Rh(I)-catalyzed ring-opening of cyclobutanols via C–C bond activation: Synthesis of cis-olefin with a remote aldehyde

Article abstract of DOI:10.1016/j.tet.2019.130563

A Rh(I)-catalyzed ring-opening of cyclobutanols has been developed with ring opening products bearing cis-olefin and a remote aldehyde. Various substrates bearing different substituted aryl groups, heterocyclic groups and alkyl groups were compatible with

Full text of DOI:10.1016/j.tet.2019.130563

Tetrahedron 75 (2019) 130563
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Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Rh(I)-catalyzed ring-opening of cyclobutanols via CeC bond
activation: Synthesis of cis-olefin with a remote aldehyde
Yu Nie, Jianzhong Chen*, Wanbin Zhang
Shanghai Key Laboratory of Molecular Engineering for Chiral Drugs, School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, 800
Dongchuan Road, Shanghai, 200240, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
A Rh(I)-catalyzed ring-opening of cyclobutanols has been developed with ring opening products bearing
cis-olefin and a remote aldehyde. Various substrates bearing different substituted aryl groups, hetero-
Received 15 July 2019
Received in revised form
20 August 2019
Accepted 23 August 2019
Available online 27 August 2019
cyclic groups and alkyl groups were compatible with the mild reaction conditions. A
pathway was proposed based on the results of preliminary mechanistic studies.
b-C elimination
© 2019 Elsevier Ltd. All rights reserved.
Keywords:
CeC bond activation
Ring-opening
Cyclobutanols
cis-Olefin
Remote aldehyde
1. Introduction
efficient syntheses of these thermodynamically less stable Z-al-
kenes are greatly desired. Previously, the olefin aldehydes were
prepared from a Wittig-reduction or oxidation of the correspond-
ing alcohols, however, the required reagents (for example PPh3,
DIBALH or Dess-Martin Periodinane) are expensive and the pro-
cedures are operationally complex. Generally, these methods pro-
duce a mixture of E and Z products or mainly E isomers. During our
study concerning the metal-catalyzed chemo- and enantioselective
hydrogenation of cyclobutanones [6], we found a highly efficient
rhodium(I)-catalyzed ring-opening of cyclobutanols via a C (sp2)-C
(sp3) bond cleavage, leading to a cis-olefin product bearing a remote
aldehyde (Scheme 1, C). The substrates of the cyclobutanols were
obtained from 10% Ca(OH)2 and 60% NaBH4 with moderate or good
yields via an operationally simple procedure using inexpensive raw
materials. The more important point is that it is an efficient method
for obtaining Z-alkenes with high selectivity via this catalytic
system.
Carbon-carbon single bonds are generally thermodynamically
stable and kinetically inert. However, significant progress has been
made in transition metal catalysis, so much so that numbers of
unique synthetic reactions in which a carbon-carbon single bond is
cleaved in preference to other seemingly more reactive bonds have
increased significantly in the past decades [1]. Cyclobutanols and
cyclobutanones are privileged building blocks in this field [2]. For
example, in 2016, the Song group developed a Pd-catalyzed ring-
opening of 2-alkyenecyclobutanones with arylbornic acids, giving
Z-selective
(Scheme 1 A) [3]. Last year, the Zhang group reported a rhodium(I)-
catalyzed asymmetric [4 2] cycloaddition reaction of 2-
g
,
d
-unsaturated ketones with Z/E ¼ 40/60e99/1
þ
alkylenecyclobutanols with cyclic enones through CeC bond
cleavage, for the efficient synthesis of trans-bicyclic compounds;
however, the intermediates need to be further converted into the
desired products (Scheme 1, B) [4].
cis-Olefin aldehydes and their derivatives are important skele-
tons in numerous bioactive compounds, flavors, pharmaceuticals
and crucial intermediates in organic synthesis [5]. Therefore,
2. Results and discussion
We commenced our study by using 1a as a model substrate for
optimization of the reaction. Initially, the model reaction was car-
ried out in toluene with PPh3 as a ligand, [Rh(COD)Cl]2 as a catalyst
at 110 ꢀC over 12 h. Product 2a was not detected (Table 1, entry 1).
* Corresponding author.
E-mail address: 0091109001@sjtu.edu.cn (J. Chen).
t
When Na2CO3 or BuOK was added as an additive, only a trace
https://doi.org/10.1016/j.tet.2019.130563
0040-4020/© 2019 Elsevier Ltd. All rights reserved.

2
Y. Nie et al. / Tetrahedron 75 (2019) 130563
Table 1
Optimization of reaction conditionsa
Entry
Solvent
Additive
L
Yield (%)b
1
2
3
4
5
6
7
8
Toluene
Toluene
Toluene
Toluene
Toluene
DCM
e
PPh3
PPh3
PPh3
PPh3
e
N.D.
trace
trace
50
9
16
17
21
79
7
67
43
60
11
4
21
trace
11
4
Na2CO3
tBuOK
AgOAc
AgOAc
AgOAc
AgOAc
AgOAc
AgOAc
AgOAc
AgOAc
AgOAc
AgOAc
AgOAc
Ag2CO3
AgOTf
AgBF4
AgNTf
AgF
Scheme 1. Methodologies for ring opening of cyclobutanones and cyclobutanols.
PPh3
PPh3
PPh3
PCy3
P (t-Bu)3
L1
L2
L3
L4
PCy3
PCy3
PCy3
PCy3
PCy3
PCy3
PCy3
PCy3
1,4-dioxane
O-xylene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
amount of 2a was obtained (Table 1, entries 2 and 3). Subsequently,
we found that the use of AgOAc as an additive could give the ring-
opened product with 50% yield (Table 1, entry 4). In the absence of
any ligand, 2a was obtained in only 9% yield (Table 1, entry 5).
However, no further improvement in the yield of 2a was obtained
after the solvent was changed to DCM, 1,4-dioxane or o-xylene
(Table 1, entries 6e8 vs 4). A better yield of 67% could be achieved
by changing the ligand to PCy3 (Table 1, entry 9). Some other
monophosphine ligands were also tested, but PCy3 proved to be the
most effective ligand (Table 1, entries 10e14 vs 9). In view of the
importance of the silver salt, a number of other silver salts were
employed in order to enhance the reaction activity. Disappoint-
ingly, only low yields were obtained when other silver salts, such as
Ag2CO3, AgOTf, AgBF4, AgNTf and AgF, were used in place of AgOAc
(Table 1, entries 15e19 vs 9). Use of [Rh(COD)OH]2 also gave the
corresponding product 2a in 61% yield (Table 1, entry 20). To our
delight, the desired product was obtained in 86% yield by
decreasing the amount of AgOAc to 15 mol % (Table 1, entry 21).
Further decreasing the amount of AgOAc to 10 mol % only produced
2a in 33% yield (Table 1, entry 22).
9
10
11
12
13
14
15
16
17
18
19
20c
21d,e
22f
AgOAc
AgOAc
AgOAc
61
86 (82)
33
a
Reaction conditions: substrate 1a (0.4 mmol, 1.0 equiv.), [Rh(COD)Cl]2
(0.01 mmol, 2.5 mol %), ligand (0.04 mmol, 10 mol %), additive (0.1 mmol, 25 mol %)
in sealed tube with 2 ml solvent at 110 ꢀC for 12 h.
b
Yields were determined by 1H NMR using CH2Br2 as the internal standard.
c
2.5 mol % [Rh(COD)OH]2 was used instead of [Rh(COD)Cl]2.
15 mol % AgOAc.
Number in parenthesis is isolated yield.
10 mol % AgOAc.
d
e
f
With the optimized reaction conditions in hand (Table 1, entry
21), the substrate scope was assessed (Table 2). All the cyclo-
butanols bearing different substituents afforded the desired prod-
ucts in good to excellent yields. Interestingly, when R ¼ aryl, ortho-,
meta-, and para-substituted groups on the benzene ring had almost
no influence on the selectivity and all gave the cis-olefin products
with good yields, albeit higher catalyst loadings were required in
the reactions of some substrates (1b-e, n, s, t). All substrates with
substituents on the benzene ring can be tolerated (2a-p). Firstly,
substrates with different substituents at the 2-position of the aryl
ring were examined, and the desired products were obtained in
good yields (2b-c). Substrates with groups located at the 3-position
provide similar results to those bearing a substituent located at the
4-position (2d-2p). A 2,4,6-trimethyl substituted substrate gave the
best result, providing the corresponding product 2q in 95% yield.
Furthermore, a naphthalene substrate also gave the corresponding
product in high yield (81%, 2r). Heterocyclic cyclobutanols were
also good substrates for this transformation, providing the ring
opened products 2s-u in 61%, 88%, and 94% yields, respectively.
Alkyl substituted cyclobutanol substrates were employed under the
standard conditions, and the corresponding ring opened products
2v-x were obtained in high yields with cis-selectivity. When the
reaction was extended to cyclopentanol and cyclohexanol, no cor-
responding products were obtained [7], suggesting that the strain
of the four-membered ring is required for this ring-opening
reaction.
To demonstrate the potential utility of this protocol in synthesis,
the catalyst system was employed in a gram-scale reaction of model
substrate 1a to give 2a in 80% isolated yield (Scheme 2a). The useful
olefins 3, 4 and 5 were obtained with ease from 2a via reduction,
witting reaction and alkynylation, respectively, in good yields
(Scheme 2a). Some other conversions of 2i were also performed
(Scheme 2b). Product 2i reacted with PhMgBr to produce unsatu-
rated alcohol 6 in 90% yield, which could be transformed to cyclic
ethers 7 [8] and 8 [9], according to literature methods. Further-
more, 6 could be oxidized with Cr3O to provide 9 in 84% yield. In-
termediate 9 could then be transformed to 2,3-bis-substitued
unprotected indole 10 [10], cyclic nitrone 11 [3,10] and asymmetric
cyclopropane (1R,2R,10R)-12 [11], which appear in numerous nat-
ural products and medicinally active compounds.
Subsequently, a plausible mechanism has been proposed for this
reaction based on literature reports (Scheme 3) [4]. At the start, a
well-established rhodium(I) cyclobutanolate I is formed and then
b-C elimination occurs to release the strain of the four-membered
ring, affording the vinylrhodium species II. Protonation of II by 1a
yields the ring opening product 2a and regenerates the rhodium(I)

Y. Nie et al. / Tetrahedron 75 (2019) 130563
3
Table 2
Substrate scopea
Entry
1
Product
Yield (%)b
82
Entry
13
Product
Yield (%)b
91
2c
3c
4c
87
84
61
14c
15
63
82
66
16
5c
82
77
17
18
95
81
6
7
8
82
61
19c
20c
61
88
9
64
92
70
21
22
23
94
93
91
10
11
12
81
24
92
a
Reaction conditions: substrate 1a (0.4 mmol, 1.0 equiv.), [Rh(COD)Cl]2 (0.01 mmol, 2.5 mol %), AgOAc (0.6 mmol, 15 mol %), ligand (0.04 mmol, 10 mol %) in sealed tube
with 2 mL solvent at 110 ꢀC for 12 h.
b
Isolated yield.
[Rh(COD)Cl]2 is 5.0 mol %.
c

4
Y. Nie et al. / Tetrahedron 75 (2019) 130563
3. Conclusions
In conclusion, we have developed a Rh(I)-catalyzed ring-open-
ing of cyclobutanols, affording various ring opened products
bearing cis-olefins and remote aldehydes. The synthetic potential of
the products was demonstrated via several easy derivatizations. In
addition, the strain of the four-membered ring is required for this
ring-opening reaction, as verified experimentally. Moreover, pre-
liminary mechanistic studies suggest a b-C elimination pathway
according to deuterium labeling experiment.
4. Experimental section
4.1. General
All reagents were commercially available and were used
without further purification unless otherwise indicated. All sol-
vents were dried and distilled before use according to the standard
methods. Analytical thin layer chromatography (TLC) was per-
formed on precoated silica gel F254 plates. Visualization on TLC was
achieved with UV light (254 nm) and potassium permanganate as
visualization methods. 1H NMR spectra were recorded on Bruker
(400 or 500 MHz). Chemical shifts were quoted in parts per million
(ppm) referenced to 0.00 ppm for tetramethylsilane. Data for 1H
NMR spectra are reported as follows: chemical shift (
d shift),
multiplicity (s ¼ singlet, d ¼ doublet, t ¼ triplet, q ¼ quartet,
m ¼ multiplet, dd ¼ double of doublet, ddd ¼ double of dd,
dt ¼ double of triplet, td ¼ triple of doublet), coupling constant (Hz)
and integration. 13C NMR spectra were recorded on Bruker (101 or
126 MHz). Chemical shifts were reported in ppm referenced to the
center line of a triplet at 77.0 ppm of chloroform-d. High resolution
mass spectra (HRMS) were obtained with ACQUITYTM UPLC & Q-
TOF MS Premier Spectrometer at the Instrumental Analysis Center
of Shanghai Jiao Tong University. Melting points were measured
with SGW X-4 micro melting point apparatus.
Scheme 2. Synthetic applications and transformations. i) NaBH4, MeOH, 0 ꢀCeRT,
0.5 h. ii) n-BuLi, THF, bromo (cyclopentyl) triphenyl-l
5-phosphane, RT, 24 h iii) K3PO4,
MeOH, dimethyl-(1-diazo-2-oxopropyl)phosphonate, RT, 24 h. iv) PhMgBr, THF, RT,
12 h. v) CrO3/H2SO4/H2O, acetone, 0 ꢀC e RT, overnight.
4.2. General procedure of Rh(I)-catalyzed ring-opening of
cyclobutanols
An oven-dried 25 mL round bottom Schlenk tube was equipped
with a magnetic stir bar and charged with substrate (0.4 mmol, 1.0
equiv.), [Rh(COD)Cl]2 (4.9 mg, 0.01 mmol, 2.5 mol %), AgOAc
(10.0 mg, 0.06 mmol, 15 mol %), and PCy3(11.2 mg, 0.04 mmol,
10 mol %) under N2 atmosphere, then the mixture was dissolved in
dry toluene. The solution was stirred at 110 ꢀC for 12 h. After the
reaction mixture was cooled to room temperature, and then the
product was extracted with EtOAc (10 ml x3). The combined
organic phase was washed with brine (10 ml x3), dried over
anhydrous Na2SO4 and evaporated, and the residue was purified by
column chromatography (eluent: petroleum ether/EtOAc ¼ 10/1) to
give the corresponding product.
Scheme 3. Proposed mechanism.
cyclobutanolate I.
The deuterated substrate D-1a was tested under standard con-
ditions and it was found that deuterium was incorporated as the
aldehyde H (Scheme 4). This result further proves our proposed
mechanism.
4.2.1. (Z)-5-Phenylpent-4-enal (2a)
Yellow oil (53 mg, 82% yield). 1H NMR (500 MHz, Chloroform-d)
d
9.75 (s, 1H), 7.33 (t, J ¼ 7.0 Hz, 2H), 7.29e7.17 (m, 3H), 6.48 (d,
J ¼ 11.0 Hz, 1H), 5.61 (dt, J ¼ 11.5, 7.0 Hz, 1H), 2.66 (q, J ¼ 7.0 Hz, 2H),
2.56 (t, J ¼ 7.0 Hz, 2H). 13C NMR (126 MHz, Chloroform-d)
d 201.7,
130.4, 130.0, 128.7, 128.3, 126.9, 43.9, 21.3. HRMS (ESI): calcd. for
C
11H12O(M þ H)þ 161.0961; found 161.0969.
4.2.2. (Z)-5-(o-Tolyl)pent-4-enal (2b)
Yellow oil (61 mg, 87% yield). 1H NMR (500 MHz, Chloroform-d)
d
9.70 (s, 1H), 7.22e7.10 (m, 4H), 6.50 (d, J ¼ 11.0 Hz, 1H), 5.68 (dt,
J ¼ 11.5, 7.0 Hz, 1H), 2.49 (s, 4H), 2.24 (s, 3H). 13C NMR (126 MHz,
Scheme 4. The deuterated experiment.
Chloroform-d) d 201.9, 136.3, 136.2, 129.9, 129.9, 129.7, 128.9, 127.1,

Y. Nie et al. / Tetrahedron 75 (2019) 130563
5
125.5, 43.8, 21.2, 19.9. HRMS (ESI): calcd. for C12H14O (M þ H)þ
d
9.78 (t, J ¼ 1.2 Hz, 1H), 7.59 (d, J ¼ 8.0 Hz, 2H), 7.37 (d, J ¼ 8.0 Hz,
2H), 6.50 (d, J ¼ 11.6 Hz, 1H), 5.72 (dt, J ¼ 11.6, 7.2 Hz, 1H), 2.70e2.54
(m, 4H). 13C NMR (101 MHz, Chloroform-d)
201.2, 140.6, 132.2,
175.1117; found 175.1120.
d
4.2.3. (Z)-5-(2-bromophenyl)pent-4-enal (2c)
129.1, 128.9, 128.9 (q, J ¼ 32.6 Hz), 125.2 (q, J ¼ 3.7 Hz), 124.2 (q,
J ¼ 272.7 Hz), 43.7, 21.2. HRMS (ESI): calcd. for C12H11F3O (M þ H)þ
229.0835; found 229.0841.
Yellow oil (80 mg, 84% yield). 1H NMR (500 MHz, Chloroform-d)
d
9.74 (s, 1H), 7.58 (d, J ¼ 8.0 Hz, 1H), 7.32e7.23 (m, 2H), 7.12 (td,
J ¼ 8.5, 2.5 Hz, 1H), 6.51 (d, J ¼ 11.5 Hz, 1H), 5.73 (dt, J ¼ 11.0, 7.5 Hz,
1H), 2.58e2.53 (m, 2H), 2.52e2.47 (m, 2H). 13C NMR (126 MHz,
4.2.11. (Z)-5-(4-methoxyphenyl)pent-4-enal (2k)
Yellow oil (53 mg, 70% yield). 1H NMR (400 MHz, Chloroform-d)
Chloroform-d)
d 201.5, 137.1, 132.7, 131.1, 130.4, 130.0, 128.6, 127.0,
43.5, 21.1. HRMS (ESI): calcd. for C11H11BrO (M þ H)þ 239.0066;
d
9.76 (s, 1H), 7.20 (d, J ¼ 8.4 Hz, 2H), 6.87 (d, J ¼ 8.4 Hz, 2H), 6.41 (d,
found 239.0072.
J ¼ 11.6 Hz, 1H), 5.50 (dt, J ¼ 11.6, 6.8 Hz, 1H), 3.80 (s, 3H), 2.71e2.61
(m, 2H), 2.56 (t, J ¼ 7.2 Hz, 2H). 13C NMR (126 MHz, Chloroform-d)
4.2.4. (Z)-5-(3-chlorophenyl)pent-4-enal (2d)
d
201.9, 129.9, 129.8, 128.5, 113.7, 55.3, 44.0, 21.3. HRMS (ESI): calcd.
Yellow oil (47 mg, 61% yield). 1H NMR (400 MHz, Chloroform-d)
for C12H14O2 (M þ H)þ 191.1067; found 191.1071.
d
9.77 (s, 1H), 7.30e7.19 (m, 3H), 7.14 (d, J ¼ 7.2 Hz, 1H), 6.41 (d,
J ¼ 11.6 Hz, 1H), 5.65 (dt, J ¼ 11.6, 6.8 Hz, 1H), 2.70e2.51 (m, 4H). 13
C
4.2.12. (Z)-5-(4-(trifluoromethoxy)phenyl)pent-4-enal (2l)
Yellow oil (79 mg, 81% yield). 1H NMR (400 MHz, Chloroform-d)
NMR (101 MHz, Chloroform-d)
d 201.4, 138.9, 134.1, 131.4, 129.5,
129.1, 128.7, 126.9, 126.8, 43.7, 21.2. HRMS (ESI): calcd. for C11H11ClO
d
9.78 (s, 1H), 7.28 (d, J ¼ 8.8 Hz, 2H), 7.18 (d, J ¼ 8.4 Hz, 2H), 6.45 (d,
(M þ H)þ 195.0571; found 195.0579.
J ¼ 11.6 Hz, 1H), 5.65 (dt, J ¼ 11.2, 7.2 Hz, 1H), 2.71e2.50 (m, 4H). 13
C
NMR (101 MHz, Chloroform-d)
d 201.4, 135.8, 131.0, 130.0, 129.0,
4.2.5. (Z)-5-(3-nitrophenyl)pent-4-enal (2e)
120.8, 120.5 (q, J ¼ 258.0 Hz), 43.7, 21.2. HRMS (ESI): calcd. for
Yellow oil (67 mg, 82% yield). 1H NMR (400 MHz, Chloroform-d)
C
12H11F3O2 (M þ H)þ 245.0784; found 245.0779.
d
9.80 (s, 1H), 8.10 (d, J ¼ 8.8 Hz, 2H), 7.60 (d, J ¼ 7.6 Hz, 1H), 7.52 (t,
J ¼ 8.0 Hz, 1H), 6.52 (d, J ¼ 11.6 Hz, 1H), 5.86e5.71 (m, 1H),
2.71e2.57 (m, 4H). 13C NMR (101 MHz, Chloroform-d)
201.0, 148.3,
4.2.13. (Z)-5-(4-bromophenyl)pent-4-enal (2m)
d
Yellow oil (87 mg, 91% yield). 1H NMR (500 MHz, Chloroform-d)
138.7, 134.6, 133.0, 129.2, 128.1, 123.4, 121.7, 43.5, 21.1. HRMS (ESI):
d
9.76 (t, J ¼ 1.5 Hz, 1H), 7.45 (d, J ¼ 8.5 Hz, 2H), 7.13 (d, J ¼ 8.5 Hz,
2H), 6.39 (dt, J ¼ 11.5, 1.5 Hz, 1H), 5.63 (dt, J ¼ 11.5, 6.5 Hz, 1H),
2.65e2.54 (m, 4H). 13C NMR (126 MHz, Chloroform-d)
201.4,131.4,
calcd. for C11H11NO3 (M þ H)þ 206.0812; found 206.0817.
d
4.2.6. (Z)-5-(m-tolyl)pent-4-enal (2f)
130.9, 130.3, 129.2, 43.7, 21.2. HRMS (ESI): calcd. for C11H11BrO
Yellow oil (54 mg, 77% yield). 1H NMR (400 MHz, Chloroform-d)
(M þ H)þ 239.0066; found 239.0072.
d
9.75 (s, 1H), 7.27e7.17 (m, 1H), 7.11e7.00 (m, 3H), 6.45 (d,
J ¼ 11.6 Hz, 1H), 5.58 (dt, J ¼ 11.6, 7.2 Hz, 1H), 2.71e2.60 (m, 2H),
4.2.14. (Z)-5-(4-chlorophenyl)pent-4-enal (2n)
2.55 (t, J ¼ 7.6 Hz, 2H), 2.35 (s, 3H). 13C NMR (126 MHz, Chloroform-
Yellow ointment (48 mg, 63% yield). 1H NMR (400 MHz, Chlo-
d)
d 201.8, 137.0, 130.5, 129.9, 129.5, 128.2, 127.6, 125.7, 43.9, 21.5,
roform-d)
J ¼ 8.4 Hz, 2H), 6.42 (dt, J ¼ 11.6, 1.6 Hz, 1H), 5.62 (dt, J ¼ 11.6, 6.8 Hz,
1H), 2.70e2.50 (m, 4H). 13C NMR (101 MHz, Chloroform-d)
201.4,
d
9.77 (t, J ¼ 1.6 Hz, 1H), 7.30 (d, J ¼ 8.0 Hz, 2H), 7.19 (d,
21.4. HRMS (ESI): calcd. for C12H14O (M þ H)þ 175.1117; found
175.1121.
d
135.5, 131.1, 130.7, 130.0, 129.2, 128.4, 43.7, 21.2. HRMS (ESI): calcd.
4.2.7. (Z)-5-(3-methoxyphenyl)pent-4-enal (2g)
for C11H11ClO (M þ H)þ 195.0571; found 195.0574.
Yellow oil (62 mg, 82% yield). 1H NMR (400 MHz, Chloroform-d)
d
9.76 (t, J ¼ 1.6 Hz, 1H), 7.29e7.21 (m, 1H), 6.86 (d, J ¼ 7.6 Hz, 1H),
6.82e6.76 (m, 2H), 6.45 (dt, J ¼ 11.6, 1.6 Hz, 1H), 5.61 (dt, J ¼ 11.6,
7.2 Hz, 1H), 3.81 (s, 3H), 2.70e2.62 (m, 2H), 2.60e2.53 (m, 2H). 13
NMR (101 MHz, Chloroform-d) 201.7, 159.5, 138.5, 130.3, 130.3,
4.2.15. (Z)-5-(4-(tert-butyl)phenyl)pent-4-enal (2o)
Yellow oil (71 mg, 82% yield). 1H NMR (400 MHz, Chloroform-d)
C
d
9.77 (t, J ¼ 1.6 Hz, 1H), 7.36 (d, J ¼ 8.4 Hz, 2H), 7.21 (d, J ¼ 8.0 Hz,
d
2H), 6.45 (dt, J ¼ 11.6, 1.6 Hz, 1H), 5.56 (dt, J ¼ 11.6, 7.2 Hz, 1H),
129.3, 121.2, 114.4, 112.3, 55.2, 43.8, 21.4. HRMS (ESI): calcd. for
C
2.73e2.62 (m, 2H), 2.61e2.52 (m, 2H), 1.32 (s, 9H). 13C NMR
12H14O2 (M þ H)þ 191.1097; found 191.1091.
(126 MHz, Chloroform-d)
d 201.9, 149.8, 134.2, 130.2, 129.4, 128.5,
125.2, 44.0, 34.6, 31.3, 21.4. HRMS (ESI): calcd. for C15H20O (M þ H)þ
4.2.8. (Z)-5-(3-hydroxyphenyl)pent-4-enal (2h)
Yellow oil (43 mg, 61% yield). 1H NMR (400 MHz, Chloroform-d)
217.1587; found 217.1585.
d
9.75 (t, J ¼ 1.6 Hz, 1H), 7.19 (t, J ¼ 8.0 Hz, 1H), 6.83e6.69 (m, 3H),
4.2.16. (Z)-5-([1,10-biphenyl]-4-yl)pent-4-enal (2p)
6.41 (dt, J ¼ 11.6, 2.0 Hz, 1H), 6.34e6.04 (br, 1H), 5.58 (dt, J ¼ 11.6,
Yellow oil (63 mg, 66% yield). 1H NMR (400 MHz, Chloroform-d)
6.8 Hz, 1H), 2.70e2.61 (m, 2H), 2.61e2.53 (m, 2H). 13C NMR
d
9.77 (s, 1H), 7.58 (t, J ¼ 8.4 Hz, 4H), 7.43 (t, J ¼ 8.0 Hz, 2H), 7.34 (d,
(101 MHz, Chloroform-d)
d 202.6, 155.8, 138.6, 130.2, 130.1, 129.5,
J ¼ 8.0 Hz, 3H), 6.50 (d, J ¼ 12.0 Hz,1H), 5.63 (dt, J ¼ 11.6, 6.8 Hz, 1H),
121.1, 115.5, 114.0, 43.8, 21.4. HRMS (ESI): calcd. for C11H12O2
2.75e2.65 (m, 2H), 2.58 (t, J ¼ 7.2 Hz, 2H). 13C NMR (101 MHz,
(M þ H)þ 177.0910; found 177.0913.
Chloroform-d)
d 201.7, 140.7, 139.7, 136.1, 130.3, 139.0, 129.2, 128.8,
127.3, 127.0, 127.0, 43.9, 21.5. HRMS (ESI): calcd. for C17H16
O
4.2.9. (Z)-5-(p-tolyl)pent-4-enal (2i)
(M þ H)þ 237.1274; found 237.1279.
Yellow oil (45 mg, 64% yield). 1H NMR (500 MHz, Chloroform-d)
d
9.76 (t, J ¼ 1.5 Hz, 1H), 7.19e7.11 (m, 4H), 6.45 (dt, J ¼ 11.5, 2.0 Hz,
1H), 5.56 (dt, J ¼ 11.5, 7.0 Hz, 1H), 2.70e2.62 (m, 2H), 2.60e2.53 (m,
2H), 2.34 (s, 3H). 13C NMR (126 MHz, Chloroform-d)
201.9, 136.6,
4.2.17. (Z)-5-mesitylpent-4-enal (2q)
d
Yellow oil (77 mg, 95% yield). 1H NMR (500 MHz, Chloroform-d)
9.64 (s, 1H), 6.85 (s, 2H), 6.32 (d, J ¼ 11.0 Hz, 1H), 5.70 (dt, J ¼ 11.0,
134.2, 130.3, 129.3, 129.0, 128.6, 43.9, 21.4, 21.2. HRMS (ESI): calcd.
d
for C12H14O (M þ H)þ 175.1117; found 175.1114.
7.5 Hz, 1H), 2.41 (td, J ¼ 7.0, 1.5 Hz, 2H), 2.27 (s, 3H), 2.18e2.12 (m,
2H), 2.15 (s, 6H). 13C NMR (126 MHz, Chloroform-d)
d 201.9, 136.2,
4.2.10. (Z)-5-(4-(trifluoromethyl)phenyl)pent-4-enal (2j)
135.8, 133.1, 130.5, 129.2, 128.0, 43.2, 21.5, 21.0, 20.3. HRMS (ESI):
Yellow oil (84 mg, 92% yield). 1H NMR (400 MHz, Chloroform-d)
calcd. for C14H18O (M þ H)þ 203.1430; found 203.1436.

6
Y. Nie et al. / Tetrahedron 75 (2019) 130563
4.2.18. (Z)-5-(naphthalen-2-yl)pent-4-enal (2r)
4.3. Deuteration experiments
Yellow oil (68 mg, 81% yield). 1H NMR (400 MHz, Chloroform-d)
9.73 (s, 1H), 7.85e7.74 (m, 3H), 7.69 (s, 1H), 7.50e7.41 (m, 2H), 7.39
d
4.3.1. (E)-2-benzylidenecyclobutan-1-d-1-ol (D-1a)
(dd, J ¼ 8.4, 1.6 Hz, 1H), 6.61 (dt, J ¼ 11.6, 2.0 Hz, 1H), 5.67 (dt,
To a 50 mL round-bottomed flask, NaBD4 (3.6 mmol, 0.6 equiv.)
was added to a stirred solution of S-1a (6.0 mmol,1 equiv.) in MeOH
(10 mL) at 0 ꢀC. After stirring at 0 ꢀC for 1 h and additional 3 h at
room temperature, the reaction was quenched by addition of water.
The MeOH was removed by rotary evaporation and the remaining
aqueous phase was extracted with DCM (10 ml x3). The combined
organic phase was washed with brine (10 ml x3), dried over
anhydrous Na2SO4 and evaporated, and the residue was purified by
column chromatography to give corresponding deuterated sub-
strate D-1a.
J ¼ 11.6, 7.2 Hz, 1H), 2.72 (qd, J ¼ 7.2, 1.6 Hz, 2H), 2.56 (t, J ¼ 7.2 Hz,
2H). 13C NMR (126 MHz, Chloroform-d)
d 201.7, 134.7, 133.3, 132.3,
130.5, 130.4, 128.0, 127.8, 127.6, 127.5, 127.0, 126.2, 125.9, 43.9, 21.4.
HRMS (ESI): calcd. for C15H14O (M þ H)þ 211.1117; found 211.1112.
4.2.19. (Z)-5-(furan-2-yl)pent-4-enal (2s)
Yellow oil (37 mg, 61% yield). 1H NMR (500 MHz, Chloroform-d)
d
9.82 (d, J ¼ 1.5 Hz, 1H), 7.39 (d, J ¼ 1.5 Hz, 1H), 6.40 (dd, J ¼ 3.0,
1.5 Hz, 1H), 6.27 (d, J ¼ 3.5 Hz,1H), 6.22 (dt, J ¼ 12.0, 1.5 Hz,1H), 5.50
White solid (0.8 g, 84% yield). Mp 75e76 ꢀC; 1H NMR (400 MHz,
(dt, J ¼ 11.5, 7.5 Hz, 1H), 2.81 (qd, J ¼ 7.5, 1.5 Hz, 2H), 2.63 (td, J ¼ 7.5,
1.5 Hz, 2H). 13C NMR (126 MHz, Chloroform-d)
d 202.0, 152.9, 141.8,
Chloroform-d)
d
7.37e7.29 (m, 2H), 7.26 (d, J ¼ 6.0 Hz, 2H), 7.21 (t,
J ¼ 7.2 Hz, 1H), 6.43 (t, J ¼ 2.4 Hz, 1H), 2.85e2.73 (m, 1H), 2.72e2.59
127.7, 118.5, 111.1, 109.7, 43.7, 22.0. HRMS (ESI): calcd. for C9H10O2
(M þ H)þ 151.0754; found 151.0758.
(m, 1H), 2.55e2.43 (m, 1H), 1.95 (q, J ¼ 9.6 Hz, 1H), 1.77e1.42 (br,
1H). 13C NMR (101 MHz, Chloroform-d)
d 147.8, 128.5, 127.8, 126.7,
120.1, 71.8 (t, J ¼ 23.6 Hz), 31.8, 25.2. HRMS (ESI): calcd. for
11H11DO (M þ H)þ 162.1024; found 162.1029.
4.2.20. (Z)-5-(benzofuran-2-yl)pent-4-enal (2t)
C
Yellow ointment (70 mg, 88% yield). 1H NMR (400 MHz, Chlo-
roform-d)
d
9.83 (t, J ¼ 1.6 Hz, 1H), 7.56e7.50 (m, 1H), 7.47e7.42 (m,
4.3.2. (Z)-5-phenylpent-4-enal-1-d (D-2a)
1H), 7.26 (td, J ¼ 7.2, 1.2 Hz, 1H), 7.20 (td, J ¼ 7.6, 0.8 Hz, 1H), 6.60 (s,
1H), 6.32 (dt, J ¼ 12.0, 1.6 Hz, 1H), 5.71 (dt, J ¼ 11.6, 7.6 Hz, 1H), 2.95
(qd, J ¼ 7.2, 1.6 Hz, 2H), 2.66 (td, J ¼ 7.2, 1.6 Hz, 2H). 13C NMR
An oven-dried 25 mL round bottom Schlenk tube was equipped
with
a magnetic stir bar and charged with substrate D-1a
(0.4 mmol, 1.0 equiv.), [Rh(COD)Cl]2 (4.9 mg, 0.01 mmol, 2.5 mol %),
AgOAc (10.0 mg, 0.06 mmol, 15 mol %), and PCy3(11.2 mg,
0.04 mmol, 10 mol %) under N2 atmosphere, then the mixture was
dissolved in dry toluene. The solution was stirred at 110 ꢀC for 12 h.
After the reaction mixture was cooled to room temperature, and
then the product was extracted with EtOAc (10 ml x3). The com-
bined organic phase was washed with brine (10 ml x3), dried over
anhydrous Na2SO4 and evaporated, and the residue was purified by
column chromatography (eluent: petroleum ether/EtOAc ¼ 10/1) to
give the corresponding product D-2a.
(101 MHz, Chloroform-d)
d 201.8, 154.7, 154.6, 131.7, 128.5, 124.5,
122.9, 120.9, 118.7, 111.1, 106.2, 43.7, 22.3. HRMS (ESI): calcd. for
C
13H12O2 (M þ H)þ 201.0910; found 201.0917.
4.2.21. (Z)-5-(benzo[b]thiophen-2-yl)pent-4-enal (2u)
Yellow ointment (81 mg, 94% yield). 1H NMR (500 MHz, Chlo-
roform-d)
d
9.80 (t, J ¼ 1.5 Hz, 1H), 7.77 (dd, J ¼ 8.0, 1.0 Hz, 1H), 7.71
(dd, J ¼ 8.0, 1.0 Hz, 1H), 7.32 (td, J ¼ 7.5, 1.5 Hz, 1H), 7.28 (td, J ¼ 7.5,
1.5 Hz, 1H), 7.17 (s, 1H), 6.61 (dt, J ¼ 12.0, 2.0 Hz, 1H), 5.65 (dt,
J ¼ 11.5, 7.5 Hz, 1H), 2.81 (qd, J ¼ 7.5, 1.5 Hz, 2H), 2.64 (td, J ¼ 7.0,
Yellow oil (53 mg, 83% yield). 1H NMR (400 MHz, Chloroform-d)
1.0 Hz, 2H). 13C NMR (126 MHz, Chloroform-d)
d
201.4, 140.0, 139.9,
d
7.37e7.30 (m, 2H), 7.29e7.20 (m, 3H), 6.48 (dt, J ¼ 11.6, 2.0 Hz,1H),
5.60 (dt, J ¼ 11.6, 7.2 Hz, 1H), 2.71e2.61 (m, 2H), 2.59e2.51 (m, 2H).
13C NMR (101 MHz, Chloroform-d)
139.3, 130.6, 124.5, 124.5, 124.3, 123.7, 123.5, 122.1, 43.5, 21.9. HRMS
(ESI): calcd. for C13H12OS (M þ H)þ 217.0682; found 217.0687.
d
201.4 (t, J ¼ 26.5 Hz), 137.1,
130.4, 130.1, 128.7, 128.3, 126.9, 43.7 (t, J ¼ 3.7 Hz), 21.3. HRMS (ESI):
calcd. for C11H11DO (M þ H)þ 162.1024; found 162.1021.
4.2.22. (Z)-5-cyclohexylpent-4-enal (2v)
Yellow oil (62 mg, 93% yield). 1H NMR (500 MHz, Chloroform-d)
4.4. Applications and transformations
d
9.78 (s, 1H), 5.32e5.16 (m, 2H), 2.49 (t, J ¼ 7.0 Hz, 2H), 2.38 (q,
J ¼ 7.0 Hz, 2H), 1.76e1.51 (m, 8H), 1.22e1.18 (m, 1H), 1.06 (qd,
J ¼ 13.0, 3.0 Hz, 2H). 13C NMR (126 MHz, Chloroform-d)
d 202.3,
4.4.1. (Z)-5-phenylpent-4-en-1-ol (3)
To a 25 mL round-bottomed flask, NaBH4 (0.24 mmol, 0.6 equiv.)
was added to a stirred solution of 2a (0.4 mmol, 1.0 equiv.) in MeOH
(2 mL) at 0 ꢀC. After stirring at 0 ꢀC for 10 min and an additional
20 min at room temperature, the reaction was quenched by the
addition of water. The MeOH was removed by rotary evaporation
and the remaining aqueous phase was extracted with DCM (10 ml
x3). The combined organic phase was washed with brine (10 ml
x3), dried over anhydrous Na2SO4 and evaporated, and the residue
was purified by column chromatography to give the corresponding
product 3.
137.7, 125.2, 44.1, 36.3, 33.2, 30.3, 26.0, 25.9, 20.3, 15.4. HRMS (ESI):
calcd. for C11H18O (M þ H)þ 167.1430; found 167.1439.
4.2.23. (Z)-5-cyclopentylpent-4-enal (2w)
Colorless oil (55 mg, 91% yield).1H NMR (500 MHz, Chloroform-
d)
d
9.77 (t, J ¼ 1.5 Hz, 1H), 5.36 (tt, J ¼ 11.0, 1.5 Hz, 1H), 5.26 (dt,
J ¼ 11.0, 7.5 Hz, 1H), 2.75e2.64 (m, 1H), 2.52e2.45 (m, 2H),
2.43e2.36 (q, J ¼ 7.2 Hz, 2H), 1.83e1.72 (m, 2H), 1.71e1.62 (m, 2H),
1.61e1.50 (m, 2H), 1.29e1.14 (m, 2H). 13C NMR (126 MHz, Chloro-
Yellow oil (62 mg, 97% yield). 1H NMR (400 MHz, Chloroform-d)
form-d) d 202.3, 137.0, 125.6, 44.0, 38.1, 33.7, 25.4, 20.4. HRMS (ESI):
calcd. for C10H16O (M þ H)þ 153.1274; found 153.1279.
d
7.37e7.24 (m, 4H), 7.19 (tt, J ¼ 7.2, 1.6 Hz, 1H), 6.42 (dt, J ¼ 16.0,
1.6 Hz, 1H), 6.22 (dt, J ¼ 16.0, 6.8 Hz, 1H), 3.69 (t, J ¼ 6.4 Hz, 2H),
4.2.24. (4Z,6E)-7-phenylhepta-4,6-dienal (2x)
2.37e2.25 (m, 2H), 1.81e1.70 (m, 2H), 1.70e1.54 (br, 1H). 13C NMR
Yellow oil (68 mg, 92% yield). 1H NMR (500 MHz, Chloroform-d)
(101 MHz, Chloroform-d) d 137.6, 130.4, 130.1, 128.5, 127.0, 126.0,
d
9.79 (t, J ¼ 1.0 Hz, 1H), 7.44e7.38 (m, 2H), 7.31 (t, J ¼ 7.5 Hz, 2H),
62.4, 32.3, 29.3. HRMS (ESI): calcd. for C11H14O (M þ H)þ 163.1117;
7.25e7.19 (m, 1H), 7.04 (ddd, J ¼ 15.5, 11.0, 1.0 Hz, 1H), 6.55 (d,
J ¼ 15.5 Hz, 1H), 6.19 (t, J ¼ 11.0 Hz, 1H), 5.46 (dt, J ¼ 10.5, 7.0 Hz, 1H),
found 163.1121.
2.66e2.51 (m, 4H). 13C NMR (126 MHz, Chloroform-d)
d
201.7, 137.3,
4.4.2. (Z)-(5-cyclopentylidenepent-1-en-1-yl)benzene (4)
133.2, 130.1, 129.8, 128.7, 127.7, 126.5, 123.7, 43.7, 20.7. HRMS (ESI):
To
a dry THF solution (5 mL) of cyclopentyltriphenylph-
calcd. for C13H14O (M þ H)þ 187.1117; found 187.1114.
osphonium bromide (987 mg, 2.4 mmol) cooled at 0 ꢀC in an ice-

Y. Nie et al. / Tetrahedron 75 (2019) 130563
7
bath was slowly added a hexane solution of n-BuLi (2.5 M, 1.2 mL,
3.0 mmol). The mixture was stirred at room temperature for 1 h.
Then a dry THF solution (5 mL) of 2a (320 mg, 2.0 mmol) was added
to the mixture. The mixture was stirred at room temperature for
24 h. After the reaction was completed, the mixture was quenched
with saturated aqueous NH4Cl, and then the product was extracted
with EtOAc (10 ml x3). The combined organic phase was washed
with brine (10 ml x3), dried over anhydrous Na2SO4 and evapo-
rated, and the residue was purified by column chromatography
(eluent: petroleum ether/EtOAc ¼ 10/1) to give corresponding
product 4.
room temperature and stirred overnight. Upon completion of the
reaction, the mixture was quenched by the addition saturated
aqueous of NH4Cl and the product was extracted with EtOAc (10 ml
x3). The combined organic phase was washed with brine (10 ml
x3), dried over anhydrous Na2SO4 and evaporated. The residue was
purified by column chromatography (eluent: petroleum ether/
EtOAc ¼ 5/1) to give corresponding product 9.
Yellow oil (147 mg, 84% yield). 1H NMR (400 MHz, Chloroform-d)
d
7.96e7.90 (m, 2H), 7.56e7.49 (m, 1H), 7.47e7.39 (m, 2H), 7.19 (d,
J ¼ 8.0 Hz, 2H), 7.12 (d, J ¼ 8.0 Hz, 2H), 6.43 (d, J ¼ 11.6 Hz, 1H), 5.65
(dt, J ¼ 11.6, 7.2 Hz, 1H), 3.11e3.02 (m, 2H), 2.77 (qd, J ¼ 7.6, 1.6 Hz,
Yellow oil (323 mg, 76% yield). 1H NMR (400 MHz, Chloroform-
2H), 2.32 (s, 3H). 13C NMR (126 MHz, Chloroform-d)
d 199.4, 136.9,
d)
d
7.35e7.24 (m, 4H), 7.23e7.15 (m, 1H), 6.41 (d, J ¼ 12.0 Hz, 1H),
136.4, 134.5, 133.1, 130.3, 129.9, 129.0, 128.7, 128.6, 128.1, 38.7, 23.4,
21.2. HRMS (ESI): calcd. for C17H16O (M þ H)þ 237.1274; found
237.1280.
5.67 (dt, J ¼ 11.6, 7.6 Hz, 1H), 5.23 (t, J ¼ 5.6 Hz, 1H), 2.45e2.33 (m,
2H), 2.27e2.07 (m, 6H), 1.71e1.53 (m, 4H). 13C NMR (126 MHz,
Chloroform-d)
d 144.0, 137.9, 132.9, 129.1, 128.9, 128.2, 126.5, 119.4,
33.7, 30.1, 28.9, 28.8, 26.6, 26.5. HRMS (ESI): calcd. for C16H20
O
Acknowledgments
(M þ H)þ 213.1638; found 213.1632.
We would like to thank National Natural Science Foundation of
China (Nos. 21702134, 21772119 and 21620102003), Science and
Technology Commission of Shanghai Municipality (No.
17ZR1415200) and Shanghai Municipal Education Commission (No.
201701070002E00030) for financial support. We thank the
Instrumental Analysis Center of SJTU for characterization.
4.4.3. (Z)-hex-1-en-5-yn-1-ylbenzene (5)
To a 25 mL round-bottomed flask, which was equipped with a
magnetic stir bar, was added 2a (1 mmol, 1.0 equiv.) and K3PO4
(2.0 mmol, 2.0 equiv.) under a N2 atmosphere. The mixture was
dissolved in dry MeOH. Then a dry MeOH solution of dimethyl (1-
diazo-2-oxopropyl)phosphonate (1.2 mmol, 1.2 equiv.) was added
to the mixture. The mixture was stirred at room temperature for
24 h. After the reaction was completed, the product was extracted
with EtOAc (10 ml x3). The combined organic phase was washed
with brine (10 ml x3), dried over anhydrous Na2SO4 and evapo-
rated, and the residue was purified by column chromatography
(eluent: petroleum ether/EtOAc ¼ 10/1) to give corresponding
product 5.
Appendix A. Supplementary data
Supplementary data to this article can be found online at
https://doi.org/10.1016/j.tet.2019.130563.
References
Yellow oil (147 mg, 94% yield). 1H NMR (500 MHz, Chloroform-d)
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7.36e7.30 (m, 2H), 7.30e7.25 (m, 2H), 7.25e7.20 (m, 1H), 6.51 (dt,
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4.4.4. (Z)-1-phenyl-5-(p-tolyl)pent-4-en-1-ol (6)
To a solution of 2i (400 mg, 2.3 mmol) in dry THF (10 mL),
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reaction, the mixture was quenched by addition of saturated
aqueous NH4Cl. The product was extracted with EtOAc (10 ml x3).
The combined organic phase was washed with brine (10 ml x3),
dried over anhydrous Na2SO4 and evaporated. The residue was
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d
7.28e7.15 (m, 5H), 7.07 (q, J ¼ 8.4 Hz, 4H), 6.35 (d, J ¼ 11.6 Hz,
1H), 5.55 (dt, J ¼ 11.6, 7.2 Hz, 1H), 4.53 (t, J ¼ 6.8 Hz, 1H), 2.46 (br,
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(126 MHz, Chloroform-d)
d 144.7, 136.3, 134.8, 131.5, 129.5, 129.1,
128.8, 128.5, 127.6, 126.1, 74.1, 39.3, 25.2, 21.4. HRMS (ESI): calcd. for
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4.4.5. (Z)-1-phenyl-5-(p-tolyl)pent-4-en-1-one (9)
To a 5 mL round-bottomed flask, Cr3O (213 mg, 0.74 mmol),
H2SO4 (0.22 mL) and H2O (0.5 mL) were added, and the mixture
was stirred for 30 min at room temperature. To a solution of 6
(239 mg, 1 mmol) in acetone, the resulting Cr3O/H2SO4/H2O
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