Cobaloxime Catalysis: selective synthesis of alkenylphosphine oxides under visible light

Article abstract of DOI:10.1021/jacs.9b06920

Direct activation of H-phosphine oxide to react with an unsaturated carbon-carbon bond is a straightforward approach for accessing alkenylphosphine oxides, which shows significant applications in both synthetic and material fields. However, expensive metals and strong oxidants are typically required to realize the transformation. Here, we demonstrate the utility of earth-abundant cobaloxime to convert H-phosphine oxide into its reactive radical species under visible light irradiation. The radical species thus generated can be utilized to functionalize alkenes and alkynes without any external photosensitizer and oxidant. The coupling with terminal alkene generates E-alkenylphosphine oxide with excellent chemo- A nd stereoselectivity. The reaction with terminal alkyne yields linear E-alkenylphosphine oxide via neutral radical addition, while addition with internal ones generates cyclic benzophosphine oxides and hydrogen. Mechanistic studies on radical trapping experiments, electron spin resonance studies, and spectroscopic measurements confirm the formation of phosphinoyl radical and cobalt intermediates that are from capturing the electron and proton eliminated from H-phosphine oxide. The highlight of our mechanistic investigation is the dual role played by cobaloxime, viz., both as the visible light absorber to activate the P(O)-H bond as well as a hydrogen transfer agent to influence the reaction pathway. This synergetic feature of the cobaloxime catalyst preforming multiple functions under ambient condition provides a convergent synthetic approach to vinylphosphine oxides directly from H-phosphine oxides and alkenes (or alkynes).

Full text of DOI:10.1021/jacs.9b06920

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Article
Cobaloxime Catalysis: Selective Synthesis of
Alkenylphosphine Oxides under Visible Light
Wen-Qiang Liu, Tao Lei, Shuai Zhou, Xiu-Long Yang, Jian Li,
Bin Chen, Jayaraman Sivaguru, Chen-Ho Tung, and Li-Zhu Wu
J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/jacs.9b06920 • Publication Date (Web): 11 Aug 2019
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Journal of the American Chemical Society
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Cobaloxime Catalysis: Selective Synthesis of Alkenylphosphine
Oxides under Visible Light
Wen-Qiang Liu,a,b Tao Lei,a,b Shuai Zhou,a,b Xiu-Long Yang,a,b Jian Li,a,b Bin Chen,a,b Jayaraman
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Sivaguru,c Chen-Ho Tung,a,b and Li-Zhu Wu*,a,b
aKey Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and
Chemistry, The Chinese Academy of Sciences, Beijing 100190, P. R. China
bSchool of Future Technology, University of Chinese Academy of Sciences, Beijing 100049, P. R. China
cCenter for Photochemical Sciences and Department of Chemistry, Bowling Green State University, Bowling Green,
OH 43403, United States
ABSTRACT: Direct activation of H-phosphine oxide to react with unsaturated carbon-carbon bond is a straightforward
approach for accessing alkenylphosphine oxides, which shows significant applications in both synthetic and material
fields. However, expensive metals and strong oxidants are typically required to realize the transformation. Here, we
demonstrate the utility of earth-abundant cobaloxime to convert H-phosphine oxide into its reactive radical species
under visible light irradiation. The radical species thus generated can be utilized to functionalize alkenes and alkynes
without any external photosensitizer and oxidant. The coupling with terminal alkene generates E-alkenylphosphine
oxides with excellent chem- and stereo-selectivity. The reaction with terminal alkyne yields linear E-alkenylphosphine
oxide via neutral radical addition, while the addition with internal ones generates cyclic benzophosphine oxides and
hydrogen. Mechanistic studies on radical trapping experiments, electron spin resonance studies and spectroscopic
measurements confirm the formation of phosphinoyl radical and cobalt intermediates that are from capturing the
electron and proton eliminated from H-phosphine oxide. The highlight of our mechanistic investigation is the dual role
played by cobaloxime viz., both as the visible light absorber to activate the P(O)-H bond, as well as a hydrogen transfer
agent to influence the reaction pathway. This synergetic feature of the cobaloxime catalyst preforming multiple functions
under ambient condition provides a convergent synthetic approach to vinylphosphine oxides directly from H-phosphine
oxides and alkenes (or alkynes).
Cobaloxime
[e.g.
Co(dmgBF2)2(L)2,
dmg
=
INTRODUCTION
dimethylglyoximato, L = H2O, MeCN, etc.], initially
developed as a mimic of vitamin B12,11-13 was recognized
early on as a powerful catalyst for either hydrogen
Phosphine oxide represents an important class of units,
in which the installation of phosphine group into a
molecule significantly improves its bioavailability and
inherent optical and electronic characters.1-3 As such, the
development of a convenient means to access these
substrates has received considerable attention across
multiple disciplines. Common synthetic approaches to
this type of molecules include treatment of
prefunctionalized substrates with strong bases or use of
expensive transition metal catalysts.4-10 Recent interest in
the direct activation of H-phosphine oxide [P(O)H] to
construct CP bond is more atom-economical and
straightforward. However, the necessity of precious metal
catalysts and oxidants remains one of fundamental
limitations. With the aim of developing a suite of new
methods for cost-effective chemical synthesis that is both
efficient and eco-friendly, we become interested in the
use of earth-abundant metal complex for this
transformation with visible light.
evolution from proton14-16 or hydrogen atom transfer17-21
.
Rapid growth of photocatalysis in recent years has widely
extended the application of cobaloxime as an efficient
catalyst to carry out chemical transformations that occur
efficiently under mild conditions. A particularly useful
application corresponds to a Heck type coupling.22
Carreira et al reported an alkyl group derived from alkyl
halide underwent intra- and inter-molecular addition23, 24
to double bond followed by unsaturation to provide a
substituted olefin. The transformation proceeded upon
irradiation of a reaction vessel with visible light in the
presence of an amine base. Cobaloxime, combining with
photosensitizers, has also shown the ability to capture the
electrons and protons eliminated from the substrates for
cross-coupling reactions.25-39 In this regard, we questioned
whether cobaloxime could activate H-phosphine oxide
(for example, diphenylphosphine oxide) [P(O)H] to
afford phosphinoyl radical [P(O)·], and simultaneously
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Scheme 1. Optimization of cobaloxime catalysts
Page 2 of 8
capture the electron and proton eliminated from P(O)H
functionality. The generated intermediates such as CoIII-H
or CoII enabled transfer the hydrogen in situ in the
subsequent radical addition with alkene or alkyne, thus
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Ph
Ph
O
P
O
P
O
P
Ph
Ph
Cobaloxime
Ph
H
+
Ph
+
Ph
Ph
pyridine, blue LEDs
RT, 16 h, argon, DCM (6 mL)
Ph
Ph
Ph
3a
Ph
3a'
providing us
a new and direct strategy for the
1a
2a
construction of important phosphine oxides. With this in
mind, we carried out reaction of diphenylphosphine oxide
[P(O)H] and alkene in the presence of cobaloxime (in
dark), but unfortunately no reaction was observed.
However, visible light irradiation of the same reaction
vessel realized the activation of P(O)H bond by
cobaloxime. In contrast to well established photocatalytic
systems,40-42 the reaction proceeded smoothly without
external photosensitizer and sacrificial oxidant.
Cobaloxime directly initiated the photocatalytic reaction
of H-phosphine oxide [P(O)H] with alkene and alkyne to
selectively produce alkenylphosphine oxides in good to
excellent yields. In these transformations, both alkene
and alkyne were all well tolerated to afford
alkenylphosphine oxides. The high yields, excellent
selectivity, wide substrate scopes, mild reaction
conditions and the absence of external photosensitizer
and sacrificial oxidant demonstrated the great
photocatalytic activity of cobaloxime.
Cl
Cl
Cl
Me
Me
Me
H
O
H
O
H
O
O
N
N
N
Me
Me
Me
O
O
N
N
Co
N
Co
N
Co
N
N
O
O
Me
Me
O
H
Me
N
N
N
H
O
H
O
H
O
Me
4-CO2Mepy
Me
Me
9
py
Cl
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Co(dmgH)(dmgH2)Cl2
>99%, 2:1
Co(dmgH)2pyCl
>99%, 2:1
Co(dmgH)2(4-CO2Mepy)Cl
>99%, 2:1
F
MeOH
F
F
H2O
Me
MeCN
Me
Me
F
F
B
F
B
B
O
O
N
O
N
N
Me
F
Me
Me
F
O
O
O
N
N
N
Co
Co
Co
N
N
N
O
O
O
Me
Me
Me
N
N
N
B
B
O
O
B
O
F
Me
MeOH
Me
Me
MeCN
F
F
F
H2O
Co(dmgBF2)2(H2O)2
36%, >20:1
Co(dmgBF2)2(MeCN)2
90%, 9:1
Co(dmgBF2)2(MeOH)2
40%, >20:1
Reaction conditions: A solution of 1a (0.1 mmol), 2a (0.3
mmol), cobaloxime (10 mol %) and pyridine (0.2 mmol) in
DCM (6 mL) was irradiated with 3 W blue LEDs for 16 hours
at room temperature under argon atmosphere. The ratio is
3a to 3a’ detected by 1H NMR analysis.
RESULTS AND DISCUSSION
Cobaloxime catalyzed reaction of H-phosphine
oxide and terminal alkene. To evaluate our strategy, we
investigated the reaction of diphenylphosphine oxide 1a
and 1,1-diphenylethene 2a in the presence of 10 mol %
Co(dmgH)2pyCl, pyridine (2 equiv.) in CH2Cl2 at room
temperature. Upon irradiation with blue LEDs (450 ± 10
nm) for 16 hours, the reaction occurred smoothly with >
99% isolated yield of 3a and 3a’. The products were
characterized by NMR spectroscopy (1H, 13C and 31P NMR)
as well as high resolution mass spectroscopy (HRMS).
Careful analysis of the reaction mixture revealed a 2:1
ratio
of
alkenylphosphine
oxide
3a
and
Figure 1. UV-vis absorption spectra in DCM at room
temperature: 1a (green), 2a (gray), Co(dmgBF2)2(MeCN)2
(red), 1a and Co(dmgBF2)2(MeCN)2 (blue), irradiation with
blue LEDs of 1a and Co(dmgBF2)2(MeCN)2 for 60 s (purple).
[1a] = 1.0 × 10-3 M, [2a] = 1.0 × 10-3 M, [Co(dmgBF2)2(MeCN)2]
= 1.0 × 10-4 M.
hydrophosphorylation product 3a’ (Scheme 1). Further
variations on the ligands of cobaloxime complexes
showed that different cobaloximes with CoIII
(Co(dmgH)2pyCl, Co(dmgH)(dmgH2)Cl2), Co(dmgH)2(4-
CO2Mepy)Cl) and CoII (Co(dmgBF2)2(L)2, L = MeCN,
MeOH, H2O) were all suitable for carrying out the
chemical transformation. Among the investigated
cobaloxime, Co(dmgBF2)2(MeCN)2 displayed the best
photocatalytic activity that resulted in 90% yield with a
3a:3a’ ratio of 9:1 (Further optimization of condition see
Table S1). It became clear that cobaloxime itself was able
to promote the reaction to access alkenylphosphine oxide
3a without additional/sacrificial oxidant. This is
unprecedented in the reported reaction of H-phospine
oxide and olefins by metal catalysis43 or visible light
catalysis (Rhodmaine B)40 to afford hydrophosphorylation
product (alkylphosphine oxide 3a’). Our results for the
first time highlight the photo-catalytic ability of
cobaloxime in H-phosphine oxide reaction with alkene,
and opens up an efficient synthetic route to access vinyl
phosphine oxides,
which could be further functionalized, for example, to
give alkenyl phosphine (see Supporting Information, part
5).
As no reaction occurred in the absence of visible light
and cobaloxime, essential to this transformation was the
activation of P(O)-H bond by cobaloxime under visible
light irradiation. To confirm the interaction between H-
phosphine oxide and cobaloxime, both electrochemical
and spectroscopic studies were carried out. According to
electrochemical study, the oxidative potential of 1a was
E1a+/1a  1.0 V vs SCE40 and reductive potential of
Co(dmgBF2)2(CH3CN)2 was EII/I = -0.76 V vs SCE (Figure
S1). Obviously, this couple is unlikely to proceed electron
transfer from 1a to cobaloxime. However, photoexcited
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cobaloxime (excitation energy E00 = 2.67 eV; Figure S2)
alkenylphosphine oxide 3a and the multi-substituted
process for product was unlikely. Interestingly, reductive
product of 1,1-diphenylethene 2a in the reaction was
detected as the byproduct by gas chromatography-mass
spectrometry (GC-MS) and 1H NMR spectroscopy
(Scheme S3), revealing a selective hydrogen-transfer of
reduced cobaloxime into terminal alkene. Isotopic
experiment for deuterated 1,1-diphenylethene D-2a
further manifested the hydrogen transfer pathway
(Scheme S4). Thus, the cobaloxime performs a dual role
in the reaction mechanism, 1) as a photocatalyst to
activate [P(O)H] bond and 2) as a metal catalyst to
capture the electron and proton eliminated from H-
phosphine oxide and subsequently transfer the hydrogen
to terminal alkene. With this conjecture, we have
developed a mechanistic model shown in Scheme 3.
Photoexcitation of cobaloxime generated phosphinoyl
radical I that reacts with terminal olefin 2a affording
radical intermediate II. This intermediate II combined
with another CoII catalyst to form metallic intermediate
III. After removal of CoIIIH intermediate via β-H
elimination, the product 3a was obtained. As mentioned
above, the generated CoIIIH intermediate selectively
reduced 2a to 1,1-diphenylethane 2a’ (with a subsequent
formation of CoIII complex) rather than alkenyl phosphine
oxide 3a to hydrophosphorylation product 3a’, thus
leading to the high selectivity for alkenylphosphine oxide.
The very small amount of hydrophosphorylation product
probably came from the protonation of metallic
intermediate III. It is also plausible that the CoIII
intermediate can be reduced by intermediate II to return
its initial state and convert the latter into carbocation
intermediate, with removal of a proton to provide the
final vinyl product 3a. One cannot exclude the
featured a reductive potential of 1.91 V vs SCE (EII*/I = EII/I
+ E00) that enabled single electron transfer from 1a to
excited cobaloxime. UV-vis absorption spectra showed
that two reactants 1a and 2a do not absorb above 400 nm
light and only Co(dmgBF2)2(CH3CN)2 absorbs visible light
with an absorption maximum at 440 nm (Figure 1). When
diphenylphosphine oxide 1a was added into the solution
of cobaloxime, a strong peak at 320 nm was generated
along with the decrease at 440 nm. Subsequent
irradiation of this solution for 1 minute led to the
formation of a new signal at 620 nm indicative of CoI
species 35 (Figure 1). This result affirmed a photoinduced
electron transfer from diphenylphosphine oxide 1a to
cobaloxime under visible light irradiation. Moreover,
irradiating solution of 1a, 5,5-dimethyl-1-pyrroline N-
oxide (DMPO) and Co(dmgBF2)2(CH3CN)2 in DCE for 10
seconds and analyzing the sample by electron spin
resonance (ESR) provided a characteristic signal of
phosphinoyl radical44 (Scheme 2, Figure S7). Besides,
TEMPO and MNP as free radical trapping agents
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significantly
decreased
the
yields
of
target
alkenylphosphine oxide 3a from 99% to 34% and 23%,
respectively (Scheme 2, Scheme S1). A coupling product of
1
diphenylphosphine oxide and MNP was detected by H
NMR and HRMS, directly revealing the formation of
phosphinoyl radical.
Scheme 2. Radical-capture experiments
Ph
O
Standard Conditions
O
Ph
Ph
P
H
+
+
+
Ph
P
Ph
Ph
Ph
Ph
1a
2a
3a 3a'
+
, 94%, 9:1
Ph
Ph
O
Standard Conditions
O
Ph
Ph
P
H
H
Ph
P
TEMPO / MNP
Ph
Ph
Ph
Ph
Ph
regeneration
of
ground-state
cobaloxime
from
Ph
3a 3a'
1a
2a
2a
+
, 34% / 23%
photoinduced oxidation of substrate 1a by in situ
generated CoIII intermediate or disproportionation of CoIII
and CoI species.
O
O
Standard Conditions
P
Ph
P N
MNP
Ph
OH
Ph
Detected by 1HNMR, MS
1a
Scheme 3. A plausible mechanism for the reaction of
H-phosphine oxide and terminal alkene
O
P
O
P
Ph
H
Ph
Ph
Ph
Ph
Ph
Ph
1a
I
Ph
2a
*[Co]II
[Co]I
H+
[Co]III-H
Ph
O
P
Ph
Ph
II
[Co]II

2a'
h
Ph
Based on the above evidences, it is reasonable to
consider that visible light irradiation of cobaloxime
activated H-phosphine oxide leading to the generation of
phosphinoyl radical that reacts with alkene. Under our
optimized conditions, high selectivity for alkenyl product
Ph Ph
[Co]II
[Co]III
[Co]III
O
P
II
Ph
Ph
III
O
P
Ph
H
Ph
Ph
3a
Ph
3a
was
obtained
instead
of
the
expected
With understanding on the reaction mechanism, we
explored the generality of this cobaloxime catalyzed
reaction involving H-phosphine oxides and terminal
olefins. Scheme 4 summarizes the scope of this strategy
that highlights the following: a) Styrene derivatives 2
undergo phosphorylation with the retention of double
bond in good to excellent yields ranging from 52% to 99%
with high selectivity; b) For 1,1-diphenylethene derivatives,
substituents such as methyl, methoxy, fluoro, chloro and
hydrophosphorylation product 3a’. In order to confirm
this selectivity, the mixture of product 3a and
Hphosphorylation [P(O)-H] 1a was irradiated in the
presence of Co(dmgBF2)2(MeCN)2 that did not result in
H-phosphorylation and diphosphorous substituted
products (Scheme S2). The control study revealed that the
minor saturated Hphosphorylation product 3a’ did not
come from the further hydrogenation of generated
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Page 4 of 8
bromo on the aromatic ring were well tolerated (3b-3f) to
which reacted with alkenes with no additional
photosensiter and oxidant under mild condition.
1
2
3
4
5
6
7
8
afford the desired products in good to excellent yields (75-
99%); c) Besides 1,1-diphenylethene derivatives, this
transformation is applicable to common mono-
substituted styrene derivatives. Moderate to good yields
(52-64%) were obtained with up to 20:1 selectivity (ratio
Cobaloxime catalyzed reaction of H-phosphine
oxide and alkyne. Considering the excellent ability of
cobaloxime to promote the reaction of H-phosphine
oxides and alkenes, we envisioned that this
straightforward and environmentally friendly strategy
offered considerable advantages in both simplicity and
efficiency for the addition reaction of H-phosphine oxides
[P(O)-H] and alkynes. To our delight, via simple trials the
combination of cobaloxime and visible light was found to
catalyze the radical addition of [P(O)H] bond to alkynes.
As shown in Scheme 5, with 10 mol % Co(dmgH)2pyCl as
catalyst and 2 equivalent pyridine as base in 2 mL of
DCE/MeOH (v/v = 3/1), H-phosphine oxides and terminal
of alkenylphosphine oxide : alkylphosphine oxide)
irrespective of the steric and electronic variations (3g-3n).
The successful formation of 3e-3f and 3m-3n in good
yields with intact chloride and bromide provides a good
opportunity for post-synthetic functionalization; d) E-
isomer was exclusively obtained in the vinyl product; e)
With regard to H-phosphine oxides, diphenylphosphine
oxides bearing methyl or halogen gave the desired
products (3o-3s) in good yields although diethyl
phosphite was not suitable in this reaction. As exception,
para-methyl substituted one gave the desired product (3o)
only in 31% yield but > 20:1 selectivity. f) A large-scale
synthesis has been accomplished with 78% isolated yield
of 3a and > 20:1 (3a:3a’) selectivity, establishing its great
potential of the cobaloxime catalysis in organic synthesis.
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alkynes
reacted
smoothly
to
produce
linear
alkenylphosphine oxides with good E-selectivity (more
details for condition optimization see Table S2). From the
analysis of products (Scheme 5), following conclusions
could be obtained: a) For terminal alkynes, most
phenylacetylene derivatives bearing either electron-
donating or electron-withdrawing groups could obtain
their corresponding alkenylphosphine oxides with good
E-selectivity (5a-5p). Methoxyl (5h), halogen (5k-5m) and
strong electron-withdrawing groups such as cyano (5n),
ester (5o), trifluoromethyl (5p) were all compatible to
afford the corre
Scheme 4. Substrate Scope for the reaction of H-
phosphine oxide and terminal alkene
Ph
O
Co(dmgBF2)2(MeCN)2 (10 mol %)
O
P
Ph
Ar
P
H
+
Ar
pyridine (1 equiv.), blue LEDs
RT, 16 h, argon, DCM (2 mL)
Ph
Ph
(0.3 mmol)
Me
Ar
Ar
1
2
3
(0.1 mmol)
MeO
F
Scheme 5. Substrate Scope for the reaction of H-
phosphine oxide and terminal alkyne
O
P
O
P
O
P
O
P
Me
OMe
F
Ph
Cl
Ph
Ph
Ph
Ph
3a
Co(dmgH)2pyCl (10 mol %)
pyridine (2 equiv.), blue LEDs
R
Ph
Ph
Ph
3d
O
P
O
P
, 94%, 9:1;
78%; >20:1a
3b
3c
, 99%, 9:1
, 98%, 9:1
, 75%, 5:1
Me
+
H
Ar
Ph
R
24 h, argon, RT
DCE/MeOH (2 mL, v/v = 3/1)
Br
Ar
Ph
5
, yield, E/Z
1
4
(0.2 mmol)
(0.1 mmol)
O
P
Me
O
P
Ph
O
O
Cl
Br
Ph
O
P
O
P
O
P
O
P
Ph
Ph
Me
Ph
P
Ph
P
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
3e
3f
3g
3h
, 60%, >20:1
, 88%, 5:1
, 77%, 10:1
, 59%, >20:1
a
5a
5b
5c
5d
, 61%, 17:1
, 83%, 13:1
, 55%, 20:1
, 40%, >20:1
Me
tBu
Ph
F
O
P
O
P
O
P
OMe
tBu
OMe
O
P
O
P
O
P
O
P
O
P
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Me
Me
Ph
Ph
Ph
Ph
Ph
3i
a
a
a
a
3j
3k
3l
, 52%, >20:1
, 58%, >20:1
, 54%, >20:1
, 64%, >20:1
5e
5f
5g
5h
, 68%, 11:1
, 56%, 8:1
, 68%, 13:1
, 68%, 14:1
Ph
O
Me
Ph
O
P
Ph
O
P
O
P
O
P
O
P
G
F
Cl
CF3
Ph
Me
P
O
P
O
P
Cl
Br
Ph
Ph
Ph
Ph
O
Ph
Ph
Ph
Ph
5i
Ph
Ph
5k
Ph
Ph
Ph
b
a
a
5j
, 84%, >20:1
5l
, 71%, 7:1
, 60%, 7:1
, 56%, 8:1
Me
3p
Me
O
P
O
P
O
P
3m
3n
3o
Br
CN
CO2Me
Ph
, 63%, >20:1
Ph
, 54%, >20:1
, 31%, >20:1
, 77%, 9:1
Ph
Ph
P
Ph
O
P
Ph
O
P
Me
Ph
Ph
Ph
Ph
Ph
Ph
O
P
Ph
Ph
O
F
Cl
a
5o
, 77%, >20:1
5p
5n
, 41%, 17:1
, 75%, 13:1
5m
, 45%, 4:1
Ph
EtO
P
Me
O
P
O
P
OEt
Ph
O
P
Ph
MeO
Me
Me
, 58%, >20:1
F
Cl
3q
3r
3s
3t
, 0%
, 68%, 9:1
, 86%, 14:1
OMe
aThe reaction was carried out in 1 mmol 1a.
5q
5r
5s
, 78%, 17:1
, 72%, 11:1
, 80%, 14:1
O
P
O
P
Ph
Ph
Thus the selective installation of phosphine oxide onto
alkene scaffold opens up an important transformation in
synthetic and medicinal chemistry. By employing
cobaloxime as an efficient photocatalyst, we developed a
molecular catalytic system for alkenylphosphine oxide,
driven by visible light that forms phosphinoyl radicals,
F
Cl
O
P
Ph
EtO
OEt
F
Cl
5t
5u
5v
, 0%
, 76%, 17:1
, 64%, 10:1
b
aToluene was used as the solvent. G group represented 9H-
carbazol-9-yl substitution.
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Journal of the American Chemical Society
sponding alkenylphosphine oxides; b) Sterically hindered
and subsequently cyclized to generate intermediate VI
rather than direct hydrogenation, probably due to the
reactivity of internal triple bond.4, 7, 41, 49 Then hydrogen
atom abstraction by CoII complex produced the cyclic
product 7a and CoIIIH complex. In the absence of
external oxidant, the captured proton and electron by
cobaloxime (CoIIIH) was released as hydrogen (detected
by GC, Scheme S7). Although cobaloximes are able to
mediate some photoredox cycles, 22-39 all examples known
so far (i) do not use the cobaloxime as the light harvesting
moiety and (ii) include H2 evolution mediated by
hydridocobaloxime. Our method afforded a novel and
efficient approach for cyclic benzophosphole oxide
without any external oxidant, which is different from
previous works using strong oxidant like N-
methoxypyridinium salts.41
1
2
3
4
5
6
7
8
2-ethynyl-1,1'-biphenyl (5b) gave a lower yield compared
with 4-ethynyl substitution one (5a). Different location of
methyl group in phenylacetylene resulted in similar yields
of products (5d-5f). Bulky substituents like tert-butyl
group (5g) were compatible to afford the corresponding
products in a 68% yield; c) Alkyne substrates with
heterocycle and extended conjugation were also
compatible in this reaction. Carbazole (5i) and
naphthalene derivatives (5j) gave isolate yields of 71% and
84%, respectively; d) In terms of diphenylphosphine oxide
derivatives, electron-donating and electron-withdrawing
groups on the phenyl ring were all compatible with our
reaction conditions. The substrates bearing p-methyl, 2,5-
dimethyl, p-methoxyl, p-fluoro, p-chloro performed well
with yields ranging from 64%-80% (5q-5u).
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17
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21
22
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A unique aspect of our methodology when compared to
previous reports is that such reactions mostly relied on
metal catalyzed oxidative addition/insertion/reductive
elimination pathway(s). 45, 46 As an alternative, free radical
addition process of H-phosphine oxides to alkynes only
limited to benzoyl peroxide,47 and Eosin Y42 systems,
which provided a Z/E mixture or Z isomer. Our
photochemical result by coblaoxime, however, is highly E-
selective as showed by the reaction cycle depicted in
Scheme 6 (left). Photoexcitation of cobaloxime activates
P(O)H bond resulting in phosphinoyl centered radical I
that was characterized by ESR (Figure S8) and radical
trapping experiment (TEMPO as radical capture, Figure
S5). Subsequent addition of phosphinoyl intermediate I to
4a gave rise to carbon center radical IV48 (Figure S8),
which combined with CoII intermediate to form
intermediate V. Protonation of intermediate V finally
provided H-phosphorylation product 5a, accompanied
with the regeneration of initial CoIII complex which closed
the catalytic cycle without the need for external oxidant
and reductant.
By employing 15 mol % Co(dmgH)2pyCl as photocatalyst
and 2 equivalent sodium formate as base in DCM, we
examined the generality of this reaction (more details for
condition optimization see Table S3-S4). As shown in
Scheme 7, this cobaloxime catalyzed cyclization was also
robust and efficient for H-phosphine oxide and internal
alkyne substrates. It was found that electron-withdrawing
internal aryl alkynes (p-FPh, p-ClPh, p-CF3Ph) showed
higher reactivity than donating ones (7b-7c, 7f). Long
carbon chain Bu and sterically hindered Bu groups in
diarylacetylenes had no/minimal effect on the
transformation, producing the desired products 7d and 7e
in good yields. Bromo-substituted diarylacetylene reacted
with diphenylphosphine oxide gave 43% yield, likely due
to its poor solubility in DCM. In addition to aryl alkynes,
aliphatic alkynes also showed good reactivity under our
optimized conditions. Both hex-3-yne 6k and dodec-6-
yne 6l reacted with diphenylphosphine oxide smoothly to
give corresponding products in 62% and 56% yields
n
t
respectively.
Significantly,
the
reaction
with
unsymmetrical phenylacetylenes like silylethynylbenzene
and methyl cinnamate exhibited high regioselectivity,
converting into single isomer 7m and 7n with yields of 90%
and 53% respectively. With regard to the exploration of
H-phosphine oxide, para-substitution of aryl group led to
Scheme 6. A plausible mechanism for the reaction of
H-phosphine oxide and alkyne
CoIII
H2
H+
Ph
H+
partial
rearrangement.
For
example,
bis(4-
O
P
CoIII-H
methylphenyl)phosphine oxide and diphenylacetylene
under the standard conditions gave both the normal
product (7o, 5’) and the isomer (7o, 6’) in 1:1 ratio with 64%
yield. A similar result of 7p (5’:6’ = 2:1) was observed for
the reactivity of bis(4-fluorophenyl)phosphine oxide and
diphenylacetylene leading to 7p and 7p', respectively.
O
Ph-4-Ph
Ph
h
Ph
P
Ph
CoIII
O
Ph
Ph-4-Ph
5a
7a
*CoIII
Ph
P
e-
+
,
H
V
Ph
O
O
Ph
P
H
Ph
P
H
Ph
1a
Ph
CoII
CoII
1a
O
P
Ph
Terminal Alkyne
Ph-4-Ph
IV
Internal Alkyne
Ph
Ph
CONCLUSION
O
H
VI
Ph
P
O
4a
6a
Ph
In summary, we have developed a straightforward
strategy for the synthesis of alkenylphosphine oxides via
free radical pathway under extremely mild reaction
conditions, by using inexpensive and easily accessible
cobaloxime complex as the photocatalyst. Our
methodology is compatible with a variety of terminal
alkenes, terminal alkynes and internal alkynes with high
yields and selectivity. Mechanistic studies demonstrated
Ph
P
Ph
Ph
Ph 4-Ph
I
Ph
In terms of internal alkynes, the same cobaloxime
catalysis indicated a radical addition yielding cyclic
benzophosphole
oxide
rather
than
linear
hydrophosphorylation product. As shown in Scheme 6
(right), phosphinoyl radical I reacted with internal alkyne
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Journal of the American Chemical Society
Page 6 of 8
JSC029), and K. C. Wong Education Foundation. Jayaraman
that cobaloxime not only absorbs the visible light to
activate the [P(O)-H] functionality, but also realizes the
hydrogen capture and transfer in situ for selective
synthesis of alkenylphosphine oxide under redox-neutral
condition. Integrity of multiple functions into this single
1
2
3
4
Sivaguru is grateful to the Chinese Academy of Sciences
President’s International Fellowship (2018VCA0001). We
thank Professor Wenguang Wang at Shandong University for
stimulating discussion on the reaction mechanism.
5
6
7
8
cobaloxime offers
a unique alternative to existing
REFERENCES
procedures. We believe the present work not only
provides a uniform strategy from H-phosphine oxide and
unsaturated carbon bonds for the simple and practical
preparation of alkenylphosphine oxides, but also
manifests the value-added potential of cobaloxime in
photocatalysis.
(1) Moonen, K.; Laureyn, I.; Stevens, C. V., Synthetic Methods
for Azaheterocyclic Phosphonates and Their Biological Activity.
Chem. Rev. 2004, 104, 6177-6216.
(2) Baumgartner, T.; Réau, R., Organophosphorus π-
Conjugated Materials. Chem. Rev. 2006, 106, 4681-4727.
(3) Montchamp, J.-L., Phosphinate Chemistry in the 21st
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
Century:
A Viable Alternative to the Use of Phosphorus
Scheme 7. Substrate Scope for the reaction of H-
phosphine oxide and internal alkyne
Trichloride in Organophosphorus Synthesis. Acc. Chem. Res.
2014, 47, 77-87.
(4) Chen, Y.-R.; Duan, W.-L., Silver-Mediated Oxidative C–
H/P–H Functionalization: An Efficient Route for the Synthesis of
Benzo[b]phosphole Oxides. J. Am. Chem. Soc. 2013, 135, 16754-
16757.
(5) Feng, C.-G.; Ye, M.-C.; Xiao, K.-J.; Li, S.-H.; Yu, J.-Q.,
Pd(II)-Catalyzed Phosphorylation of Aryl C–H Bonds. J. Am.
Chem. Soc. 2013, 135, 9322-9325.
(6) Li, Y.-M.; Sun, M.; Wang, H.-L.; Tian, Q.-P.; Yang, S.-D.,
Direct Annulations Toward Phosphorylated Oxindoles: Silver-
Catalyzed Carbon-Phosphorus Functionalization of Alkenes.
Angew. Chem. Int. Ed. 2013, 52, 3972-3976.
(7) Unoh, Y.; Hirano, K.; Satoh, T.; Miura, M., An Approach to
Benzophosphole Oxides Through Silver- or Manganese-
Mediated Dehydrogenative Annulation Involving C-C and C-P
Bond Formation. Angew. Chem. Int. Ed. 2013, 52, 12975-12979.
(8) Zhou, Y.; Gan, Z.-J.; Su, B.; Li, J.; Duan, Z.; Mathey, F.,
Intramolecular, Pd/Cu-Co-catalyzed P–C Bond Cleavage and
Addition onto an Alkyne: A Route to Benzophospholes. Org. Lett.
2015, 17, 5722-5724.
R2
Co(dmgH)2pyCl (15 mol %)
HCOONa (2 equiv.), DCM (2 mL)
R1
O
R1
Ar
P
H
+
R
60 oC, 20 h, argon, blue LEDs
P
R2
Ar
O
Ar
7
1
6
(0.2 mmol)
(0.1 mmol)
Me
nBu
Me
Me
Me
OMe
CF3
nBu
P
O
P
P
P
O
Ph
O
O
Ph
Ph
Ph
7a
7b
7c
7d
, 80%
tBu
, 60%
, 62%
F
, 69%
Cl
OMe
tBu
F
Cl
P
P
P
P
O
O
O
O
Ph
Ph
Ph
Ph
7e
7f
7g
7h
, 77%
, 69%
Br
, 54%
CF3
, 79%
(9) Sato, Y.; Kawaguchi, S.; Nomoto, A.; Ogawa, A., Highly
Selective
P
Phosphinylphosphination
of
Alkenes
with
O
Br
Ph
P
P
P
Tetraphenyldiphosphine Monoxide. Angew. Chem. Int. Ed. 2016,
55, 9700-9703.
(10) Guo, H.-M.; Zhou, Q.-Q.; Jiang, X.; Shi, D.-Q.; Xiao, W.-J.,
Catalyst- and Oxidant-Free Desulfonative C−P Couplings for the
Synthesis of Phosphine Oxides and Phosphonates. Adv. Synth.
Catal. 2017, 359, 4141-4146.
(11) Schrauzer, G. N., Organocobalt Chemistry of Vitamin B12
Model Compounds (Cobaloximes). Acc. Chem. Res. 1968, 1, 97-
103.
(12) Schrauzer, G. N., New Developments in the Field of
Vitamin B12: Reactions of the Cobalt Atom in Corrins and in
Vitamin B12 Model Compounds. Angew. Chem. Int. Ed. 1976, 15,
417-426.
(13) Giedyk, M.; Goliszewska, K.; Gryko, D., Vitamin B12
Catalysed Reactions. Chem. Soc. Rev. 2015, 44, 3391-3404.
(14) Artero, V.; Chavarot-Kerlidou, M.; Fontecave, M.,
Splitting Water with Cobalt. Angew. Chem. Int. Ed. 2011, 50,
7238-7266.
(15) Dempsey, J. L.; Brunschwig, B. S.; Winkler, J. R.; Gray, H.
B., Hydrogen Evolution Catalyzed by Cobaloximes. Acc. Chem.
Res. 2009, 42, 1995-2004.
(16) Wu, L.-Z.; Chen, B.; Li, Z.-J.; Tung, C.-H., Enhancement of
the Efficiency of Photocatalytic Reduction of Protons to
Hydrogen via Molecular Assembly. Acc. Chem. Res. 2014, 47,
2177-2185.
(17) Gjerde, H. B.; Espenson, J. H., Concurrent and
Competitive Homolysis and Elimination Reactions of (Alpha-
phenylethyl)aquocobaloxime. Organometallics 1982, 1, 435-440.
O
O
O
Ph
5'
Ph
Ph
7i
7j
7k
7l
, 43%
, 62%
, 62%
, 56%
Ph
Ph
5'
Ph
Ph
Me
Ph
F
Ph
6'
6'
P
P
Si
CO2CH3
O
O
P
P
O
O
Ph
Ph
Me
F
7m
7n
7o
7p
, 72%, 5':6' = 2:1
, 90%
, 53%
, 64%, 5':6' = 1:1
ASSOCIATED CONTENT
Supporting Information. The experimental procedure,
1
13
31
characterization data, and copies of H, C, 19F, and P NMR
spectra. The Supporting Information is available free of
charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
*lzwu@mail.ipc.ac.cn
ACKNOWLEDGMENT
This work was supported by the Ministry of Science and
Technology of China (2017YFA0206903), the National
Natural Science Foundation of China (21861132004), the
Strategic Priority Research Program of the Chinese Academy
of Science (XDB17000000), Key Research Program of Frontier
Sciences of the Chinese Academy of Science (QYZDY-SSW-
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(18) Choi, J.; Tang, L.; Norton, J. R., Kinetics of Hydrogen
Atom Transfer from (η5-C5H5)Cr(CO)3H to Various Olefins:ꢀ
Influence of Olefin Structure. J. Am. Chem. Soc. 2007, 129, 234-
240.
(34) He, K.-H.; Tan, F.-F.; Zhou, C.-Z.; Zhou, G.-J.; Yang, X.-L.;
Li, Y., Acceptorless Dehydrogenation of N-Heterocycles by
Merging Visible-Light Photoredox Catalysis and Cobalt Catalysis.
Angew. Chem. Int. Ed. 2017, 56, 3080-3084.
(35) Zhong, J.-J.; Wu, C.-J.; Meng, Q.-Y.; Gao, X.-W.; Lei, T.;
Tung, C.-H.; Wu, L.-Z., A Cascade Cross-Coupling and in Situ
Hydrogenation Reaction by Visible Light Catalysis. Adv. Synth.
Catal. 2014, 356, 2846-2852.
(36) Yang, Q.; Zhang, L.; Ye, C.; Luo, S.-Z.; Wu, L.-Z.; Tung, C.-
H., Visible-Light-Promoted Asymmetric Cross-Dehydrogenative
Coupling of Tertiary Amines to Ketones by Synergistic Multiple
Catalysis. Angew. Chem. Int. Ed. 2017, 56, 3694-3698.
(37) Yang, X.-L.; Guo, J.-D.; Lei, T.; Chen, B.; Tung, C.-H.; Wu,
L.-Z., Oxidative Cyclization Synthesis of Tetrahydroquinolines
and Reductive Hydrogenation of Maleimides under Redox-
Neutral Conditions. Org. Lett. 2018, 20, 2916-2920.
(38) Cao, H.; Jiang, H.-M.; Feng, H.-Y.; Kwan, J. M. C.; Liu, X.-
G.; Wu, J., Photo-induced Decarboxylative Heck-Type Coupling
of Unactivated Aliphatic Acids and Terminal Alkenes in the
Absence of Sacrificial Hydrogen Acceptors. J. Am. Chem. Soc.
2018, 140, 16360-16367.
(39) Yu, W.-L.; Luo, Y.-C.; Yan, L.; Liu, D.; Wang, Z.-Y.; Xu, P.-
F., Dehydrogenative Silylation of Alkenes for the Synthesis of
Substituted Allylsilanes via Photoredox, HAT, and Cobalt
1
2
3
4
5
6
7
8
(19) Li, G.; Han, A.; Pulling, M. E.; Estes, D. P.; Norton, J. R.,
Evidence for Formation of
a
Co–H Bond from
(H2O)2Co(dmgBF2)2 under H2: Application to Radical
Cyclizations. J. Am. Chem. Soc. 2012, 134, 14662-14665.
(20) Estes, D. P.; Grills, D. C.; Norton, J. R., The Reaction of
Cobaloximes with Hydrogen: Products and Thermodynamics. J.
Am. Chem. Soc. 2014, 136, 17362-17365.
(21) Li, G.; Kuo, J. L.; Han, A.; Abuyuan, J. M.; Young, L. C.;
Norton, J. R.; Palmer, J. H., Radical Isomerization and
Cycloisomerization Initiated by H• Transfer. J. Am. Chem. Soc.
2016, 138, 7698-7704.
(22) Ikeda, Y.; Nakamura, T.; Yorimitsu, H.; Oshima, K.,
Cobalt-Catalyzed Heck-Type Reaction of Alkyl Halides with
Styrenes. J. Am. Chem. Soc. 2002, 124, 6514-6515.
(23) Weiss, M. E.; Kreis, L. M.; Lauber, A.; Carreira, E. M.,
Cobalt-Catalyzed Coupling of Alkyl Iodides with Alkenes:
Deprotonation of Hydridocobalt Enables Turnover. Angew.
Chem. Int. Ed. 2011, 50, 11125-11128.
(24) Kreis, L. M.; Krautwald, S.; Pfeiffer, N.; Martin, R. E.;
Carreira, E. M., Photocatalytic Synthesis of Allylic
Trifluoromethyl Substituted Styrene Derivatives in Batch and
Flow. Org. Lett. 2013, 15, 1634-1637.
(25) Liu, Q.; Wu, L.-Z., Recent Advances in Visible-Light-
Driven Organic Reactions. Natl. Sci. Rev. 2017, 4, 359-380.
(26) Chen, B.; Wu, L.-Z.; Tung, C.-H., Photocatalytic
Activation of Less Reactive Bonds and Their Functionalization
via Hydrogen-Evolution Cross-Couplings. Acc. Chem. Res. 2018,
51, 2512-2523.
(27) Meng, Q.-Y.; Zhong, J.-J.; Liu, Q.; Gao, X.-W.; Zhang, H.-
H.; Lei, T.; Li, Z.-J.; Feng, K.; Chen, B.; Tung, C.-H.; Wu, L.-Z., A
Cascade Cross-Coupling Hydrogen Evolution Reaction by Visible
Light Catalysis. J. Am. Chem. Soc. 2013, 135, 19052-19055.
(28) Zhong, J.-J.; Meng, Q.-Y.; Liu, B.; Li, X.-B.; Gao, X.-W.; Lei,
T.; Wu, C.-J.; Li, Z.-J.; Tung, C.-H.; Wu, L.-Z., Cross-Coupling
Hydrogen Evolution Reaction in Homogeneous Solution without
Noble Metals. Org. Lett. 2014, 16, 1988-1991.
(29) Gao, X.-W.; Meng, Q.-Y.; Li, J.-X.; Zhong, J.-J.; Lei, T.; Li,
X.-B.; Tung, C.-H.; Wu, L.-Z., Visible Light Catalysis Assisted
Site-Specific Functionalization of Amino Acid Derivatives by C–
H Bond Activation without Oxidant: Cross-Coupling Hydrogen
Evolution Reaction. ACS Catal. 2015, 5, 2391-2396.
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
Catalysis.
Angew.
Chem.
Int.
Ed.
2019.
doi:
10.1002/anie.201904707
(40) Yoo, W.-J.; Kobayashi, S., Hydrophosphinylation of
Unactivated Alkenes with Secondary Phosphine Oxides under
Visible-Light Photocatalysis. Green Chem. 2013, 15, 1844-1848.
(41) Quint, V.; Morlet-Savary, F.; Lohier, J.-F.; Lalevée, J.;
Gaumont, A.-C.; Lakhdar, S., Metal-Free, Visible Light-
Photocatalyzed Synthesis of Benzo[b]phosphole Oxides:
Synthetic and Mechanistic Investigations. J. Am. Chem. Soc. 2016,
138, 7436-7441.
(42) Wang, H.-M.; Li, Y.-L.; Tang, Z.-L.; Wang, S.-C.; Zhang,
H.; Cong, H.-J.; Lei, A.-W., Z-Selective Addition of Diaryl
Phosphine Oxides to Alkynes via Photoredox Catalysis. ACS
Catal. 2018, 8, 10599-10605.
(43) Shulyupin, M. O.; Kazankova, M. A.; Beletskaya, I. P.,
Catalytic Hydrophosphination of Styrenes. Org. Lett. 2002, 4,
761-763.
(44) Li, Z.-J.; Fan, F.-H.; Zhang, Z.-Y.; Xiao, Y.-X.; Liu, D.; Liu,
Z.-Q.,
A
Silver-Initiated
Free-Radical
Intermolecular
Hydrophosphinylation of Unactivated Alkenes. RSC Adv. 2015, 5,
27853-27856.
(45) Han, L.-B.; Hua, R.-M.; Tanaka, M., Phosphinic Acid
Induced Reversal of Regioselectivity in Pd-Catalyzed
Hydrophosphinylation of Alkynes with Ph2P(O)H. Angew. Chem.
Int. Ed. 1998, 37, 94-96.
(46) Han, L.-B.; Zhang, C.; Yazawa, H.; Shimada, S., Efficient
and Selective Nickel-Catalyzed Addition of H−P(O) and H−S
Bonds to Alkynes. J. Am. Chem. Soc. 2004, 126, 5080-5081.
(47) Coudray, L.; Montchamp, J. L., Recent Developments in
the Addition of Phosphinylidene-Containing Compounds to
Unactivated Unsaturated Hydrocarbons: Phosphorus-Carbon
Bond-Formation via Hydrophosphinylation and Related
Processes. Eur. J. Org. Chem. 2008, 21, 3601-3613.
(48) Liu, W.-Q.; Lei, T.; Song, Z.-Q.; Yang, X.-L.; Wu, C.-J.;
Jiang, X.; Chen, B.; Tung, C.-H.; Wu, L.-Z., Visible Light
Promoted Synthesis of Indoles by Single Photosensitizer under
Aerobic Conditions. Org. Lett. 2017, 19, 3251-3254.
(30) Zhang, G.-T.; Liu, C.; Yi, H.; Meng, Q.-Y.; Bian, C.-L.;
Chen, H.; Jian, J.-X.; Wu, L.-Z.; Lei, A.-W., External Oxidant-Free
Oxidative Cross-Coupling:
A Photoredox Cobalt-Catalyzed
Aromatic C–H Thiolation for Constructing C–S Bonds. J. Am.
Chem. Soc. 2015, 137, 9273-9280.
(31) Wu, C.-J.; Meng, Q.-Y.; Lei, T.; Zhong, J.-J.; Liu, W.-Q.;
Zhao, L.-M.; Li, Z.-J.; Chen, B.; Tung, C.-H.; Wu, L.-Z., An
Oxidant-Free Strategy for Indole Synthesis via Intramolecular C–
C Bond Construction under Visible Light Irradiation: Cross-
Coupling Hydrogen Evolution Reaction. ACS Catal. 2016, 6,
4635-4639.
(32) Li, Z.-J.; Zhan, F.; Xiao, H.-Y.; Zhang, X.-Y.; Kong, Q.-Y.;
Fan, X.-B.; Liu, W.-Q.; Huang, M.-Y.; Huang, C.; Gao, Y.-J.; Li, X.-
B.; Meng, Q.-Y.; Feng, K.; Chen, B.; Tung, C.-H.; Zhao, H.-F.; Tao,
Y.; Wu, L.-Z., Tracking Co(I) Intermediate in Operando in
Photocatalytic Hydrogen Evolution by X-ray Transient
Absorption Spectroscopy and DFT Calculation. J. Phys. Chem.
Lett. 2016, 7, 5253-5258.
(49) Ma, D.-M.; Chen, W.-Z.; Hu, G.-B.; Zhang, Y.; Gao, Y.-X.;
Yin, Y.-W.; Zhao, Y.-F., K2S2O8-Mediated Metal-Free Direct P–
H/C–H
Functionalization:
A
Convenient
Route
to
(33) Zheng, Y.-W.; Chen, B.; Ye, P.; Feng, K.; Wang, W.-G.;
Meng, Q.-Y.; Wu, L.-Z.; Tung, C.-H., Photocatalytic Hydrogen-
Evolution Cross-Couplings: Benzene C–H Amination and
Hydroxylation. J. Am. Chem. Soc. 2016, 138, 10080-10083.
Benzo[b]phosphole Oxides from Unactivated Alkynes. Green
Chem. 2016, 18, 3522-3526.
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