Palladium-catalyzed phosphorylation of benzyl ammonium triflates with P(O)H compounds

Article abstract of DOI:10.1016/j.tet.2020.131020

A palladium-catalyzed phosphorylation of benzyl ammonium triflates with P(O)H compounds has been developed. Various benzylphosphorus compounds were produced in good to excellent yields with high functional group tolerance. All the three kinds of hydrogen phosphoryl compounds, i.e. H-phosphonates, H-phosphinates and secondary phosphine oxides, were applicable to this reaction. The successful scale-up experiment and one-pot synthetic operation also well demonstrated its practicality.

Full text of DOI:10.1016/j.tet.2020.131020

Journal Pre-proof
Palladium-catalyzed phosphorylation of benzyl ammonium triflates with P(O)H
compounds
Long Liu, Kaiqiang Xu, Yuan Wang, Wenqi Wang, Hanshuang Xu, Tianzeng Huang,
Tieqiao Chen
PII:
S0040-4020(20)30122-8
https://doi.org/10.1016/j.tet.2020.131020
TET 131020
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 9 December 2019
Revised Date: 9 January 2020
Accepted Date: 3 February 2020
Please cite this article as: Liu L, Xu K, Wang Y, Wang W, Xu H, Huang T, Chen T, Palladium-catalyzed
phosphorylation of benzyl ammonium triflates with P(O)H compounds, Tetrahedron (2020), doi: https://
doi.org/10.1016/j.tet.2020.131020.
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Palladium-catalyzed phosphorylation of benzyl ammonium
triflates with P(O)H compounds
Long Liu,a Kaiqiang Xu,a Yuan Wang,a Wenqi Wang,a Hanshuang Xu,a Tianzeng
Huang,a Tieqiao Chen*a
aKey Laboratory of Ministry of Education for Advanced Materials in Tropical Island Resources,
Hainan Provincial Key Lab of Fine Chem, Hainan University, Haikou, 570228, China.
Email: chentieqiao@hnu.edu.cn
Abstract:
A palladium-catalyzed phosphorylation of benzyl ammonium triflates with P(O)H
compounds has been developed. Various benzylphosphorus compounds were
produced in good to excellent yields with high functional group tolerance. All the
three kinds of hydrogen phosphoryl compounds, i.e. H-phosphonates, H-phosphinates
and secondary phosphine oxides, were applicable to this reaction. The succesful
scale-up experiment and one-pot synthetic operation also well demonstrated its
practicality.
Keywords: Palladium catalysis; Benzyl ammonium triflates; Phosphorylation;
Benzylphosphorus compounds.
Introduction
1

Benzylphosphorus compounds are a kind of important synthetic intermediates,
for example, for synthesis of alkenes [1]. They also found wide application in
medicinal chemistry and material chemistry [2]. Traditional methods for their
preparation relied on nucleophilic substitutions of P(O)X compounds with benzyl
metals (Li or Mg) and Michaelis-Arbuzov reactions of benzyl halides with phosphites
[3], suffering from harsh conditions, poor functional group tolerance, and high
toxicity of reagents. In 1980s, Hirao developed a mild Pd-catalyzed cross coupling
between aryl halides and P(O)H compounds, which has become a powerful method
for constructing C-P bonds [4]. This strategy was also applicable to produce benzyl
phosphorus compounds using benzyl halides [5]. Recently, new methods using more
available and abundant compounds such as benzyl nitriles, benzyl alcohols and benzyl
esters etc. instead of benzyl halides to couple with P(O)H compounds have also been
developed [6-9].
Benzyl ammonium triflates are readily accessible amine derivatives. In the last
decades, they acted as an excellent benzyl source and were applied in a series of C-C
and C-heteroatom (C-B, C-S) bonds forming reactions [10,11]. Recently, Wang
reported an Ni-catalyzed cross coupling of aryl, benzyl, and allylammonium salts with
P(O)H compounds [12]. It is a very good method for the phosphorylation of aryl and
allyl ammonium salts. However, it seems not efficient enough for the synthesis of
benzyl phosphorus compounds, especially for the non-π-extended ones. The yields
usually were less than 60%. Probably due to the strong ability of oxidative addition of
nickel, substrate bearing CAr-Cl bonds gave a low yield (21% yield). In addition, only
2

Ph2P(O)H was demonstrated in the phosphorylation of benzyl ammonium salts.
Herein, we report a Pd-catalyzed version with a good complementary reactivity,
providing an efficient access to benzyl phosphorus compounds (Scheme 1).
Scheme 1 Pd-catalyzed phosphorylation of benzyl ammonium triflates
Results and discussion
Initially, the reaction of benzyltrimethylammonium triflate (1a, 0.2 mmol) and
diisopropyl phosphite (2a, 1.2 equiv.) was examined in the presence of Pd(OAc)2 (3
mol%), DPPB (4 mol%) and Na2CO3 (2.0 equiv.). After heating the mixture at 110 oC
in dioxane for 4 h, the phosphorylated product 3a was obtained in 81% GC yield
(Table 1, entry 1). Common Pd(II) catalysts such as PdCl2, Pd(acac)2 and Pd(OTFA)2
were tested, however, no better results were observed (Table 1, entries 2-4). Pd(dba)2
could also mediate the reaction, giving 3a in 54% yield (Table 1, entry 5).[13] It
should be noted that no reaction occurred in the absence of palladium catalyst,
excluding the possibility that this transformation proceeded through base-promoted
nucleophilic substitution (Table 1, entry 6). The phosphine ligand played an important
role; no 3a was detected without addition of phosphine ligands (Table 1, entry 7).
Among the monodentate and bisdentate phosphine ligands investigated, DPPF was
the best choice, leading to 3a in 90% yield (Table 1, entries 8-13). A variety of bases
were subsequently screened. Cs2CO3, K3PO4 and K2CO3 could also effectively
promote this reaction with K2CO3 being the best one (Table 1, entries 14-16).
3

Table 1. Optimization of the reaction conditions.a
[a] Reaction conditions: 1a (0.2 mmol), 2a (1.2 equiv), catalyst (3 mol%), ligand (4 mol%), base
(2.0 equiv.), solvent (2.0 mL), N2, 110 °C, 4 h. [b] GC yield using dodecane as an internal
standard. [c] Ligand (8 mol%). [d] K2CO3 (1.0 equiv.). [e] 100 °C. [f] 80 °C.
4

Probably because of the hydrolysing decomposition of H-phosphonate under the
strong alkaline conditions, only 6% yield of 3a was obtained with NaOtBu (Table 1,
entry 17). Reducing the loading of K2CO3 to 1.0 equiv led to decrease of the yield;
while no 3a was detected in the absence of any base (Table 1, entries 18 and 19). This
C-P bond-forming reaction also took place in other solvents such as THF, toluene,
cyclohexane, CH3CN or DMF, though slightly lower yields of 3a were given (Table 1,
entries 16, 20-24). Final investigation of reaction temperature showed that this
o
reaction could efficiently proceeded at 100 C, while further lowering the reaction
temperature would reduce the yield of 3a (Table 1, entries 25 and 26).
With the optimized conditions in hand, substrate scope for both P(O)H
compounds and benzyl ammonium triflates was investigated to probe the versatility of
this new catalytic reaction (Table 2). In addition to diisopropyl phosphite converted
into 3a in 91% isolated yield, other H-phosphonates like diethyl phosphite and dibutyl
phosphite were also applicable to this reaction, producing the corresponding products
in 90% and 94% yields, respectively (3b and 3c). H-Phosphinates also proved to be
good substrates, exemplified by ethyl phenylphosphinate giving 3d in 95% yield.
Secondary phosphine oxides with aryl groups also showed high reactivity to couple
with 1a, furnishing the expected coupling products in 91-94% yields (3e-g). However,
when dibutylphosphine oxide was used, low yield of 3h was obtained under the
reaction conditions.
Subsequently, the scope of benzyltrimethylammonium triflates was examined.
Substrates bearing electron-donating groups such as OMe, Me, and tBu at the benzene
5

ring coupled readily with Ph2P(O)H, producing the corresponding coupling products
in good to high yields (3i-m). Condensed nucleus compounds like the
oxygen-containing heterocycle 3n and naphthyl products 3o could also be obtained in
95 and 74% yields, respectively. Worth noting is that the vinyl group, which is easy
Table 2. Substrate scope.a
[a] Reaction conditions: 1 (0.2 mmol), 2 (1.2 equiv), Pd(OAc)2 (3 mol%), DPPF (4 mol%), K2CO3
(2.0 equiv.), dioxane (2.0 mL), N2, 100 °C, 4 h. Isolated yield. [b] GC yield.
6

to react with P(O)H compounds and polymerize by heating [14], survived well under
the reaction conditions, exemplified by 3p which was obtained in 69% yield.
Derivatives bearing electron withdrawing groups such as –F, -CN and –CF3 at the
benzene ring presented high reactivity, generating the corresponding
organophosphorus products in 80-91% yields (3q-s). Unlike the reported Ni-catalyzed
system, this Pd-catalyzed system had a good compatibility to CAr–Cl bonds. Both
mono- and dichloro substituted benzyl ammonium salts reacted with Ph2P(O)H
regioselectively, giving the C-N bond-phosphorylated products in high yields (3s-v,
83-88% yields). However, the more active CAr–Br bond could not survive under the
reaction conditions (not shown). Substrates bearing substituent at the benzyl site were
also unworkable, When PhCH(Me)NMe3OTf was allowed to react with HP(O)Ph2
under the optimized conditions, only a trace amount of desired product 3w was
obtained, the main product was phenylethylene which was generated through
β-elimination.
Scheme 2 Scale up and one-pot synthesis.
Pd(OAc)2 (3 mol%)
DPPF (4 mol%)
P(O)(OiPr)2
+
(1)
(2)
Ph
1a (10 mmol)
NMe3OTf
HP(O)(OiPr)2
Ph
K2CO3 (2.0 equiv.)
dioxane (20 mL)
100 oC, 10 h
2a (1.2 equiv.)
3a, 85% (2.18 g)
2a (1.2 equiv.)
MeOTf (1.2 equiv.)
dioxane (2.0 mL)
r.t., 30 min
3a
Ph
NMe2
Ph
NMe3OTf
Optimized
conditions
90%
1A (0.2 mmol)
1a (not isolated)
7

In order to further explore the potential use of this transformation, a scale-up
reaction to 10 mmol scale was performed and an acceptable yield of 3a (85%, 2.18 g)
was obtained (Scheme 2, eq 1). In addition, without isolation of 1a, the one-pot
synthetic operation starting from N,N-dimethylbenzylamine (1A) was successfully
achieved to produce 3a in 90% yield, providing a more convenient access for
converting organic amines into organophosphorus compounds (Scheme 2, eq 2).
On the basis of previous literatures [10-12, 15], a plausible reaction mechanism
was proposed. As shown in Scheme 3, Pd(0) complex firstly added to
benzyltrimethylammonium triflates to afford speceis I with release of NMe3. In the
presence of a base, I subsequently underwent ligand exchange with P(O)H
compounds, generating the intermediate II. Reductive elimination of II produced the
target benzyl phosphorus compounds and regenerated the Pd(0) complex to complete
the catalytic cycle.
Scheme 3 Plausible reaction mechanism.
Conclusions
8

In conclusion, we have developed an efficient Pd-catalyzed C-P bond forming
reaction through phosphorylation of the readily accessible benzyl ammonium triflates.
The reaction allowed all the three kinds of hydrogen phosphoryl compounds to couple
with benzyl ammonium salts bearing various functional groups, producing the
corresponding benzylphosphorus compounds in good to excellent yields. Gram-scale
reaction and one-pot synthetic experiment starting from amines were successfully
operated, which not only provide an efficient method for synthesis of
benzylphosphorus compounds, but also enriches the application of amines as synthon
in organic chemistry.
Acknowledgements
This work is supported by the NSF of Hainan Province (Grant No. 219MS005) and
the National NSF of China (Grant Nos. 21871070). Hainan University start-up funds
(KYQD(ZR)1854 and KYQD(ZR)1857) are also appreciated.
Experimental section
General Information
The reactions were carried out in schlenk tubes of 25 mL under N2 atmosphere.
Reagents were used as received unless otherwise noted, and solvents were purified
according to standard operation procedure. Column chromatography was performed
using Silica Gel 60 (300‒400 mesh). The reactions were monitored by GC and
GC-MS, GC-MS results were recorded on GC-MS QP 2010, and GC analysis was
9

performed on GC 2014. The 1H, 13C and 31P NMR spectra were recorded on a Brucker
ADVANCE III spectrometer at 400 MHz, 100 MHz and 162 MHz respectively, and
chemical shifts were reported in parts per million (ppm). The HR-MS was obtained
using a Q-TOF instrument equipped with ESI source, and the mass analyzer type is
TOF for EI. All solvents and reagents were purchased from Tansoole, Meryer,
Heowns, Energy Chemical, Alfa Aesar, and Aladdin.
Experimental Procedure
In an oven dried 25 mL Schlenk tube was charged with benzyl ammonium
triflates 1 (0.2 mmol), P(O)H compounds 2 (0.24 mmol, if it is liquid, add it after
charging N2), Pd(OAc)2 (0.006 mmol, 3 mol %), DPPF (0.008 mmol, 4 mol %) and
K2CO3 (0.4 mmol, 2.0 equiv), after charging N2 for three times, dioxane (2.0 mL) was
added. The reaction mixture was reacted at 100 °C for 4 h. After completion of the
reaction, the reaction mixture was concentrated under vacuum. The desired product
was isolated by column chromatography over silica gel (300-400 mesh) using
petroleum ether-ethyl acetate as eluent.
Diisopropyl benzylphosphonate (3a)
The title compound was prepared according to the general experimental procedure
and purified by column chromatography on silica gel and eluted with petroleum ether:
1
ethyl acetate = 2:1 (v:v) to afford a colorless oil in 91% yield (46.6 mg). H NMR
(400 M, CDCl3): δ 7.30–7.28 (m, 4H), 7.25–7.21 (m, 1H), 4.63–4.56 (m, 2H), 3.11 (d,
10

13
J = 17.2 Hz, 2H), 1.27 (d, J = 4.8 Hz, 6H), 1.16 (d, J = 5.2 Hz, 6H). C NMR (100
MHz, CDCl3): δ 131.7 (d, JC-P = 8.9 Hz), 129.6 (d, JC-P = 6.6 Hz), 128.1 (d, JC-P = 2.9
Hz), 126.5 (d, JC-P = 3.5 Hz), 70.3 (d, JC-P = 6.9 Hz), 34.5 (d, JC-P = 138.8 Hz), 23.7 (d,
JC-P = 27.9 Hz).; 31P NMR (162 MHz, CDCl3): δ 24.6. This compound is known [3e],
CAS number: 1083-98-3.
Diethyl benzylphosphonate (3b)
The title compound was prepared according to the general experimental procedure
and purified by column chromatography on silica gel and eluted with petroleum ether:
1
ethyl acetate = 2:1 (v:v) to afford a colorless oil in 90% yield (41.1 mg). H NMR
(400 M, CDCl3): δ 7.32–7.28 (m, 4H), 7.26–7.22 (m, 1H), 4.06–3.95 (m, 4H), 3.15 (d,
J = 17.2 Hz, 2H), 1.23 (t, J = 5.8 Hz, 6H).; 13C NMR (100 MHz, CDCl3): 131.4 (d,
JC-P = 7.3 Hz), 129.6 (d, JC-P = 5.3 Hz), 128.4 (d, JC-P = 2.4 Hz), 126.7 (d, JC-P = 2.8
31
Hz), 62.0 (d, JC-P = 5.4 Hz), 33.6 (d, JC-P = 109.9 Hz), 16.2 (d, JC-P = 4.8 Hz).; P
NMR (162 MHz, CDCl3): δ 26.5. This compound is known [3e], CAS number:
1080-32-6.
Dibutyl benzylphosphonate (3c)
The title compound was prepared according to the general experimental procedure
and purified by column chromatography on silica gel and eluted with petroleum ether:
1
ethyl acetate = 2:1 (v:v) to afford a colorless oil in 94% yield (53.4 mg). H NMR
(400 M, CDCl3): δ 7.31–7.28 (m, 4H), 7.25–7.21 (m, 1H), 3.98–3.89 (m, 4H), 3.15 (d,
11

J = 17.2 Hz, 2H), 1.58–1.53 (m, 4H), 1.36–1.29 (m, 4H), 0.89 (t, J = 5.8 Hz, 6H).; 13C
NMR (100 MHz, CDCl3): 131.4 (d, JC-P = 7.3 Hz), 129.6 (d, JC-P = 5.2 Hz), 128.3 (d,
JC-P = 2.4 Hz), 126.6 (d, JC-P = 2.9 Hz), 65.6 (d, JC-P = 5.5 Hz), 33.4 (d, JC-P = 110.0
31
Hz), 32.3 (d, JC-P = 4.8 Hz), 18.5, 13.4.; P NMR (162 MHz, CDCl3): δ 26.4. This
compound is known [9a], CAS number: 3762-27-4.
Ethyl benzyl(phenyl)phosphinate (3d)
The title compound was prepared according to the general experimental procedure
and purified by column chromatography on silica gel and eluted with petroleum ether:
1
ethyl acetate = 2:1 (v:v) to afford a colorless oil in 95% yield (49.4 mg). H NMR
(400 M, CDCl3): δ 7.55–7.50 (m, 2H), 7.45–7.40 (m, 1H), 7.34–7.29 (m, 2H),
7.14–7.10 (m, 3H), 7.02–6.99 (m, 2H), 4.05–3.95 (m, 1H), 3.86–3.76 (m, 1H), 3.21 (d,
J = 18.0 Hz, 2H), 1.20 (t, J = 7.2 Hz, 3H).; 13C NMR (100 MHz, CDCl3): 132.2 (d,
JC-P = 2.8 Hz), 131.9 (d, JC-P = 9.5 Hz), 131.4 (d, JC-P = 7.6 Hz), 130.1 (d, JC-P = 124.9
Hz), 129.9 (d, JC-P = 5.7 Hz), 128.3 (d, JC-P = 9.4 Hz), 128.2 (d, JC-P = 6.0 Hz), 126.6
(d, JC-P = 3.5 Hz), 60.9 (d, JC-P = 6.6 Hz), 38.1 (d, JC-P = 94.8 Hz), 16.4 (d, JC-P = 6.4
Hz).; 31P NMR (162 MHz, CDCl3): δ 39.9. This compound is known [9a], CAS
number: 2129-79-5.
Benzyldiphenylphosphine oxide (3e)
The title compound was prepared according to the general experimental procedure
and purified by column chromatography on silica gel and eluted with petroleum ether:
12

ethyl acetate = 1:1 (v:v) to afford a white solid in 91% yield (53.2 mg). 1H NMR (400
M, CDCl3): δ 7.71–7.67 (m, 4H), 7.52–7.49 (m, 2H), 7.43–7.42 (m, 4H), 7.18–7.17
(m, 3H), 7.12–7.10 (m, 2H), 3.65 (d, J = 13.2 Hz, 2H).; 13C NMR (100 MHz, CDCl3):
132.3 (d, JC-P = 78.7 Hz), 131.7 (d, JC-P = 2.1 Hz), 131.1 (d, JC-P = 7.3 Hz), 130.1 (d,
JC-P = 4.1 Hz), 128.4 (d, JC-P = 9.3 Hz), 128.3 (d, JC-P = 1.9 Hz), 126.7 (d, JC-P = 2.4
Hz), 38.1 (d, JC-P = 53.0 Hz).; 31P NMR (162 MHz, CDCl3): δ 29.4. This compound is
known [3e], CAS number: 2959-74-2.
Benzyl di-p-tolylphosphine oxide (3f)
The title compound was prepared according to the general experimental procedure
and purified by column chromatography on silica gel and eluted with petroleum ether:
ethyl acetate = 1:1 (v:v) to afford a white solid in 94% yield (60.2 mg). 1H NMR (400
M, CDCl3): δ 7.50–7.45 (m, 4H), 7.14–7.07 (m, 7H), 7.03–7.01 (m, 2H), 3.52 (d, J =
13.6 Hz, 2H), 2.27 (s, 6H).; 13C NMR (100 MHz, CDCl3): 141.9 (d, JC-P = 2.8 Hz),
131.9 (d, JC-P = 10.2 Hz), 131.4 (d, JC-P = 7.8 Hz), 131.0 (d, JC-P = 9.4 Hz), 130.0 (d,
JC-P = 5.2 Hz), 129.1 (d, JC-P = 102.8 Hz), 129.0 (d, JC-P = 12.0 Hz), 128.2 (d, JC-P
=
2.5 Hz), 126.5 (d, JC-P = 3.0 Hz), 38.1 (d, JC-P = 66.3 Hz), 21.0 (d, JC-P = 0.6 Hz).; 31P
NMR (162 MHz, CDCl3): δ 29.7. This compound is known [16], CAS number:
54441-76-8.
Benzyl(butyl)(phenyl)phosphine oxide (3g)
The title compound was prepared according to the general experimental procedure
13

and purified by column chromatography on silica gel and eluted with petroleum ether:
ethyl acetate = 1:1 (v:v) to afford a white solid in 93% yield (50.6 mg), m.p.
o
1
102.0-104.0 C. H NMR (400 M, CDCl3): δ 7.53–7.48 (m, 2H), 7.46–7.42 (m, 1H),
7.38–7.36 (m, 2H), 7.20–7.10 (m, 3H), 7.02–7.00 (m, 2H), 3.30–3.18 (m, 2H),
1.95–1.74 (m, 2H), 1.58–1.48 (m, 1H), 1.38–1.22 (m, 3H), 0.77 (t, J = 7.2 Hz, 2H);
13C NMR (100 MHz, CDCl3): 131.8 (d, JC-P = 7.2 Hz), 131.7 (d, JC-P = 92.5 Hz),
131.6 (d, JC-P = 2.7 Hz), 130.7 (d, JC-P = 8.6 Hz), 130.0 (d, JC-P = 5.0 Hz), 128.5 (d,
JC-P = 2.6 Hz), 128.4 (d, JC-P = 11.0 Hz), 126.7 (d, JC-P = 2.9 Hz), 38.9(d, JC-P = 61.9
Hz), 27.9 (d, JC-P = 69.1 Hz), 24.0 (d, JC-P = 14.5 Hz), 23.2 (d, JC-P = 4.2 Hz), 13.5.;
31P NMR (162 MHz, CDCl3): δ 38.1. HRMS (ESI) m/z: [M + H]+ calcd. for
C17H21OP: 273.1408, found: 273.1405.
(4-Methoxybenzyl)diphenylphosphine oxide (3i)
The title compound was prepared according to the general experimental procedure
and purified by column chromatography on silica gel and eluted with petroleum ether:
ethyl acetate = 1:1 (v:v) to afford a white solid in 89% yield (57.4 mg). 1H NMR (400
M, CDCl3): δ 7.64–7.59 (m, 4H), 7.45–7.41 (m, 2H), 7.38–7.33 (m, 4H), 6.96–6.93
(m, 2H), 6.65 (d, J = 8.8 Hz, 2H), 3.66 (s, 3H), 3.52 (d, J = 13.2 Hz, 2H).; 13C NMR
(100 MHz, CDCl3): 158.5 (d, JC-P = 2.8 Hz), 132.3 (d, JC-P = 98.0 Hz), 131.7 (d, JC-P
= 2.6 Hz), 131.1 (d, JC-P = 8.9 Hz), 131.0 (d, JC-P = 5.3 Hz), 128.4 (d, JC-P = 12.5 Hz),
31
122.8 (d, JC-P = 8.0 Hz), 113.8 (d, JC-P = 2.4 Hz), 55.1, 37.1 (d, JC-P = 67.1 Hz).; P
NMR (162 MHz, CDCl3): δ 29.6. This compound is known [3e], CAS number:
14

16114-90-2.
(4-Methylbenzyl)diphenylphosphine oxide (3j)
The title compound was prepared according to the general experimental procedure
and purified by column chromatography on silica gel and eluted with petroleum ether:
ethyl acetate = 1:1 (v:v) to afford a white solid in 93% yield (57.0 mg). 1H NMR (400
M, CDCl3): δ 7.64–7.59 (m, 4H), 7.44–7.40 (m, 2H), 7.37–7.32 (m, 4H), 6.91 (br, 4H),
3.54 (d, J = 13.6 Hz, 2H), 2.18 (d, J = 2 Hz, 3H).; 13C NMR (100 MHz, CDCl3): 136.3
(d, JC-P = 3.2 Hz), 132.4 (d, JC-P = 98.5 Hz), 131.7 (d, JC-P = 2.7 Hz), 131.1 (d, JC-P
=
9.0 Hz), 129.9 (d, JC-P = 5.3 Hz), 129.0 (d, JC-P = 2.5 Hz), 128.4 (d, JC-P = 10.6 Hz),
127.8 (d, JC-P = 8.0 Hz), 37.6 (d, JC-P = 66.6 Hz), 21.0.; 31P NMR (162 MHz, CDCl3):
δ 29.4. This compound is known [6], CAS number: 53144-71-1.
(4-(Tert-butyl)benzyl)diphenylphosphine oxide (3k)
The title compound was prepared according to the general experimental procedure
and purified by column chromatography on silica gel and eluted with petroleum ether:
ethyl acetate = 1:1 (v:v) to afford a white solid in 81% yield (56.4 mg), m.p.
o
1
248.4-248.7 C. H NMR (400 M, CDCl3): δ 7.64–7.59 (m, 4H), 7.42–7.38 (m, 2H),
7.36–7.31 (m, 4H), 7.12 (d, J = 8.4 Hz, 2H), 6.95 (dd, J = 8.4, 2.0 Hz, 2H), 3.54 (d, J
= 13.6 Hz, 2H), 1.16 (s, 9H).; 13C NMR (100 MHz, CDCl3): 149.5 (d, JC-P = 3.1 Hz),
132.4 (d, JC-P = 98.1 Hz), 131.6 (d, JC-P = 2.6 Hz), 131.1 (d, JC-P = 9.1 Hz), 129.7 (d,
JC-P = 5.2 Hz), 128.3 (d, JC-P = 11.6 Hz), 127.8 (d, JC-P = 8.0 Hz), 125.3 (d, JC-P = 2.5
15

Hz), 37.4 (d, JC-P = 66.6 Hz), 34.3, 31.2.; 31P NMR (162 MHz, CDCl3): δ 29.5.
HRMS (ESI) m/z: [M + H]+ calcd. for C23H25OP: 349.1721, found: 349.1716.
(3-Methylbenzyl)diphenylphosphine oxide (3l)
The title compound was prepared according to the general experimental procedure
and purified by column chromatography on silica gel and eluted with petroleum ether:
ethyl acetate = 1:1 (v:v) to afford a white solid in 94% yield (57.6 mg). 1H NMR (400
M, CDCl3): δ 7.64–7.59 (m, 4H), 7.44–7.40 (m, 2H), 7.37–7.33 (m, 4H), 6.99–6.96
(m, 1H), 6.89 (d, J = 7.6 Hz, 1H), 6.84 (s, 1H), 6.78 (d, J = 7.2 Hz, 1H), 3.54 (d, J =
13.6 Hz, 2H), 2.14 (s, 4H).; 13C NMR (100 MHz, CDCl3): 137.8 (d, JC-P = 1.4 Hz),
132.4 (d, JC-P = 97.1 Hz), 131.7 (d, JC-P = 1.4 Hz), 131.1 (d, JC-P = 8.7 Hz), 130.9 (d,
JC-P = 4.9 Hz), 130.8 (d, JC-P = 7.2 Hz), 128.3 (d, JC-P = 11.4 Hz), 128.1 (d, JC-P = 1.1
Hz), 127.5 (d, JC-P = 1.9 Hz), 127.0 (d, JC-P = 4.9 Hz),38.1 (d, JC-P = 65.8 Hz), 21.2.;
31P NMR (162 MHz, CDCl3): δ 29.6. This compound is known [6], CAS number:
23896-92-6.
(2-Methylbenzyl)diphenylphosphine oxide (3m)
The title compound was prepared according to the general experimental procedure
and purified by column chromatography on silica gel and eluted with petroleum ether:
ethyl acetate = 1:1 (v:v) to afford a white solid in 78% yield (47.8 mg). 1H NMR (400
M, CDCl3): δ 7.61–7.56 (m, 4H), 7.45–7.41 (m, 2H), 7.37–7.32 (m, 4H), 7.03-6.99 (m,
2H), 6.92–6.85 (m, 2H), 3.58 (d, J = 14.0 Hz, 2H), 2.06 (s, 3H).; 13C NMR (100 MHz,
16

CDCl3): 137.4 (d, JC-P = 5.4 Hz), 132.4 (d, JC-P = 97.8 Hz), 131.7 (d, JC-P = 2.7 Hz),
131.1 (d, JC-P = 9.1 Hz), 130.6 (d, JC-P = 4.6 Hz), 130.3 (d, JC-P = 2.1 Hz), 129.6 (d,
JC-P = 8.1 Hz), 128.4 (d, JC-P = 11.6 Hz), 126.9 (d, JC-P = 3.2 Hz), 125.6 (d, JC-P = 2.9
Hz), 35.2 (d, JC-P = 66.3 Hz), 20.0 (d, JC-P = 1.1 Hz).; 31P NMR (162 MHz, CDCl3): δ
29.6. This compound is known [3e], CAS number: 158871-10-4.
(Benzo[d][1,3]dioxol-5-ylmethyl)diphenylphosphine oxide (3n)
The title compound was prepared according to the general experimental procedure
and purified by column chromatography on silica gel and eluted with petroleum ether:
ethyl acetate = 1:1 (v:v) to afford a white solid in 95% yield (63.9 mg), m.p.
o
1
227.2-227.4 C. H NMR (400 M, CDCl3): δ 7.65–7.60 (m, 4H), 7.45–7.35 (m, 6H),
6.58-6.53 (m, 2H), 6.45 (d, J = 8.0 Hz, 1H), 5.80 (s, 2H), 3.50 (d, J = 13.2 Hz, 2H).;
13C NMR (100 MHz, CDCl3): 147.5 (d, JC-P = 1.8 Hz), 146.5 (d, JC-P = 2.7 Hz), 132.8,
131.8 (d, JC-P = 3.1 Hz), 131.1 (d, JC-P = 8.9 Hz), 128.5 (d, JC-P = 11.5 Hz), 124.4 (d,
JC-P = 8.2 Hz), 123.3 (d, JC-P = 5.8 Hz), 110.5 (d, JC-P = 4.6 Hz), 108.1 (d, JC-P = 2.2
31
Hz), 100.9, 37.6 (d, JC-P = 66.9 Hz).; P NMR (162 MHz, CDCl3): δ 29.4. HRMS
(ESI) m/z: [M + H]+ calcd. for C20H17O3P: 337.0994, found: 337.0990.
(Naphthalen-2-ylmethyl)diphenylphosphine oxide (3o)
The title compound was prepared according to the general experimental procedure
and purified by column chromatography on silica gel and eluted with petroleum ether:
ethyl acetate = 1:1 (v:v) to afford a white solid in 74% yield (50.7 mg). 1H NMR (400
17

M, CDCl3): δ 7.76–7.69 (m, 5H), 7.67–7.65 (m, 2H), 7.57 (s, 1H), 7.52–7.48 (m, 2H),
7.44–7.40 (m, 6H), 7.25–7.22 (m, 1H), 3.81 (d, J = 10.8 Hz, 2H).; 13C NMR (100
MHz, CDCl3): 133.3 (d, JC-P = 2.1 Hz), 132.3 (d, JC-P = 78.7 Hz), 132.2 (d, JC-P = 1.5
Hz), 131.8 (d, JC-P = 2.1 Hz), 131.2 (d, JC-P = 7.2 Hz), 128.9 (d, JC-P = 5.3 Hz), 128.7
(d, JC-P = 6.5 Hz), 128.5 (d, JC-P = 9.7 Hz), 128.1 (d, JC-P = 3.4 Hz), 127.9 (d, JC-P
=
1.5 Hz), 127.6 (d, JC-P = 0.6 Hz), 127.5 (d, JC-P = 1.0 Hz), 125.9, 125.6 (d, JC-P = 0.8
Hz), 38.4 (d, JC-P = 52.7 Hz).; 31P NMR (162 MHz, CDCl3): δ 29.3. This compound is
known [3e], CAS number: 935659-31-7.
Diphenyl(4-vinylbenzyl)phosphine oxide (3p)
The title compound was prepared according to the general experimental procedure
and purified by column chromatography on silica gel and eluted with petroleum ether:
ethyl acetate = 1:1 (v:v) to afford a white solid in 69% yield (43.9 mg). 1H NMR (400
M, CDCl3): δ 7.65–7.59 (m, 4H), 7.45–7.41 (m, 2H), 7.38–7.34 (m, 4H), 7.15 (d, J =
8.0 Hz, 2H), 6.99 (dd, J = 8.2, 1.8 Hz, 2H), 6.56 (dd, J = 19.4, 12.8 Hz, 1H), 5.59 (d,
J = 17.6 Hz, 1H), 5.11 (d, J = 10.8 Hz, 1H), 3.57 (d, J = 13.6 Hz, 2H).; 13C NMR (100
MHz, CDCl3): 136.4 (d, JC-P = 1.4 Hz), 136.1 (d, JC-P = 4.2 Hz), 132.7, 131.8 (d, JC-P
= 2.7 Hz), 131.1 (d, JC-P = 9.1 Hz), 130.7 (d, JC-P = 8.2 Hz), 130.2 (d, JC-P = 5.3 Hz),
128.5 (d, JC-P = 11.6 Hz), 126.2 (d, JC-P = 2.7 Hz), 113.6, 37.9 (d, JC-P = 66.0 Hz).; 31P
NMR (162 MHz, CDCl3): δ 29.3. This compound is known [17], CAS number:
741-41-3.
18

(4-Fluorobenzyl)diphenylphosphine oxide. (3q)
The title compound was prepared according to the general experimental procedure
and purified by column chromatography on silica gel and eluted with petroleum ether:
ethyl acetate = 1:1 (v:v) to afford a white solid in 91% yield (56.5 mg). 1H NMR (400
M, CDCl3): δ 7.70–7.66 (m, 4H), 7.53–7.50 (m, 2H), 7.46–7.43 (m, 4H), 7.08–7.05
(m, 2H), 6.88 (t, J = 6.8 Hz, 2H), 3.61 (d, J = 10.8 Hz, 2H).; 13C NMR (100 MHz,
CDCl3): 161.9 (d, JC-P = 197.8 Hz), 132.1 (d, JC-P = 78.9 Hz), 131.9 (d, JC-P = 2.2 Hz),
131.5 (dd, J = 6.4, 4.1 Hz), 131.1 (d, JC-P = 7.2 Hz), 128.5 (d, JC-P = 9.3 Hz), 126.8
(dd, J = 6.3, 2.6 Hz), 115.3 (dd, J = 20.6, 3.5 Hz), 37.2 (d, JC-P = 53.0 Hz).; 31P NMR
(162 MHz, CDCl3): δ 29.2 (d, JP-F = 4.05 Hz). This compound is known [12], CAS
number: 1393677-42-3.
4-((Diphenylphosphoryl)methyl)benzonitrile (3r)
The title compound was prepared according to the general experimental procedure
and purified by column chromatography on silica gel and eluted with petroleum ether:
ethyl acetate = 1:1 (v:v) to afford a white solid in 80% yield (50.8 mg). 1H NMR (400
M, CDCl3): δ 7.64–7.58 (m, 4H), 7.49–7.44 (m, 2H), 7.41–7.36 (m, 6H), 7.15 (dd, J =
8.4, 2.0 Hz, 2H), 3.62 (d, J = 13.6 Hz, 2H).; 13C NMR (100 MHz, CDCl3): 137.1 (d,
JC-P = 8.0 Hz), 132.2 (d, JC-P = 2.8 Hz), 132.0 (d, JC-P = 2.6 Hz), 131.5 (d, JC-P = 99.7
Hz), 131.0 (d, JC-P = 9.4 Hz), 130.8 (d, JC-P = 5.1 Hz), 128.7 (d, JC-P = 11.7 Hz), 118.7
31
(d, JC-P = 1.8 Hz), 110.7 (d, JC-P = 3.0 Hz), 38.4 (d, JC-P = 64.0 Hz).; P NMR (162
MHz, CDCl3): δ 28.9. This compound is known [12], CAS number: 18629-19-1.
19

Diphenyl(4-(trifluoromethyl)benzyl)phosphine oxide (3s)
The title compound was prepared according to the general experimental procedure
and purified by column chromatography on silica gel and eluted with petroleum ether:
ethyl acetate = 1:1 (v:v) to afford a white solid in 87% yield (62.7 mg). 1H NMR (400
M, CDCl3): δ 7.64–7.59 (m, 4H), 7.47–7.43 (m, 2H), 7.39–7.35 (m, 6H), 7.15 (d, J =
7.6 Hz, 2H), 3.62 (d, J = 13.6 Hz, 2H).; 13C NMR (100 MHz, CDCl3): 135.5 (dd, JC-P
= 9.0, 1.0 Hz), 132.0 (d, JC-P = 2.7 Hz), 131.8 (d, JC-P = 99.4 Hz), 131.0 (d, JC-P = 9.1
Hz), 130.3 (d, JC-P = 5.0 Hz), 129.0 (dd, JC-P = 32.2, 1.0 Hz), 128.6 (d, JC-P = 11.8 Hz),
125.2-125.1 (m), 124.1 (q, JC-P = 269.4 Hz), 38.0 (d, JC-P = 64.8 Hz).; 31P NMR (162
MHz, CDCl3): δ 29.0. This compound is known [12], CAS number: 220396-39-4.
(4-Chlorobenzyl)diphenylphosphine oxide (3t)
The title compound was prepared according to the general experimental procedure
and purified by column chromatography on silica gel and eluted with petroleum ether:
ethyl acetate = 1:1 (v:v) to afford a white solid in 88% yield (57.5 mg). 1H NMR (400
M, CDCl3): δ 7.71–7.67 (m, 4H), 7.54–7.50 (m, 2H), 7.47–7.43 (m, 4H), 7.16 (d, J =
6.4 Hz, 2H), 7.05-7.03 (m, 2H), 3.61 (d, J = 10.8 Hz, 2H).; 13C NMR (100 MHz,
CDCl3): 132.8 (d, JC-P = 2.9 Hz), 132.0 (d, JC-P = 79.1 Hz), 131.9 (d, JC-P = 2.2 Hz),
131.3 (d, J = 4.2 Hz), 131.1 (d, JC-P = 7.3 Hz), 129.7 (d, JC-P = 6.5 Hz), 128.6 (d, JC-P
31
= 9.3 Hz), 128.5 (d, JC-P = 2.1 Hz), 37.5 (d, JC-P = 52.6 Hz).; P NMR (162 MHz,
CDCl3): δ 29.0. This compound is known [3e], CAS number: 53144-72-2.
20

(2-Chlorobenzyl)diphenylphosphine oxide (3u)
The title compound was prepared according to the general experimental procedure
and purified by column chromatography on silica gel and eluted with petroleum ether:
ethyl acetate = 1:1 (v:v) to afford a white solid in 85% yield (55.5 mg), m.p.
o
1
110.3-111.5 C. H NMR (400 M, CDCl3): δ 7.65–7.61 (m, 4H), 7.47–7.35 (m, 7H),
7.15–7.04 (m, 3H), 3.79 (d, J = 14.0 Hz, 2H).; 13C NMR (100 MHz, CDCl3): 134.2 (d,
JC-P = 6.8 Hz), 132.1 (d, JC-P = 99.1 Hz), 131.9 (d, JC-P = 4.3 Hz), 131.8 (d, J = 2.4
Hz), 131.1 (d, JC-P = 9.3 Hz), 129.7 (d, JC-P = 7.3 Hz), 129.3 (d, JC-P = 1.9 Hz), 128.4
(d, JC-P = 11.7 Hz), 128.2 (d, JC-P = 2.5 Hz), 126.8 (d, JC-P = 2.0 Hz), 34.6 (d, JC-P
=
31
66.4 Hz).; P NMR (162 MHz, CDCl3): δ 29.5. HRMS (ESI) m/z: [M + H]+ calcd.
for C19H16ClOP: 327.0706, Found: 327.0701.
(3,4-Dichlorobenzyl)diphenylphosphine oxide (3v)
The title compound was prepared according to the general experimental procedure
and purified by column chromatography on silica gel and eluted with petroleum ether:
ethyl acetate = 1:1 (v:v) to afford a white solid in 83% yield (59.9 mg). 1H NMR (400
M, CDCl3): δ 7.64–7.59 (m, 4H), 7.47–7.43 (m, 2H), 7.40–7.35 (m, 4H), 7.16 (d, J =
8.0 Hz, 1H), 7.08–7.07 (m, 1H), 6.89 (dt, J = 8.4, 2.0 Hz, 1H), 3.50 (d, J = 13.2 Hz,
2H).; 13C NMR (100 MHz, CDCl3): 132.2 (d, JC-P = 3.1 Hz), 132.0 (d, JC-P = 3.7 Hz),
131.8 (d, JC-P = 5.3 Hz), 131.6 (d, JC-P = 99.4 Hz), 131.5 (d, J = 7.9 Hz), 131.0 (d, JC-P
= 3.2 Hz), 130.9 (d, JC-P = 9.1 Hz), 130.1 (d, JC-P = 2.5 Hz), 129.3 (d, JC-P = 5.0 Hz),
21

31
128.6 (d, JC-P = 11.7 Hz), 37.2 (d, JC-P = 65.1 Hz).; P NMR (162 MHz, CDCl3): δ
28.8. This compound is known [18], CAS number: 101894-92-2.
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24

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25

In this study, we present the first palladium-catalyzed phosphorylation of benzyl
ammonium triflates with P(O)H compounds. Various benzylphosphorus compounds
were produced in good to excellent yields with high functional group tolerance. All
the three kinds of hydrogen phosphoryl compounds, i.e. H-phosphonates,
H-phosphinates and secondary phosphine oxides, were applicable to this reaction. The
succesful scale-up experiment and one-pot synthetic operation also well demonstrated
its practicality.

Declaration of interests
☒ The authors declare that they have no known competing financial interests or personal relationships
that could have appeared to influence the work reported in this paper.
☐The authors declare the following financial interests/personal relationships which may be considered
as potential competing interests: