Copper-catalyzed C–P cross-coupling of secondary phosphines with (hetero)aromatic bromide

Article abstract of DOI:10.1007/s11164-018-3403-3

A novel and convenient approach to the synthesis of various tertiary phosphines via a copper-catalyzed cross-coupling of (hetero)aromatic bromide with secondary phosphines has been developed. The reaction employs cheap copper as the catalyst, 2,6-bis(N-methylaminomethyl)pyridine (L4) as a perfect ligand and KO^tBu as a base; all reactions are carried out under argon atmosphere. A variety of sterically hindered and/or functionalized substrates were found to react under these reaction conditions to provide products in good to excellent yields. Moreover, ten new tertiary phosphines were first reported in this process.

Full text of DOI:10.1007/s11164-018-3403-3

Res Chem Intermed
https://doi.org/10.1007/s11164-018-3403-3
Copper-catalyzed C–P cross-coupling of secondary
phosphines with (hetero)aromatic bromide
Chun-Jing Li1 Jing Lu¨1
Zhi-Xun Zhang1 Kun Zhou1
•
•
•
•
Yan Li1 Guang-Hui Qi1
•
Received: 15 September 2017 / Accepted: 19 March 2018
Ó Springer Science+Business Media B.V., part of Springer Nature 2018
Abstract A novel and convenient approach to the synthesis of various tertiary
phosphines via a copper-catalyzed cross-coupling of (hetero)aromatic bromide with
secondary phosphines has been developed. The reaction employs cheap copper as
the catalyst, 2,6-bis(N-methylaminomethyl)pyridine (L4) as a perfect ligand and
KOtBu as a base; all reactions are carried out under argon atmosphere. A variety of
sterically hindered and/or functionalized substrates were found to react under these
reaction conditions to provide products in good to excellent yields. Moreover, ten
new tertiary phosphines were first reported in this process.
Keywords Copper-catalyzed Á C–P bond Á Phosphorization
Introduction
Phosphines and their derivatives represent an important class of compounds that
have broad applications in the fields of organic synthesis, materials, ligand
chemistry, pharmaceuticals, and agrochemicals [1–5]. Especially in transition
metal-catalyzed reactions, tertiary phosphines have been used as preferred ligands
due to their robust C–P bonds and the unique opportunity to modify the steric and
electronic properties of the ligand. Meanwhile, the C–P bond activation of tertiary
Chun-Jing Li and Jing Lu¨ contributed equally to this work.
&
&
1
Chun-Jing Li
wyclichunjing@126.com
Jing Lu¨
lvjingwenzhang@163.com
Department of Chemistry and Environmental Engineering, Hebei Chemical and Pharmaceutical
College, Shijiazhuang 050026, China
123

C.-J. Li et al.
phosphines by transition metals is a fundamental reaction and an important research
topic in both modern experimental and theoretical chemistry [6–11]. Currently, four
major methods are used for the synthesis of tertiary phosphines: Friedel–Crafts
reactions [12], reaction of organometallic reagents with halophosphines [13–17],
nucleophilic substitution with metallated organophosphines [18, 19], and catalytic
C–P bond formation [20]. Tertiary phosphines can be also prepared without catalyst
[21], solvent, and ligand [22]. In 1987, Tunney and Stille reported the palladium-
catalyzed synthesis of several aryldiphenylphosphines [23]. Later, nickel(0)-
catalyzed protocols were employed [24]. Copper was first used as a co-catalyst in
palladium-catalyzed phosphorylation reactions [25]. The Ullmann-type chemistry
showed that the formation of carbon–nitrogen, carbon–oxygen, and carbon–sulfur
bonds may be performed using a catalytic quantity of a copper complex [26–29]. In
the past decades, the DV group [26, 30–36], Buchwald group [28, 37–50], and
others [51–55] have been developing copper-catalyzed cross-coupling reactions.
These methods have demonstrated increased functional group tolerance, good
economy, and the choice for large- and industrial-scale reactions. This cheaper and
more convenient alternative form of catalysis was used in C–P bond formation
[35, 42, 56–61]. Although the majority of efforts have been focused on the C–P
bond formation, the system is limited to aryl iodides [59, 62–69]. Herein, we report
an inexpensive copper-catalyzed method by the cross-coupling of (hetero)aromatic
bromide with secondary phosphines for the formation of unsymmetrical tertiary
phosphines.
Results and discussion
Bromonaphthalene and di-(4-methoxyphenyl)-phosphine were selected as proto-
typical reaction partners for optimization of reaction conditions. At the outset, the
reaction was carried out using two equivalents (eq.) of cesium carbonate under
metal-free conditions for 24 h; no product 3a was detected (Table 1, entry 1.;
However, after addition of 5 mol% of CuI and 24 h, the desired P–C product was
31
formed in a 55% yield and P nuclear magnetic resonance (NMR) spectroscopy
showed the starting material disappeared (Table 1, entry 2). These results indicated
that the cross-coupling was feasible. The reports demonstrated that certain additives
could be employed to enhance the efficiency of copper-catalyzed reactions
[28, 35, 42, 57–61, 70–75]. Therefore, we decided to test commercially available
1,2-bis(methylamino)ethane (L5) as a ligand for the copper-catalyzed cross-
coupling. Various copper salts were screened under similar conditions, of which CuI
showed the highest activity and efficacy, whereas other tested salts, Cu(OAc)2,
CuCl, CuO, CuBr, and Cu(OTf)2 were less effective (Table 1, entries 3–8). The
yield does not exceed that of the increased CuI eq. (Table 1, entry 9). CuI showed
relatively higher catalytic efficiency compared with other copper salts and was thus
chosen as the catalyst for further optimization.
To advance the process further, a survey on the role of ligands for the C–P bond
formation revealed 2,6-bis(N-methylaminomethyl)pyridine (L4) as the most favored
one to push the reaction forward (Table 2, entries 1–4). Without the ligand, a
123

Copper-catalyzed C–P cross-coupling of secondary…
Table 1 Optimization of copper source
Entry
Catalyst
Yield (%)a
1b
2c
3
–
–
CuI
55
77
35
24
55
47
60
79
CuI
4
Cu(OAc)2
CuO
5
6
CuCl
CuBr
Cu(OTf)2
CuI
7
8
9d
Reaction conditions: 1a (1 mmol), 2a (1 mmol), copper salt (0.05 mmol), Cs2CO3 (2.0 eq.), L5
(0.3 mmol) in 3 ml of toluene at 110 °C for 24 h, under argon atmosphere
aIsolated yield based on secondary phosphine
bCs2CO3 (2.0 eq.) without copper salt
cCs2CO3 (2.0 eq.), CuI (0.05 mmol) without L5
dCuI (0.10 mmol)
considerably lower yield was observed under similar reaction conditions (Table 1,
entry 2). Encouraged by the above promising results, in addition to Cs2CO3, other
bases were also investigated (Table 2, entries 5–8), such as KOtBu, NaOtBu, and
K2CO3, all of which gave good yields. However, pyridine (Table 2, entries 8), a
weak organic base, resulted in a very low yield. The effect of solvents was also
investigated (Table 2, entries 9–14), such as tetrahydrofuran (THF), acetonitrile
(CH3CN), dichloromethane (CH2Cl2), and component solvent. The better solvent
confirmed that component solvent (THF-to-toluene = 1:5) was the best choice for
this reaction (Table 2, entry 12).
With these optimized reaction conditions, a variety of substrates were surveyed
under similar reaction conditions (Table 3). As demonstrated in Table 3, the
substrates bearing different functional groups were all efficiently coupled and
provided the corresponding unsymmetrical tertiary phosphines in excellent isolated
yields, showing that this protocol is a general method for the phosphorization of
(hetero)aromatic bromides and secondary phosphines. Thus, a variety of functional
groups, such as methyl, methoxyl, trifluoromethyl, phenyl, chloro, bromo, iodo,
carboxylate, acylamino, and cyano were all tolerated. Substrates with electron-rich
groups like 1e and 1m were readily phosphorylated to produce the expected
products in passable yields (Table 3, entries 5 and 14). Similarly, unsubstituted
arybromide reacted with secondary phosphine 2e to afford the coupled products 3l
123

C.-J. Li et al.
Table 2 Ligand, base, and solvent effects on reactivity
H
P
Br
5 mol% CuI, 30 mol% Ligand
Base, Sovent, 100oC, 24h
P
+
O
O
O
N
O
1a
2a
3a
H
N
N
N
N
N
H
N
N
N
N
N
H
H
H
L1
L2
L3
L4
L5
Entry
Ligand
Base
Solventb
Yield (%)a
1
L1
L2
L3
L4
L4
L4
L4
L4
L4
L4
L4
L4
L4
L4
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
K2CO3
KOtBu
NaOtBu
Py
KOtBu
KOtBu
KOtBu
KOtBu
KOtBu
KOtBu
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
THF
67
60
71
82
79
86
83
36
82
68
42
93
70
88
2
3
4
5
6
7
8
9
10
11
12
13
14
CH3CN
CH2Cl2
THF-to-toluene (1:5)
THF-to-toluene (1:1)
THF-to-toluene (1:6)
Reaction conditions: 1a (1 mmol), 2a (1 mmol), CuI (0.05 mmol), base (2.0 eq.), ligand (0.3 mmol) in 3
mL of solvent at 100–110 °C for 24 h, under argon atmosphere
aIsolated yield based on secondary phosphine
bTetrahydrofuran (THF); acetonitrile (CH3CN); dichloromethane (CH2Cl2)
in satisfactory yields (Table 2). Substrates with electron-withdrawing groups such
as 1b, 1f, 1g, 1j, 1k, and 1n were coupled well with this protocol to acquire
moderate yields (Table 3, entries 2, 6, 7, 11, 12, and 15). Ortho-substituted chloride
1h and sterically demanding ortho-substituted counterpart 1c afforded similar yields
of 82 and 88%, respectively, illustrating that steric hindrance is not evident in this
coupling reaction (Table 3, entries 8 and 3). Notably, ortho-substituted iodide
produced a lower yield of 38% (Table 3, entry 9). Unfortunately, chemoselective
phosphination of bromoiodoarenes 1i was problematic because of the formation of a
123

Copper-catalyzed C–P cross-coupling of secondary…
Table 3 Copper-catalyzed C–P cross-coupling
Entry R-X
1
HPR1R2
Product
Yielda (%)
X = Br (93%)
X = I (95%)
X
H
P
O
O
O
O
X=Br, I
P
2a
1a
3a
2
3
79
CN
Br
H
P
CN
P
O
N
N
O
O
2a
1b
O
3b
X = Br (98%)
X = I (91%)
H
P
O
O
X
O
O
P
2a
X=Br, I
1c
3c
3d
H
P
4
5
81
90
Br
N
N
P
1d
2b
2b
H
P
O
P
O
Br
1e
3e
123

C.-J. Li et al.
Table 3 continued
Entry R-X
HPR1R2
Product
Yielda (%)
77
H
O
6
P
Br
O
O
O
1f
2b
P
3f
H
P
CN
P
7
79
NC
Br
1g
2b
3g
8
82
38
42
Cl
H
P
Cl
Br
P
F
F
F
F
F
F
F
F
F
F
1h
F
F
3h
2c
9
I
H
P
I
P
Br
F
F
F
F
F
FF
F
F
F
F
F
3i
10
Br
P
F
F
F
F
F
F
2c
2d
1i
3i-1
H
P
CN
11
X = Br (81%)
X = I (83%)
CN
P
X
1j
3j
123

Copper-catalyzed C–P cross-coupling of secondary…
Table 3 continued
Entry R-X
12
HPR1R2
Product
Yielda (%)
X = Br (78%)
X = I (84%)
H
O
N
O
P
N
X
P
P
2d
X=Br,I
1k
3
k
H
P
13
14
15
77
78
75
Br
1l
2e
2e
2e
3l
H
P
Br
P
F
1m
3m
H
P
F
F
F
F
F
Br
P
1n
3n
Reaction conditions: 1a (1 mmol), 2a (1 mmol), CuI(0.05 mmol), KOtBu (2.0 eq.), L4 (0.3 mmol) in 3
mLof THF/Toluene(1/5) at 100 °C for 24 h, under argon atmosphere
aIsolated yield based on secondary phosphine
complex mixture of mono- (Table 3, entries 9 and 10) and a small amount of
disubstituted product [42]. We also screened (hetero)aromatic iodides with
secondary phosphines and obtained the desired products in 95% (3a), 91% (3c),
83% (3j), and 84% (3k) yields (Table 3, entries 1, 3, 11, and 12).
Conclusions
In conclusion, we have developed a novel copper-catalyzed C–P cross-coupling
protocol from a wide range of (hetero)aromatic bromides and different secondary
phosphines. As one of its notable features, the protocol tolerated a variety of useful
functional groups. Moreover, it exhibits good compatibility with various types of
secondary phosphines and allows them to be coupled efficiently. These advantages
persuade us that this C–P bond-forming method should find broad application in
both complex molecule synthesis and P-chiral organophosphorus compound
synthesis applications.
123

C.-J. Li et al.
Experimental
General
Copper(I) iodide (98%), copper(I) bromide (98%), copper(I) chloride (99%), and
copper(II) trifluoromethanesulfonate were purchased from Aldrich. Copper acetate,
copper(II) oxide, and cesium carbonate were purchased from Alfa Aesar. Other
reagents are available commercially and were used without further purification,
unless otherwise indicated. Reactions were run under an argon atmosphere with
exclusion of moisture from reagents and glassware using standard Schlenk
techniques. Solvents were dried from molecular sieves and kept under argon.
Spectroscopy data of the known compounds matches with the data reported in the
corresponding references. All new compounds were further characterized by
1
element analysis, and 31P, 19F, H, and 13C NMR spectra were measured on a
Bruker 400 M spectrometer. 1H NMR and 13C NMR were recorded using
tetramethylsilane (TMS) in the solvent of deuterated chloroform (CDCl3) as the
internal standard and 85% H3PO4 as external standard for 31P NMR. Chemical shifts
were reported in parts per million (d). The peak patterns are indicated as follows: s,
singlet; d, doublet; t, triplet; dd, doublet of doublets; dt, doublet of triplets; and m,
multiplet. The coupling constant, J, is reported in hertz (Hz). The products were
purified by column chromatography on silica gel 300–400 mesh under an argon
atmosphere.
Experimental section
General procedure A: symmetric secondary phosphine oxides
Bis-(4-methoxyphenyl)-phosphine oxide [76] Symmetric secondary phosphine
oxides were prepared by the method of Hays [77, 78] by adding 1 eq. of
diethylphosphite to 3.3 eq. of the corresponding Grignard reagent at 0 °C and
warming to ambient temperature. A 100-mL round-bottom flask equipped with an
addition funnel was evacuated/Ar filled, then charged with 33 mL of 1 M
4-methoxyphenylmagnesium bromide/THF (33 mmol, 3.3 eq.), and the solution
cooled to 0 °C under Ar. A solution of 1.38 g of diethylphosphite (10 mmol,
1.0 eq.) in 10 mL of THF was then added dropwise over 10 min. The mixture was
aged 10 min at 0 °C, then the bath was removed, and the mixture stirred 2 h at
ambient temperature, then cooled again to 0 °C. 25 mL 0.1 N HCl (deoxygenated
water) was then added dropwise over 20 min, then 25 mL methyl tert-butyl ether
(MTBE) was added, and the mixture agitated well for 5 min. The upper organic
phase was decanted from the separator and saved. To the lower phase was then
added 20 mL of 1 N HCl (deoxygenated water) again, and it was extracted with
CH2Cl2 (2 9 30 mL). The organic phase was combined with the first organic phase,
then filtered through a celite pad, washing the pad with CH2Cl2, dried magnesium
sulfate (MgSO4), and the solvents removed in vacuo. The crude material was
123

Copper-catalyzed C–P cross-coupling of secondary…
chromatographed on silica gel eluting with 2% MeOH/CH2Cl2, then recrystallized
from hot ethyl acetate (EtOAc) to give 2.41 g of product (92%) as a colorless solid.
Colorless solid; Y = 92%; 1H NMR (400 MHz, CDCl3) d: 8.01 (d,
1JHP = 473 Hz, 1H), 7.60 (dd, J = 13.8, 8.2 Hz, 4H), 6.97 (dd, J = 7.8, 2.4 Hz,
4H), 3.83 (s, 6H); 31P NMR (162 MHz, CDCl3) d: 21.0.
Bis-(4-trifluoromethylphenyl)-phosphine oxide [79] The title compound was
prepared from 4-trifluoromethylphenylmagnesium bromide and diethylphosphite
by general procedure A. The crude material was dissolved in 10 mL of boiling
MTBE and allowed to cool to ambient temperature under Ar, with stirring, causing a
thick slurry to form. Hexane (20 ml) was slowly added to this slurry, stirred 10 min,
and filtered through a medium-fritted filter funnel, with a vigorous stream of N2
flowing over the filter cake. After 2 h, 2.81 g of the product (83%) was obtained as a
colorless solid.
Colorless solid; Y = 83%; 1H NMR (400 MHz, CDCl3) d: 8.22 (d,
1JHP = 493 Hz, 1H), 7.92–7.85 (m, 4H), 7.83–7.79 (m, 4H); 31P NMR (162 MHz,
CDCl3) d: 18.9; 19F NMR (282 MHz, CDCl3) d: -67.3.
Diphenyl-phosphine oxide [80] The title compound was prepared from phenyl-
magnesium bromide and diethylphosphite by general procedure A and chro-
matographed on silica gel eluting with 80:20 EtOAc-to-hexane to give 1.84 g of
product (91%) as a colorless solid after drying under high vacuum.
Colorless solid; Y = 91%; 1H NMR (400 MHz, CDCl3) d: 8.03 (d, 1JHP = 480 Hz,
1H), 7.69 (m, 4H), 7.54 (m, 2H), 7.47 (m, 4H); 31P NMR (162 MHz, CDCl3) d: 21.6.
Dicyclohexylphosphine oxide [81] The title compound was prepared from
cyclohexylmagnesium bromide and diethylphosphite by general procedure A. The
crude product was chromatographed on silica gel eluting with EtOAc to give an oil
which rapidly crystallized on standing to give 1.9 g of product (89%) as a colorless
solid.
Colorless solid; Y = 89%, 1H NMR (400 MHz, CDCl3) d: 6.32 (dt, JHP = 434 Hz,
JHH = 3.0 Hz, 1H), 2.00–1.24 (m, 22H), 31P NMR (162 MHz, CDCl3) d: 49.8.
General procedure B: non-symmetric secondary phosphine oxides
Cyclohexyl(tert-butyl)phosphine oxide Non-symmetric secondary phosphine oxi-
des were prepared by the addition of 1 eq. of ethylcyclohexylphosphinate [82] to
2.2 eq. of the corresponding Grignard reagent at 0 °C and warming to ambient
temperature, essentially following the procedure of Emmick [83]. A 100-mL 3-neck
flask fitted with an addition funnel was evacuated/Ar filled, then charged with
22 mL of 1 M tert-butylmagnesium chloride (t-BuMgCl)/ethyl ether (Et2O;
22 mmol, 2.2 eq.) in 10 mL of THF, then cooled to -10 °C under Ar in an ice/
salt bath. A solution of 1.76 g of ethylcyclohexylphosphinate (10 mmol, 1 eq.) in
123

C.-J. Li et al.
20 mL of THF was then added dropwise via an addition funnel over 10 min. The
bath was then removed, the mixture stirred 2 h at 25 °C, then cooled to 0 °C and
quenched by the dropwise addition of 20 mL of 1 N HCl (deoxygenated water) over
15 min. Et2O (20 mL ) was added, agitated 5 min, and then the upper organic phase
was decanted from the separator. To the lower phase was then added 20 mL of 1 N
HCl (deoxygenated water) again, and it was extracted with CH2Cl2 (2 9 30 mL).
The combined organics were filtered through a celite pad with washing the pad with
CH2Cl2, dried (MgSO4), and the solvents removed first under house vacuum, then
high vacuum to give 1.60 g of product (85%) as a colorless oil.
Colorless oil; Y = 85%.1H NMR (400 MHz, CDCl3) d: 6.50 (d, JHP = 456 Hz,
JHH = 3.6 Hz, 1H), 2.07–1.09 (m, 20H); 13C NMR (100 MHz, CDCl3) d: 33.5 (d,
J = 58 Hz), 29.4 (d, J = 64 Hz), 27.1 (d, J = 69 Hz), 25.8 (d, J = 6.4 Hz), 24.1,
23.4 (d, J = 3.2 Hz); 31P{1H} NMR (162 MHz, CDCl3) d: 56.4; anal. calcd. for
C10H21OP: C 63.80, H 11.24; found: C 63.87; H 11.29.
General procedure C: reduction of secondary phosphine oxides [84]
A 4-neck jacketed flask equipped with a bottom drain valve containing a 24/40 joint,
mechanical stirrer, addition funnel, and an argon sparge line was evacuated/Ar
filled, then charged with 15 mL of 1 M diisobutyl aluminium hydride (DIBAL-
H)/toluene (15.0 mmol, 3 eq.) through the addition funnel. THF (10 mL) was then
used to wash the walls of the addition funnel into the flask. The addition funnel was
then charged with a solution of secondary phosphine oxides (5.0 mmol, 1 eq.) in
20 mL of THF. This solution was then added dropwise over 10 min. THF (5 mL)
was then used to wash the walls of the addition funnel into the flask. The resulting
mixture was then stirred 2.0 h at ambient temperature, then 30 mL of MTBE was
added dropwise via an addition funnel over 5 min. After 5 min, the sparge line was
inserted beneath the solution surface and a slow argon flow was started and
maintained throughout all subsequent operations. After sparging for 10 min, the
mixture was cooled to an internal temperature of 5 °C. The addition funnel was then
charged with 20 mL of 2 N NaOH (deoxygenated water). This solution was then
added dropwise via an addition funnel over 10 min. Washing of the organic phase
with 15 mL of brine (deoxygenated water) was performed for 10 min. After 5 min,
the agitation was stopped, and the lower aqueous phase was drained to waste
through the bottom drain valve. Brine (30 mL 5% w/v, deoxygenated water) was
then added dropwise via an addition funnel over 10 min, and the lower aqueous
phase was again discarded to waste as described above. The resultant mixture was
then filtered through 5 mg of MgSO4. The pad (MgSO4) was then washed with
25 mL of MTBE which was added to the reactor and degassed by Ar sparging for
10 min. This solution was then used as a wash of the solids. The organic phase was
combined with the first organic phase and the solvents were removed in vacuo (kept
under argon). The crude material was chromatographed on silica gel to give the
product (kept under argon).
123

Copper-catalyzed C–P cross-coupling of secondary…
Bis-(4-methoxyphenyl)-phosphine [85] Colorless solid; Y = 90%; 1H NMR
(400 MHz, C6D6) d: 7.23 (t, J = 7.5 Hz, 4H), 6.56 (d, J = 8.3 Hz, 4H), 5.16 (d,
1JHP = 217 Hz, 1H), 3.12 (s, 6H); 31P NMR (162 MHz, C6D6) d: -30.8.
Bis-(4-(trifluoromethyl)phenyl)phosphine Colorless oil; Y = 87%; 1H NMR
(400 MHz, C6D6) d: 7.65 (d, J = 7.8 Hz, 4H), 7.43 (t, J = 7.4 Hz, 4H); 13C
NMR (100 MHz, CDCl3) d: 140.1 (d, J = 106 Hz), 134.2 (d, J = 20 Hz), 131.8 (dp,
J = 18 Hz, J = 2.8 Hz), 125.4 (d, J = 32 Hz), 123.2 (q, J = 272 Hz); 31P NMR
(162 MHz, C6D6) d: -26.8; 19F NMR (282 MHz, CDCl3) d: -68.1; anal. calcd. for
C14H9F6P: C 52.19, H 2.82; found: C 52.08; H 2.87.
1
Diphenylphosphine [86] Colorless oil; Y = 88%; H NMR (400 MHz, C6D6) d:
1
7.52–7.46 (m, 4H), 7.16–7.11 (m, 6H), 5.30 (d, JHP = 217 Hz, 1H); 31P NMR
(162 MHz, C6D6) d: -26.3.
Dicyclohexyl phosphine [87] Colorless oil; Y = 85%; 1H NMR (400 MHz, C6D6)
d: 3.01 (dt, 1JHP = 154 Hz, 3JHH = 4.4 Hz, 1H); 1.90–1.63 (m, 11H), 1.48–1.23 (m,
11H); 31P NMR (162 MHz, C6D6) d: -17.3.
Cyclohexyl(tert-butyl) phosphine Colorless oil; Y = 87%; 1H NMR (400 MHz,
1
3
C6D6) d: 3.13 (dt, JHP = 146 Hz, JHH = 3.8 Hz, 1H), 2.02–1.00 (m, 20H); 13C
NMR (100 MHz, CDCl3) d: 33.2 (d, J = 55 Hz), 28.7 (d, J = 20 Hz), 26.6 (d,
J = 19 Hz), 25.1 (d, J = 6.2 Hz), 24.0, 23.2 (d, J = 3.2 Hz); 31P NMR (162 MHz,
C6D6) d: -12.3; anal. calcd. for C10H21P: C 69.73, H 12.29; found: C 69.79; H
12.33.
General procedure D: phosphination of (hetero)aromatic bromide with secondary
phosphine
In an argon-filled glovebox, an oven-dried Schlenk tube equipped with a Teflon stir
bar was charged with CuI (9.5 mg, 0.05 mmol, 5 mol%) followed by anhydrous
toluene (2.0 ml), secondary phosphine (1.00 mmol), and L4 (49.54 mg, 0.30 mmol,
30 mol%). The solution was stirred for 5–10 min. Then the (hetero)aromatic
bromide (1.00 mmol) and KOtBu (224.42 mg, 2.0 mmol) were added at once
followed by anhydrous toluene/THF (0.5 mL/0.5 mL). The Schlenk tube was sealed
with a Teflon valve and the reaction mixture was stirred at 100 °C for 24 h. The
reaction mixture was then cooled to room temperature and filtered with
dichloromethane to remove any insoluble residues. The filtrate was concentrated
in vacuo; the residue was purified by flash chromatography on silica to obtain the
analytically pure product (kept under argon).
1-(Bis-(4-methoxyphenyl)phosphanyl)naphthalene (3a) White solid; Y = 93%;
1
(X = Br), Y = 95% (X = I); H NMR (400 MHz, CDCl3) d: 8.43–8.35 (m, 1 H),
7.84 (dd, J = 12.8, 8.2 Hz, 2 H), 7.52–7.39 (m, 2 H), 7.37–7.30 (m, 1 H), 7.26–7.08
(m, 8 H), 7.05–6.97 (m, 1 H), 3.81 (s, 6H); 13C NMR (100 MHz, CDCl3) d: 160.8
123

C.-J. Li et al.
(s), 137.8 (d, J = 26.8 Hz), 136.7 (d, J = 20.8 Hz), 131.9, 128.7 (d, J = 17.4 Hz),
127.3 (d, J = 1.8 Hz), 126.8 (d, J = 6.3 Hz), 125.7 (d, J = 3.2 Hz), 125.7 (d,
J = 3.2 Hz), 122.5 (d, J = 2.1 Hz), 114.7 (d, J = 19.2 Hz), 113.8 (d, J = 7.8 Hz),
113.1, 54.6 (s); 31P NMR (162 MHz, CDCl3) d: -16.4; anal. calcd. for
C24H21O2P: C 77.41, H 5.68; found: C 77.48, H 5.76.
2-(Bis-(4-methoxyphenyl)phosphanyl)nicotinonitrile (3b) White solid; Y = 79%;
1H NMR (400 MHz, CDCl3) d: 8.57 (d, J = 4.8 Hz, 1 H), 7.83 (d, J = 7.8 Hz, 1 H),
7.58 (dd, J = 8.7, 6.9 Hz, 4 H), 7.16–7.08 (m, 5 H), 3.80 (s, 6H); 13C NMR
(100 MHz, CDCl3) d: 162.4 (d, J = 15.8 Hz), 160.6, 150.1 (d, J = 6.2 Hz), 138.5
(d, J = 21.0 Hz), 134.8 (d, J = 8.4 Hz), 128.2 (d, J = 19.8 Hz), 122.8, 113.6 (d,
J = 8.8 Hz), 117.8, 112.8 (d, J = 19.0 Hz), 55.8; 31P NMR (162 MHz, CDCl3) d:
-15.7; anal. calcd. for C20H17N2O2P: C 68.96, H 4.92, N 8.04; found: C 68.92, H
4.99, N 8.11.
Biphenyl-2-yl-bis-(4-methoxyphenyl)-phosphane (3c) White solid; Y = 88%
(X = Br); Y = 91% (X = I); 1H NMR (400 MHz, CDCl3) d: 7.43 (t, J = 7 Hz,
1H), 7.34–7.08 (m, 16H), 3.83 (s, 6H); 13C NMR (100 MHz, CDCl3) d: 160.7, 148.8
(d, J = 28 Hz), 142.4 (d, J = 7 Hz), 136.5 (d, J = 14 Hz), 134, 8 (d, J = 12 Hz),
134.5, 134.3 (d, J = 22 Hz), 130.6 (d, J = 5.2 Hz), 130.1 (d, J = 3.6 Hz), 129.7 (d,
J = 6.8 Hz), 128.9, 127.8, 127.6 (d, J = 15.2 Hz), 127.6, 55.7; 31P NMR (162 MHz,
CDCl3) d: -14.6; anal. calcd. for C26H23O2P: C 78.38, H 5.82; found: C 78.45, H
5.89.
3-(Diphenylphosphanyl)pyridine (3d) [88] White solid; Y = 81%; 1H NMR
(400 MHz, CDCl3) d: 8.59 (d, J = 4.7 Hz, 1H), 8.54 (s, 1 H), 7.62–7.55 (m, 1
H), 7.43–7.34 (m, 10 H), 7.30–7.25 (m, 1 H); 31P NMR (162 MHz, CDCl3) d:
-12.1.
1
(4-Methoxyphenyl)diphenylphosphane (3e) [88] White solid; Y = 90%; H NMR
(400 MHz, CDCl3) d: 7.37–7.28 (m, 12 H), 6.92 (d, J = 7.6 Hz, 2 H), 3.80 (s, 3 H);
31P NMR (162 MHz, CDCl3) d: -7.3.
4-(Diphenylphosphanyl)benzoic acid ethyl ester (3f) [89] White solid; Y = 77%;
1H NMR (400 MHz, CDCl3) d: 8.02 (d, J = 7.8 Hz, 2H), 7.42–736 (m, 12H), 4.36
(q, J = 7.3 Hz, 2H), 1.38 (t, J = 6.8 Hz, 2H); 31P NMR (162 MHz, CDCl3) d: -4.8.
1
4-(Diphenylphosphanyl)benzonitrile (3g) [90] White solid; Y = 79%; H NMR
(400 MHz, CDCl3) d: 7.57 (d, J = 6.9 Hz, 2H), 7.38–7.30 (m, 12H); 31P NMR
(162 MHz, CDCl3) d: -4.8.
(2-Chlorophenyl)-di-(4-trifluoromethylphenyl)phosphane
(3h) White
solid;
1
Y = 79%; H NMR (400 MHz, CDCl3) d: 7.57–7.46 (m, 4H), 7.43 (t, J = 7.2 Hz,
2H), 7.40–7.21 (m, 4H), 6.90 (t, J = 7.3 Hz, 1H), 6.81 (t, J = 7.6 Hz, 1H); 13C
NMR (100 MHz, CDCl3) d: 143.9 (s, J = 14.6 Hz), 142.7 (d, J = 26 Hz), 135.8 (d,
123

Copper-catalyzed C–P cross-coupling of secondary…
J = 25 Hz), 134.8, 133.8 (d, J = 3.2 Hz), 132.4 (d, J = 18 Hz), 131.9 (s, J = 3 Hz),
130.4, 130.2, 126.1, 123.6 (s, J = 270 Hz), 125.8, 124.3; 31P NMR (162 MHz,
CDCl3) d: -12.1; 19F NMR (282 MHz, CDCl3) d: -58.6; anal. calcd. for
C20H12ClF6P: C 55.51, H 2.80; found: C 55.59, H 2.84.
(2-Iodophenyl)-di-(4-trifluoromethylphenyl)phosphane (3i) White solid; Y = 38%;
1H NMR (400 MHz, CDCl3) d: 7.62–7.53 (m, 4H), 7.51 (dd, J = 30 Hz,
J = 8.1 Hz, 1H), 7.45 (m, 2H), 7.41–7.34 (m, 2H), 7.28 (m, 1H), 6.91 (t,
J = 7.6 Hz, 1H), 6.74 (t, J = 7.8 Hz, 1H); 13C NMR (100 MHz, CDCl3) d: 140.2 (s,
J = 15 Hz), 137.8 (d, J = 24 Hz), 135.6, 134.6 (d, J = 30 Hz), 134.3 (d,
J = 3.2 Hz), 134.1 (d, J = 20 Hz), 132.8 (d, J = 17.8 Hz), 134.3 (d, J = 22 Hz),
131.8 (s, J = 30 Hz), 131.1, 127.4, 126.0, 124.5, 123.7 (s, J = 270 Hz); 31P NMR
(162 MHz, CDCl3) d: -16.1; 19F NMR (282 MHz, CDCl3) d: -58.8; anal. calcd.
for C20H12F6IP: C 45.83, H 2.31; found: C 45.87, H 2.33.
(2-Bromophenyl)-di-(4-trifluoromethylphenyl)phosphane (3i–1) White solid;
1
Y = 42%; H NMR (400 MHz, CDCl3) d: 7.62–7.54 m, 5H), 7.42 (t, J = 7.4 Hz,
2H), 7.39–7.34 (m, 2H), 7.25 (d, J = 7.6 Hz, 1H), 6.95 (t, J = 7.4 Hz, 1H), 6.72 (t,
J = 7.6 Hz, 1H); 13C NMR (100 MHz, CDCl3) d: 140.1 (s, J = 14 Hz), 137.9 (d,
J = 25 Hz), 135.1, 134.7 (d, J = 32 Hz), 134.2 (d, J = 3 Hz), 134.0 (d, J = 20 Hz),
132.6 (d, J = 18 Hz), 131.8 (s, J = 39 Hz), 131.0, 127.2, 125.8, 124.1, 123.6 (s,
J = 271 Hz); 31P NMR (162 MHz, CDCl3) d: -12.5; 19F NMR (282 MHz, CDCl3)
d: -58.9; anal. calcd. for C20H12BrF6P: C 50.34, H 2.53; found: C 50.40, H 2.59.
3-(Dicyclohexylphosphanyl)benzonitrile (3j) [91] White solid; Y = 81% (X = Br);
1
Y = 83% (X = I); H NMR (400 MHz, CDCl3) d: 7.74 (t, J = 5.4 Hz, 1H), 7.39 (t,
J = 6.6 Hz, 1H), 7.03 (d, J = 7.6 Hz, 1H), 6.83 (t, J = 7.6 Hz, 1H), 1.87–0.94 (m,
22 H); 31P NMR (162 MHz, CDCl3) d:4.7.
2-(Dicyclohexylphosphanyl)-N,N-dimethylbenzamide (3k) White solid; Y = 78%
1
(X = Br); Y = 84% (X = I); H NMR (400 MHz, CDCl3) d: 7.53 (d, J = 8.1 Hz,
1H), 7.35–7.30 (m, 2 H), 7.23 (d, J = 7.7 Hz, 1H), 3.70–3.66 (m, 1H),
d = 3.47–3.44 (m, 1H), 3.12–3.09 (m, 2 H), 2.14–2.10 (m, 1H), 1.86–1.01 (m,
23H); 13C NMR (100 MHz, CDCl3) d: 170.4 (d, J = 4.2 Hz), 147.5 (d,
J = 34.7 Hz), 132.9 (d, J = 10.6 Hz), 132.5 (d, J = 2.0 Hz), 127.8, 127.1 (d,
J = 3.9 Hz), 125.8 (d, J = 8.8 Hz), 38.8, 38.6, 33.1 (d, J = 11.7 Hz), 30.8 (d,
J = 14.2 Hz), 30.6 (d, J = 14.5 Hz), 29.4 (d, J = 10.3 Hz), 28.1 (d, J = 7.8 Hz),
28.0; 31P NMR (162 MHz, CDCl3) d: -6.9; anal. calcd. for C21H32NOP: C 73.01,
H 9.34; found: C 73.10, H 9.38.
Tert-butyl-cyclohexylphenylphosphane (3l) Colorless oil; Y = 77%; 1H NMR
(400 MHz, CDCl3) d: 7.44–7.37 (m, 2H), 7.28–7.14 (m, 3H), 2.09–1.10 (m,
20H); 13C NMR (100 MHz, CDCl3) d: 136.7 (d, J = 18 Hz), 133.6 (d, J = 20 Hz),
128.6, 126.1 (d, J = 2.4 Hz), 35.3 (d, J = 8.3 Hz), 31.3 (d, J = 22.4 Hz), 30.8 (d,
J = 15.4 Hz), 29.6 (d, J = 15.0 Hz), 28.3, 26.8 (d, J = 10.6 Hz); 31P NMR
123

C.-J. Li et al.
(162 MHz, CDCl3) d: 2.8; anal. calcd. for C16H25P: C 77.38, H 10.15; found: C
77.43, H 10.19.
Tert-butyl-cyclohexyl-(3,5-dimethyl-phenyl)phosphane
(3m) Colorless
oil;
1
Y = 78%; H NMR (400 MHz, CDCl3) d: 7.32 (d, J = 7.2 Hz, 2H), 6.81 (s, 1H),
2.18 (s, 6H), 1.97–1.01 (m, 20H); 13C NMR (100 MHz, CDCl3) d: 137.9 (d,
J = 7.6 Hz), 136.1 (d, J = 18 Hz), 133.7 (d, J = 21 Hz), 131.8, 33.8 (d,
J = 14.6 Hz), 32.1 (d, J = 25.0 Hz), 30.5 (d, J = 14.8 Hz), 28.1 (d, J = 11.4 Hz),
27.9 (d, J = 7.2 Hz), 27.4, 21.9, 20.5 (d, J = 14.8 Hz); 31P NMR (162 MHz,
CDCl3) d: 3.4; anal. calcd. for C18H29P: C 78.22, H 10.58; found: C 78.25, H
10.63.
Tert-butyl-cyclohexyl-(4-trifluoromethylphenyl)phosphane (3n) Colorless oil;
Y = 75%; 1H NMR (400 MHz, CDCl3) d: 7.63 (d, J = 8.2 Hz, 2H), 7.42 (t,
J = 7.8 Hz, 2H), 2.01–1.05 (m, 20H); 13C NMR (100 MHz, CDCl3) d: 140.0 (d,
J = 14 Hz), 134.1 (d, J = 22 Hz), 131.8 (s, J = 31 Hz), 125.7, 123.6 (s,
J = 273 Hz), 33.5 (d, J = 14 Hz), 33.3 (d, J = 24.6 Hz), 27.9 (d, J = 12 Hz),
27.8 (d, J = 7.1 Hz), 27.2, 21.7 (d, J = 15.8 Hz); 31P NMR (162 MHz, CDCl3) d:
3.9; 19F NMR (282 MHz, CDCl3) d: -58.7; anal. calcd. for C17H24F3P: C 64.54,
H 7.65; found: C 64.61, H 7.69.
Acknowledgements The authors gratefully acknowledge the financial support from Hebei Chemical and
Pharmaceutical College. The authors are thankful to Hebei University of Science and Technology for
1
elemental, 13C NMR, H NMR, 19F NMR, and 31P NMR analysis.
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