3-Bromo-2-Pyrone: An Alternative and Convenient Route to Functionalized Phosphinines

Article abstract of DOI:10.1002/chem.201602012

The facile access to 3-bromo-2-pyrone allows the preparation of 6-bromo-2-trimethylsilyl-phosphinine by a [4+2] cycloaddition with Me₃Si-C≡P for the first time. The regioselectivity of this reaction could be verified by means of single crystal X-ray diffraction of the corresponding W⁰complex. In the presence of ZnBr₂and dppp (1,3-bis(diphenylphosphino)propane) as a bidentate ligand, the bromo-phosphinine quantitatively undergoes a Negishi cross-coupling reaction with PhLi that selectively leads to 6-phenyl-2-trimethylsilyl-phosphinine. This heterocycle could again be characterized by means of X-ray diffraction as a W⁰complex. These results describe a new and convenient route to 2,6-disubstituted phosphinines that makes use of readily available starting materials.

Full text of DOI:10.1002/chem.201602012

DOI: 10.1002/chem.201602012
Full Paper
&
Coordination Chemistry
3-Bromo-2-Pyrone: An Alternative and Convenient Route to
Functionalized Phosphinines
Marija H. Habicht, Friedrich Wossidlo, Manuela Weber, and Christian Mꢀller*[a]
Abstract: The facile access to 3-bromo-2-pyrone allows the
preparation of 6-bromo-2-trimethylsilyl-phosphinine by
a [4+2] cycloaddition with Me3Si-CꢀP for the first time. The
regioselectivity of this reaction could be verified by means
of single crystal X-ray diffraction of the corresponding W0
complex. In the presence of ZnBr2 and dppp (1,3-bis(diphe-
nylphosphino)propane) as a bidentate ligand, the bromo-
phosphinine quantitatively undergoes a Negishi cross-cou-
pling reaction with PhLi that selectively leads to 6-phenyl-2-
trimethylsilyl-phosphinine. This heterocycle could again be
characterized by means of X-ray diffraction as a W0 complex.
These results describe a new and convenient route to 2,6-
disubstituted phosphinines that makes use of readily avail-
able starting materials.
Introduction
cally much more stable 2,4,6-triphenylphosphinine (2) has al-
ready been described in 1966.[3,4] The beauty of the latter com-
pound is its synthesis by the corresponding pyrylium salt,
which provides access to both 2 and the structurally related
2,4,6-triphenylpyridine. We have recently exploited this syn-
thetic procedure extensively. Important contributions to this
chemistry were made with the synthesis of various donor-func-
tionalized phosphinines as well as axially chiral heterocycles
and their corresponding transition metal complexes.[5] As an
example, the phosphorus derivative of 2,2’-bipyridine (3) has
been successfully used for the preparation of hitherto un-
known phosphinine-based coordination compounds due to
the chelate effect of this P,N-hybrid ligand.[6]
Low-coordinate phosphorus compounds have long been re-
garded as “laboratory curiosities”, as they were considered to
violate the double bond rule and should therefore not be
stable.[1] However, they have recently regained noticeable in-
terest, particularly in the last decade. In fact, it was demon-
strated in several cases that the peculiar characteristic proper-
ties of l3,s2-species can be transferred to more applied re-
search fields, such as homogeneous catalysis, (luminescent)
molecular materials, phosphorus-containing oligomers and
polymers, dendrimers, and supramolecular chemistry.[2] Never-
theless, the accessibility to tailor-made low-coordinate phos-
phorus compounds is an important aspect for potential appli-
cations, as the steric and electronic properties of such species
have to be modified accordingly.
The direct functionalization of phosphinines towards this
type of valuable bi- or polydentate heterocycles is, on the
other hand, not as straightforward as for pyridines. Mathey, Le
Floch, and co-workers and later Bayer et al. have shown that 2-
bromo-4,5-dimethylphosphinine (4) undergoes Pd-catalyzed
Stille- and Negishi-type coupling reactions with various sub-
strates to afford the corresponding 2-substituted phosphinines
of type 5 (Scheme 1).[7,8]
During the last years, our group has been particularly inter-
ested in aromatic l3,s2-phosphinines, which are the higher ho-
mologues of pyridines (Figure 1). While the parent compound
C5H5P (1) has been reported by Ashe et al. in 1971, the kineti-
Figure 1. Parent phosphinine 1 and functionalized heterocycles 2 and 3.
Scheme 1. Pd-catalyzed coupling reactions of bromo-functionalized phos-
phinines 4.
[a] M. H. Habicht, F. Wossidlo, M. Weber, Prof. Dr. C. Mꢀller
Institute of Chemistry and Biochemistry
Freie Universitꢁt Berlin, Fabeckstrasse 34/36, Berlin (Germany)
Fax: (+49)30-838-454004
Unfortunately, the preparation of 4 requires the use of the
very expensive 2,3-dimethylbutadiene as well as the rather
hazardous and potentially carcinogenic dibromomethyldibro-
mophosphine (Br2P-CHBr2).[9] Breit et al. reported on an elegant
alternative for the preparation of donor-functionalized phos-
E-mail: c.mueller@fu-berlin.de
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/chem.201602012.
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uct signal at d=196 ppm in the 31P{1H} NMR spectrum even
after one week of reaction time. We therefore turned our at-
tention to the more reactive phosphaalkyne Me3Si-CꢀP.[15]
Indeed a very fast conversion was found but, much to our sur-
prise, only a rather poor regioselectivity was observed. In fact,
two resonances were found in the 31P{1H} NMR spectrum at
d=244 and 219 ppm in a ratio of 3:7, which we assigned to
the two regioisomers 12 and 13 (or vice versa, Scheme 5).
Scheme 2. Conversion of 6-carboxy-2-pyrone to the chiral 2,6-disubstituted
phosphinine 7.
phinines with the use of 6-carboxy-2-pyrone (6) as the starting
material. In a multistep synthetic procedure, the chiral oxazo-
line-substituted phosphinine
(Scheme 2).[10]
7
could be obtained
This transformation is based on the original procedure for
the preparation of 2-tert-butylphosphinine (10a) described by
Regitz et al.[11] In this reaction, unsaturated cyclic compounds
(such as pyrones) undergo a [4+2] cycloaddition reaction with
tBu-CꢀP under formation of 10a. In few cases, the conversion
of 6-substituted pyrones with tBu-CꢀP to 2,6-disubstituted
phosphinines has also been reported in the literature
(Scheme 3).[12]
Scheme 5. Reaction of 6-chloro-2-pyrone with Me3Si-CꢀP.
Interestingly, this lack of regioselectivity has not been report-
ed in the literature so far for the reaction of 6-substituted 2-py-
rones and phosphaalkynes (vide supra). It is clear, on the other
hand, that steric factors play a role during the addition of the
dienophile to the diene according to Scheme 6.
Scheme 3. [4+2] Cycloaddition of pyrones with tBu-CꢀP.
Inspired by these publications, we set out to combine the
synthetic procedures shown in Schemes 1, 2, and 3 to have
a
convenient access to 2-substituted 6-halophosphinines.
These could be used for further coupling reactions for the
preparation of functionalized phosphinines according to
Scheme 4. However, the [4+2] cycloaddition of a halopyrone
has never been reported in the literature before.
Scheme 6. Intermediates in the formation of 12 and 13 starting from 11.
Thus, we turned our attention to bromo-substituted py-
rones. Unfortunately, however, the corresponding 6-bromo-2-
pyrone is unknown and has not been reported so far. Conse-
quently, we attempted the synthesis of 3-bromo-2-pyrone (16),
in the hope that this compound would regioselectively form
the desired 2-substituted 6-bromo-phosphinine upon reaction
with tBu-CꢀP or Me3Si-CꢀP due to the sterically demanding
bromo substituent. Starting from 3-butenoic acid (14), the
bromo-substituted 2-pyrones 16, 17, and 18 could be pre-
pared according to a modified literature procedure, with the
desired 3-bromo-2-pyrone (16) as the main product
(Scheme 7).[16]
Scheme 4. Synthetic strategy for the preparation of 2,6-disubstituted phos-
phinines.
All compounds were easily separated by column chromatog-
Results and Discussion
1
raphy. The assignment of the H NMR spectra to 16–18 was
We first investigated the reaction of 6-chloro-2-pyrone (11)
with the rather common phosphaalkyne tBu-CꢀP.[13] For this
purpose, compound 11 was prepared according to a procedure
described by Pirkle and Dines starting from glutaconic acid
and phosphorus pentachloride.[14] Unfortunately, this reaction
turned out to be extremely slow, showing only a minor prod-
verified crystallographically, as single crystals suitable for X-ray
diffraction were obtained of all three compounds. The molecu-
lar structures of 16–18 are depicted in Figure 2, along with se-
lected bond lengths and angles for 16.
3-Bromo-2-pyrone (16) was first treated with tBu-CꢀP. Again,
it unfortunately turned out that this reaction is rather slow,
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ly demonstrates that the [4+2] cycloaddition reaction of 16
with Me3Si-CꢀP obviously proceeds regioselectively in the case
of the bromo-substituted 2-pyrone moiety. The new phosphi-
nine could easily be purified by column chromatography and
was isolated as a fairly air and moisture stable orange oil in
1
75% yield. Figure 3 shows the H NMR spectrum of the prod-
1
uct (>95% purity based on H NMR spectroscopy).
Unfortunately, it was not possible to assign the signals in
the aromatic region (see inset) to the correct substitution pat-
tern. We therefore treated the new phosphinine 19 with
[W(CO)6] in THF under irradiation with UV light. Within 2 h, the
starting material was quantitatively converted to the corre-
sponding W0 complex 20 according to 31P{1H} NMR spectrosco-
py and could be isolated as a light yellow solid. The coordina-
Scheme 7. Synthesis of the bromo-pyrones 16–18.
tion compound 20 shows
a single resonance in the
31P{1H} NMR spectrum with additional satellites (1JPÀW
=
139.3 Hz).
Crystals of 20 suitable for X-ray diffraction were obtained
from THF/pentane at T=À358C and the molecular structure
along with selected bond lengths and angles is depicted in
Figure 4. The X-ray crystal structure analysis not only confirms
the mononuclear nature of the coordination compound 20,
but also the presence of 6-bromo-2-TMS-phosphinine (19,
TMS=trimethylsilyl) as ligand. Due to the rather sterically de-
manding TMS group and the Br substituent both in a-position
of the phosphorus heterocycle, the planar aromatic ring is ro-
tated out of the plane defined by three of the five carbonyl li-
gands and the phosphinine moiety (dihedral angle C(10)À
W(1)ÀP(1)ÀC(5)=41.98). A similar conformation has been ob-
served for phosphinine complexes containing a Cr(CO)5 or
W(CO)5 fragment.[17,18]
Figure 2. Molecular structure of 16 in the crystal. Displacement ellipsoids are
shown at the 50% probability level. Selected bond lengths (ꢂ): O(1)À
C(1) 1.373(10), O(2)ÀC(1) 1.213(11), C(1)ÀC(2) 1.451(11), C(2)ÀC(3) 1.349(10),
C(3)ÀC(4) 1.415(10), C(4)ÀC(5) 1.351(11), C(5)ÀO(1) 1.355(9), C(2)À
Br(1) 1.891(7).
showing full conversion of the starting material only after 4 d.
In contrast, the reaction of 16 with Me3Si-CꢀP is considerably
faster, with full conversion already after 6 h in toluene at T=
110 8C. Most strikingly, only one signal could be found in the
31P{1H} NMR spectrum at d=232 ppm, while only two small im-
purities occurred at d=28 and 30 ppm. This observation clear-
The structural characterization of 20 nicely proves that the
phosphinine 19 was regioselectively formed in a facile manner,
Figure 3. 1H NMR spectrum of the phosphinine 19 in CD3CN.
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Scheme 9. Negishi coupling of 19 under formation of 21 and the W0 com-
plex 22.
1
225.4 ppm. Moreover, in the H NMR spectrum of 21, addition-
al signals in the aromatic region can be observed. The yellow
oil was subsequently treated with [W(CO)6] in THF under irradi-
ation with UV light monitored by means of NMR spectroscopy.
Product 22 shows a single resonance in the 31P{1H} NMR spec-
trum with additional satellites (1JPÀW =132.8 Hz).
We were able to obtain crystals of 22 suitable for X-ray dif-
fraction and the molecular structure along with selected bond
lengths and angles are depicted in Figure 5. The X-ray crystal
structure analysis confirms the presence of 6-phenyl-2-TMS-
phosphinine (20) as ligand and the successful Pd-catalyzed Ne-
gishi-coupling between 19 and PhLi in the presence of ZnBr2
and dppp as ligand (Scheme 9).
Figure 4. Molecular structure of 20 in the crystal. Displacement ellipsoids are
shown at the 50% probability level. Selected bond lengths (ꢂ) and angles
(8): P(1)ÀC(1) 1.739(4); C(1)ÀC(2) 1.395(5), C(2)ÀC(3) 1.381(5), C(3)À
C(4) 1.392(5), C(4)ÀC(5) 1.377(5), C(5)ÀP(1) 1.737(4), C(5)ÀBr(1) 1.902(3), C(1)À
Si(1) 1.908(4), P(1)ÀW(1) 2.4819(9), W(1)ÀC(9) 2.011(4); C(9)ÀO(1) 1.138(5);
C(1)ÀP(1)ÀC(5) 103.14.
A comparison of the molecular structures of compounds 20
and 22 in the crystal further reveals that the P(1)ÀW(1) dis-
tance in 20 is shorter than in 22 (2.4819(9) ꢂ vs. 2.5225(8) ꢂ),
while the CÀO bond is longer in 22 than in 20 (1.153(3) ꢂ vs.
Scheme 8. Reaction sequence for the preparation of 20 starting from 3-
bromo-2-pyrone.
starting from 3-bromo-2-pyrone (16) and Me3Si-CꢀP. This
method can, thus, be used for the convenient synthesis of 6-
bromo- and 2-TMS-functionalized phosphinines and the overall
reaction sequence is summarized in Scheme 8.
Finally, we attempted a coupling reaction to convert 6-
bromo-2-TMS-phoshinine (19) into the corresponding product
by means of a CÀC coupling reaction, which has been reported
for bromo-phosphinines before (vide supra and Scheme 9).
It turned out, that the Pd-catalyzed Negishi reaction of 19
with PhLi and ZnBr2 in the presence of dppp (1,3-bis(diphenyl-
phosphino)-propane) as a bidentate ligand leads to the pres-
ence of four very broad signals in the 31P{1H} NMR spectrum at
d=220.6, 220.9, 222.6, and 255.3 ppm after 24 h at T=508C.
These resonances are probably caused by the presence of sev-
eral phosphinine-based metal complexes, while no starting
material could be detected anymore. Indeed, after column
chromatography, a yellow oil was isolated in 80% yield that
shows a single resonance in the 31P{1H} NMR spectrum at d=
Figure 5. Molecular structure of 22 in the crystal. Displacement ellipsoids are
shown at the 50% probability level. Selected bond lengths (ꢂ) and angles
(8):P(1)ÀC(1) 1.735(3); C(1)ÀC(2) 1.398(4), C(2)ÀC(3) 1.390(4), C(3)À
C(4) 1.379(4), C(4)ÀC(5) 1.400(4), C(5)ÀP(1) 1.737(3), C(5)ÀC(6) 1.486(4), C(1)À
Si(1) 1.899(3), P(1)ÀW(1) 2.5225(8), W(1)ÀC(9) 1.996(3); C(19)ÀO(5) 1.153(3);
C(1)ÀP(1)ÀC(5) 105.75.
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[M(79Br)]+, 232.9 (100) [M(81Br)-CH3]+, 230.9 (95) [M(79Br)-CH3]+,
152.9 (15) [M-(BrCH3)]+, 73.0 (75) [Si(CH3)3]+.
1.138(5) ꢂ). Although steric effects cannot be excluded, the ob-
served data nicely reflect the stronger p-accepting character of
the bromo-phosphinine 20 compared to the phenyl-substitut-
ed aromatic heterocycle 22.
[W(CO)5(19)] (20). The phosphinine 19 (21.1 mg, 0.09 mmol) was
dissolved in THF (0.8 mL) and W(CO)6 (30.0 mg, 0.09 mmol) was
added. After irradiation under UV light for 2 h, the dark red reac-
tion mixture was filtered over Celite and the filtrate was concen-
trated in vacuo. The crude product was recrystallized from THF/n-
pentane to give the product 20 as a yellow solid (38 mg,
0.07 mmol, 78%). 1H NMR (400 MHz, CD2Cl2, 208C): d=8.19 (ddd,
J=12.4, 8.8, 0.8 Hz, 1H), 8.02 (ddd, J=28.1, 8.0, 0.6 Hz, 1H), 7.25
(ddd, J=16.1, 8.0, 0.6 Hz, 1H), 0.47 ppm (s, 9H); 13C{1H} NMR
(101 MHz, CD2Cl2, 208C): d=198.6 (d, J=33.0 Hz, 1C), 196,0 (d, J=
9.1 Hz, 1C), 192.0 (s, 1JCÀW =63.5 Hz, 5C, W(CO)5), 168.4 (d, J=
27.1 Hz, 1C), 141.5 (d, J=19.4 Hz, 1C), 128.0 (d, J=30.7 Hz, 1C),
1.70 ppm (d, J=2.9 Hz, 3C); 29Si{1H} NMR (80 MHz, CD2Cl2, 208C):
d=3.43 ppm (d, J=24.0 Hz); 31P{1H} NMR (162 MHz, CD2Cl2, 208C):
d=198.2 ppm (1JPÀW =140.9 Hz).
Conclusion
We have successfully developed a convenient and straightfor-
ward synthetic route to 2,6-disubstituted phosphinines starting
from 3-bromo-2-pyrone. The [4+2] cycloaddition of this com-
pound with the rather reactive phosphaalkyne Me3Si-CꢀP re-
gioselectively as well as quantitatively gives 6-bromo-2-TMS-
phosphinine, under elimination of CO2. This could be verified
by means of X-ray crystallography of the corresponding W0
complex. By making use of the Pd-catalyzed Negishi cross-cou-
pling reaction, the bromo-functionalized phosphinine can
easily be further converted to a 2,6-disubstiuted aromatic
phosphorus heterocycle. As an example, the quantitative for-
mation of 6-phenyl-2-TMS-phosphinine could again be con-
firmed by means of single crystal X-ray diffraction of its W0
complex. Experiments to investigate the scope of the reaction
as well as to use the TMS substituent for further functionaliza-
tions are currently carried out in our laboratories.
6-Phenyl-2-(trimethylsilyl)phosphinine (21). ZnBr2 (360 mg,
1.60 mmol) was dissolved in THF (2 mL) at T=À708C and a solution
of phenyllithium (1.8m) in dibutyl ether (0.56 mL, 1.00 mmol) was
added. After stirring for 30 min at T=À708C, a solution of
Pd2(dba)3 (11.5 mg, 0.01 mmol, 5 mol% in Pd), dppp (10.4 mg,
0.025 mmol, 5 mol%), and 19 (124 mg, 0.50 mmol) in THF (2 mL)
was added dropwise at T=À508C. The reaction mixture was
heated for 24 h at T=508C under constant stirring. Since no start-
ing material (19) could be detected in the 31P{1H} NMR spectrum,
the solvent was removed under reduced pressure. The crude prod-
uct was purified by means of column chromatography over silica
with DCM/n-pentane (1:9) to afford the pure product as a yellow
oil (105 mg, 0.43 mmol, 86%). 1H NMR (400 MHz, [D8]THF, 208C):
d=8.06 (m, 1H), 8.00 (m, 1H), 7.65 (t, J=5.9 Hz, 2H), 7.60 (m, 1H),
7.41 (dt, J=7.2, 5.8 Hz, 1H), 7.34 (t, J=7.2 Hz, 1H), 0.39 ppm (s,
9H); 13C{1H} NMR (101 MHz, [D8]THF, 208C): d=172.1 (d, J=61.6 Hz,
1C), 171.6 (d, J=77.4 Hz, 1C), 144.7 (d, J=22.4 Hz, 1C), 137.7 (d,
J=13.1 Hz, 1C), 134.0 (d, J=10.7 Hz, 1C), 128.6 (d, J=1.9 Hz, 1C),
128.3 (s, 2C), 128.2 (s, 2C), 127.9 (s, 1C), 0.2 ppm (d, J=6.6 Hz, 3C);
31P{1H} NMR (162 MHz, [D8]THF, 208C): d=223.5 ppm; MS (EI, 308C,
80 eV): m/z (%): 244.0 (40) [M]+, 229.0 (100) [M-CH3]+.
Experimental Section
General. All reactions were performed under argon in oven-dried
glassware using modified Schlenk techniques unless otherwise
stated. All common solvents and chemicals were commercially
available. Trimethylsilylphosphaalkyne[15a] and the bromo-substitut-
ed 2-pyrones 16, 17, and 18[16,19] were prepared according to liter-
ature procedures. The solvents were prepared by using the
MBraun Solvent Purification System MB-SPS 800 filled with Al2O3.
Silica gel plates 60 F254 from Merck were used for thin layer chro-
matography and silica gel 60 M (0.04–0.063 mm) from Macherey–
Nagel was used for preparative column chromatography. 1H, 13C,
and 31P NMR spectra were recorded by using a Jeol JNM-ECA 400II
[W(CO)5(21)] (22). The phosphinine 21 (20.0 mg, 0.08 mmol) was
dissolved in THF (0.7 mL) and W(CO)6 (28.8 mg, 0.08 mmol) was
added. After irradiation under UV light for 6 h, the reaction mixture
was filtered over Celite. The dark orange filtrate was concentrated
in vacuo and the crude product was recrystallized from acetonitrile
to give the product 21 as a yellow solid (33 mg, 0.06 mmol, 75%).
1H NMR (400 MHz, CD2Cl2, 208C): d=8.12 (ddd, J=26.4, 8.2, 1.2 Hz,
1H), 7.82 (ddd, J=15.3, 8.4, 1.2 Hz, 1H), 7.45 (m, 6H), 0.54 ppm (s,
9H); 13C{1H} NMR (101 MHz, CD2Cl2, 208C): d=196.4 (d, J=9.0 Hz,
5C), 145.9 (d, J=23.4 Hz, 1C), 143.5 (d, J=13.5 Hz, 1C), 142.2 (d,
J=19.5 Hz, 1C), 138.3 (d, J=10.8 Hz, 1C), 130.9 (d, J=3.5 Hz, 1C),
130.7 (d, J=8.9 Hz, 2C), 129.2 (d, J=0.8 Hz, 2C), 128.8 (d, J=
1.9 Hz, 1C), 126.7 (d, J=32.6 Hz, 1C), 1.9 ppm (d, J=2.9 Hz, 3C);
29Si{1H} NMR (80 MHz, CD2Cl2, 208C): d=2.41 ppm (d, J=23.9 Hz);
1
spectrometer. H and 13C{1H} chemical shifts are referenced to the
residual proton resonance of the deuterated solvents and 31P{1H}
chemical shifts are referenced to an 85% aqueous solution of
H3PO4. Electron impact mass spectra (EI-MS) were recorded on
a Variant MAT 711 spectrometer. For reactions under UV radiation
a UVP Black-Ray B-100AP 100 W high intensity mercury vapor lamp
without filter was used at a distance of 15 cm.
6-Bromo-2-(trimethylsilyl)phosphinine (19). The pyrone 16
(0.93 g, 5.30 mmol) was added to a solution of Me3Si-CꢀP (0.62 g,
5.30 mmol) in toluene (100 mL). After refluxing for 12 h, all volatiles
were removed in vacuo to obtain a dark orange residue. The crude
product was purified by means of column chromatography over
silica with ethyl acetate/n-hexane (1:9) to afford the product 19 as
a yellow oil (0.97 g, 3.93 mmol, 75%). Rf =0.78 (ethyl acetate/n-
31P{1H} NMR (162 MHz, [D8]THF, 208C): d=181.2 ppm (1JPÀW
=
132.8 Hz).
X-ray crystal structure determination of 16. Crystals suitable for
X-ray diffraction were obtained from a saturated solution of 16 in
1
hexane 1:9); H NMR (400 MHz, CDCl3, 208C): d=8.03 (dd, J=8.7,
4.1 Hz, 1H), 7.95 (dd, J=11.4, 7.8 Hz, 1H), 7.36 (ddd, J=8.7, 8.1,
4.1 Hz, 1H), 0.35 ppm (s, 9H); 13C{1H} NMR (101 MHz, CDCl3, 208C):
d=175.3 (d, J=80.2 Hz, 1C), 154.0 (d, J=1.0 Hz, 1C), 137.8 (d, J=
12.7 Hz, 1C), 136.1 (d, J=13.1 Hz, 1C), 130.2 (d, J=19.7 Hz, 1C),
À0.09 ppm (d, J=6.5 Hz, 3C); 29Si{1H} NMR (80 MHz, CDCl3, 208C):
d=83.0 ppm; 31P{1H} NMR (162 MHz, CDCl3, 208C): d=231.5 ppm;
MS (EI, 308C, 80 eV): m/z (%): 248.0 (29) [M(81Br)]+, 246.0 (28)
methanol. Crystallographic data (C5H3BrO2): FW =174.98 gmolÀ1
;
0.60ꢃ0.14ꢃ0.10 mm3; colorless needle, orthorhombic; Pna21; a=
10.6142(6), b=13.0601(8), c=3.9163(2) ꢂ; a=908, b=908, g=908;
V=542.89(5) ꢂ3; Z=4; Dx =2.141 gcmÀ3; m=7.460 mmÀ1. 1704 re-
flections were measured by a D8 Venture Bruker Photon CMOS dif-
fractometer[20] (MoKa radiation; l=0.71073 ꢂ) up to a resolution of
(sinq/l)max =0.63 ꢂ at a temperature of 100 K. 978 reflections were
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unique (Rint =0.069). The structures were solved with SHELXL-
2014[21] by using direct methods and refined with SHELXS-2014[21]
on F2 for all reflections. Non-hydrogen atoms were refined by
using anisotropic displacement parameters. The positions of the
hydrogen atoms were calculated for idealized positions. 73 param-
eters were refined with one restraint. R1 =0.035 for 904 reflections
with I>2s(I) and wR2 =0.117 for 978 reflections; S=1.136; residual
Acknowledgements
The Deutsche Forschungsgemeinschaft (DFG), the European In-
itial Training Network SusPhos (317404), and the Free Universi-
ty of Berlin, Institute of Chemistry and Biochemistry are grate-
fully acknowledged for financial support.
electron density À1.33–1.03 eꢂÀ3
. Geometry calculations and
checks for higher symmetry were performed with the PLATON pro-
gram.[22] CCDC 1476987 (16) contains the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre.[23]
Keywords: coordination chemistry
functionalizations · phosphorus · phosphorus heterocycles
·
cross-coupling
·
[1] P. Jutzi, Chem. Unserer Zeit 1981, 15, 149.
X-ray crystal structure determination of 20. Crystals suitable for
[2] a) P. Le Floch, Coord. Chem. Rev. 2006, 250, 627–681; b) F. Mathey,
Angew. Chem. Int. Ed. 2003, 42, 1578–1602; c) P. Le Floch, F. Mathey,
Coord. Chem. Rev. 1998, 178–180, 771; d) N. Mꢄzailles, F. Mathey, P. Le
Floch, Prog. Inorg. Chem. 2001, 49-50, 455; e) L. Weber, Angew. Chem.
Int. Ed. 2002, 41, 563; Angew. Chem. 2002, 114, 583; f) F. Mathey, P. Le
Floch, Sci. Synth. 2005, 5, 1097; g) C. Mꢀller, D. Vogt, Dalton Trans. 2007,
47, 5505; h) L. Kollꢅr, G. Keglevich, Chem. Rev. 2010, 110, 4257; i) C.
Mꢀller, D. Vogt, C. R. Chim. 2010, 13, 1127–1143; j) J. I. Bates, J. Doug-
las-Tessier, D. P. Gates, Dalton Trans. 2010, 39, 3151–31259; k) C. Mꢀller,
D. Vogt in Catalysis and Material Science Applications, Vol. 36 (Eds.: M.
Peruzzini, L. Gonsalvi), Springer, Heidelberg, 2011; l) C. Mꢀller in Phos-
phorus Ligand Effects in Homogeneous Catalysis: Design and Synthesis
(Eds.: P. C. J. Kamer, P. W. N. M van Leeuwen), Wiley-VCH, Weinheim,
2012; m) J. Douglas-Tessier, E. D. Conrad, G. R. Dake, D. P. Gates in Phos-
phorus Ligand Effects in Homogeneous Catalysis: Design and Synthesis
(Eds.: P. C. J. Kamer; P. W. N. M. van Leeuwen), Wiley-VCH, Weinheim,
2012; n) P. Roesch, J. Nitsch, M. Lutz, J. Wiecko, A. Steffen, C. Mꢀller,
Inorg. Chem. 2014, 53, 9855–9859; o) J. A. W. Sklorz, S. Hoof, N. Rades,
N. De Rycke, L. Kçnczçl, D. Szieberth, M. Weber, J. Wiecko, L. Nyulꢅszi,
M. Hissler, C. Mꢀller, Chem. Eur. J. 2015, 21, 11096–11109; p) C. Mꢀller,
Eur. J. Inorg. Chem. 2016, 569–571; q) J. W. Heinicke, Eur. J. Inorg. Chem.
2016, 575–594; r) J. A. W. Sklorz, C. Mꢀller, Eur. J. Inorg. Chem. 2016,
595–606; s) X. Chen, Z. Li, F. Yanan, H. Grꢀtzmacher, Eur. J. Inorg. Chem.
X-ray diffraction were obtained by cooling down a saturated solu-
tion
of
20
in
THF/n-pentane.
FW =571.05 gmolÀ1
Crystallographic
data
(C13H12O5BrPSiW):
;
0.34ꢃ0.27ꢃ0.08 mm3;
¯
yellow plate, triclinic; P1; a=9.0676(6), b=10.0337(7), c=
10.0485(7) ꢂ; a=73.056(3)8, b=82.106(3)8, g=83.231(3)8; V=
863.33(10) ꢂ3; Z=2; Dx =2.197 gcmÀ3; m=9.183 mmÀ1. 20150 re-
flections were measured by using a D8 Venture Bruker Photon
CMOS diffractometer[20] (MoKa radiation; l=0.71073 ꢂ) up to a res-
olution of (sinq/l)max =0.63 ꢂ at a temperature of 100 K. The reflec-
tions were corrected for absorption and scaled on the basis of
multi-scan-measured reflections by using the SADABS program
(0.15–0.53 correction range).[20] 3549 reflections were unique (Rint
=
0.031). The structures were solved with SHELXL-2014[21] by using
direct methods and refined with SHELXS-2014[21] on F2 for all reflec-
tions. Non-hydrogen atoms were refined by using anisotropic dis-
placement parameters. The positions of the hydrogen atoms were
calculated for idealized positions. 202 parameters were refined
with zero restraints. R1 =0.021 for 3353 reflections with I>2s(I)
and wR2 =0.055 for 3549 reflections; S=1.070; residual electron
density À1.98–1.27 eꢂÀ3. Geometry calculations and checks for
higher symmetry were performed with the PLATON program.[22]
CCDC 1476990 (20) contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge
from The Cambridge Crystallographic Data Centre.[23]
´
˝
2016, 633–638; t) D. Klintuch, K. Krekic, C. Bruhns, Z. Benko, R. Pietsch-
nig, Eur. J. Inorg. Chem. 2016, 718–725; u) Y.-H. Chang, I. Tanigawa, H.
Taguchi, K. Takeuchi, F. Ozawa, Eur. J. Inorg. Chem. 2016, 754–760; v) J.
Moussa, G. R. Freeman, J. A. Gareth Williams, L.-M. Chamoreau, P.
Herson, H. Amouri, Eur. J. Inorg. Chem. 2016, 761–767; w) S. Wu, A. L.
Rheingold, J. A. Golen, A. B. Grimm, J. D. Protasiewicz, Eur. J. Inorg.
Chem. 2016, 768–773.
X-ray crystal structure determination of 22. Crystals suitable for
X-ray diffraction were obtained by cooling down a saturated solu-
tion of 22 in acetonitrile. Crystallographic data (C19H17O5PSiW): FW =
568.23 gmolÀ1; 0.11ꢃ0.11ꢃ0.03 mm3; yellow block, monoclinic;
P21/n; a=11.5174(6), b=9.4421(4), c=18.7154(10) ꢂ; a=908, b=
93.027(2)8, g=908; V=2032.43(17) ꢂ3; Z=4; Dx =1.857 gcmÀ3; m=
5.848 mmÀ1. 35114 reflections were measured by using a D8 Ven-
ture Bruker Photon CMOS diffractometer[20] (MoKa radiation; l=
0.71073 ꢂ) up to a resolution of (sinq/l)max =0.60 ꢂ at a tempera-
ture of 100 K. The reflections were corrected for absorption and
scaled on the basis of multi-scan measured reflections by using the
SADABS program (0.57–0.53 correction range).[20] 3718 reflections
were unique (Rint =0.038). The structures were solved with SHELXS-
2014[21] by using direct methods and refined with SHELXL-2014[21]
on F2 for all reflections. Non-hydrogen atoms were refined by
using anisotropic displacement parameters. The positions of the
hydrogen atoms were calculated for idealized positions. 247 pa-
rameters were refined with zero restraints. R1 =0.019 for 3132 re-
flections with I>2s(I) and wR2 =0.032 for 3718 reflections; S=
0.990; residual electron density À0.71–0.49 eꢂÀ3. Geometry calcula-
tions and checks for higher symmetry were performed with the
PLATON program.[22] CCDC 1476991 (22) contains the supplementa-
ry crystallographic data for this paper. These data can be obtained
free of charge from The Cambridge Crystallographic Data
Centre.[23]
[3] A. J. Ashe III, J. Am. Chem. Soc. 1971, 93, 3293.
[4] G. Mꢆrkl, Angew. Chem. Int. Ed. Eng. 1966, 5, 846; Angew. Chem. 1966,
78, 907.
[5] a) C. Mꢀller, L. Guarrotxena-Lopꢄz, H. Kooijman, A. L. Spek, D. Vogt, Tet-
rahedron Lett. 2006, 47, 2017; b) C. Mꢀller, D. Wasserberg, J. J. M. Weem-
ers, E. A. Pidko, S. Hoffmann, M. Lutz, A. L. Spek, S. C. J. Meskers, R. A.
Janssen, R. A. van Santen, D. Vogt, Chem. Eur. J. 2007, 13, 4548; c) C.
Mꢀller, E. A. Pidko, M. Lutz, A. L. Spek, R. A. van Santen, D. Vogt, Dalton
Trans. 2007, 46, 5372; d) C. Mꢀller, Z. Freixa, M. Lutz, A. L. Spek, D. Vogt,
P. W. N. M. van Leeuwen, Organometallics 2008, 27, 834; e) C. Mꢀller,
E. A. Pidko, A. J. P. M. Staring, M. Lutz, A. L. Spek, R. A. van Santen, D.
Vogt, Chem. Eur. J. 2008, 14, 4899; f) C. Mꢀller, E. A. Pidko, M. Lutz, A. L.
Spek, D. Vogt, Chem. Eur. J. 2008, 14, 8803; g) J. J. M. Weemers, J.
Wiecko, E. A. Pidko, M. Weber, M. Lutz, C. Mꢀller, Chem. Eur. J. 2013, 19,
14458–14469; h) J. J. M. Weemers, W. N. P. van der Graaff, E. A. Pidko, M.
Lutz, C. Mꢀller, Chem. Eur. J. 2013, 19, 8991–9004; i) C. Mꢀller, L. E. E.
Broeckx, I. de Krom, J. J. M. Weemers, Eur. J. Inorg. Chem. 2013, 187.
[6] a) I. de Krom, E. A. Pidko, M. Lutz, C. Mꢀller, Chem. Eur. J. 2013, 19,
7523–7531; b) I. de Krom, L. E. E. Broeckx, M. Lutz, C. Mꢀller, Chem. Eur.
J. 2013, 19, 3676–3684; c) A. Loibl, I. de Krom, E. A. Pidko, M. Weber, J.
Wiecko, C. Mꢀller, Chem. Commun. 2014, 50, 8842–8844; d) C. Mꢀller,
J. A. W. Sklorz, I. de Krom, A. Loibl, M. Habicht, M. Bruce, G. Pfeifer, J.
Wiecko, Chem. Lett. 2014, 43, 1390–1404; e) I. de Krom, M. Lutz, C.
Mꢀller, Dalton Trans. 2015, 44, 10304–10314.
[7] P. Le Floch, D. Carmichael, L. Ricard, F. Mathey, J. Am. Chem. Soc. 1993,
115, 10665–10670.
&
&
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www.chemeurj.org
6
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[8] N. Kostenko, C. Ericsson, M. Engqvist, S. Villa Gonzalez, A. Bayer, Eur. J.
Org. Chem. 2013, 4756–4759.
[16] M. Nakagawa, M. Tonozuka, M. Obi, M. Kiuchi, T. Hino, Synthesis 1974, 7,
510.
[9] a) P. Le Floch, D. Carmichael, F. Mathey, Bull. Soc. Chim. Fr. 1992, 129,
291; b) P. Le Floch, L. Ricard, F. Mathey, Polyhedron 1990, 9, 991; c) P. Le
Floch, D. Carmichael, F. Mathey, Organometallics 1991, 10, 2432.
[10] B. Breit, J. Mol. Catal. A 1999, 143, 143–154.
[11] W. Rçsch, M. Regitz, Z. Naturforsch., B: Anorg. Chem., Org. Chem. 1986,
41, 931.
[12] M. Regitz, P. Binger, Angew. Chem. Int. Ed. Eng. 1988, 27, 1484–1508;
Angew. Chem. 1988, 100, 1541–1565.
[13] G. Becker, G. Gresser, W. Uhl, Z. Naturforsch., B: Anorg. Chem., Org.
Chem. 1981, 86, 16–19.
[17] H. Vahrenkamp, H. Nçth, Chem. Ber. 1973, 106, 2227–2235.
[18] Y. Mao, F. Mathey, Chem. Eur. J. 2011, 17, 10745–10751.
[19] G. Posner, K. Afarinkia, H. Dai, Org. Synth. 1996, 73, 231–239.
[20] Bruker (2010). APEX2, SAINT, SADABS, and XSHELL. Bruker AXS Inc.,
Madison, Wisconsin, USA.
[21] SHELX: G. M. Sheldrick, Acta Crystallogr. Sect. A 2008, 64, 112.
[22] Platon: A. L. Spek, Acta Crystallogr. Sect. D 2009, 65, 148.
[23] CCDC 1476987 (16), 1476990 (20), and 1476991 (22) contain the supple-
mentary crystallographic data for this paper. These data are provided
free of charge by The Cambridge Crystallographic Data Centre.
[14] W. Pieckle, M. Dines, J. Am. Chem. Soc. 1968, 90, 2318.
[15] a) S. M. Mansell, M. Green, R. J. Kilby, M. Murray, C. A. Russell, C. R. Chim.
2010, 13, 1073–1081; b) J. G. Cordaro, D. Stein, H. Rꢀegger, H. Grꢀtz-
macher, Angew. Chem. Int. Ed. 2006, 45, 6159–6162; Angew. Chem.
2006, 118, 6305–6308.
Received: April 29, 2016
Published online on && &&, 0000
Chem. Eur. J. 2016, 22, 1 – 8
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FULL PAPER
New functionalized phosphorus het-
erocycles: A convenient and straightfor-
ward synthetic route to 6-bromo-2-tri-
methylsilyl-phosphinine was developed,
starting from 3-bromo-2-pyrone and
Me3SiÀCꢀP. The quantitative [4+2] cy-
cloaddition of the starting materials
turned out to be regioselective, which
was verified by single crystal X-ray dif-
fraction. A subsequent Pd-catalyzed Ne-
gishi cross-coupling reaction allows fur-
ther access to 2,6-disubstiuted aromatic
phosphorus heterocycles (se figrue).
&
Coordination Chemistry
M. H. Habicht, F. Wossidlo, M. Weber,
C. Mꢀller*
&& – &&
3-Bromo-2-Pyrone: An Alternative and
Convenient Route to Functionalized
Phosphinines
&
&
Chem. Eur. J. 2016, 22, 1 – 8
www.chemeurj.org
8
ꢁ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!