Electrochemically Enabled Carbohydroxylation of Alkenes with H2O and Organotrifluoroborates

Article abstract of DOI:10.1021/jacs.8b08592

Unprecedented hydroxy-alkynylation and -alkenylation reactions of arylalkenes have been developed through electrochemically enabled addition of an organotrifluoroborate reagent and H₂O across the double bond of the alkene. The use of electrochemistry to promote these oxidative alkene 1,2-difunctionalization reactions not only obviates the need for transition-metal catalysts and oxidizing reagents but also ensures high regio- and chemoselectivity to afford homopropargylic or homoallylic alcohols. The possibility of extending the electrochemical alkene difunctionalization strategy to other alkene carbo-heterofunctionalization reactions has been demonstrated.

Full text of DOI:10.1021/jacs.8b08592

Subscriber access provided by The University of Texas at El Paso (UTEP)
Communication
Electrochemically Enabled Carbohydroxylation
2
of Alkenes with HO and Organotrifluoroborates
Peng Xiong, Hao Long, Jinshuai Song, Yaohui Wang, Jian-Feng Li, and Hai-Chao Xu
J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/jacs.8b08592 • Publication Date (Web): 02 Nov 2018
Downloaded from http://pubs.acs.org on November 2, 2018
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 6
Journal of the American Chemical Society
1
2
3
4
5
6
7
8
9
Electrochemically Enabled Carbohydroxylation of Alkenes with H2O
and Organotrifluoroborates
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
Peng Xiong,†,§ Hao Long,†,§ Jinshuai Song,‡ Yaohui Wang,† Jian-Feng Li,† Hai-Chao Xu*,†
†State Key Laboratory of Physical Chemistry of Solid Surfaces, Key Laboratory of Chemical Biology of Fujian Province,
Innovative Collaboration Center of Chemistry for Energy Materials, and College of Chemistry and Chemical Engineering,
Xiamen University, Xiamen 361005, P. R. China
‡Fujian Institute of Research on Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, P. R. China
Supporting Information Placeholder
which facilitates their self-coupling or polymerization especially
for terminal alkenes.5f,g As a result, electrochemical alkene
difunctionalization reactions that proceed through alkene radical
cations generally employ a large excess of external nucleophiles,
such as solvent molecules, to efficiently trap the radical cations
(Scheme 1a, bottom-right).6f-i,7
ABSTRACT: Unprecedented hydroxy-alkynylation and
-
alkenylation reactions of aryl alkenes have been developed through
electrochemically enabled addition of an organotrifluoroborate
reagent and H2O across the double bond of the alkene. The use of
electrochemistry to promote these oxidative alkene 1,2-
difunctionalization reactions not only obviates the need for
transition metal catalysts and oxidizing reagents but also ensures
high regio- and chemoselectivity to afford homopropargylic or
homoallylic alcohols. The possibility of extending the
electrochemical alkene difunctionalization strategy to other alkene
carboheterofunctionalization reactions has been demonstrated.
Alkynyl- and alkenyltrifluoroborate salts have been widely
employed in organic synthesis owing to their easy availability,
stability and excellent crystallinity.8 Although no reactions
between alkynyltrifluoroborates and radical species have been
reported, alkenyltrifluoroborates have been shown to react
regioselectively with electrophilic radicals9a,b and enamine-derived
radical cations9c at the ipso-position. Encouraged by these studies,
herein we report the electrochemically enabled regio- and
chemoselective hydroxy-alkynylation and -alkenylation reactions
of alkenes via sequential addition of alkynyl- or
alkenyltrifluoroborate and H2O across the olefinic double bond
(Scheme 1b). Our method provides efficient access to
homopropargylic and homoallylic alcohols without the need for
transition metal-catalysts or oxidizing reagents.10 In addition,
extension to other alkene carboheterofunctionalization reactions
has been demonstrated.
Vicinal difunctionalization of alkenes, which adds one substituent
to each carbon of a double bond, provides a straightforward and
highly attractive strategy for organic synthesis.1 Despite extensive
research in this area, only a few reported literatures have explored
the synthesis of functionalized alkynes and alkenes via the vicinal
addition of a heteroatom group and an alkynyl or alkenyl group,
which generally involve transition metal (TM)-catalyzed
intramolecular cyclizations with
a
tethered heteroatom
nucleophile.2 In contrast, the more challenging three-component
intermolecular hetero-alkynylation and -alkenylation of alkenes
remain rare3 and to the best of our knowledge, intermolecular
alkene hydroxy-alkynylation and -alkenylation reactions have not
been reported.
Scheme 1. Electrochemical 1,2-Difunctionalization of
Alkenes with Two Nucleophiles
(a) Previous work
Radical pathway
X
X
R
NaN3
or MgCl2
MgCl2
NaO2SCF3
CF3
R'
Cl
R'
Organic electrochemistry, which employs electrons as traceless
redox reagents, provides an enabling and environmentally
sustainable tool for organic synthesis.4 Electrochemistry is capable
of achieving reactivity umpolung through single electron transfer
(SET), allowing the coupling of two or more functionalities that
share the same polarity. The feasibility of this concept has been
demonstrated in several published studies that have accomplished
the intermolecular anodic difunctionalization of alkenes with two
nucleophiles (Scheme 1a).5 However, most of these reactions
involved the introduction of two heteroatom-based functionalities.
Nonetheless, Lin has very recently reported efficient Mn-catalyzed
electrochemical chlorotrifluoromethylation of alkenes with MgCl2
and CF3SO2Na via addition of CF3 radical to the alkene (Scheme
1a, top-right).5c An alternative strategy to achieve alkene
difunctionalization with two nucleophiles is to use alkene-derived
radical cation as the key intermediate.6 Alkenes can lose one
electron on the electrode surface to generate a high local
concentration of the corresponding radical cation intermediates,
R'
R
R
Ref. 5a,b
Ref. 5c
X = N3 or Cl
Radical cation pathway
O
X
X
ArSH
ROH or RNH2
X
ArS
R
or MeOH
S
R'
R
R'
Ref. 5d,e
Ref. 5f-i
X = O, OH, OMe
X = OR or NHR
(b) This work
OH
KF3B R3
+
R
R
R3
=
R3
R2
R2
R1
R3
R1
R2
+
H2O
R1
R3
OH
R3
via
OH
OH
R2
R2
R2
R1
R1
R1
Our studies began by optimizing the reaction conditions for the
difunctionalization of alkene 1 with H2O and alkynyltrifluoroborate
2. The best results were obtained by conducting the electrolysis at
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 2 of 6
50 °C, under a constant current of 5 mA, in an undivided cell (a
MeCN with acetone (entry 9), and changing the current (7.5 mA,
entry 10 or 3 mA, entry 11), were all found to lower the yield of 3.
An optimal concentration of H2O was need because it served as a
reactant and to increase the solubility of the salts.
1
2
3
4
5
6
7
8
three-necked round-bottomed flask) equipped with a graphite rod
anode and a platinum plate cathode, and with a mixed solvent of
MeCN/H2O containing KHCO3 as additive. Under these
conditions, the desired homopropargylic alcohol product 3 was
obtained as the only regioisomer in 78% yield (entry 1). In addition,
no other homo-addition products, such as those derived from
dihydroxylation or dialkynylation, were detected. Control
experiments showed
The substrate scope of the reaction was then explored by first
varying the substituents of the alkene (Scheme 2). When the 1,1-
diphenyl alkene 1 was used, the reaction showed broad
compatibility with a wide range of substituents with diverse
electronic properties on the benzene ring (4–13). Aryl, alkyl-
substituted alkenes (14–24) were also well tolerated. Potentially
labile functional groups, including silylether (19), free alcohol (20)
and ester (21), were all left intact after the electrochemical
difunctionalization. Furthermore, alkenes that carried a heteroaryl
substituent, such as a 3-pyridyl (25), 2-thiazolyl (26), 2-
benzothiazolyl (27) or 2-benzoxazolyl (28) group, were all shown
to be suitable substrates. However, product formation was
significantly hampered when a monosubstituted styrenyl alkene
was employed (29, 30). Disubstituted aryl alkene such as 1-buten-
1-ylbenzene reacted successfully to give the desired product 31 in
55% yield, albeit with low diastereoselectivity (1.3:1 dr). The
reaction of 1,1-diphenylpropene, a trisubstituted alkene, afforded
the hydroxy-alkynylation product 32 in 27% yield along with 51%
of vicinal diol 33, 10% of 3-methyl-2,2-diphenyloxirane and 9% of
benzophenone.11,12 This alkene reacted preferentially with H2O
over the trifluoroborate probably because of the increased steric
demand.
Table 1. Optimization of Reaction Conditionsa
9
OH
n-Bu
Ph
Pt
C
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
KF3B
n-Bu
+
Ph
Ph
Ph
3
KHCO3 (1.5 equiv)
H O
1
2
MeCN/
, 50 °C
2
entry deviation from standard conditions
yield/%b
78c
61
58
NR
60
50
69
71
60
41
45
1
none
2
Reaction at rt
3
No KHCO3
4
No electricity
5
K2CO3 as the base
NaHCO3 as the base
MeCN/H2O (20:1) as the solent
MeCN/H2O (5:1) as the solent
Acetone/H2O (14:1) as the solvent
7.5 mA
6
7
8
9
10
11
We next tested a variety of potassium organotrifluoroborates
(Scheme 2). The terminal butyl moiety in 2 could be replaced with
a primary alkyl chain bearing a hydroxyl (34), chloro (35) or
alkynyl group (36), a more sterically hindered cyclohexyl (37) or
tBu (38), or a phenyl ring para-substituted with H (39), OMe (40),
Me (41) or halogen (42–44). An alkynyl trifluoroborate capped
with an alkenyl group also exhibited moderate reactivity toward 1
affording the enyne product 45. Pleasingly, alkenyltrifluoroborates
were also found to be compatible with the reaction system and
afforded homoallylic alcohols in moderate to excellent yields (46–
3 mA
aReaction conditions: Undivided cell, graphite rod anode, Pt
cathode, 1 (0.2 mmol), 2 (0.6 mmol), MeCN (5.5 mL), H2O (0.4
mL), argon, 5 mA, 3.3 F mol−1 (based on 1). bYield determined by
1H-NMR analysis using 1,3,5-trimethoxybenzene as the internal
standard. cIsolated yield. NR = no reaction.
that the reaction became less efficient at room temperature (entry
2) or in the absence of KHCO3 (entry 3), and was completely
abolished when there was no electric current (entry 4). Using
another base additive such as K2CO3 (entry 5) or NaHCO3 (entry
6), altering the ratio of MeCN/H2O (entries 7 and 8), replacing
49).13
Importantly,
the
stereochemistry
of
the
alkenyltrifluoroborate was well-maintained during the reaction,
providing stereoselective access to homoallylic alcohols bearing an
internal alkene (47–49).
Scheme 2. Scope of the Electrohemical Hydroxy-Alkynylation and -Alkenylation of Alkenesa
ACS Paragon Plus Environment

Page 3 of 6
Journal of the American Chemical Society
R3
R1
OH
OH
KF3B
KF3B
R3
Pt
KHCO3 (1.5 equiv)
C
R3
+
or
or
R2
1
Ar
Ar
R1
R1
R3
H O
CH3CN/
, 50 °C
2
2
3
4
5
6
7
8
9
Scope of Alkene
OH
n-Bu
OH
n-Bu
4
5
6
7
8
9
, R = Me, 63%
R1
R2
OH
Ph
13
n-Bu
, R = F, 74%
Me
Ph
OH
n-Bu
, R = Cl, 65%
, R = Br, 60%
, R = CF3, 75%
, R = CN, 72%
R
14
, R = H, 67%
, R = F, 54%
, R = Br, 51%
Ph
, R1 = Br, R2 = H, 65%
, R1 = F, R2 = OMe, 48%
11
12
15
16
, 53%
R
10
, R = CONEt2, 70%
OH
n-Bu
OH
n-Bu
OH
OH
n-Bu
n-Bu
OH
n-Bu
R
N
Ph
n
Ph
Me
Ph
R
19
20
21
Me
22
, R = TBDPSO, 69%
, R = CH2CH2OH, 55%
, R = CH2CH2OOCt-Bu, 66%
17
23
24
, R = Et, 56%
, n = 0, 58%
, n = 1, 68%
25
, 41%
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
, 55%
OH
18
, R = i-Pr, 68%
n-Bu
OH
n-Bu
OH
n-Bu
OH
n-Bu
OH
n-Bu
OH
X
Ph
Ph
Ph
OH
S
Ph
Ph
Me
+
Me
N
Et
N
R
Me
Me
27
28
, X = S, 50%
, X = O, 40%
29
30
, R = H, 25%
, R = Br, 20%
b
26
31
, 50%
, 55% (1.3:1 dr)
32
33
, 27% + , 51%
Scope of Organotrifluoroborate
OH
t-Bu
OH
OH
OH
OH
OH
Cl
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
35
Ph
Br
34
36
37
38
, 52%
, 64%
, 69%
, 60%
, 68%
39
40
41
42
43
44
, R = H, 52%
, R = OMe, 54%
, R = Me, 40%
, R = F, 68%
, R = Cl, 60%
, R = Br, 53%
OH
R
OH
OH
OH
OH
n-Bu
n-Bu
Ph
OH
Ph
Me
Ph
Ph
Ph
Ph
[from E-alkenyltrifluoroborate]
Ph
n-Bu
Ph
Ph
45
[from Z-alkenyltrifluoroborate]
48
, 55% (>20:1 E/Z)
49
Ph
Ph
, 48%
46
47
, 40%
, 91% (>20:1 E/Z)
, 78% (>20:1 Z/E)
aReaction conditions from Table 1, entry 1, alkene (0.2 mmol), trifluoroborate salt (0.6 mmol), 2.8–3.8 h. Isolated yields were reported.
b10% of 3-methyl-2,2-diphenyloxirane and 9% of benzophenone were also formed.
employment of tethered oxygen nucleophiles led to the formation
of valuable functionalized heterocycles (51–67 and 69).
Scheme 3. Scope of Heteroatom Nucleophiles
OMe
n-Bu
Pt
C
Scheme 4. Gram Scale Synthesis and Product
Transformationsa
2
1
+
Ph
Ph
50
(3 equiv)
MeOH
MeCN/
(5.5:1)
, 80%
1
2
+
Ph
n-Bu
R1
R1
HN
O
Ph
Pt
C
O
n-Bu
+
R2 BF3K
(2.5 equiv)
N
76
71
R2
a
KHCO3 (1.5 equiv)
Ph
g
CH3CN/H2O, 80 °C, 5 mA
Ar
Ar
CN
n-Bu
OH
Ph
n-Bu
b
51
52
53
54
55
56
57
58
59
, R = C6H5, 78%
n-Bu
72
60
61
Ph 47%
40%
, R =
, R =
Ph
Ph
, R = 4-MeO-C6H4, 72%
, R = 4-Me-C6H4, 74%
, R = 4-Cl-C6H4, 68%
, R = 4-I-C6H4, 76%
Ph
f
75
Ph
n-Bu
3
(62%, 1.44 g)
R
Ph
c
OH
Ph
e
O
Ph
Ph
d
O
N
, R = 4-CF3-C6H4, 59%
, R = 4-CN-C6H4, 52%
, R = 4-pyridyl, 51%
OH
Ph
H
62
, R =
52%
Ph
n-Bu
Ph
(1:1 dr)
n-Bu
73
Ph
49
Ph
Ph 74
, R = 2-thiophenyl, 75%
aReaction conditions: (a) H2SO4, toluene, rt, 70%, 1.8:1 E/Z; (b)
(i) H2PtCl6, CH2Cl2, rt, 90%; (ii) HOAc, HCl, 120 °C, 60%; (c) (i)
PdCl2(PhCN)2, THF, rt, 95%; (ii) Et3SiH, BF3•Et2O, CH2Cl2, −78
°C, 85%; (d) Pd/C, H2, MeOH, rt, 68%; (e) Ni(OAc)2•4H2O,
NaBH4, H2, EtOH, rt, 98%; (f) InBr3, TMSCN, CH2Cl2, rt, 60%;
(g) SOCl2, pyridine, CH2Cl2, rt, 78%.
Ph
N
Ph
4-Me-C6H4
O
O
O
n-Bu
N
N
n-Bu
R
Ph
Ph
63
64
65
, R = 4-MeO-C6H4, 50%
, R = 4-F-C6H4, 50%
, R = 2-naphthyl, 57%
66
67
, 52% (only E)
, 63%
O
n-Bu
same as above
To further demonstrate the synthetic utility of the current
electrosynthesis, the difunctionalization reaction of 1 with 2 was
performed on a gram scale. Gratifyingly, the reaction generated the
expected product 3 in 62% yield (Scheme 4). Compound 3 could
be converted in one or two steps to various cyclic and acyclic
structures such as benzofulvene 71, naphthalene 72,
tetrahydrofuran 73, tertiary alcohol 74, homoallylic alcohol 49,
nitrile 75, and enyne 76.
+
2
Me
OH
(2.5 equiv)
Me
68
69
, 50%
F
n-Bu
Pt
C
2
1
+
Ph
Ph
70
HF
(3.0 equiv)
Et4NF•3
(5.5 equiv)
MeCN, 50 °C, 6 mA
, 62%
Further studies (Scheme 3) revealed the electrochemical alkene
difunctionalization reaction was compatible with other heteroatom
nucleophiles such as MeOH (50), tethered amide carbonyls (51–
67) or a hydroxyl group (68), and even fluoride (70). The
SET oxidation of aryl alkenes to generate the corresponding
radical cations can also be achieved using photocatalysis or
chemical oxidants such as cerium ammonium nitrate (CAN).
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 4 of 6
Particularly, Lei and coworkers reported that styrenyl alkenes could
The distinct outcome for the alkene functionalization under the
electrochemical conditions is attributable to the unique features of
electrochemical oxidation. Under the electrochemical conditions,
the alkene A is oxidized to the radical cation B on the anode
surface.18 Meanwhile, relatively high concentration of the anionic
organotrifluoroborate is probably attracted to the positively
charged anode surface.19 As a result, the radical cation B reacts
efficiently and preferentially with the organotrifluoroborate
reagent. However, cation E reacts selectively with H2O probably
due to the steric hindrance posed by the C–C bond formation
between two bulky coupling partners (C and E). The cation E was
therefore trapped by the less sterically demanding nucleophile H2O.
The sensitivity of the organotrifluoroborate reagents to steric
hindrance is also manifested in their low reaction efficiency with
trisubstituted alkenes that we tested.
1
2
3
4
5
6
7
8
undergo visible light induced oxidative functionalization with
various heteroatom-based nucleophiles via H2 evolution to give
mono functionalized products.14 Based on these findings, we
compared the efficiency of the non-electrochemical methods and
our electrolytic approach in promoting the functionalization of
alkene 1 with alkynyl trifluoroborate 2. As shown in Scheme 5,
subjecting the mixture of 1 and 2 under the same photochemical
conditions as reported14a led to formation of aldehyde 77 in 58%
yield without the observation of homopropargyl alcohol product 3.
In addition, treating the same reaction mixture with stoichiometric
CAN15 led to the formation benzophenone as the only identifiable
product. These results suggested that the alkene reacted
preferentially with H2O instead of the organoborate reagent under
these homogeneous conditions.
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
In summary, we have achieved regio- and chemoselective
hydroxy-alkynylation and -alkenylation reactions of aryl alkenes
using two easily available and stable nucleophiles. This method
takes advantage of the unique aspects of electrochemistry to enable
transformations that are difficult for alternative technologies. We
Scheme 5. Alkene Functionalization Reactions under Non-
electrochemical Conditions

cat. Acr+-Mes ClO4
Ph
cat. [Co]
1
+
2
(3 equiv)
(3 equiv)
3
, 0%
+
O
Ph
are
currently
assessing
the
synthetic
utility
of
MeCN/H2O (10:1)
blue LED, rt, 24 h
77
, 58%
organotrifluoroborates in other electrochemical hetero-
carbofunctionalization reactions of alkenes.
CAN (3 equiv)
KHCO3 (1.5 equiv)
Ph
O
1
+
2
3
+
, 0%
25%
Ph
ASSOCIATED CONTENT
Supporting Information
Full experimental details and characterization data. This material is
available free of charge via the Internet at http://pubs.acs.org.
MeCN/H2O (14:1)
50 °C, 4 h
1
(42% conversion of
)
Scheme 6. Mechanistic Proposal
e
cathode
anode
R1
AUTHOR INFORMATION
R2
A
B
e
Corresponding Author
R1
2H2O
2e
*E-mail: haichao.xu@xmu.edu.cn
R2
F3B R3
Author Contributions
§P.X. and H.L. contributed equally to this work.
C
BF3
2HO
+ H2
R1
R3
R2
R1
Notes
D
e
OH
The authors declare no competing financial interests.
H O
+
2
R3
R2
R3
E
R1
R2
 H+
F
ACKNOWLEDGMENT
[On surface]
Financial support of this research from MOST (2016YFA0204100)
NSFC (21672178) and the Fundamental Research Funds for the
Central Universities.
A
possible
mechanism
for
the
electrochemical
difunctionalization reaction is shown in Scheme 6. The reaction
begins with the anodic oxidation of the alkene A [Ep/2 (1) = 1.57 V
vs SCE] to produce the radical cation B,16 which is trapped by the
organotrifluoroborate reagent C [Ep/2 (2) = 2.06 V vs SCE] to
generate the C-centered radical D. The reactions of enamine radical
cations with alkenyltrifluoroborates have been proposed to proceed
via a stepwise mechanism involving formation of the C–C bond,
SET oxidation and cleavage of the C–B bond.9c However, the
stereospecific reaction of the alkenyltrifluoroborates in our work
suggests that such a mechanism is not operative here. The reaction
of B and C most likely proceeds through a concerted mechanism
with concomitant formation of the C–C bond and cleavage of the
C–B bond to release BF3. Density functional theory (DFT)-based
calculations on the reaction of alkene 1 derived radical cation with
an alkenyltrifluoroborate suggests a low activation barrier for such
a concerted mechanism (Figure S4). Anodic oxidation of D results
in the formation of the carbocation E, which then reacts with H2O
to afford the final alcohol product F. At the cathode, H2O is reduced
to furnish H2 and HO−. The latter is consumed by H+ produced
during the formation of F and the added bicarbonate, preventing
accumulation of HO−.17
REFERENCES
(1) (a) McDonald, R. I.; Liu, G.; Stahl, S. S. Chem. Rev. 2011, 111,
2981. (b) Jensen, K. H.; Sigman, M. S. Org. Biomol. Chem. 2008, 6, 4083.
(2) (a) Holt, D.; Gaunt, M. J. Angew. Chem., Int. Ed. 2015, 54, 7857. (b)
Nicolai, S.; Erard, S.; González, D. F.; Waser, J. Org. Lett. 2010, 12, 384.
(c) Hopkins, B. A.; Garlets, Z. J.; Wolfe, J. P. Angew. Chem., Int. Ed. 2015,
54, 13390. (d) Han, W.-J.; Wang, Y.-R.; Zhang, J.-W.; Chen, F.; Zhou, B.;
Han, B. Org. Lett. 2018, 20, 2960. (e) Bovino, M. T.; Liwosz, T. W.; Kendel,
N. E.; Miller, Y.; Tyminska, N.; Zurek, E.; Chemler, S. R. Angew. Chem.,
Int. Ed. 2014, 53, 6383. (f) Nicolai, S.; Piemontesi, C.; Waser, J. Angew.
Chem., Int. Ed. 2011, 50, 4680. (g) Shen, K.; Wang, Q. Chem. Sci. 2017, 8,
8265. (h) Mai, D. N.; Wolfe, J. P. J. Am. Chem. Soc. 2010, 132, 12157. (i)
Faulkner, A.; Scott, J. S.; Bower, J. F. J. Am. Chem. Soc. 2015, 137, 7224.
(3) Liu, Z.; Wang, Y.; Wang, Z.; Zeng, T.; Liu, P.; Engle, K. M. J. Am.
Chem. Soc. 2017, 139, 11261.
(4) Selected recent reviews on electroorganic synthesis: (a) Horn, E. J.;
Rosen, B. R.; Baran, P. S. ACS Cent. Sci. 2016, 2, 302. (b) Yan, M.;
Kawamata, Y.; Baran, P. S. Chem. Rev. 2017, 117, 13230. (c) Yan, M.;
Kawamata, Y.; Baran, P. S. Angew. Chem., Int. Ed. 2017, 57, 4149. (d)
Waldvogel, S. R.; Lips, S.; Selt, M.; Riehl, B.; Kampf, C. J. Chem. Rev.
2018, 118, 6706. (e) Yang, Q. L.; Fang, P.; Mei, T. S. Chin. J. Chem. 2018,
ACS Paragon Plus Environment

Page 5 of 6
Journal of the American Chemical Society
36, 338. (f) Tang, S.; Liu, Y.; Lei, A. Chem 2018, 4, 27. (g) Francke, R.;
(8) Darses, S.; Genet, J.-P. Chem. Rev. 2008, 108, 288. (b) Molander, G.
A. J. Org. Chem. 2015, 80, 7837.
(9) (a) Yasu, Y.; Koike, T.; Akita, M. Chem. Commun. 2013, 49, 2037.
(b) Fernandez Reina, D.; Ruffoni, A.; Al-Faiyz, Y. S. S.; Douglas, J. J.;
Sheikh, N. S.; Leonori, D. ACS Catal. 2017, 4126. (c) Kim, H.; MacMillan,
D. W. C. J. Am. Chem. Soc. 2008, 130, 398.
(10) (a) Ding, C.-H.; Hou, X.-L. Chem. Rev. 2011, 111, 1914. (b) Yus,
M.; González-Gómez, J. C.; Foubelo, F. Chem. Rev. 2011, 111, 7774. (c)
Diner, C.; Szabó, K. J. J. Am. Chem. Soc. 2017, 139, 2.
Little, R. D. Chem. Soc. Rev. 2014, 43, 2492. (h) Yoshida, J.-i.; Kataoka,
K.; Horcajada, R.; Nagaki, A. Chem. Rev. 2008, 108, 2265. (i) Moeller, K.
D. Chem. Rev. 2018, 118, 4817. (j) Nutting, J. E.; Rafiee, M.; Stahl, S. S.
Chem. Rev. 2018, 118, 4834. (k) Wiebe, A.; Gieshoff, T.; Möhle, S.;
Rodrigo, E.; Zirbes, M.; Waldvogel S. R. Angew. Chem., Int. Ed. 2018, 57,
5594. (l) Mohle, S.; Zirbes, M.; Rodrigo, E.; Gieshoff, T.; Wiebe, A.;
Waldvogel, S. R. Angew. Chem., Int. Ed. 2018, 57, 6018. (m) Sauermann,
N.; Meyer, T. H.; Qiu, Y.; Ackermann, L. ACS Catal. 2018, 8, 7086. (n)
Kärkäs, M. D. Chem. Soc. Rev. 2018, 47, 5786. (o) Yoshida, J.-i.; Shimizu,
A.; Hayashi, R. Chem. Rev. 2018, 118, 4702. (p) Ma, C.; Fang, P.; Mei, T.-S.
ACS Catal. 2018, 8, 7179. (q) Jiang, Y.; Xu, K.; Zeng, C. Chem. Rev. 2018,
118, 4485. (r) Sauer, G. S.; Lin, S. ACS Catal. 2018, 8, 5175.
1
2
3
4
5
6
7
8
(11) Please see Figure S1 for details and discussion.
(12) (a) Wu, X.; Davis, A. P.; Fry, A. J. Org. Lett. 2007, 9, 5633. (b)
Okajima, M.; Suga, S.; Itami, K.; Yoshida, J.-i. J. Am. Chem. Soc. 2005,
127, 6930.
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
(5) (a) Fu, N.; Sauer, G. S.; Saha, A.; Loo, A.; Lin, S. Science 2017, 357,
575. (b) Fu, N.; Sauer, G. S.; Lin, S. J. Am. Chem. Soc. 2017, 139, 15548.
(c) Ye, K.-Y.; Pombar, G.; Fu, N.; Sauer, G. S.; Keresztes, I.; Lin, S. J. Am.
Chem. Soc. 2018, 140, 2438. (d) Yuan, Y.; Chen, Y.; Tang, S.; Huang, Z.;
Lei, A. Sci. Adv. 2018, 4, eaat5312. (e) Wang, Y.; Deng, L.; Mei, H.; Du,
B.; Han, J.; Pan, Y. Green Chem. 2018, 20, 3444. (f) Belleau, B.; Au-Young,
Y. K. Can. J. Chem. 1969, 47, 2117. (g) Kojima, M.; Sakuragi, H.;
Tokumaru, K. Chem. Lett. 1981, 10, 1707. (h) Ashikari, Y.; Nokami, T.;
Yoshida, J.-i. Org. Lett. 2012, 14, 938. (i) Ashikari, Y.; Shimizu, A.;
Nokami, T.; Yoshida, J.-i. J. Am. Chem. Soc. 2013, 135, 16070. (j) Yan,
W.-q.; Lin, M.-y.; Little, R. D.; Zeng, C.-C. Tetrahedron 2017, 73, 764. (k)
Chen, J.; Yan, W. Q.; Lam, C. M.; Zeng, C. C.; Hu, L. M.; Little, R. D. Org.
Lett. 2015, 17, 986.
(13) Suzuki, J.; Tanigawa, M.; Inagi, S.; Fuchigami, T.
ChemElectroChem 2016, 3, 2078.
(14) (a) Zhang, G.; Hu, X.; Chiang, C.-W.; Yi, H.; Pei, P.; Singh, A. K.;
Lei, A. J. Am. Chem. Soc. 2016, 138, 12037. (b) Yi, H.; Niu, L.; Song, C.;
Li, Y.; Dou, B.; Singh, A. K.; Lei, A. Angew. Chem., Int. Ed. 2017, 56, 1120.
(15) Nair, V.; Deepthi, A. Chem. Rev. 2007, 107, 1862.
(16) Alkylalkenes are not suitable substrates because of their high
oxidation potentials. For the functionalization of trisubstituted alkylalkenes
using photochemical methods, see: Nguyen, T. M.; Nicewicz, D. A. J. Am.
Chem. Soc. 2013, 135, 9588.
(17) The reaction of the side product BF3 with H2O also produces acid
(HBF4): Wamser, C. A. J. Am. Chem. Soc. 1951, 73, 409.
(18) Sperry, J. B.; Wright, D. L. Chem. Soc. Rev. 2006, 35, 605.
(19) The absorption of alkynyltrifluoroborate 2 on a gold electrode was
observed by Raman spectroscopy. See Figure S5 for details.
(6) Feng, R.; Smith, J. A.; Moeller, K. D. Acc. Chem. Res. 2017, 50, 2346.
(7) The aziridination of trisubstituted alkenes via radical cations seems
to be an exception: Li, J.; Huang, W.; Chen, J.; He, L.; Cheng, X.; Li, G.
Angew. Chem., Int. Ed. 2018, 57, 5695.
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 6 of 6
1
2
3
4
5
6
7
8
OH
R3
KF3B
R3
R1
+
R2
R2
+
or
R1
R2
or
KF3B
OH
R3
[nucleophilic]
H2O
R1
[nucleophilic]
R3
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
6
ACS Paragon Plus Environment