A convenient procedure for the preparation of 1-(diisopropylamino)phospholes - Application to the synthesis of new 2,2′-biphosphole disulfides

Article abstract of DOI:10.1002/1099-0690(200202)2002:4<675::AID-EJOC675>3.0.CO;2-Z

A convenient one-pot procedure for the preparation of 1-(diisopropylamino)phospholes has been developed. These phospholes have been used in a multistep procedure for synthesizing two new 2,2′-biphosphole disulfide compounds. The structures and stereochemistry of these compounds have been studied by X-ray diffraction analysis and by molecular modeling. The 1-(diisopropylamino) group, used as a bulky substituent on the phosphorus atom in combination with a phenyl group on the ring, proved to be an important factor in the stabilization of the axial chirality of 2,2′-biphosphole framework.

Full text of DOI:10.1002/1099-0690(200202)2002:4<675::AID-EJOC675>3.0.CO;2-Z

FULL PAPER
A Convenient Procedure for the Preparation of 1-(Diisopropylamino)phospholes
؊ Application to the Synthesis of New 2,2Ј-Biphosphole Disulfides
[a]
[a]
[b]
[a]
´ ˆ
´ ´
Jerome Hydrio, Maryse Gouygou,* Frederic Dallemer, Gilbert G. A. Balavoine, and
Jean-Claude Daran*[a]
Keywords: Chirality / 2,2Ј-Biphosphole / Phosphanes / 1-(Diisopropylamino)phosphole
A convenient one-pot procedure for the preparation of 1-(di-
isopropylamino)phospholes has been developed. These pho- substituent on the phosphorus atom in combination with a
spholes have been used in a multistep procedure for synthes- phenyl group on the ring, proved to be an important factor
modeling. The 1-(diisopropylamino) group, used as a bulky
izing two new 2,2Ј-biphosphole disulfide compounds. The in the stabilization of the axial chirality of 2,2Ј-biphosphole
structures and stereochemistry of these compounds have framework.
been studied by X-ray diffraction analysis and by molecular
Concentrating our investigations on 2,2Ј-biphosphole
ligands and their use in asymmetric catalysis, we were inter-
ested in the design and syntheses of new compounds pos-
Introduction
Chiral diphosphane ligands, especially the C2-symmetric sessing stable axial chirality. We decided to introduce bulky
diphosphanes, play an important role as chiral auxiliaries substituents such as the diisopropylamino group at position
in catalytic asymmetric processes.[1] Since the preparation 1, and different alkyl or aryl substituents at positions 3 and
of DIOP by Kagan in 1971,[2] numerous C2-symmetric di- 4 on the 2,2Ј-biphosphole framework (Scheme 1), in order
phosphanes have been synthesized. Different sources of to prevent free rotation around the CϪC bond linking the
chirality have been exploited for the design of these diphos- two phosphole rings. Moreover, the diisopropylamino
phanes; the centers of chirality (carbon centers as in group, which exhibits different electronic effects with re-
DIOP[2] or phosphorus centers as in DIPAMP[3]), axial spect to the phenyl group in position 1 in BIPHOS, may
chirality as in BINAP,[4] and planar chirality as in also enhance the pyramidal inversion barrier of the phos-
Phanephos.[5] Sometimes several sources of chirality are phorus atom.[12]
combined within the same molecule, as in BIPNOR,[6] in
which stereocenters are located on carbon and phosphorus
atoms, or in TRAP,[7] with both central and planar chirality.
In 1994, we began to focus our attention on C2-symmet-
ric diphosphanes incorporating two sources of chirality.
Our first studies were based on a bidentate ligand combin-
ing both central and axial chirality, the 3,3Ј,4,4Ј-tetra-
Scheme 1. 2,2Ј-Biphosphole framework
methyl-1,1Ј-diphenyl-2,2Ј-biphosphole (BIPHOS) first syn-
thesized by F. Mathey.[8] We first demonstrated that this
chiral diphosphane, which is an efficient ligand for trans-
ition metal ions,[9] is stereolabile in solution.[10] However,
we have since been able to obtain BIPHOS complexes in
stable enantiomerically pure form,[11] and this new family
of complexes proved to be effective in asymmetric catalysis.
For the goal of obtaining new 1,1Ј-bis(diisopropylam-
ino)-2,2Ј-biphospholes, a simple and versatile method for
syntheses of 1-(diisopropylamino)-substituted monophos-
phole precursors in high yields was desirable. As the avail-
able synthetic route to these compounds, restricted to 1-
(diisopropylamino)-3,4-dimethylphosphole,[13] involved
a
rather complicated multistep procedure and proceeded in
rather low yield, we attempted to develop a new method for
preparing 1-(diisopropylamino)phosphole moieties.
Here we report a convenient one-pot procedure for the
preparation of various 1-(diisopropylamino)phospholes
2a,b and their use in the synthesis of new 2,2Ј-biphosphole
disulfides 8a,b and one free 2,2Ј-biphosphole 10a. The
structures and stereochemistry of the disulfide compounds
[a]
Laboratoire de Chimie de Coordination du CNRS,
205, Route de Narbonne, 31077 Toulouse Cedex, France
Fax: (internat.) ϩ 33-5/61553003
E-mail: gouygou@lcc-toulouse.fr
daran@lcc-toulouse.fr
Rhodia Recherches, Centre de Recherche de Lyon, 85
[b]
Avenue des Freres Perret, BP 62, 69192 Saint-Fons Cedex,
France
Eur. J. Org. Chem. 2002, 675Ϫ685
WILEY-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002 1434Ϫ193X/02/0204Ϫ0675 $ 17.50ϩ.50/0
675

J. Hydrio, M. Gouygou, F. Dallemer, G. G. A. Balavoine, J.-C. Daran
FULL PAPER
have been studied by X-ray diffraction analysis and by mo- amide base such as LDA or LiHMDS, and the correspond-
lecular modeling.
ing phospholes 2a and 2b were obtained in 68% and 84%
yields, respectively (Scheme 3). In the case of 1c, the dehy-
drohalogenation reaction was unsuccessful, possibly be-
cause the bulky substituents in 1c might have prevented de-
protonation by the amide base. The 3,4-di-tert-butyl-1-di-
isopropylamino-3-phospholene oxide probably resulted
from hydrolysis of the phospholenium ion (Scheme 4) dur-
ing the workup.
Results and Discussion
Synthesis of 1-(Diisopropylamino)phospholes 2
The conventional synthetic routes to the phosphole rings
involve the MacCormack reaction,[14] in which the five-
membered ring is assembled by means of a cycloaddition
reaction between a dichlorophosphane and a 1,3-diene. The
resulting 3-phospholenium salt is then directly or indirectly
dehydrohalogenated to give a phosphole[15] (Scheme 2). The
major problem with this method is that the McCormack
reaction requires several days or weeks to reach completion.
Transient phosphenium ions [(R)(Cl)P]ϩ have, in fact, been
postulated as intermediates in this reaction. On the other
hand, stable phosphenium moieties such as phosphenium
tetrachloroaluminate ions,[16] are known to be good dien-
ophiles and give 1,4-addition reactions with 1,3-butadi-
enes[17] to afford 3-phospholenium tetrachloroaluminates.
However, these compounds have never been used in a syn-
thetic approach to phospholes. We thus investigated reac-
tions between the chlorophosphenium ion [(iPr2N)(Cl)P]ϩ
[18] and various dienes in order to obtain the corresponding
1-chloro-3-phospholenium cations, which might then be de-
hydrohalogenated to give phospholes.
Scheme 3. Synthesis of phospholes 2a,b: i) AlCl3, CH2Cl2, Ϫ78 °C
to room temp.; ii) diene, CH2Cl2, Ϫ20 °C to room temp.; iii)
LiHMDS, THF, Ϫ78 °C to room temp.
Scheme 4. Hydrolysis of phospholenium 1c
The phospholes 2a,b were isolated and fully character-
ized, and the structure of 2a was confirmed by X-ray dif-
fraction analysis (Figure 1). As usually observed in related
molecules,[15b] the phosphole ring adopts an envelope con-
formation. The dihedral angle between the butadiene moi-
ety and the C(1)ϪP(1)ϪC(4) plane is 11.21° (cf. 9.6° for 1-
benzylphosphole[21a] and 13.7° for 4,5-dimethyl-1,2,3-tri-
phenylphosphole[21b]). Thus, the phosphorus atom retains
its slightly pyramidal geometry: Σ(CPC angles) ϭ 306.1°,
similarly to the 1-alkoxyphosphole:[21a] Σ(CPC angles) ϭ
309.5°. It is worth pointing out that the amino group, which
is itself planar, makes a dihedral angle of 91.7° with the
phosphole ring.
Scheme 2. General synthesis of phospholes via 3-phospholenium
compounds
The chlorophosphenium ion [(iPr2N)(Cl)P]ϩ, obtained
by the action of AlCl3 on dichloro(diisopropylamino)phos-
phane,[19] reacted cleanly and rapidly with 2,3-dimethyl-1,3-
butadiene, 2,3-diphenyl-1,3-butadiene, and 2,3-di-tert-bu-
tyl-1,3-butadiene to afford quantitatively the corresponding
3-phospholenium cations 1a (δ31P ϭ 91.30), 1b (δ31P ϭ
88.99), and 1c (δ31P ϭ 76.07) (Scheme 3). The dehydrohalo-
genation of 1 could not be accomplished with nitrogen ba-
ses (such as Et3N or some pyridine derivatives) according
to Mathey’s method.[20] However, the dehydrohalogenation
Figure 1. ORTEP view of molecule 2a with atom labelling scheme;
˚
ellipsoids represent 50% probability; selected bond lengths [A] and
bond angles [°]: P(1)ϪN(1) 1.669(2), P(1)ϪC(1) 1.793(2),
P(1)ϪC(4) 1.797(2); C(1)ϪP(1)ϪN(1) 108.02(8), N(1)ϪP(1)ϪC(4)
of compounds 1a and 1b was readily achieved by use of an 108.50(9), C(1)ϪP(1)ϪC(4) 89.55(8)
676
Eur. J. Org. Chem. 2002, 675Ϫ685

A Convenient Procedure for the Preparation of 1-(Diisopropylamino)phospholes
FULL PAPER
This one-pot sequence thus provides simple and quick observed dimer compounds with smaller substituted amino
access to 1-(diisopropylamino)phospholes in high yield with groups, such as 1-(dimethylamino) or 1-(diethylamino).
respect to iPr2NPCl2. This new procedure afforded a new
1-(diisopropylamino)phosphole 2b, with phenyl groups in
the 3 and 4 positions,[22] and constitutes an efficient altern-
ative route to the synthesis of the 1-(diisopropylamino)-3,4-
dimethylphosphole 2a.[13] Indeed, the synthesis of the phos-
phole 2a via the 3,4-dimethyl-1-phenylphosphole obtained
from a classical McCormack reaction required prolonged
reaction times (12 d) and gave the product in only moderate
yield with respect to PhPCl2 (25Ϫ30%).
Scheme 6. The [4ϩ2] DielsϪAlder cycloadducts were not obtained
from the oxides 3a,b
In the second step, 1,4-bromo addition onto the diene
systems of the phosphole rings, carried out with pyridinium
tribromide, provided compounds 4a,b in high yields
(Scheme 5). In the case of 3a, monitoring of the reaction
mixture by 31P NMR spectroscopy indicated the quantitat-
ive conversion of 3a into a mixture of two stereoisomers,
the major stereoisomer 4aЈ (δ ϭ 36.4) and the minor ste-
reoisomer 4aЈЈ (δ ϭ 38.4), in an 80:20 ratio (Scheme 7).
Synthesis of 1,1ЈBis(diisopropylamino)-2,2Ј-biphospholes 8
In 1992,[23] Mathey reported a convenient route for the
preparation of 2,2Ј-biphosphole, involving the oxidative
coupling reaction of 2-lithiophosphole. The starting point
of this method required the α-functionalization of the phos-
phole ring. By an analogous procedure, we attempted to
synthesize 2,2Ј-biphospholes starting from phospholes 2a,b.
The strategy used was based on a sequence of oxidation at
the phosphorus atom, bromination and dehydrobromin-
ation of the diene system, and finally a coupling reaction
via a 2-lithiophosphole intermediate (Scheme 5).
Scheme 7. Stereoisomers of compounds 4a,b and 5a,b
The separation of these two isomers was difficult. Only
a small amount of 4aЈ could be isolated in pure form by
crystallization of the crude mixture from dichloromethane,
but this allowed a complete characterization. This major
stereoisomer 4aЈ was the result of a 1,4-bromo addition at
the face opposite to that occupied by the iPr2N group. In-
deed, the α-H atoms were trans to the PϭO group (Fig-
2
ure 2), which was consistent with the low JH-P value
1
(2.8 Hz)[23] observed in the H NMR spectrum. The X-ray
crystal structure analysis (Figure 2) clearly shows an envel-
ope conformation for the phospholene ring with a dihedral
angle of 6.23° between the C(1)ϪC(2)ϪC(3)ϪC(4) and
C(1)ϪP(1)ϪC(4) planes, as observed in analogous com-
pounds.[26] The nitrogen atom is nearly planar (Σ ϭ 358.3°),
Scheme 5. Synthesis of 2,2Ј-biphospholes 8a,b: i) m-CPBA,
CH2Cl2, Ϫ30 °C to room temp.; ii) pyrHϩ, Br3Ϫ, CH2Cl2, Ϫ20 °C
to room temp.; iii) P4S10, toluene, reflux; iv) KOH, MeOH/CH2Cl2,
room temp.; v) nBuLi, THF, Ϫ90 °C; vi) CuCl2, THF, Ϫ90 °C to
room temp.
˚
the P(1)ϪN(1) distance is rather short [1.636 (3) A], and
the PϭO bond length is typical of a double bond [1.471 (3)
[27]
2
˚
A]. The minor stereoisomer 4aЈЈ which had a high JH-P
value (7.2 Hz), was not isolated in pure form but probably
corresponded to the other diastereoisomer, as was also ob-
In the first step (Scheme 5), the phospholes 2a,b reacted served in the case of 2,5-dibromo-2,5-dihydro-3,4-dimethyl-
with meta-chloroperbenzoic acid at Ϫ30 °C to give the cor- 1-phenylphosphole 1-oxide[23] (Scheme 7).
responding phosphole 1-oxides 3a,b (3a: δ31P ϭ 46.90; 3b:
In the case of 4b, only one stereoisomer was isolated, in
δ31P ϭ 43.98). These oxides, unlike 1-phenylphosphole 1- 98% yield. Complete assignment of the structure could not
oxides,[24] were stable for 48 h at room temperature in be made on the basis of on the JP-H value (6.8 Hz), which
2
dichloromethane solution and did not dimerize to give the was between 2.8 Hz and 7. 2 Hz, and an X-ray crystal struc-
[4 ϩ 2] DielsϪAlder cycloadducts (Scheme 6) even at 40 °C ture was necessary to reveal the stereochemistry of 4b,
in dichloromethane solution over 24 h, or at 110 °C in tolu- which proved to be the same as that of the major stereoiso-
ene solution over 4 h. The lack of dimerization of the 3a,b mer 4aЈ (cf. data deposited with the CCDC).
can be attributed to steric effects rather than electronic ef-
In the next step, the compounds 4a,b were transformed
fects of the diisopropylamino group. Indeed, Quin[25] has into their corresponding sulfides 5a,b prior to dehydrobro-
Eur. J. Org. Chem. 2002, 675Ϫ685
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J. Hydrio, M. Gouygou, F. Dallemer, G. G. A. Balavoine, J.-C. Daran
FULL PAPER
Figure 2. ORTEP view of molecule 4aЈ with atom labelling scheme;
˚
Figure 3. ORTEP view of molecule 5aЈ with atom labelling scheme;
ellipsoids represent 50% probability; selected bond lengths [A] and
˚
ellipsoids represent 50% probability; selected bond lengths [A] and
bond angles [°]: P(1)ϪN(1) 1.636(3), P(1)ϪO(1) 1.471(3),
P(1)ϪC(1) 1.842(4), P(1)ϪC(4) 1.841(4), C(1)ϪBr(1) 1.971(4),
C(4)ϪBr(2) 1.981(4); N(1)ϪP(1)ϪC(1) 105.7(2), N(1)ϪP(1)ϪC(4)
109.7(2), C(1)ϪP(1)ϪC(4) 92.9(2), C(1)ϪP(1)ϪO(1) 117.0(2),
C(4)ϪP(1)ϪO(1) 115.4(2), N(1)ϪP(1)ϪO(1) 114.0(2)
bond angles [°]: P(1)ϪN(1) 1.653(3), P(1)ϪS(1) 1.931(2),
P(1)ϪC(1) 1.859(4), P(1)ϪC(4) 1.847(4), C(1)ϪBr(1) 1.962(4),
C(4)ϪBr(2) 1.979(4); N(1)ϪP(1)ϪC(1) 105.20(2), N(1)ϪP(1)ϪC(4)
107.8(2), C(1)ϪP(1)ϪC(4) 92.4(2), C(1)ϪP(1)ϪS(1) 117.4(1),
C(4)ϪP(1)ϪS(1) 116.0(2), N(1)ϪP(1)ϪS(1) 115.3(1)
mination.[22] Treatment of a crude mixture of the two ste-
reoisomers 4aЈ and 4aЈЈ (in an 80:20 ratio) with P4S10 in formed by hydrolysis of the 2-lithiophosphole intermediates
refluxing toluene for 1 h quantitatively afforded a mixture 7a,b (Scheme 8). Compound 8a, isolated in 45% yield as a
1
of 5aЈ and 5aЈЈ in the same ratio (Scheme 5). In the major single diastereoisomer, was characterized by H, 31P, and
isomer 5aЈ (Figure 3), the α-H atoms were trans to the Pϭ 13C NMR, mass spectrometry, and X-ray analysis. In con-
S group, thus demonstrating that the sulfurization had trast, 8b was isolated in 14% yield as a mixture of two dias-
taken place with retention of the stereochemistry at the tereoisomers 8bЈ and 8bЈЈ in a 51:49 ratio and we were un-
phosphorus atom. The molecular structure of 5aЈ was iso- able to separate 8bЈ and 8bЈЈ by conventional methods.
morphous with 4aЈ, as indicated by the unit cell parameters However, whereas the diastereoisomer 8bЈЈ was amorphous,
and space group. As the major product 5aЈ was presumably the diastereoisomer 8bЈ crystallized and some single crystals
produced from the major isomer 4aЈ, the minor product suitable for X-ray analysis were obtained. The molecular
5aЈЈ, which could not be isolated, presumably originated structures of compounds 8a and 8bЈ are shown in Figures 4
from the minor isomer 4aЈЈ. Similarly, 4b was transformed and 5, respectively. In both compounds, the phosphole rings
into 5b in quantitative yield with retention of stereochem- are all planar within experimental error, but they are
istry at the phosphorus atom. The crude compound was twisted with respect to each other along the C(1)ϪC(1Ј)
fully characterized and its structure, established by X-ray bond. The dihedral angles between the two phosphole rings
analysis, confirmed the retention of configuration at the (67.32° in 8a and 61.29° in 8bЈ) give rise to axial chirality.
phosphorus during the sulfurization reaction, as for 5aЈ (cf. These values, which are much lower than those in analog-
data deposited with the CCDC).
ous 2,2Ј-biphospholes disulfides,[10] may be associated with
Dehydrobromination of 5a,b was then performed with the bulky diisopropylamino substituents.
methanolic potassium hydroxide to yield 6a,b in 75 and
70% yields, respectively (Scheme 5). These 2-bromophos-
phole sulfides 6a,b were fully characterized and the struc-
ture of 6b was confirmed by X-ray analysis (cf. data depos-
ited with the CCDC).
We were unable to achieve the desulfurization of 6a,b by
Scheme 8. Hydrolysis of 2-lithiophosphole intermediates 7a؊b
classical reduction with different phosphanes.[28] We then
attempted to synthesize the 2,2Ј-biphospholes by means of
a direct coupling reaction from the 2-bromophosphole sulf-
ides 6a,b, via the 2-lithio derivatives 7a,b (Scheme 5). The
These structural determinations unambiguously estab-
addition of n-butyllithium to a solution of 6a,b in THF at lished the relative configurations of both the central and the
Ϫ90 °C, followed by the addition of copper(II) chloride, axial elements of chirality. In these two compounds, both
resulted in the formation of a mixture of the 2,2Ј-biphos- phosphorus atoms had the same central absolute configura-
phole disulfides 8a,b (Scheme 5) and, as undesired side tion ([R,R] or [S,S]), in association either with an opposite
products, the 1-(diisopropylamino)phosphole sulfides 9a,b, axial absolute configuration in 8a, or with the same axial
678
Eur. J. Org. Chem. 2002, 675Ϫ685

A Convenient Procedure for the Preparation of 1-(Diisopropylamino)phospholes
FULL PAPER
diastereoisomer 8bЈЈ, two possibilities arise; this isomer
could correspond either to the third diastereoisomer,
(R[SR], S[RS]), or to the first diastereoisomer, (S[RR],
R[SS]). However, as the diastereoisomer (R[SR], S[RS]) was
not observed in the case of the less hindered 8a, we assume
that 8bЈЈ corresponds to the diastereoisomer (S[RR],
R[SS]), as observed in the case of 8a.
These results were supported by molecular mechanics
calculations performed on 2,2Ј-biphosphole disulfides 8
with the different phosphorus configurations, [R,R] ([S,S])
and [R,S] ([S,R]). Systematic conformational analysis of the
rotation process around the CϪC bond linking the two
phosphole rings was carried out. For 8b, the calculations
showed that the [R,S] ([S,R]) isomer was energetically less
favored than the [R,R] ([S,S]) isomer, although the differ-
ence in energy was small (3 kcal·molϪ1). For the [R,R]
([S,S]) isomer, two minima, corresponding to two stable
conformers, were located at the same energy level on the
potential energy surface, in agreement with our experi-
mental results. The estimated energy barrier between these
two conformers was 16 kcal·molϪ1. Experimentally, no in-
Figure 4. ORTEP view of molecule 8a with atom labelling scheme;
˚
ellipsoids represent 50% probability; selected bond lengths [A] and
bond angles [°]: P(1)ϪN(1) 1.651(1), P(1)ϪS(1) 1.9532(4),
P(1)ϪC(1) 1.820(1), P(1)ϪC(4) 1.787(1), C(1)ϪC(1Ј) 1.462(2);
N(1)ϪP(1)ϪC(1)
C(1)ϪP(1)ϪC(4)
107.85(8),
92.40(5),
N(1)ϪP(1)ϪC(4)
C(1)ϪP(1)ϪS(1)
111.82(8),
114.72(3), terconversion between 8bЈ and 8bЈЈ occurred even at ϩ90
°C in toluene, according to NMR studies. These two con-
formers are shown in Figure 7. In the first conformer, the
torsion angle[29] of ϩ53.5° is close to the torsion angle ob-
served from X-ray analysis for 8bЈ (torsion angle ϭ 46°). In
the second conformer, the torsion angle of Ϫ35.5° is indic-
ative of an axial absolute configuration opposite to that in
the first conformer. These results, which are consistent with
the existence of the two diastereoisomers, (S[SS], R[RR])
and (S[RR], R[SS]), in the case of 8b thus support our hy-
pothesis that 8bЈ corresponds to the (S[RR], R[SS]) diaster-
eoisomer. Similar calculations performed on 8a showed that
the [R,R] ([S,S]) and [R,S] ([S,R]) isomers had the same en-
ergy. However, only the [R,R] ([S,S]) forms were isolated
and characterized experimentally. For this isomer, calcula-
tions showed the existence of many conformers for which
the differences in energy were small (2Ϫ4 kcal·molϪ1). The
geometry of the most stable conformer (Figure 8), which
predicted a torsion angle of 43.6°, was close to that estab-
lished by X-ray analysis for 8a (torsion angle ϭ 58°). The
observation of only one isomer in solution in the case of 8a
C(4)ϪP(1)ϪS(1) 112.26(4), N(1)ϪP(1)ϪS(1) 115.51(4)
Figure 5. ORTEP view of molecule 8bЈ with atom labelling scheme;
˚
is probably attributable to free rotation around the CϪC
bond. Indeed, according to the calculations, 8a had a lower
free enthalpy of activation than 8b for the rotation barrier
around the CϪC bond (5 kcal·molϪ1). In the solid state,
isomer 8a crystallized to give the most stable form, which
corresponds to the (S[RR], R[SS]) diastereoisomer.78
The last stage in our synthesis was the reduction of 8a,b
ellipsoids represent 50% probability; selected bond lengths [A] and
bond angles [°]: P(1)ϪN(11) 1.666(3) [1.665(3)], P(1)ϪS(1) 1.947(1)
[1.944(1)], P(1)ϪC(11) 1.842(3) [1.829(3)], P(1)ϪC(14) 1.794(4)
[1.785(3)]; N(1)ϪP(1)ϪC(11) 110.1(1) [109.4(1)], N(1)ϪP(1)ϪC(14)
107.6(2) [108.7(2)], C(11)ϪP(1)ϪC(14) 91.6(2) [91.7(2)],
C(11)ϪP(1)ϪS(1) 113.7(2) [114.1(1)], C(14)ϪP(1)ϪS(1) 115.0(1)
[114.4(1)], N(1)ϪP(1)ϪS(1) 116.2(1) [115.9(1)]
absolute configuration in 8bЈ. The different possibilities of to free 2,2Ј-biphosphole 10a,b. Unfortunately, under Ma-
combining axial and central chiralities in 2,2Ј-biphosphole they’s[28] conditions to obtain BIPHOS,[23] treatment of dis-
are depicted in Figure 6, in Newman projections along the ulfides 8a,b either with trimethylphosphane or with tris(2-
CϪC axis of the bond linking the two phosphole rings. This cyanoethyl)phosphane did not afford the corresponding
stereochemical analysis shows the occurrence of six ste- 2,2Ј-biphospholes 10a,b but resulted in the formation of un-
reoisomers corresponding to three pairs of enantiomers. identified products. By using Mikolajczyk’s procedure,[30]
The first diastereoisomer, (S[RR], R[SS]), is obtained for 8a we were able to observe the formation of 2,2Ј-biphosphole
and the second diastereoisomer, (S[SS], R[RR]), is obtained 10a, starting from the disulfide 8a (Scheme 9), by 31P NMR
for one of the two diastereoisomers of 8bЈ. For the other and mass spectrometry. As the procedure gave rather low
Eur. J. Org. Chem. 2002, 675Ϫ685
679

J. Hydrio, M. Gouygou, F. Dallemer, G. G. A. Balavoine, J.-C. Daran
FULL PAPER
Figure 6. The 23 stereoisomers of 2,2Ј-biphospholes possessing 2 chiral centers and 1 chiral axis; among these eight stereoisomers, six
are truly inequivalent; axial chirality is given first and central chirality is between square brackets
influence of the diisopropylamino group on the 2,2Ј-
biphosphole framework.
Figure 7. The two stable conformers of compound 8b
Scheme 9. Reduction of disulfide 8a: i) CF3SO3Me, CH2Cl2, room
temp.; ii) tBuSLi, Et2O/CH2Cl2, Ϫ78 °C to room temp.
Conclusions
We have developed a convenient one-pot procedure to
prepare two 1-(diisopropylamino)phospholes. These phos-
phole moieties have been used for the synthesis of two new
2,2Ј-biphospholes derivatives, 1,1Ј-bis(diisopropylamino)-
3,3Ј,4,4Ј-tetramethyl-2,2Ј-biphosphole 1,1Ј-disulfide (8a)
and 1,1Ј-bis(diisopropylamino)-3,3Ј,4,4Ј-tetraphenyl-2,2Ј-
biphosphole 1,1Ј-disulfide (8b). Compound 8b exists as two
Figure 8. The stable conformer of compound 8a
yields of 10a, however, the compound could not be isolated stable diastereoisomers, unlike compound 8a, according to
in a pure form. We are currently investigating new methods both experimental and theoretical studies. Thus, these re-
for the desulfurization of these 1,1Ј-bis(diisopropyl)-2,2Ј-bi- sults show that a combination of bulky substituents in posi-
phosphole disulfides, in order to continue our study of the tions 1 (iPr2N) and 3 (Ph) is an important factor in the
680
Eur. J. Org. Chem. 2002, 675Ϫ685

A Convenient Procedure for the Preparation of 1-(Diisopropylamino)phospholes
FULL PAPER
1-(Diisopropylamino)-3,4-dimethylphosphole 1-Oxide (3a): A solu-
tion of dry meta-chloroperbenzoic acid (1.207 g, 7.46 mmol) in
dichloromethane (8 mL) was added dropwise at Ϫ30 °C to a
dichloromethane solution (10 mL) of 2a (1.431 g, 6.70 mmol). The
mixture was allowed to stir at 0 °C for 1 h and then concentrated
to dryness. The crude 3a was only characterized by 31P and 1H
NMR and used without further purification. 31P NMR (CDCl3):
stabilization of axial chirality. We are currently studying
methods for the reduction of these 1,1Ј-bis(diisopropylam-
ino)-2,2Ј-biphosphole disulfides to the 1,1Ј-bis(diisopropyl-
amino)-2,2Ј-biphospholes in order to study the configura-
tional stability of their phosphorus centers, their coordina-
tion chemistry, and potential applications in asymmetric
catalysis.
1
δ ϭ 46.9. H NMR (CDCl3): δ ϭ1.24 [d, JH,H ϭ 6.75 Hz, 12 H,
(CH3)2CH], 1.98 (s, 6 H, CH3), 3.54 [m, 2 H, (CH3)2CHN], 5.84
(d, JHP 24.88 Hz, 2 H, CHP).
Experimental Section
1-(Diisopropylamino)-3,4-diphenylphosphole 1-Oxide (3b): The ex-
perimental procedure was the same as above. Compound 3b was
obtained as a yellow oil (680 mg, 87%). 31P NMR (CDCl3): δ ϭ
42.98. 1H NMR (CDCl3): δ ϭ1.30 [d, JH,H ϭ 6.75 Hz, 12 H,
(CH3)2CHN], 3.67 [m, 4 H, (CH3)2CHN], 6.12 (d, JH,P ϭ 23.3 Hz,
2 H, CHP), 6.98Ϫ7.7 (m, 20 H, Ph). 13C NMR (CDCl3): δ ϭ 23.5
[s, (CH3)2CH], 46.8 [s, (CH3)2CH], 124.21 (d, JC,P ϭ 116 Hz, CHP),
127.9Ϫ128.5 (m, Ph), 135.95 (d, JC,P ϭ 19.9 Hz, Cipso), 153.27 (d,
JC,P ϭ 24.4 Hz, PhC). MS (DCI, CH4): m/z (%) ϭ 352 (100) [M
ϩ H]ϩ.
General: All reactions were carried out under dry argon by use of
Schlenk glassware and vacuum-line techniques. Solvents were
freshly distilled from standard drying agents. Flash chromato-
graphy was carried out under argon on Merck silica gel (230Ϫ400
mesh). Melting points (uncorrected) were determined with a Stuart
1
Scientific SMP1 apparatus. H, 31P{1H}, and 13C{1H, 31P} NMR
spectra were recorded with a Bruker AM 250 instrument operating
at 250, 101, and 63 MHz, respectively. Chemical shifts are reported
in parts per million (ppm) relative to Me4Si (1H and 13C) or 85%
H3PO4 (31P). Mass spectra were obtained with a Mermag R10Ϫ10
instrument. Elemental analyses were performed by the ‘‘Service
d’Analyse du Laboratoire de Chimie de Coordination’’ at Toulouse.
P,P-Dichloro(diisopropylamino)phosphane was prepared as de-
scribed in the literature.[19]
2,5-Dibromo-2,5-dihydro-1-(diisopropylamino)-3,4-dimethyl-
phosphole 1-Oxide (4a): Pyridinium tribromide (2.50, 7.8 mmol)
was added rapidly at Ϫ20 °C to a dichloromethane solution of
crude 3a previously obtained. The mixture was allowed to stir for
20 min at 0 °C and 2 h at room temp. and was then treated with
aqueous sodium sulfite. The aqueous layer was washed 3 times with
dichloromethane; the organic extracts were washed until neutral
with water, dried with MgSO4, and filtered. After removal of the
solvent, the major isomer 3aЈ was recrystallized from dichlorome-
thane at Ϫ18 °C to give white crystals (1.76 g, 84%). m.p. 145 °C
1-(Diisopropylamin)o-3,4-dimethylphosphole
(2a):
(iPr)2NPCl2
(2.1 g, 10.3 mmol) was added dropwise at Ϫ78 °C to a stirred sus-
pension of AlCl3 (1.34 g, 10 mmol) in dichloromethane (30 mL).
After 15 min, the mixture was allowed to warm to room temp. and
the stirring was continued for 1 h to afford a colorless solution
of the corresponding phosphenium compound. This solution was
cooled again to Ϫ78 °C, and 2,3-dimethyl-1,3-butadiene (0.83 g,
10.1 mmol) was added dropwise to give an orange solution. This
mixture was stirred for 15 min at Ϫ78 °C and for 3 h at room
temperature, and the solvent was then evaporated under reduced
pressure to give the crude phospholenium compound 1a. Com-
pound 1a was then dissolved in THF (25 mL) and cooled to Ϫ78
°C, and LiHMDS (1 , 20 mmol) was added dropwise. The mixture
was stirred for 15 min at Ϫ78 °C and for 1 h at room temp. and
then concentrated to dryness. The resulting residue was extracted
with small portions of pentane. The combined pentane phases were
1
(decomp). 31P NMR (CDCl3): δ ϭ 36.34. H NMR (CDCl3): δ ϭ
1.25 [d, JH,H ϭ 6.78 Hz, 12 H, (CH3)2CH], 1.91 (s, 6 H, CH3), 3.21
[m, 2 H, (CH3)2CH], 4.36 (d, JH,P ϭ 2.7 Hz, 2 H, CHBr). 13C NMR
(CDCl3): δ ϭ 15.7 (d, JC,P ϭ 10 Hz, CH3), 23.0 [s, (CH3)2CH], 46.4
(d, JC,P ϭ 86 Hz, CHP), 47.1 [s, (CH3)2CH], 135.9 (d, JC,P ϭ 14 Hz,
CH3C). MS (DCI, CH4): m/z (%) ϭ 388 (8) [M ϩ H]ϩ, 308 (17)
[M ϩ H Ϫ Br]ϩ, 228 (100) [M ϩ H Ϫ 2 Br]ϩ. C12H22Br2NOP
(387.10): C 37.23, H 5.73, N 3.62; found C 36.46, H 4.94, N: 2.67.
2,5-Dibromo-2,5-dihydro-1-(diisopropylamino)-3,4-diphenyl-
phosphole 1-Oxide (4b): The synthesis of 4b was accomplished by
the same procedure as described above for 4a. Compound 4b, ob-
washed twice with water and dried with MgSO4, and the solvents tained as yellow solid (98%), was used without further purification.
were evaporated to give 2a as a white-yellow solid (1.83 g, 68%). 31P NMR (CDCl3): δ ϭ 35.48. 1H NMR (CDCl3): δ ϭ 1.33 [d,
31P NMR (CDCl3): δ ϭ 28.40. 1H NMR (CDCl3): δ ϭ1.04 [d,
JH,H ϭ 6.8 Hz, 12 H, (CH3)2CH], 3.45 [m, 2 H, (CH3)2CH], 4.88
JH,H ϭ 6.6 Hz, 12 H, (CH3)2CH], 1.99 (d, JH,P ϭ 5.3 Hz, 6 H, (d, JH,P ϭ 6.6 Hz, 2 H, CHP), 7.32 (m, 10 H, Ph). 13C NMR
CH3), 2.85 [m, 2 H, (CH3)2CH], 6.04 (d, JH,P ϭ 36 Hz, 2 H, CHP).
(CDCl3): δ ϭ 23.17 [s, (CH3)2CH], 44.6 (d, JC,P ϭ 88 Hz, CHP),
13C NMR (CDCl3): δ ϭ 17.4 (d, JC,P ϭ 6.7 Hz,CH3), 23.6 [d, 48.13 [s, (CH3)2CH], 128.57Ϫ128.88 (m, Ph), 135.3 (d, JC,P
C,P ϭ 6 Hz, (CH3)2CH], 48.7 [d, JC,P ϭ 7.2 Hz, (CH3)2CH], 129.6 11.2 Hz, Cipso), 141.3 (d, JC,P ϭ 13.5 Hz, PhC). MS (DCI, CH4):
ϭ
J
(s, CHP), 145.1 (d, JC,P ϭ 15.2 Hz, CH3C). MS (DCI, CH4): m/z m/z (%) ϭ 512 (51) [M ϩ H]ϩ, 432 (76) [M ϩ H Ϫ Br]ϩ, 352 (100)
(%) ϭ 212 (100%) [MH]ϩ. Crystals suitable for X-ray analysis were
obtained by slow concentration of a pentane solution.
[M ϩ H Ϫ 2 Br]ϩ. C22H26Br2NOP (511.25): C 51.6, H 5.13, N
2.74; found C 52.97, H 4.09, N: 2.46. Crystals suitable for X-ray
analysis were obtained by slow concentration of a dichloromethane
solution from the crude product before treatment; these crystals
contained an equimolar mixture of 4b and m-chlorobenzoic acid.
1-(Diisopropylamino)-3,4-diphenylphosphole (2b): The experimental
procedure was the same as above. Compound 2b was obtained as
an orange oil (84%). 31P NMR (CDCl3): δ ϭ 35.19. 1H NMR
(CDCl3): δ ϭ 1.24 [d, JH,H ϭ 7.2 Hz, 12 H, (CH3)2CH], 3.15 [m, 2 2,5-Dibromo-2,5-dihydro-1-(diisopropylamino)-3,4-dimethyl-
H, (CH3)2CH], 6.70 (d, JH,P ϭ 33 Hz, 2 H, CHP), 7.0Ϫ7.5 (m, 10
phosphole 1-Sulfide (5a): A mixture of crude 4a (1.70 g, 4.39 mmol)
and P4S10 (1.1 g, 2.63 mmol) was refluxed in toluene (10 mL) for
H, Ph). 13C NMR (CDCl3): δ ϭ 23.9 [d, JC,P ϭ 5.5 Hz, (CH3)2CH],
50.4 [d, JC,P ϭ 8.5 Hz, (CH3)2CH], 126.9Ϫ128.6 (s, Ph), 134.5 (s, 30 min. After removal of the solvent, the major isomer 5aЈ was
CHP), 138.9 (d, JC,P ϭ 4 Hz, Cipso), 147.4 (d, JC,P ϭ 16 Hz, PhC). isolated by flash chromatography on silica gel (dichloromethane/
MS (DCI, CH4): m/z (%) ϭ 336 (100) [M ϩ H]ϩ. C22H26NP pentane, 50:50) and purified by recrystallization from dichlorome-
(335.43): C 78.8, H 7.81, N 4.18; found C 78.97, H 7.50, N 4.03.
thane. Compound 5aЈ was obtained as a yellow solid (807 mg, 53%
Eur. J. Org. Chem. 2002, 675Ϫ685
681

J. Hydrio, M. Gouygou, F. Dallemer, G. G. A. Balavoine, J.-C. Daran
FULL PAPER
for the two steps). 31P NMR (CDCl3): δ ϭ 80.45. 1H NMR
(CDCl3): δ ϭ 1.27 [d, JH,H ϭ 7.0 Hz, 12 H, (CH3)2CH], 1.92 (s, 6
H, CH3), 3.45 [m, 2 H, (CH3)2CH,], 4.78 (d, JH,P ϭ 1.2 Hz, 2 H,
CHBr). 13C NMR (CDCl3): δ ϭ 16.3 (d, JC,P ϭ 8 Hz, CH3), 22.9
[s, (CH3)2CH], 48.9 [s, (CH3)2CH], 52.9 (d, JC,P 66 Hz, CHP), 135.4
(d, JC,P ϭ 10 Hz, CCH3). MS (DCI, CH4): m/z (%) ϭ 404 (85) [M
ϩ H]ϩ, 324 (100) [M ϩ H Ϫ Br]ϩ. C12H22Br2NPS (403.2): C 35.75,
H 5.50, N 3.47; found C 35.86; H 4.60; N 4.73.
5.82, N 3.42. Crystals suitable for X-ray analysis were obtained by
slow concentration of a dichloromethane solution.
1,1Ј-Bis(diisopropylamino)-3,3Ј,4,4Ј-tetramethyl-2,2Ј-biphosphole
1,1Ј-Disulfide (8a): n-Butyllithium (510 µL, 0.82 mmol) was added
dropwise at Ϫ90 °C to a solution of phosphole sulfide 6a (240mg;
0.74 mmol) in THF (10 mL). After 30 min of stirring, solid CuCl2
(148 mg, 1.12 mmol) was added. The resulting mixture was stirred
at Ϫ80 °C for 2 h and was then allowed to warm at room temper-
ature. After filtration, the filtrate was diluted with dichloromethane
(20 mL) and was washed with aqueous NH3 (14%) until the blue
color of the aqueous layer disappeared. The organic phase was then
washed with water, dried with MgSO4, and concentrated under re-
duced pressure. The crude residue was then dissolved in a small
amount of dichloromethane and precipitated with a large excess of
pentane. After filtration, 8a was obtained as yellow solid (161 mg,
45%), m.p. 258 °C (decomp.). 31P NMR (CDCl3): δ ϭ68.2. 1H
2,5-Dibromo-2,5-dihydro-1-(diisopropylamino)-3,4-diphenyl-
phosphole 1-Sulfide (5b): The synthesis of 5b was accomplished by
the same procedure as described above for 5a, from 4b (6.75 g) and
P4S10 (3.54 g). Crude 5b was obtained in quantitative yield as an
orange solid (6.90 g, 99%) and was used without further purifica-
1
tion. 31P NMR (CDCl3): δ ϭ 78.70. H NMR (CDCl3): δ ϭ 1.34
[d, JH,H ϭ 3.2 Hz, 12 H, (CH3)2CH], 3.67 [m, 2 H, (CH3)2CH],
5.20 (d, JH,P ϭ 5 Hz, 2 H, CH), 7.14Ϫ7.30 (m, 10 H, Ph). 13C
NMR (CDCl3): δ ϭ 23.18 [s, (CH3)2CH], 49.44 [s, (CH3)2CH],
51.90 (d, JC,P ϭ 65.8 Hz, CHP), 128.50Ϫ128.99 (m, Ph), 135.61 (d,
NMR (CDCl3): δ ϭ 1.11 [d, JH,H ϭ 7 Hz, 12 H, (CH3)2CH], 1.22
3
[d, JH,H ϭ 7 Hz, 12 H, (CH3)2CH], 1.70 (AB system, JH,P
ϭ
4JH,P ϭ 2.0 Hz, 6 H, CH3), 2.00 (b, 6 H, CH3), 3.89 [m, 4 H,
(CH3)2CH], 5.92 (d, JH,P ϭ 30 Hz, 2 H, CHP). 13C NMR (CDCl3):
δ ϭ 15.7 (d, JC,P ϭ 15 Hz, CH3), 17.7 (d, JC,P ϭ 18 Hz, CH3), 23.7
[s, (CH3)2CH], 47.3 [s, (CH3)2CH], 126.0 (d, JC,P ϭ 95 Hz, CHP),
135.1 (d, JC,P ϭ 98 Hz, CϪC), 144.0 (d, JC,P ϭ 31 Hz, CH3C),
146.3 (d, JC,P ϭ 18.8 Hz, CH3C). MS (DCI, CH4): m/z (%) ϭ 485
(100) [M ϩ H]ϩ. C24H42N2P2S2 (484.7): C 59.48, H 8.73, N 5.78,
S:13.23; found C 59.73, H 8.67, N 5.69, S 12.93. Crystals suitable
for X-ray analysis were obtained by slow concentration of a dichlo-
romethane solution.
J
C,P ϭ 9.3 Hz, Cipso), 141.38 (d, JC,P 9.7 Hz, PhC). MS (DCI, CH4):
m/z (%) ϭ 528 (35) [M ϩ H]ϩ, 448 (40) [M ϩ H Ϫ Br]ϩ, 368 (100)
[M ϩ H Ϫ 2 Br]ϩ. C22H26Br2NPS (527.3): C 50.11, H 4.97, N 2.66;
found C 50.12, H 4.74, N 2.47. Crystals suitable for X-ray analysis
were obtained by slow concentration of a dichloromethane solu-
tion.
2-Bromo-1-diisopropylamino-3,4-dimethylphosphole 1-Sulfide (6a):
A solution of KOH (80 mg, 1.44 mmol) in methanol (2 mL) was
added dropwise to a solution of 5aЈ (290 mg, 0.72 mmol) in dichlo-
romethane (4 mL). The resulting mixture was allowed to stir at
room temperature for 2 h 30 and was then diluted with dichlorome-
thane (20 mL). The mixture was washed three times with water and
the combined aqueous layers were re-extracted with dichlorome-
thane. The organic layers were combined, dried with MgSO4, and
filtered, and the solvents were evaporated to dryness to afford
crude 6a as a brown solid (243 mg, 75%). 31P NMR (CDCl3): δ ϭ
62.98. 1H NMR (CDCl3): δ ϭ 1.25 [d, JH,H ϭ 7.2 Hz, 12 H,
(CH3)2CH], 1.93 (d, JH,P ϭ 3 Hz, 3 H, CH3), 2.,03 (d, JH,P ϭ 3 Hz,
3 H, CH3), 3.50 [m, 2 H, (CH3)2CH], 5.87 (d, JH,P ϭ 28 Hz, 1 H,
CHP). 13C NMR (CDCl3): δ ϭ 15.2 (d, JC,P ϭ 12 Hz, CH3), 18.3
(d, JC,P ϭ 18 Hz, CH3), 23.3 [d, JC,P ϭ 14 Hz, (CH3)2CH], 47.4 [d,
1,1Ј-Bis(diisopropylamino)-3,3Ј,4,4Ј-tetraphenyl-2,2Ј-biphosphole
1,1Ј-Disulfide (8b): The synthesis of 8b was accomplished by the
same procedure as described above for 8a, from 6b (4.01 g), n-butyl-
lithium (1.6 , 6.2 mL), and CuCl2 (1.81 g), to afford 454 mg of 8b
as a mixture of two diastereoisomers (14%) in a 51:49 ratio. MS
(DCI, CH4): m/z (%) ϭ 733 (100) [M ϩ H]ϩ, 632 (99) [M ϩ H Ϫ
N(iPr)2]ϩ. C44H50N2P2S2 (732.95): C 72.10, H 6.88, N 3.82; found
C 71.89, H 6.77, N 3.92. Major isomer: 31P NMR (CDCl3): δ ϭ
75.76. 1H NMR (CDCl3): δ ϭ 1.31 [d, JH,H ϭ 6.8 Hz, 12 H,
(CH3)2CH], 1.52 [d, JH,H ϭ 6.8 Hz, 12 H, (CH3)2CH], 4.29 [m, 4
H, (CH3)2CH], 6.36 (d, JH,P ϭ 29.1 Hz, 2 H, CHP), 6.78Ϫ6.90 (m,
8 H, Ph), 7.01Ϫ7.17 (m, 12 H, Ph). Crystals of the major isomer
suitable for X-ray analysis were obtained by slow concentration of
a dichloromethane solution. Minor isomer: 31P NMR (CDCl3): δ ϭ
69.36. 1H NMR (CDCl3): δ ϭ 1.40 [d, JH,H ϭ 6.7 Hz, 12 H,
(CH3)2CH], 1.63 [d, JH,H ϭ 6.7 Hz, 12 H, (CH3)2CH], 4.67 [m, 4
H, (CH3)2CH], 6.38 (d, JH,P ϭ 29.1 Hz, 2 H, CHP), 6.62Ϫ6.71 (m,
8 H, Ph), 6.93Ϫ7.00 (m, 12 H, Ph).
JC,P ϭ 6 Hz, (CH3)2CH], 121.5 (d, JC,P ϭ 100 Hz, CBrP), 122.3 (d,
JC,P ϭ 100 Hz, CHP), 143.,4 (d, JC,P ϭ 15 Hz, CH3C), 150.0 (d,
JC,P ϭ 15 Hz, CH3C). MS (DCI, CH4): m/z (%) ϭ 324 (100) [M ϩ
2 H]ϩ; 322 (97) [M]ϩ. C12H21BrNPS (322.25): C 44.73, H 6.57, N
4.35; found C 44.91, H 6.63, N 4.15. Crystals suitable for X-ray
analysis were obtained by slow concentration of a dichlorome-
thane solution.
Compounds 9a and 9b, obtained as undesired side products in the
syntheses of 8a and 8b, respectively, were isolated in the filtrate and
purified by flash chromatography on silica gel (dichloromethane/
pentane, 30:70)
2-Bromo-1-(diisopropylamino)-3,4-diphenylphosphole 1-Sulfide (6b):
The synthesis of 6b was accomplished by the same procedure as
described above for 6a, from 5b (6.90 g) and KOH (1.47 g). Crude
6b, obtained as an orange solid (4.01 g, 70%), was used without
further purification. 31P NMR (CDCl3): δ ϭ 63.57. 1H NMR
(CDCl3): δ ϭ 1.32 [d, JH,H ϭ 6.8 Hz, 6 H, (CH3)2CH], 1.36 [d,
1-(Diisopropylamino)-3,4-dimethylphosphole 1-Sulfide (9a): Yellow
1
solid (50%). 31P NMR (CDCl3): δ ϭ 65.5. H NMR (CDCl3): δ ϭ
1.21 [d, JH,H ϭ 6.5 Hz, 12 H, (CH3)2CH], 1.98 (d, JH,P ϭ 1.0 Hz,
6 H, CH3), 3.62 [m, 2 H, (CH3)2CH], 5.88 (d, 2 H, JH,P ϭ 28.8 Hz,
CHP). 13C NMR (CDCl3): δ ϭ 17.01 (d, JC,P ϭ 19.5 Hz, CH3),
23.22 [s, (CH3)2CH], 47.68 [s, (CH3)2CH], 132.41 (s, CHP), 148.44
(d, JC,P 21.8 Hz, CH3C). MS (DCI,CH4): m/z (%) ϭ 244 (100)
[MH]ϩ, 143 (11) [M Ϫ 100]ϩ.
J
H,H ϭ 6.8 Hz, 6 H, (CH3)2CH], 3.80 [m, 2 H, (CH3)2CH], 6.29 (d,
JH,P ϭ 28 Hz, 1 H, CHP), 6.91Ϫ7.29 (m, 10 H, Ph). 13C NMR
(CDCl3): δ ϭ 23.5 [d, JC,P ϭ 11 Hz, (CH3)2CH], 47.5[d, JC,P
4.3 Hz, (CH3)2CH], 124.9 (d, JC,P ϭ 96.7 Hz, CHP), 127.7 (d,
ϭ
JC,P ϭ 100 Hz, CBrP), 127.9Ϫ129.1 (m, Ph), 133.9 (d, JC,P
13.5 Hz, Cipso), 135.5 (d, JC,P ϭ 18 Hz, Cipso), 145.2 (d, JC,P
ϭ
ϭ
31.2 Hz, PhC), 152.5 (d, JC,P 16.6 Hz, PhC). MS (DCI, CH4): m/z 1-(Diisopropylamino)-3,4-diphenylphosphole 1-Sulfide (9b): Yellow
1
(%) ϭ 448 (100) [M ϩ 2 H]ϩ; 447 (39) [M ϩ H]ϩ; 446 (95) [M]ϩ. solid (80%), m.p. 133Ϫ135 °C. 31P NMR (CDCl3): δ ϭ 64.50. H
C22H25BrNPS (446.4): C 59.20, H 5.65, N 3.14; found C 59.60, H
682
NMR (CDCl3): δ ϭ 1.31 [d, JH,H ϭ 6.8 Hz, 12 H, (CH3)2CH], 3.83
Eur. J. Org. Chem. 2002, 675Ϫ685

A Convenient Procedure for the Preparation of 1-(Diisopropylamino)phospholes
FULL PAPER
[m, 2 H, (CH3)2CH], 6.32 (d, JH,P ϭ 27.3 Hz, 2 H, CHP),
H]ϩ. C22H26NPS (367.50): C 71.90, H 7.13, N 3.81; S 8.72; found
6.99Ϫ7.08 (m, 4 H, Ph), 7.17Ϫ7.30 (m, 6 H, Ph). 13C NMR C 70.27, H 7.35, N 3.42, S 7.57.
(CDCl3): δ ϭ 23.3 [s, (CH3)2CH], 47.7 [d, JC,P ϭ 3.7 Hz,
(CH3)2CH], 127.9 (m, Ph), 128.1 (d, JC,P ϭ 94 Hz, CHP), 1,1Ј-Bis(diisopropylamino)-3,3Ј,4,4Ј-tetramethyl-2,2Ј-biphosphole
128.3Ϫ128.5 (m, Ph), 135.7 (d, JC,P ϭ 19.4 Hz, Cipso), 150.4 (d,
C,P ϭ 21.2 Hz, PhC). MS (DCI, CH4): m/z (%) ϭ 368 (100) [M ϩ
(10a): CF3SO3Me (0.300 mL, 2.48 mmol) was added dropwise to a
solution of 8a (0.602 mg, 1.24 mmol) in dichloromethane (20 mL).
J
Table 1. Crystal data
2a
4aЈ
4b
5aЈ
Empirical formula
Formula mass
Temperature [K]
Crystal system
Space group
C12H22NP
211.3
180(2)
C12H22NOPBr2
387.1
180(2)
monoclinic
P21/a
11.4016(15)
7.7488(10)
18.0964(22)
90.0
103.15(2)
90.0
1556.8(3)
4
1.651
52.450
C29H31Br2ClNO3P
667.81
150(2)
monoclinic
C2/c
11.3735(10)
12.9365(9)
39.017(3)
90.0
94.51(1)
90.0
5722.9(8)
8
1.550
30.135
C12H22NSPBr2
403.16
180
monoclinic
P21/a
12.112(2)
7.7547(7)
17.643(3)
90.0
104.73(2)
90.0
1602.6(6)
4
1.671
52.155
triclinic
¯
P1
˚
a [A]
7.4043(10)
7.6092(10)
12.6715(16)
90.91(2)
98.62(2)
110.01(2)
661.5(2)
2
1.061
1.757
2.86 Ͻ θ Ͻ 25.97
6376
˚
b [A]
˚
c [A]
α [°]
β [°]
γ [°]
3
˚
V [A ]
Z
ρ(calcd) [gcmϪ3
]
µ(Mo-Kα) [cmϪ1
θ range [°]
]
2.86 Ͻ θ Ͻ 26.20
15210
2.39 Ͻ 2θ Ͻ 24.09
13831
2.39 Ͻ θ Ͻ 26.11
10274
Reflections measured
Independent reflections (Rint
Reflections used [I Ͼ 2σ(I)]
)
2366 (0.0476)
1726
3061 (0.0540)
2155
4460 (0.0428)
3658
3145 (0.0597)
2259
R
Rw
0.0396
0.0480
0.0426
0.0446
0.0295
0.0313
0.0450
0.0486
(∆/σ)max
∆ρmin/∆ρmax
GOF
0.052
Ϫ0.22/0.23
1.026
0.017
Ϫ0.62/0.72
1.0534
0.021
Ϫ0.36/0.50
0.965
0.045
Ϫ1.11/0.76
0.944
Variable parameters
128
155
339
155
Table 2. Crystal data (Continued)
5b
6b
8a
8bЈ
Empirical formula
Formula mass
Temperature [K]
Crystal system
Space group
C22H26Br2NPS
527.30
160(2)
C22H25 BrNPS
446.39
160(2)
monoclinic
P21
11.846(3)
12.928 (2)
15.033(4)
90.0
110.39(3)
90.0
2158.1(9)
4
1.374
20.816
C24H42N2P2S2
484.68
160(2)
monoclinic
C2/c
24.225(4)
8.1372(9)
18.142(3)
90.0
129.34(1)
90.0
2766.3(11)
4
1.164
3.115
C44H50 N2P2S2
732.96
180(2)
monoclinic
P21/c
8.7740(8)
23.391(3)
19.3229(16)
90.0
97.74(1)
90.0
3929.6(7)
4
1.239
2.504
triclinic
¯
P1
˚
a [A]
7.8928(21)
10.0827(25)
14.817(4)
73.68(3)
82.23(3)
80.38(3)
1110.9(5)
2
1.576
37.818
2.23 Ͻ θ Ͻ 26.03
11031
˚
b [A]
˚
c [A]
α [°]
β [°]
γ [°]
3
˚
V [A ]
Z
ρ(calcd) [gcmϪ3
]
µ(Mo-Kα) [cmϪ1
θ range [°]
]
2.14 Ͻ θ Ͻ 26.15
21540
2.27 Ͻ θ Ͻ 26.11
11676
2.04 Ͻ θ Ͻ 24.21
25321
Reflections measured
Independent reflections (Rint
reflections used [I Ͼ 2σ(I)]
)
4047 (0.0430)
3298
8418 (0.0833)
6496
2671 (0.0413)
2299
6019 (0.0974)
2534
R
Rw
0.0392
0.0412
0.0537
0.0559
0.0310
0.0346
0.0317
0.0311
(∆/σ)max
∆ρmin/∆ρmax
GOF
0.032
Ϫ1.17/1.12
0.999
0.020
Ϫ0.83/1.06
1.01
0.082
Ϫ0.21/0.34
0.9947
0.043
Ϫ0.22/0.24
1.0876
Variable parameters
245
476
137
452
Eur. J. Org. Chem. 2002, 675Ϫ685
683

J. Hydrio, M. Gouygou, F. Dallemer, G. G. A. Balavoine, J.-C. Daran
FULL PAPER
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After 24 h of stirring, the resulting suspension was concentrated to
ca. 10 mL and cooled to Ϫ78 °C. Then, a solution of tBuSLi,
obtained by treatment of 2-methyl-2-propanethiol (0.300 mL,
2.48 mmol) in ether (4 mL) with n-butyllithium (2.48 mmol, 1.55
mL, 2.5  in hexane) at Ϫ40 °C, was added dropwise. The resulting
solution was stirred for 15 min at Ϫ78 °C and for 2 h at room
temp. and then concentrated to dryness. The resulting residue was
extracted with small portions of pentane. The combined pentane
phases were washed with water and dried with MgSO4, and the
solvents were evaporated to give crude compound 10a (52 mg,
10%). 31P NMR (CDCl3): δ ϭ 44.90. MS (DCI, CH4): m/z (%) ϭ
421 (100) [M ϩ H]ϩ.
[4]
[5]
[6]
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[8]
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M. Gouygou, O. Tissot, J-C. Daran, G. G. A. Balavoine,
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reflections. Only statistical fluctuations were observed in the intens-
ity monitors over the course of the data collection. The eight struc-
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˚
into idealized positions [d(CH)ϭ 0.96 A] and their atomic coordin-
[12]
ates were recalculated after each cycle. They were given isotropic
thermal parameters 20% higher than those of the carbon atom to
which they were attached. Least-squares refinements were carried
out by minimizing the function Σw(|Fo| Ϫ |Fc|)2, where Fo and Fc
are the observed and calculated structure factors. The weighting
scheme used in the last refinement cycles was w ϭ wЈ[1 Ϫ {∆F/
6σ(Fo)}2]2 where wЈ ϭ 1/Σ1nArTr(x) with 3 coefficients Ar for the
Chebyshev polynomial ArTr(x) where x was Fc/Fc(max).[32] Models
reached convergence with R ϭ Σ(|Fo| Ϫ |Fc|)/Σ(|Fo|) and Rw ϭ
[Σw(|Fo| Ϫ |Fc|)2/Σw(Fo)2]1/2, with the values listed in Tables 1 and
2. The criteria for a satisfactory complete analysis were ratios of
rms shift to standard deviation of less than 0.1 and no significant
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coordinates, anisotropic thermal parameters for non-hydrogen
atoms, and atomic coordinates for H atoms have been deposited
with the Cambridge Crystallographic Data Centre as supplement-
ary publication nos. CCDC-165119Ϫ165126. Copies of the data
can be obtained free of charge, on application to the CCDC, 12
Union Road, Cambridge CB2 IE2, UK.
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Acknowledgments
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684
Eur. J. Org. Chem. 2002, 675Ϫ685

A Convenient Procedure for the Preparation of 1-(Diisopropylamino)phospholes
FULL PAPER
[28]
For the desulfuration of phosphole sulfides, see: F. Mathey,
Tetrahedron 1976, 32, 2395Ϫ2400.
for automatic solution of crystal structures by direct methods:
A. Altomare, M. C. Burla, M. Camalli, G. L. Cascarano, C.
Giacovazzo, A. Guagliardi, A. G. G. Moliterni, G. Polidori, R.
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J. Watkin, C. K. Prout, J. R. Carruthers, P. W. Betteridge, R.
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[29]
The torsion angle is defined by the dihedral angle between the
C(2)ϪC(1)ϪC(1Ј) and C(1)ϪC(1Ј)ϪC(2Ј) bonds for com-
pound 8a and C(12)ϪC(11)-(C21) and C(11)ϪC(21)ϪC(22)
bonds for compound 8b.
[32]
[33]
[30] [30a]
J. Omelanczuk, M. Mikolajczyk, J. Am. Chem. Soc. 1979,
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[34]
SIR92, a program for automatic solution of crystal struc-
tures by direct methods: A. Altomare, G. Cascarano, G. Giaco-
vazzo, A. Guagliardi, M. C. Burla, G. Polidori, M. Camalli, J.
Received September 11, 2001
[31b]
Appl. Crystallogr. 1993, 26, 343Ϫ350.
SIR97, a program
[O01435]
Eur. J. Org. Chem. 2002, 675Ϫ685
685