Visible- And UV-Light-Induced Decarboxylative Radical Reactions of Benzoic Acids Using Organic Photoredox Catalysts

Article abstract of DOI:10.1021/acs.joc.0c00055

Photoinduced decarboxylative radical reactions of benzoic acids with electron-deficient alkenes, diborane, and acetonitrile under organic photoredox catalysis conditions and mild heating afforded adducts, arylboronate esters, and the reduction product, respectively. The reaction is thought to involve single-electron transfer promoted the generation of aryl radicals via decarboxylation. A diverse range of benzoic acids were found to be suitable substrates for this photoreaction. Only our two-molecule organic photoredox system can work well for the direct photoinduced decarboxylation of benzoic acids.

Full text of DOI:10.1021/acs.joc.0c00055

Subscriber access provided by NATIONAL UNIV OF SINGAPORE
Article
Visible and UV-light-induced Decarboxylative Radical Reactions
of Benzoic Acids Using Organic Photoredox Catalysts
Suzuka Kubosaki, Haruka Takeuchi, Yutaka Iwata, Yosuke Tanaka,
Kazuyuki Osaka, Mugen Yamawaki, Toshio Morita, and Yasuharu Yoshimi
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.0c00055 • Publication Date (Web): 15 Mar 2020
Downloaded from pubs.acs.org on March 16, 2020
Just Accepted
“Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted
online prior to technical editing, formatting for publication and author proofing. The American Chemical
Society provides “Just Accepted” as a service to the research community to expedite the dissemination
of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in
full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully
peer reviewed, but should not be considered the official version of record. They are citable by the
Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore,
the “Just Accepted” Web site may not include all articles that will be published in the journal. After
a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web
site and published as an ASAP article. Note that technical editing may introduce minor changes
to the manuscript text and/or graphics which could affect content, and all legal disclaimers and
ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or
consequences arising from the use of information contained in these “Just Accepted” manuscripts.
is published by the American Chemical Society. 1155 Sixteenth Street N.W.,
Washington, DC 20036
Published by American Chemical Society. Copyright © American Chemical Society.
However, no copyright claim is made to original U.S. Government works, or works
produced by employees of any Commonwealth realm Crown government in the course
of their duties.

Page 1 of 9
The Journal of Organic Chemistry
1
2
3
4
5
6
7
8
9
Visible and UV-light-induced Decarboxylative Radical
Reactions of Benzoic Acids Using Organic Photoredox Catalysts
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Suzuka Kubosaki, Haruka Takeuchi, Yutaka Iwata, Yosuke Tanaka, Kazuyuki Osaka, Mugen
Yamawaki, Toshio Morita, Yasuharu Yoshimi*
Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, University of Fukui, 3-9-1 Bunkyo,
Fukui 910-8507, Japan
Supporting Information Placeholder
photoinduced electron transfer (PET) (Figure 1b).16-22 The process
is initiated by PET from Phen to DCB, generating the radical
cation of Phen, which oxidizes the alkyl carboxylate ions to form
alkyl carboxy radicals. These alkyl carboxy radicals are smoothly
decarboxylated to generate the corresponding alkyl radicals,
ABSTRACT: Photoinduced decarboxylative radical reactions of
benzoic acids with electron-deficient alkenes, diborane, and
acetonitrile under organic photoredox catalysis conditions and
mild heating afforded adducts, arylboronate esters, and the
reduction product, respectively. The reaction is thought to involve
single-electron transfer promoted generation of aryl radicals via
decarboxylation. A diverse range of benzoic acids were found to
be suitable substrates for this photoreaction. Only our two-
molecule organic photoredox system can work well for the direct
photoinduced decarboxylation of benzoic acids.
Figure 1. a.Decarboxylation of benzoic acids using
a
photoredox catalyst. b.Photoinduced decarboxylative radical
reactions of carboxylic acids (previous work 1). c.Photoinduced
deboronative radical addition of arylboronic acids to electron-
deficient alkenes (previous work 2). d.Decarboxylative radical
reactions with BP and DCN or DCA (this work).
a. Decarboxylation of benzoic acids with photoredox catalyst
Introduction

h
CO2
CO2H
+ OH-
CO2
not reported
– CO2
Photoinduced decarboxylative radical reactions of carboxylic
acids in the presence of a photoredox catalyst constitute a
powerful and environment-friendly method for the synthesis of
polymers1,2 and complex organic molecules3-9. This strategy has
several advantages: (1) carboxylic acids occur widely in nature in
addition to being inexpensive and easy to store and handle; (2)
decarboxylation releases only CO2, which is nonflammable,
nontoxic, and easily removable from the reaction medium; (3)
light is a traceless reagent, and (4) harsh reaction conditions such
as high temperature and pressure are not required. However, the
substrates used in this transformation are limited to aliphatic
carboxylic acids, which generate alkyl radicals. Aryl radicals 2 are
useful reactive intermediates in reactions that introduce aryl
groups. However, benzoic acids cannot be employed as substrates
for generating 2 because the rate (k = 106 s-1) of decarboxylation
of aryl carboxy radical 1 is lower than that (k = 109 s-1) of the
alkyl carboxy radical (Figure 1a).10 Typically, the generation of 2
requires the use of stoichiometric amounts of toxic metals (Sn, Cu,
Ag) and/or sensitive substrates such as aryl halides and aryl
diazonium salts, as well as harsh reaction conditions such as high
temperature.11,12 In particular, diazonium salts are often explosive
and highly toxic, and diazonium salts bearing sensitive
substituents cannot be used as substrates for generating aryl
radicals. Thus, one of the recent challenges in organic chemistry
is decarboxylation of benzoic acids to generate aryl radicals under
mild photoredox catalysis conditions.13-15
Photoredox
catalyst
R
Decarbo
-xylation
R
R
2
R
1
Benzoic acids
Benzates
Aryl radicals
Aryl carboxy radicals
aryl, k = 106 s-1
alkyl, k = 109 s-1
b. Previous work 1
Phen*
DCB

h
Phen;
DCB;
NC
CN
Phen
- e-
Phen
– CO2
DCB
O
O
O
– H
+ X
Alkyl radicals
R
X
R
Decarbo
-xylation
R
OH
R
O
R
O
X = H, D, CH2CH2CN,
CH(CO2CH3)NHOBn,
C6H4CN, et. al.
c. Previous work 2
B(OH)3
Phen, DCB
B(OH)2
+ OH-
R'

h
+
R'
R
R
R
2
R
Arylboronic acids Arylborates
Aryl radicals
d. This work

h
BP, DCN or DCA
CO2H
X
30 o
C
+ X
CH3CN/H2O=9:1
R
R
R
2
Benzoic acids
Aryl radicals
We have previously described photoinduced decarboxylative
radical reactions of aliphatic carboxylic acids, which involves
decarboxylation of the alkyl carboxy radicals produced under UV
light irradiation in the presence of organic photoredox catalysts
such as phenanthrene (Phen) and 1,4-dicyanobenzene (DCB) via
DCN;
BP;
NC
CN
DCA;
NC
CN
with UV light (313 nm)
with visible light (405 nm)
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 2 of 9
which then react with a variety of radical acceptors to provide the
mM) and 5 equiv. of 4A (25 mM) with BP (2 mM, 40 mol%) and
DCA (2 mM, 40 mol%) for 3 h at 30 °C under irradiation by a
blue LED (405 nm, 18 W) also afforded 5aA in a decreased yield
(42%, entry 13; the photochemical conditions under visible-light
irradiation are illustrated in Method II). The low yield of 5aA
was attributed to the low solubility of DCA in the aqueous
acetonitrile solution, but the visible light-induced decarboxylation
of 3a using BP and DCA was successful. Similar photoreactions
with typical visible light-induced redox catalysts such as Ir(ppy)3,
Ir[dF(CF3)ppy]2(dtbbpy)+, and Fukuzumi catalyst5-6,8,28 by
Method II failed to provide 5aA and 3a was recovered almost
completely (entries 14–16), although the Fukuzumi catalyst has a
higher oxidation potential (+2.06 V)28 than BP. Thus, only our
two-molecule photoredox system is suited for the photoinduced
decarboxylation of benzoic acid.
1
2
3
4
5
6
7
8
respective products in high yields. However, our attempts toward
the decarboxylation of benzoic acids to generate aryl radicals
under the same photochemical conditions failed, and the benzoic
acids were almost completely recovered. This finding encouraged
us to screen suitable substrates for the generation of aryl radicals
under similar organic photoredox catalysis conditions. We found
that arylboronic acids are promising candidates for aryl radical
precursors via photoinduced deboronation (Figure 1c).23 A careful
reinvestigation revealed that the photoinduced decarboxylative
radical reactions of benzoic acids proceeded well when using a
biphenyl (BP)/1,4-dicyanonaphthalene (DCN) or BP/9,10-
dicyanoanthracene (DCA) system as the organic photoredox
catalyst under UV and visible-light irradiation with mild heating
(30 °C) (Figure 1d).
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Results and Discussion
Initially, we attempted to optimize the reaction conditions by
using benzoic acid 3a and acrylonitrile 4A with organic
photoredox catalysts for the decarboxylation (Table 1). An
aqueous acetonitrile solution (CH3CN/H2O = 9:1, v/v) containing
3a (20 mM), 4A (100 mM), Phen (10 mM, 50 mol%), DCB (10
mM, 50 mol%), and NaOH (20 mM) under an argon atmosphere
for 3 h at room temperature was irradiated (100 W high-pressure
mercury lamp with a Pyrex glass filter; λ > 280 nm, organic
photocatalysts such as Phen or DCN mainly absorb at 313 nm) to
give no formation of adduct 5aA (entry 1). However, when the
solution was heated to 60 °C, excitation occurred under the same
photochemical conditions to give 5aA, albeit in a low yield (9%),
along with some oligomeric materials (entry 2). The low rate of
decarboxylation of 1 necessitates high-temperature conditions,
which promoted radical polymerization. Fortunately, the use of
BP and DCN as photocatalysts improved the yield of 5aA (20%,
entry 3) even at room temperature, and heating at 30 °C gave the
best yield of 5aA (69%, entry 4; photochemical conditions with
UV irradiation are illustrated in Method I). A further increase in
temperature accelerated the polymerization and decreased the
yield of 5aA (entries 5–7). The effect of the concentrations of 4A,
BP, and DCN as well as the type of solvent and base in the
photoreaction of 3a (see Table S1 in SI) followed a similar trend
in the photoreaction of phenylboronic acid,23 wherein a phenyl
radical is the reactive intermediate. The formation of 5aA in the
photoreaction using BP and DCN in the presence of 3 equiv. of
2,2,6,6-tetramethylpiperidin-1-yl)oxidanyl (TEMPO; 60 mM)
under similar conditions was completely disturbed to give a
complex mixture. Nonetheless, the corresponding TEMPO
coupling product, as reported in our previous photoreaction of
phenylboronic acid,23 was not isolated because it was unstable
under the photochemical conditions using DCN.24 These results
suggested the generation of a phenyl radical from 3a via
photoinduced decarboxylation for addition to alkene 4A.
Competitive phenyl radical H-abstraction from CH3CN and
addition to 4A occur during the photoreaction, thereby entailing a
high concentration (100 mM) of alkene for the latter process. The
use of a high alkene concentration makes oligomerization more
efficient, and requires high concentrations of photocatalysts for
preventing oligomerization.23 In the absence of a base (NaOH),
the photoreaction furnished 5aA in a decreased yield (entry 8,
42%). When using naphthalene (oxidation potential: +1.70 V vs.
SCE in acetonitrile),25 1-methylnaphthalene (+1.43 V),25 and Phen
(+1.50 V)25 instead of BP (+1.95 V)26 as the photocatalyst, 5aA
was not formed (entries 9–11), with almost 100% recovery of 3a.
This result indicated that a high oxidation potential of the arene is
required for the decarboxylation of 3a, although the oxidation
potential of the benzoate ion is +1.40 V vs. SCE in acetonitrile.27
In the absence of BP, the photoinduced decarboxylation of 3a did
not proceed (entry 12). The reaction of 3a (5 mM) with NaOH (5
Table 1. Photoinduced decarboxylative radical addition of 3a to
4A.

h , 3 h
CO2H
Photocatalyst (10 mM)
NaOH (20 mM)
CN
+
CN
CH3CN/H2O = 9:1
4A (100 mM)
3a (20 mM)
5aA
5aA
Entry
Photocatalyst Temperature/ºC
Yield of
/%
r.t.
60
r.t.
30
40
50
60
30
30
0
1
2
3
4
Phen, DCB
Phen, DCB
BP, DCN
BP, DCN
BP, DCN
BP, DCN
BP, DCN
BP, DCN
9
20
69 (
50
35
33
42
0
Method I
)
5
6
7
8a
Naphthalene, DCN
9
1-Methyl-
naphthalene, DCN
10
0
30
30
30
30
0
0
11
12
13b
14b
Phen, DCN
DCN
Method II
( )
37
BP, DCA
Ir(ppy)3
30
30
30
0
0
0
15b Ir[dF(CF3)ppy]2(dtbbpy)+
16b Fukuzumi catalyst
b
aIn the absence of NaOH. Photoreaction of 3a (5 mM), 4A (25
mM), NaOH (5 mM), and photocatalyst (2 mM) was carried out
under blue LED (405 nm, 18 W) irradiation for 3 h at 30 °C.
Next, the scope of benzoic acids and alkenes in the photoreaction
was evaluated under the optimized conditions (Method I and II).
The results are summarized in Table 2. Because of the poor
solubility of substrates 3e,f,n,o in the reaction medium, the ratio
of water in the solvent had to be increased. The photoreactions of
benzoic acids 3b–f bearing alkyl groups proceeded efficiently to
afford the corresponding adducts 5bA–fA in moderate yields.
Benzoic acids with strongly electron-donating groups such as the
methoxy
group
(4-methoxybenzoic
acid
and
2,4-
dimethoxybenzoic acid) were unfavorable for PET, and adducts 3
were not formed. However, the introduction of an appropriate
protecting group such as acetyl or Boc onto the phenolic hydroxyl
group of benzoic acids 3g,h facilitated PET-promoted
decarboxylative radical addition to furnish 5gA,hA. Similar
photoreactions of halogenated benzoic acids 3i–k provided the
corresponding adducts 5iA–kA in moderate yields. Moreover,
photoreactions of benzoic acids 3l–n substituted with a para-
electron-withdrawing group (CN, CF3, and CO2CH3) gave slightly
decreased yields because of the low rate of addition of the
ACS Paragon Plus Environment

Page 3 of 9
The Journal of Organic Chemistry
electron-deficient aryl radicals to the electron-deficient alkene 4A.
equiv. of 6, 1.5 equiv. of BP and DCN, without NaOH (Table S2
in SI). This is possibly because back electron transfer (BET) from
the generated radical anion of DCN did not occur to decompose
DCN during the borylation. The photoreactions of benzoic acids 3
bearing an electron-donating or electron-withdrawing substituent
under UV irradiation and the optimized conditions provided
arylboronate esters 7 in moderate yields (Table 3). Visible-light
induced reaction of 1a (2 mM) and 6 (6 mM) with BP (2 mM, 100
mol%) and DCA (2 mM, 100 mol%) also provided 7a in a 38%
yield. A similar trend in the substituent effect was observed for
1
2
3
4
5
6
7
8
In addition, 4-phenylbenzoic acid 3o underwent the photoredox
catalyzed reaction to generate the corresponding adduct 5oA. The
use of 3 equiv. of low electron-deficient alkenes such as t-butyl
acrylate 4B, acrylamide 4C, and phenyl vinyl sulfone 4D instead
of 5 equiv. of 4A led to the formation of the corresponding
adducts 5aB–aD along with oligomeric materials in low yields.
Visible-light-induced reactions (Method II) of 3a,b,j,l with 4A,B
furnished the corresponding adducts 5bA,jA,lA,aB. In particular,
the reaction of 3l gave 5lA (44%) in improved yield after
prolonged irradiation (6 h). The combined results showed that a
wide variety of benzoic acids and alkenes can participate in C–C
bond formation under UV and visible-light irradiation via
photoinduced decarboxylation, and that the yields of the adducts
depend on the electronic nature of the arene ring and alkene
substituents.
the photoreaction with 4.
A secondary photoreaction of
9
halogenated arylboronate ester 7i took place to decrease the yield
of 7i. Thus, commercially available benzoic acids are proven to be
suitable precursors of synthetically useful arylboronate esters.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Table 3. Photoinduced decarboxylative radical borylation of 3
with 6.
Table 2. Scope of benzoic acid and alkene in the photoinduced
decarboxylative radical addition.
h, 6 h, 30 ºC
BP (30 mM)
DCN (30 mM)
O
B
CO2H
O
O
O
O
O
Method I or II
B
B
+

CH3CN/H2O = 9:1
h
, 30 ºC
CO2H
R
3
Photocatalyst
NaOH
R
X
6 (60 mM)
(20 mM)
+
X
7a-o
CH3CN/H2O = 9:1
4
R
4B: X = CO2t-Bu
4C
3a o
-
R
: X = CONH2
5bA-aD
O
B
O
O
B
O
4D: X = SO2Ph
B
B
O
O
O
O
CN
CN
CN
7a: 55% (38%)a
7d: 49%b
7c: 53%b
7b: 44%
O
B
5bA: 61% (38%)a
CN
5dA: 51%
5cA: 43%
O
O
O
B
B
O
O
O
CN
CN
O
Cl
O
7i: 17%b
7e: 45%b
7g: 36%b
O
5fA: 44%b
5gA: 26%
5eA: 42%b
O
O
B
B
CN
Cl
O
O
O
CN
CN
F3C
NC
O
O
Br
7m: 34%b
7l: 38%b
5jA: 48% (45%)a
5iA: 44%
5hA: 48%
O
O
B
CN
CN
CN
B
O
O
O
O
NC
Br
F3C
5lA: 38% (44%)a,d
5mA: 34%
5kA: 50%
7n: 43%b,d
7o: 56%c
CN
CN
aPhotoreaction of 3a (2 mM) and 6 (6 mM) with BP (2 mM) and
DCA (2 mM) was carried out under blue LED (405 nm, 18 W) for
3 h at 30 °C. bIrradiation time is 8 h. cCH3CN/H2O = 8:2.
dCH3CN/H2O = 17:3.
O
O
5nA: 45%c
5oA: 45%b
O
O
O
S
NH2
O
O
To extend this methodology to other reactions and elucidate the
reaction mechanism, photoinduced decarboxylative reduction and
deuteration of 3 were carried out (Scheme 1). The photoreaction
of 3f in the presence of a catalytic amount of BP (5 mM) and
DCN (5 mM) in CH3CN/H2O = 8:2 gave the reduction product 8
in 72% yield. The similar reaction of 3f in CD3CN/H2O = 8:2
afforded the deuteration product d-8 with approximately 91% d-
content, as in the case of arylboronic acids.23 These findings
indicate that in the absence of an electron-deficient alkene and
diboron, the aryl radical intermediate abstracts a hydrogen and
deuterium atom from CH3CN and CD3CN to form the reduction
and deuteration products, respectively, and catalytic amounts of
BP and DCN (25 mol%) is sufficient for the photoinduced
decarboxylation of benzoic acids.
5aC: 25%e
5aB: 39%e (16%)a,f
5aD: 23%e
aYields of 5 in parentheses correspond to the reactions by Method
b
c
d
II. CH3CN/H2O = 8:2. CH3CN/H2O = 17:3. Irradiation time is
6 h. e[4] = 60 mM. f[4B] = 15 mM.
To demonstrate the synthetic utility of the photoinduced
decarboxylation of benzoic acids, borylation of benzoic acids with
bis(pinacolato)diboron 629-31 under similar conditions was
investigated, as the resulting arylboronate esters are frequently
used in Suzuki–Miyaura coupling reactions.32 The optimal
conditions for the photoinduced borylation of 3a with 6 were 3
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 4 of 9
diboron to furnish the corresponding arylboronate esters 7. As
1
2
3
4
5
6
7
8
mentioned, the absence of BET from the radical anion of DCN led
to the decomposition of DCN; hence, 1.5 equiv. of DCN was
required for the reaction. In the absence of radical acceptors,
abstraction of the hydrogen and deuterium atom from CH3CN and
CD3CN by 2 occurred to yield reduction and deuteration products
8 and cyanomethyl radical ( CH2CN). BET from the radical
anion of DCN to the resulting cyanomethyl radical generated a
cyanomethyl anion, followed by protonation to regenerate CH3CN,
as previously reported by us.23,33 Although the direct
photoinduced decarboxylation of benzoic acids proceeded with
catalytic amounts of BP and DCN, increasing the yield of adducts
5 and arylboronate esters 7 required higher concentrations of BP,
DCN, DCA, alkene, and 6.
Scheme 1. Photoinduced decarboxylative reduction and
deuteration of 3f.

h , 6 h, 30 ºC
H(D)
BP (5 mM)
DCN (5 mM)
NaOH (20 mM)
3f (20 mM)
CH3CN/H2O = 8:2
or
CD3CN/H2O = 8:2
8
: 72%
d-8: 46%, d-content 91%
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Additional information about the photoreaction mechanism was
obtained by the fluorescence quenching. The fluorescence of DCN
and DCA in the aqueous CH3CN solution (CH3CN/H2O = 9:1)
excited at 310 and 400 nm were quenched by BP (Figures S2 and
S4), 3a with 1 equiv. of NaOH (Figures S3 and S5), and 4-
methoxybenzoic acid with 1 equiv. of NaOH (Figure S6),
respectively. The rate constants for fluorescence quenching (kq)
of DCN by BP, 3a with NaOH, and 4-methoxybenzoic acid with
NaOH were calculated as 6.77 × 109, 3.31 × 109, and 7.69 × 109
M−1 s−1, respectively. The higher rate of fluorescence quenching
by 4-methoxybenzoic acid with NaOH than that by BP indicates
that PET between DCN and BP is prevented by 4-
methoxybenzoic acid with NaOH. Similarly, the rate constant of
DCA by BP was calculated as 4.55 × 109 M−1 s−1; however, the
interaction between the excited state of DCA and 3a with NaOH
was not observed in these concentrations (Detailed method of the
calculation is shown in Experimental Section).
Conclusion
In conclusion, the direct photoinduced decarboxylation of
benzoic acids using BP and DCN or DCA with slight heating was
achieved. The resulting aryl radicals react with electron-deficient
alkenes, diboron, and acetonitrile to furnish adducts, arylboronate
esters, and the reduction product, respectively. Further
investigation into improvement of product yields with visible
light-irradiation using the modified organic photoredox catalyst is
in progress.
Figure 2. Plausible mechanism underlying decarboxylative
radical reactions of 3.
O
O
Based on the abovementioned results and our previous report,23
we suggest that the generation of aryl radicals 2 from benzoic
acids 3 using organic photoredox catalysts via photoinduced
decarboxylation leads to the radical reactions, as depicted in
Figure 2. PET between BP and DCN or DCA under UV or
visible-light irradiation affords the radical cation of BP and the
radical anion of DCN or DCA. The radical cation of BP oxidizes
the aryl carboxylate ion to generate aryl carboxy radical 1, which
undergoes sequential decarboxylation upon heating to give 2. In
addition, PET between the aryl carboxylate ion and the excited
state of DCN generates the carboxy radical 1 and the radical anion
of DCN, although PET between the aryl carboxylate ion and the
excited state of DCA did not occur. As shown in entry 12 in Table
1, the photoreaction through the direct PET between the aryl
carboxylate ion and DCN did not proceed, probably because BET
between 1 and the radical anion of DCN was faster than the
decarboxylation of 1. In the case of 4-methoxybenzoic acid, the
similar PET between DCN and 4-methoxybenzoate ion took place,
and the fast BET led to non-decarboxylation and the recovery of
starting material. This means that products are primarily obtained
through the formation of the BP/DCN or BP/DCA radical ion pair
as shown in Figure 2. Photoinduced decarboxylation of benzoic
acids using Ir and Fukuzumi photocatalysts was unsuccessful and
the starting material was regenerated, probably because of the low
rate of decarboxylation of 1 and the high rate of BET between 1
and the reductant part of Ir and Fukuzumi photocatalysts. In
contrast, the low efficiency of BET in our two-molecule
photoredox system led to the successful decarboxylation of 1.
According to Glorius et al., the high rates of non-decarboxylative
pathways, such as hydrogen abstraction of 1, disturb the
photoinduced decarboxylation of benzoic acids.14 However, we
have suggested that the low rate of the BET to 1 is essential for a
R
BET
+ e
O
BP
O
DCN*
DCA*
1
PET

h
R
BP
DCN
DCA
CN
– CO2
+ H+

5
DCN
DCA
Decarboxylation
R
CN
4A
CN
R
R
2
Aryl radicals
O
O
O
B
B
O
6
7
CH3CN or CD3CN
8 or d-8
Experimental Section
General Information. All reagents and solvents were used as
received from commercial suppliers. IR spectra were recorded on
1
an FT-IR spectrometer. H NMR spectra were recorded in CDCl3
containing tetramethylsilane as an internal standard, and were
acquired on either a 300 or 500 MHz spectrometers. 13C{1H}
NMR spectra were acquired on a 125 MHz spectrometer. High-
resolution mass spectra were obtained using double-focusing
magnetic sector mass spectrometer coupled with FAB. The UV-
light source was a Riko UV-100HA high-pressure (100 W)
mercury arc. Pyrex vessels (18 mm × 180 mm) in the water bath
were directly attached to the light source (λ > 280 nm, DCN
mainly absorbs at 313 nm light; Figure S1a). The visible-light
successful photoinduced decarboxylation.
Addition of the
resulting aryl radicals 2 to electron-deficient alkenes 4 gave the
radical intermediates, and subsequent reduction via BET from the
radical anion of DCN or DCA and protonation furnished adducts
5. In the presence of diboron 6, aryl radicals 2 attacked the
ACS Paragon Plus Environment

Page 5 of 9
The Journal of Organic Chemistry
source was a 18 W blue LED (EvoluChem, P206-18-1 405 nm),
Characterization data for 5, 7, and 8
1
2
3
4
5
6
7
8
and Pyrex vessels (10 mm × 120 mm) in the water bath were set
at a distance of 10 cm from the LED (Figure S1b).
Adducts 5 have been previously reported by us23 except
5dA,eA,fA,gA,hA,kA,nA.
General procedures for the photoreaction of benzoic acids 3
and acrylonitrile 4A
3-Phenylpropanenitrile 5aA (using hexane/EtOAc = 15:1 as the
eluent), 0.07024 (UV-light) and 0.01480 (visible light) g, 69 and
37%, Colorless oil; 1H NMR (300 MHz, CDCl3): δ 7.36–7.22 (m,
5H), 2.95 (t, J = 7.5 Hz, 2H), 2.61 (t, J = 7.5 Hz, 2H); 13C{1H}
NMR (125 MHz, CDCl3): δ 138.0, 128.9, 128.3, 127.2, 119.2,
31.6, 19.4.
An aqueous CH3CN solution (CH3CN 36 mL, H2O 4 mL) of
benzoic acids 3 (20 mM), NaOH (20 mM, 0.0320 g), BP (10 mM,
0.0616 g), and DCN (10 mM, 0.0712 g) in Pyrex vessels (18 mm
x 180 mm) was purged with argon for 10 min, and acrylonitrile
4A (100 mM, 0.264 mL) was added under argon atmosphere. The
mixture was irradiated with 100 W high-pressure mercury lamp
for 3 h at 30°C, and then the solvent was removed under reduced
pressure. The crude product was purified by silica-gel column
chromatography using hexane/EtOAc as the eluents to yield
adducts 5. Photoreactions of 3 (5 mM) and 4A (25 mM, 0.100
mL) with visible light-irradiation (blue LED, 405 nm) using BP (2
mM, 0.0185 g) and DCA(2 mM, 0.0276 g) for 3 h at 30°C were
also carried out similarly (CH3CN 54 mL, H2O 6 mL).
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
3-(4-t-Butylphenyl)propanenitrile 5bA (using hexane/EtOAc =
15:1 as the eluent), 0.09136 (UV-light) and 0.02111 (visible light)
g, 61 and 38%, Colorless oil; 1H NMR (300 MHz, CDCl3): δ 7.36
(d, J = 8.4 Hz, 2H), 7.16 (d, J = 8.4 Hz, 2H), 2.93 (t, J = 7.4 Hz,
2H), 2.60 (t, J = 7.4 Hz, 2H), 1.31 (s, 9H); 13C{1H} NMR (125
MHz, CDCl3): δ 150.1, 135.0, 128.0, 125.8, 119.3, 34.5, 31.3,
31.1, 19.3.
3-(4-Methylphenyl)propanenitrile 5cA (using hexane/EtOAc =
1
15:1 as the eluent), 0.05013 g, 43%, Colorless oil; H NMR (300
General procedures for the photoreaction of benzoic acids 3
and bis(pinacolato)diboron 6 and the photoreaction of 3g
without 4 and 6
MHz, CDCl3): δ 7.14–7.10 (m, 4H), 2.92 (t, J = 7.4 Hz, 2H), 2.59
(t, J = 7.4 Hz, 2H), 2.33 (s, 3H); 13C{1H} NMR (125 MHz,
CDCl3): δ 136.9, 135.0, 129.5, 128.1, 119.2, 31.2, 21.1, 19.5.
An aqueous CH3CN solution (CH3CN 18 mL, H2O 2 mL) of
benzoic acids 3 (20 mM), BP (30 mM, 0.0925 g), and DCN (30
mM, 0.107 g) in Pyrex vessels (18 mm x 180 mm) was purged
with argon for 10 min, and bis(pinacolato)diboron 6 (60 mM,
0.305 g) was added under argon atmosphere. The mixture was
irradiated with 100 W high-pressure mercury lamp for 6 h at 30°C,
and then the solvent was removed under reduced pressure. The
crude product was purified by silica-gel column chromatography
using hexane/EtOAc as the eluents to yield adducts 7. Similar
photoreactions of 3f (20 mM, 0.1041 g) using BP (5 mM, 0.0148
g) and DCN (5 mM, 0.0178 g) in CH3CN/H2O = 8:2 or
CH3CN/D2O = 8:2 for 6 h at 30°C without 4 and 6 were carried
out. Visible-light induced reaction of 3a (2 mM, 0.0146 g) and 6
(6 mM, 0.0914 g) with BP (2 mM, 0.0185 g) and DCA (2 mM,
0.0273 g) was conducted similarly (CH3CN 54 mL, H2O 6 mL).
3-(3,5-Dimethylphenyl)propanenitrile 5dA (using hexane/EtOAc
= 15:1 as the eluent), 0.06496 g, 51%, Colorless oil; IR (neat,
1
cm−1) 2918, 2248; H NMR (300 MHz, CDCl3): δ 6.91 (s, 1H),
6.83 (s, 2H), 2.88 (t, J = 7.4 Hz, 2H), 2.59 (t, J = 7.4 Hz, 2H),
2.30 (s, 6H); 13C{1H} NMR (125 MHz, CDCl3): δ 138.5, 138.0,
128.8, 126.0, 119.3, 31.5, 21.3, 19.3; HRMS (FAB) calcd for
(M+H)+ C11H14N, 160.1126; found, 160.1110.
3-(4-Cyclohexylphenyl)propanenitrile 5eA (using hexane/EtOAc
= 30:1 as the eluent), 0.08940 g, 42%, Colorless oil; IR (neat,
1
cm−1) 2969, 2249; H NMR (300 MHz, CDCl3): 7.21–7.12 (m,
4H), 2.92 (t, J = 7.4 Hz, 2H), 2.60 (t, J = 7.4 Hz, 2H), 2.52–2.44
(m, 1H), 1.87–1.73 (m, 5H), 1.47–1.21 (m, 5H); 13C{1H} NMR
(125 MHz, CDCl3): δ 147.1, 135.4, 128.2, 127.3, 119.3, 44.2, 34.4,
31.2, 26.9, 26.1, 19.4; HRMS (FAB) calcd for (M+H)+ C15H20N,
214.1595; found, 214.1583.
Large scale photoreaction of 3a with 4A by UV irradiation
3-[4-(4-Butylcyclohexyl)phenyl]propanenitrile
5fA
(using
Similar large scale photoreaction of 3a (20 mM, 0.488 g) with
4A (100 mM, 1.321 mL) in the presence of NaOH (20 mM, 0.160
g), BP (10 mM, 0.3084 g), and DCN (10 mM, 0.3564 g) by high-
pressure (100 W) mercury arc in an aqueous CH3CN solution
(CH3CN 180 mL, H2O 20 mL) using ten Pyrex vessels (18 mm x
180 mm) was carried out to furnish 5aA (0.351 g) in a 67 % yield.
hexane/EtOAc = 15:1 as the eluent), 0.09382 g, 44%, Colorless
1
oil; IR (neat, cm−1) 2923, 2241; H NMR (300 MHz, CDCl3): δ
7.19–7.12 (m, 4H), 2.92 (t, J = 7.4 Hz, 2H), 2.59 (t, J = 7.4 Hz,
2H), 2.50–2.40 (m, 1H), 1.94–1.77 (m, 5H), 1.49–1.16 (m, 12H),
1.09–0.83 (m, 6H); 13C{1H} NMR (125 MHz, CDCl3): δ 146.9,
135.4, 128.2, 127.3, 119.3, 44.2, 37.3, 37.1, 34.3, 33.6, 31.2, 29.2,
23.0, 19.4, 14.2; HRMS (FAB) calcd for (M+H)+ C19H28N,
270.2222; found, 270.2227.
Fluorescence quenching of DCN and DCA by BP and 3a with
NaOH
The fluorescence of DCN and DCA (1.0 x 10-4M) in the aqueous
CH3CN solution (CH3CN/H2O = 9:1) excited at 310 and 400 nm
were quenched by BP (Figure S2 and S4), 3a with 1 equiv. of
NaOH (Figure S3 and S5), and 4-methoxybenzoic acid with 1
equiv. of NaOH (Figure S6), respectively. The rate constants for
fluorescence quenching (kq) of DCN and DCA by BP, 3a with
NaOH, and 4-methoxybenzoic acid with NaOH were calculated
from the Stern−Volmer plot I0/I = 1+kqτ[Q]. (I0: fluorescence
intensity of DCN and DCA at 386 and 437 nm, I: observed
fluorescence intensity of DCN and DCA at 386 and 437 nm with
BP or 3a with 1 equiv. of NaOH or 4-methoxybenzoic acid with 1
equiv. of NaOH, τ = 10.1 and 15.1 ns (fluorescence lifetime of
DCN and DCA), [Q]: concentration of BP or 3a with 1 equiv. of
NaOH or 4-methoxybenzoic acid with 1 equiv. of NaOH).
3-(4-Acetoxyphenyl)propanenitrile 5gA (using hexane/EtOAc =
15:1 to 10:1 as the eluent), 0.03413 g, 26%, Colorless oil; IR (neat,
cm−1) 3039, 2251, 1759; 1H NMR (300 MHz, CDCl3): δ 7.24 (d, J
= 8.6 Hz, 2H), 7.06 (d, J = 8.6 Hz, 2H), 2.95 (t, J = 7.5 Hz, 2H),
2.61 (t, J = 7.5 Hz, 2H), 2.29 (s, 3H); 13C{1H} NMR (125 MHz,
CDCl3): δ 169.5, 149.8, 135.6, 129.3, 122.0, 119.0, 31.0, 21.1,
19.3; HRMS (FAB) calcd for (M+H)+ C11H12NO2, 190.0868;
found, 190.0856.
3-(4-O-Boc-oxyphenyl)propanenitrile 5hA (using hexane/EtOAc
= 15:1 to 5:1 as the eluent), 0.09480 g, 48%, Colorless oil; IR
1
(neat, cm−1) 2982, 2248, 1757; H NMR (300 MHz, CDCl3): δ
7.24 (d, J = 8.6 Hz, 2H), 7.14 (d, J = 8.6 Hz, 2H), 2.95 (t, J = 7.4
Hz, 2H), 2.60 (t, J = 7.4 Hz, 2H), 1.56 (s, 9H); 13C{1H} NMR
(125 MHz, CDCl3): δ 151.8, 150.2, 135.5, 129.3, 121.8, 119.0,
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 6 of 9
83.7, 31.0, 27.7, 19.4; HRMS (FAB) calcd for (M+H)+ C14H18NO3,
248.1287; found, 248.1280.
[(2-Phenylethyl)sulfonyl]benzene 5aD (using hexane/EtOAc =
30:1 to 10:1 as the eluent), 0.04488 g, 23%, Compound 5aD has
1
2
3
4
5
6
7
8
1
been previously reported.33 Colorless oil, H NMR (300 MHz,
3-(4-Chlorophenyl)propanenitrile 5iA, (using hexane/EtOAc =
CDCl3): δ 7.95 (d, J = 7.0 Hz, 2H), 7.70–7.56 (m, 3H), 7.29–7.20
(m, 3H), 7.11 (d, J = 6.8 Hz, 2H), 3.39–3.37 (m, 2H), 3.08–3.02
(m, 2H); 13C{1H} NMR (125 MHz, CDCl3): δ 139.0, 137.4, 133.8,
129.4, 128.8, 128.3, 128.1, 126.9, 57.5, 28.7.
1
15:1 to 10:1 as the eluent), 0.05864 g, 44%, Colorless oil, H
NMR (300 MHz, CDCl3): δ 7.32 (d, J = 8.4 Hz, 2H), 7.17 (d, J =
8.4 Hz, 2H), 2.93 (t, J = 7.4 Hz, 2H), 2.61 (t, J = 7.4 Hz, 2H);
13C{1H} NMR (125 MHz, CDCl3): δ 136.4, 133.2, 129.7, 129.1,
118.8, 30.9, 19.3.
Phenylboronic acid pinacol ester 7a (using hexane/EtOAc =
30:1 to 10:1 as the eluent), 0.04381 (UV-light) and 0.00932
(visible light) g, 55 and 38%, Compound 7a has been previously
reported.35 Colorless oil, 1H NMR (300 MHz, CDCl3): δ 7.81 (d, J
= 6.6 Hz, 2H), 7.49–7.43 (m, 1H), 7.39–7.34 (m, 2H), 1.35 (s,
12H); 13C{1H} NMR (125 MHz, CDCl3): δ 134.7, 131.3, 127.7,
83.8, 24.9.
3-(4-Bromophenyl)propanenitrile 5jA (using hexane/EtOAc =
15:1 as the eluent), 0.08451 (UV-light) and 0.02871 (visible light)
g, 48 and 45%, Colorless oil, 1H NMR (300 MHz, CDCl3): δ 7.47
(d, J = 8.4 Hz, 2H), 7.12 (d, J = 8.4 Hz, 2H), 2.92 (t, J = 7.4 Hz,
2H), 2.61 (t, J = 7.4 Hz, 2H); 13C{1H} NMR (125 MHz, CDCl3):
δ 136.9, 132.0, 130.0, 121.2, 118.8, 31.0, 19.2.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
4-t-Butylphenylboronic acid pinacol ester 7b (using
3-(2-Bromophenyl)propanenitrile 5kA (using hexane/EtOAc =
hexane/EtOAc = 30:1 to 10:1 as the eluent), 0.04524 g, 44%,
15:1 as the eluent), 0.08469 g, 50%, Colorless oil, IR (neat, cm−1)
1
Compound 7b has been previously reported.36 White solid, H
1
2947, 2246; H NMR (300 MHz, CDCl3): δ 7.57 (d, J = 7.9 Hz,
NMR (500 MHz, CDCl3): δ 7.77 (d, J = 8.0 Hz, 2H), 7.41 (d, J =
8.0 Hz, 2H), 1.34–1.26 (m, 21H); 13C{1H} NMR (125 MHz,
CDCl3): δ 154.5, 134.7, 124.7, 83.6, 34.9, 31.2, 24.8.
1H), 7.32–7.23 (m, 2H), 7.19–7.14 (m, 1H), 3.10 (t, J = 7.4 Hz,
2H), 2.69 (t, J = 7.4 Hz, 2H); 13C{1H} NMR (125 MHz, CDCl3):
δ 137.2, 133.2, 130.8, 129.2, 128.0, 124.0, 118.8, 32.1, 17.6;
HRMS (FAB) calcd for (M+H)+ C9H9N79Br, 209.9919; found,
209.9916. (C9H9N81Br, 211.9898; found, 211.9911.)
4-Methylphenylboronic acid pinacol ester 7c (using
hexane/EtOAc = 30:1 to 10:1 as the eluent), 0.04612 g, 53%,
1
Compound 7c has been previously reported.35 Colorless oil, H
3-(4-Cyanophenyl)propanenitrile 5lA (using hexane/EtOAc =
15:1 to 5:1 as the eluent), 0.04730 (UV-light) and 0.02080 (visible
light) g, 38 and 44%, White solid, 1H NMR (300 MHz, CDCl3): δ
7.65 (d, J = 8.2 Hz, 2H), 7.37 (d, J = 8.2 Hz, 2H), 3.03 (t, J = 7.4
Hz, 2H), 2.67 (t, J = 7.4 Hz, 2H); 13C{1H} NMR (125 MHz,
CDCl3): δ 143.2, 132.7, 129.2, 118.5, 118.3, 111.5, 31.5, 18.9.
NMR (500 MHz, CDCl3): δ 7.70 (d, J = 8.4 Hz, 2H), 7.19 (d, J =
8.4 Hz, 2H), 2.36 (s, 3H), 1.34 (s, 12H); 13C{1H} NMR (125 MHz,
CDCl3): δ 141.4, 134.8, 128.5, 83.6, 24.8, 21.7.
3,5-Dimethylphenylboronic acid pinacol ester 7d (using
hexane/EtOAc = 30:1 to 10:1 as the eluent), 0.04548 g, 49%,
1
Compound 7d has been previously reported.35 White solid, H
3-(4-Trifluoromethylphenyl)propanenitrile
5mA
(using
NMR (500 MHz, CDCl3): δ 7.44 (s, 2H), 7.10 (s, 1H), 2.32 (s,
6H), 1.34 (s, 12H); 13C{1H} NMR (125 MHz, CDCl3): δ 137.3,
133.1, 132.5, 83.8, 24.9, 21.2.
hexane/EtOAc = 15:1 to 10:1 as the eluent), 0.06706 g, 34%,
Colorless oil, 1H NMR (300 MHz, CDCl3): δ 7.61 (d, J = 8.2 Hz,
2H), 7.37 (d, J = 8.2 Hz, 2H), 3.03 (t, J = 7.4 Hz, 2H), 2.66 (t, J =
7.4 Hz, 2H); 13C{1H} NMR (125 MHz, CDCl3): δ 141.9, 130.0 (q,
J = 32 Hz), 128.7, 126.5, 125.9, 118.6, 31.3, 19.1.
4-Cyclohexylphenylboronic acid pinacol ester 7e, (using
hexane/EtOAc = 30:1 to 10:1 as the eluent), 0.05112 g, 45%,
White solid; mp 91 °C; IR (KBr, cm−1) 2965, 2926, 1392, 1361;
1H NMR (500 MHz, CDCl3): δ 7.74 (d, J = 8.0 Hz, 2H), 7.23 (d, J
= 8.0 Hz, 2H), 2.53–2.48 (m, 1H), 1.95–1.80 (m, 4H), 1.77–1.70
(m, 1H), 1.42–1.26 (m, 18H); 13C{1H} NMR (125 MHz, CDCl3):
δ 151.5, 134.9, 126.3, 83.6, 44.9, 34.2, 26.9, 26.1, 24.8; HRMS
(FAB) calcd for (M+H)+ C18H28BO2, 287.2183; found, 287.2174.
Methyl 4-(2-cyanoethyl)benzoate 5nA (using hexane/EtOAc =
15:1 to 5:1 as the eluent), 0.06801 g, 45%, White solid, mp 61 °C;
IR (KBr, cm−1) 3014, 2242, 1716; 1H NMR (300 MHz, CDCl3): δ
8.02 (d, J = 8.2 Hz, 2H), 7.31 (d, J = 8.2 Hz, 2H), 3.91 (s, 3H),
3.01 (t, J = 7.4 Hz, 2H), 2.65 (t, J = 7.4 Hz, 2H); 13C{1H} NMR
(125 MHz, CDCl3): δ 166.7, 143.1, 130.2, 129.3, 128.4, 118.7,
52.2, 31.5, 19.0; HRMS (FAB) calcd for (M+H)+ C11H12NO2,
190.0868; found, 190.0856.
4-Acetoxyphenylboronic acid pinacol ester 7g (using
hexane/EtOAc = 30:1 to 10:1 as the eluent), 0.03796 g, 36%,
1
Compound 7g has been previously reported.37 White solid, H
3-(4-Phenylphenyl)propanenitrile 5oA (using hexane/EtOAc =
15:1 to 10:1 as the eluent), 0.09214 g, 44%, White solid, 1H NMR
(300 MHz, CDCl3): δ 7.59–7.30 (m, 9H), 3.01 (t, J = 7.4 Hz, 2H),
2.66 (t, J = 7.4 Hz, 2H); 13C{1H} NMR (125 MHz, CDCl3): δ
140.6, 140.3, 137.0, 128.8, 128.7, 127.6, 127.4, 127.1, 119.1, 31.2,
19.4.
NMR (300 MHz, CDCl3): δ 7.83 (d, J = 8.4 Hz, 2H), 7.09 (d, J =
8.4 Hz, 2H), 2.29 (s, 3H), 1.33 (s, 12H); 13C{1H} NMR (125 MHz,
CDCl3): δ 169.3, 153.2, 136.2, 121.0, 83.9, 24.8, 21.2.
4-Chlorophenylboronic acid pinacol ester 7i (using
hexane/EtOAc = 30:1 to 10:1 as the eluent), 0.01587 g, 17%,
Compound 7i has been previously reported.34 White solid, 1H
NMR (300 MHz, CDCl3): δ 7.73 (d, J = 8.4 Hz, 2H), 7.34 (d, J =
8.4 Hz, 2H), 1.34 (s, 12H); 13C{1H} NMR (126 MHz, CDCl3): δ
137.5, 136.1, 128.0, 84.0, 24.9.
t-Butyl 3-phenylpropanoate 5aB (using hexane/EtOAc = 30:1 to
8:1 as the eluent), 0.06390 (UV-light) and 0.00990 (visible light)
1
g, 39 and 16%, Colorless oil, H NMR (300 MHz, CDCl3): δ
7.30–7.19 (m, 5H), 2.91 (t, J = 7.8 Hz, 2H), 2.54 (t, J = 7.8 Hz,
2H), 1.42 (s, 9H); 13C{1H} NMR (125 MHz, CDCl3): δ 172.3,
140.8, 128.4, 128.3, 126.1, 80.4, 37.1, 31.1, 28.1.
4-Cyanophenylboronic acid pinacol ester 7l (using
hexane/EtOAc = 30:1 to 10:1 as the eluent), 0.03461 g, 38%,
Compound 7l has been previously reported.37 White solid, 1H
NMR (500 MHz, CDCl3): δ 7.88 (d, J = 8.0 Hz, 2H), 7.64 (d, J =
8.0 Hz, 2H), 1.35 (s, 12H); 13C{1H} NMR (125 MHz, CDCl3): δ
135.1, 131.1, 118.9, 114.5, 84.5, 24.9.
3-Phenylpropanamide 5aC (using hexane/CHCl3 = 3:1 to 0:1 as
1
the eluent), 0.03000 g, 25%, White solid, H NMR (300 MHz,
CDCl3): δ 7.32–7.18 (m, 5H), 2.97 (t, J = 7.7 Hz, 2H), 2.53 (t, J =
7.7 Hz, 2H); 13C{1H} NMR (125 MHz, CDCl3): δ 174.5, 140.7,
128.6, 128.3, 126.3, 37.5, 31.4.
ACS Paragon Plus Environment

Page 7 of 9
The Journal of Organic Chemistry
Introduction of Complex Molecules into Polymer Chain Ends ACS Macro
Lett. 2017, 6, 381−385.
4-Trifluoromethylphenylboronic acid pinacol ester 7m (using
1
2
3
4
5
6
7
8
hexane/EtOAc = 30:1 to 10:1 as the eluent), 0.03769 g, 34%,
(2) Liaoa, W.; Ni, X. Photocatalytic Decarboxylation of Diacids for the
Initiation of Free Radical Polymerization. Photochem. Photobiol. Sci.
2017, 16, 1211−1219.
(3) Yokoi, H.; Nakano, T.; Fujita, W.; Ishiguro, K.; Sawaki, Y. In-Cage
Formation of Carbanions in Photoinduced Electron-Transfer Reaction of
Carboxylate Ions. J. Am. Chem. Soc. 1998, 20, 12453–12458.
(4) Manley, D. W.; McBurney, R. T.; Miller, P.; Howe, R. F.;
Rhydderch, S.; Walton, J. C. Unconventional Titania Photocatalysis:
Direct Deployment of Carboxylic Acids in Alkylations and Annulations.
J. Am. Chem. Soc. 2012, 134, 13580–13583.
(5) Chu, L.; Ohta, C.; Zuo, Z.; MacMillan, D. W. C. Carboxylic Acids
as A Traceless Activation Group for Conjugate Additions: A Three-Step
Synthesis of (±)-Pregabalin. J. Am. Chem. Soc. 2014, 136, 10886−10889.
(6) Zuo, Z.; MacMillan, D. W. C. Decarboxylative Arylation of -
Amino Acids via Photoredox Catalysis: A One-Step Conversion of
Biomass to Drug Pharmacophore. J. Am. Chem. Soc. 2014, 136,
5257−5260.
1
Compound 7m has been previously reported.38 White solid, H
NMR (300 MHz, CDCl3): δ 7.91 (d, J = 7.9 Hz, 2H), 7.61 (d, J =
7.9 Hz, 2H), 1.36 (s, 12H); 13C{1H} NMR (125 MHz, CDCl3): δ
135.0, 133.0 (q, J = 32 Hz), 124.3, 124.3, 84.3, 24.9.
4-Methoxycarbonylphenylboronic acid pinacol ester 7n (using
hexane/EtOAc = 30:1 to 10:1 as the eluent), 0.04505 g, 43%,
1
Compound 7n has been previously reported.36 White solid, H
NMR (500 MHz, CDCl3): δ 8.02 (d, J = 8.0 Hz, 2H), 7.87 (d, J =
8.0 Hz, 2H), 3.92 (s, 3H), 1.36 (s, 12H); 13C{1H} NMR (125 MHz,
CDCl3): δ 167.1, 134.6, 132.2, 128.5, 84.1, 52.1, 24.8.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
4-Phenylphenylboronic acid pinacol ester 7o (using
hexane/EtOAc = 30:1 to 10:1 as the eluent), 0.06279 g, 56%,
1
Compound 7o has been previously reported.39 White solid, H
NMR (500 MHz, CDCl3): δ 7.89 (d, J = 8.0 Hz, 2H), 7.59–7.65
(m, 4H), 7.44 (m, 2H), 7.36 (m, 1H), 1.37 (s, 12H); 13C{1H}
NMR (125 MHz, CDCl3): δ 143.8, 141.0, 135.2, 128.7, 127.5,
127.20, 126.4, 83.8, 24.9.
(7) Cassani, C.; Bergonzini, G.; Wallentin, C. Photocatalytic
Decarboxylative Reduction of Carboxylic Acids and Its Application in
Asymmetric Synthesis. Org. Lett. 2014, 16, 4228−4231.
(8) Griffin, J. D.; Zeller, M. A.; Nicewicz, D. A. Hydrodecarboxylation
of Carboxylic and Malonic Acid Derivatives via Organic Photoredox
Catalysis: Substrate Scope and Mechanistic Insight. J. Am. Chem. Soc.
2015, 137, 11340−11348.
(9) Mumtaz, S.; Robertson, M.; Oelgemöeller, M. Recent Advances in
Photodecarboxylations Involving Phthalimides. Aust. J. Chem. 2018, 71,
634–648.
(10) Hilborn, J. W.; Pincock, J. P. Rates of Decarboxylation of Acyloxy
Radicals Formed in the Photocleavage of Substituted 1-Naphthylmethyl
Alkanoates. J. Am. Chem. Soc. 1991, 113, 2683–2686.
(11) Galli, C. Radical Reactions of Arenediazonium Ions: An Easy
Entry into the Chemistry of The Aryl Radical. Chem. Rev. 1988, 88,
765−792.
(12) Ghosh, I.; Marzo, L.; Das, A.; Shaikh, R.; König, B. Visible Light
Mediated Photoredox Catalytic Arylation Reactions. Acc. Chem. Res.
2016, 49, 1566−1577.
(13) Ramirez, N. P.; Bosque, I.; Gonzalez-Gomez, J. C. Photocatalytic
Dehydrogenative Lactonization of 2-Arylbenzoic Acids. Org. Lett. 2015,
17, 4550−4553.
(14) Candish, L.; Freitag, M.; Gensch, T.; Glorius, F. Mild, Visible
Light-mediated Decarboxylation of Aryl Carboxylic Acids to Access Aryl
Radicals. Chem. Sci. 2017, 8, 3618–3622.
(15) Candish, L.; Teders, M.; Glorius, F. Transition-Metal-Free,
Visible-Light-Enabled Decarboxylative Borylation of Aryl N-
Hydroxyphthalimide Esters. J. Am. Chem. Soc. 2017, 139, 7440–7443.
(16) Patra, T.; Mukherjee, S.; Ma, J.; Strieth-Kalthoff, F.; Glorius, F.
Visible-Light-Photosensitized Aryl and Alkyl Decarboxylative
Functionalization Reactions. Angew. Chem. Int. Ed. 2019, 58, 10514–
10520.
(17) For review, see; Yoshimi, Y. Photoinduced Electron Transfer-
promoted Decarboxylative Radical Reactions of Aliphatic Carboxylic
Acids by Organic Photoredox System. J. Photochem. Photobiol. A 2017,
42, 116–130.
(18) Yoshimi, Y.; Itou, T.; Hatanaka, M. Decarboxylative Reduction of
Free Aliphatic Carboxylic Acids by Photogenerated Cation Radical.
Chem. Commun. 2007, 5244–5246.
(19) Yoshimi, Y.; Masuda, M.; Mizunashi, T.; Nishikawa, K.; Maeda,
K.; Koshida, N.; Itou, T.; Morita, T.; Hatanaka, M. Inter- and
Intramolecular Addition Reactions of Electron-Deficient Alkenes with
Alkyl Radicals, Generated by SET-Photochemical Decarboxylation of
Carboxylic Acids, Serve as a Mild and Efficient Method for the
Preparation of -Amino Acids and Macrocyclic Lactones. Org. Lett. 2009,
11, 4652–4655.
(20) Nishikawa, K.; Yoshimi, Y.; Maeda, K.; Morita, T.; Takahashi, I.;
Itou, T.; Inagaki, S.; Hatanaka, M. Radical Photocyclization Route for
Macrocyclic Lactone Ring Expansion and Conversion to Macrocyclic
Lactams and Ketones. J. Org. Chem. 2013, 78, 582–589.
(21) Yamamoto, T.; Iwasaki, T.; Morita, T.; Yoshimi, Y. A Strategy for
O-Alkylation of Serine and Threonine from Serinyl and Threoninyl Acetic
Acids by Photoinduced Decarboxylative Radical Reactions: Connection
between Serine/Threonine and Carbohydrates/Amino Acids at the Side
Chain. J. Org. Chem. 2018, 83, 3702−3709.
(4-Butylcyclohexyl)benzene 8 (using hexane as the eluent),
1
0.06247 g, 72%, Colorless oil, IR (neat, cm−1) 2923, 2858; H
NMR (500 MHz, CD3OD): δ 7.27–7.10 (m, 5H), 2.49–2.30 (m,
1H), 1.95–1.70 (m, 4H), 1.51–0.86 (14H); 13C{1H} NMR (125
MHz, CD3OD): δ 147.6, 128.0, 126.5, 125.5, 44.8, 37.3, 37.1,
34.3, 33.5, 29.1, 22.82, 13.2; HRMS (FAB) calcd for (M+H)+
C16H25, 217.1957; found, 217.1938.
4-(4-Butylcyclohexyl)-1-d-benzene d-8 (using hexane as the
eluent), 0.03985 g, 46%, Colorless oil, IR (neat, cm−1) 2924,
1
2852; H NMR (500 MHz, CD3OD): δ 7.23–7.10 (m, 4H), 2.49–
2.32 (m, 1H), 1.88–1.71 (m, 4H), 1.51–0.85 (m, 14H); 13C{1H}
NMR (125 MHz, CD3OD): δ 147.6, 127.9, 126.4, 125.5, 44.8,
37.3, 37.0, 34.3, 33.5, 29.1, 22.8, 13.2; HRMS (FAB) calcd for
(M+H)+ C16H24D, 218.2019; found, 218.2003.
ASSOCIATED CONTENT
Supporting Information
The Supporting Information is available free of charge on the
ACS Publication website
1
Experimental procedures, and H and 13C{1H} NMR spectra
(PDF).
AUTHOR INFORMATION
Corresponding Author
*yyoshimi@u-fukui.ac.jp
Notes
The authors declare no competing financial interests.
ACKNOWLEDGMENT
This work was supported by the Japan Society for the Promotion
of Science (JSPS), Grant-in-Aid no. 17K05779, for scientific
research.
REFERENCES
(1) Yamawaki, M.; Ukai, A.; Kamiya, Y.; Sugihara, S.; Sakai, M.;
Yoshimi Y. Metal-Free Photoinduced Decarboxylative Radical
Polymerization Using Carboxylic Acids as Benign Radical Initiators:
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 8 of 9
(22) Osaka, K.; Usami, A.; Iwasaki, T.; Yamawaki, M.; Morita, T.;
Yoshimi, Y. Sequential Intermolecular Radical Addition and Reductive
Radical Cyclization of Tyrosine and Phenylalanine Derivatives with
Alkenes via Photoinduced Decarboxylation: Access to Ring-constrained γ-
Amino Acids. J. Org. Chem. 2019, 84, 9480−9488.
1
2
3
(23) Iwata, Y.; Tanaka, Y.; Kubosaki, S.; Morita, T.; Yoshimi, Y. A
Strategy for Generating Aryl Radicals from Arylborates through Organic
Photoredox Catalysis: Photo-Meerwein Type Arylation of Electron-
deficient Alkenes. Chem. Commun. 2018, 54, 1257−1260.
(24) Tanaka, Y.; Kubosaki, S.; Osaka, K.; Yamawaki, M.; Morita, T.;
Yoshimi, Y. Two Types of Cross-Coupling Reactions between Electron-
Rich and Electron–Deficient Alkenes Assisted by Nucleophilic Addition
Using Organic Photoredox Catalyst. J. Org. Chem. 2018, 83,
13625−13635.
(25) Montalti, M.; Credi, A.; Prodi, L.; Gandolfi, M, T. Handbook of
Photochemistry 3rd ed., CRC Press, Taylor & Francis Group, Boca Raton,
p.510−512 (2006).
(26) Guirado, G.; Fleming, C. N.; Lingenfelter, T. G.; Williams, M. L.;
Zuilhof, H.; Dinnocenzo, J. P. Nanosecond Redox Equilibrium Method for
Determining Oxidation Potentials in Organic Media. J. Am. Chem. Soc.
2004, 126, 14086–14094.
(27) Mukherjee, S.; Maji, B.; Tlahuext-Aca, A.; Glorius, F. Visible-
Light-Promoted Activation of Unactivated C(sp3)–H Bonds and Their
Selective Trifluoromethylthiolation. J. Am. Chem. Soc. 2016, 138, 16200–
16203.
(28) Fukuzumi, S.; Ohkubo, K. Organic Synthetic Transformations
Using Organic Dyes as Photoredox Catalysts. Org. Biomol. Chem. 2014,
12, 6059–6071.
(29) Chen, K.; Zhang, S.; He, P.; Li, P. Efficient Metal-Free
Photochemical Borylation of Aryl Halides under Batch and Continuous-
Flow Conditions. Chem. Sci. 2016, 7, 3676–3680.
(30) Mfuh, A. M.; Doyle, J. D.; Chhetri, B.; Arman, H. D.; Larionov,
O. V. Scalable, Metal-and Additive Free, Photoinduced Borylation of
Haloarenes and Quaternary Arylammonium Salts. J. Am. Chem. Soc. 2016,
138, 2985–2988.
(31) Zhang, L.; Jiao, L. Visible-Light-Induced Organocatalytic
Borylation of Aryl Chlorides. J. Am. Chem. Soc. 2019, 141, 9124–9128.
(32) Miyaura, N.; Suzuki, A. Palladium-Catalyzed Cross-Coupling
Reactions of Organoboron Compounds. Chem. Rev. 1995, 95, 2457−2483.
(33) Kumagai, Y.; Naoe, T.; Nishikawa, K.; Osaka, K.; Morita, T.;
Yoshimi, Y. Formation of Carbanions from Carboxylate Ions Bearing
Electron-Withdrawing Groups via Photoinduced Decarboxylation:
Addition of Generated Carbanions to Benzaldehyde. Aust. J. Chem. 2015,
68, 1668–1671.
(34) Geoghegan, K.; Kelleher, S.; Evans, P. An Investigation into the
One-Pot Heck Olefination−Hydrogenation Reaction. J. Org. Chem. 2011,
76, 2187–2194.
(35) Yan, G.; Jiang, Y.; Kuang, C.; Wang, S.; Liu, H.; Zhang, Y.;
Wang, J. Nano-Fe2O3-Catalyzed Direct Borylation of Arenes. Chem.
Commun. 2010, 46, 3170−3172.
(36) Yamamoto, T.; Morita, T.; Takagi, J.; Yamakawa, T.
NiCl2(PMe3)2-Catalyzed Borylation of Aryl Chlorides. Org. Lett. 2011,
13, 5766−5769.
(37) Mo, F.; Jiang, Y.; Qiu, D.; Zhang, Y.; Wang, J. Direct Conversion
of Arylamines to Pinacol Boronates: A Metal‐Free Borylation Process.
Angew. Chem. Int. Ed. 2010, 49, 1846−1849.
(38) Claudel, S.; Gosmini, C.; Paris, J. M.; Périchon, J. A Novel
Transmetallation of Arylzinc Species into Arylboronates from Aryl
Halides in A Barbier Procedure. Chem. Commun. 2007, 3667−3669.
(39) Chen, H. B.; Zhou, Y.; Yin, J.; Yan, J.; Ma, Y.; Wang, L.; Cao, Y.;
Wang, J.; Pei, J. Single Organic Microtwist with Tunable Pitch. Langmuir
2009, 25, 5459−5462.
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
ACS Paragon Plus Environment

Page 9 of 9
The Journal of Organic Chemistry
1
2
3
4
5
6
7
8
9
Table of Contents
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
CN
CN
CN
CN
UV-light-irradiation visible light-irradiation
(313 nm)
(405 nm)
X
R
O
B
CO2H
O
Decarboxylation
R
R
Aryl radicals
R
CO2
H(D)
R
9
ACS Paragon Plus Environment