Transformations of benzothiadiphosphole system: General one-pot synthesis of 1,2,5-dithiaphosphepines and their precursor phosphanethiols

Article abstract of DOI:10.1002/hc.20099

Treatment, at room temperature, of benzothiadiphosphole 1 with BrMg(CH ₂)₅MgBr gives intermediate A, which was allowed to stand for about 3 h at room temperature. The subsequent addition of RMgX to the reaction mixture and the final

Full text of DOI:10.1002/hc.20099

Heteroatom Chemistry
Volume 16, Number 5, 2005
Transformations of Benzothiadiphosphole
System: General One-Pot Synthesis of
1,2,5-Dithiaphosphepines and Their
Precursor Phosphanethiols
Graziano Baccolini,1 Carla Boga,1 Marzia Mazzacurati,1
and Magda Monari2
1Dipartimento di Chimica Organica, Universita` di Bologna, Viale Risorgimento 4, I-40136
Bologna, Italy
2Dipartimento di Chimica ‘G. Ciamician’, Via Selmi 2-40126, Bologna, Italy
Received 9 November 2004; revised 11 January 2005
interest. In fact, recently, attention has increasingly
ABSTRACT: Treatment, at room temperature, of ben-
been paid to the coordination chemistry of polyden-
tate ligands incorporating both thiolate and tertiary
zothiadiphosphole 1 with BrMg(CH2)5MgBr gives in-
termediate A, which was allowed to stand for about
3 h at room temperature. The subsequent addition
of RMgX to the reaction mixture and the final treat-
phosphine groups, also known as S P S pincer lig-
ꢀ
C
ands.
2005 Wiley Periodicals, Inc. Heteroatom Chem
16:339–345, 2005; Published online in Wiley InterScience
(www.interscience.wiley.com). DOI 10.1002/hc.20099
ment with an excess of S and water affords the dithi-
8
aphosphepine sulfide 8 in good yields. The structure
of this new heterocyclic system, containing both an
S S unit and a P S group, is confirmed by an single
crystal X-ray structure determination. If the reaction
is carried out without final treatment with sulfur we
obtain, using PhMgBr as mono-Grignard reagent, the
corresponding ring-opened product 11b, which can be
easily transformed into the corresponding ring-opened
sulfide 12b by simple treatment with elemental sul-
fur. Further addition of sulfur to 12b gives quanti-
tatively the cyclic dithiaphosphepine sulfide 8b. The
two phosphanethiols 11b and 12b are of considerable
INTRODUCTION
The facile synthesis of heterocyclic systems contain-
ing phosphorus is of considerable current interest,
principally because they play a central role in coor-
dination chemistry and homogeneous catalysis [1].
In addition, cyclic systems containing both phospho-
rus and sulfur should be particularly interesting as
bidentate or polydentate ligands but this type of com-
pounds has received much less attention. Recently, in
a communication we reported [2] a simple synthesis
of the first examples of a new heterocyclic system,
namely 11H-dibenzo[c,f][1,2,5]dithiaphosphepine,
containing in a seven-membered ring an S S unit
and a P S group. Now, in this paper, we report fur-
ther details of this new procedure to obtain new
derivatives of this heterocyclic system and an X-
ray crystallographic study confirming the structure
Correspondence to: G. Baccolini; e-mail: baccolin@ms.fci.
unibo.it.
Contract grant sponsor: University of Bologna.
Contract grant number: A.A 2003-2004.
Contract grant sponsor: Consiglio Nazionale delle Ricerche
(CNR-Roma).
Contract grant sponsor: Ministero della Ricerca Scientifica e
Tecnologica (MURST).
c
ꢀ
2005 Wiley Periodicals, Inc.
339

340 Baccolini et al.
previously proposed. In addition we found that it is
possible to obtain in a similar manner in one-pot
synthesis also PhP(p-MeC6H3-SH-2)2, (11b) and its
sulfide PhPS(p-MeC6H3-SH-2)2 (12b), which are the
ring-opened precursors of the above heterocyclic sys-
tem containing the S S unit. Compounds 11 and 12
are of considerable interest because recently atten-
tion has increasingly been paid to the coordination
chemistry of polydentate ligands incorporating both
thiolate and tertiary phosphine donor sites, as their
combination is likely to confer unusual structures
and reactivities on their metal complexes [3].
for the one-pot preparation of secondary cyclic phos-
phanes 5 (n = 1, 2) in 70–80% yields. This method
consists in the treatment at room temperature of
reagent 1 with one equivalent of bis-Grignard 2.
Treatment of the reaction mixture with acidic water
gave secondary cyclic phosphanes 5 (70–80% yields)
and the end product 6 (90% yields) which is the
residue of reagent 1. The separation of 5 from 6 can
be performed by simple acid/base extraction or by
distillation. Simple treatment of 6 with PCl3 regen-
erates quantitatively and immediately the starting
reagent 1, which can be reused without further pu-
rification. The same end product 6 can be recovered
also from the final reaction mixture obtained when
we prepare phosphanes 3.
RESULTS AND DISCUSSION
The general synthesis of cyclic tertiary and sec-
ondary phosphanes reported in Scheme 1 is an atom-
economic [8] and environmentally friendly method-
ology because the by-product 6 is easily transformed
into the starting reagent 1.
In the past years, we reported [4] that benzoth-
iadiphosphole 1 is easily obtained by an unexpected
domino reaction treating p−methylthioanisole with
PCl3 and AlCl3. Compound 1 was separated by sim-
ple crystallization from the reaction mixture [4b, 6b].
It is an air-stable solid which can be stored for sev-
eral years without particular precaution and thus it
is easy to handle. Subsequently, we found [5a] that
compound 1 can be used as a phosphorus-donating
reagent for obtaining diazaphosphole [5b] deriva-
tives by the reaction of 1 with azalkenes.
Recently, we reported [6] that the simultaneous
or the sequential addition of equimolar amounts
of a bis-Grignard 2 (n = 1, 2) and a mono-Grignard
RMgBr (R = alkyl, phenyl, alkenyl) to one equiva-
lent of 1 give phosphanes 3 or, after addition of ele-
mental sulfur, their sulfides 4 in good yields at room
temperature (Scheme 1). More recently [7], we have
reported a very efficient and economic new method
These results were tentatively explained by the
intervention of hypervalent phosphorus intermedi-
ates [9] such as A and B (Scheme 2) in which the
“dibenzo-butterfly” moiety of reagent 1, as depicted
in Scheme 1, might favor their formation. In inter-
mediate A, the coordination of the Mg atom to sulfur
would activate the P1 atom to undergo the final nu-
cleophilic attack giving a very unstable intermediate
B (or its isomeric forms) that immediately collapses
to the final phosphanic product. It should be noted
that only in the second step we can use a nucleophilic
reagent such as a sodium alcoholate or thiolate giv-
ing the corresponding cyclic phosphane derivatives
7 (see Scheme 1). But sodium alcoholate or thiolate
SCHEME 1

Transformations of Benzothiadiphosphole System 341
giving a very complex mixture of alkylphosphanes;
this work is still in progress.
It should be noted that the end product, phos-
phane sulfide D, was supposed [2] and never iso-
lated but the subsequent isolation of phosphane 6
also confirms D.
Recently, in order to find further information
about this reaction, we have observed a new type of
transformation which occurs when the intermediate
A reacts with RMgBr with high steric hindrance of
the R group (Scheme 3). In these cases (cases a, c, d),
we have the prevalent formation [2] of the new het-
erocyclic compounds 8 (75–80%) with the concomi-
tant formation of cyclic phosphane sulfides 9. When
RMgX is sterically less demanding (case b) and the
intermediate A was allowed to stand for about 3 h at
room temperature before the reaction with RMgBr,
we have the formation of both 8 and 4 in a ratio
depending on the reaction time of the first step of
the reaction with the formation of intermediate A.
In fact, when PhMgBr is immediately added to A we
have only 4b while when we added PhMgBr to A af-
ter about 3 h at ambient temperature we also found
8b in 50% yield. This fact indicates that the pathway
for formation of 8 is more complex than the one for
explaining the formation of 4.
SCHEME 2
Presumably the new intermediate might be the
isomeric ionic form Aꢁ (Scheme 4) which might ex-
plain the inversion of reactivity of the two P atoms.
In this manner, the nucleophilic attack of the second
reagent can occur on the P2 atom which is now a
very reactive phosphenium ion [12]. After this attack
and addition of S8 and water, the P1 phosphoranide
[13], an unstable hypervalent species, collapses to
form compounds 8 and 9. The decomposition path-
way is still unclear. A possibility is the formation of
phosphanethiols such as 11 and 12 and their subse-
quent oxidation by S8, as reported in Scheme 3 and
explained below.
cannot be used in the first step of this reaction. In
fact, we have found that reaction of several alcoho-
lates as RONa with 1 does not give in appreciable
amount the corresponding phosphite (RO)3P.
This observation may be in agreement with our
hypothesis that in the first step, the reaction of a bis-
Grignard reagent with 1 may not be a conventional
[10] double SN2 substitution, which would give the
expected form C, but might prefer to give the inter-
mediate A with a hypervalent phosphorus atom as
shown in Scheme 2. In the intermediate A, the forma-
tion of another additional ring around the P1 atom,
obtained by attack of the bis-Grignard, is a factor of
further stability. In fact, when the reaction is carried
out with simultaneous addition of a bis-Grignard
reagent and mono-Grignard (RMgX) in equimolar
amount, we have the almost exclusive formation of
cyclic phosphanes 3 without acyclic PR3 which, for
three simple SN2 reactions, would be favored. This
observed favored cyclization might be in accord with
a hypervalent intermediate in which the formation
of a cyclic form is favored by a large factor (105–108)
with respect to an acyclic form [11]. When we use
only mono-Grignard reagents we have different re-
sults. In fact, the use of mono-Grignards also in the
first step does not form a ring around the phosphorus
and, consequently, causes instability of the interme-
diate A which might be transformed into the form C
In a similar manner we obtained the 11-alkoxy
derivatives 8e,f using alcoholates as nucleophilic
reagents.
Compounds 8 represent the first examples
of derivatives with a new heterocyclic system,
namely 11H-dibenzo[c,f][1,2,5] dithiaphosphepine
11-thione derivatives. The only related compound
reported in the literature [14] is the 11-phenyl-11-
oxo-derivative, obtained by a two-step procedure
from lithium 2-lithiobenzenethiolate at −78◦C
with phenylphosphonic dichloride. Then the 2-
mercaptophenyl phosphane oxide obtained is oxi-
dized to the cyclic disulfide by DMSO at 90◦C. It is
clear that with this reported procedure it is neces-
sary to use, for every cyclic disulfide, various RPOCl2
reagents, which are very difficult to prepare when R

342 Baccolini et al.
SCHEME 3
is a simple alkyl group. On the other hand, in our
case, it is possible to obtain compounds 8 bearing
several R or ORꢁ groups only using different mono-
Grignard reagents or sodium alcoholates in a one-pot
two-step procedure carried out at room temperature.
With the purpose to check whether our new
method to obtain dibenzo[c,f][1,2,5]dithiaphos-
phepine 11-thione derivatives can be generalized,
we carried out the reaction using mono-Grignard
reagents RMgBr having not relevant steric hin-
drance, namely n-butyl- and n-pentyl-magnesium
bromide (cases g,h). Also in these cases, we ob-
tained the corresponding products 8g and 8h,
thus confirming the possibility to prepare, through
this new synthetic approach, a wide number of
dithiaphosphepines.
Compound 8b (Fig. 1) contains an unusual
seven-membered heterocycle in which a phospho-
rus and two sulfur atoms forming an S S bond are
present. The molecule is asymmetric, and the central
heterocycle is rather distorted, presumably in order
to optimize the bonding interactions. The S S dis-
˚
tance [2.033(2) A] is comparable to that found in S8
˚
˚
[2.059 A], and the P S distance [1.936(2) A] indi-
cates double bond order. To the best of our knowl-
edge, only one other compound showing a similar
seven-membered ring has been reported in the liter-
ature: [OPS3]2, where PS3 = [P(C6H4-2-S)3] [15] (see
Fig. 2). In the latter case, the molecule is dimeric and
the phosphorus atoms are oxidized.
In order to confirm unequivocally the structure
of these new series of heterocyclic compounds by X-
rays diffraction, we repeated the reaction to prepare
compound 8b and were able to obtain suitable crys-
tals for a single crystal X-ray diffraction study.
SCHEME 4
FIGURE 1 ORTEP drawing of 8b

Transformations of Benzothiadiphosphole System 343
by the observation of unusual structures containing
a “dibenzo-butterfly” moiety, very similar to our
intermediate A, in the resulting transition metal
complexes [3].
EXPERIMENTAL
General
1H, 13C, and 31P NMR spectra were recorded on a
Varian Gemini 300 (or Inova 400) spectrometer at
300 (or 400) MHz, 75.46 (or 100.56) MHz, and 121.47
(or 161.90) MHz, respectively, in CDCl3. Chemical
shifts are referenced to internal standard TMS (1H
NMR), to solvent (77.0 ppm for 13C NMR), and to
external standard 85% H3PO4 (31P NMR). J values
are given in Hz. Multiplicities were obtained from
DEPT experiments (the symbols used are as fol-
lows: (+) for CH and CH3, (−) for CH2) I.R. spec-
tra were recorded on a Perkin-Elmer spectrome-
ter model 1600 FT-IR. MS spectra were recorded
at an ionization voltage of 70 eV on a VG 7070
E spectrometer. GC-MS analyses were performed
on a HP-5890 gas chromatograph equipped with a
methyl silicone capillary column and an HP-5970
mass detector. Thin-layer chromatography was per-
formed on Merck Kieselgel 60 F254. Melting points
were measured with a Bu¨ chi apparatus and are
uncorrected. THF was distilled from sodium ben-
zophenone ketyl. All Grignard reagents used, both
commercially available and prepared from the corre-
sponding alkyl halide and magnesium turnings, were
titrated immediately prior to use by standard meth-
ods [16]. 2-Chlorophenylmagnesium iodide (for the
synthesis of compound 8c) was prepared by adding
dropwise, at −30◦C, an equimolar amount of iso-
propylmagnesium chloride to a solution of 1-chloro-
2-iodobenzene in anhydrous THF and keeping this
solution at −30◦C for 60 min. Air and moisture
sensitive solutions and reagents were handled in
a dried apparatus under an atmosphere of dry
nitrogen.
FIGURE 2 Representation of structure of compound re-
ported in literature [15] as [OPS3]2.
With the aim to obtain compound 10b, which
is the phosphinic form of 8b, we have carried out
the reaction in a similar manner but without the fi-
nal treatment with sulfur. The final reaction mixture
was treated with aqueous acid to recover also the sec-
ondary cyclic phosphane 5 (n = 2), but surprisingly
we obtained the phosphanethiol 11b together with
phosphane 5, which can be completely purified by
bulb-to-bulb distillation. Compound 11b was sepa-
rated from the residue by column chromatography
and obtained in 50% yield. Compound 10b was not
obtained. Small amounts of 3 (R=Ph) and 6 were
also observed.
When we treated compound 11b with a stoi-
chiometric amount of elemental sulfur, we obtained
quantitatively the corresponding sulfide 12b which
was completely characterized. Further treatment of
12b with sulfur gave the heterocyclic compound 8b.
In addition, we found that compounds 11b and
12b, when analyzed by GC-MS, showed mainly the
presence of compounds 10b and 8b, respectively,
thus revealing a probable oxidation reaction from
the thiolic to the disulfidic form in the mass injec-
tor. From this result, we hope to find other reaction
conditions to obtain also 10b.
The importance of this new simple route to
phosphanylthiols suggests us to try to synthesize
also alkyl derivatives, which probably are less stable
than the phenyl ones: work is still in progress to this
objective.
In conclusion, with these new transformations of
compound 1, it is possible to have a general method
to produce the 1,2,5-dithiaphosphepinic system
and to also obtain its precursor phosphanethiols
11b and 12b, which are known as pincer ligands.
Recently, the chemistry of this kind of S P S pincer
ligands has attracted increasing interest, augmented
Typical Procedure for the Synthesis
of Compounds 8
A solution of BrMg(CH2)5MgBr (2, 1.0 mmol) in THF
was added dropwise under dry nitrogen atmosphere
to a solution of 1 (1.0 mmol) in THF (15–25 mL)
at room temperature. The mixture was stirred for
30 min and allowed to stand for an additional
150 min, always at room temperature. A solution of
mono-Grignard reagent (1.1 mmol) (or alcoholate,
2.0 mmol) was then added. The reaction mixture was
allowed to stand for 25 h at room temperature then

344 Baccolini et al.
treated with elemental sulfur (2.0 mmol) for 60 min,
quenched with water and extracted with CH2Cl2. The
organic layer was dried over anhydrous sodium sul-
fate and concentrated “in vacuo.” Compounds 8 were
isolated by FC on a silica gel column. According to
spectral data their purity is higher than 98%. Char-
acterization data for compounds 8a,c,d,e,f were re-
ported previously [2].
7.42–7.20 (m, 9H), 2.43 (s, 6H, CH3); δC (75.56 MHz,
CDCl3): 139.8 (d, J = 70.1 Hz), 139.5 (d, J = 12.8 Hz,
(+)), 139.1 (d, J = 13.1 Hz), 139.0 (d, J = 7.4 Hz),
133.7 (d, J = 83.0 Hz), 132.8 (d, J = 2.9 Hz, (+)),
131.3 (d, J = 8.9 Hz, (+)), 130.7 (d, J = 3.3 Hz, (+)),
130.3 (d, J = 11.3 Hz, (+)), 128.3 (d, J = 13.3 Hz,
(+)), 21.3 (+); δP (121.47 MHz, CDCl3): 49.0; MS
(m/z, %): 384 (M+, 59), 352 (14), 320 (74), 275 (70),
243 (100), 211 (51), 185 (62); IR, ν (cm−1): 488
(S S), 690 and 745 (P S), 1100 (PC), 1583; HRMS
calcd. for C20H17PS3: 384.0230, found: 384.0221.
Crystal structure of 8b: C20H17PS3, Fw = 384.49,
monoclinic, space group Cc, a = 9.351(2), b =
2,9-Dimethyl-11-(butyl)-11H11ꢀ5-dibenzo[c,f]-
[1,2,5]dithiaphosphepine-11-thione (8g). Greasy
solid, 35% yield, R = 0.44 (petroleum light: dichlo-
f
romethane 2:1); δH (300 MHz, CDCl3): 8.74 (dd,
2H, JP−H = 17.0 Hz, JH−H = 2.2 Hz), 7.36 (dd, 2H,
J = 7.5 Hz, J = 4.4 Hz), 7.26–7.16 (m, 2H), 2.85–
2.70 (m, 2H), 2.45 (s, 6H, CH3), 2.40–1.40 (m, 4H),
0.90–0.70 (m, 3H); δC (75.56 MHz, CDCl3): 139.8
(d, J = 12.2 Hz, (+)), 139.3 (d, J = 12.4 Hz), 138.2
(d, J = 5.8 Hz), 133.7 (d, J = 75.6 Hz), 132.4 (d,
J = 2.4 Hz, (+)), 131.3 (d, J = 8.9 Hz, (+)), 40.1 (d,
J = 56.0 Hz, (−)), 24.2 (d, J = 3.4 Hz, (−)), 23.4
(d, J = 18.1 Hz, (−)), 21.3 (+), 13.6 (+); δP (121.47
MHz, CDCl3): 53.7; MS (m/z, %): 364 (M+, 25), 331
(25), 308 (30), 275 (100), 243 (50), 211 (18), 185 (21);
IR, ν (cm−1): 617, 728, 1111, 1450, 1583; HRMS
calcd. For C18H21PS3: 364.0543, found: 364.0541.
16.050(3), c = 12.474(3) A, β = 102.93(3)◦, V =
˚
3
3
˚
1824.5(6) A , Z = 4, D = 1.400 mg/m , ꢁ(Mo Kꢂ) =
0.493 mm−1, R = 0.0348, [I > 2σ(I)], absolute struc-
1
ture parameter = 0.05(11), Rw = 0.0911 (all data),
GOF = 1.002.
CCDC 254796 contains the supplementary crys-
tallographic data for this paper. These data can be ob-
tained free of charge via www.ccdc.cam.ac.uk/conts/
retrieving.html (or from the Cambridge Crystallo-
graphic Data Centre, 12, Union Road, Cambridge
CB2 1EZ, UK; fax: +44 1223 336033; or deposit@
ccdc.cam.ac.uk).
Synthesis of Compounds 11b and 12b
2,9-Dimethyl-11-(pentyl)-11H-11ꢀ5-dibenzo[c,f]-
[1,2,5]dithiaphosphepine-11-thione (8h). Greasy
A solution of BrMg(CH2)5MgBr (2, 1.0 mmol) in
THF was added dropwise under a dry nitrogen atmo-
sphere to a solution of 1 (1.0 mmol) in THF (15–25
mL) at room temperature. The mixture was stirred
for 30 min and allowed to stand for an additional
150 min at room temperature. A solution of phenyl-
magnesium bromide (1.1 mmol) was then added.
The reaction mixture was allowed to stand for 25 h
at room temperature then treated with aqueous acid
and extracted with CH2Cl2. The organic layer was
dried over anhydrous sodium sulfate and concen-
trated “in vacuo.” Compound 11b was isolated by
FC on a silica gel column (eluent: petroleum light:
dichloromethane 2:1). It contains small amounts
(about 3%) of its oxide 13b, probably formed dur-
ing the work-up and/or the chromatographic purifi-
cation process. The oxide 13b was characterized only
solid, 45% yield, R = 0.44 (petroleum light: dichlo-
f
romethane 2:1); δH (300 MHz, CDCl3): 8.74 (dd, 2H,
JP−H = 16.3 Hz, JH−H = 1.6 Hz), 7.37 (dd, 2H, J = 7.8
Hz, J = 4.7 Hz), 7.25–7.16 (m, 2H), 2.80–2.62 (m,
2H), 2.45 (s, 6H, CH3), 1.70–1.00 (m, 4H), 0.98–0.88
(m, 2H), 0.83–0.74 (m, 3H); δC (75.56 MHz, CDCl3):
139.8 (d, J = 12.2 Hz, (+)), 139.3 (d, J = 12.2 Hz),
138.2 (d, J = 5.4 Hz), 133.8 (d, J = 75.7 Hz), 132.4
(d, J = 3.2 Hz, (+)), 131.4 (d, J = 9.1 Hz, (+)), 40.2
(d, J = 55.6 Hz, (−)), 32.4 (d, J = 17.8 Hz, (−)),
22.1 (−), 22.0 (d, J = 3.6 Hz, (−)), 21.4 (+), 13.9
(+); δP (121.47 MHz, CDCl3): 53.6; MS (m/z, %): 378
(M+, 24), 345 (30), 308 (32), 275 (100), 243 (31), 211
(16), 185 (25); IR, ν (cm−1): 613, 717, 1117, 1456,
1583; HRMS calcd. For C19H23PS3: 378.0700, found:
378.0698.
1
by H, 31P NMR, and MS spectroscopy as reported
below.
Physical and Crystallographic Data of 11-(Phe-
nyl)-2,9-dimethyl-11H-11ꢀ5 -dibenzo[c,f][1,2,5]di-
thiaphosphepine-11-thione(8b). The reaction was
carried out following the typical procedure de-
scribed above. Compound 8b was obtained in
50% yield, mp: 162–164◦C (from dichloromethane)
Treatment of a solution of 11b in dichlorome-
thane with an equimolar amount of elemental sulfur
gave quantitatively the corresponding sulfide 12b,
which was isolated and fully characterized. Further
addition of sulfur to this solution gave formation
of compound 8b. Also when the solution contain-
ing pure 11b was treated with a large excess of el-
R = 0.45 (petroleum light: dichloromethane 2:1); δH
f
3
1
(300 MHz, CDCl3): 8.58 (dm, 2H, JP−H = 16.6 Hz),
emental sulfur, the reaction, monitored by H NMR

Transformations of Benzothiadiphosphole System 345
analysis, showed the presence of both 12b and 8b,
with gradual decreasing of 12b and the parallel in-
creasing of 8b until the presence of the latter alone.
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4-Methyl-2-[(5-methyl-2-sulfanylphenyl)(phenyl)-
phosphino]benzenethiol(11b). 50% yield, Rf = 0.10
(petroleum light: dichloromethane 1:2); δH (400
MHz, CDCl3): 7.42–7.34 (m, 3H), 7.32–7.24 (m, 4H),
7.08–7.03 (m, 2H), 6.61–6.57 (m, 2H), 3.94 (d, 2H,
J = 1.3 Hz, disappears after addition of D2O), 2.17
(s, 6H); δC (100.56 MHz, CDCl3) (selected data):
136.0, 134.7 (d, J = 6.5 Hz), 134.4 (+), 134.2 (d,
J = 20.2 Hz, (+)), 130.9 (d, J = 3.2 Hz, (+)), 130.5
(+), 129.2 (+), 128.8 (d, J = 7.3 Hz, (+)), 21.1 (+); δP
(161.90 MHz, CDCl3): −18.3; MS (m/z, %): 353 (M+
−1, 2), 352 (9), 320 (6), 243 (100), 211 (17); IR, ν
(cm−1): 696, 746, 807, 1038, 1111, 1263, 1434, 1453,
2487, 2547; HRMS calcd. for C20H19PS2: 354.0666,
found: 354.0662.
4-Methyl-2-[(5-methyl-2-sulfanylphenyl)(phenyl)-
phosphorothioyl]benzene Thiol (12b). mp: 169–
171◦C (from dichloromethane), quantitative yield
from 11b, R = 0.30 (petroleum light: dichloro-
f
[7] Baccolini, G.; Boga, C.; Galeotti, M. Angew Chem, Int
Ed 2004, 43, 3058–3060.
methane 1:2); δH (400 MHz, CDCl3): 7.80 (dd,
2H, J = 13.7 Hz, J = 7.1 Hz), 7.64–7.44 (m, 3H),
7.38–7.28 (m, 2H), 7.22–7.14 (m, 2H), 6.95 (dd, 2H,
J = 15.2 Hz, J = 1.3 Hz), 6.13 (s, 2H, disappears
after addition of D2O), 2.18 (s, 6H); δC (100.56
MHz, CDCl3): 135.3 (d, J = 7.3 Hz), 135.0 (d,
J = 11.3 Hz), 134.6 (d, J = 11.3 Hz, (+)), 133.2 (d,
J = 10.5 Hz, (+)), 133.0 (d, J = 9.7 Hz, (+)), 132.8
(d, J = 2.4 Hz, (+)), 132.1 (d, J = 3.2 Hz, (+)), 129.4
(d, J = 86.6 Hz), 128.6 (d, J = 13.0 Hz, (+)), 127.4
(d, J = 89.1 Hz), 21.0 (+); δP (161.90 MHz, CDCl3):
44.5; MS (m/z, %): 386 (M+, 12), 385 (20), 384 (80),
352 (10), 320 (100), 275 (97), 243 (86), 185 (85);
IR, ν (cm−1): 692, 715, 730, 814, 905, 1118, 1267,
1380, 1434, 1464, 2373; HRMS calcd. for C20H19PS3:
386.0387, found: 386.0384.
[8] Trost, Barry M. Acc Chem Res 2002, 35, 695–705.
[9] The formation of the intermediate A was observed
by 31P NMR spectroscopy as reported previously
in [6b]. For reviews on pentacoordinated phospho-
rus and similar hypervalent phosphorus compounds
see: (a) Holmes, R. R. Pentacoordinated Phosphorus
Structure and Spectroscopy, ACS Monograph 175;
American Chemical Society: Washington, DC, 1980.
Vols. I and II; (b) Holmes, R. R. Acc Chem Res 1998,
31, 535–542; (c) Arduengo, A. J. III; Stewart, C. A.
Chem Rev 1994, 94, 1215–1237.
[10] There are indications that free radical may be in-
volved in reactions with Grignard reagents, see:
Hoffman, R. W. Chem Soc Rev 2003, 32, 225–230.
[11] Holmes, R. R. Pentacoordinate Phosphorus, Vol II,
ACS Monograph 176; American Chemical Society:
Washington, DC, 1980; Ch. 2, pp. 91–105.
[12] For a review about phosphenium ions see: Cowley,
A. H.; Kempt, R. A. Chem Rev 1985, 85, 367–382.
[13] For a review about phosphoranides see: Dillon, K. B.
Chem Rev 1994, 94, 1441–1456.
[14] Block, E.; Ofori-Okai, G.; Zubieta, J. J Am Chem Soc
1989, 111, 2327–2329.
[15] Clark, K. A.; George, T. A.; Brett, T. J.; Ross II, C. R.;
Shoemaker, R. K. Inorg Chem 2000, 39, 2252–2253.
[16] Bergbreiter, D. E.; Pendergrass, E. J Org Chem 1981,
46, 219–220.
4-Methyl-2-[(5-methyl-2-sulfanylphenyl)(phenyl)-
phosphoryl]benzenethiol (13b). δH (400 MHz,
CDCl3): 7.70–7.05 (m, 9H), 6.79 (d, 2H, J = 14.3 Hz),
5.95 (s, 2H, disappears after addition of D2O), 2.19
(s, 6H); δP (161.90 MHz, CDCl3): 39.0; MS (m/z, %):
370 (M+, 11), 369 (25), 368 (100), 335 (13), 259 (63),
244 (18), 211 (22).