Air-stable phosphine organocatalysts for the hydroarsination reaction

Article abstract of DOI:10.1016/j.jorganchem.2020.121216

Readily-available triarylphosphines are explored as organocatalysts for the hydroarsination reaction. When compared to transition metal catalysis, phosphine organocatalysis greatly improved solvent compatibility of the hydroarsination of nitrostyrenes. Upon complete conversion, arsine products were isolated in up to 99% yield while up to 48% of the phosphine catalyst was still active. A mechanism was proposed and structure-activity analysis regarding catalyst activity concluded that sterically-bulkier catalysts were effective at minimizing catalyst deactivation.

Full text of DOI:10.1016/j.jorganchem.2020.121216

Journal of Organometallic Chemistry 914 (2020) 121216
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Air-stable phosphine organocatalysts for the hydroarsination reaction
Wee Shan Tay, Yongxin Li, Xiang-Yuan Yang, Sumod A. Pullarkat, Pak-Hing Leung*
Division of Chemistry & Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore,
637371, Singapore
a r t i c l e i n f o
a b s t r a c t
Article history:
Readily-available triarylphosphines are explored as organocatalysts for the hydroarsination reaction.
When compared to transition metal catalysis, phosphine organocatalysis greatly improved solvent
compatibility of the hydroarsination of nitrostyrenes. Upon complete conversion, arsine products were
isolated in up to 99% yield while up to 48% of the phosphine catalyst was still active. A mechanism was
proposed and structure-activity analysis regarding catalyst activity concluded that sterically-bulkier
catalysts were effective at minimizing catalyst deactivation.
Received 13 January 2020
Received in revised form
4 March 2020
Accepted 5 March 2020
Available online 10 March 2020
© 2020 Published by Elsevier B.V.
Keywords:
Arsine
Hydroarsination
Organocatalysis
Oxidation
Phosphine
1. Introduction
conducted, encompassing its interaction with reagents, proposed
mechanism and possible deactivation pathways.
Early developments in hydroarsination reactions stalled due to
limited protocols and poor synthetic utility of the products [1]. The
attractive atom-economical CeAs bond formation strategy was
only revisited in the last decade with the introduction of organo-
metallic complexes, first as a stoichiometric reagent [2] and sub-
sequently in more cost-effective catalytic roles (Fig. 1) [3]. The
logical inception of organocatalysts as cheaper and more conve-
nient alternatives has yet to be explored in this recent reinvention
of the hydroarsination reaction. This was in spite of successful
organocatalytic hydroamination [4] and hydrophosphination [5]
reactions where Lewis-basic amines have been employed to acti-
vate the olefinic substrates.
Amines have been reported to initiate a competing homocou-
pling of the secondary arsine reagent via deprotonation [3a]. On the
other hand, phosphines, being less basic yet more nucleophilic in
nature, were proposed to circumvent such side reactions [6].
Organocatalysis was also expected to resolve the strong de-
pendency on alcoholic solvents observed in transition metal-
catalyzed variants [3a,b,d]. Herein, widely-available triar-
ylphosphines are investigated as potential catalysts in the hydro-
arsination reaction. An examination of the phosphine catalyst was
2. Results and discussion
Triarylphosphines were benchmarked against the recently-
developed Ni(II)-pincer catalyst with nitrostyrene 1a as a model
substrate (Table 1) [3b]. Arsine loadings were comparable to
existing protocols while catalyst loadings were referenced from
other organocatalytic hydrofunctionalization reactions [4,5c,d]. A
variety of solvents yielded the 1,4-arsine adduct 3a in good to
excellent yields with up to quantitative conversion in DCM (Entry
2). The catalysis also proceeded smoothly for internal olefins and
furnished structural isomer 3b in 64% yield (Entry 10). Aryl sub-
stituents, even at distal para-positions, were observed to influence
the reaction (Entry 11) while less-activated enones achieved <10%
conversion after 24 h suggesting that the phosphine-catalyzed
hydroarsination was less versatile in terms of substrate scope
than transition metal-catalyzed variants [3]. To better compare to
other organocatalyzed hydrofunctionalization reactions [4b,c,5c,d],
the reaction was conducted with 15 mol % of catalyst and the
product was isolated in a lower yield of 67% (Entry 12). However, it
was worth noting that the reaction proceeded smoothly in THF
(79% yield, Entry 7) and acetone (92% yield, Entry 8)- solvents for
which the Ni(II) pincer complex was inactive. This prompted a
consideration of fundamental reactivity differences between the
organophosphine and transition metal catalysts.
* Corresponding author.
E-mail address: pakhing@ntu.edu.sg (P.-H. Leung).
https://doi.org/10.1016/j.jorganchem.2020.121216
0022-328X/© 2020 Published by Elsevier B.V.

2
W.S. Tay et al. / Journal of Organometallic Chemistry 914 (2020) 121216
2e (Entries 1e5). The larger cone angle of ortho-substituted phos-
phine 2f resulted in a moderate yield of arsine 3a (51%, Entry 6) and
the use of bulky trimesitylphosphine 2g further lowered the yield
(30%, Entry 7). Other phosphine alternatives (eg. phosphine oxides,
alkylphosphines, triphenylamine, triphenylarsine) were also
screened for potential catalytic activity which concluded that the
availability of the phosphine lone pair was central to catalytic ac-
tivity [8]. It may be worth noting here that trialkylphosphines (eg.
PBu3, PtBu3, PEt3) were not further pursued as potential catalysts
due to their increased susceptibility to phosphine oxidation leading
to catalyst deactivation (vide infra). In terms of catalyst design, re-
sults from the screening of functionalized phosphines and phos-
phine alternatives were consistent with the nucleophilic nature of
other amine-catalyzed hydrofunctionalization reactions [4a,5a,b,d].
Related organocatalyzed hydrofunctionalization reactions have
proposed substrate activation via the nucleophilic addition of Lewis
basic catalysts to the substrate (Scheme 1) [.4a,b,5b,d] Alternatively,
transition metal-activation of the weakly-nucleophilic secondary
arsine reagent was used to generate a reactive anionic arsenide
species [3a,b]. This required alcoholic solvents to stabilize the in-
termediate, thereby causing poor reactivity in non-polar protic
solvents. Both activation modes were inapplicable to the current
phosphine-catalyzed reaction. Firstly, no interactions were
observed between PPh3 and nitrostyrene 1 with 31P{1H} NMR
spectroscopy [9,10]. Secondly, the catalysis was compatible with a
wide range of solvents (Table 1). The high pKa of HAsPh2
(pKa ¼ 20.3 in THF) [11]further supported the unlikely deproto-
nation of HAsPh2 by weakly-basic tertiary phosphines. It remains to
be seen if transient interaction between the tertiary phosphine and
energetically low-lying LUMOs of the secondary arsine may have
contributed to activating the secondary arsine reagent (Scheme 1).
Similar interactions have been previously documented in
phosphine-stabilized arsenium salts [12] and have also been
studied using X-ray crystallography and variable-temperature NMR
spectroscopy [13]. In this instance, no physical evidence could be
gathered from NMR or mass spectroscopy methods which suggest
Fig. 1. Key organometallic intermediates of hydroarsination reactions.
Table 1
Solvent screening.a
Entry
3
Solvent
t (h)
Yieldb (%)
1
2
3
4
5
6
7
8
3a
3a
3a
3a
3a
3a
3a
3a
3a
3b
3c
3a
Toluene
DCM
DEE
CHCl3
EA
Hexane
THF
Acetone
MeOH
DCM
DCM
DCM
24
24
24
24
24
24
24
24
24
48
48
48
78
99
54
79
69
54
79
92
68
61c
49
67
9
10
11
12d
a
Reaction conditions: nitrostyrene 1a (4.47 mg, 0.03 mmol, 1.0 eq.), HAsPh2
(8.28 mg, 0.04 mmol, 1.2 eq.), cat. PPh3 (2.36 mg, 0.01 mmol, 30 mol %), solvent
(1 mL).
b
Isolated yield.
c
Due product instability, conversion was reported instead.
Cat. PPh3 (1.18 mg, 0.005 mmol, 15 mol %) was used instead.
d
Table 2
Catalyst screening.a
Entry
R
Cone angle
Yield of 3ab (%)
1
2
3
4
5
6
7
C6H5 (2a)
145
145
145
145
145
194
e
99
85
81
88
55
51
30
4-OCH3C6H4 (2b)
4-ClC6H4 (2c)
3-CH3C6H4 (2d)
4-FC6H4 (2e)
2-CH3C6H4 (2f)
Mesityl (2g)
a
Reaction conditions: nitrostyrene 1a (4.47 mg, 0.03 mmol, 1.0 eq.), HAsPh2
(8.28 mg, 0.04 mmol, 1.2 eq.), cat. PR3 2 (0.01 mmol, 30 mol %), DCM (1 mL).
b
Isolated yield.
Firstly, a series of functionalized triarylphosphines 2 were
screened to investigate the role of the phosphine (Table 2) [7]. For
phosphines with the same cone angle, catalytic activity was lower
when the reaction was catalyzed by electron-deficient phosphine
Scheme 1. Plausible modes of catalyst activation.

W.S. Tay et al. / Journal of Organometallic Chemistry 914 (2020) 121216
3
Table 3
Investigating phosphine oxidation.a
Entry
PPh3 loading (equiv.)
Solvent
Yieldb (%)
1
2
3
4
5
6
7
8
9
10
1
1
1
1
1
1
DCM
48
49
45
42
37
38
52
76
43
48
MeOH
Acetone
DEE
Hexane
THF
30 mol %
30 mol %
30 mol %
30 mol %
DCM
MeOH
Acetone
DEE
Fig. 2. Molecular structure of diphenylarsinic acid.
a
Reaction conditions: Triphenylphosphine 2a (23.08 mg, 0.088 mmol, 1.0 eq.),
specialized reagents/conditions such as fluorinating reagents [14],
peroxides [15], and transition metal catalysts [16]. A series of
controlled experiments suggested that H2O was the oxygen source
for the arsine-mediated oxidation pathway [10]. Since previous
catalytic runs were conducted with degassed AR grade solvents and
glassware stored under ambient conditions, a model reaction was
set up to evaluate if the trace amounts of water present could
oxidize the phosphine catalyst (Table 3) [8]. The freeze-pump-thaw
method was employed for the solvents to eliminate the possibility
of phosphine oxidation by air through inefficient degassing. Indeed,
phosphine oxidation was detected in various solvents (Entries 1e6)
with a larger extent of oxidation under catalytic (30 mol %) loadings
of phosphine (Entries 7e10). Curiously, no evidence of H2 was
observed with 1H NMR spectroscopy when HAsPh2 and PPh3 were
stirred under inert conditions and we were unable to identify the
terminal oxidant. Also, no oxidation of PPh3 was observed when
HAsPh2 was replaced with HOAs(O)Ph2, thus ruling out the possi-
bility of an oxygen-transfer mechanism. It remains to be estab-
lished if the oxidation is second order (and stoichiometric) in
arsenic because all attempts to isolate the arsine derivative led to
the eventual formation of diphenylarsinic acid (Fig. 2).
HAsPh2 (59.84 mg, 0.26 mmol, 3.0 eq.), solvent (12 mL), RT, 24 h.
b
Average isolated yield of three runs.
Table 4
Screening of phosphines.a
Nevertheless, it was of immediate interest to minimize catalyst
deactivation by oxidation. The phosphine-catalyzed hydro-
arsination of nitrostyrene 1a was repeated in the presence of MS4A
to remove trace amounts of water. Unfortunately, this formed a
polymeric material from HAsPh2 leading to isolated product yields
of only 79% after several attempts. Rational catalyst design was
proposed as an alternative solution to minimize catalyst deactiva-
tion (Table 4) [8]. No notable resistance to oxidation was observed
for electron-deficient (2c, 2e), acidic (2l, 2m) and basic (2j, 2k)
phosphines. Alkylphosphines 2h and 2i were observed to be
particularly susceptible to oxidation which suggest that tri-
alkylphosphines may be less effective catalysts in this instance
(Entries 7 and 8). Sterically hindered tri(o-tolyl)phosphine 2f was
observed to be more resistant to oxidation (Entry 6), which was
encouraging because large ligand scaffolds are typically employed
in many well-developed phosphine organocatalysts [17] especially
for asymmetric transformations [18].
Entry
2
Yield of 4b (%)
Recovered 2b(%)
1
2
3
4
5
6
7
8
2a
2b
2c
2d
2e
2f
2h
2i
2j
76
69
76
73
78
44
37 (61)
31 (64)
78
16
15
27
18
12
43
0
0
9
15
22
16
18
10
11
12
2k
2l
2m
74
72
76
a
Reaction conditions: Phosphine 2 (0.088 mmol, 1.0 eq.), HAsPh2 (60.76 mg,
0.264 mmol, 3.0 eq.), MeOH (12 mL), RT, 24 h.
b
Isolated average yield over three runs. Yield in parentheses refers to that for the
phosphine dioxide.
3. Conclusion
that species A could have manifested as a high energy transition
state instead of an energetically stable intermediate.
An evaluation was conducted regarding the feasibility of phos-
phine organocatalysts for the hydroarsination reaction. An initial
comparison revealed that tertiary phosphines offered comple-
mentary reactivity to transition metal-catalyzed hydroarsination
reactions. On one hand, phosphine organocatalysts required more
electron-deficient olefins which limited substrate scope. On the
other hand, suitable substrates furnished the desired arsine
It may be worth noting that a significant catalyst deactivation
pathway was observed throughout the course of screening. As
presented above (Table 1 Entry 12), lowering the catalyst loading to
15 mol % led to a decrease in product yield despite longer reaction
times. This was unprecedented because triarylphosphines are well-
established to be relatively resistant to oxidation, requiring

4
W.S. Tay et al. / Journal of Organometallic Chemistry 914 (2020) 121216
products in excellent yields of up to 99%. Low solvent dependency
was a notable triumph over transition metal-catalyzed methodol-
ogies. A competing catalyst deactivation-by-oxidation pathway was
identified. The susceptibility of phosphine oxidation was system-
atically investigated, leading to the identification of variables to
reduce the rate of oxidation. Together, these developments suggest
that while phosphine organocatalysts could activate secondary
arsine reagents, this activation mode was less suitable for the
hydroarsination reaction as compared to transition metal catalysts.
Further work is in progress to explore other avenues for arsenic-
carbon bond formation with phosphine organocatalysts.
4.3.1. 4a
White solid. Mp: 160.1e160.8 ꢀC. 1H NMR (CDCl3, 400 MHz):
d
7.70e7.64 (m, 2H, Ar), 7.57e7.53 (m, 1H, Ar), 7.48e7.44 (m, 2H,
Ar); 13C NMR (CDCl3, 100 MHz):
d
132.8 (d, 3C, 1JPC ¼ 103.6 Hz, PC),
132.3 (d, 6C, 3JPC ¼ 9.9 Hz, PCCC), 132.1 (d, 3C, 4JPC ¼ 2.7 Hz, PCCCC).
128.7 (d, 6C, JPC ¼ 12.1 Hz, PCC); 31P{1H} NMR (CDCl3, 161 MHz):
2
d
29.1 (s, 1P). HRMS (þESI) m/z: (M þ H)þ calcd for C18H16OP,
279.0939; found, 279.0951.
4.3.2. 4b
White solid. Mp: 145.9e146.4 ꢀC. 1H NMR (CDCl3, 400 MHz):
d
7.59e7.54 (m, 6H, Ar), 6.96e6.94 (m, 6H, Ar), 3.84 (s, 3H, OCH3);
13C NMR (CDCl3, 75 MHz):
d
162.7 (d, 3C, 4JPC ¼ 2.7 Hz, PCCCC),134.2
4. Experimental section
(d, 6C, 3JPC ¼ 11.6 Hz, PCCC), 124.3 (d, 3C, 1JPC ¼ 115.6 Hz, PC), 114.3
(d, 6C, 2JPC ¼ 13.2 Hz, PCC), 55.6 (s, 3C, OCH3); 31P{1H} NMR (CDCl3,
4.1. General information
161 MHz):
C
d
28.8 (s, 1P). HRMS (þESI) m/z: (M þ H)þ calcd for
21H22O4P, 369.1256; found, 369.1256.
All reactions were carried out under a positive pressure of ni-
trogen using standard Schlenk technique. Solvents were purchased
from their respective companies (ACN, MeOH, DCM: VWR Chem-
icals, EE: Merck, toluene, n-hexane Avantor, Acetone: Sigma-
Aldrich, THF: Tedia) and degassed prior to use by sparging with
N2 (g). A Low Temp Pairstirrer PSL-1400 was used for controlling
low temperature reactions. Column chromatography was done on
Silica gel 60 (Merck). Melting points were measured using SRS
Optimelt Automated Point System SRS MPA100. NMR spectra were
recorded on Bruker AV 300, AV 400 and AV 500 spectrometers.
Chemical shifts were reported in ppm and referenced to an internal
SiMe4 standard (0 ppm) for 1H NMR, chloroform-d (77.23 ppm) for
13C NMR, and an external 85% H3PO4 for 31P{1H} NMR. Compounds
1a [3b], 1b [3d], 1c [3b] and HAsPh2 [19] were prepared according
to literature methods. All other reactants and reagents were used as
supplied.
4.3.3. 4c
White solid. Mp: 173.9e174.6 ꢀC. 1H NMR (CDCl3, 400 MHz):
d
7.60e7.55 (m, 6H, Ar), 7.48e7.445 (m, 6H, Ar); 13C NMR (CDCl3,
75 MHz):
d
139.4 (s, 3C, ClC), 133.7e133.6 (m, 9C, PC þ PCC), 129.4
(d, 6C, 3JPC ¼ 10.3 Hz, PCCC); 31P{1H} NMR (CDCl3, 161 MHz):
d 26.9
35
(s, 1P). HRMS (þESI) m/z: (M þ H)þ calcd for C18
H Cl3OP, 380.9770;
13
35
found, 380.9769; calcd for
C H
Cl327ClOP, 382.9740; found,
18 13
35
382.9742; calcd for C
calcd for C
H
Cl37Cl2OP, 384.9711; found, 384.9715;
18 13
37
H Cl3OP, 386.9681; found, 386.9698.
18 13
4.3.4. 4d
White solid. Mp: 112.0e113.1 ꢀC. 1H NMR (CDCl3, 400 MHz):
d
7.59e7.56 (m, 3H, Ar), 7.39e7.29 (m, 9H, Ar), 2.36 (s, 9H,CH3); 13
C
NMR (CDCl3, 100 MHz):
d
138.6 (d, 3C, 3JHH ¼ 12.0 Hz, CCH3), 132.9
(d, 3C, 4JPC ¼ 2.8 Hz, PCCCC), 132.7 (d, 3C, 1JPC ¼ 102.7 Hz, PC), 132.7
(d, 3C, 2JPC ¼ 9.5 Hz, PCC), 129.4 (d, 6C, 2JPC ¼ 10.1 Hz, PCC), 128.4 (d,
3
4.2. General procedure for catalytic hydroarsination of nitroolefins
3C, JPC ¼ 12.7 Hz, PCCC), 21.6 (s, 3C, CH3); 31P{1H} NMR (CDCl3,
161 MHz):
d
29.4 (s, 1P). HRMS (þESI) m/z: (M þ H)þ calcd for
Nitrostyrene 1 (, 0.03 mmol,1.0 equiv.), diphenylarsine (8.28 mg,
0.04 mmol, 1.2 equiv.) and catalyst (0.01 mmol, 30 mol %) were
dissolved in the stated solvent (1 mL) The reaction was stirred in
the dark at RT and volatiles were removed under reduced pressure
after 24 h. The crude product was purified by silica gel chroma-
tography (DCM) to afford compound 3 as white solids. The data
obtained for compound 3c was consistent with literature [3b].
C21H22OP, 321.1408; found, 321.1406.
4.3.5. 4e
White solid. Mp: 120- 121 ꢀC. 1H NMR (CDCl3, 400 MHz):
d
7.67e7.60 (m, 6H, Ar), 7.19e7.15 (m, 6H, Ar); 13C NMR (CDCl3,
100 MHz):
d
165.2 (dd, 3C, 1JFC ¼ 252.8 Hz, 4JPC ¼ 2.9 Hz, FC), 134.5
(dd, 6C, JPC ¼ 8.98 Hz, 3JFC ¼ 11.3 Hz, PCC), 128.2 (d, 3C,
2
1JPC ¼ 8.0 Hz, PC), 116.1 (dd, 6C, 2JFC ¼ 21.2 Hz, 3JPC ¼ 13.2 Hz, PCCC);
31P{1H} NMR (CDCl3, 161 MHz):
d
26.9 (s, 1P); 19F NMR (CDCl3,
4.2.1. 3a
376 MHz):
d
ꢁ106.0 (brs, 3F). HRMS (þESI) m/z: (M þ H)þ calcd for
White solid. Mp: 41- 42 ꢀC. 1H NMR (CDCl3, 400 MHz):
C18H13F3OP, 333.0656; found, 333.0658.
d
7.61e7.59 (m, 2H, Ar), 7.45e7.45 (m, 3H, Ar), 7.24e7.18 (m, 6H, Ar),
7.12e7.09 (m, 4H, Ar), 4.86 (dd, 1H, 3JHH ¼ 12.9 Hz, 3JHH ¼ 12.9 Hz,
4.3.6. 4f
NCH), 4.53 (dd,1H, 3JHH ¼ 13.1 Hz, 2JHH ¼ 3.8 Hz, AsCH), 4.26 (dd,1H,
White solid. Mp: 154.4e155.1 ꢀC. 1H NMR (CDCl3, 400 MHz):
7.45e7.41 (m, 3H, Ar), 7.33e7.30 (m, 3H, Ar), 7.17e7.14 (m, 3H, Ar),
3JHH ¼ 12.7 Hz, JHH ¼ 3.8 Hz, AsCH); 13C NMR (CDCl3, 100 MHz):
2
d
d
134.1e127.5 (18C, Ar), 78.7 (s, 1C, NC), 43.2 (s, 1C, AsC). HRMS
7.12e7.07 (m, 3H, Ar), 2.50 (s, 9H, CH3); 13C NMR (CDCl3, 100 MHz):
(þESI) m/z: (M þ H)þ calcd for C20H19NO2As, 380.0632; found,
380.0630. Anal. Calcd for C20H18NO2As: C, 63.33; H, 4.78; N, 3.69.
Found: C, 63.34; H, 5.09; N, 3.95%.
2
d
143.8 (d, 3C, JPC ¼ 7.6 Hz, H3CC), 133.2e131.5 (m, 12C, Ar), 125.7
(d, 3C, 3JPC ¼ 12.6 Hz, PCCC), 22.2 (d, 3C, 3JPC ¼ 3.8 Hz, H3C), 31P{1H}
NMR (CDCl3, 161 MHz):
d
37.1 (s, 1P). HRMS (þESI) m/z: (M þ H)þ
calcd for C21H22OP, 321.1408; found, 321.1411.
4.3. General procedure for the oxidation of tertiary phosphines
4.3.7. 4h
Diphenylarsine (60.76 mg, 0.264 mmol, 3.0 equiv.) was charged
to a pre-weighed Schlenk flask and dissolved in the stated solvent
(6 mL). Tertiary phosphine 2 (0.088 mmol, 1.0 equiv.) was subse-
quently added, washed down with the stated solvent (6 mL) and
the reaction was stirred for 24 h at RT in the dark. Volatiles were
removed and pure phosphine oxide 4 was obtained upon recrys-
tallization from DCM/H.
White solid. Mp: 270.3e271.1 ꢀC. 1H NMR (CDCl3, 400 MHz):
d
7.73e7.70 (m, 8H, Ar), 7.69e7.50 (m, 4H, Ar), 7.47e7.44 (m, 8H, Ar),
2.53 (d, 4H, 2JPH ¼ 1.6 Hz, CH2); 13C NMR (CDCl3, 100 MHz):
d 132.3
1
(s, 4C, Ar), 131.1e129.0 (m, 10C, Ar), 21.9 (dd, 2C, JPC ¼ 40.0 Hz,
2JPC ¼ 34.2 Hz, PCH2); 31P{1H} NMR (CDCl3, 161 MHz):
d 33.2 (s, 2P).
HRMS (þESI) m/z: (M þ H)þ calcd for C26H25O2P2, 431.1330; found,
431.1340.

W.S. Tay et al. / Journal of Organometallic Chemistry 914 (2020) 121216
5
4.3.8. 4i
Yellow solid. Mp: 244- 245 ꢀC. 1H NMR (CDCl3, 400 MHz):
7.60e7.55 (m, 8H, Ar), 7.49e7.45 (m, 4H, Ar), 7.40e7.39 (m, 8H,
Appendix A. Supplementary data
d
Supplementary data to this article can be found online at
https://doi.org/10.1016/j.jorganchem.2020.121216.
Ar), 4.70 (brs, 4H, Fc), 4.26 (brs, 4H, Fc); 13C NMR (CDCl3, 100 MHz):
d
133.9 (d, 4C, 1JPC ¼ 105.7 Hz, PCAr),131.8 (s, 4C, PCCCC),131.4 (d, 8C,
2JPC ¼ 9.8 Hz, PCCAr), 128.4 (d, 8C, 3JPC ¼ 12.0 Hz, PCCCAr), 74.5 (d, 2C,
References
1JPC ¼ 1114.5 Hz, PCFc), 74.2 (d, 4C, 1JPC ¼ 114.5 Hz, PCFc), 74.2 (d, 8C,
3JPC ¼ 10.1 Hz, PCCCFc), 74.6 (d, 8C, JPC ¼ 12.5 Hz, PCCFc); 31P{1H}
2
[1] a) K. Maitra, V.J. Catalano, J. Clark III, J.H. Nelson, Inorg. Chem. 37 (1998)
28.2 (s, 1P). HRMS (þESI) m/z: (M þ H)þ
1105e1111;
NMR (CDCl3, 161 MHz):
d
€
b) H.-O. Berger, H. Noth, J. Organomet. Chem. 250 (1983) 33e48.
calcd for C34H29FeO2P2, 587.0992; found, 587.0995.
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4215e4220;
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4134e4140.
4.3.9. 4j
White solid. Mp: 106- 107 ꢀC. 1H NMR (CDCl3, 400 MHz):
d
8.78e8.29 (m, 1H, NCH), 7.90e7.82 (m, 1H, Ar), 7.53e7.49 (m, 5H,
[3] a) W.S. Tay, X.-Y. Yang, Y. Li, S.A. Pullarkat, P.-H. Leung, Dalton Trans. 48
(2019) 4602e4610;
Ar), 7.46e7.45 (m, 2H, Ar), 7.44e7.41 (m, 2H, Ar), 7.40e7.38 (m, 1H,
Ar); 13C NMR (CDCl3, 100 MHz):
d
156.6 (d, 1C, 1JPC ¼ 130.0 Hz, NCP),
b) W.S. Tay, X.-Y. Yang, Y. Li, S.A. Pullarkat, P.-H. Leung, Chem. Eur J. 25 (2019)
11308e11317;
c) C.A. Bange, R. Waterman, Polyhedron 156 (2018) 31e34;
d) W.S. Tay, X.-Y. Yang, Y. Li, S.A. Pullarkat, P.-H. Leung, Chem. Commun. 53
(2017) 6307e6310;
3
2
150.3 (d, 1C, JPC ¼ 19.0 Hz, NCH), 136.5 (d, 1C, JPC ¼ 9.1 Hz, PCC),
132.4 (d, 2C, 1JPC ¼ 103.7 Hz, PC), 132.3 (d, 2C, JPC ¼ 9.4 Hz, PCC),
2
132.1 (d, 1C, 4JPC ¼ 2.3 Hz, PCCCC), 128.7e128.5 (m, 7C, Ar), 125.4 (d,
2C, 4JPC ¼ 2.14 Hz, PCCCC); 31P{1H} NMR (CDCl3, 161 MHz):
d 20.8 (s,
e) A.J. Roering, J.J. Davidson, S.N. MacMillan, J.M. Tanski, R. Waterman, Dalton
Trans. (2008) 4488e4498.
1P). HRMS (þESI) m/z: (M þ H)þ calcd for C17H15NOP, 280.0891;
ꢀ
[4] a) I. Ibrahem, P. Hammar, J. Vesely, R. Rios, L. Eriksson, A. Cordova, Adv. Synth.
found, 280.0892.
Catal. 350 (2008) 1875e1884;
b) I. Ibrahem, R. Rios, J. Vesely, P. Hammar, L. Eriksson, F. Himo, A. Cordova,
ꢀ
Angew. Chem. Int. Ed. 46 (2007) 4507e4510;
c) G. Bartoli, M. Bosco, A. Carlone, M. Locatelli, A. Mazzanti, L. Sambri,
P. Melchiorre, Chem. Commun. (2007) 722e724.
4.3.10. 4k
White solid. Mp: 93- 94 ꢀC. 1H NMR (CDCl3, 400 MHz):
d
8.53e8.51 (m, 1H, Ar), 7.65e7.45 (m, 11H, Ar), 7.40e7.36 (m, 1H,
[5] a) B.-J. Li, C. El-Nachef, A.M. Beauchemin, Chem. Commun. 53 (2017)
13192e13204;
Ar), 7.11e7.06 (m, 1H, Ar), 4.93 (s, 2H, NCH2), 3.19 (s, 6H, NCH3); 13
C
ꢀ
2
b) P. Diner, M. Neilsen, M. Marigo, K.A. Jørgensen, Angew. Chem. Int. Ed. 46
NMR (CDCl3, 100 MHz):
d
136.2 (d, 1C, JPC ¼ 9.28 Hz, PCCCH2),
(2007) 1983e1987;
c) H. Sunden, R. Rios, I. Ibrahem, G.-L. Zhao, L. Eriksson, A. Cordova, Adv. Synth.
Catal. 349 (2007) 827e832;
133.7e128.8 (m, 17C, Ar), 70.1 (s, 1C, NCH2), 59.4 (s, 2C, NCH3); 31
P
ꢀ
ꢀ
{1H} NMR (CDCl3, 161 MHz):
d
33.1 (s, 1P). HRMS (þESI) m/z:
(M þ H)þ calcd for C22H22NOP, 347.1439; found, 347.1433.
d) Y.K. Chen, M. Yoshida, D.W.C. MacMillan, J. Am. Chem. Soc. 128 (2006)
9328e9329.
[6] J.L. Methot, W.R. Roush, Adv. Synth. Catal. 346 (2004) 1035e1050.
[7] J.A. Bilbrey, A.H. Kazez, J. Locklin, W.D. Allen, J. Comput. Chem. 34 (2013)
1189e1197.
4.3.11. 4l
White solid. Mp: 270.6e271.0 ꢀC. 1H NMR (CDCl3, 400 MHz):
8.17e8.14 (m, 2H, HOOCCCH), 7.80e7.75 (m, 2H, HOOCCCCH),
[8] See ESI Page S3-5 for Experimental Data.
d
[9] In the Event of Phosphine-Substrate Interaction, the Appearance of a Signal
Corresponding to the Zwitteranionic Phosphine-Olefin Adduct Was Expected
to Be Observable with 31P{1H} NMR Spectroscopy. a) I.C. Stewart,
R.G. Bergman, F.D. Toste, J. Am. Chem. Soc. 125 (2003) 8696e8697;
b) D.A. White, M.M. Baizer, Tetrahedron Lett. 14 (1973) 3597e3600.
[10] See ESI Page S30-35 for the Related NMR Spectra.
7.71e7.66 (m, 4H, Ar), 7.59e7.55 (m, 2H, Ar), 7.51e7.46 (m, 4H, Ar);
13C NMR (CDCl3, 100 MHz):
d
168.7 (s, 1C, HOOC), 133.3e129.0 (18C,
Ar); 31P{1H} NMR (CDCl3, 161 MHz):
d
31.0 (s, 1P). HRMS (þESI) m/z:
(M þ H)þ calcd for C19H16O3P, 323.0837; found, 323.0840.
[11] a) K. Issleib, R. Kümmel, J. Organomet. Chem. 3 (1965) 84e91;
b) J.-N. Li, L. Liu, Y. Fu, Q.-X. Guo, Tetrahedron 62 (2006) 4453e4462.
[12] a) J.C. Summers, H.H. Sisler, Inorg. Chem. 9 (1970) 862e869;
4.3.12. 4m
White solid. Mp: 110.2e110.8 ꢀC. 1H NMR (CDCl3, 300 MHz):
ꢁ
b) C. Payrastre, Y. Madaule, J.G. Wolf, T.C. Kim, M.R. Mazieres, R. Wolf,
M. Sanchez, Heteroat. Chem. 3 (1992) 157e162.
[13] K.A. Porter, A.C. Willis, J. Zank, S.B. Wild, Inorg. Chem. 41 (2002) 6380e6386.
[14] a) Q. Chen, J. Zeng, X. Yan, Y. Huang, Z. Du, K. Zhang, C. Wen, Tetrahedron Lett.
57 (2016) 3379e3381;
d
7.76e7.80 (m, 4H, Ar), 7.57e7.48 (m, 6H, Ar), 2.68 (m, 4H,
CH2CH2COOH þ CH2CH2COOH); 13C NMR (CDCl3, 75 MHz):
d 174.1
3
4
(d, 1C, JPC ¼ 12.7 Hz, COOH), 132.6 (d, 2C, JPC ¼ 2.1 Hz, PCCCC),
131.3 (d, 2C, 1JPC ¼ 101.2 Hz, PC), 131.0 (d, 4C, JPC ¼ 9.6 Hz, PCC),
b) W. Peng, J.M. Shreeve, J. Fluor. Chem. 126 (2005) 1054e1056.
[15] a) S. Sasaki, K. Sutoh, Y. Shimizu, K. Kato, M. Yoshifuji, Tetrahedron Lett. 55
(2014) 322e325;
2
129.2 (d, 4C, 3JPC ¼ 11.8 Hz, PCCC), 27.0 (d, 1C, 2JPC ¼ 2.2 Hz, HOOCC),
24.9 (d, 1C, JPC ¼ 72.5 Hz, PCH); 31P{1H} NMR (CDCl3, 161 MHz):
1
ꢀ
b) R.T. Boere, Y. Zhang, J. Organomet. Chem. 690 (2005) 2651e2657;
d
35.7 (s, 1P). HRMS (þESI) m/z: (M þ H)þ calcd for C15H16O3P,
c) R.D. Bach, M.N. Glukhovstev, C. Canepa, J. Am. Chem. Soc. 120 (1998)
77e873.
275.0837; found, 275.0842.
[16] (a) I.D. Rettig, J. Van, J.B. Brauer, T.M. McCormick, Dalton Trans. 48 (2019)
5665e5673;
Declaration of competing interest
b) Y.-M. Lee, M. Yoo, H. Yoon, X.-X. Li, W. Nam, S. Fukuzumi, Chem. Commun.
53 (2017) 9352e9355;
c) R. Dobrovetsky, D.W. Stephan, Angew. Chem. Int. Ed. 52 (2013) 2516e2519;
d) A. Cervilla, F. Perez-Pla, E. Llopis, M. Plies, Inorg. Chem. 45 (2006)
7357e7366;
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.
ꢀ
e) G. Du, J.H. Espenson, Inorg. Chem. 44 (2005) 2465e2471;
f) W. Levason, R. Patel, G. Reid, J. Organomet. Chem. 688 (2003) 280e282.
[17] Z. Zhou, Y. Wang, C. Tang, Curr. Org. Chem. 15 (2011) 4083e4107 (and ref-
erences therein).
Acknowledgments
[18] (For examples of bulky chiral phosphine organocatalysts, see) a) Y. Xiao,
Z. Sun, H. Guo, O. Kwon, Beilstein J. Org. Chem. 10 (2014) 2089e2121;
b) A. Marinetti, A. Voituriez, Synlett 2 (2010) 174e194;
c) H. Ni, W.-L. Chan, Y. Lu, Chem. Rev. 118 (2018) 9344e9411.
[19] J.K.-P. Ng, G.-K. Tan, J.J. Vittal, P.-H. Leung, Inorg. Chem. 42 (2003) 7674e7682.
W. S. T. acknowledges NTU for the award of a research schol-
arship. This work was supported by the Nanyang Technological
University [M401110000 RG 10/19].