Hydrophosphanation of phenolic aldehydes as facile synthetic approach to catechol-functionalized phosphane oxides and phosphanes

Article abstract of DOI:10.1002/ejic.200600330

Reactions of diphenylphosphane with mono- and dihydroxy-benzaldehydes yield as initial products α-phosphanyl-carbinols that exist according to NMR studies in dynamic equilibrium with the starting materials in solution but are stable in the solid state. Th

Full text of DOI:10.1002/ejic.200600330

FULL PAPER
DOI: 10.1002/ejic.200600330
Hydrophosphanation of Phenolic Aldehydes as Facile Synthetic Approach to
Catechol-Functionalized Phosphane Oxides and Phosphanes
Samir Chikkali[a] and Dietrich Gudat*[a]
Keywords: Phosphanes / Phosphane oxides / P,O ligands / Hydrophosphanation / Rearrangement
Reactions of diphenylphosphane with mono- and dihydroxy- nes were isolated and characterized by analytical and spec-
benzaldehydes yield as initial products α-phosphanyl- troscopic data. The reactions described represent an im-
carbinols that exist according to NMR studies in dynamic proved synthesis for phosphanes with phenol and catechol
equilibrium with the starting materials in solution but are functionalities that are useful for applications as ligands or
stable in the solid state. The facile rearrangement of the ini- supramolecular building blocks.
tial products yields isomeric phosphane oxides which react
with MeI and excess LiAlH4 via deoxygenation to give the (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
corresponding phosphanes. Phosphane oxides and phospha- Germany, 2006)
ation followed by isomerization of the transient α-phos-
Introduction
phanyl-carbinol [pathway (i), Scheme 2].[3] In the context of
The addition of a P–H bond to a carbonyl group is a
our studies on controlling the regioselectivity in hydrophos-
fundamental and synthetically useful reaction of phospho-
phanations[2] it was of interest to elucidate mechanistic as-
rus-hydrogen substituted phosphanes PHnR3–n
. These
pects of this reaction in more detail. In particular, we
wanted to exclude that the product was formed via “in-
verse” addition of the P–H bond of the phosphane and sub-
sequent Michaelis–Arbuzov rearrangement of a transient
phosphinite [pathway (ii) in Scheme 2] which might, in view
of the reactivity of 1 and earlier observations of Michaelis–
Arbuzov rearrangements under conditions similar to the
ones applied here,[4] provide a conceivable alternative to the
standard mechanism. We present here the results of studies
of the transformations of diphenylphosphane and phenolic
aldehydes into phenol-functionalized phosphane oxides,
and demonstrate that these species can easily be converted
into phosphanes. The products thus accessible belong to a
class of multifunctional ligands that have recently attracted
increasing attention as supramolecular building blocks[5]
transformations proceed normally strictly regioselective via
P–C bond formation to give α-phosphanyl-carbinols
(Scheme 1, a) and are used for the synthesis of functional
tertiary phosphanes.[1] We have recently found that N-het-
erocyclic phosphanes 1 react with aldehydes and ketones
via reduction rather than alkylation of the carbonyl moiety
(Scheme 1, b).[2] The reversed regioselectivity (“umpolung”)
has been related to the unique hydride-like polarization of
the P–H bond in 1 which owes to the special bonding situa-
tion in the heterocycle.[2]
Scheme 1. Possible reaction modes of phosphanes with carbonyl
groups.
During a study on hydrophosphanation of carbonyl com-
pounds we noticed that the reaction of diphenylphosphane
with salicylic aldehyde affords a benzylphosphane oxide.
Similar reactions were observed earlier and explained by a
two-step sequence involving a “normal” hydrophosphan-
[a] Institut für Anorganische Chemie, Universität Stuttgart,
Pfaffenwaldring 55, 70550 Stuttgart, Germany
E-mail: gudat@iac.uni-stuttgart.de
Scheme 2.
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S. Chikkali, D. Gudat
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and anchoring groups that are capable of immobilizing the phosphane on the protonated aldehyde. This structural
metal complexes on the surface of a metal oxide support.[6] assignment was further corroborated by satisfactory analyt-
ical data. Attempts to characterize 6a by solution NMR
spectroscopy revealed that the product decomposes upon
Results and Discussion
dissolution in methanol to give a mixture of the starting
materials and the phosphane oxide 5a, an observation that
emphasizes the character of a reaction intermediate for 6a.
The reaction of equimolar amounts of diphenylphos-
phane (2) and salicylic aldehyde (3a) in methanol or ethers
(Et2O, DME) in the presence of catalytic amounts of hydro-
chloric or p-toluenesulfonic acid affords directly the phos-
phane oxide 5a[7] which has been isolated in good yield after
work-up (Scheme 3).
Figure 1. Isotropic line of the solid state CP/MAS 31P NMR spec-
trum of 6a at a spinning speed of 13.2 kHz recorded with high-
power proton decoupling (top trace) and frequency-shifted Lee–
Goldburg decoupling[9] (bottom trace) to suppress homonuclear di-
polar coupling between protons. As the decoupling sequence scales
the heteronuclear coupling by a factor of 0.577, the observed split-
1
ting of 289 Hz corresponds to a value of JPH = 501 Hz.
The above results allow to conclude that the reaction of
2 with salicylic aldehyde involves a “normal” hydrophos-
phanation as the key step. The same regioselectivity was
observed in the acid-catalyzed reaction of 2 with 2,3-di-
hydroxybenzaldehyde (3b). NMR studies allowed in this
case the direct detection of a small amount of the α-phos-
phanyl-carbinol 4b and two further intermediates. The con-
stitution of the latter was assigned as diastereomeric phos-
phonium salts 7b, 7Јb by 2D NMR studies, and dynamic
exchange between all four species was established by a 2D
Scheme 3.
31P NMR studies revealed that 5a remained the only 31P EXSY NMR spectrum. All products were eventually
spectroscopically detectable species beside unreacted 2 and converted into the phosphane oxide 5b which was isolated
minor side products. The latter were not further charac- after work-up and characterized by analytical and spectro-
terized but their chemical shifts precluded assignment as an scopic data. Species similar to 7b, 7Јb have previously been
α-phosphanyl-carbinol. In order to elucidate mechanistic obtained by reaction of diphenylphosphane (2) with formal-
details we set out to find reaction conditions that facilitated dehyde in the presence of strong acids.[1,8]
the detection of a precursor to 5a. In these studies it was
The reaction of 2 with 4-hydroxybenzaldehyde (3c) af-
established that treatment of an ethereal solution of 2 and fords as primary product the α-phosphanyl-carbinol 4c
3a with excess concd. hydrochloric acid lead to immediate which was isolated by precipitation from methanol and
precipitation of a colorless solid which was isolated by fil- characterized by 31P CP/MAS NMR and analytical data.
tration. A solid-state 31P CP/MAS NMR spectrum dis- Key to the structural assignment was the observation of a
closed an isotropic shift (δ31Piso = –0.8) which differs clearly single resonance (δ31P = –7.2) which appears at somewhat
from that of 5a (δ31Piso = 39.3) but resembles that of the α- higher field than that of 6a and shows no splitting due to
phosphanyl-carbinol obtained from reaction of 2 and benz- 1JPH coupling. In contrast to the elusive 2-hydroxy-substi-
aldehyde. A spectrum recorded under conditions that allow tuted carbinol 4a, the signal of 4c is also observable in solu-
to detect scalar couplings to protons revealed a doublet tion 31P NMR spectra although in these solutions, even in
splitting attributable to a one-bond J-coupling (Figure 1, the absence of additional acid, partial decomposition to 2
JPH = 501 Hz). Consequently, we assume that α-phos- and 3c occurs (obviously the acidity of the phenolic OH
phanyl-carbinol hydrochloride 6a is formed which is de- moiety is sufficient to promote an auto-catalytic reaction).
emed to represent the initial product formed by attack of Acidic catalysts promote the complete conversion to phos-
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Hydrophosphanation of Phenolic Aldehydes
FULL PAPER
phane oxide 5c. The same behavior can be observed in the groups is mandatory to obtain reasonable yields of prod-
reaction of 2 with 3,4-dihydroxybenzaldehyde (3d) which af- ucts. Aqueous work-up of the reaction mixture and purifi-
fords 5d as final product. Both 5c and 5d were isolated after cation of the crude products by column chromatography
work-up and characterized by analytical and spectroscopic affords the phosphanes 8a–d as colorless, moderately oxy-
data.
gen-sensitive solids that were characterized by analytical
Finally, the acid-catalyzed reaction of 2 with 3-hydroxy- and spectroscopic data.
benzaldehyde (3e) gives a mixture of dynamically exchang-
ing products the structures of which were assigned to the
phosphanyl-carbinol 4e and the diastereomeric phospho-
nium salts 7e/7eЈ on the basis of a comparison of the ob-
served 31P chemical shifts with those of the products of the
previously described reactions. A 1:1 mixture of 7e/7eЈ pre-
cipitated from the reaction solution and was isolated by fil-
tration. The constitution was confirmed by analytical data;
a slow-spinning technique 31P CP/MAS NMR spectrum
shows the presence of two isotropic signals of equal inten-
sity with negligible chemical shielding anisotropy. The pre-
cipitate dissolved again when the mixture was stirred for
prolonged reaction times, and 31P NMR studies allowed to
detect the formation of the phosphane oxide 5e as final
product which eventually precipitated from the solution and
was characterized by spectroscopic data.
In summary it can be stated that the reactions of the
phosphane 2 with hydroxybenzaldehydes 3a–e proceed via
hydrophosphanation to yield α-phosphanyl-carbinols 4a–e
as initial products. These species are in dynamic equilibrium
with the starting materials and phosphonium salts 7 re-
sulting from acid-promoted reaction with further aldehyde.
The composition of the equilibrium mixtures depends on
the substitution pattern of the aldehydes and lies for 3a–d
which feature at least one OH substituent in 2- or 4-position
largely on the side of the starting materials, whereas for 3e
the formation of the phosphonium salts 7e,eЈ appears to be
favored. As a consequence, the equilibrium concentration
of the adducts 4a–e is rather low, or these species may not
be detectable at all. The reduced stability of the adducts
with respect to the starting materials is attributable to the
electron-releasing nature of the additional hydroxy-substit-
uents which should render the aldehydes weaker electro-
philes and the attack by the nucleophilic phosphane ener-
getically less favorable. Aldehydes with 2-hydroxy substitu-
ents such as 3a,b may further benefit from additional stabi-
Conclusions
It has been confirmed that the reaction of diphenylphos-
phane with phenolic aldehydes is initiated by reversible for-
mation of α-phosphanyl-carbinols. The presence of OH
groups in p- or o-position appears to destabilize the adducts
relative to the starting materials, thus keeping their concen-
tration in the equilibrium mixtures low. The initial adducts
rearrange easily to afford isomeric phosphane oxides which
may further be reduced to the corresponding phosphanes.
The overall reaction sequence permits to access the first alk-
ylphosphane derivatives with tethered catechol and phenol
moieties from readily available starting materials and with-
out the necessity of additional efforts for the protection and
deprotection of the reactive OH groups. This procedure
constitutes a substantial improvement over previously
known synthetic protocols which required often more com-
plicated approaches.[4,11] The utilization of this procedure
should prove useful for the preparation of functional phos-
phanes in applications as chelating ligands or supramolec-
ular building blocks.
Experimental Section
General Remarks: Manipulations were carried out under dry argon
and solvents were dried by standard procedures if required. Solu-
tion NMR spectra were recorded at 30 °C on Bruker Avance 400
(1H: 400.1 MHz, 13C: 100.5 MHz, 31P: 161.9 MHz) or AC 250 spec-
trometers (1H: 250 MHz, 13C: 62.8 MHz, 31P: 101.2 MHz) at
303 K; chemical shifts are referenced to ext. TMS (1H, 13C) or 85%
H3PO4 (Ξ = 40.480747 MHz, 31P). Solid state MAS NMR spectra
were recorded on a Bruker Avance 400 instrument with spinning
rates between 3 and 14 kHz. Cross polarization with a ramp-shaped
contact pulse and mixing times between 3 and 5 ms was used for
lization by strong intramolecular hydrogen bonding. The signal enhancement. MAS NMR spectra aiming at the determi-
1
nation of JP,H couplings were recorded under frequency-shifted
Lee–Goldburg decoupling of homonuclear proton–proton interac-
tions[9] which scales the visible splitting by a factor of 0.577. All
coupling constants are given as absolute values; prefixes i, o, m, p
denote phenyl ring positions of P-C6H5 substituents. The reso-
nances of OH protons were not always detectable, presumably as a
consequence of chemical exchange, and data are not listed when
unequivocal assignment was unfeasible. MS: Varian MAT 711, EI,
70 eV. Elemental analyses: Perkin–Elmer 2400CHSN/O Analyser.
Melting points were determined in sealed capillaries.
observation that all primary adducts may eventually re-
arrange quantitatively to the corresoponding phosphane
oxides 5a–e suggests that the latter are thermodynamically
much more stable so that the isomerization is practically
irreversible. The easy occurrence of this rearrangement is
presumably also facilitated by the stabilization of the re-
sulting transient intermediates by the electron-releasing
phenolic OH substituents.
Deoxygenation of the phosphane oxides 4a–e is readily
achieved by adaptation of an established procedure[10] in-
volving quaternization of the phosphane oxide moiety with
methyl iodide and subsequent reduction with LiAlH4
(Scheme 3). No special protection of the phenol groups is
necessary, however, the use of a sufficient excess of the hy-
General Procedure for the Synthesis of Phenol-Functionalized Phos-
phane Oxides: Diphenylphosphane 2 (12 mmol) was added to a
solution of the appropriate aldehyde 3a–e (12 mmol) in DME
(10 mL). The solution was stirred for five minutes at room tempera-
ture. A catalytic amount of p-toluenesulfonic acid (approx. 3–
dride to achieve complete deprotonation of the acidic OH 6 mmol) was added and the stirring continued for 48 h. The color-
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S. Chikkali, D. Gudat
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less precipitate formed was isolated by filtration, washed twice with
5 mL of DME, and dried in vacuo for 4 h.
ether (10 mL). This mixture was stirred for five minutes at room
temperature and an excess of conc. hydrochloric acid (2 mL,
24 mmol) was added. A colorless precipitate formed immediately.
The reaction mixture was then stirred for further 60 min, the pre-
cipitate filtered off, washed twice with diethyl ether (5 mL), and
dried for 1 h in vacuo. Yield: 1.86 g (90%); m.p. 104 °C; elemental
analysis: C19H18ClO2P (344.78): calcd. C 66.19 H 5.26 Cl 10.28;
found C 66.76 H 5.38 Cl 8.54. 31P{1H}NMR (solid, 162 MHz, CP/
MAS): δiso = –0.8.
2-[(Diphenylphosphinoyl)methyl]phenol (5a): Yield 2.59 g (70%);
m.p. 177 °C; elemental analysis: C19H17O2P (308.32): calcd. C 74.02
H 5.56, found C 73.90 H 5.37. Spectroscopic data are identical with
the values reported in the literature.[7]
3-[(Diphenylphosphinoyl)methyl]benzene-1,2-diol (5b): Yield 3.31 g
(85%); m.p. 194 °C; elemental analysis: C19H17O3P (324.32): calcd.
C 70.37 H 5.28; found C 70.44 H 5.35. 1H NMR (400 MHz,
CDCl3): δ = 8.2 (br., 2 H, OH), 7.74 (m, 4 H, o-H), 7.58 (m, 2 H,
p-H), 7.50 (m, 4 H, m-H), 6.81 (ddd, 3JHH = 8.0 Hz, 4JHH = 1.7 Hz,
4-[(Diphenylphosphanyl)hydroxymethyl]phenol (4c): A solution of
diphenylphosphane (2) (1.43 mL, 8.2 mmol) and 4-hydroxybenzal-
dehyde (3c) (1.00 g, 8.2 mmol) in methanol (10 mL) was stirred for
5 min at room temperature and conc. hydrochloric acid (0.25 mL,
3 mmol) was added. A colorless precipitate formed immediately.
The reaction mixture was stirred for further 60 min, the precipitate
filtered off and dried for 1 h in vacuo. Yield: 2.27 g (90%); m.p.
168 °C; elemental analysis: C19H17O2P (308.32): calcd. C 74.02 H
5.92; found 74.29 H 5.92. 31P NMR (101 MHz, THF): δ = –2.3 (s)
ppm. 31P{1H}NMR (solid, 162 MHz, CP/MAS): δiso = –7.2 ppm.
3
5
6JPH = 1.7 Hz, 1 H, H-6), 6.63 (dt, JHH = 8.0 Hz, JPH = 0.9 Hz,
3
4
4
1 H, H-5), 6.34 (dddm, JHH = 7.7 Hz, JHH = 1.7 Hz, JPH
=
2
1.7 Hz, 1 H, H-4), 3.73 (d, JPH = 12.8 Hz, 2 H, CH2) ppm.
13C{1H} NMR (100 MHz, CDCl3): δ = 148.2 (d, JPC = 2.7 Hz),
143.9 (d, JPC = 4.2 Hz), 133.2 (d, JPC = 2.7 Hz, p-C), 131.6 (d, JPC
= 9.6 Hz, o-C), 130.9 (d, JPC = 100.4 Hz, i-C), 129.4 (d, JPC
=
12.1 Hz, m-C), 122.9 (d, JPC = 6.3 Hz), 121.7 (d, JPC = 1.9 Hz),
119.9 (d, JPC = 8.4 Hz), 114.6 (d, JPC = 2.5 Hz), 35.6 (d, JPC
=
67.1 Hz, CH2) ppm. 31P NMR (101 MHz, CDCl3): δ = 40.4 (s)
ppm. MS (EI = 70 eV): m/z (%) = 324.1 (100) [M+]; 202.1 (38)
[Ph2POH+], 201 (54) [Ph2PO+].
Bis[hydroxy(3-hydroxyphenyl)methyl]diphenylphosphonium Toluene-
sulfonate (7e/7eЈ): A solution of diphenylphosphane (2) (1.43 mL,
8.2 mmol) and 3-hydroxy benzaldehyde (3e) (1.00 g, 8.2 mmol) in
DME (5 mL) was stirred for 5 min at room temperature and p-
toluenesulfonic acid (0.60 g, 3.2 mmol) was added. A colorless pre-
cipitate began to form after 10 min. The reaction mixture was
stirred for 12 h, the precipitate filtered off, washed twice with
DME, and dried for 4 h in vacuo. Yield: 1.73 g (90%); m.p. 121 °C;
elemental analysis: C33H31O7PS (602.64): calcd. C 65.77 H 5.19;
found 65.39 H 5.30. 31P{1H}NMR (solid, 162 MHz, CP/MAS): δiso
= 30.5, 29.9 ppm.
4-[(Diphenylphosphinoyl)methyl]phenol (5c): Yield 2.22 g (60%);
m.p. 223 °C; elemental analysis: C19H17O2P (308.32): calcd. C 74.02
1
H 5.56; found 74.19 H 5.82. H NMR (400 MHz, CDCl3): δ = 8.2
(br., 1 H, OH), 7.76 (m, 4 H, o-H), 7.57 (m, 2 H, p-H), 7.49 (m, 4
2
H, m-H), 6.82 (m, 2 H, C6H4), 6.56 (m, 2 H, C6H4), 3.62 (d, JPH
= 12.2 Hz, 2 H, CH2) ppm. 13C{1H} NMR (100 MHz, CDCl3): δ
2
= 156.9 (d, JPC = 1.7 Hz), 132.7 (s), 131.8 (d, JPC = 9.2 Hz, o-C),
3
131.6 (d, JPC = 4.8 Hz), 129.3 (d, JPC = 11.7 Hz, m-C), 128.6 (d,
General Procedure for the Synthesis of Phenol-Functionalized Phos-
phanes: The appropriate phosphane oxide 5a–d (10 mmol) was dis-
solved in dry THF (100 mL). Methyl iodide (0.69 mL, 11 mmol)
was added via a syringe and the solution stirred for 2 h at room
temperature. The mixture was then cooled to 0 °C and solid LiAlH4
(1.7 g, 45 mmol) added in several small portions. The reaction mix-
ture was warmed to ambient temperature, and stirring was contin-
ued for another 5–6 h. The progress of the reaction was monitored
by TLC. The reaction flask was again cooled to 0 °C, and 50 mL
of 1  hydrochloric acid were added in several portions (the first
few drops had to be added very carefully until the exothermic reac-
tion became less violent). The organic layer was separated and the
aqueous layer washed with ethyl acetate (3×50 mL). The combined
organic phases were dried overnight with Na2SO4 and all volatiles
evaporated in vacuo. The crude products were purified by column
chromatography (silica, petroleum ether:ethyl acetate = 7:3).
JPC = 99.6 Hz), 120.7 (d, JPC = 7.5 Hz), 117.0 (d, JPC = 2.1 Hz),
37.4 (d, JPC = 72.1 Hz, CH2) ppm. 31P NMR (162 MHz, CDCl3):
δ = 32.2 (s) ppm.
4-[(Diphenylphosphinoyl)methyl]benzene-1,2-diol (5d): Yield 3.50 g
(90%); m.p. 192 °C; elemental analysis: C19H17O3P (324.32): calcd.
C 70.37 H 5.28; found C 69.98 H 5.17. 1H NMR (250 MHz,
CDCl3): δ = 7.47 to 7.23 (m, 10 H, C6H5), 6.53 (s, 1 H, C6H3), 6.31
3
3
(d, JHH = 8.1 Hz, 1 H, C6H3), 6.12 (d, JHH = 8.1, 1 H, C6H3),
3.42 (d, 2JPH = 12.9 Hz, 2 H, CH2) ppm. 13C{1H} NMR (62 MHz,
CD3CN/CDCl3): δ = 143.8 (d, JPC = 2.3 Hz), 143.2 (d, JPC
=
3.1 Hz), 131.7 (d, JPC = 1.8 Hz, p-C), 130.3 (d, JPC = 9.4 Hz, o-C),
128.1 (d, JPC = 11.7 Hz, m-C), 126.9 (d, JPC = 101.8 Hz, i-C), 121.2
(d, JPC = 6.1 Hz), 120.9 (d, JPC = 8.4 Hz), 116.6 (d, JPC = 4.8 Hz),
114.4 (d, JPC = 2.3 Hz), 35.1 (d, JPC = 68.2 Hz) ppm. 31P NMR
(101 MHz, CDCl3): δ = 40.4 (s) ppm.
3-[(Diphenylphosphinoyl)methyl]phenol (5e): Yield 2.22 g (60%);
m.p. 198 °C; elemental analysis: C19H17O2P (308.32): calcd. C 74.02
H 5.56; found C 74.10 H 5.60. 1H NMR (250 MHz, CD3CN/
CDCl3): δ = 7.55 (m, 4 H, o-H), 7.40 to 7.25 (m, 6 H, m/p-H), 6.80
2-[(Diphenylphosphanyl)methyl]phenol (8a): Yield 1.81 g (62%); col-
orless oil, elemental analysis: C19H17OP (292.32): calcd. C 78.07 H
5.86; found C 74.33 H 5.91. 1H NMR (250 MHz, [D8]toluene): δ
= 6.8 to 7.5 (m, 10 H, C6H5), 6.80 (t, 1 H, 3JHH = 7.7 Hz), 6.74 (d,
1 H, JHH = 7.7 Hz), 6.61 (d, 1 H, JHH = 7.8 Hz), 6.50 (t, 1 H,
3JHH = 7.5 Hz), 3.32 (s, 2 H, CH2) ppm. 31P{1H} NMR (101 MHz,
[D8]toluene): δ = –15.0 ppm. The 1H NMR spectroscopic data
match those published earlier.[11]
3
3
3
3
(t, JHH = 8.0 Hz, 1 H, H-5), 6.59 (s, 1 H, H-2), 6.44 (d, JHH
=
3
8.0 Hz, 1 H, H-4/6), 6.41 (d, JHH = 8.0 Hz, 1 H, H-4/6), 3.50 (d,
2JPH = 13.4 Hz, 2 H, CH2) ppm. 13C{1H} NMR (62 MHz,
CD3CN/CDCl3): δ = 157.1 (d, JPC = 2.6 Hz), 132.4 (d, JPC
=
2.9 Hz, p-C), 131.2 (d, JPC = 9.5 Hz, o-C), 131.0 (s), 130.9 (d, JPC
= 102.3 Hz, i-C), 129.5 (d, JPC = 2.1 Hz), 128.9 (d, JPC = 11.8 Hz,
m-C), 121.8 (d, JPC = 5.8 Hz), 117.5 (d, JPC = 5.0 Hz), 114.2 (d, JPC
= 2.9 Hz), 37.1 (d, JPC = 67.1 Hz) ppm. 31P{1H}NMR (101 MHz,
CDCl3): δ = 31.4 ppm.
3-[(Diphenylphosphanyl)methyl]benzene-1,2-diol (8b): Yield 1.85 g
(60%); m.p. 82 °C; elemental analysis: C19H17O2P (308.32): calcd.
C 74.02 H 5.56; found C 73.91 H 5.73. 1H NMR (400 MHz,
CDCl3): δ = 7.52 to 7.30 (m, 10 H, C6H5), 6.78 (dm, 3JHH = 7.9 Hz,
1 H, C6H3), 6.64 (tm, JHH = 7.9 Hz, 1 H, C6H3), 6.43 (dm, JHH
= 7.9 Hz, 1 H, C6H3), 6.02 (br., 1 H, OH), 5.86 (br., 1 H, OH),
3.52 (d, 2JPH = 1.7 Hz, 2 H, CH2) ppm. 13C{1H} NMR (100 MHz,
CDCl3): δ = 145.0 (d, JPC = 1.6 Hz), 141.7 (d, JPC = 3.7 Hz), 132.8
3
3
2-[(Diphenylphosphanyl)hydroxymethyl]phenol Hydrochloride (6a):
2-Hydroxybenzaldehyde (3a) (0.64 mL, 6 mmol) was added to a
solution of diphenylphosphane 2 (1.05 mL, 6 mmol) in diethyl
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Hydrophosphanation of Phenolic Aldehydes
FULL PAPER
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2
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Eur. J. Inorg. Chem. 2005, 496–503; N. T. Lucas, A. M.
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1
(d, JPC = 10.5 Hz, CH2) ppm. 31P NMR (101 MHz, CDCl3): δ =
–13.1 (s) ppm. MS (EI = 70 eV): m/z (%) = 308.1 (100) [M+], 186.1
(45) [Ph2PH+], 185.1 (44) [Ph2P+], 183.0 (54) [Ph2P+–H2], 123.1 (45)
[M+–PPh2], 108.1 (54).
4-[(Diphenylphosphanyl)methyl]benzene-1,2-diol (8d): Yield 2.16 g
(70%); m.p. 144 °C; elemental analysis: C19H17O2P (308.32): calcd.
1
C 74.02 H 5.56; found C 74.06 H 5.59. H NMR (400 MHz, [D8]-
THF): δ = 7.68 (s, 1 H, OH), 7.53 (s, 1 H, OH), 7.41 (m, 4 H, o-
4
4
H), 7.33 to 7.25 (m, 6 H, m/p-H), 6.58 (dd, JHH = 1.7 Hz, JPH
=
3
1.7 Hz, 1 H, C6H3), 6.52 (d, JHH = 8.1 Hz, 1 H, C6H3), 6.38 (dm,
3JHH = 8.0 Hz, 1 H, C6H3), 3.31 (s, 2 H, CH2) ppm. 13C{1H} NMR
(100 MHz, [D8]THF): δ = 145.6 (d, JPC = 1.5 Hz), 144.2 (d, JPC
=
2.9 Hz), 139.9 (d, JPC = 16.8 Hz, i-C), 133.3 (d, JPC = 18.7 Hz, m-
C), 129.1 (d, JPC = 8.8 Hz), 128.7 (s, p-C), 128.6 (d, JPC = 6.3 Hz,
o-C), 120.9 (d, JPC = 7.1 Hz), 116.7 (d, JPC = 7.6 Hz), 115.3 (d, JPC
= 1.5 Hz), 35.6 (d, JPC = 15.1 Hz) ppm. 31P{1H} NMR (162 MHz,
CDCl3): δ = –10.4 ppm. MS (EI = 70 eV): m/z (%) = 308.1 (48)
[M+], 186.1 (38) [Ph2PH+], 183.0 (27) [Ph2P+–H2], 123.1 (100) [M+–
PPh2], 108.1 (27).
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D. J. Ruben, Solid State Nucl. Magn. Reson. 1993, 2, 151–163.
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3, 87–90.
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Received: April 11, 2006
Published Online: June 1, 2006
Eur. J. Inorg. Chem. 2006, 3005–3009
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
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