19
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(
4E,6E)-3,3-Dimethyl-7-phenylhepta-4,6-dien-1-ol (2r). Yellow 127.29, 126.67, 126.37, 70.75, 38.87, 24.48. HRMS (ESI) m/z:
+
+
oil; 34.2 mg, 79% yield; R = 0.20 (EtOAc/petroleum ether 1 : 5); 177.1272 [M + H] ; Calcd for C H O : 177.1274.
H NMR (400 MHz, DMSO-d
m, 2H), 7.21–7.16 (m, 1H), 6.84 (dd, J = 15.7, 10.2 Hz, 1H), yield; R
f
12 17
1
6
) δ 7.43–7.38 (m, 2H), 7.32–7.27
(E)-(2-Cyclohexylvinyl)benzene (4b). White oil; 25.3 mg, 68%
1
(
f
= 0.7 (petroleum ether); H NMR (400 MHz, DMSO-d
6
)
6
.50 (d, J = 15.7 Hz, 1H), 6.11 (dd, J = 15.5, 10.3 Hz, 1H), 5.84 δ 7.36 (d, J = 7.6 Hz, 2H), 7.28 (t, J = 7.5 Hz, 2H), 7.18 (t, J =
(
4
d, J = 15.5 Hz, 1H), 4.26 (t, J = 5.0 Hz, 1H), 3.38 (td, J = 7.6, 7.2 Hz, 1H), 6.34 (d, J = 16.1 Hz, 1H), 6.23 (dd, J = 16.1, 6.7 Hz,
1
3
.9 Hz, 2H), 1.51 (dd, J = 8.2, 7.0 Hz, 2H), 1.01 (s, 6H).
C
1H), 2.10 (dd, J = 7.1, 3.6 Hz, 1H), 1.73 (t, J = 12.8 Hz, 4H),
NMR (101 MHz, DMSO-d ) δ 145.7, 137.7, 130.6, 130.1, 129.0, 1.66–1.61 (m, 1H), 1.31–1.23 (m, 2H), 1.15 (d, J = 14.1 Hz, 2H),
6
1
3
1
2
27.6, 126.8, 126.5, 58.3, 45.6, 35.6, 27.9. HRMS (ESI) m/z: 0.90 (t, J = 7.4 Hz, 1H). C NMR (101 MHz, DMSO-d
17.1586 [M + H] ; Calcd for C15
6E,8E)-5-Methyl-9-phenylnona-6,8-dien-4-ol (2s). Yellow oil; (ESI) m/z: 187.1481 [M + H] ; Calcd for C H : 187.1481.
6
) δ 137.9,
+
+
H
21O : 217.1587.
136.8, 129.0, 127.5, 127.3, 126.3, 40.9, 32.9, 26.1, 26.0. HRMS
+
+
(
1
4
19
1
3
2.3 mg, 70% yield; R
f
= 0.44 (EtOAc/petroleum ether 1 : 5); H
) δ 7.44–7.39 (m, 2H), 7.29 (td, J = 30.8 mg, 77% yield; R
.9, 3.1 Hz, 2H), 7.21–7.16 (m, 1H), 6.84 (ddt, J = 15.5, 10.5, (400 MHz, CDCl ) δ 7.29 (s, 2H), 7.26 (s, 3H), 6.29 (d, J =
(E)-(2-(1-Methylcyclohexyl)vinyl)benzene (4c). White oil;
1
NMR (400 MHz, DMSO-d
6
f
= 0.72 (petroleum ether); H NMR
7
2
5
3
3
.4 Hz, 1H), 6.47 (dd, J = 15.8, 2.8 Hz, 1H), 6.22–6.12 (m, 1H), 16.3 Hz, 1H), 6.18 (d, J = 16.4 Hz, 1H), 1.60 (dt, J = 12.1, 5.2 Hz,
.85 (tdd, J = 14.5, 9.5, 3.0 Hz, 1H), 4.38 (tt, J = 4.9, 2.2 Hz, 1H), 2H), 1.50 (d, J = 5.7 Hz, 4H), 1.38 (dq, J = 19.0, 5.8 Hz, 4H),
.37–3.25 (m, 1H), 2.28–2.15 (m, 1H), 1.45–1.19 (m, 4H), 0.99 1.06 (s, 3H). C NMR (101 MHz, CDCl ) δ 139.2, 138.9, 129.4,
1
3
3
1
3
(
tt, J = 4.9, 2.5 Hz, 3H), 0.87–0.81 (m, 3H). C NMR (101 MHz, 128.9, 127.2, 127.0, 56.1, 37.1, 30.2, 24.6, 11.7. HRMS (ESI)
+
+
DMSO-d
6
) δ 139.8, 138.8, 137.8, 130.4, 130.3, 129.1, 127.6, m/z: 201.1634 [M + H] ; Calcd for C15
H21 : 201.1638.
1
2
26.5, 73.7, 43.0, 36.9, 19.3, 17.1, 14.6. HRMS (ESI) m/z: 2-((E)-Styryl)bicyclo[2.2.1]heptane (4d). White oil; 29.3 mg,
+
+
1
31.1745 [M + H] ; Calcd for C16
H
23O : 231.1743.
74% yield; R
) δ 7.37 (d, J = 7.2 Hz, 2H), 7.34–7.26 (m, 2H), 7.25–7.18
oil; 50.8 mg, 61% yield; R = 0.20 (petroleum ether); H NMR (m, 1H), 6.34 (d, J = 15.8 Hz, 1H), 6.16 (dd, J = 15.8, 8.0 Hz,
f
= 0.42 (petroleum ether); H NMR (400 MHz,
Triphenyl((3E,5E)-6-phenylhexa-3,5-dien-2-yl)silane (2t). Yellow CDCl
3
1
f
6
(400 MHz, DMSO-d ) δ 7.50–7.42 (m, 10H), 7.41 (d, J = 1.7 Hz, 1H), 2.31 (d, J = 10.2 Hz, 2H), 2.18 (s, 1H), 1.64–1.54 (m, 3H),
1
H), 7.42–7.34 (m, 10H), 6.80–6.69 (m, 1H), 6.30 (dd, J = 14.6, 1.48 (dt, J = 9.7, 2.0 Hz, 1H), 1.42 (ddd, J = 10.6, 6.0, 2.7 Hz,
1
3
3.7 Hz, 1H), 5.70 (dd, J = 20.3, 3.7 Hz, 1H), 1.35 (d, J = 7.8 Hz, 1H), 1H), 1.26 (dq, J = 29.8, 10.5, 9.7 Hz, 3H). C NMR (101 MHz,
13
1.19–0.84 (m, 3H). C NMR (101 MHz, DMSO-d
6
) δ 137.4, 135.9, CDCl
3
) δ 138.1, 136.5, 128.5, 127.3, 126.7, 126.0, 45.5, 42.7,
+
135.6, 135.1, 134.2, 134.1, 130.2, 130.0, 128.5, 128.5, 8.1, 4.6. 38.0, 36.7, 35.9, 29.8, 29.0. HRMS (ESI) m/z: 199.1480 [M + H] ;
+
+
+
HRMS (ESI) m/z: 417.2035 [M + H] ; Calcd for C H Si : 417.2033. Calcd for C H : 199.1481.
30
29
15 19
Trimethyl((1-((1E,3E)-4-phenylbuta-1,3-dien-1-yl)cyclohexyl)
oxy)silane (2u). Yellow oil; 38.4 mg, 64% yield; R = 0.50
5-Phenylhexan-2-one (4e). Yellow oil; 33.1 mg, 94% yield;
1
f
R
f
= 0.40 (petroleum ether); H NMR (400 MHz, CDCl
3
)
1
(EtOAc/petroleum ether 1 : 4); H NMR (400 MHz, CDCl3) δ 7.33–7.26 (m, 2H), 7.20 (m, J = 14.0, 5.5, 4.1 Hz, 3H), 2.69 (m,
δ 7.40 (d, J = 7.4 Hz, 2H), 7.31 (t, J = 7.7 Hz, 2H), 7.20 (t, J = J = 15.8, 10.1, 4.5 Hz, 1H), 2.39–2.22 (m, 2H), 2.06 (s, 3H),
1
3
7
1
6
.3 Hz, 1H), 6.84 (dd, J = 15.5, 9.0 Hz, 1H), 6.53 (d, J = 15.6 Hz, 1.95–1.79 (m, 2H), 1.27 (d, J = 6.9 Hz, 3H). C NMR (101 MHz,
H), 6.34 (d, J = 2.9 Hz, 1H), 5.84 (s, 1H), 2.20 (dd, J = 10.0, CDCl ) δ 208.9, 146.5, 128.5, 127.0, 126.2, 77.4, 77.1, 76.7, 41.8,
3
1
3
+
.0 Hz, 4H), 1.66–1.52 (m, 6H), 0.18 (s, 7H), 0.15 (s, 2H).
C
39.4, 31.9, 29.9, 22.5. HRMS (ESI) m/z: 176.1272 [M + H] ;
+
NMR (101 MHz, CDCl
3
) δ 137.0, 131.0, 130.8, 129.9, 128.6, Calcd for C12
H
17O : 177.1274.
1
3
27.1, 126.1, 125.6, 26.2, 24.5, 22.5, 1.3, 1.0. HRMS (ESI) m/z: tert-Butyl
4-methyl-4-(3-oxobutyl)piperidine-1-carboxylate
+
+
01.1980 [M + H] ; Calcd for C19
5E,7E)-4-Ethyl-8-phenylocta-5,7-dien-1-yl acetate (2v). Yellow roleum ether 1 : 2); H NMR (400 MHz, CDCl
oil; 30.5 mg, 56% yield; R = 0.64 (EtOAc/petroleum ether 1 : 5); 4H), 3.16 (m, J = 13.3, 9.0, 4.0 Hz, 2H), 2.42–2.30 (m, 3H), 2.14
H
29OSi : 301.1982.
(4f). Colorless oil; 45.8 mg, 85% yield; R
f
= 0.47 (EtOAc/pet-
1
(
3
) δ 3.63–3.50 (m,
f
1
H NMR (400 MHz, DMSO-d
.6 Hz, 2H), 7.19 (t, J = 7.3 Hz, 1H), 6.85 (ddd, J = 15.8, 10.4,
.4 Hz, 1H), 6.49 (d, J = 15.7 Hz, 1H), 6.18 (ddd, J = 15.2, 10.4, 36.5, 35.0, 30.9, 30.0, 28.5, 23.0. HRMS (ESI) m/z: 270.2060
6
) δ 7.43–7.40 (m, 2H), 7.29 (t, J = (s, 4H), 1.44 (s, 9H), 1.28 (m, J = 9.1, 4.6 Hz, 2H), 0.89 (s, 3H).
1
3
7
3
3
C NMR (101 MHz, CDCl ) δ 209.0, 155.0, 79.3, 39.7, 37.9,
+
+
1.7 Hz, 1H), 5.60 (ddd, J = 14.8, 9.0, 5.3 Hz, 1H), 4.00–3.89 (m, 2H), [M + H] ; Calcd for C15
3
H28NO : 270.2064.
1
.97 (s, 4H), 1.56–1.37 (m, 2H), 1.25 (dtd, J = 15.8, 9.1, 8.3, 3.2 Hz,
13
2
(
1
H), 1.06–0.91 (m, 2H), 0.83 (dt, J = 11.8, 7.1 Hz, 3H). C NMR
101 MHz, DMSO-d ) δ 170.8, 139.8, 137.7, 131.3, 130.5, 129.7,
29.6, 129.1, 126.5, 64.4, 44.3, 31.1, 28.0, 26.6, 21.2, 12.1. HRMS
6
Conflicts of interest
+
+
(ESI) m/z: 273.1850 [M + H] ; Calcd for C H O : 273.1849.
There are no conflicts to declare.
18 25 2
(E)-2,2-Dimethyl-4-phenylbut-3-en-1-ol (4a). Yellow oil;
3
0.6 mg, 87% yield; R = 0.15 (EtOAc/petroleum ether 1 : 10);
f
1
H NMR (400 MHz, DMSO-d ) δ 7.45–7.33 (m, 2H), 7.33–7.25
6
Acknowledgements
(m, 2H), 7.18 (m, J = 7.3, 3.9, 1.1 Hz, 1H), 6.38–6.23 (m, 2H),
4
6
.58 (t, J = 31.2, 5.4 Hz, 1H), 3.35–3.16 (s, 2H), 1.08–0.83 (m, The authors gratefully acknowledge support from the National
13
H). C NMR (101 MHz, DMSO-d ) δ 138.95, 138.01, 128.94, Natural Science Foundation of China (21502046), the Natural
6
This journal is © The Royal Society of Chemistry 2019
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Science Foundation of Heilongjiang Province (B2016008) and
the University Nursing Program for Young Scholars with
Creative Talents in Heilongjiang Province (UNPYSCT-2017124).
The Fundamental Research Funds for the Central Universities
A. Han, J. M. Abuyuan, L. C. Young, J. R. Norton and
J. H. Palmer, J. Am. Chem. Soc., 2016, 138, 7698–7704.
8 (a) X. Lu, B. Xiao, Z. Zhang, T. Gong, W. Su, J. Yi, Y. Fu and
L. Liu, Nat. Commun., 2016, 7, 11129; (b) X. Ma and
S. B. Herzon, Chem. Sci., 2015, 6, 6250–6255; (c) X. Ma and
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