Mechanistic Studies on Propargyl Alcohol-Tethered Alkylidenecyclopropane with Aryldiazonium Salt Initiated by Visible Light

Article abstract of DOI:10.1002/cjoc.202000469

This paper discloses the reaction mechanism of two consecutive but different visible light photo-induced chain processes for the rapid construction of spirobi[indene] skeletons. The first process is triggered by a photo-induced single-electron-transfer (SET) of an electron donor-accepter (EDA) complex. The second process is initiated by a direct SET process between aryldiazonium salt and the excited allenic intermediate. In these two processes, another SET took place respectively on the in situ formed radical intermediate to realize a redox-neutral outcome. The mechanistic studies have been carried out by control experiments, kinetic and spectroscopic analyses, deuterium labeling experiments to support these two chain processes.

Full text of DOI:10.1002/cjoc.202000469

Chinese Journal
of Chemistry
CJC
中 国 化 学 - An International Journal
Accepted Article
Title: Mechanistic studies on propargyl alcohol-tethered alkylidenecyclopropane
with aryldiazonium salt initiated by visible light
Authors: Jiaxin Liu, Yin Wei* and Min Shi
This manuscript has been accepted and appears as an Accepted Article online.
This work may now be cited as: Chin. J. Chem. 2020, 38, 10.1002/cjoc.202000469.
The final Version of Record (VoR) of it with formal page numbers will soon be
published online in Early View: http://dx.doi.org/10.1002/cjoc.202000469.
ISSN 1001-604X • CN 31-1547/O6
mc.manuscriptcentral.com/cjoc
www.cjc.wiley-vch.de

Chinese Journal
of Chemistry
mechanistic study, photoredox, spirobi[indene], chain process
Concise Report
CJC
中
国 化 学 - An International Journal
Mechanistic studies on propargyl alcohol-tethered alkylidenecyclopropane with aryldiazonium salt initiated by visible light
Jiaxin Liu,a Yin Wei*,a and Min Shia,b
a
State Key Laboratory of Organometallic Chemistry, Center for Excellence in Molecular Synthesis, University of Chinese Academy of Science, Shanghai
Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, People’s Republic of China
b Shenzhen Grubbs Institute, Southern University of Science and Technology, Shenzhen, Guangdong 518000, China
Cite this paper: Chin. J. Chem. 2020, 38, XXX—XXX. DOI: 10.1002/cjoc.202000XXX
Summary of main observation and conclusion This paper discloses the reaction mechanism of two consecutive but different visible light photo-induced
chain processes for the rapid construction of spirobi[indene] skeletons. The first process is triggered by a photo-induced single-electron-transfer (SET) of
an electron donor-accepter (EDA) complex. The second process is initiated by a direct SET process between aryldiazonium salt and the excited allenic
intermediate. In these two processes, another SET took place respectively on the in situ formed radical intermediate to realize a redox-neutral outcome.
The mechanistic studies have been carried out by control experiments, kinetic and spectroscopic analyses, deuterium labeling experiments to support
these two chain processes.
the mechanistic investigations on this reaction to well
understanding the detailed reaction process, shedding light on
Background and Originality Content
In the past decade, photoredox catalysis has played a much
the merger of photoredox catalysis with the transformation of
crucial role for the efficient construction of molecular
strained small rings.
complexity in
a
sustainable manner under mild and
environment friendly conditions with a high chemoselectivity.[1]
Generally, the most significant feature of this synthetic
approach is the use of metal complex/organic dye for the
energy transfer or electron energy to a variety of organic
substrates via visible-light photoexcitation to generate highly
reactive species.[2] Thus far, a series of efficient strategies have
been explored in photoredox catalysis such as metal-to-ligand
charge transfer (MLCT),[3] ligand-to-metal charge transfer
(LMCT),[4] hydrogen atom transfer (HAT),[5] proton-coupled
electron transfer (PCET)[6] and so on (Scheme 1a). Moreover,
photo-induced intermolecular charge transfer through
noncovalent interactions of donor and acceptor molecules is
renowned in photochemistry.[7] These exciting findings inspired
us to develop a much facilitated photocatalytic protocol in
organic synthesis.
Scheme 1 Previous work and this work.
Previous strategy in visible
(a)
light photocatalysis
=
M
+
R
*
LMCT
*
R''
R''
Photoredox
MLCT
R
or
=
R''
M
Energy
transfer
R'
R'
work
This
(b)
Ar
ArN2BF4
Chain B
Chain A
OH
2
Ar
Ar
Our group has been working on the chemical transformation
of strained small rings for the rapid construction of poly- and
heterocyclic compounds.[8] On the basis of the aforementioned
outstanding photoredox catalytic processes, we attempted to
develop new synthetic methods by merging photoredox
catalysis strategy with strained small rings to explore new
reaction modes with regard to these small carbocyclic
compounds. Recently, our group has reported a visible-light
photo-induced reaction for rapidly constructing spirobi[indene]s
in good yields and with good functional group tolerance
(Scheme 1b).[9] However, the related mechanistic studies on this
new reaction are insufficient and the real catalytic process has
not been clearly unveiled. The preliminary study indicated that
this reaction must be initiated by the visible-light irradiation. In
addition, the use of a catalytic loading of aryldiazonium salt
suggests that an autocatalytic or a chain process might take
place during the reaction process. Thus, we envisaged that this
reaction may proceed through an unprecedented
photochemical pathway. Thus, it is important to further perform
1
4
*
Ar
3*
Results and Discussion
On the basis of the preliminary study, the acid-catalytic
process has been excluded and a simplified reaction pathway
has been provided.[9] Meanwhile, the allenic product has been
identified under the reaction condition, implying that it was the
intermediate to give 4a. However, the detailed reaction
pathway and the evidence to support this mechanism have not
been fully clarified. To illustrate the real reaction pathway, we
firstly utilized allene intermediate 3a as substrate to examine its
This article has been accepted for publication and undergone full peer review but has not been
through the copyediting, typesetting, pagination and proofreading process which may lead to
differences between this version and the Version of Record. Please cite this article as doi:
10.1002/cjoc.202000469
This article is protected by copyright. All rights reserved.

First author et al.
Report
reaction outcome under the standard reaction conditions and
identified that the desired product 4a could be obtained even
using 0.1 equiv of 2a or in the absence of MeOH, suggesting
that 3a was the intermediate for the formation of 4a (Scheme
2). To simplify the mechanistic investigation, we divided the
reaction pathways into two parts: (1) the formation of 3a from
1a; (2) the formation of 4a from 3a.
illumination of light is not an essential element for the
formation of 3a after the reaction is initiated (Figure 2d).
Moreover, the quantum yield of this reaction was measured to
be 5.7, supporting the domination of chain process without light
irradiation. These results validated that the second SET did not
involve with the excited species and it might take place with a
substrate on the ground state to generate a radical cationic
species. All these evidences demonstrated the existence of a
chain process and the irradiation of visible light is unnecessary
while the reaction has been initiated.
Scheme 2 Transformation of 3a to 4a under different reaction
conditions
O
Ph
N2BF4
eq)
Ph
OMe
Ph
Ph
MeOH
+
•
Figure 1. (a) UV-vis absorption spectra of 1a, 2a and their mixture. (b)
The color change after mixing 1a and 2a.
DCM, blue LEDs,
MeO
overnight
rt,
2a
2a
Ph
92%
yield
(1.0
(0.1
4a
3a
(b)
(a)
UV-Visible absorption spectroscopy
MeOH
3.5
3
+
4a
4a
3a
eq)
eq)
DCM, blue LEDs,
overnight
1a+2a
1a
2a
rt,
93%
2.5
2
yield
1.5
1
2a
1a 1a+2a
+
3a
2a
(0.1
DCM, blue LEDs,
overnight
0.5
0
rt,
90%
yield
220.00
270.00
320.00
370.00
420.00
470.00
520.00
Wavelength (nm)
Next, we turned our attention to the mechanistic study of
the first part starting with evaluation of the role of
aryldiazonium salt 2. It has been well known that aryldiazonium
salt 2 can act as an oxidant as it often does in photoredox
catalysis. However, the redox potential of 1a and 2a did not
support its direct oxidation pathway (see cyclic voltammetry at
Chapter 9 in the Supporting Information). Upon mixing 1a and
2a, a significant color change was observed at the beginning of
the reaction, implying the formation of an electron
donor-accepter (EDA) complex.[7,10] This observation was further
supported by appearance of a new absorption peak upon mixing
1a and 2a in DCM solution in their electronic spectra (Figure 1).
According to their absorption spectra, neither 1a nor 2a can be
effectively photoexcited by the broad-band blue LED light
(380−530 nm). Therefore, it suggested that the radical cation
generated upon the visible light photoexcitation of the formed
EDA complex followed by a subsequent tandem cyclization, ring
opening and nucleophilic attack of MeOH accounted for the
formation of 3a. Moreover, the reaction proceeded smoothly
even with a catalytic amount of 2a, suggesting that 2a might be
an initiator in this reaction. In a catalytic sense, the reaction
should therefore be possible to proceed through a chain
transfer or an autocatalytic process. The autocatalysis could be
easily ruled out since 3a itself did not catalyze or accelerate the
transformation of 1a to 3a under the standard conditions
Figure 2. (a) A direct autocatalytic examination experiment of 1a to 3a.
(b) Autocatalytic examination experiment of 1a to 3a under the reaction
conditions. (c) The kinetic experiments from 1a to 3a. (d) Light/dark
cycle experiments for the templet reaction from 1a to 3a.
(a)
(b)
Autocatalysis
experiment
1a to
from substrate
intermediate
3a
O
Ph
40
35
30
25
20
15
10
5
Ph
0% 3a loading
20% 3a loading
+
no reaction
MeOH
(2.0 eq),
blue LEDs
DCM
OH
Ph
Ph
Ph
1a
3a
eq)
(0.2
0
0
5
10
15
20
25
30
35
40
Time(min)
(c)
(d)
salt
Kinetic study of different concentration of
Dark-light
experiment
aryldiazonium
3a
--------from
1a to
1a
to intermediate 3a
substrate
intermediate
substrate
from
120
120
100
80
60
40
20
0
100
80
60
40
20
0
10% eq. 2a
20% eq. 2a
50% eq. 2a
0
10
20
30
40
0
10
20
30
40
50
60
70
80
Time (min)
Time (min)
Notably, the allenic product 3a is a bright yellow solid,
indicating the possibility on the absorption of visible light
irradiation. As expected, the UV-vis absorption spectrum of 3a
showed a broad absorption band over 400 nm (Figures 3a and
3b). On the basis of its absorption spectrum, fluorescence
quenching experiment of 3a demonstrated that its excited state
could be quenched by aryldiazonium salt 2a, indicating that a
SET process or an energy transfer could take place between 3a
and 2a (Figure 3c). Thus, we assumed that the second reaction
pathway might proceed via a SET process to generate the
radical cation of 3a under the reaction condition. In a seminal
work by Wu and his coworkers, it has been shown that the
allenic moiety of 3a could be oxidized to radical cation followed
(Figures 2a and 2b). Furthermore,
a series of control
experiments were conducted to investigate the reaction
mechanism. The kinetic experiments on reaction rates showed
that the concentration of 2a could affect the reaction rate and
the reaction was accelerated if using 0.2 or 0.5 equiv of 2a.
Meanwhile, the shapes of their kinetic curves also implied the
existence of an induction period and a chain process (Figure 2c).
Next, the light-dark interval experiment confirmed that constant
www.cjc.wiley-vch.de
© 2020 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2019, 37, XXX－XXX
This article is protected by copyright. All rights reserved.

Running title
Chin. J. Chem.
by a nucleophilic attack.[11] Indeed, while using catalytic amount
of 2a, the reaction could proceed smoothly from 3a to 4a,
suggesting a similar chain process or autocatalytic pathway. The
measurement on the fluorescence decay of compound 3a
indicated that its fluorescence lifetime is 0.80 ns (see page S26
in the Supporting Information). The control experiments
showed that 4a itself could not catalyze the transformation of
3a to 4a, and upon treating 3a with 4a (10 mol%) under the
reaction conditions, no accelerated transformation could be
realized from 3a to 4a, thereby excluding the autocatalytic
pathway (Figures 3d and 3e). Therefore, the second reaction
pathway might have a similar chain process as that of the first
pathway. To explain the formation of product 4a, we
hypothesized that the radical cation of 3a was quenched by an
intramolecular Friedel-Crafts-type cyclization to generate a
spirobi[indene] skeleton fused alkenyl radical, which underwent
a hydrogen transfer to afford the final product.
Scheme 3 The deuterium labeling experiments.
Ph
100% CD3 content
D
D
O
Ph
N2BF4
CD3OD
Ph
Ph
OH
+
D
H/D
rt
CD2Cl2, D
blue LEDs
2O,
15% D content
Ph
O
1a
2a
-
4a
d
3 (79% yield)
Ph
Ph
blue LEDs
O
+
2a
O
rt
CD2Cl2,
Ph
Ph
Ph
3a
4a
(92% yield)
without deuterium
incorpoartion
Ph
Ph
O
blue LEDs
commercially
H/D
+
2a
O
rt
available DCM,
<10% D content
Ph-d5
D
D
Ph-d5
D
4a
Ph-d5
D
(88% yield)
3a
[D]-
Ph
O
blue LEDs
DCM,
H/D
Figure 3. (a) UV-vis absorption spectrum of 3a. (b) The physical
property of 3a. (c) The fluorescence quenching experiment. (d) A direct
autocatalytic examination experiment of 3a to 4a. (e) Autocatalytic
examination experiment of 3a to 4a under the reaction conditions.
+
2a
3a
[D]-
D content
rt
60%
Ph-d5
D
anhydrous
D
D
4a
D
(90% yield)
UV-Vis-absorption
of intermediate
(a)
spectroscopy
Fluorescence
Another key issue is to illustrate the way of alkenyl radical
to capture a H atom to produce 4a, whether it comes from a
HAT process or a SET process. To clarify this point, a series of
deuterium labeling experiments were carried out. As shown in
Scheme 3, when the reaction was performed by using 1a as the
starting material in CD2Cl2 in the presence of deuterium oxide
(5.0 equiv) and CD3OD (2.0 equiv), only 15% of the alkenyl
hydrogen in product 4a was deuterated. In the meantime, no
deuterium incorporation was observed when the reaction was
carried out in CD2Cl2 using intermediate 3a as the starting
material. Next, we prepared the deuterated 3a to further
investigate the hydrogen source and found that when the
reaction was carried out in anhydrous DCM, 4a was obtained in
90% yield along with 60% deuterium incorporation; however,
when the reaction was directly performed in commercially
available DCM, 4a was formed in 88% yield without significant
deuterium incorporation (< 10% D content), due to the higher
water content (0.035%) of commercially available DCM (see Karl
Fischer analytic result in the Supporting Information). These
results suggested that the H atom is derived from an
electrophilic addition pathway rather than a HAT process.
Meanwhile, a kinetic isotope experiment gave a kH:kD = 0.73,
also indicating an electrophilic pathway in the hydrogen transfer
process (Figure 4a). In addition, the intermolecular HAT
between alkenyl radical and the phenyl group in 3a could be
also ruled out, suggesting a complete proton transfer process.
More importantly, the light-dark interval experiment confirmed
that constant illumination of light is an indispensable element
for formation of 4a from allenic intermediate 3a (Figure 4b).
This experimental result may validate that the photoexcitation
of 3a to 3a* is an essential element for the chain transfer
process. Furthermore, the kinetic experiments illustrated that
the reaction rate was not related to the concentration of 2a
from reaction pathway of 3a to 4a, demonstrating that the rate
of SET between 3a* and 2a is much slower than that of 3a* and
(c)
quenching experiment
(b)
3a
8000
7000
6000
5000
4000
3000
2000
1000
0
3
3a
2.5
2
2a
3a+2a
1.5
1
0.5
0
220.00
270.00
320.00
370.00
420.00
470.00
520.00
Wavelength (nm)
420
440
460
480
500
520
540
560
580
600
Wavelength (nm)
(d)
Autocatalysis
from intermediate
(e)
experiment
3a to
4a
product
16
14
12
10
8
3a
MeOH
DCM, blue LEDs
+
eq)
(2.0
no reaction
4a
eq)
(0.2
0% 4a loading
6
4
10% 4a loading
2
0
0
10
20
Time(min) 30
40
50
Chin. J. Chem. 2019, 37, XXX－XXX
© 2019 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
This article is protected by copyright. All rights reserved.

First author et al.
Report
alkenyl radical species (Figure 4c). The quantum yield of this
process was measured to be 0.5, which implied the chain
process without light irradiation is not a dominant process,
partially supporting the chain process with the continuous light
irradiation (see page S16 in the Supporting Information). The
similar shape of the kinetic curves suggested the existence of a
similar induction period and chain process as that of the first
reaction pathway.
pervious results, a plausible reaction mechanism for this novel
process is outlined in Scheme 4. The visible light irradiation of
an in situ generated electron donor-accepter (EDA) complex
between propargyl alcohol-tethered alkylidenecyclopropane 1
and aryldiazonium salt 2 would generate a radical cation I via a
SET event, which underwent a cyclization to give intermediate
II. The cyclopropane in intermediate II underwent
a
ring-opening process upon nucleophilic attack of methanol to
deliver the corresponding radical intermediate III, and the
release of water leads to a radical cation IV. It can accept an
electron from another molecule of propargyl alcohol-tethered
alkylidenecyclopropane 1 to give the indene fused allenic
product 3. The two SET processes constituted the first chain
process. Visible light direct irradiation of 3 could produce a
excited 3* species, which underwent another SET event with
aryldiazonium salt 2 to afford a radical cationic species V. Once
V was formed, it would rapidly undergo an intramolecular
Friedel-Crafts reaction to give a cyclized radical intermediate VI
along with the release of a proton. At this stage, another SET
process could take place between VI and the excited 3* to
afford V and the alkenyl anion VII, which captured a proton to
afford the desired spirobi[indene] derivative 4 (path a).
However, we could not exclude the possiblity of a direct PCET
from VI to 4 without the formation of intermeidate VII at the
present stage (path b).6 The two SET processes constituted the
second chain process.
Figure 4. (a) Experiment of kinetic isotope effect; (b) Light/dark cycle
experiments for the templet reaction of 3a to 4a; (c) The kinetic
experiment from 3a to 4a.
(a)
O
O
Kinetic isotope effect
experiment
Ph
90
80
70
60
50
40
30
20
10
0
Ph
Ph
N2BF4
blue LEDs
CH2Cl2
+
[D]-3a
3a
R² = 0.9716
Ph
O
Linear ([D]-3a)
Linear (3a)
Ph
2a
3a
4a
R² = 0.9946
O
O
Ph
blue LEDs
CH2Cl2
+
-d
Ph
2a
Ph
5
Ph-d5
Ph-d5
=
k
H/kD 0.73
D
0
50
100
150
200
250
3a
-10
[D]-
Time (min)
D
D
D
(b)
salt
(c)
study
Dark-light
intermediate 3a to
Kinetic
of different of
concentration
experiment
aryldiazonium
4a
3a to
from intermediate
4a
from
product
product
50
45
40
35
30
25
20
15
10
5
70
60
50
40
30
20
10
0
20% eq. 2a
50% eq. 2a
100% eq. 2a
0
50
100
150
200
0
0
20
40
60
80
100
Time (min)
Time (min)
On the basis of above mechanistic investigations and the
Scheme 4. Proposed reaction mechanism
*
Ar
3*
Ar
OH
O
1
b
path
PCET
H2O
a
path
SET
SET
Ar
IV
Ar
Ar
Ar
Ar
H+
SET
Ar
1
OH
ArN2BF4
SET
Ar
OH
O
PIAR
A
PIAR
B
cycle
Ar
cycle
H
Ar
3
I
ArN2BF4
2
V
4
OH2
VII
Ar
III
electron-donor-acceptor
complex
(EDA)
OH
Ar
Ar
Ar
H
MeOH
VI
II
with a photoactive substrate in organic synthesis. The utilization
of this novel synthetic method for the synthesis of natural
products or pharmaceutical molecules is currently under
investigation.
Conclusions
In summary, we have disclosed the reaction pathway to
rapidly construct spirobi[indene] skeletons, and two
a
consequent chain processes has been suggested. This process
has been established through the detailed mechanistic
investigations. This unusual process occurs, through utilizing
photoactive substrate in chain process with visible light
irradiation. Upon photo-irradiation, the redox-active
intermediate can be generated as radical ion or the substrate
can be excited to the singlet or triplet state to take part in the
following chain transfer process. To the best of our knowledge,
this is the unique example of a photo-induced chain process
Supporting Information
The supporting information for this article is available on the
WWW under https://doi.org/10.1002/cjoc.2020xxxxx.
www.cjc.wiley-vch.de
© 2020 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2019, 37, XXX－XXX
This article is protected by copyright. All rights reserved.

Running title
Chin. J. Chem.
photocatalysis of [2+2] styrene cycloadditions by energy transfer. Angew.
Chem. Int. Ed. 2012, 51, 10329-10332; (g) Zou, Y.-Q.; Duan, S.-W.; Meng,
X.-G.; Hu, X.-Q.; Gao, S.; Chen, J.-R.; Xiao, W.-J. Visible light induced
intermolecular [2+2]-cycloaddition reactions of 3-ylideneoxindoles through
energy transfer pathway. Tetrahedron 2012, 68, 6914-6919; (h) Alonso, R.;
Bach, T. A chiral thioxanthone as an organocatalyst for enantioselective
[2+2] photocycloaddition reactions induced by visible light. Angew. Chem.
Int. Ed. 2014, 53, 4368-4371; (i) Liu, Q.; Zhu, F.-P.; Jin, X.-L.; Wang, X.-J.;
Chen, H.; Wu, L.-Z. Visible-light-driven intermolecular [2+2] cycloadditions
between coumarin-3-carboxylates and acrylamide analogs. Chem. Eur. J.
2015, 21, 10326-10329; (j) Blum, T. R.; Miller, Z. D.; Bates, D. M.; Guzei, I.
A.; Yoon, T. P. Enantioselective photochemistry through lewis
acid-catalyzed triplet energy transfer. Science 2016, 354, 1391-1395; (k)
Tröster, A.; Alonso, R.; Bauer, A.; Bach, T. Enantioselective intermolecular
[2+2] photocycloaddition reactions of 2(1H)-quinolones induced by visible
light irradiation. J. Am. Chem. Soc. 2016, 138, 7808-7811; (l) Zhao, J.;
Brosmer, J. L.; Tang, Q.; Yang, Z.; Houk, K. N.; Diaconescu, P. L.; Kwon, O.
Intramolecular crossed [2+2] photocycloaddition through visible
light-induced energy transfer. J. Am. Chem. Soc. 2017, 139, 9807-9810; (m)
Miller, Z. D.; Lee, B. J.; Yoon, T. P. Enantioselective crossed
photocycloadditions of styrenic olefins by lewis acid catalyzed triplet
sensitization, Angew. Chem. Int. Ed. 2017, 56, 11891-11895; (n) Tan, W.;
Wang, C.; Jiang, X. Visible-Light-Mediated C(sp3)-H Thiocarbonylation for
Thiolactam Preparation with Potassium Sulfide, Chinese J. Chem. 2019, 37,
1234-1238; (o) Feng, J.; Li, B.; Jiang, J.; Zhang, M.; Ouyang, W.; Li, C.; Fu, Y.;
Gu, Z. Visible Light Accelerated Vinyl C-H Arylation in Pd-Catalysis:
Application in the Synthesis of ortho Tetra-substituted Vinylarene
Atropisomers, Chinese J. Chem. 2018, 36, 11-14; (p) Wang, D.; Zhang, L.;
Luo, S. Visible Light Promoted β-C-H Alkylation of β-Ketocarbonyls via a
β-Enaminyl Radical Intermediate, Chinese J. Chem. 2018, 36, 311-320; (q)
Yuan, Y.; Dong, W.; Gao, X.; Xie, X.; Curran, D. P.; Zhang, Z.
Visible-Light-Induced Radical Cascade Cyclization: Synthesis of
(20S)-Camptothecin, SN-38 and Irinotecan. Chinese J. Chem. 2018, 36,
1035-1040; (r) Li, C.; Qi, Z.-C.; Yang, Q.; Qiang, X.-Y.; Yang, S.-D.
Visible-Light-Catalyzed Phosphonation-Annulation: An Efficient Strategy to
Synthesize β-Phosphonopyrrolidines and β-Phosphonolactones, Chinese J.
Chem. 2018, 36, 1052-1058; (s) Yang, B.; Ren, X.; Shen, X.; Li, T.; Lu, Z.
Visible Light-Promoted Three-Component Carboazidation of Unactivated
Alkenes with TMSN3 and Acrylonitrile, Chinese J. Chem. 2018, 36,
1017-1023; (t) Yu, W.; Ouyang, Y.; Xu, X.-H.; Qing, F.-L. Visible Light-Induced
Methoxycarbonyldifluoromethylation of Trimethylsilyl Enol Ethers and
Allyltrimethylsilanes with FSO2CF2CO2Me, Chinese J. Chem. 2018, 36,
1024-1030.
Acknowledgement
We are grateful for the financial support from the Strategic
Priority Research Program of the Chinese Academy of Sciences
(Grant No. XDB20000000), the National Natural Science
Foundation of China (21421091, 21372250, 21121062,
21302203, 20732008, 21772037, 21772226, 21861132014 and
91956115)
References
[1]
(a) Nicewicz, D. A.; MacMillan, D. W. C. Merging photoredox catalysis
with organocatalysis: the direct asymmetric alkylation of aldehydes. Science
2008, 322, 77-80; (b) Creutz, S. E.; Lotito, K. J.; Fu, G. C.; Peters, J. C.
Photoinduced ullmann C-N coupling: demonstrating the viability of a radical
pathway. Science 2012, 338, 647-651; (c) Zhang, M.; Xie, J.; Zhu, C. A
general deoxygenation approach for synthesis of ketones from aromatic
carboxylic acids and alkenes. Nat. Commun. 2018, 9, 3517-3526; (d) Prier, C.
K.; Rankic, D. A.; MacMillan, D. W. C. Visible light photoredox catalysis with
transition metal complexes: applications in organic synthesis. Chem. Rev.
2013, 113, 5322-5363; (e) Tellis, J. C.; Kelly, C. B.; Primer, D. N.; Jouffroy, M.;
Patel, N. R.; Molander, G. A. Single-electron transmetalation via
photoredox/nickel dual catalysis: unlocking a new paradigm for sp(3)-sp(2)
cross-coupling. Acc. Chem. Res. 2016, 49, 1429-1439; (f) Zhou, Q.-Q.; Zou,
Y.-Q.; Lu, L.-Q.; Xiao, W.-J. Visible-light-induced organic photochemical
reactions through energy-transfer pathways. Angew. Chem. Int. Ed. 2019,
58, 1586-1604; (g) Nguyen, J. D.; D'Amato, E. M.; Narayanam, J. M.;
Stephenson, C. R. J. Engaging unactivated alkyl, alkenyl and aryl iodides in
visible-light-mediated free radical reactions. Nat. Chem. 2012, 4, 854–859;
(h) Hari, D. P.; König, B. The photocatalyzed meerwein arylation: classic
reaction of aryl diazonium salts in a new light. Angew. Chem. Int. Ed. 2013,
52, 4734-4743; (i) Kärkäs, M. D.; Jr., Porco, J. A.; Stephenson, C. R. J.
Photochemical approaches to complex chemotypes: applications in natural
product synthesis. Chem. Rev. 2016, 116, 9683-9747; (j) Liu, Q.; Wu, L.-Z.
Recent advances in visible-light-driven organic reactions. Natl. Sci. Rev.
2017, 4, 359-380; (k) Xuan, J.; Xiao, W.-J. Visible-light photoredox catalysis.
Angew. Chem. Int. Ed. 2012, 51, 6828-6838; (l) Xuan, J.; Hea, X.-K.; Xiao,
W.-J. Visible light-promoted ring-opening functionalization of
three-membered carbo- and heterocycles. Chem. Soc. Rev. 2020, 49,
2546-2556; (m) Cai, B.-G.; Xuan, J.; Xiao, W.-J. Visible light-mediated C-P
bond formation reactions Sci. Bull. 2019, 64, 337-350; (n) Li, S.; Xiang, S.-H.;
Tan, B. Chiral Phosphoric Acid Creates Promising Opportunities for
Enantioselective Photoredox Catalysis. Chinese J. Chem. 2020, 38, 213-214.
(a) Milligan, J. A.; Phelan, J. P.; Badir, S. O.; Molander, G. A. Alkyl
carbon-carbon bond formation by nickel/photoredox cross-coupling.
Angew. Chem. Int. Ed. 2019, 58, 6152-6163; (b) Wilger, D. J.; Grandjean, J.
M.; Lammert, T. R.; Nicewicz, D. A. The direct anti-markovnikov addition of
mineral acids to styrenes. Nat. Chem. 2014, 6, 720-726. (c) Corcoran, E. B.;
Pirnot, M. T.; Lin, S.; Dreher, S. D.; DiRocco, D. A.; Davies, I. W.; Buchwald, S.
L.; MacMillan, D. W. C. Aryl amination using ligand-free Ni(II) salts and
photoredox catalysis. Science 2016, 353, 279-283; (d) Ghosh, I.; Ghosh, T.;
Bardagi, J. I.; König, B. Reduction of aryl halides by consecutive visible
light-induced electron transfer processes. Science 2014, 345, 725-728; (e)
Kainz, Q. M.; Matier, C. D.; Bartoszewicz, A.; Zultanski, S. L.; Peters, J. C.; Fu,
G. C. Asymmetric copper-catalyzed C-N cross-couplings induced by visible
light. Science 2016, 351, 681-684; (f) Lu, Z.; Yoon, T. P. Visible light
[3]
[4]
(a) Perry, I. B.; Brewer, T. F.; Sarver, P. J.; Schultz, D. M.; DiRocco, D. A.;
MacMillan, D. W. C. Direct arylation of strong aliphatic C-H bonds. Nature
2018, 560, 70-75; (b) Flores, D. M.; Schmidt, V. A. I. Intermolecular 2+2
carbonyl-olefin photocycloadditions enabled by Cu(I)-norbornene MLCT. J.
Am. Chem. Soc. 2019, 141, 8741-8745.
(a) Hu, A.; Chen, Y.; Guo, J. J.; Yu, N.; An, Q.; Zuo, Z. Cerium-catalyzed
formal cycloaddition of cycloalkanols with alkenes through dual
photoexcitation. J. Am. Chem. Soc. 2018, 140, 13580-13585; (b) Heitz, D. R.;
Tellis, J. C.; Molander, G. A. Photochemical nickel-catalyzed C-H arylation:
synthetic scope and mechanistic investigations. J. Am. Chem. Soc. 2016,
138, 12715-12718; (c) Zhang, K.; Chang, L.; An, Q.; Wang, X.; Zuo, Z.
Dehydroxymethylation of alcohols enabled by cerium photocatalysis. J. Am.
Chem. Soc. 2019, 141, 10556-15564.
[2]
Chin. J. Chem. 2019, 37, XXX－XXX
© 2019 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
This article is protected by copyright. All rights reserved.

First author et al.
Report
[5]
[6]
(a) Nicewicz, D. A.; Nguyen, T. M. Recent applications of organic dyes as
methylenecyclopropanes and vinylidenecyclopropanes, Acc. Chem. Res.
2014, 47, 913-924; (c) Yu, L.-Z.; Chen, K.; Zhu, Z.-Z.; Shi, M. Recent advances
in the chemical transformations of functionalized alkylidenecyclopropanes
(FACPs), Chem. Commun. 2017, 53, 5935-5945; (d) Zhu, Z.-Z.; Chen, K.; Yu,
L.-Z.; Tang, X.-Y.; Shi, M. Copper(I)-catalyzed intramolecular
trifluoromethylation of methylenecyclopropanes, Org. Lett., 2015, 17,
5994-5997; (e) Zhang, X.-Y.; Ning, C.; Long, Y.-J.; Wei, Y.; Shi M.
Visible-light-mediated decarboxylative tandem carbocyclization of
acrylamide-attached alkylidenecyclopropanes: access to polycyclic
benzazepine derivatives, Org. Lett. 2018, 20, 4686-4690.
photoredox catalysts in organic synthesis. ACS Catalysis 2014, 4, 355-360;
(b) Hamilton, D. H.; Nicewicz, D. A. Direct catalytic anti-markovnikov
hydroetherification of alkenols. J. Am. Chem. Soc. 2012, 134, 18577-18580;
(c) Nguyen, T. M.; Nicewicz, D. A. Anti-markovnikov hydroamination of
alkenes catalyzed by an organic photoredox system. J. Am. Chem. Soc.
2013, 135, 9588-9591.
(a) Dirocco, D. A.; Dykstra, K.; Krska, S.; Vachal, P.; Conway, D. V.;
Tudge, M. Late-stage functionalization of biologically active heterocycles
through photoredox catalysis. Angew. Chem. Int. Ed. 2014, 53, 4802-4806;
(b) Yayla, H. G.; Wang, H.; Tarantino, K. T.; Orbe, H. S.; Knowles, R. R.
Catalytic ring-opening of cyclic alcohols enabled by PCET activation of
strong O-H bonds. J. Am. Chem. Soc. 2016, 138, 10794-10797; (c) Choi, G. J.;
Knowles, R. R. Catalytic alkene carboaminations enabled by oxidative
proton-coupled electron transfer. J. Am. Chem. Soc. 2015, 137, 9226-9229;
(d) Tarantino, K. T.; Liu, P.; Knowles, R. R. Catalytic ketyl-olefin cyclizations
enabled by proton-coupled electron transfer. J. Am. Chem. Soc. 2013, 135,
10022-10025.
(a) Mulliken, R. S. Molecular compounds and their spectra. II, J. Am.
Chem. Soc. 1952, 74, 811-824; (b) Foster, R. J. Phys. Chem. Electron
donor-acceptor complexes, 1980, 84, 2135-2141. (c) Cao, Z.-Y.; Ghosh, T.;
Melchiorre, P. Enantioselective radical conjugate additions driven by a
photoactive intramolecular iminium-ion-based EDA complex, Nat. Comm.
2018, 9, 3274; (d) Fu, M.-C.; Shang, R.; Zhao, B.; Wang, B.; Fu, Y.
Photocatalytic decarboxylative alkylations mediated by triphenylphosphine
and sodium iodide. Science 2019, 363, 1429-1434.
[9]
Liu, J.; Li, Q.; Wei, Y.; Shi, M. Visible light induced cyclization to
spirobi[indene] skeletons from functionalized alkylidienecyclopropanes.
Org. Lett. 2020, 22, 2494-2499.
[10]
(a) S. V. Rosokha, J. K. Kochi, Fresh Look at Electron-transfer
mechanisms via the donor/acceptor bindings in the critical encounter
complex, Acc. Chem. Res. 2008, 41, 641-653; (b) M. Nappi, G. Bergonzini, P.
Melchiorre, Metal-free photochemical aromatic perfluoroalkylation of
α-cyano arylacetates, Angew. Chem. Int. Ed. 2014, 53, 4921-4925
Wei, K.; Luo, K.; Liu, F.; Wu, L.; Wu, L.-Z. Visible-light-driven selective
alkenyl C-P bond cleavage of allenylphosphine oxides. Org. Lett. 2019, 21,
1994-1998.
[7]
[11]
(The following will be filled in by the editorial staff)
Manuscript received: XXXX, 2020
Manuscript revised: XXXX, 2020
Manuscript accepted: XXXX, 2020
Accepted manuscript online: XXXX, 2020
Version of record online: XXXX, 2020
[8]
(a) Liu, J.; Liu, R.; Wei, Y.; Shi, M. Recent developments in cyclopropane
cycloaddition reactions, Trends in Chem., 2019, 1, 779-793; (b) Zhang, D.-H.;
Tang, X.-Y.; Shi, M. Gold-catalyzed tandem reactions of
www.cjc.wiley-vch.de
© 2020 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2019, 37, XXX－XXX
This article is protected by copyright. All rights reserved.

Running title
Chin. J. Chem.
Entry for the Table of Contents
Page No.
Title: Mechanistic studies on propargyl
alcohol-tethered alkylidenecyclopropane with
aryldiazonium salt initiated by visible light
Ar
Ar
ArN2BF4
Ar
OH
Chain A
Chain B
Ar
ArN2BF4
electron-donor-acceptor
complex
*
(EDA)
Ar
OH
Ar
1) KIE effect
2)
3
)
Kinetic study
Spectorscopic analysis
The plausible reaction mechanism of a visible-light photo-induced reaction for rapidly constructing
spirobi[indene]s has been established through systematically mechanistic studies.
Jiaxin Liu,a Yin Wei*,a and Min Shi,a,b
Chin. J. Chem. 2019, 37, XXX－XXX
© 2019 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
This article is protected by copyright. All rights reserved.