Rhodium-Catalyzed Insertion Reaction of PhP Group of Pentaphenylcyclopentaphosphine with Acyclic and Cyclic Disulfides

Article abstract of DOI:10.1021/acs.orglett.7b03825

Organophosphorus compounds with a phosphorus atom attached to a phenyl group and two organothio/organoseleno groups were synthesized using the rhodium-catalyzed insertion reaction of the PhP group of pentaphenylcyclopentaphosphine (PhP)₅ with acyclic disulfides and diselenides. The method was applied to the synthesis of heterocyclic compounds containing the S-P-S group by the reaction of (PhP)₅ and cyclic disulfides such as 1,2-dithietes, 1,2-dithiocane, 1,4,5-dithiopane, and 1,2-dithiolanes.

Full text of DOI:10.1021/acs.orglett.7b03825

Letter
pubs.acs.org/OrgLett
Cite This: Org. Lett. XXXX, XXX, XXX−XXX
Rhodium-Catalyzed Insertion Reaction of PhP Group of
Pentaphenylcyclopentaphosphine with Acyclic and Cyclic Disulfides
Mieko Arisawa,* Kyosuke Sawahata, Tomoki Yamada, Debayan Sarkar,† and Masahiko Yamaguchi*
Department of Organic Chemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba, Sendai, 980-8578, Japan
S
* Supporting Information
ABSTRACT: Organophosphorus compounds with a phosphorus
atom attached to a phenyl group and two organothio/organoseleno
groups were synthesized using the rhodium-catalyzed insertion
reaction of the PhP group of pentaphenylcyclopentaphosphine
(PhP)5 with acyclic disulfides and diselenides. The method was
applied to the synthesis of heterocyclic compounds containing the S−P−S group by the reaction of (PhP)5 and cyclic disulfides
such as 1,2-dithietes, 1,2-dithiocane, 1,4,5-dithiopane, and 1,2-dithiolanes.
ligomeric organophosphanes (RP)n possessing P atoms
attached to one organo moiety and two P atoms are an
metal halides. We consider that (i) the direct transformation of
P4 is preferable for the synthesis of organophosphorus
compounds, in terms of saving energy and resources,10 and
(ii) chemical studies of the (RP)n compounds are critical for
such purpose.
We previously developed the addition reaction of diphos-
phines to unsaturated organic compounds and the single-bond
metathesis reaction of diphosphines with diphosphines,
disulfides, alcohols, 1-organothioalkynes, and acyl compounds,
which involved P−P bond cleavage under rhodium- and
palladium-catalyzed conditions.11 A P atom of a diphosphine
possesses one P−P bond and two C−P bonds, and the
reactivity of (RP)n compounds with a P atom possessing two
P−P bonds is of interest. Described here is the rhodium-
catalyzed synthesis of organophosphorus compounds, in which
a P atom is attached to a phenyl group and two organothio
groups by the reaction of acyclic disulfides and 1 (Scheme 1).
O
interesting group of polyphosphorus compounds that exhibit
notable chemical properties, because of the P−P−P group.1 It
was considered that chemical reactions of such compounds
could provide synthetic routes to various organophosphorus
compounds containing X−P−X groups if two P−P bonds of P
atoms could be efficiently converted to P−X bonds. It is then
crucial to understand and control the chemical reactivity of P−
P−P bond systems, and a transition-metal-catalyzed reaction of
(RP)n compounds is considered an attractive approach.
Among various (RP)n compounds, pentaphenylcyclopenta-
phosphine (PhP)5 (1) can readily be synthesized by the
reaction of dichlorophenylphosphine and magnesium.2 How-
ever, its chemical reactivity has not been significantly examined,
except for a few examples: alkylation of 1 with alkyllithium gave
mixtures of oligophosphide Li(PhP)nR (n = 1−4);3 substitution
of 1 with 1,2-dichlorobenzene in the presence of a
stoichiometric amount of potassium provided 1,2,3-triphenyl-
1,2,3-triphosphaindan;4 addition of 1 to diphenylacetylene at
240 °C gave a mixture of 1,2-diphenyl-1,2-diphosphetene and
pentaphenyltriphospholene;5 and carbene-phosphinidene ad-
ducts formed via the addition of 1 to carbene such as N-
heteroacyclic carbenes and bicyclic (alkyl)(amino)carbene.6
Woollins reagent obtained from 1 and selenium powder are
also used in organic synthesis.7 The insertion reaction of the
PhP group into a single bond was reported for bis-
(trifluoromethyl) disulfide at 120 °C to give phenylphospho-
nodithious acid bis(trifluoromethyl) ester.8a The PhP group in
Scheme 1. Rhodium-Catalyzed Synthesis of Cyclic and
Acyclic Organophosphorus Compounds with S−P−S Bonds
Using (PhP)5 (1) and Disulfides
The reaction was also employed for the efficient synthesis of
heterocycles containing S and P atoms when applied to cyclic
disulfides. 1 reacted with diphenyl diselenide and dibutyl
diselenide. The rhodium complex effectively inserts a PhP
group of 1 into group 16 heteroatom−heteroatom single
bonds.
1 was also inserted to hexa(pentafluorophenyl)digermane.8b
A
transition-metal-catalyzed reaction of 1 was not reported,
although the complexation of a transition metal and 1 was
known.9
Essentially, all organophosphorus compounds are now
synthesized from P4, which is converted to phosphorus
trichloride (PCl3) or phosphoryl chloride (POCl3). Substitu-
tion of chloride with various groups in the presence of bases
provides organophosphorus compounds, which are accompa-
nied by the formation of stoichiometric amounts of inorganic
It was initially confirmed that the P−P bond of 1 can be
cleaved and the PhP group can be inserted into the S−S bond
Received: December 7, 2017
© XXXX American Chemical Society
A
DOI: 10.1021/acs.orglett.7b03825
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
of acyclic disulfides by rhodium catalysis (see Scheme 2). When
1 (1 equiv atom) was reacted with di(hexyl) disulfide (2a) in
Scheme 2. Rhodium-Catalyzed Reaction of Disulfides/
Diselenides and 1
Figure 1. ORTEP view of 7a.
Table 1. Rhodium-Catalyzed Synthesis of 1,3,2-
Dithiaphosphorus Derivatives
the presence of RhH(dppe)2 (5 mol %) in refluxing THF for 15
min, phenylphosphonodithious acid di(hexyl) ester (3a) was
obtained in 94% yield. It was noted that five PhP groups of 1
were effectively inserted into the S−S bond. No reaction
occurred in the absence of RhH(dppe)2. RhH(PPh3)4 in the
presence of dppe exhibited similar reactivity, whereas RhCl-
(PPh3)3, [Rh(OAc)]2, Rh(acac)3, and Pd(OAc)2 were inactive.
Aliphatic disulfides with triethylsilyloxy and methoxycarbonyl
groups also reacted effectively (2b and 2c). The reaction of 1
and diphenyl disulfide 2d gave phenylphosphonodithious acid
diphenyl ester 3d (90%). 1 reacted with diphenyl diselenide 4a
and dibutyl diselenide 4b, and the products 5a and 5b were
isolated after air oxidization. Using the rhodium complex, two
P−P bonds of 1 were cleaved, and the PhP group was inserted
into the S−S and Se−Se bonds.
The reaction of 1 was applied to four-membered cyclic
disulfides. When 1 was reacted with 3-(t-butyl)-4-phenyl-1,2-
dithiete (6a)12 (1 equiv) in the presence of RhH(dppe)2 (5
mol %) in refluxing THF for 0.5 h, 2-phenyl-4-(t-butyl)-5-
phenyl-1,3,2-dithiaphosphole (7a) was obtained in 77% yield
(see Scheme 3). The structure of 7a was determined by X-ray
Scheme 3. Rhodium-Catalyzed Synthesis of 1,3,2-
Dithiaphospholes
a)Yield of 9a′ was calculated on the basis of 8a. A mixture (R*,R*)-9a′:
(R*,S*)-9a′ = 1:1 was obtained.
crystal structure analysis (see Figure 1). 3-(t-Butyl)-4-(4-tolyl)-
1,2-dithietes (6b) also gave 1,3,2-dithiophospholes (7b) in 73%
yield. The 1,3,2-dithiophospholes obtained here are new
compounds. The reaction of 1 and 1,2-dithietes, which, in
turn, are readily obtained from alkynes and S8,11 can be a novel
efficient synthetic method for 1,3,2-dithiophospholes from
alkynes.13
The reaction of 1 and five-, seven-, and eight-membered
cyclic disulfides was conducted (see Table 1). 1,2-Dithiocane
(8a) reacted with 1, giving the corresponding ring-expanded
compound 9a, along with cyclic dimers 9a′ [(R*,R*)-9a′:
(R*,S*)-9a′ = 1:1]. The PhP group was efficiently inserted into
the S−S bond of 1-oxa-4,5-dithiepane (8b), 1,2-dithiolane-3-
pentanoic acid methyl ester (8c), and 3H-1,2-benzodithiol-3-
one dioxide (8d), and the corresponding ring-expanded
compounds 9b−9d were obtained in high yields. A rhodium
complex can be used for the synthesis of the heterocyclic
compound possessing S−P−S bonds via the cleavage of two
B
DOI: 10.1021/acs.orglett.7b03825
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
P−P bonds in (PhP)5 and the S−S bond in disulfides. As an
exception, 3H-1,2-benzodithiol-3-one (8e) gave 2-phenyl-1,2-
benzoisothiaphosphole-3(2H)-one (9e) with desulfurization.
All cyclic organophosphorus products obtained here are new
compounds.
active and unstable rhodium species with a structure related to
11 is formed.16
A possible mechanism of this reaction is shown in Scheme 5.
RhH(dppe)2 and 1 react to provide a diphenyl diphosphene
The activation mechanism of (PhP)5 1 with a RhH(dppe)2
complex was investigated. RhH(dppe)2 was reacted with 1 (2.0
equiv atom) in refluxing THF for 1 h, and the solvent was
removed. As indicated by 31P NMR, a mixture was formed,
containing RhH(dppe)2 δ 57.0 (d, J = 133.0 Hz, 50%) and
other rhodium complexes were observed at δ 56.2 (d, J = 143.9
Hz), 27.7 (d, J = 48.9 Hz), and 13.2 (d, J = 47.5 Hz). The
residue was washed with hexane and chloroform, and
[Rh+(dppe)2]Cl− complex 10 (73%) was formed (see Scheme
4).14 The Cl− ion in 10 was derived from the chloroform used
Scheme 5. A Possible Mechanism
Scheme 4. Activation Mechanism of (PhP)5 (1) with a
RhH(dppe)2 Complex
rhodium complex A. Then, rhodium intermediate B is formed
via oxidative addition of rhodium complex A and the S−S
bond, and the phosphide intermediate C was formed by the
insertion of a PhP group. The organophosphorus compounds
with the S−P(Ph)−S group were liberated by reductive
elimination, and the rhodium catalyst was regenerated by
insertion of 1.
In summary, in the presence of a rhodium complex, PhP
groups in (PhP)5 1 were inserted into the S−S bonds of cyclic
and acyclic disulfides to give organophosphorus compounds
containing the S−P−S group. A rhodium complex can
effectively react with a polyphosphine containing a P atom
with two P−P bonds. This reaction provides a useful synthetic
method for the preparation of organophosphorus compounds
with acyclic and cyclic structures.
to wash the complex. Because 10 did not contain 1, the
elimination of the phosphorus group from rhodium metal was
considered to be very rapid. Isocyanide was then added to
stabilize the rhodium complex containing 1. RhH(dppe)2 and
1-adamantlyisocyanide (4 equiv) were reacted with 1 (4 equiv
atom) in refluxing THF for 1 h. The solvent was removed, and
the mixture was washed with hexane, chloroform, and
acetonitrile to give [Rh(PhPPPh)(dppe)(AdNC)2]Cl com-
plex 11 in 59% yield as yellow crystals (Scheme 4). The
structure was determined by liquid chromatography-mass
spectroscopy (LC-MS) (electrospray ionization (ESI)) analysis,
m/z 1039.3075, [Rh(PhPPPh)(dppe)(AdNC)2]+: calcd for
1039.3048. 31P NMR analysis showed two peaks at δ −28.4 (dt,
J = 21.4, 19.8 Hz) and δ 42.1 (dt, J = 96.4, 19.9 Hz), which
were assigned to the π-coordinated diphenyldiphosphene15 and
the equatorial-coordinated dppe ligand, respectively. Infrared
(IR) analysis showed an absorption of isocyanide at 2190 cm−1.
Two isocyanides were considered to be coordinated at two
equatorial positions. The Cl− ion in 11 was derived from
chloroform used to wash the complex. The results indicated the
formation of rhodium diphosphene complex 11 with a π-
coordinated PP bond. When di(hexyl) disulfide (2a) was
reacted with complex 11 in refluxing THF for 1 h, 3a was
obtained in 16% yield. The lower yield of 3a in this reaction
than in the reaction shown in Scheme 2 may be due to the
presence of 1-adamantlyisocyanide. It is considered that an
ASSOCIATED CONTENT
* Supporting Information
■
S
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.or-
glett.7b03825.
Experimental procedures and detailed characterizeation
data for the compounds (PDF)
Accession Codes
CCDC 1816018 contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge
via www.ccdc.cam.ac.uk/data_request/cif, or by emailing data_
request@ccdc.cam.ac.uk, or by contacting The Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB2
1EZ, U.K.; fax: +44 1223 336033.
AUTHOR INFORMATION
Corresponding Authors
■
*E-mail: arisawa@m.tohoku.ac.jp (M. Arisawa).
C
DOI: 10.1021/acs.orglett.7b03825
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
M.; Onoda, M.; Hori, C.; Yamaguchi, M. Tetrahedron Lett. 2006, 47,
5211.
(12) Choi, K. S.; Akiyama, I.; Hoshino, M.; Nakayama, J. Bull. Chem.
*E-mail: yama@m.tohoku.ac.jp (M. Yamaguchi).
ORCID
Soc. Jpn. 1993, 66, 623.
Mieko Arisawa: 0000-0002-9561-2653
Debayan Sarkar: 0000-0003-2221-2912
Masahiko Yamaguchi: 0000-0003-3965-7598
Present Address
†Department of Chemistry, National Institute of Technology,
Rourkela, Odisha 769008, India.
(13) The synthesis of benzodithiophospholes was reported by the
reaction of 1,2-benzenedithiol and dichlorophenylphosphine. See:
(a) Ogawa, S.; Saito, M.; Ogasawara, M.; Sato, R. Heterocycles 1995,
41, 889. (b) Sau, A. C.; Holmes, R. R. J. Organomet. Chem. 1978, 156,
253. (c) Campbell, I. G. M.; Way, J. K. J. Chem. Soc. 1960, 0, 5034.
(14) 31P-NMR of 10 was reported δ 57.18 (d, J = 134.2 Hz). See:
James, B. R.; Mahajan, D. Can. J. Chem. 1979, 57, 180.
(15) Coupling constant with rhodium and phosphorus ca. 20 Hz is
known for PP π-coordinated rhodium complex. See: Barbaro, P.;
Ienco, A.; Mealli, C.; Peruzzini, M.; Scherer, O. J.; Schmitt, G.; Vizza,
Notes
The authors declare no competing financial interest.
́
F.; Wolmershauser, G. Chem. - Eur. J. 2003, 9, 5195.
ACKNOWLEDGMENTS
(16) Previously, we reported that dithiorhodium complex was formed
from elemental sulfur and RhH(dppe)2. See: Arisawa, M.; Ichikawa,
T.; Yamaguchi, M. Chem. Commun. 2015, 51, 8821.
■
This research was supported by the Platform Project for
Supporting Drug Discovery and Life Science Research funded
by Japan Agency for Medical Research and Development
(AMED), JSPS KAKENHI (Grant Nos. 17K19112 and
15H00911), Tohoku University Center for Gender Equality
Promotion (TUMUG), and Morinomiyako Project for
Empowering Women in Research.
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DOI: 10.1021/acs.orglett.7b03825
Org. Lett. XXXX, XXX, XXX−XXX