Photoredox/Cobalt-Catalyzed Phosphinyloxy Radical Addition/Cyclization Cascade: Synthesis of Phosphaisocoumarins

Article abstract of DOI:10.1021/acs.joc.9b00570

A novel visible-light photoredox-catalyzed phosphinyloxy radical addition/cyclization cascade of arylphosphinic acids or arylphosphonic acid monoesters with alkynes has been developed, which provides an efficient and practical access to various phosphaisocoumarins by using a dual catalytic system containing an acridinium photosensitizer and a cobaloxime proton-reducing catalyst [Co(dmgH)₂]PyCl at ambient temperature. This method has advantages of a broad substrate scope, mild condition, as well as no sacrificial oxidant.

Full text of DOI:10.1021/acs.joc.9b00570

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Article
A Photoredox/Cobalt-Catalyzed Phosphinyloxy Radical addition/
Cyclization Cascade: Synthesis of Phosphaisocoumarins
Ming-ming Qiao, Yi-Yin Liu, Sheng Yao, Tian-Cong Ma, Zi-Long Tang, De-Qing Shi, and Wen-Jing Xiao
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.9b00570 • Publication Date (Web): 16 May 2019
Downloaded from http://pubs.acs.org on May 16, 2019
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A Photoredox/Cobalt-Catalyzed Phosphinyloxy Radical Addition/Cyclization
Cascade: Synthesis of Phosphaisocoumarins
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Ming-Ming Qiao1, Yi-Yin Liu1, Sheng Yao1, Tian-Cong Ma1, Zi-Long Tang2, De-Qing Shi1*, Wen-Jing
Xiao1,3
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1CCNU-uOttawa Joint Research Centre, Key Laboratory of Pesticide and Chemical Biology, Ministry
of Education, College of Chemistry, Central China Normal University, 152 Luoyu Road, Wuhan
430079, China
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2College of Chemistry and Chemical Engineering, Hunan University of Science and Technology,
Xiangtan, Hunan 411201, China
3State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou 730000, China
chshidq@mail.ccnu.edu.cn
O
R2
O
P
hv
Co
R2
O
P
O
R1
H
R3
R4
H2
+
+
R1
O
P
R4
R2
O
via
R1
H
R3
24 examples
up to 83% yield
 gram-scale synthesis
 no stoichiometric oxidant
 ambient temperature
Abstract
A novel visible-light photoredox catalyzed phosphinyloxy radical addition/cyclization cascade of
arylphosphinic acids or arylphosphonic acid monoesters with alkynes has been developed, which
provides an efficient and practical access to various phosphaisocoumarins by using a dual catalytic
system containing an acridinium photosensitizer and a cobaloxime proton-reducing catalyst,
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[Co(dmgH)2]PyCl at ambient temperature. This method has advantages of broad substrate scope, mild
condition as well as without any sacrificial oxidant.
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Introduction
Organophosphorus compounds are of great importance not only in many functional materials and
bioactive fine chemicals, such as agrochemicals, pharmaceuticals and natural products, 1 but also as
synthetic reagents in organic synthesis, versatile phosphine ligands in transition metal catalysis or
nucleophilic organo-catalysts.2 Generally speaking, phosphorus substituents can regulate important
biological, medicinal and materials functions, so, heterocycles containing phosphorus or phosphonyl
group are received considerable attention to organic and medicinal chemists (Figure 1). 1
Figure 1. Some important biologically active P-containing molecules.
Phosphaisocoumarin, as a phosphorus analogue of isocoumarins, displayed versatile and interesting
biological activies.3 In 2013, Ding group first reported the preparation of phosphaisocoumarins by
Cu(I)-catalyzed intramolecular cyclization of o-ethynylphenylphosphonic acid monoesters (Scheme
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1a).4a After that, Peng reported the CuX2 (X = Br, Cl) mediated direct halocyclization for the synthesis
of 4-halophosphaisocoumarins (Scheme 1a).4b Afterwards, Lee developed rhodium- and ruthenium-
catalyzed oxidative C–H activation/cyclization for the synthesis of phosphaisocoumarins using
arylphosphinic acids or arylphosphonic acid monoesters and alkynes as the starting materials (Scheme
1b).5 Despite these remarkable advances, in order to achieve good yields, stoichiometric oxidant or
elevated temperature is usually required in these transformations. In this regard, the development of an
efficient and environmentally benign method for the synthesis of phosphaisocoumarins is still highly
desirable.
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Recently, visible-light photoredox catalysis has attracted increasing research interest from synthetic
community due to its extremely mild condition and environmental friendly character,6 and a
photoredox/cobaloxime dual catalytic system provides a new strategy for the construction of a variety of
heterocycles without external oxidants.7 Herein, we developed an unprecedented visible-light
photoredox-catalyzed phosphinyloxy radical formation by O−H cleavage of arylphosphinic acids or
arylphosphonic acid monoesters with H2 release in the presence of a cobalt catalyst, and its application
in the synthesis of a variety of phosphaisocoumarins through the phosphinyoxy radical
addition/cyclization with alkynes in high atom-economy at ambient temperature is accomplished
(Scheme 1c).
Scheme 1 Preparation of phosphaisocoumarins
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(a) Ding and Peng's work:
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OEt
O
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O OEt
OEt
P
R1
Cu
Pd
Cat.
R2
Cat.
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R1
X
R2
R2
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R1= OH, OEt
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O OR3
O
P
OR3
P
CuX2
OR3
O
R1
R1
R2
n-Bu4NX, DCE
R2
X
(b) Lee's work:
O R2
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Rh or Ru
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+
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R1
R4
H
R3
(c) This work: photoredox catalyzed phosphinyloxy radical addition/cyclization cascade
O
O
P
R2
O
R2
P
R1
H
O
+
R1
H2
R4
photoredox and Co(III) catalysis
H
R3
room temperature
-H+
e-
-e
-H
no stoichiometric oxidant
O
P
O
R2
R2
P
O
R1
O
R1
R3
R4
R4
H
H
R3
Results and Discussion
Initially, diphenylphosphinic acid 1a and diphenylacetylene 2a were chosen as the model substrates
and CsF as the base under irradiation of 6 W blue LEDs in the presence of Acr+-MesClO4 (3 mol%)
-
and [Co(dmgH)2]PyCl (8 mol%) (Table 1). To our delight, this reaction indeed proceeded, delivering
the desired product 3a in 46% NMR yield (Table 1, entry 1). The structure of 3a was unambiguously
confirmed by X-ray single-crystal diffraction analysis.8 A variety of bases were evaluated, it’s found
that CsF was still the best choice for this transformation (Table 1, entries 1–3). The mixture of
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chloroform and water (V/V, 4:1) can improve the yield of 3a to 52% (Table 1, entry 4). By screening
photo-catalysts and Co(III) catalysts, it is found that other Co(III) catalysts, such as Co(dmgH)2(4-
NMe2Py)Cl, Co(dmgH)2(4-CO2MePy)Cl, and [Co(dmgH)2Py2]PF6 are less effective (Table 1, entries 5-
7), and other photocatalysts, such as Ru(bpz)3(PF6)2 and fac-Ir(ppy)3 can not tigger the reaction (Table
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−
1, entries 8-9). DiRocco9 and Nicewicz10 found that Acr+-MesClO4 can undergo demethylation and is
prone to nucleophilic attack, which can lead to lose the photocatalytic activity. To our delight, when the
−
reaction was carried out for 24 h, extra Acr+-MesClO4 (3 mol%) was added to the reaction mixture and
continued to be stirred until 48 h, the product 3a can improve to 72% isolated yield (Table 1, entry 10).
Control experiments indicated that without the photocatalyst, base or visible light irradiation, the
reaction did not occur, indicating that visible light, base and photocatalyst were essential for this
reaction. Moreover, the addition of the cobalt catalyst [Co(dmgH)2]PyCl can improve the reaction
efficiency (see Supporting Information).
Table 1. Optimization of reaction conditiona
entry
photocatalyst
solvent
base
Co(III) catalyst
yieldb
(%)
-
-
-
-
1
2
3
4
Acr+-Mes ClO4
Acr+-Mes ClO4
Acr+-Mes ClO4
Acr+-Mes ClO4
CHCl3
CsF
[Co(dmgH)2]PyCl
[Co(dmgH)2]PyCl
[Co(dmgH)2]PyCl
[Co(dmgH)2]PyCl
46
CHCl3
DMAP
Cs2CO3
CsF
Trace
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CHCl3
CHCl3/H2O（4:1）
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29
32
-
-
5
6
Acr+-Mes ClO4
Acr+-Mes ClO4
CsF
CsF
Co(dmgH)2(4-NMe2Py)Cl
Co(dmgH)2(4-CO2MePy)Cl
CHCl3/H2O (4:1）
CHCl3/H2O (4:1）
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Acr+-Mes ClO4
Ru(bpz)3(PF6)2
fac-Ir(ppy)3
CsF
[Co(dmgH)2Py2]PF6
[Co(dmgH)2]PyCl
[Co(dmgH)2]PyCl
[Co(dmgH)2]PyCl
CHCl3/H2O (4:1）
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CsF
CsF
CsF
CHCl3/H2O (4:1）
CHCl3/H2O (4:1）
CHCl3/H2O (4:1）
Trace
N.R.
72
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10c, d
Acr+-Mes ClO4
a1a (0.2 mmol), 2a (0.4 mmol, 2.0 equiv.), photocatalyst (0.006 mmol, 3 mol%), base (0.3 mmol, 1.5 equiv.), Co(III)
catalyst (0.016 mmol, 8 mol%), 2.0 mL of solvent, 6 W blue LEDs, 24 h. determined by 31P NMR analysis using
b
trioctylphosphine oxide as an internal standard. cAcr+-MesClO4 (5.0 mg, 0.012 mmol, 6 mol%) was added portionwise
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d
(3 mol% of PC was added first, after 24 h another 3 mol % of PC was added), 48 h. isolated yield based on 1a in
parenthesis.
With the optimized reaction condition being established, the scope of arylphosphinic acids was then
investigated. As highlighted in Table 2, substrates bearing either electron-donating groups (i.e., methyl-,
t-Bu-) or electron-withdrawing group (i.e., fluoro-, CF3-) on the benzene ring, either ortho-, meta- or
para-substituted group, were found to be suitable for the reaction, delivering the corresponding products
in moderate yields (45%-68%, 3b-3f). It is worth noting that when 3-trifluoromethyl substituted
phosphinic acid was employed, two products (3f and 3f’) with ortho- and para-cyclization patterns can
be isolated in 68% total yield. However, when heteroaryl-substituted phosphinic acids (e g., thiophene-
substituted) were employed, unfortunately, the reaction did not occur. Encouraged by these results, to
test the generality of the cascade reaction, we turned our attention to investigate whether a series of
arylphosphonic acid monoesters could be acted as suitable candidates. As shown in Table 2, a series of
arylphosphonic acid monoesters, either electron-donating groups (e. g., CH3, OCH3, t-Bu) or electron-
withdrawing groups (e. g., F, CF3 and acetyl), and different substituted pattern on the benzene ring, are
compatible in the reaction, furnishing corresponding products 3g-3o in moderate to high yields (Table 2,
31-83% yields). It is found that the electronic property of substituents on the benzene ring has some
influence on the reaction efficiency, for example, 4-trifluoromethyl substituted substrate can give the
best result (3m, 83% yield). Moreover, when 3-trifluoromethyl substituted substrate was adopted, two
products (3o and 3o’) with ortho- and para-cyclization can be isolated in 62% total yield.
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Table 2. Substrate Scope of Arylphosphinic acids or Arylphosphonic Acid Monoestersa,b
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aReaction condition from Table 1, entry 10, 0.2 mmol scale. b Isolated yield based on 1.
Subsequently, we continued to evaluate the alkyne scope of the cascade reaction between
diphenylphosphinic acid 1a and a variety of alkynes 2. As summarized in Table 3, various symmetric
biaryl alkynes 2 were found to be compatible for the reactions and gave the desired products 3p-3v in
25-71% yields. The electronic property of substituents on the benzene ring (e. g., -F, -Cl, -Me and -t-Bu)
had no obvious influence on the reaction efficiency, and the corresponding products 3p-3u were
provided in moderate isolated yields (Table 3, 57-71% yields). Notably, the bromo-substituted substrate
tolerated well in this reaction and gave the bromo-containing product 3v, albeit in low yield (Table 3,
25% yield), which is usually incompatible in transition-metal-catalyzed reactions. As for unsymmetric
alkynes, when the disubstituents on the phenyl rings of the diarylacetylenes were −CF3 and –CH3, −F
and −CH3, respectively, the desired products 3w and 3w′, 3x and 3x’ were isolated as the mixtures of
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regio-isomers in 47-75% yields, the pure regio-isomers can be isolated further by HPLC, and their
major isomers 3w and 3x were unambiguously confirmed by X-ray single-crystal diffraction analysis.8
The observation of regioselectivity could be due to the distinctly biased electronic property on the
alkynes. However, alkyl substituted alkynes, such as phenylacetylene, (2-phenylethynyl) trimethyl
silane, phenyl prop-1-yne, and heterocycle-stituted alkynes, for example thiophene-substituted alkyne,
are not active in the cascade reaction.
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Table 3. Substrate Scope of Alkynes a,b
a Reaction condition from Table 1, entry 10, 0.2 mmol scale. b Isolated yield based on 1a.
In order to demonstrate the potential synthetic application, a gram-scale reaction of 1a with 2a was
performed under standard condition, the desired product 3a was achieved in 46 % yield (0.90 g). To
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gain further insight into the mechanism, when radical scavengers, such as TEMPO or BHT, were
introduced to the model reaction of substrates 1a and 2a under standard condition, reaction efficiencies
were partially inhibited, the desired compound 3a was isolated in 15 % and 14% yield, respectively,
without the observation of the products of phosphinyoxy radical being captured (Scheme 2).
The Luminescence quenching experiments showed that both 1a with CsF, and diphenylacetylene 2a
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*
−
could quench the excited photocatalyst Acr+-MesClO4 (see Supporting Information). A cyclic
voltammogram indicated the oxidation potential of 1a in the presence of CsF is 1.67 V vs SCE, which
indicated that phosphinate of 1a could be oxidized to phosphinyloxy radical B through single-electron
*
−
transfer (SET) by the excited photocatalyst Acr+-Mes ClO 4 (E1/2red [Acr•-Mes•+/Acr•-Mes] = +2.06 V
vs. SCE). Moreover, the pathway that the acridine excited species can oxidize diphenylacetylene (E1/2red
= +1.86 V vs. SCE) to an alkyne radical cation via a SET process is also possible.
Scheme 2. Gram-scale reaction and experiments for the mechanistic study
On the basis of above observations (see Supporting Information) and some related literatures,7i-j, 11
we proposed plausible mechanism for the phosphinyloxy radical-mediated radical addition/cyclization
cascade reaction (Figure 2). In situ-generated anionic intermediate A is initially oxidized to the key
*
−
phosphinyloxy radical B by the photoexcited state photocatalyst Acr+-MesClO4 via a SET process
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(Path A), subsequent radical addition to alkyne and cyclization results in an aryl radical species and
further oxidation by cobalt catalyst leads to the desired product 3. The latter step may proceed through
hydrogen atom abstraction (HAT) or electron/proton transfer sequence. The cobalt catalyst would act as
the proton or electron reservoir, leading to hydrogen gas release. 7a, 7b, 7d, 11 However, the reduction of Co
III-H to Co II-H, following by protonation to release H2 or the homolytic cleavage involving two Co III-H
to evolve hydrogen gas can not be ruled out. 11, 12 On the other hand, the pathway that diphenylacetylene
(E1/2red = +1.86 V vs. SCE) can be oxidized to an alkyne radical cation by the photoexcited state Acr+-
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MesClO4 (E1/2red [Acr•-Mes•+/Acr•-Mes] = +2.06 V vs. SCE) through a SET process (Path B) is also
possible.13
Figure 2. Proposed Mechanism.
In conclusion, the first photoredox/cobalt-catalyzed phosphinyloxy radical addition/cyclization
cascade for the synthesis of phosphaisocoumarins with high atom economy under ambient
temperature was developed. This method has advantages of mild condition, with no use of any
sacrificial oxidant as well as wide substrate scopes, which will inspire the application of
phosphinyloxy radical mediated synthetic transformations by visible light irradiation for the
synthesis of structurally diversity phosphorus heterocycles.
Experimental Section
Unless otherwise noted, materials were purchased from commercial suppliers and used without
further purification. The solvents used were purified by distillation over the drying agents. All of the
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reactions were monitored by analytical thin layer chromatography (TLC) on silica gel plates using UV
light as visualizing agent (if applicable). Flash column chromatography was performed using 200-300
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mesh silica gel. H NMR spectra were recorded on 400/600 MHz spectrophotometers. Chemical shifts
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are reported in delta (δ (ppm)) units in parts per million (ppm) relative to the singlet (0 ppm) for
tetramethylsilane (TMS). Data are reported as follows: chemical shift, multiplicity (s = singlet, d =
doublet, t = triplet, q = quartet, dd = doublet of doublets, m = multiplet), coupling constants (Hz) and
integration. 13C{1H}NMR spectra were recorded on Varian Mercury 400 (100 MHz) with complete
proton decoupling spectrophotometers (CDCl3: 77.0 ppm). HRMS was recorded on Bruker
ultrafleXtreme MALDITOF/TOF mass spectrometer. All of the reactions were carried out using a
schlenk borosilicate reaction tube (10 mL) flask without special photochemical equipment. There is 5.0
cm distance between the reactor and LEDs. The cobalt complexes Co(dmgH)2(4-NMe2Py)Cl,
Co(dmgH)2(4-CO2MePy)Cl, Co(dmgH)2(4-CONEt2Py)Cl and [Co(dmgH)2Py2]PF6 were prepared
according to the reported procedure.[14]
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All alkynes 2 are known compounds, which were synthesized according to the reported method.[15] 1-
Methyl-4-[(p-tolyl) ethynyl] benzene (2r)(known compound).[15] A white solid; yield 670 mg (65%); mp
1
137 - 139 oC. H NMR (400 MHz, CDCl3) δ (ppm) = 7.41 (d, J = 7.7 Hz, 4H), 7.14 (d, J = 7.6 Hz, 4H),
2.35 (s, 6H). 13C{1H} NMR (100 MHz, CDCl3) δ (ppm) = 138.1, 131.4, 129.1, 120.3, 88.8, 21.6.
All diarylphosphinic acids 1 are known compounds, which were synthesized according to the reported
method [16]. Bis (4-tert-butyl) phenylphosphinic acid (1d)(known compound).[16] A white solid; yield 908
mg (55%); mp 200 - 202 oC. 1H NMR (400 MHz, CDCl3) δ (ppm) = 8.58 (s, 1H), 7.67 (dd, J = 12.2, 8.1
Hz, 4H), 7.38 (dd, J = 8.4, 3.1 Hz, 4H), 1.29 (s, 18 H). 13C{1H} NMR (100 MHz, CDCl3) δ (ppm) =
155.0 (d, JC-P = 2.5 Hz), 131.1 (d, JC-P = 10.9 Hz), 129.8 (d, JC-P = 141.6 Hz), 125.2 (d, JC-P = 13.0 Hz),
34.9, 31.1.
Arylphosphonic mono-ester were synthesized according to the reported procedure [5c]. Except for 1g, 1i,
1l, 1m and 1o are new compounds, other arylphosphonic mono-esters are kown compounds.
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(4-Methoxy phenyl) phosphonic acid monoethyl ester (1j)(known compound).[5c] A yellow oil; yield
71.3 mg (66 %). 1H NMR (400 MHz, CDCl3) δ (ppm) = 11.56 (s, 1H), 7.76-7.63 (m, 2H), 6.99-6.78 (m,
6
7
13
2H), 4.14-3.93 (m, 2H), 3.82 (s, 3H), 1.27 (q, 3H). C{1H} NMR (100 MHz, CDCl3) δ (ppm) = 162.6
8
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(d, JC-P =3.3 Hz), 133.2 (d, JC-P =11.5 Hz), 120.0 (d, JC-P = 199.7 Hz), 113.8 (d, JC-P = 16.2 Hz), 61.7 (d,
JC-P = 5.7 Hz), 55.2, 16.1 (d, JC-P = 6.9 Hz).
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(4-Methyl phenyl) phosphonic acid monoethyl ester (1g). A yellow oil; yield 750 mg (75%). H NMR
(400 MHz, CDCl3) δ (ppm) = 11.40 (s, 1H), 7.68 (dd, J = 13.5, 7.7 Hz, 2H), 7.20 (dd, J = 8.0, 3.9 Hz,
2H), 4.06-3.99 (m, 2H), 2.35 (s, 3H), 1.25 (t, J = 7.1 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3) δ (ppm)
= 142.5 (d, JC-P = 3.2 Hz), 131.2 (d, JC-P = 10.6 Hz), 128.9 (d, JC-P = 15.6 Hz), 125.4 (d, JC-P = 194.7
Hz), 61.7 (d, JC-P = 5.6 Hz), 21.4, 16.1 (d, JC-P = 6.8 Hz). 31P NMR (162 MHz, CDCl3): δ = 20.2. HRMS
(ESI-TOF) m/z: [M + H]+ calcd for C9H14O3P: 201.0675; found: 201.0645.
(4-tert-Butyl phenyl) phosphonic acid monoethyl ester (1i). A yellow oil; yield 872 mg (72%). 1H NMR
(400 MHz, CDCl3) δ (ppm) = 11.54 (s, 1H), 7.75 (s, 2H), 7.48-7.44 (m, 2H), 4.14-4.04 (m, 2H), 1.33-
1.23 (m, 12H). C{1H} NMR (100 MHz, CDCl3) δ (ppm) = 155.6, 131.2 (d, JC-P =10.6 Hz), 125.5 (d,
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JC-P = 195.0 Hz), 125.3 (d, JC-P = 15.5 Hz), 61.7 (d, JC-P = 5.3 Hz), 34.9, 31.0, 16.1 (d, JC-P = 6.9 Hz).
31P NMR (162 MHz, CDCl3): δ = 20.9. HRMS (ESI-TOF) m/z: [M + H]+ calcd for C12H20O3P:
243.1145; found: 243.1115.
1
(3,5-Dimethylphenyl) phosphonic acid monoethyl ester (1l). A yellow oil; yield 674 mg (63%). H
NMR (400 MHz, CDCl3) δ (ppm) = 12.19 (s, 1H), 7.42 (d, J = 14.0 Hz, 2H), 7.14 (s, 1H), 4.10-4.03 (m,
2H), 2.32 (s, 6H), 1.30 (t, J = 7.1 Hz, 3H). C{1H} NMR (100 MHz, CDCl3) δ (ppm) = 137.9 (d, JC-P
13
=16.0 Hz), 133.9 (d, JC-P =3.4 Hz), 128.2 (d, JC-P = 191.1 Hz), 128.8 (d, JC-P = 10.0 Hz), 61.8 (d, JC-P
=
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5.8 Hz), 21.1, 16.1 (d, JC-P = 6.7 Hz). P NMR (162 MHz, CDCl3): δ = 21.1. HRMS (ESI-TOF) m/z:
[M + H]+ calcd for C10H16O3P: 215.0832; found: 215.0802.
[4-(Trifluoromethyl)phenyl]phosphonic acid monoethyl ester (1m). A yellow oil; yield 851 mg (67 %).
1H NMR (400 MHz, CDCl3) δ (ppm) = 10.75 (s, 1H), 7.91 (dd, J = 13.4, 7.9 Hz, 2H), 7.68 (dd, J = 8.3,
3.5 Hz, 2H), 4.13-4.04 (m, 2H), 1.29 (t, J = 7.1 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3) δ (ppm) =
133.9-133.6 (m), 131.8 (d, JC-P = 10.5 Hz), 125.3 -125.1 (m), 123.5 (d, JC-F = 271.3 Hz), 62.5 (d, JC-P
5.9 Hz) , 16.1 (d, JC-P = 6.7 Hz). 31P NMR (162 MHz, CDCl3): δ = 17.03. HRMS (ESI-TOF) m/z: [M +
=
H]+ calcd for C9H11F3O3P: 255.0392; found: 255.0388.
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[3-(Trifluoromethyl)phenyl]phosphonic acid monoethyl ester (1o). A yellow oil; yield 991 mg (78 %).
1H NMR (400 MHz, CDCl3) δ (ppm) = 11.84 (s, 1H), 8.06 (d, J = 14.0 Hz, 1H), 7.98 (dd, J = 13.4, 7.7
Hz, 1H), 7.78 (d, J = 7.8 Hz, 1H), 7.57 (td, J = 7.8, 3.8 Hz, 1H), 4.13-4.05 (m, 2H), 1.30 (t, J = 7.1 Hz,
3H). 13C{1H} NMR (100 MHz, CDCl3) δ (ppm) = 134.6 (d, JC-P = 10.0 Hz), 131.1-130.6 (m), 130.2 (d,
JC-P = 194.5 Hz), 128.9, 128.2-128.1 (m), 123.6 (d, JC-F = 271.4 Hz), 62.5 (d, JC-P = 5.9 Hz), 16.1 (d, JC-
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= 6.7 Hz). 31P NMR (162 MHz, CDCl3): δ = 16.70. HRMS (ESI-TOF) m/z: [M + H]+ calcd for
P
C9H11F3O3P: 255.0392; found: 255.0366.
General procedure for the synthesis of 3a-3x.
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1a (0.2 mmol), 2a (0.4 mmol), Acr+-MesClO4 (2.5 mg, 0.006 mmol), [Co(dmgH)2]PyCl (6.5 mg,
0.016 mmol) and CsF (46 mg, 0.3 mmol) were dissolved in CHCl3/H2O (2 mL, V/V = 4:1). Then, the
resulting mixture was degassed via ‘freeze-pump-thaw’ procedure (3 times) under argon atmosphere.
After that, the solution was stirred at a distance of ~5 cm from a 6 W blue LEDs (450-460 nm) at
-
ambient temperature for 24 h. Then another Acr+-MesClO4 (2.5 mg, 0.006 mmol) was added and
stirred at under irradiation of 6 W blue LEDs until the reaction was completed, as monitored by TLC
analysis. The crude product was purified by flash chromatography on silica gel (petroleum ether/ethyl
acetate 3:1) directly to give the desired product 3.
[5a]
1,3,4-Triphenyl-1H-2,1-benzoxaphosphorin-1-oxide (3a)(known compound).
A light yellow solid;
yield 56.80 mg (72%); mp 143 - 145 oC. IR (in KBr): 3132, 1489, 1245, 1122, 945, 731 cm-1. 1H NMR
(400 MHz, CDCl3) δ (ppm) = 7.97 - 7.91 (m, 2H), 7.62 - 7.56 (m, 2H), 7.54 - 7.49 (m, 2H), 7.43 (t, J =
7.8 Hz, 1H), 7.40 - 7.30 (m, 4H), 7.30 - 7.25 (m, 2H), 7.25 - 7.20 (m, 2H), 7.17 - 7.10 (m, 2H), 7.09 -
7.04 (m, 2H). 13C{1H} NMR (100 MHz, CDCl3) δ (ppm) = 146.8 (d, JC-P = 11.0 Hz), 138.6 (d, JC-P
=
5.3 Hz), 136.0, 134.6 (d, JC-P = 5.1 Hz), 132.9 (d, JC-P = 2.9 Hz), 132.4 (d, JC-P = 2.5 Hz), 132.3 (d, JC-P
= 11.0 Hz), 131.5, 130.2 (d, JC-P = 12.3 Hz), 129.9 (d, JC-P = 144.3 Hz) , 129.1, 128.9, 128.6, 128.4 (d,
J
C-P = 3.6 Hz), 127.8, 127.6, 127.5, 126.7 (d, JC-P = 9.5 Hz), 123.1 (d, JC-P =128.8 Hz), 119.1 (d, JC-P =
11.0 Hz). 31P NMR (162 MHz, CDCl3 ): δ = 24.6. HRMS (ESI-TOF) m/z: [M + H]+ calcd for C26H20O2P:
395.1195; found: 395.1182.
6-Methyl-1-(4-methylphenyl)-3,4-diphenyl-1H-2,1-benzoxa-phosphorin 1-oxide (3b). A yellow solid;
1
yield 41.40 mg (49%); mp 200 - 202 oC. IR (in KBr): 3138, 2975, 1601, 1480, 1236, 1121 cm-1. H
NMR (400 MHz, CDCl3) δ (ppm) = 7.88 - 7.78 (m, 2H), 7.44 - 7.31 (m, 7H), 7.28 - 7.25 (m, 2H) , 7.23 -
7.20 (m, 2H), 7.15 - 7.05 (m, 3H), 6.95 - 6.91 (dd, J = 8.3, 5.1 Hz, 1H), 2.44 (s, 3H), 2.31 (s, 3H).
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13C{1H} NMR (100 MHz, CDCl3) δ (ppm) = 146.2 (d, JC-P = 11.0 Hz), 143.6 (d, JC-P = 2.9 Hz), 137.8
(d, JC-P = 22.9 Hz), 136.3, 136.0 (d, JC-P = 5.3 Hz), 134.8 (d, JC-P = 5.1 Hz), 133.3 (d, JC-P = 11.0 Hz),
132.3 (d, JC-P = 11.5 Hz), 131.6, 130.4 (d, JC-P = 12.2 Hz), 130.0 (JC-P= 101.2 Hz), 129.3 (d, JC-P = 3.8
Hz), 129.0, 128.8, 128.2, 127.7, 127.5, 126.8 (d, JC-P = 10.0 Hz), 123.2 (d, JC-P = 128.2 Hz), 119.0 (d,
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JC-P = 10.9 Hz), 21.7 (d, J = 1.4 Hz), 21.1. P NMR (162 MHz, CDCl3 ): δ = 25.3. HRMS (ESI-TOF)
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m/z: [M + H]+ calcd for C28H24O2P: 423.1508; found: 423.1504.
8-Methyl-1-(2-methylphenyl)-3,4-diphenyl-1H-2,1-benzoxa-phosphorin 1-oxide (3c)(known compound).
A white solid; yield 42.24 mg (50%); mp 125 - 127 oC. IR (in KBr): 3131, 2926, 1622, 1488, 1245,
[5a]
1090 cm-1. 1H NMR (400 MHz, CDCl3) δ (ppm) = 7.76 (dd, J = 15.6, 7.7 Hz, 1H), 7.64 - 7.61 (m, 1H),
7.42 - 7.23 (m, 3H), 7.20 - 7.09 (m, 6H), 7.07 - 7.03 (m, 4H), 6.86 (d, J = 7.6 Hz, 2H), 2.23 (s, 3H), 1.66
(s, 3H). 13C{1H} NMR (100 MHz, CDCl3) δ (ppm) = 146.8 (d, JC-P = 9.9 Hz), 142.5 (d, JC-P =8.4 Hz),
138.3 (d, JC-P = 2 Hz), 137.4 (d, JC-P = 5.5 Hz), 137.1 (d, JC-P =2.7 Hz), 136.9, 135.1 (d, JC-P = 3.5 Hz),
133.4 (d, JC-P = 14.8 Hz), 132.9 (d, JC-P = 2.8 Hz), 131.5 (d, JC-P = 12.0 Hz), 130.8, 129.8 (d, JC-P
=
186.1 Hz), 128.9, 128.3, 128.1 (d, JC-P = 3.7 Hz), 128.0, 127.5, 127.2, 126.5 (d, JC-P = 108.2 Hz), 125.0
(d, JC-P = 15 Hz), 124.5, 123.0 (d, JC-P = 12.8 Hz), 22.9 (d, JC-P = 1.5 Hz), 20.8 (d, JC-P = 4.2 Hz). 31P
NMR (162 MHz, CDCl3 ): δ = 31.0. HRMS (ESI-TOF) m/z: [M + H]+ calcd for C28H24O2P: 423.1508;
found: 423.1516.
6-tert-Butyl-1-(4-tertiary butylphenyl)-3,4-diphenyl-1H-2,1-benzoxa-phosphorin 1-oxide (3d). A white
solid; yield 55.72 mg (55%); mp 104 - 105 oC. IR (in KBr): 3132, 2968, 1633, 1400, 1233, 1090 cm-1.
1H NMR (400 MHz, CDCl3) δ (ppm) 7.84 (dd, J = 12.9, 8.0 Hz, 2H), 7.65 (d, J = 14.8 Hz, 1H), 7.57-
7.45 (m, 3H), 7.37 (d, J = 6.6 Hz, 4H), 7.22 (d, J = 7.7 Hz, 2H), 7.16 -7.05 (m, 4H), 6.97 (dd, J = 8.6,
5.4 Hz,1H), 1.35 (s, 9H), 1.26 (s, 9H). 13C{1H} NMR (100 MHz, CDCl3) δ (ppm) = 156.4 (d, JC-P = 2.9
Hz), 151.0 (d, JC-P = 13.1 Hz), 146.4 (d, JC-P = 11.0 Hz), 136.4, 136.3 (d, JC-P = 5.6 Hz), 134.9 (d, JC-P
=
5.1 Hz), 131.9 (d, JC-P = 11.4 Hz), 131.6, 129.9 (d, JC-P = 2.6 Hz), 129.3 (d, JC-P = 103.2 Hz), 129.0,
128.9, 128.3,128.0, 127.6 (d, JC-P = 22.3 Hz), 127.5, 126.7 (d, JC-P = 2.7 Hz), 125.6 (d, JC-P = 13.7 Hz),
122.8 (d, JC-P = 128.0 Hz), 118.9 (d, JC-P = 10.7 Hz), 35.2, 34.8, 31.1 (d, JC-P = 6.2 Hz). 31P NMR (162
MHz, CDCl3 ): δ = 25.9. HRMS (ESI-TOF) m/z: [M + H]+ calcd for C34H36O2P: 507.2447; found:
507.2442.
6-Fluoro-1-(4-fluoro phenyl)-3,4-diphenyl-1H-2,1-benzoxa-phosphorin 1-oxide (3e). A white solid;
yield 38.73 mg (45%); mp 175 - 177 oC. IR (in KBr): 3133, 2363, 1639, 1400, 1240, 1093, 949, 761 cm-
1. 1H NMR (400 MHz, CDCl3) δ (ppm) = 8.02 - 7.90 (m, 2H), 7.41 - 7.35 (m, 3H), 7.29 - 7.18 (m, 7H),
7.18 - 7.03 (m, 5H). 13C{1H} NMR (100 MHz, CDCl3) δ (ppm) = 165.9 (dd, JC-F = 253.7 Hz , JC-P = 3.5
Hz ), 161.4 (dd, JC-F = 251.1 Hz , JC-P = 19.8 Hz), 146.3 -146.2 (m), 135.1 (d, JC-P = 21.7 Hz), 135.13,
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135.10, 134.9 - 134.8 (m), 134.3 (d, JC-P = 5.1 Hz), 131.4, 129.6 (dd, JC-F = 11.2 Hz , JC-P = 7.3 Hz ),
129.01, 128.96, 128.6, 128.0, 127.6, 125.8-125.9 (m), 124.5 (dd, JC-F = 19.2 Hz , JC-P = 6.1 Hz ), 120.0
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(dd, JC-F = 21.5 Hz , JC-P = 2.7 Hz ), 118.6 (d, JC-P = 11.0 Hz), 116.6 -116.0 (m). P NMR (162 MHz,
CDCl3 ): δ = 21.5. HRMS (ESI-TOF) m/z: [M + H]+ calcd for C26H18F2O2P: 431.1007; found: 431.1008.
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7-Trifluoromethyl -1-(3-trifluoromethyl phenyl)-3,4-diphenyl-1H-2,1-benzoxa- phosphorin 1-oxide (3f).
A colorless oil; yield 33.94 mg (32 %); IR (in KBr): 3131, 2361, 1637, 1401, 1248, 1131, 958, 752.cm-1.
1H NMR (400 MHz, CDCl3) δ (ppm) = 8.24 (d, J = 13.5 Hz, 1H), 8.12 (dd, J = 13.0, 7.6 Hz, 1H), 7.91
(d, J = 8.0 Hz, 1H), 7.73 - 7.64 (m, 2H), 7.59 (d, J = 7.7 Hz, 1H), 7.41 (t, J = 3.4 Hz, 3H), 7.34 (d, J =
4.1 Hz, 1H), 7.31 - 7.26 (m, 2H), 7.24 - 7.21 (m, 2H), 7.18 (d, J = 6.4 Hz, 1H), 7.16 - 7.09 (m, 2H).
13C{1H} NMR (100 MHz, CDCl3) δ (ppm) = 148.2 (d, JC-P =11.1 Hz ), 139.6 (d, JC-P = 5.8 Hz), 135.7 (d,
J
C-P = 10.8 Hz), 134.7, 133.9 (d, JC-P = 4.2 Hz), 131.6 (d, JC-P = 6.0 Hz), 131.4 130.9 (d, JC-P = 12.8 Hz ),
129.8, 129.5, 129.4, 129.3, 129.1, 128.5, 127.8, 127.2 (d, JC-F = 114.1 Hz), 125.9 (d, JC-P = 128.7 Hz),
124.5, 124.3 - 124.2 (m), 124.1-124.0 (m), 123.8 - 123.6 (m), 122.1 (d, JC-P = 2.3 Hz), 118.8 (d, JC-P
=
11.0 Hz). 31P NMR (162 MHz, CDCl3 ): δ = 20.8. HRMS (ESI-TOF) m/z: [M + H]+ calcd for
C28H18F6O2P: 531.0943; found: 531.0916.
5-Trifluoromethyl -1-(3-trifluoromethyl phenyl)-3,4-diphenyl-1H-2,1-benzoxa-phosphorin 1-oxide (3f’).
A white solid; yield 38.19 mg (36 %); mp 211 - 213 oC. IR (in KBr): 3131, 2361, 1635, 1400, 1249,
1130, 968, 732.cm-1. 1H NMR (400 MHz, CDCl3) δ (ppm) = 8.16 (dd, J = 13.6, 8.8 Hz, 2H), 7.88 (d, J =
7.8 Hz, 1H), 7.72 - 7.65 (m, 2H), 7.60 (t, J = 8.1 Hz, 1H), 7.42 (t, J = 3.4 Hz, 3H), 7.36 (dd, J = 8.3, 3.4
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Hz, 1H), 7.32 - 7.27 (m, 2H), 7.18 (d, J = 7.6 Hz, 3H), 7.12 (d, J = 7.3 Hz, 2H). C{1H} NMR (100
MHz, CDCl3) δ (ppm) = 146.7 (d, JC-P = 10.7 Hz ), 141.3 (d, JC-P = 3.2 Hz), 135.8 (d, JC-P = 11.1 Hz),
135.7, 133.6 (d, JC-P = 4.7 Hz), 132.4 (d, JC-P = 2.1 Hz), 131.8 (d, JC-P = 8.8 Hz), 131.5, 131.4 (d, JC-P
=
8.3 Hz ), 130.9 (d, JC-P = 32.7 Hz ), 130.7 (d, JC-P = 32.7 Hz ), 129.7-129.6 (m), 129.3, 129.0, 128.9,
128.8, 128.7, 128.3, 127.7, 126.4-126.2 (m), 123.6 (dd, JC-F = 279.4 Hz , JC-P = 2.4 Hz ), 123.2 (dd, JC-F
= 273.2 Hz , JC-P = 4.1 Hz ), 120.9 (d, JC-P = 124.0 Hz), 119.5 (d, JC-P = 11.5 Hz). 31P NMR (162 MHz,
CDCl3 ): δ = 19.1. HRMS (ESI-TOF) m/z: [M + H]+ calcd for C28H18F6O2P: 531.0943; found: 531.0927.
3,4-Diphenyl-1-ethoxy-6-methylbenz[c-1,2]oxaphosphinine 1-oxide (3g). A yellow oil; yield 41.40 mg
(55%); IR (in KBr): 3131, 1633, 1401, 1161, 1040, 957, 757. cm-1. 1H NMR (400 MHz, CDCl3) δ (ppm)
= 7.82-7.72 (m, 1H), 7.40 - 7.30 (m, 3H), 7.29 (s, 1H),7.24 - 7.10 (m, 7H), 6.85 (dd, J = 8.2, 6.6 Hz,
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1H), 4.33 - 4.16 (m, 2H), 2.42 (s, 3H), 1.32 (t, J = 7.1 Hz, 3H). C{1H} NMR (100 MHz, CDCl3) δ
(ppm)= 147.0 (d, JC-P = 9.0 Hz), 137.9 (d, JC-P = 15.3 Hz), 137.6 (d, JC-P = 6.8 Hz), 136.2, 134.6 (d, JC-P
= 5.7 Hz), 133.7 (d, JC-P = 2.4 Hz), 131.5, 129.6 (d, JC-P = 9.1 Hz), 128.9, 128.8, 128.4, 127.8, 127.6,
127.2 (d, JC-P = 12.4 Hz), 120.7 (d, JC-P = 170.0 Hz), 119.8 (d, JC-P = 14 Hz), 62.9 (d, JC-P = 6.7 Hz),
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21.1, 16.5 (d, J = 6.1 Hz). P NMR (162 MHz, CDCl3): δ = 11.1. HRMS (ESI-TOF) m/z: [M + H]+
calcd for C23H22O3P: 377.1301; found: 377.1294.
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[5a]
3,4-Diphenyl-1-ethoxy-6-acetylbenz[c-1,2]oxaphosphinine 1-oxide (3h)(known compound).
A
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yellow oil; yield 43.67 mg (54%); IR (in KBr): 3132, 2926, 2362, 1686, 1401, 1290, 1180, 1026, 954,
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756 cm-1. H NMR (400 MHz, CDCl3) δ (ppm) = 8.50 (dd, J = 15.5, 1.9 Hz, 1H), 8.05 (d, J = 8.5 Hz,
1H), 7.39 (s, 1H), 7.38 (d, J = 4.0 Hz, 2H), 7.30 - 7.23 (m, 4H), 7.24 - 7.14 (m, 3H), 7.07 (dd, J = 8.5,
6.1 Hz, 1H), 4.38 - 4.24 (m, 2H), 2.65 (s, 3H), 1.35 (t, J = 7.1 Hz, 3H). 13C{1H} NMR (100 MHz,
CDCl3) δ (ppm) = 196.2, 149.9 (d, JC-P = 10.8 Hz), 144.2 (d, JC-P = 7.0 Hz), 135.6, 135.5 (d, JC-P = 1.6
Hz), 134.0 (d, JC-P = 5.5 Hz), 132.1, 131.4, 129.9 (d, JC-P = 9.8 Hz), 129.1, 128.9, 128.2, 127.8, 127.4 (d,
JC-P = 10.2 Hz), 127.1, 121.1 (d, JC-P = 182.0 Hz), 119.6 (d, JC-P = 11.3 Hz), 63.4 (d, JC-P = 6.7 Hz), 26.6,
16.5 (d, JC-P = 5.9 Hz). 31P NMR (162 MHz, CDCl3 ): δ = 9.5. HRMS (ESI-TOF) m/z: [M + H]+ calcd
for C24H22O4P: 405.1250; found: 405.1245.
3,4-Diphenyl-1-ethoxy-6- tert-butylbenz[c-1,2]oxaphosphinine 1-oxide (3i). A white solid; yield 35.15
mg (42%); mp 140 - 141 oC. IR (in KBr): 3132, 2362, 1634, 1478, 1401, 1268, 1169, 1052, 951, 752
cm-1. 1H NMR (400 MHz, CDCl3) δ (ppm) = 7.96 (dd, J = 15.9, 2.2 Hz, 1H), 7.51 (dd, J = 8.3, 2.2 Hz,
1H), 7.40 - 7.30 (m, 3H), 7.28 - 7.08 (m, 7H), 6.90 (dd, J = 8.5, 6.8 Hz, 1H), 4.28 - 4.23 (m, 2H), 1.33
(d, J = 10.4 Hz, 12H). 13C{1H} NMR (100 MHz, CDCl3) δ (ppm) = 151.1 (d, JC-P = 14.6 Hz), 147.1 (d,
J
C-P = 10.8 Hz), 137.6 (d, JC-P = 6.9 Hz), 136.2 (d, JC-P = 1.5 Hz), 134.5 (d, JC-P = 5.7 Hz), 131.4, 130.2
(d, JC-P = 3.1 Hz), 128.8, 128.7, 128.4, 127.8, 127.6, 127.0 (d, JC-P = 12.9 Hz), 125.8 (d, JC-P = 2.4 Hz),
120.6 (d, JC-P = 152.6 Hz), 119.7 (d, JC-P = 11.7 Hz), 62.8 (d, JC-P = 7.0 Hz), 34.9, 31.1, 16.4 (d, JC-P
=
6.1 Hz). 31P NMR (162 MHz, CDCl3 ): δ = 11.4. HRMS (ESI-TOF) m/z: [M + H]+ calcd for C26H28O3P:
419.1771; found: 419.1771.
3,4-Diphenyl-1-ethoxy-6- methoxybenz[c-1,2]oxaphosphinine 1-oxide (3j) (known compound). [5b]
yellow solid; yield 24.32 mg (31%); mp 95 - 97 oC. IR (in KBr): 3131, 2361, 1631, 1401, 1236, 1150,
1063, 948, 756 cm-1. H NMR (400 MHz, CDCl3) δ (ppm) = 7.46 (d, J = 2.8 Hz, 1H), 7.42 (d, J = 2.8
A
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Hz, 1H), 7.38 -7.30 (m, 3H), 7.21 (dd, J = 8.5, 4.0 Hz, 3H), 7.17 - 7.11 (m, 3H), 7.00 (dd, J = 8.9, 2.8
Hz, 1H), 6.89 (dd, J = 9.0, 7.2 Hz, 1H), 4.32 - 4.19 (m, 2H), 3.88 (s, 3H), 1.32 (t, J = 7.1 Hz, 3H).
13C{1H} NMR (100 MHz, CDCl3) δ (ppm) = 158.8 (d, JC-P = 19.0 Hz), 145.8 (d, JC-P = 10.6 Hz), 136.3,
134.5 (d, JC-P = 5.6 Hz), 133.1 (d, JC-P = 6.2 Hz), 131.4, 129.1(d, JC-P = 14.3 Hz), 128.8, 128.7, 128.2,
128.0 (d, JC-P = 42.2 Hz), 127.6, 122.0 (d, JC-P = 179.6 Hz), 120.1 (d, JC-P = 3.0 Hz), 119.7 (d, JC-P
=
11.5 Hz), 112.5 (d, JC-P = 10.2 Hz), 63.0 (d, JC-P= 6.6 Hz), 55.7, 16.4 (d, JC-P = 6.0 Hz). 31P NMR (162
MHz, CDCl3): δ = 10.6. HRMS (ESI-TOF) m/z: [M + H]+ calcd for C23H22O4P: 393.1250; found:
393.1253.
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3,4-Diphenyl-1-ethoxy-6-fluorobenz[c-1,2]oxaphosphinine 1-oxide (3k) (known compound).[5b]
A
yellow oil; yield 26.62 mg (35%); IR (in KBr): 3132, 2362, 1634, 1477, 1401, 1083, 958, 785 cm-1. 1H
NMR (400 MHz, CDCl3) δ (ppm) = 7.66 - 7.60 (m, 1H), 7.37 - 7.35 (m, 3H), 7.25 - 7.10 (m, 8H), 6.99 -
6.94 (m, 1H), 4.36 - 4.18 (m, 2H), 1.34 (t, J = 7.1 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3) δ (ppm) =
162.6 (d, JC-P = 21.7 Hz ), 160.1 (d, JC-P = 21.7 Hz ), 147.1 (d, JC-P = 3.1 Hz), 136.5 (dd, JC-P = 5.9 Hz ,
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C-F = 2.8 Hz ), 135.8, 134.2 (d, JC-P = 5.9 Hz), 131.4, 129.8 (dd, JC-P = 14.0 Hz , JC-F = 7.3 Hz ), 129.0,
128.7, 128.6, 128.0, 127.7, 120.2 (dd, JC-F = 20.7 Hz , JC-P = 2.1 Hz), 118.2 (JC-P = 211.6 Hz), 115.8 (dd,
JC-F = 22.8 Hz , JC-P = 9.2 Hz ), 63.3 (d, JC-P = 6.3 Hz), 16.4 (d, JC-P = 5.8 Hz). 31P NMR (162 MHz,
CDCl3 ): δ = 8.7. HRMS (ESI-TOF) m/z: [M + H]+ calcd for C22H19FO3P: 381.1050; found: 381.1051.
3,4-Diphenyl-1-ethoxy-5-methyl-7-methylbenz[c-1,2]-oxaphosphinine 1-oxide (3l). A white solid; yield
49.19 mg (63%); mp 128 -130 oC. IR (in KBr): 3133, 2989, 1401, 1256, 1027, 961, 767 cm-1. 1H NMR
(400 MHz, CDCl3) δ (ppm) = 7.40 - 7.29 (m, 3H), 7.20 (dd, J = 7.0, 3.3 Hz, 3H), 7.16 - 7.09 (m, 4H),
7.04 (d, J = 4.3 Hz, 1H), 6.58 (d, J = 5.7 Hz, 1H), 4.33 - 4.14 (m, 2H), 2.73 (d, J = 1.8 Hz, 3H), 2.21 (s,
3H), 1.34 (t, J = 7.1 Hz, 3H). C{1H} NMR (100 MHz, CDCl3) δ (ppm) = 147.2 (d, JC-P = 10.4 Hz),
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142.9 (d, JC-P = 2.3 Hz), 141.1 (d, JC-P = 9.9 Hz), 141.08, 136.6, 134.6 (d, JC-P = 5.8 Hz), 131.6, 131.1,
130.9, 128.8, 128.3, 127.7, 127.5, 125.7 (d, JC-P = 12.3 Hz), 119.4 (d, JC-P = 11.5 Hz), 116.4 (d, JC-P
=
178.6 Hz), 62.6 (d, JC-P = 6.9 Hz), 21.7, 21.4, 16.4 (d, JC-P = 5.8 Hz). 31P NMR (162 MHz, CDCl3 ): δ =
10.8. HRMS (ESI-TOF) m/z: [M + H]+ calcd for C24H24O3P: 391.1458; found: 391.1463.
3,4-Diphenyl-1-ethoxy-6-trifluoromethylbenz[c-1,2]oxaphosphinine 1-oxide (3m). A yellow oil; yield
71.43 mg (83%); IR (in KBr): 3131, 1601, 1488, 1271, 1241, 1026, 955, 756 cm-1. 1H NMR (400 MHz,
CDCl3) δ (ppm) = 8.20 (dd, J = 15.3, 2.0 Hz, 1H), 7.68 (d, J = 8.5 Hz, 1H), 7.44 - 7.32 (m, 3H), 7.29 -
7.13 (m, 7H), 7.09 (dd, J = 8.5, 6.0 Hz, 1H), 4.41- 4.22 (m, 2H), 1.35 (t, J = 7.1 Hz, 3H). 13C{1H} NMR
(100 MHz, CDCl3) δ (ppm)= 149.7 (d, JC-P = 10.3 Hz), 143.4 (d, JC-P = 7.0 Hz), 135.4, 133.9 (d, JC-P
5.7 Hz), 129.7, 129.6, 129.3, 129.1 (d, JC-P = 9.8 Hz), 128.9, 128.3, 127.8, 127.6. 127.5, 126.5 - 126.6
(m), 124.8, 121.6 (d, JC-F = 182.8 Hz), 119.3 (d, JC-P = 11.4 Hz), 63.5 (d, JC-P = 6.6 Hz), 16.5 (d, JC-P
=
=
5.8 Hz). 31P NMR (162 MHz, CDCl3 ): δ = 8.5. HRMS (ESI-TOF) m/z: [M + H]+ calcd for C23H19F3O3P:
431.1018; found: 431.1019.
3,4-Diphenyl-1-ethoxybenz[c-1,2]oxaphosphinine 1-oxide (3n) (known compound). [5a] A yellow solid;
yield 34.06 mg (47%); mp 124 -126 oC. IR (in KBr): 3132, 1606, 1467, 1441, 1269, 1025, 950, 761 cm-1.
1H NMR (400 MHz, CDCl3) δ (ppm) = 7.98 - 7.92 (m, 1H), 7.50 - 7.41 (m, 2H), 7.39 - 7.31 (m, 3H),
7.30 - 7.09 (m, 7H), 7.02 - 6.93 (m, 1H), 4.39 - 4.15 (m, 2H), 1.32 (t, J = 7.1 Hz, 3H). 13C{1H} NMR
(100 MHz, CDCl3) δ (ppm) = 147.8 (d, JC-P = 10.3 Hz), 140.1 (d, JC-P = 6.8 Hz), 136.0 (d, JC-P = 1.2 Hz),
134.4 (d, JC-P = 5.5 Hz), 132.8 (d, JC-P = 2.5 Hz), 131.5, 129.3 (d, JC-P = 8.9 Hz), 128.8, 128.7, 128.5,
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127.8, 127.6, 127.5, 127.1 (d, JC-P = 12 Hz), 120.8 (d, JC-P = 180.5 Hz), 119.8 (d, JC-P = 11.8 Hz), 63.0
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(d, JC-P = 6.6 Hz), 16.4 (d, JC-P = 5.8 Hz). P NMR (162 MHz, CDCl3 ): δ = 10.6. HRMS (ESI-TOF)
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m/z: [M + H]+ calcd for C22H20O3P: 363.1145; found: 363.1146.
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3,4-Diphenyl-1-ethoxy-7-trifluoromethylbenz[c-1,2]oxaphosphinine 1-oxide (3o). A white solid; yield
29.26 mg (34%); mp 124 -127 oC. IR (in KBr): 3130, 1634, 1401, 1265, 1237, 1033, 973, 696 cm-1. 1H
NMR (600 MHz, CDCl3) δ (ppm) = 8.07 (dd, J = 14.6, 7.9 Hz, 1H), 7.67 (dd, J = 7.7, 2.4 Hz, 1H), 7.45
- 7.30 (m, 3H), 7.28 - 7.09 (m, 8H), 4.35 - 4.25 (m, 2H), 1.34 (t, J = 7.1 Hz, 3H). 13C{1H} NMR (100
MHz, CDCl3) δ (ppm) = 149.2 (d, JC-P = 10.5 Hz), 141.1 (d, JC-P = 7.0 Hz), 135.0, 134.0 (d, JC-P = 5.6
Hz), 131.3, 130.1, 130.0, 129.2, 129.0, 128.8, 128.4, 127.8, 125.0 (d, JC-F = 73.4 Hz), 124.1-123.9 (m),
123.8 -123.5 (m), 121.9, 119.3 (d, J = 11.6 Hz), 63.5 (d, JC-P = 6.6 Hz), 16.5 (d, JC-P = 5.8 Hz). 31P
NMR (162 MHz, CDCl3 ): δ = 8.3. HRMS (ESI-TOF) m/z: [M + H]+ calcd for C23H19F3O3P: 431.1018;
found: 431.1021.
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3,4-Diphenyl-1-ethoxy-5-trifluoromethylbenz[c-1,2]oxaphosphinine 1-oxide (3o’). A white solid; yield
24.09 mg (28%); mp 179 -180 oC. IR (in KBr): 3132, 1621, 1400, 1267, 1214, 1020, 971, 757 cm-1. 1H
NMR (400 MHz, CDCl3) δ (ppm) = 7.74 (dd, J = 7.8, 4.8 Hz, 1H), 7.53 (t, J = 8.0 Hz, 1H), 7.39 -7.35
(m, 3H), 7.25 -7.14 (m, 8H), 4.47- 4.33 (m, 2H), 1.38 (t, J = 7.1 Hz, 3H). 13C{1H} NMR (100 MHz,
CDCl3) δ (ppm) = 148.0 (d, JC-P = 10.3 Hz), 142.5 (d, J = 4.5 Hz), 135.9, 133.8 (d, JC-P = 5.5 Hz), 132.0,
131.5, 131.2 (d, JC-P = 10.3 Hz), 129.1, 128.9, 128.7, 128.2, 127.7, 125.8-125.6 (m), 123.3 (dd, JC-F
=
272.9 Hz, JC-P = 5.6 Hz), 120.8, 119.7 (d, JC-P = 12.0 Hz), 119.0, 63.9 (d, JC-P = 6.9 Hz), 16.3 (d, JC-P
=
6.1 Hz). 31P NMR (162 MHz, CDCl3 ): δ = 5.6. HRMS (ESI-TOF) m/z: [M + H]+ calcd for C23H19F3O3P:
431.1018; found: 431.1020.
3,4-Bis(4-tert-butylphenyl)-1-phenyl-1H-2,1-benzoxaphosphorin 1-oxide (3p). A white solid; yield
71.94 mg (71%); mp 113 - 115 oC. IR (in KBr): 3130, 2961, 1608, 1244, 1060, 744 cm-1. 1H NMR (400
MHz, CDCl3) δ (ppm) = 8.00 - 7.89 (m, 2H), 7.63 - 7.57 (m, 2H), 7.51 (m, J = 7.6, 3.7 Hz, 2H), 7.43
(dd, J = 16.0, 8.0 Hz, 3H), 7.31 (dd, J = 7.5, 2.9 Hz, 1H), 7.23- 7.18 (m, 2H), 7.19 - 7.12 (m, 2H), 7.13 -
7.05 (m, 3H), 1.37 (s, 9H), 1.22 (s, 9H). 13C{1H} NMR (100 MHz, CDCl3) δ (ppm) = 151.2 (d, JC-P
=
57.7 Hz), 146.8 (d, JC-P = 11.0 Hz), 139.1 (d, JC-P = 5.3 Hz), 133.1, 132.7 (d, JC-P = 2.7 Hz), 132.4,
132.3, 131.8 (d, JC-P = 5.2 Hz), 131.2, 130.3 (d, JC-P = 144.2 Hz), 130.2 (d, JC-P = 12.2 Hz), 128.7, 128.6,
128, 127.3 (d, JC-P = 14.3 Hz), 126.9 (d, JC-P = 9.5 Hz), 125.8, 124.4, 123.0 (d, JC-P = 128.8 Hz), 118.5
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(d, JC-P = 10.8 Hz), 34.7, 34.5, 31.4, 31.1. P NMR (162 MHz, CDCl3 ): δ = 24.3. HRMS (ESI-TOF)
m/z: [M + H]+ calcd for C34H36O2P: 507.2447; found: 507.2442.
3,4-Bis(3,5-dimethylphenyl)-1-phenyl-1H-2,1-benzoxaphosphorin 1-oxide (3q). a white solid; yield
62.17 mg (69%); mp 80 - 81 oC. IR (in KBr): 3131, 2917, 2361, 1598, 1401, 1244, 1123, 905, 730 cm-1.
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1H NMR (400 MHz, CDCl3) δ (ppm) = 7.97 - 7.87 (m, 2H), 7.65 - 7.57 (m, 2H), 7.56 - 7.39 (m, 4H),
7.29 (s, 1H), 7.07 (dd, J = 8.2, 4.7 Hz, 1H), 7.00 (s, 1H), 6.90 (d, J = 10.7 Hz, 4H), 2.30 (s, 6H), 2.11 (s,
6H). 13C{1H} NMR (100 MHz, CDCl3) δ (ppm) = 146.8 (d, JC-P = 11.1 Hz), 139.1 (d, JC-P = 5.4 Hz),
136.7, 135.9, 134.4 (d, JC-P = 7.0 Hz), 132.8 (d, JC-P = 2.9 Hz), 132.4 (d, JC-P = 2.6 Hz), 132.3, 132.2,
131.0, 130.2, 130.1 (d, JC-P = 2.7 Hz), 129.6, 129.2 (d, JC-P = 3.3 Hz), 128.5 (d, JC-P = 13.9 Hz), 127.3 (d,
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C-P = 14.3 Hz), 127.0, 126.9, 123.0 (d, JC-P = 128.8 Hz), 118.9 (d, JC-P = 10.8 Hz), 21.2, 21.1. 31P NMR
(162 MHz, CDCl3 ): δ = 24.3. HRMS (ESI-TOF) m/z: [M + H]+ calcd for C30H28O2P: 451.1821; found:
451.1806.
3,4-Bis(4-methylphenyl)-1-phenyl-1H-2,1-benzoxaphosphorin 1-oxide (3r) (known compound).[5a]
yellow solid; yield 48.16 mg (57%); mp 222 - 224 oC. IR (in KBr): 3139, 2363, 1639, 1401, 1237, 1057,
944, 739 cm-1. H NMR (400 MHz, CDCl3) δ (ppm) = 7.92 (dd, J = 13.2, 7.7 Hz, 2H), 7.65 - 7.55 (m,
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2H), 7.54 - 7.46 (m, 2H), 7.42 (t, J = 7.5 Hz, 1H), 7.31 (t, J = 6.8 Hz, 1H), 7.23 - 7.11 (m, 6H), 7.09 -
7.01 (m, 1H), 6.90 (t, J = 11.5 Hz, 2H), 2.38 (s, 3H), 2.23 (s, 3H). 13C{1H} NMR (100 MHz, CDCl3) δ
(ppm) = 146.9 (d, JC-P = 11.0 Hz), 139.0 (d, JC-P = 5.2 Hz), 138.4, 137.4, 133.1, 132.9 (d, JC-P = 2.6 Hz),
132.4 (d, JC-P = 2.6 Hz), 132.3 (d, JC-P = 5.2 Hz), 131.9 (d, JC-P = 5.2 Hz), 131.4, 131.0, 130.2 (d, JC-P
=
12.3 Hz), 129.7, 129.5 (d, JC-P = 13.4 Hz), 128.6 (d, JC-P = 69.5 Hz), 128.5 (d, JC-P = 13.9 Hz), 127.3 (d,
JC-P = 14.2 Hz), 126.7 (d, JC-P = 9.5 Hz), 123.0 (d, JC-P = 128.7 Hz), 118.4 (d, JC-P = 11.0 Hz), 21.3, 21.2.
31P NMR (162 MHz, CDCl3 ): δ = 24.4. HRMS (ESI-TOF) m/z: [M + H]+ calcd for C28H24O2P:
423.1508; found: 423.1510.
3,4-Bis(2-methylphenyl)-1-phenyl-1H-2,1-benzoxaphosphorin 1-oxide (3s). A white solid; yield 67.59
mg (80%); mp 76 - 77 C. IR (in KBr): 3146, 2974, 2360, 1627, 1401, 1063, 948, 756 cm-1. H NMR
(400 MHz, CDCl3) δ (ppm) = 7.96 - 7.83 (m, 2H), 7.59 - 7.52 (m, 2H), 7.55 - 7.47 (m, 2H), 7.48 - 7.36
(m, 2H), 7.15 (d, J = 6.0 Hz, 2H), 7.10 - 7.03 (m, 5H), 6.95 - 6.78 (m, 2H), 2.40 (s, 3H), 2.17 (s, 1.7 H),
o
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2.11 (s, 1.3 H). 13C{1H} NMR (100 MHz, CDCl3) δ (ppm) = 148.5 (d, JC-P = 11.2 Hz), 148.3 (d, JC-P
=
11.1 Hz), 137.9, 137.3, 137.7 (d, JC-P = 5.2 Hz), 137.0 (d, JC-P = 4.5 Hz), 134.8 (d, JC-P = 15.7 Hz),
134.2 (d, JC-P = 4.5 Hz), 133.0 (d, JC-P = 3.0 Hz), 132.8, 132.6, 132.5, 131.9 (d, JC-P = 11.3 Hz), 131.4,
131.3, 130.5 (d, JC-P = 11.6 Hz), 130.4 (d, JC-P = 10.1 Hz), 130.1, 130.0, 130.0, 129.4 (d, JC-P = 88.1 Hz),
129.4, 128.8, 128.5, 128.4, 128.0, 125.6, 124.9 (d, JC-P = 3.6 Hz), 123.2 (d, JC-P = 128.5 Hz), 122.5 (d,
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C-P = 127.2 Hz), 119.3 (d, JC-P = 11.3 Hz), 118.4 (d, JC-P = 10.7 Hz), 29.7, 20.0 (d, JC-P = 4.3 Hz), 19.8.
31P NMR (162 MHz, CDCl3 ): δ = 25.3, 24.1. HRMS (ESI-TOF) m/z: [M + H]+ calcd for C28H24O2P:
423.1508; found: 423.1509.
3,4-Bis(4-fluorophenyl)-1-phenyl-1H-2,1-benzoxaphosphorin 1-oxide (3t). A white solid; yield 60.25
mg (70%); mp 167 - 168 oC. IR (in KBr): 3133, 1619, 1507, 1401, 1226, 1059, 950, 743 cm-1. 1H NMR
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(400 MHz, CDCl3) δ (ppm) = 7.93 (dd, J = 13.4, 7.5 Hz, 2H), 7.68 - 7.58 (m, 1H), 7.57 - 7.51 (m, 3H),
7.47 (t, J = 7.8 Hz, 1H), 7.36 (dd, J = 7.5, 2.8 Hz, 1H), 7.25 - 7.19 (m, 4H), 7.10 (t, J = 8.4 Hz, 2H),
7.03 (dd, J = 8.2, 4.8 Hz, 1H), 6.83 (t, J = 8.5 Hz, 2H). 13C{1H} NMR (100 MHz, CDCl3) δ (ppm) =
162.4 (d, JC-F = 248.6 Hz), 161.3 (d, JC-F = 246.7 Hz), 146.2 (d, JC-P = 10.8 Hz), 133.3, 133.2, 133.1 (d,
JC-P = 2.8 Hz), 132.6 (d, JC-P = 2.5 Hz), 132.5, 132.3, 131.8 (d, JC-P = 3.7 Hz), 131.1 (d, JC-P = 8.3 Hz),
130.4, 130.3, 128.6 (d, JC-P = 14.0 Hz), 127.8 (d, JC-P = 14.5 Hz), 126.5 (d, JC-P = 9.8 Hz), 123.2 (d, JC-P
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= 128.9 Hz), 118.2 (d, JC-P = 12.2 Hz), 116.1 (d, JC-F = 21.1 Hz), 114.8 (d, JC-F = 21.6 Hz). P NMR
(162 MHz, CDCl3 ): δ = 24.5. HRMS (ESI-TOF) m/z: [M + H]+ calcd for C26H18F2O2P: 431.1007; found:
431.1004.
3,4-Bis(4-chlorophenyl)-1-phenyl-1H-2,1-benzoxaphosphorin 1-oxide (3u) (known compound).[5a]
A
white solid; yield 56.52 mg (61%); mp 90 - 93 oC. IR (in KBr): 3131, 1589, 1487, 1400, 1236, 1090,
948, 748 cm-1. 1H NMR (400 MHz, CDCl3) δ (ppm) = 7.97 - 7.86 (m, 2H), 7.67 - 7.50 (m, 4H), 7.47 (t,
J = 7.7 Hz, 1H), 7.46 - 7.38 (m, 3H), 7.21 (d, J = 7.9 Hz, 2H), 7.18 - 7.09 (m, 4H), 7.01 (dd, J = 8.2, 4.9
Hz, 1H). 13C{1H} NMR (100 MHz, CDCl3) δ (ppm) = 146.0 (d, JC-P = 10.9 Hz), 137.9 (d, JC-P = 5.1 Hz),
134.7, 134.2 (d, JC-P = 6.5 Hz), 133.2 (d, JC-P = 2.9 Hz), 133.0, 132.9, 132.6 (d, JC-P = 2.5 Hz), 132.4 (d,
J
C-P = 11.1 Hz), 130.5, 130.3, 130.1, 129.4, 128.7 (d, JC-P = 14.0 Hz), 128.6, 128.0, 127.9 (d, JC-P = 14.3
Hz), 126.6 (d, JC-P = 9.5 Hz), 123.2 (d, JC-P = 128.9 Hz), 118.5 (d, JC-P = 11.1 Hz). 31P NMR (162 MHz,
CDCl3 ): δ = 24.5. HRMS (ESI-TOF) m/z: [M + H]+ calcd for C26H18Cl2O2P: 463.0416; found:
463.0430.
3,4-Bis(4-bromophenyl)-1-phenyl-1H-2,1-benzoxaphosphorin 1-oxide (3v) (known compound).[5a]
A
white solid; yield 27.61 mg (25%); mp 193 - 194 oC. IR (in KBr): 3132, 1633, 1400, 1239, 1072, 947,
746 cm-1. 1H NMR (400 MHz, CDCl3) δ (ppm) = 7.89 - 7.79 (m, 2H), 7.60 - 7.50 (m, 1H), 7.47 (dd, J =
6.1, 4.1 Hz, 5H), 7.40 (t, J = 8.2 Hz, 1H), 7.33 - 7.27 (m, 1H), 7.23 - 7.17 (m, 2H), 7.08 (d, J = 7.9 Hz,
2H), 7.02 (d, J = 8.4 Hz, 2H), 6.94 (dd, J = 8.1, 4.8 Hz, 1H). 13C{1H} NMR (100 MHz, CDCl3) δ (ppm)
= 146.0 (d, JC-P = 10.8 Hz), 137.9 (d, JC-P = 5.1 Hz), 134.7, 133.4 (d, JC-P = 5.1 Hz), 133.2, 133.1, 132.7
(d, JC-P = 2.4 Hz), 132.5, 132.4, 132.3, 131.0, 130.4 (d, JC-P = 12.4 Hz), 130.2, 128.6 (d, JC-P = 14.1 Hz),
128.0 (d, JC-P = 14.4 Hz), 126.6 (d, JC-P = 9.4 Hz), 123.2 (d, JC-P = 128.8 Hz), 123.1, 122.3, 118.6 (d, JC-
= 11.1 Hz). 31P NMR (162 MHz, CDCl3 ): δ = 24.6. HRMS (ESI-TOF) m/z: [M + H]+ calcd for
P
C26H18Br2O2P: 550.9406; found: 550.9408.
According to the general procedure, the mixture of 3w and 3w’ were obtained by column
chromatography with the eluting (petroleum ether/ethyl acetate = 3/1) as a white solid, yield 64.3 mg
(75%). The ratio of the isomers were determined based on the intergration of the character peak located
at 2.40 ppm (H-1 of 3w) and 2.25 ppm (H-1’of 3w’) and by 31P NMR, the ratio of isomers (3w/3w’) is
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3:1.4. The mixture of 3w and 3w’: IR (in KBr): 3130, 2361, 1637, 1506, 1400, 952, 750 cm-1. 1H NMR
(400 MHz, CDCl3) δ (ppm) = 7.96 - 7.90 (m, 2H), 7.65 - 7.51 (m, 4H), 7.48 - 7.42 (m, 1H), 7.35 - 7.31
(m, 1H), 7.25 -7.19 (m, 3H), 7.16 – 6.99 (m, 4H), 6.94 (d, J = 8.1 Hz, 1H), 6.81 (t, J = 8.7 Hz, 1H), 2.41
13
(s, 2.05 H), 2.25 (s, 0.95 H). C{1H} NMR (100 MHz, CDCl3) δ (ppm) = 162.4 (d, JC-F = 248.3 Hz),
145.8 (d, JC-P = 10.7 Hz), 138.8-138.7 (m), 137.8, 133.4 (d, JC-P = 7.7 Hz), 133.1(d, JC-P = 2.8 Hz),
132.8, 132.5, 132.5, 132.5, 132.4, 132.4, 132.3, 131.4, 131.1 (d, JC-P = 8.3 Hz), 130.3, 130.2, 129.8,
129.0, 128.7, 128.5, 128.4, 127.8 (d, JC-F = 9.6 Hz), 126.9 (d, JC-F = 9.6 Hz), 123.1 (d, JC-P = 129.0 Hz),
114.7 (d, JC-P = 21.6 Hz), 21.3, 21.2. MP 76 - 78 oC. 31P NMR (162 MHz, CDCl3): δ = 24.5, 24.4 (3:1.4).
HRMS (ESI-TOF) m/z: [M + H]+ calcd for C27H21FO2P: 427.1258; found: 427.1245.
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According to the general procedure, the mixture of 3x and 3x’ were obtained by column
chromatography with the eluting (petroleum ether/ethyl acetate = 3/1) as a white solid, yield 45.2 mg
(47%). The ratio of the isomers were determined based on the intergration of the character peak located
31
at 2.40 ppm (H-1 of 3x) and 2.25 ppm (H-1’ of 3x’) and by P NMR. The ratio of isomers (3x/3x’) is
3:1.3. The pure isomer 3x was isolated further by HPLC. 3x: mp 77 - 78 oC. IR (in KBr): 3478, 3234,
3133, 2027, 1638, 1617, 1469, 1401, 1242, 949, 742 cm-1. 1H NMR (400 MHz, CDCl3) δ (ppm) = 7.98 -
7.89 (m, 2H), 7.62 (d, J = 1.6 Hz, 2H), 7.56 - 7.52 (m, 2H), 7.47 (t, J = 8.0 Hz, 1H), 7.36 (s, 5H), 7.22
(d, J = 7.7 Hz, 2H), 7.15 (d, J = 7.6 Hz, 2H), 7.09 (dd, J = 8.2, 4.8 Hz, 1H), 2.42 (s, 3H). 13C{1H} NMR
(100 MHz, CDCl3) δ (ppm) = 144.9 (d, JC-P = 10.7 Hz), 138.4 (d, JC-P = 5.2 Hz), 138.1, 133.2 (d, JC-P
3.0 Hz), 132.6 (d, JC-P = 2.6 Hz), 132.4, 132.3, 132.2, 131.2, 130.2 (d, JC-P = 12.4 Hz), 130.1 (d, JC-P
=19.1 Hz), 130.0-129.8 (m), 129.3, 128.8 (d, JC-P = 14.2 Hz), 128.6 (d, JC-P = 13.9 Hz), 128.0 (d, JC-P
=
=
14.5 Hz), 127.1 (d, JC-P = 9.5 Hz), 123.8 (d, JC-P = 170.8 Hz), 124.5 - 124.4 (m), 123.4 (d, JC-F = 129.1
Hz), 120.5 (d, JC-P = 11.0 Hz), 21.3. 31P NMR (162 MHz, CDCl3 ): δ = 24.6. HRMS (ESI-TOF) m/z: [M
+ H]+ calcd for C28H21F3O2P: 477.1226; found: 477.1201.
Acknowledgment: We are grateful to the National Natural Science Foundation of China (NOs.
21472057, 21772053) and Program of Introducing Talents of Discipline to Universities of China (111
Program, B17019) and the Open Project of Key Laboratory of Theoretical Chemistry & Molecular
Simulation of Ministry of Education, Hunan University of Science and Technology (LKF104) for the
financial support of this research.
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Supporting Information Available Full experimental details, spectroscopic data of 3, CIF file for 3a,
3w and 3x. This material is available free of charge via the Internet at http://pubs.acs.org.
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References
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(1) (a) Montchamp, J. L. Phosphinate Chemistry in the 21st Century: A Viable Alternative to the Use
of Phosphorus Trichloride in Organophosphorus Synthesis. Acc. Chem. Res. 2014, 47, 77. (b) Demmer,
C. S.; Krogsgaard-Larsen, N.; Bunch, L. Review on Modern Advances of Chemical Methods for the
Introduction of a Phosphonic Acid Group. Chem. Rev. 2011, 111, 7981. (c) Mucha, A.; Kafarski, P.;
Berlicki, L. Remarkable potential of the α-Aminophosphonate/Phosphinate Structural Motif in
Medicinal Chemistry. J. Med. Chem. 2011, 54, 5955. (d) Quin, L. D. A Guide to Organophosphorus
Chemistry, Wiley, New York, 2000. (e) Corbridge, D. E. C. Phosphorus: Chemistry, Biochemistry and
Technology, CRC Press, 6th edn. 2013. (f) Seto, H.; Kuzuyama, T. Bioactive Natural Products with
Carbon-Phosphorus Bonds and their Biosynthesis. Nat. Prod. Rep. 1999, 16, 589. (g) Han, L.-B.; Ono,
Y.; Xu, Q.; Shimada, S. Highly Selective Markovnikov Addition of Hypervalent H-Spirophosphoranes
to Alkynes Mediated by Palladium Acetate: Generality and Mechanism. Bull. Chem. Soc. Jpn. 2010, 83,
1086.
(2) (a) Maryanoff, B. E.; Reitz, A. B. The Wittig Olefination Reaction and Modifications Involving
Phosphoryl-Stabilized Carbanions. Stereochemistry, Mechanism, and Selected Synthetic Aspects. Chem.
Rev. 1989, 89, 863. (b) Ma, X.-T.; Wang, Y.; Dai, R.-H.; Liu, C.-R.; Tian, S.-K. Catalytic Allylation of
Stabilized Phosphonium Ylides with Primary Allylic Amines. J. Org. Chem. 2013, 78, 11071. (c)
Boutagy, J.; Thomas, R. Olefin Synthesis with Organic Phosphonate Carbanions. Chem. Rev. 1974, 74,
87. (d) Kamer, P. C. J.; Leeuwen, P. W. N. M. Phosphorus (III) Ligands in Homogeneous Catalysis:
Design and Synthesis; Wiley, 2012. (e) McManus, H. A.; Guiry, P. J. Recent Developments in the
Application of Oxazoline-Containing Ligands in Asymmetric Catalysis. Chem. Rev. 2004, 104, 4151. (f)
Birkholz, M. N.; Freixa, Z.; van Leeuwen, P. W. Bite Angle Effects of Diphosphines in C-C and C-X
Bond Forming Cross Coupling Reactions. Chem. Soc. Rev. 2009, 38, 1099. (g) Tang, W.-J.; Zhang, X.-
22
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1
2
3
4
5
6
7
8
M. New Chiral Phosphorus Ligands for Enantioselective Hydrogenation. Chem. Rev. 2003, 103, 3029.
(h) Zhou, Y.-G. Asymmetric Hydrogenation of Heteroaromatic Compounds. Acc. Chem. Res. 2007, 40,
1357.
9
(3) (a) Ruda, G. F.; Wong, P. E.; Alibu, V. P.; Norval, S.; Read, K. D.; Barrett, M. P.; Gilbert, I. H.
Aryl Phosphoramidates of 5-Phospho Erythronohydroxamic Acid, a new class of Potent Trypanocidal
Compounds. J. Med. Chem. 2010, 53, 6071. (b) Li, B.; Zhou, B.; Lu, H.; Ma, L.; Peng, A.-Y.
Phosphaisocoumarins as a new class of Potent Inhibitors for Pancreatic Cholesterol Esterase. Eur. J.
Med. Chem. 2010, 45, 1955. (c) Li, X. S.; Zhang, D. W.; Pang, H.; Shen, F.; Fu, H.; Jiang, Y. Y.; Zhao,
Y. F. Synthesis of a Diverse Series of Phosphacoumarins with Biological Activity. Org. Lett. 2005, 7,
4919.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
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42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(4) (a) Peng, A.-Y.; Ding, Y.-X. The Synthesis of Phosphaisocoumarins by Cu(I)-Catalyzed
Intramolecular Cyclization of O-Ethynylphenylphosphonic Acid Monoesters. J. Am. Chem. Soc. 2003,
125, 15006. (b) Peng, A.-Y.; Hao, F.; Li, B.; Wang, Z.; Du, Y. An Efficient Route to 4-
Halophosphaisocoumarins
via
CuX2-Mediated
Direct
Halocyclization
of
2-(1-
Alkynyl)phenylphosphonic Acid Diesters. J. Org. Chem. 2008, 73, 9012.
(5) (a) Park, Y.; Jeon, I.; Shin, S.; Min, J.; Lee, P. H. Ruthenium-Catalyzed C-H
Activation/Cyclization for the Synthesis of Phosphaisocoumarins. J. Org. Chem. 2013, 78, 10209. (b)
Seo, J.; Park, Y.; Jeon, I.; Ryu, T.; Lee, P. H. Synthesis of Phosphaisocoumarins through Rhodium-
Catalyzed Cyclization using Alkynes and Arylphosphonic Acid Monoesters. Org. Lett., 2013, 15, 3358.
(c) Park, Y.; Seo, J.; Park, S.; Yoo, E. J.; Lee, P. H. Rhodium-Catalyzed Oxidative C-H
Activation/Cyclization for the Synthesis of Phosphaisocoumarins and Phosphorous 2-Pyrones. Chem.
Eur. J. 2013, 19, 16461.
(6) (a) Prier, C. K.; Rankic D. A.; MacMillan, D. W. Visible light Photoredox Catalysis with
Transition Metal Complexes: Applications in Organic Synthesis. Chem. Rev. 2013, 113, 5322. (b)
Narayanam, J. M.; Stephenson, C. R. Visible Light Photoredox Catalysis: Applications in Organic
Synthesis. Chem. Soc. Rev. 2011, 40, 102. (c) Xuan, J.; Xiao, W. J. Visible-Light Photoredox Catalysis.
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7
8
9
Angew. Chem., Int. Ed. 2012, 51, 6828. (d) Romero, N. A.; Nicewicz, D. A. Organic Photoredox
Catalysis. Chem. Rev. 2016, 116, 10075. (e) Hari, D. P.; König, B. The Photocatalyzed Meerwein
Arylation: Classic Reaction of Aryl Diazonium Salts in a new Light. Angew. Chem., Int. Ed. 2013, 52,
4734. (f) Yasu, Y.; Koike, T.; Akita, M. Three-Component Oxytrifluoromethylation of Alkenes: Highly
Efficient and Regioselective Difunctionalization of C-C Bonds Mediated by Photoredox Catalysts.
Angew. Chem. Int. Ed. 2012, 51, 9567.
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18
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20
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59
60
(7) (a) Zhang, G.; Liu, C.; Yi, H.; Meng, Q.; Bian, C.; Chen, H.; Jian, J.; Wu, L,-Z.; Lei, A. 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. (b) Hu, X.; Zhang, G.; Bu, F.; Lei, A.
Selective Oxidative [4+2] Imine/Alkene Annulation with H2 Liberation Induced by Photo-Oxidation.
Angew. Chem. Int. Ed. 2018, 57, 1286. (c) Yang, Q.; Zhang, L.; Ye, C.; Luo, S.; 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. (d) Xiang, M.; Meng, Q.-Y.;
Li, J.-X.; Zheng, Y.-W.; Chen Ye, C.; Li, Z.-J.; Chen, B.; Tung, C.-H.; Wu, L.-Z. Activation of C-H
Bonds through Oxidant-Free Photoredox Catalysis: Cross-Coupling Hydrogen-Evolution
Transformation of Isochromans and β-Keto Esters. Chem. Eur. J. 2015, 21, 18080. (e) Yang, X.-L.; Gao,
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. (f) 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. (g) Zhao, Q.-Q.; Hu, X. Q.; Yang, M.-N.; Chen, J.-R.; Xiao, W.-J.
A Visible-light Photocatalytic N-radical Cascade of Hydrazones for the Synthesis of Dihydropyrazole-
fused Benzosultams. Chem. Commun. 2016, 52, 12749. (h) 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. (i) Tian, W.-F.;
Wang, D.-P.; Wang, S.-F.; He, K.-H.; Cao, X.-P.; Li, Y. Visible-Light Photoredox-Catalyzed Iminyl
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Radical Formation by N-H Cleavage with Hydrogen Release and Its Application in Synthesis of
Isoquinolines. Org. Lett. 2018, 20, 1421. (j) Yang, Q.; Jia, Z.; Li, L.; Luo, S. Visible-light Promoted
Arene C-H/C-X Lactonization via Carboxylic Radical Aromatic Substitution. Org. Chem. Front., 2018,
5, 237.
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(8) CCDC 1851666 (3a), 1880620 (3w) and 1879737 (3x) contain the supplementary crystallographic
data for this paper. These data can be obtained free of charge from the Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
(9) Joshi-Pangu, A.; Lévesque, F.; Roth, H. G.; Oliver, S. F.; Campeau, L.-C.; Nicewicz, D. A.;
DiRocco, D. A. Acridinium-Based Photocatalysts: A Sustainable Option in Photoredox Catalysis. J.
Org. Chem. 2016, 81, 7244.
(10) Romero, N. A.; Nicewicz, D. A. Mechanistic Insight into the Photoredox Catalysis of anti-
Markovnikov Alkene Hydrofunctionalization Reactions. J. Am. Chem. Soc. 2014, 136, 17024.
(11) The Cobalt catalyst showed rather lower oxidation potential Co (dmgH)2 PyCl (Eox(CoIII/II) = -0.68
V vs SCE and Eox
= -1.13 V vs SCE), excluding the possibility of direct participation of Co
(CoII/I)
catalyst in substrate oxidation (oxidation potential of 1a in the presence of CsF is 1.67 V vs SCE).
Please see: Dempsey, J. L.; Brunschwig, B. S.; Winkler, J. R. and Gray, H. B. Hydrogen Evolution
Catalyzed by Cobaloximes. Acc. Chem. Res., 2009, 42, 1995.
(12) Lazarides, T.; McCormick, T.; Du, P.; Luo, G.; Lindley, B.; Eisenberg, R. Making Hydrogen
from Water using a Homogeneous System without Noble Metals. J. Am. Chem. Soc. 2009, 131, 9192.
(13) Lei, W.-L.; Yang, B.; Zhang, Q.-B.; Yuan, P.-F.; Wu, L.-Z.; Liu, Q. Visible-light-enabled
Aerobic Synthesis of Benzoin Bis-ethers from Akynes and Alcohols. Green Chem., 2018, 20, 5479.
(14) Du, P.; Schneider, J.; Luo, G.; Brennessel, W. W.; Eisenberg, R. Visible Light-Driven
Hydrogen Production from Aqueous Protons Catalyzed by Molecular Cobaloxime Catalysts. Inorg.
Chem. 2009, 48, 4952.
(15) (a) Mio, M. J.; Kopel, L. C.; Braun, J. B.; Gadzikwa, T. L.; Hull, K. L.; Brisbois, R. G.;
Markworth, C. J.; Grieco, P. A. One-Pot Synthesis of Symmetrical and Unsymmetrical Bisarylethynes
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by a Modification of the Sonogashira Coupling Reaction. Org. Lett. 2002, 4, 3199. (b) Park, K.; Bae, G.;
Moon, Choe, J.; Song, K. H.; Lee, S. Synthesis of Symmetrical and Unsymmetrical Diarylalkynes from
Propiolic Acid using Palladium-Catalyzed Decarboxylative Coupling. J. Org. Chem. 2010, 75, 6244. (c)
Severin, R.; Reimer, J.; Doye, S. One-pot Procedure for the Synthesis of Unsymmetrical Diarylalkynes.
J. Org. Chem. 2010, 75, 3518.
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(16) Qi, N.; Zhang, N.; Allu, S. R.; Gao, J.; Guo, J.; He, Y. Insertion of Arynes into P-O Bonds:
One-Step Simultaneous Construction of C-P and C-O Bonds. Org. Lett. 2016, 18, 6204.
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