Bis(trifluoroacetyl)phenols and their derivatives in reactions with selected phosphorus(III) compounds

Article abstract of DOI:10.1002/hc.20451

The reactivity of bis(trifluoroacetyl)-phenols toward selected λ³P derivatives was examined. In the case of dialkyl(isocyanato)phosphites, only one of both present trifluoracetyl moieties of substrate was involved. After addition of the phenolic OH moiety across the intermediary formed P=N bond, tri-, tetra-, and pentacyclic α- (trifluoromethyl)phosphoranes were produced in a highly diastereoselective reaction. An unusual deoxygenation of the intermediary hydroxyphosphorane was observed reacting 4-methyl-2,6-bis-(trifluoroacetyl)phenol with diethyl(trimethylsilyl)-phosphite, and the subsequent hydrolysis gave γ-hydroxy-α-(trifluoromethyl)phoshonate. On the contrary, during the reaction of the O-silylated phenol with tris(trimethylsilyl)phosphite, a bis-phosphonate was obtained that underwent heterocyclization to phosphono phosphole system. The mechanistic aspects of the studied reactions, as well as structural features of the synthesized compounds are discussed, based on the multinuclear NMR spectroscopy and X-ray single crystal investigation data.

Full text of DOI:10.1002/hc.20451

Heteroatom Chemistry
Volume 19, Number 5, 2008
Bis(trifluoroacetyl)phenols and Their
Derivatives in Reactions with Selected
Phosphorus(III) Compounds
Dmitri V. Sevenard, Ralf-Matthias Schoth, Olesya Kazakova,
Enno Lork, and Gerd-Volker Ro¨schenthaler
Institute of Inorganic & Physical Chemistry, University of Bremen, Leobener Str.,
28334 Bremen, Germany
Received 12 December 2007; revised 17 March 2008
19:474–482, 2008; Published online in Wiley InterScience
ABSTRACT: The reactivity of bis(trifluoroacetyl)-
(www.interscience.wiley.com). DOI 10.1002/hc.20451
phenols toward selected λ3P derivatives was examined.
In the case of dialkyl(isocyanato)phosphites, only one
of both present trifluoracetyl moieties of substrate was
INTRODUCTION
involved. After addition of the phenolic OH moiety
across the intermediary formed P N bond, tri-, tetra-,
and pentacyclic α-(trifluoromethyl)phosphoranes
were produced in a highly diastereoselective reaction.
An unusual deoxygenation of the intermediary hydrox-
yphosphorane was observed reacting 4-methyl-2,6-bis-
(trifluoroacetyl)phenol with diethyl(trimethylsilyl)-
phosphite, and the subsequent hydrolysis gave
γ -hydroxy-α-(trifluoromethyl)phoshonate. On the
contrary, during the reaction of the O-silylated phenol
with tris(trimethylsilyl)phosphite, a bis-phosphonate
was obtained that underwent heterocyclization
to phosphono phosphole system. The mechanis-
tic aspects of the studied reactions, as well as
structural features of the synthesized compounds
are discussed, based on the multinuclear NMR
spectroscopy and X-ray single crystal investigation
Fluorinated alkyl moieties, especially the CF3 group,
being incorporated into organic molecules, induce
dramatic consequences on the properties of the de-
rived compounds, with an enhanced lipophilicity,
completely changed reactivity and unique metabolic
behavior as the most striking aspects [1]. Thus, the
species bearing a phosphorus atom and a fluorinated
group at the same time is of particular interest for
applications in the pharmaceutical industry, agro-
and medicinal chemistry. Great attention was paid
to α-fluoroalkyl phosphonates with F3-etidronic acid
as the famous member of the family [2]. The most
common procedure to synthesize compounds of this
type consists of the addition of a phosphorus(III)
nucleophile to the trifluoroacetyl group. The pres-
ence of other functions in the molecules of the re-
action partners opens up further possibilities in the
process proceeding, e.g., due to heterocyclization, as
for the enol forms of fluorinated β-dicarbonyls [3].
Reactivity of these compounds as well as behavior
of the structurally related 2-(trifluoroacetyl)phenols
and their derivatives in reactions with phospho-
rus(III) compounds was topics of our previous work
[3,4]. Therefore, our wish to involve the newly
synthesized bis(trifluoroacetyl)phenols [5] in these
ꢀ
C
data.
2008 Wiley Periodicals, Inc. Heteroatom Chem
This work was presented in parts at the 18th International
Symposium on Fluorine Chemistry, Bremen, Germany, July 30–
August 4, 2006.
Correspondence to: Dmitri V. Sevenard, Hansa Fine Chemicals
GmbH, BITZ, Fahrenheit Str. 1, 28359 Bremen, Germany; e-mail:
sevenard@hfc-chemicals.com.
Gerd-Volker
Ro¨schenthaler;
e-mail: gvr@chemie.uni-bremen.de.
c
ꢀ
2008 Wiley Periodicals, Inc.
474

Bis(trifluoroacetyl)phenols and Their Derivatives in Reactions with Selected Phosphorus(III) Compounds 475
investigations is quite logical. The experimental find-
ings are reported and analyzed in this paper.
as the only diastereomer (Scheme 1). Noteworthy,
(trimethylsilyl)ether 6 (easily available via protec-
tion of phenolic oxygen in 1b with chlorotrimethyl-
silane) as well as 2,6-bis(trifluoroacetyl)anisol [5] do
not react with phosphites 2 at all. In this context, the
absence of the expected dimerization of intermedi-
ate B into diazadiphosphetidine [7] gets understand-
able: obviously, the presence of phenolic OH group
is crucial for the success of the reaction.
RESULTS AND DISCUSSION
The examination of the reactivity of compounds 1
was started with dialkyl(isocyanato)phosphites 2 as
phosphorus counterpart. Tricyclic phosphoranes 3,
colorless solids, were formed in 62–98% yields in a
highly diastereoselective reaction (Scheme 1). Prob-
ably, the intermediate A generated from the attack of
phosphorus on the carbonyl group provides product
B. Finally, the phenolic OH moiety adds across the
P N double bond. Despite the presence of two chiral
centers, only one diastereomer is obtained because
of the limitation of the reaction channel numbers [6],
as indicated by NMR spectroscopy, where only one
set of signals has been observed. The reaction of 1,4-
hydroquinone 4 with 2a proceeds similarly to pro-
duce the pentacyclic bis-phosphorane 5 in 72% yield
As stressed above, only one set of signals was
1
found in the H, 13C, 19F, and 31P NMR spectra of
compounds 3 and 5 measured at ambient tempera-
ture. Phosphorus resonances appear in the expected
range −47.4 to −34.5 ppm, being typical for phos-
1
phoranes (λ5σ5P). The characteristic JC-P values of
ca. 124 Hz suggest strongly the trigonal-bipyramidal
structure with equatorial–axial–equatorial arrange-
ment of the two fused five-membered rings and axi-
ally located CF3C carbon [6,8], in which assignment
2
is unambiguous due to splitting with JC-F-coupling
SCHEME 1 Reaction of phenols 1, 4 with dialkyl(isocyanato)phosphites 2.
Heteroatom Chemistry DOI 10.1002/hc

476 Sevenard et al.
constant. In addition, these splittings allow identi-
fication of both CF3C signals in compounds 3; the
chemical shifts (ca. 83 vs. 178.5 ppm), as well as
δF values of the adjacent trifluoromethyl groups (ca.
−72 vs. −73 ppm, respectively) are in accordance
with proposed structure with a free trifluoroacetyl
group and phosphorus in geminal position to the
second CF3 moiety. The axial and equatorial sub-
stituents OAlk can be easily distinguished in the am-
1
bient H and 13C NMR spectra, with the signals at
lower field for the equatorial and at higher field for
the axial position [6,8]. This fact indicates clearly
that pseudorotation processes are slow on the NMR
time scale. An interesting feature of compounds 3
and 5 is the spin–spin interaction of the fluorine
nuclei of the trifluoroacetyl group with a carbon
5
and proton in o-position (4 JC-F ≈ 3, JF-H ≈ 1 Hz).
Probably, the “through-space” mechanism is real-
ized, which requires a syn-periplanar arrangement
of CF3C(O) group with respect to phenolic oxygen.
The asymmetric unit of 3c consists of two dis-
crete species X and Y and two molecules of chlo-
roform, as revealed by X-ray diffraction analysis. In
the molecule X, all the three phosphorus containing
rings are axial-equatorial arranged, with O(2) and
C(8) atoms in axial positions of the slightly distorted
trigonal bipyramid (Fig. 1). The P O distances are
within the expected values for axially and equatori-
ally bonded oxygen atoms in ring systems [9]. Re-
markably, the P(1) O(5) equatorial bond is some-
what longer than P(1) O(2) axial bond [163.9(3)
vs. 162.2(3) pm]. In the oxaphospholene frame-
work, an angle O(5) P(1) C(8) of 89.19(17)◦ was
observed, and all ring atoms are located almost
coplanar with the atoms of the aromatic system
(maximal deviation of 6.7 pm from the ideal plane
for C(8) atom). The trifluoroacetyl moiety is some-
thing turned respective aromatic ring (torsion an-
gle C(10) C(16) C(17) O(6) 30.5◦). Oxazaphosp-
hole cycle features an “envelope” conformation, with
C(8) above P(1) N(1) C(7) O(4) plane by 20.4 pm
(mean deviation of ca. 1.0 pm). The dioxaphosphole
ring shows an “envelope” geometry with C(4) above
the C(1) O(1) P(1) O(2) plane by 53.4 pm (mean
deviation of ca. 4.0 pm).
FIGURE 1 Molecular structure of compound 3c (species X
with arbitrary atoms numbering, thermal ellipsoids with 50%
probability; molecule Y (being practically identical to X struc-
turally) as well as the solvent (CHCl3) molecule are omit-
ted for clarity reason). Selected bond lengths of species X
(pm): P(1) O(1) 158.5(3), P(1) O(2) 162.2(3), P(1) O(5)
163.9(3), P(1) N(1) 167.0(4), P(1) C(8) 194.0(5); selected
bond lengths of species X (◦): O(1) P(1) O(5) 116.13(15),
O(5) P(1) N(1) 117.82(17), O(2) P(1) N(1) 89.56(19),
O(1) P(1) O(2) 93.39(16), O(2) P(1) C(8) 174.12(17),
O(5) P(1) C(8) 89.19(17).
7a to afford heterocycle 8. Our attempts to isolate
this compound failed, but it could be characterized
by NMR spectroscopy. Hydrolysis (water–ethanol)
cleaved the phosphole ring to give phosphonate 9,
similar to the reaction of 2-(trifluoracetyl)phenol
with trimethylphosphite [10]. After recrystalliza-
tion from ethanol, compound 9 was isolated in
hemi-ketal form 10 (Scheme 2), whose molecu-
lar structure was established by X-ray analysis
(Fig. 2).
The δP values of the compounds 8 and 9
(−31.1 and 16.0, respectively) are within the usual
range for the penta- and tetra-coordinated phos-
phorus derivatives, respectively. Similar to parent
o-(trifluoroacetyl)phenol [11], the carbonyl group in
9 is bonded by intramolecular hydrogen bond, as in-
dicated by δH shift of the OH proton (11.3 ppm). In
The reaction of 2b with double excess on di-
ethyl(trimethylsilyl)phosphite 7a delivered an un-
expected result. Instead of bis-phosphonate, the
oxaphosphole 8 was formed (Scheme 2). From a
mechanistic point of view, it can be reasonably pos-
tulated that after initial nucleophilic addition of
phosphorus on the carbonyl group followed by pro-
ton transfer, a phosphorane ring closure takes place
(Scheme 2, C → D → E). The derived hydroxyphos-
phorane E undergoes deoxygenation by an excess of
5
19F NMR spectrum, the JF-H splitting found for the
fluorine nuclei of the trifluoroacetyl moiety results
probably from the “through-space” coupling, and is
in well accordance with the U-type structure [12]
of the intramolecularly H-bonded species. Besides
Heteroatom Chemistry DOI 10.1002/hc

Bis(trifluoroacetyl)phenols and Their Derivatives in Reactions with Selected Phosphorus(III) Compounds 477
SCHEME 2 Reaction of phenol 1b with diethyl(trimethylsilyl)phosphite 7a.
3 JF-P splitting, for the second trifluoromethyl group
an additional splitting in doublet with ca. 10 Hz cou-
pling constant is evident for both compounds 8 and
9, corresponding to the presence of a hydrogen atom
in α-position.
The treatment of silyl ether 6 with a two-fold
excess of 7a or tris(trimethylsilyl)phosphite 7b pro-
vided benz[d][1,2λ5σ4]oxaphospholes 11a and 11b
in 98% and 87% yield, respectively (Scheme 3).
Apparently, a double Arbuzov-type addition occurs
FIGURE 2 Molecular structure of compound 10 (thermal ellipsoids with 50% probability, the disordering of C(40)H3
methyl group is not depicted for clarity). Selected bond lengths (pm): P(1) O(3) 146.0(2), P(1) O(1) 155.8(2), P(1) C(5)
182.0(3); selected bond lengths (◦): O(3) P(1) O(1) 116.48(13), O(1) P(1) O(2) 105.18(13), O(3) P(1) C(5) 114.31(15),
O(1) P(1) C(5) 100.75(14).
Heteroatom Chemistry DOI 10.1002/hc

478 Sevenard et al.
SCHEME 3 Reaction of phenol 1b and (trimethylsilyl)ether 6 with phosphites 7.
reaction partner remained intact. Thus, the λ5P
products appear to be promising substrates for the
further organofluorine modifications, such as Perkin
[13], Wittig/Horner–Wadsworth–Emmons [14] reac-
tions, as well as biomimetic reductive amination
[15].
in this case, and bis-phosphonate F transforms
further into the fused product. Interestingly, phe-
nol 1b behaves toward tris(trimethylsilyl)phosphite
7b the same way to yield phosphono phosp-
hole 11b, in contrast to the reaction with di-
ethyl(trimethylsilyl)phosphite 7a (Scheme 3).
Two sets of signals manifest themselves in NMR
spectra of 11a to indicate the presence of two di-
astereomers in ca. 65:35 ratio. In 31P NMR spectrum,
two kinds of phosphonate resonances are obvious
(δP = 11.5, 12.4 vs. 28.3). The quartets (3 JP-F = 5.1 Hz)
in higher field were attributed to the phosphorus in
oxaphosphole ring. Analogously, signals of two dif-
EXPERIMENTAL
Appropriate precautions for handling moisture-
and oxygen-sensitive compounds were observed
throughout this work. Melting points are uncor-
rected. MS (m/z, intensity (%), species): EI (70
eV), Finnigan MAT-8200 and MAT-95 spectrome-
ters. High-resolution mass spectra (HRMS): peak-
matching method, Finnigan MAT-95 spectrometer.
NMR spectra: Bruker AC-80, Bruker DPX-200, and
Bruker AMX-360 spectrometers [80.1 and 200.1
(1H), 50.3 (13C), 75.4 and 188.3 (19F), 32.4, 81.0,
145.8 (31P) MHz]; Me4Si-(1H and 13C), CCl3F-(19F)
and H3PO4-(31P) scales. 1H NMR chemical shifts
in CDCl3, CD3CN, and C6D6 solutions are refer-
enced to the signal at 7.25, 1.94, and 7.15 ppm, re-
spectively, 13C-NMR chemical shifts in CDCl3 solu-
tions are referenced to the central line of solvent
signal at 77.0 ppm. Reaction progress was mon-
itored by 19F and 31P NMR spectroscopy for the
samples from the reaction mixtures (without lock).
X-ray single crystal determination for compounds
3c and 10: at −100(2)◦C, Siemens-P4 diffractome-
ter with a graphite monochromated Mo Kα radia-
tion (λ 71.073 pm) and the low-temperature device
LT2. The structures were solved by direct methods
and refined by full-matrix least squares at F2 with
the SHELXL-97 program package [16]. All non-H
3
ferent trifluoromethyl moieties split with JF-P cou-
pling constants appear in 19F NMR spectra of both
diastereomers. Presumably, the doublets observed in
lower field (δF = −78.7 vs. −74.8, −72.6) correspond
to the trifluoromethyl group attached to heterocycle.
Only one of possible diastereomers could be de-
tected in C6D6 solution of 11b, confirmed by only
one set of signals in all NMR spectra measured. Sig-
nals in the 31P NMR spectrum appear in significantly
higher yield when compared to 11a, namely at −2.9
and −2.4 ppm. This difference can be explained via
cumulative electron donor influence of trimethylsilyl
moieties.
In summary, the behavior of bis(trifluoro-
acetyl)phenols and their derivatives in reactions
with dialkyl(isocyanato)phosphites and (trimethylsi-
lyl)phosphites was studied. The polyfunctional
nature of starting compounds causes the synthet-
ical manifold: a wide range of valuable phospho-
nates and phosphoranes bearing CF3 substituents
in α-position was obtained, among them bi-, tri-,
tetra-, and pentacyclic products. In several cases,
the second trifluoroacetyl group of the phenolic
Heteroatom Chemistry DOI 10.1002/hc

Bis(trifluoroacetyl)phenols and Their Derivatives in Reactions with Selected Phosphorus(III) Compounds 479
5
atoms were refined anisotropically, the NH proton
3F, CF3C(O), JF-H = 1.4 Hz), −72.01 (d, 3F, 5-CF3,
3 JF-P = 2.8 Hz). 31P NMR (CDCl3): δ = −46.8 m.
was refined isotropically, and the positions of the
other hydrogen atoms were calculated as a riding
model. Crystallographic data have been deposited
with the Cambridge Crystallographic Data Centre.
Elemental analyses: Microanalytisches Beller La-
bor, Go¨ttingen, Germany. All chemicals are com-
mercially available and were used as purchased un-
less otherwise specified. Reactions in dried diethyl
ether (distilled from sodium/benzophenone ketyl)
were performed in oven-dried glassware under a
static nitrogen atmosphere. Triethylamine was dried
over KOH and distilled. Starting phenols 1 [5] and
phosphites 2a [17], 2b [18], and 7 [19] were prepared
according to the published procedures.
CCDC-657297 and CCDC-657296 contain the
supplimentary crystallographic data for the struc-
tures 3c and 10, respectively. These data can be ob-
tained free of charge via www.ccdc.cam.ac.uk/conts/
retrieveing.html (or from the Cambridge Crystallo-
graphic Data Centre, 12 Union Road, Cambridge
CB2 1EZ, UK; fax: +44 1223 336033; or deposit@
ccdc.cam.ac.uk).
31P{ H} NMR (CDCl3): δ = −46.8 (q, JP-F = 2.6 Hz).
MS (EI); m//z = 449 (20) [M+], 406 (56) [M –
CONH]+, 404 (64) [M – EtO]+, 380 (12) [M – CF3]+,
376 (100) [M – CO – EtO]+, 352 (30) [M – CF3CO]+,
330 (76) [M – CF3 – EtOH]+, and other fragments.
HRMS for C15H14F6NO6P; Calcd: 449.0463. Found:
449.0459.
1
3
6,7-Benzo-1,1-diethoxy-10-methyl-12-trifluoroacet-
yl-5-trifluoromethyl-4,8-dioxa-2-aza-1λ5σ5-phospha-
bicyclo[3.3.0]oct-6-en-3-one (3b): Recrystallization
of crude product from heptane at −30◦C yielded
62% of yellowish crystals (mp 131–133◦C (sealed
capillary)). H NMR (CDCl3): δ = 1.27 (td, 3H, CHa3x,
1
3 JH-H = 7.2, JH-P ≈ 1.4 Hz), 1.31 (td, 3H, CHe3q,
4
3 JH-H = 7.0, JH-P ≈ 1.6 Hz), 2.40 (s, 3H, 10-CH3),
4
3.85–4.03 (m, 1H, OCHHax), 4.07–4.32 (m, 3H,
eq
OCHHax, CH2 ), 7.38 (d, 1H, NH, JH-P = 9.3 Hz),
2
7.70, 7.72 (two s, each 1H, 9,11-H). 13C{ H} NMR
1
(CDCl3): δ = 15.6 (d, CHa3x, JC-P = 8.1 Hz), 16.0 (d,
3
CHe3q, 3 JC-P = 9.9 Hz), 20.9 (s, 10-CH2), 62.3 (d, CHax,
2
2 JC-P = 10.2 Hz), 67.8 (d, CHeq, JC-P = 15.5 Hz),
2
2
1
2
83.0 (dq, C-P, JC-P = 124.2, JC-F = 31.3 Hz), 116.0
(q, CF3C(O), JC-F = 291.5 Hz), 116.9 (d, CAr,
1
Standard Procedure for the Preparation
of Phosphoranes (3)
JC-P = 12.0 Hz), 124.1 (d, CAr, JC-P = 14.8 Hz), 124.2
(q, 5-CF3, JC-F = 280.7 Hz), 133.4 (s, CAr), 135.2 (d,
1
CAr, JC-P = 10.2 Hz), 151.4 (d, 7-C, JC-P = 6.0 Hz),
2
To a well-stirred solution of the appropriate phenol 1
(1.7 mmol) in dried diethyl ether (20 mL), freshly dis-
tilled isocyanatophosphite 2 (1.7 mmol) was added.
The resulting pale yellow solution was stirred for 1 h
at room temperature, and the solvent was removed
under reduced pressure to afford a yellowish solid
(3b,c) or yellow oil which solidified (3a).
2
151.8 (d, 3-C, JC-P = 30.7 Hz), 178.6 (q, CF3 C(O),
2 JC-F = 36.1 Hz). 19F NMR (CDCl3): δ = −73.08 (d, 3
5
F, CF3C(O), JF-H = 1.4 Hz), −71.89 (d, 3F, 5-CF3,
3 JF-P = 2.9 Hz). 31P NMR (CDCl3): δ = −46.5 m.
31P{ H} NMR (CDCl3): δ = −46.5 (q, JP-F = 2.9 Hz).
MS (EI): m/z = 463 (44) [M+], 420 (64) [M – CONH]+,
418 (66) [M – EtO]+, 394 (20) [M – CF3]+, 390 (88)
[M – CO – EtO]+, 366 (40) [M – CF3CO]+, 344 (100)
[M – CF3 – EtOH]+, and other fragments. HRMS for
C16H16F6NO6P; Calcd: 463.0620. Found: 463.0612.
1
3
6,7-Benzo-1,1-diethoxy-12-trifluoroacetyl-5-trifluo-
romethyl-4,8-dioxa-2-aza-1λ5σ5-phosphabicyclo[3.3.0]-
oct-6-en-3-one (3a): Yield 98% as yellow crystals
(melting interval 68–74◦C (sealed capillary)). 1H
3
NMR (CDCl3): δ = 1.28 (td, 3H, CHa3x, JH-H = 6.6,
6,7-Benzo-10-methyl-1,1-(1ꢁ,1ꢁ,2ꢁ,2ꢁ -tetramethyl-
ethylene-1ꢁ,2ꢁ-dioxy)-12-trifluoroacetyl-5-trifluoromet-
hyl-4,8-dioxa-2-aza-1λ5σ5-phosphabicyclo[3.3.0]oct-6-
en-3-one (3c): Recrystallization of crude product
from chloroform yielded 62% of yellowish crystals
(mp 180◦C (sealed capillary)). 1H NMR (C6D6):
δ = 1.32, 1.41 (two s, each 6H, 1ꢁ,1ꢁ,2ꢁ,2ꢁ-CH3), 2.41
4 JH-P ≈ 1.5 Hz), 1.32 (td, 3H, CH3eq, 3 JH-H = 6.6, 4 JH-P
≈
1.6 Hz), 3.86–4.03 (m, 1H, OCHHax), 4.04–4.34 (m,
3H, OCHHax, CH2eq), 7.01 (d, 1H, NH, 2 JH-P = 9.3 Hz),
3
7.27 (t, 1H, 10-H, JH-H = 8.1 Hz), 7.93, 7.94 (two
3
1
d, each 1H, 9,11-H, JH-H = 7.8 Hz). 13C{ H} NMR
(CDCl3): δ = 15.6 (d, CHa3x, JC-P = 8.1 Hz), 16.1 (d,
3
CHe3q, JC-P = 9.9 Hz), 62.5 (d, CHax, JC-P = 9.9 Hz),
3
2
2
(s, 3H, 10-CH3), 7.20 (d, 1H, NH, JH-P = 9.3 Hz),
2
67.9 (d, CHe2q, JC-P = 15.5 Hz), 82.8 (dq, C-P,
2
7.71 (s, 2H, 9,11-H). 19F NMR (C6D6): δ = −77.36 (s,
3F, CF3C(O)), −75.19 (s, 3F, 5-CF3). 31P NMR (C6D6):
δ = −34.5 m. MS (EI): m/z = 490 (6) [M + H]+, 446
(12) [M – CONH]+, 420 (2) [M – CF3]+, 373 (18) [M
– Me2CCMe2]+, 304 (18) [M – CF3 – Me2CCMe2]+,
and other fragments. Anal. Calcd. for C18H18F6NO6P
(489.31): C, 44.19; H, 3.71; F, 23.3; P, 6.33. Found:
C, 44.63; H, 3.85; F, 22.8; P, 6.63.
1 JC-P = 124.1, JC-F = 31.5 Hz), 116.0 (q, CF3C(O),
2
1 JC-F = 291.5 Hz), 117.1 (d, CAr, JC-P = 12.4 Hz), 123.4,
124.2 (two s, CAr), 121.1 (q, 5-CF3, JC-F = 281.2 Hz),
1
133.3 (q, 9-C, JC-F = 2.9 Hz), 134.7 (d, CAr,
4
2
JC-P = 13.0 Hz), 153.5 (d, 7-C, JC-P = 6.2 Hz),
2
154.1 (d, 3-C, JC-P = 31.3 Hz), 178.4 (q, CF3C(O),
2 JC-F = 36.1 Hz). 19F NMR (CDCl3): δ = −73.01 (d,
Heteroatom Chemistry DOI 10.1002/hc

480 Sevenard et al.
X-ray
Crystal-Structure
Analysis
of
3c.
mmol) was added dropwise. After addition was com-
pleted, the volatile materials were removed in vacuo
to leave mixture of 1,2-oxaphospholane 8 and di-
ethyl(trimethylsilyl)phosphate (δP = 1.8). After treat-
ment with aqueous ethanol (ca. 90%) for 1 h at
room temperature, the mixture was concentrated in
vacuo to 3 mL and left overnight. The formed pre-
cipitate was collected by filtration to afford 9 as col-
orless crystals, 2.5 g (60%) (mp 105◦C). Compound
Diffraction-quality crystals were selected from
analytical sample obtained via recrystallization
of the crude product from chloroform. Colorless
prisms; C19H19Cl3F6NO6P (608.67); 0.75 × 0.30
× 0.30 mm3, triclinic P-1 with a = 964.10(10),
b= 1695.7(2), c= 1787.7(2) pm, α = 61.690(10),
β = 82.160(10),
γ = 89.950(10)◦,
V = 2.5421(5)
nm3, D = 1.590 g cm−3, Z = 4, difference electron
1
−3
˚
8. H NMR (C6D6): δ = 0.03 (s, 9H, Si(CH3)3), 0.80–
density 0.650 and −0.509 e A . Index range
−1 ≤ h ≤ 11, −17 ≤ k ≤ 17, −21 ≤ l ≤ 21, 2θ range
2.62 to 25.00◦, reflections measured 10,255, unique
reflections 8472 (R(int) = 0.0452). Completeness
to θmax = 25.00◦: 94.4%, data/restraints/parameter
8472/0/670. Goodness-of-fit at F2 0.756; final R-
1.85 (m, 6H, 2CH2CH3), 2.18 (s, 3H, ArCH3), 3.88
∗
(m, 1H, CH), 3.50–4.85 (m, 4H, 2CH2CH3), 7.22–
8.00 (m, 2H, 4,6-H). 19F NMR (C6D6): δ = −68.20
(dd, 3F, 3-CF3, 3 JF-P = 14.3, 3 JF-H = 9.9 Hz), −77.85 (d,
5
1
3F, CF3C(O), JF-H = 1.3 Hz). 19F{ H} NMR (C6D6):
3
δ = −68.17 (d, 3F, 3-CF3, JF-P = 14.5 Hz), −77.85 (s,
values (I > 2σ(I)): R = 0. 0.0507, wR2 = 0.1055;
1
3F, CF3C(O)). 31P{ H} NMR (C6D6): δ = −31.1 (q,
1
R-value (all reflections): R = 0.1344, wR2 = 0.1220.
1
3 JP-F = 14.8 Hz).
Compound 9. 1H NMR (C6D6): 0.65–1.15 (m,
6H, 2 CH2CH3), 2.10 (s, 3H, ArCH3), 3.55–4.45
6,6,15,15-Tetraethoxy-2,11-bis(trifluoromethyl)-
3,7,12,16-tetraoxa-5,14-diaza-6λ5σ5,15λ5σ5-
diphosphapentacyclo[13.3.0.02,6.01,8.010,17]-
octadeca-1(8),9,17-trien-4,13-dione (5)
∗
2
(m, 4H, 2CH2CH3), 3.60 (dq, 1H, CH, JH-P = 48.1,
3 JH-F = 11.4 Hz), 7.14–7.98 (m, 2H, 4,6-H), 11.3 (br.s,
1H, OH). 19F NMR (C6D6): δ = -65.60 (dd, 3F, 3-CF3,
3 JF-H = 11.4, JF,P = 9.7 Hz), −74.53 (d, 3F, CF3C(O),
3
A solution of freshly distilled (diethyl)isocyanatop-
hosphite 2a (1.1 g, 6.7 mmol) in dried diethyl ether
(7 mL) was added dropwise to a well-stirred solution
of hydroquinone 4 (1 g, 3.3 mmol) in diethyl ether
(20 mL) maintained at 0◦C. The resulting solution
was allowed to warm and stirred for 1 h at room
temperature. The mixture was cooled to −30◦C, and
dried pentane (20 mL) was added. The precipitated
solid was filtered, washed with pentane (2 × 7 mL),
and dried to give 5 (1.5 g, 72%) as a pale yellow
moisture-sensitive powder. To obtain an analytical
sample, the crude product was washed successively
with acetone and diethyl ether and dried in vacuo to
furnish white powder, (mp 180◦C (decomp., sealed
capillary)). 1H NMR (CD3CN): δ = 1.19–1.32 (m, 12H,
4CH3), 3.81–4.07 (m, 4H, 2CH2), 4.08–4.29 (m, 4H,
5 JF-H = 2.6 Hz). 19F{ H} NMR (C6D6): δ = −65.60 (d,
1
3
3F, 3-CF3, JF-P = 9.7 Hz), −74.54 (s, 3F, CF3C(O)).
31P{ H} NMR (C6D6): δ = 16.0 (q, 3 JP-F = 9.4 Hz). MS
1
(EI): m/z = 422 (84) [M+], 394 (18) [M – CO]+, 354
(28) [M – CF3 + H]+, 353 (14) [M – CF3]+, 325 (18)
[M – CF3CO]+, 284 (22) [M – 2CF3]+, 127 (100),
45 (45) [EtO+], and other fragments. Anal. Calcd
for C15H17F6O5P (422.26): C, 42.67; H, 4.06; P, 7.34.
Found: C, 42.63; H, 4.61; P, 7.02.
X-ray Crystal-Structure Analysis of Hemi-ketal
10. Diffraction-quality crystals were grown by
slow crystallization of 9 from ethanol. Color-
less prisms; C17H23F6O6P (468.32); 0.80 × 0.80
× 0.70 mm3, triclinic P-1 with a = 818.60(10),
b= 1006.70(10), c= 1467.1(2) pm, α = 70.010(10),
β = 85.680(10), γ = 66.750(10)◦, V = 1.0414(2) nm3,
D = 1.493 g cm−3, Z = 2, difference electron den-
2
2CH2), 7.18 (d, 2H, 2NH, JH-P = 9.8 Hz), 7.35 (q,
2H, HAr, JH-F ≈ 1.0 Hz). 19F NMR (acetone-d6 +
5
C6D6, ca. 3:2): δ = −70.88 s. 31P{ H} NMR (acetone-
1
3
−3
˚
d6 + C6D6, ca. 3:2): δ = −47.4 (q, JP-F = 2.7 Hz).
sity 0.247 and −0.369 e·A . Index range −1 ≤
h ≤ 9, −10 ≤ k ≤ 11, −17 ≤ l ≤ 17, 2θ range 2.71
to 24.99◦, reflections measured 4503, unique
reflections 3600 (R(int) = 0.0501). Completeness
to θmax = 24.99◦: 98.2%, data/restraints/parameter
3600/0/293. Goodness-of-fit at F2 0.859; final R-
MS (EI); m/z = 628 (28) [M+], 583 (50) [M – EtO]+,
29 (100) [Et+], and other fragments. HRMS for
C20H24F6N2O10P2; Calcd: 628.0810. Found: 628.0816.
2,2-Diethoxy-5-methyl-7-trifluoroacetyl-3-
trifluoromethyl-2-(trimethylsiloxy)benz[d]-
[1,2λ5σ5]oxaphospholane (8) and diethyl
1-(2-hydroxy-3-trifluoroacetyl-5-methylphenyl)-
2,2,2-trifluoroethylphosphonate (9)
values (I > 2σ(I)): R = 0.0491, wR2 = 0.1000; R-
1
value (all reflections): R = 0.0971, wR2 = 0.1121.
1
4-Trimethylsiloxy-3,5-bis(trifluoroacetyl)toluene
(6)
To a well-stirred solution of phenol 1b (3 g, 10
mmol) in dried diethyl ether (10 mL), freshly dis-
tilled diethyl(trimethylsilyl)phosphite 7a (4.2 g, 20
To a stirred solution of phenol 1b (3 g, 10 mmol)
in dried diethyl ether (10 mL) dried triethylamine
Heteroatom Chemistry DOI 10.1002/hc

Bis(trifluoroacetyl)phenols and Their Derivatives in Reactions with Selected Phosphorus(III) Compounds 481
(1 g, 10 mmol) was added dropwise, followed by
tris(trimethylsilyl)phosphite 7b (6 g, 20 mmol) was
added dropwise at room temperature. After stirring
for 1 h, the volatile materials were evaporated in
vacuo to afford 11b (7 g, 87%) as a yellowish oil. 1H
NMR (C6D6): δ = −0.15 (s, 18H, 2Si(CH3)3), −0.13 (s,
9H, Si(CH3)3), 0.17 (s, 18H, 2Si(CH3)3), 2.29 (s, 3H,
ArCH3), 7.18–7.42 (m, 2H, 4,6-H). 19F NMR (C6D6):
δ = −71.83 (d, 3F, exo-CF3, 3 JF-P = 6.4 Hz), −70.40 (d,
chlorotrimethylsilane (1.1 g, 10 mmol). The precip-
itated triethylammonium chloride was filtered off,
the filtrate evaporated in vacuo to give 6 (3.6 g,
1
97%) as a yellowish oil. H NMR (CDCl3): δ = 0.18
(s, 9H, Si(CH3)3), 2.42 (s, 3H, ArCH3), 7.63 (s, 2H,
2,4-H). 19F NMR (CDCl3): δ = −77.01 s. Anal. Calcd
for C14H14F6O3Si (372.34): C, 45.16; H, 3.79; F, 30.6.
Found: C, 45.25; H, 3.96; F, 30.6.
3
1
3F, endo-CF3, JF-P = 6.3 Hz). 31P{ H} NMR (C6D6):
3
δ = −2.8 (q, 1P, endo-P(O), JP-F = 5.6 Hz), −2.4 (q,
3
1P, exo-P(O), JP-F = 5.8 Hz). MS (EI); m/z = 824 (4)
[M + H2O+], 225 (50) [P(O)(OTMS)2+], 211 (100),
147 (98) [Me3SiOSiMe2+], 73 (74) [Me3Si+], and other
fragments. Anal. Calcd for C26H50F6O8P2Si5 (807.04):
C, 38.70; H, 6.24; F, 14.1. Found: C, 38.68; H, 6.58;
F, 13.9.
Diethyl 2,2,2-trifluoro-1-[2-ethoxy-5-methyl-3-
trifluoromethyl-3-(trimethylsiloxy)benz[d]-
[1,2λ5σ4]oxaphospholan-2-one-7-yl]-1-
(trimethylsiloxy)ethylphosphonate (11a)
To a stirred solution of silyl ether 6 (3.7 g, 10 mmol)
in dried diethyl ether (10 mL) freshly distilled di-
ethyl(trimethylsilyl)phosphite 7a (4.2 g, 20 mmol)
was added dropwise at room temperature. After stir-
ring for 1 h, the volatile materials were evaporated
in vacuo to afford 11a (6.6 g, 98%) as a yellow-
ish oil. The NMR spectra display the presence of
two diastereomers (M and N) in ca. 65:35 ratio,
ACKNOWLEDGMENTS
We are grateful to Dr. K.-H. Hellberg, Solvay Fluor
und Derivate GmbH, Hannover, Germany, and Dr.
M. Braun, Solvay Organics GmbH, Bensberg, Ger-
many, for the generous gift of chemicals. Mrs.
D. Kemken, Mrs. I. Erxleben, Dr. P. Schulze, and Dr.
T. Du¨lcks, Institute of Organic Chemistry, Univer-
sity of Bremen, Germany, are thanked for recording
mass spectra, and Mr. P. Brackmann, Institute of In-
organic & Physical Chemistry, University of Bremen,
Germany, for the X-ray diffraction measurements.
1
respectively. Isomer M. H NMR (C6D6): δ = −0.18
(s, 9H, Si(CH3)3), −0.01 (s, 9H, Si(CH3)3), 0.91–1.29
(m, 6H, 2CH2CH3), 2.15 (s, 3H, ArCH3), 3.77–4.28
(m, 4H, 2CH2CH3), 7.00–7.22 (m, 2H, 4,6-H). 19F
3
NMR (C6D6): δ = −78.66 (d, 3F, exo-CF3, JF-P = 5.3
1
Hz), −72.61 (d, 3F, endo-CF3, 3 JF-P = 5.3 Hz). 31P{ H}
3
NMR (C6D6): δ = 11.5 (q, 1P, endo-P(O), JP-F = 5.1
3
Hz), 28.3 (unresolved q, P, exo-P(O), JP-F ≈ 5 Hz).
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Heteroatom Chemistry DOI 10.1002/hc