Copper-catalyzed P-H insertion reactions of sulfoxonium ylides

Article abstract of DOI:10.1039/d1ob00948f

A copper-catalyzed P-H insertion reaction between sulfoxonium ylides and H-phosphorus oxides has been demonstrated, furnishing α-phosphonyl carboxylate derivatives in 41-93% yields. This methodology utilizing bench-stable and thermodynamically stable sulfoxonium ylides as carbene precursors in the presence of the inexpensive and readily available copper catalyst shows advantages such as mild reaction conditions, good functional group compatibility, and easy scale-up, which make this protocol attractive for large-scale chemical processing and processing at the industrial scale.

Full text of DOI:10.1039/d1ob00948f

Organic &
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Copper-catalyzed P–H insertion reactions of
sulfoxonium ylides†
Cite this: Org. Biomol. Chem., 2021,
19, 5767
Xinzhi Zhang, a Yangyang Zhang,a Cuijian Lianga and Jun Jiang
*
a,b
Received 15th May 2021,
Accepted 11th June 2021
DOI: 10.1039/d1ob00948f
rsc.li/obc
A copper-catalyzed P–H insertion reaction between sulfoxonium conditions to obtain various α-phosphonyl carboxylate deriva-
ylides and H-phosphorus oxides has been demonstrated, furnish- tives is highly valuable.
ing α-phosphonyl carboxylate derivatives in 41–93% yields. This
Sulfoxonium ylides have emerged as increasingly valuable
methodology utilizing bench-stable and thermodynamically stable carbene precursors with numerous advantages such as their
sulfoxonium ylides as carbene precursors in the presence of the in- thermally stable and crystalline nature, and nonvolatile
expensive and readily available copper catalyst shows advantages dimethyl sulfoxide (DMSO) as the byproduct.9 Remarkable
such as mild reaction conditions, good functional group compat- achievements have been made in X–H (X = N, O, S, B) insertion
ibility, and easy scale-up, which make this protocol attractive for reactions with sulfoxonium ylides as surrogates of diazo com-
large-scale chemical processing and processing at the industrial pounds (Scheme 1b).10–13 To the best of our knowledge, the P–
scale.
H insertion reaction with sulfoxonium ylides for the construc-
tion of C–P bonds has not been reported previously. In con-
tinuation of our research on metal carbene chemistry and con-
sidering the importance of organophosphorus compounds, we
describe herein the P–H insertion reactions with sulfoxonium
ylides catalyzed by the inexpensive and readily available
Organophosphorus compounds play key roles in various
fields, such as in agrochemistry,1 pharmacy,2 materials
science,3 and catalysis chemistry.4 The transition-metal-cata-
lyzed heteroatom–hydrogen bond (X–H) insertion of carbene
represents a straightforward and atom-economical method for
the construction of C-heteroatom bonds.5 Much effort has
been made to develop P–H insertion reactions of
H-phosphorus oxides with various diazo compounds,6 among
which the α-diazo carbonyl compound is a reactive metal–
carbene precursor for the construction of α-phosphonyl car-
boxylate derivatives (Scheme 1a-i).6a–c Large-scale reactions
using diazo compounds are challenging due to their thermal
instability and the release of nitrogen gas. Besides diazo com-
pounds, hydrazones7 and triazo compounds8 have already
been used as alternative carbene precursors in P–H insertions
(Scheme 1a-ii and iii). However, the generation of metal car-
benes from hydrazones and triazo compounds generally
suffers from the the use of excess amounts of a base or high
temperature. Therefore, the development of catalytic P–H
insertion with stable carbene precursors under mild reaction
aCollege of Chemistry and Chemical Engineering, Guangxi University, Nanning,
530004, P. R. China. E-mail: jiangjun@gxu.edu.cn
bGuangxi Key Laboratory of Electrochemical Energy Materials, Nanning, Guangxi
530004, P. R. China
†Electronic supplementary information (ESI) available. See DOI: 10.1039/
d1ob00948f
Scheme 1 Metal–carbene insertions for C–X bond formation.
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copper catalyst under mild reaction conditions for the syn- ditions with the typically used Rh, Ir, Ru, or Au catalyst
thesis of α-phosphonyl carboxylates (Scheme 1c). (entries 1–4). The reaction in the presence of 10 mol% CuCl
Initially, sulfoxonium ylide 1a and diphenylphosphine generated the desired insertion product 3a in 29% yield (entry
oxide 2a were studied as substrates for P–H insertions in DCM 5). Encouraged by this result, we next explored other copper
at room temperature (Table 1). First, we tested metal catalysts. catalysts (entries 6–13), among which inexpensive and readily
Unfortunately, no reaction occurred under the catalytic con- available Cu(OAc)2 proved superior, affording 3a in 63% yield
(entry 13). The solvents DMSO and DMF were found to be
essentially ineffective in the reaction (entries 14 and 15).
CHCl3 was a suitable solvent for this reaction, affording 3a in
40% yield (entry 16). The reaction was not subjected to notable
Table 1 Optimization of reaction conditionsa
temperature effects (see the ESI†). When the reaction was con-
ducted in the absence of a metal catalyst, no product was
obtained, indicating the important role of the copper catalyst
in the decomposition of sulfoxonium ylides (entry 13 vs. 17).
With the optimized reaction conditions established, we first
evaluated the substrate scope of H–phosphine oxides 2
Entry
Catalyst
Solvent
Yieldb (%)
(Scheme 2). Sulfoxonium ylide 1a and various H–phosphine
1
2
3
4
5
6
7
8
RhCp*Cl2
[Ir(COD)Cl]2
[Ru(p-cymene)]Cl2
AuCl
CuCl
Cu(acac)2
CuCN
CuI
CuBr2
CuTc
Cu(OTf)2
[(CH3CN)4Cu]PF6
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2
—
DCM
DCM
DCM
DCM
DCM
DCM
DCM
DCM
DCM
DCM
DCM
DCM
DCM
DMSO
DMF
CHCl3
DCM
N.R.
N.R.
N.R.
N.R.
29
43
29
37
40
29
43
46
63
N.R.
N.R.
40
9
10
11
12
13
14
15
16
17
N.R.
a Reaction conditions: the reactions were performed with 1a
(0.1 mmol) and 2a (0.2 mmol) in the presence of 10 mol% catalyst in
2.0 mL of solvent at room temperature for 18–36 h. b Isolated yield. N.
R. = no reaction.
Scheme 2 Scope of H–phosphine oxides. Reaction conditions: the
reactions were carried out with Cu(OAc)2 (0.01 mmol), 1a (0.10 mmol),
and 2 (0.20 mmol) in CH2Cl2 (2.0 mL) at room temperature for 18–36 h.
Isolated yield.
Scheme 3 Scope of sulfoxonium ylides. Reaction conditions: the reac-
tions were carried out with Cu(OAc)2 (0.01 mmol), 1 (0.10 mmol), and 2
(0.20 mmol) in CH2Cl2 (2.0 mL) at room temperature for 18–36 h.
Isolated yield.
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oxides 2 reacted smoothly in the presence of Cu(OAc)2 to
To demonstrate the synthetic utility of the catalytic reaction,
afford products 3a–f in moderate to high yields. H–phosphine a gram-scale experiment was performed. The reaction was con-
oxides with electron-rich substituted groups such as Me and ducted at a 4.0 mmol scale under the standard reaction con-
OMe were tolerated and gave 3b and 3c in 77% and 63% yield, ditions, affording 3i in 92% yield (Scheme 4).
respectively. Moreover, bis(benzo[d][1,3]dioxol-4-yl)phosphine
On the basis of the above experimental results and pre-
oxide could take part in the transformation to deliver the cedent literature,5a,10c,14 we propose a possible mechanism for
corresponding product 3d in moderate yield. Notably, when this P–H insertion reaction (Scheme 5). At the beginning of the
ethyl phenylphosphinate was chosen as the substrate, the catalytic cycle, the Cu–carbene complex A is the sulfoxonium
expected product 3e was obtained in 88% yield with 56 : 44 dr. ylide with the release of DMSO. The subsequent nucleophilic
Furthermore, the use of benzyl (phenyl)phosphine oxide was attack on the Cu–carbene complex A by phosphinous acid 2′,
also feasible for this reaction, producing 3f in 55% yield with tautomerized from 2, generates the zwitterionic intermediate
80 : 20 dr.
B, which forms the metal-associated ylide (C) that is in equili-
Next, a series of sulfoxonium ylides was investigated as brium with the free ylide (D). Both C and D afford the final
carbene precursors (Scheme 3). Sulfoxonium ylides bearing product 3 via a proton transfer.
different ester moieties all afforded the expected products 3 in
high yields. Sulfoxonium ylides with a tert-butyl ester group
furnished the P–H insertion products 3i, 3j, and 3k in 93%,
78%, and 92% yields, respectively. 1-Naphthyl and 2-naphthyl
Conclusions
In summary, we have accomplished a catalytic P–H insertion
reaction by using sulfoxonium ylides as carbene precursors.
This scalable protocol provides a straightforward approach for
substituted groups were all tolerated, providing the corres-
ponding products 3l and 3m in good yields (85% and 85%,
respectively). Furthermore, electron-rich motifs (R1
=
synthesizing α-phosphonyl carboxylate derivatives in moderate
to high yields. The great stability of sulfoxonium ylides, mild
reaction conditions, easy scale up, as well as the use of the in-
expensive and readily available copper catalyst make this cata-
lytic reaction attractive for large-scale chemical processing and
processing at the industrial scale.
4-C6H5C6H4, 4-MeC6H4, 3-MeOC6H4, 2-MeOC6H4) were toler-
ant and gave the desired products 3n–r with good chemoselec-
tivities (58–91% yields). Various halogen substituents such as
F, Cl, and Br at the para positions of the phenyl ring generated
products 3s–u in 66–91% yields. Aliphatic sulfoxonium ylides
were not investigated.
Conflicts of interest
There are no conflicts to declare.
Acknowledgements
We are grateful for financial support from the National Natural
Science Foundation of China (21762005) and the Natural
Scheme 4 Scaled-up reaction.
Science
Foundation
of
Guangxi
Province
(2015GXNSFDA139008).
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