Efficient synthesis of tetradecafluoro-4-phenylheptan-4-ol by a Cannizzaro-type reaction and application of the alcohol as a bulky Martin ligand variant for a new anti-apicophilic phosphorane

Article abstract of DOI:10.1039/c0dt00539h

Alcohols 8 bearing two identical perfluoroalkyl groups were prepared by the reaction of the corresponding perfluoroalkyl phenyl ketones 7 with 0.5 equivalents of t-BuOK via Cannizzaro-type disproportionation. Utilizing the new bulky bidentate ligand with two n-C₃F₇ groups generated from 8c, anti-apicophilic phosphorane 5a and its stable isomer 6a were synthesized. The crystal structures of 5a and 6a were slightly affected by the steric repulsion of heptafluoropropyl groups. Kinetic studies on the isomerization of 5a to 6a showed that the new ligand was effective for decreasing the isomerization rate compared with its C₂F₅ analog 3a to about half.

Full text of DOI:10.1039/c0dt00539h

View Article Online / Journal Homepage / Table of Contents for this issue
PAPER
www.rsc.org/dalton | Dalton Transactions
Efficient synthesis of tetradecafluoro-4-phenylheptan-4-ol by a
Cannizzaro-type reaction and application of the alcohol as a bulky Martin
ligand variant for a new anti-apicophilic phosphorane†
Xin-Dong Jiang,*a,b Shiro Matsukawa,b,c Ken-ichiro Kakuda,b Yuta Fukuzaki,b Wei-Li Zhao,a Lin-Song Li,a
Huai-Bin Shen,a Satoshi Kojimab and Yohsuke Yamamoto*b
Received 25th May 2010, Accepted 6th August 2010
DOI: 10.1039/c0dt00539h
Alcohols 8 bearing two identical perfluoroalkyl groups were prepared by the reaction of the
corresponding perfluoroalkyl phenyl ketones 7 with 0.5 equivalents of t-BuOK via Cannizzaro-type
disproportionation. Utilizing the new bulky bidentate ligand with two n-C3F7 groups generated from
8c, anti-apicophilic phosphorane 5a and its stable isomer 6a were synthesized. The crystal structures of
5a and 6a were slightly affected by the steric repulsion of heptafluoropropyl groups. Kinetic studies on
the isomerization of 5a to 6a showed that the new ligand was effective for decreasing the isomerization
rate compared with its C2F5 analog 3a to about half.
Anti-apicophilic phosphoranes,7 as we define, are phosphoranes
which have configurations that violate the relative apicophilicity of
Introduction
Hypervalent1 10-P-52 phosphorus compounds (phosphoranes) are
the elements, and are isomeric to and less stable than phosphoranes
regarded as intermediates (or transition states) in the formation
with configurations that comply with apicophilicity. Thus, anti-
or hydrolysis of biologically relevant phosphorus compounds3
apicophilic phosphoranes easily isomerize to their corresponding
such as DNA or RNA. Phosphoranes generally adopt a trigonal-
more stable phosphoranes by BPR (Fig. 1). Therefore, the isolation
bipyramid (TBP) structure which has two distinct types of bonds,
i.e., the apical bond (three-center-four-electron bond) and the
of anti-apicophilic phosphoranes is of great significance for
elucidating the nature of hypervalent compounds in general.
equatorial bond (sp2 bond). This structural characteristic brings
about two unique features, i.e., apicophilicity4,5 and facile stereo-
mutation usually interpreted by the Berry pseudorotation (BPR)
mechanism.6 The former is the propensity for more electronegative
and sterically less bulky groups to prefer the apical sites, and the
latter is a low energy non-dissociative intramolecular site exchange
process peculiar to TBP molecules.
Utilizing the Martin ligand,8 our group succeeded in the isolation
and full characterization of the first anti-apicophilic phospho-
rane, n-butylphosphorane 1b (O-equatorial), which bears an
n-butyl group at the equatorial site (Fig. 1).7,9 The corresponding
equatorial Me analog 1a was also prepared. However, 1a was
found to easily isomerize even at rt, and thus could not be isolated
in a pure form.7 In order to raise the BPR barrier of the anti-
apicophilic phosphoranes, we developed a modified Martin ligand
with two C2F5 groups.10,11 This enabled us to isolate O-equatorial
methylphosphorane 3a as a species thermally stable even at room
temperature.10 A kinetic study revealed that the steric hindrance
of the C2F5 group was much more effective for freezing pseudoro-
aThe Key Laboratory for Special Functional Materials, Ministry of
Education, Henan University, Kaifeng, Henan, 475-004, China. E-mail:
xdjiang@henu.edu.cn; Fax: (+81)-0378-3881358; Tel: (+81)-0378-
3881358
bDepartment of Chemistry, Graduate School of Science, Hiroshima Uni-
versity, 1-3-1 Kagamiyama, Higashi-Hiroshima, 739-8526, Japan. E-mail:
yyama@sci.hiroshima-u.ac.jp; Fax: (+81)-82-424-0723; Tel: (+81)-82-
424-7430
tation than that of the CF3 group (1a → 2a: DGπ = 22.5 kcal
333
mol-1; 3a → 4a: DGπ = 26.1 kcal mol-1).7b,10 The new bidentate
333
cDepartment of Chemistry, Faculty of Science, Toho University 2-2-1
Miyama, Funabashi, 274-8510, Japan
ligand also allowed us to prepare thermally stabilized equatorial
aryl anti-phosphoranes and the first anti-apicophilic arsorane.11a,c
We envisioned that substituting the two C2F5 groups with two
n-C3F7 groups would give rise to anti-apicophilic phosphoranes
with even higher barriers to stereomutation. Herein, we report on
† Electronic supplementary information (ESI) available: Additional data.
CCDC reference numbers 778132 and 778133 for 5a and 6a, respectively.
For ESI and crystallographic data in CIF or other electronic format see
DOI: 10.1039/c0dt00539h
Fig. 1 Bidentate ligand, O-equatorial phosphorane and O-apical phosphorane.
The Royal Society of Chemistry 2010 Dalton Trans., 2010, 39, 9823–9829 | 9823
This journal is
©

View Article Online
Table 1 The reaction of 7a with NaOH
the efficient synthesis of tetradecafluoro-4-phenylheptan-4-ol and
the stereochemical behavior of an anti-apicophilic phosphorane
5a bearing bidentate ligands prepared from this alcohol.
Results and discussion
Entry Base
Solvent 7aa
:
8aa
:
9aa
:
10aa
In order to prepare the new anti-apicophilic phosphorane with the
bulky n-C3F7 groups, tetradecafluoro-4-phenylheptan-4-ol, which
would serve as a precursor to the new bidentate ligand, was
required. The synthesis of such compounds necessitates an efficient
method for introducing the perfluoroalkyl group. The introduction
of a perfluoroalkyl group into an organic molecule can cause a
remarkable change in chemical, physical and biological properties,
due to the lipophilizing nature, strong electron-withdrawing nature
and the steric repulsion induced by the perfluoroalkyl groups.12
Therefore, studies on the development of methods for introducing
such groups have extensively been carried out, and these endeavors
have brought about many practical methods for the introduction
of the CF3 group. For instance, the Ruppert–Prakash reagent13 has
been widely used, and CF3I,14 HCF3,15 XCOCF3(X = OR, NRR¢,
Ar),16 O-silylated vic-amino alcohols,17 and fluoral hemiketal18
have also been utilized as sources of the trifluoromethyl anion.
As for higher congeners, penta- and hepta-fluoroalkyl Grignard
reagents (C2F5MgBr and n-C3F7MgBr)19 and penta- and hepta-
fluoroalkyl lithium (C2F5Li and n-C3F7Li)20,21 are known. How-
ever, the precursor perfluoroalkyl bromides and iodides are of low
boiling point and handling is not necessarily simple. Langlois’s
method using easy-to-handle trifluoroacetophenone as a source
of the CF3 anion was originally intended for reactions with other
ketones.16c In a preliminary examination using its higher congener,
pentafluoroethyl phenyl ketone, we found that this compound
could serve as a source of the C2F5 anion, and interestingly, by
using only 0.5 equivalents of t-BuOK as base in the absence of
an additional ketone, the C2F5 anion reacted with the unreacted
starting material ketone to efficiently furnish alcohols with two
C2F5 groups by Cannizzaro-type disproportionation.22 Thus, we
decided to examine this reaction in a little more detail and then
attempt to apply this method for the preparation of the alcohol
with two n-C3F7 groups.
1
2
3
4
NaOH aq.
NaOH (solid) DMF
NaOH aq.
NaOH (solid) THF
DMF
41.7
:
:
:
:
0
16.3
0
:
:
:
:
57.1
41.2
45.9
86.1
:
:
:
:
1.2
1.8
1.5
1.1
40.7
52.6
12.8
THF
0
a Based on the integral values in the 19F NMR.
Scheme 1 Haloform reaction of 7a.
NaBH4. However, when solid NaOH was used in DMF, 8a was
obtained, although in a low yield of 16% (entry 2). Although
this result is very promising, we could not improve the yields.
Thus, the use of t-BuOK as a base under anhydrous conditions is
optimal for our Cannizzaro-type reaction to obtain alcohols with
two perfluoroalkyl groups.
DMF has been a popularly used solvent for the generation of
the trifluoromethyl anion.14,15a,16c Therefore, its use for substrates
7a, 7b and 7c in the Cannizzaro-type reaction was investigated.
The reaction of 0.5 equivalents of t-BuOK with 1.0 equivalent of
ketones 7 provided alcohols 8 (8a, 8b and 8c) with high efficiency
(Scheme 2). The reaction of 7a proceeded to completion (entry 1
in Table 2), and alcohol 8a (41%) and ester 12 (39%) were obtained
in good yields. However, the yield of 8b from 7b was 22% (entry
2), and a large amount of 7c was recovered in the case of the
n-C3F7 analog (entry 3). As an alternative solvent, THF was also
examined. Since the isolated yields of 8 (8a, 8b and 8c) were similar
The typical Cannizzaro reaction involves the base-induced
disproportionation of non-enolizable aldehydes to mixtures of
alcohols and carboxylic acids. Generally, the Cannizzaro reaction
is performed using strong alkali in aqueous or alcoholic solutions.
If our disproportionation reaction could be carried out with
a hydroxide in the place of an alkoxide, then the workup
would be more facile. Therefore, we decided to examine sodium
hydroxide as a base for our version of the Cannizzaro reaction.
Trifluoroacetophenone 7a was treated with NaOH (0.5 eq.) for
10 h at room temperature, and quenched with the addition of
2 M HCl aq (entries 1–4 in Table 1). Under aqueous conditions,
8a was not obtained (entries 1 and 3), and the main product of the
reactions was trifluoroacetophenone hydrate 9a.23 It is well known
that 7a gradually undergoes the haloform reaction to give benzoate
in the presence of excess hydroxide anion (Scheme 1).24 However,
benzoic acid was not obtained in our experiments. This is probably
because intermediate 11a is stable under aqueous conditions and
the reaction is so slow. A small amount of reduced compound
10a25 was also obtained (1–2%). This was identified by comparison
with an authentic sample prepared from the reaction of 7a with
Scheme 2 Synthesis of alcohols 8.
Table 2 Solvent effect on the Cannizzaro-type reaction
Entry Substrate Solvent
7
:
8
:
12
1
2
3
4
5
6
7a
7b
7c
7a
7b
7c
DMF
DMF
DMF
THF
THF
THF
0
0
1.51
0
0
:
:
:
:
:
:
1a (41%)b
1 (22%)
1 (5%)
1 (33%)
1 (33%)
1 (27%)
:
:
:
:
:
:
0.90 (39%)
1.62 (50%)
0.93
1.50 (50%)
1.21
0.50
1.20
a Based on the integral values in the 1H NMR. b The isolated yield.
9824 | Dalton Trans., 2010, 39, 9823–9829
This journal is
The Royal Society of Chemistry 2010
©

View Article Online
Scheme 3 Generation of the new bulky bidentate ligand and synthesis of O-equatorial phosphorane 5a and O-apical phosphorane 6a.
Fig. 2 The ORTEP drawings of 5a and 6a showing the thermal ellipsoids at the 30% probability level. The hydrogen atoms are omitted for clarity.
with those of reactions in DMF, and the experimental procedure
for isolating the products (entries 4–6) was easier with THF, THF
was more preferable as the solvent. Monitoring 19F NMR (see
ESI,†) in the reaction of 7b to 8b revealed that the reaction is
complete in about 15 h at room temperature. tert-Butyl benzoate
12, the side product, could be removed by azeotropic treatment
or in large-scale syntheses of 8 by conversion to benzoic acid by
treatment with trifluoroacetic acid. To the best of our knowledge,
this is the first example for the introduction of a n-C3F7 group into
7 to form 8 with two n-C3F7 groups based on a Cannizzaro-type
disproportionation reaction.
Using our recently reported method for the synthesis of
phosphorane 3a bearing the C2F5 groups,10 the corresponding
phosphorane 5a bearing the two n-C3F7 groups was prepared
as outlined in Scheme 3. Alcohol 8c was converted to its o-
bromobenzene derivative 13. This was treated with NaH followed
by n-BuLi to generate a bulky dianionic bidentate ligand which
was reacted with PCl3. Quenching the reaction with aqueous HCl
gave phosphorane 14. The low efficiency compared with the C2F5
system is probably due to the increased steric hindrance induced
by the C3F7 groups. Treatment of 14 with MeLi followed by
oxidation with I2 at -78 ◦C gave anti-apicophilic phosphorane
5a in high yield as the exclusive product. Heating a solution of
O-equatorial phosphorane 5a furnished O-apical phosphorane
6a, quantitatively. The structures of 5a and 6a were confirmed
by X-ray analysis (Fig. 2), which shows that both have slightly
distorted TBP geometry. A comparison of the structures of n-
C3F7 derivatives 5a and 6a with those of the corresponding C2F5
derivatives 3a10 and 4a10 indicates that the directions in which
the zigzagged perfluoroalkyls are stretched are practically the
same. This allows for a direct comparison of structural parameters
between corresponding compounds (3a and 5a; 4a and 6a), and
it can be suggested that the steric bulk of the n-C3F7 group has
slightly affected the crystal structures (Table 3). In the O-equatorial
phosphoranes 3a and 5a, the C1–P1–O2 angle of 5a (121.61◦) is
expanded by 2.1◦ compared to that of 3a (119.52◦), and the C1–
P1–C3 angle of 5a (119.17◦) is narrowed by 2.1◦ compared to
that of 3a (121.27◦) in the projected equatorial plane. This can
be inferred to steric repulsion between the two n-C3F7 groups of
differing ligands of 5a that face each other.10 Other structural
parameters obtained for 3a and 5a around the phosphorus atom
were very similar. In the O-apical phosphoranes 4a and 6a, the
bond lengths were almost the same, but the angles were rather
different. The apical bond O1–P1–O2 in 6a has an angle of 174.44◦
and is less distorted from the ideal value of 180◦ than that of 4a
which is 169.32◦. In accordance, the differences in the bond angles
formed between apical bonds and equatorial bonds in 4a and 6a
were 2–4◦. The C1–P1–C2, C2–P1–C3, and C3–P1–C1 angles in
the equatorial plane were 128.30, 115.85, and 115.85◦ for 6a, and
137.10, 111.45, and 111.45◦ for 4a.
This journal is
The Royal Society of Chemistry 2010
Dalton Trans., 2010, 39, 9823–9829 | 9825
©

View Article Online
◦
Table 3 Selected bond lengths (A) and angles ( ) for 5a, 6a, 3a10 and 4a10
˚
activation free energy for the stereomutation of 5a to 6a was higher
than that of 3a to 4a (DGπ333 = 26.1 kcal mol-1)10 by 0.4 kcal mol-1.
On the other hand, enhancement of the barrier upon changing
Compound
5a
6a
3a
4a
from the CF3 system (1a → 2a: DGπ = 22.5 kcal mol-1)7b to the
333
P1–O1
P1–O2
P1–C1
P1–C2
P1–C3
1.7847(14)
1.6620(14)
1.822(2)
1.8750(19)
1.819(2)
1.7588(14)
1.7588(14)
1.8250(19)
1.8250(19)
1.808(4)
1.7858(17)
1.6547(17)
1.827(2)
1.879(2)
1.814(3)
1.7588(12)
1.7588(12)
1.8320(17)
1.8320(17)
1.810(3)
C2F5 system was 3.6 kcal mol-1. Therefore, the change from C2F5
to n-C3F7 group was not as dramatic as that for the change from
CF3 to C2F5.
O1–P1–O2
O1–P1–C1
O1–P1–C2
O1–P1–C3
O2–P1–C1
O2–P1–C2
O2–P1–C3
C1–P1–C2
C1–P1–C3
C2–P1–C3
83.26(6)
86.73(8)
171.20(8)
89.00(8)
121.61(8)
87.97(8)
117.99(9)
98.64(9)
119.17(10)
94.64(9)
174.44(10)
86.99(7)
90.59(8)
92.78(5)
90.59(8)
86.99(7)
92.78(5)
128.30(13)
115.85(6)
115.85(6)
83.89(8)
86.38(9)
169.32(9)
89.29(7)
86.80(7)
95.34(5)
86.80(7)
89.29(7)
95.34(5)
137.10(12)
111.45(6)
111.45(6)
Conclusions
171.58(10)
88.55(11)
119.52(10)
87.92(9)
117.97(11)
99.42(11)
121.27(12)
93.57(12)
The synthesis of alcohols 8 (8a, 8b and 8c) with two perfluoroalkyl
(CF3, C2F5, n-C3F7) groups was achieved in an efficient fashion
by the reaction of perfluoroalkyl phenyl ketones 7a–c with
0.5 equivalents of t-BuOK in THF based on a Cannizzaro-type
reaction. Utilizing the new bulky bidentate ligand system with
two n-C3F7 groups, anti-apicophilic phosphorane 5a could be
synthesized, quantitatively from its precursor P–H (equatorial)
phosphorane 14. This anti-apicophilic phosphorane isomerized
to its more stable isomer 6a upon heating. Both compounds were
characterized by X-ray structural analysis. A kinetic study of
the isomerization of 5a to 6a, revealed that the n-C3F7 group
was effective for raising the BPR barrier compared with its
corresponding anti-apicophilic phosphorane bearing C2F5 groups.
Although the effect was not as significant as that upon changing
from CF3 to C2F5, we were able to prove that increasing steric
hindrance is a reasonable way to raise the isomerization barrier.
This provides valuable insight for future designing of new ligands.
Table 4 Rate constants for the stereomutation from O-equatorial phos-
phoranes (5a, 3a10) to O-apical phosphoranes (6a, 4a10)
T/K
ka(5a→6a)/s-1
ka(3a→4a)/s-1
333
338
343
348
353
(2.24 0.03) ¥ 10-5
(4.22 0.08) ¥ 10-5
(7.17 0.19) ¥ 10-5
(1.17 0.02) ¥ 10-4
(2.01 0.03) ¥ 10-4
(4.76 0.03) ¥ 10-5
(7.70 0.06) ¥ 10-5
(15.0 0.18) ¥ 10-5
a Error is given as the standard deviation.
Experimental
The rate of isomerization of 5a to 6a was measured in C6D6 in
the temperature range of 333–353 K by monitoring the change
in the integrals of the 1H NMR signals of the methyl group. The
isomerization proceeded with first-order kinetics with rate values
given in Table 4. A comparison of these rates with those of the
C2F5 analog 3a at the same temperature show that there is about
a two-fold decrease in isomerization rates. Thus, it could be said
that the steric effect of the new anti-apicophilic phosphoranes has
an unnegligible effect. The activation parameters obtained from
the Eyring plot are as follows: DSπ = (-6.03 1.37) e.u., DHπ =
(24.5 0.5) kcal mol-1, DGπ333 = 26.5 kcal mol-1 (Fig. 3). Thus, the
General
Melting points were measured using a Yanaco micro melting point
apparatus and are uncorrected. H NMR (400 MHz), 19F NMR
1
(376 MHz), and 31P NMR (162 MHz) were recorded using a JEOL
EX-400 or a JEOL AL-400 spectrometer. 1H NMR chemical shifts
(d) are given in ppm downfield from Me4Si, determined by residual
chloroform (d 7.26) or incompletely deuterated benzene (d 7.20).
19F NMR chemical shifts (d) are given in ppm downfield from
external CFCl3. 31P NMR chemical shifts (d) are given in ppm
downfield from external 85% H3PO4. The elemental analyses were
performed using a Perkin-Elmer 2400 CHN elemental analyzer.
All reactions were carried out under N2 or Ar. Tetrahydrofuran
(THF) and diethyl ether (Et2O) were freshly distilled from Na-
benzophenone, n-hexane was distilled over Na, and other solvents
were distilled over CaH2. Merck silica gel 60 was used for the
column chromatography.
1,1,1,3,3,3-Hexafluoro-2-phenylpropan-2-ol (8a). Under N2, t-
BuOK (1.0 M THF solution, 1.25 mL, 1.25 mmol) was added to
a solution of trifluoroacetophenone 7a (435 mg, 2.50 mmol) in
THF (5 mL) at 0 ◦C and the resulting mixture was stirred for 15 h
at room temperature. The mixture was extracted with Et2O (2 ¥
10 mL), and the organic layer was washed with brine (2 ¥ 15 mL)
and dried over anhydrous MgSO4. After removing the solvents by
evaporation, the resulting crude mixture was separated by TLC
(n-hexane : CH2Cl2 = 2 : 1) to afford 8a (201 mg, 0.823 mmol, 33%)
1
and 12 (112 mg, 0.625 mmol, 50%) as colorless liquids. 8a: H
NMR (400 MHz, CDCl3): d 3.47 (br s, 1 H, OH), 7.43–7.49 (m,
Fig. 3 Eyring plot for the isomerization of 5a to 6a.
9826 | Dalton Trans., 2010, 39, 9823–9829
3 H, Ar–H), 7.73 (d, 3JH,H = 8.0 Hz, 2 H, Ar–H) ppm. 19F NMR
This journal is
The Royal Society of Chemistry 2010
©

View Article Online
1
(376 MHz, CDCl3): d -76.0 (s, 6 F, CF3) ppm. 12: H NMR
layer was washed with brine (2 ¥ 40 mL) and dried over anhydrous
MgSO4. After removing the solvents by evaporation, the yellow
oil was subjected to distillation to affor◦d 8c (0.656 g, 1.52 mmol,
27%) as a colorless liquid. Bp 64.0–65.0 C (3.0 mmHg). 1H NMR
(400 MHz, CDCl3): d 3.67 (br s, 1 H, OH), 7.42–7.48 (m, 3
3
(400 MHz, CDCl3): d 1.15 (s, 9 H, C(CH3)3), 7.41 (t, JH,H
=
8.0 Hz, 2 H, Ar–H), 7.52 (t, 3JH,H = 8.0 Hz, 1 H, Ar–H), 7.99 (d,
3JH,H = 8.0 Hz, 2 H, Ar–H) ppm.
2,2,2-Trifluoro-1-phenylethane-1,1-diol (9a). In the open air,
NaOH (54.8 mg, 1.37 mmol) in H2O (2 mL) was added to a
solution of 7a (476 mg, 2.74 mmol) in THF (5 mL) at 0 C and
3
H, Ar–H), 7.74 (d, JH,H = 8.0 Hz, 2 H Ar–H) ppm. 19F NMR
(376 MHz, CDCl3): d -81.2 (m, 6 F, CF2CF2CF3), -116.1 (br s,
4 F, CF2CF2CF3), -121.3 (d, 2JF,F = 292.0 Hz, 2 F, CF2CF2CF3),
-124.3 (d, 2JF,F = 292.0 Hz, 2 F, CF2CF2CF3) ppm.
◦
the mixture was stirred for 10 h at room temperature. The reaction
was then quenched with 2 M HCl (15 mL). The mixture was
extracted with Et2O (2 ¥ 20 mL), and the combined organic layer
was washed with brine (2 ¥ 15 mL) and dried over anhydrous
MgSO4. After removing the solvents by evaporation, the crude
mixture (428 mg) of 9a, 10a and the starting material 7a was
obtained (9a : 10a : 7a = 86.1 : 1.1 : 12.7 based on 19F NMR). 9a:
1H NMR (400 MHz, CDCl3): d 4.32 (s, 2 H, OH), 7.40–7.44 (m,
3 H, Ar–H), 7.70–7.72 (m, 2 H, Ar–H) ppm. 19F NMR (376 MHz,
CDCl3): d -85.0 (s, 3 F, CF3) ppm. MS (EI(+)): m/z = 192 [M]+,
193 [M + 1]+, 123 [M - CF3]+.
4-(2-Bromophenyl)-1,1,1,2,2,3,3,5,5,6,6,7,7,7-tetradecafluoro-
heptan-4-ol (13). Under N2, TMEDA (8.00 mL, 53.0 mmol) was
added to n-BuLi (1.60 M n-hexane solution, 34.0 mL, 54.4 mmol)
at room temperature, and the mixture was stirred for 30 min. 8c
(7.97 g, 17.9 mmol) was then added at 0 ◦C, and the mixture
was stirred for 39 h at room temperature. 1,2-Dibromo-1,1,2,2-
tetrafluoroethane (9.6 mL, 80.1 mmol) was added at -78 ◦C and
the resulting mixture was stirred for 4 h at room temperature. The
reaction was quenched with 2 M HCl (80 mL) at 0 ◦C. The mixture
was extracted with Et2O (2 ¥ 100 mL), and the organic layer was
washed with brine (2 ¥ 60 mL) and dried over anhydrous MgSO4.
After removing the solvents by evaporation, the resulting yellow
oil was separated by column chromatography (n-hexane : CH2Cl2 =
5 : 1), followed by distillation to afford 13 (3.54 g, 6.78 mmol, 38%)
2,2,2-Trifluoro-1-phenylethanol (10a). Under N2, NaBH4
(30.0 mg, 0.793 mmol) was adde◦d to a solution of 7a (295 mg,
1.69 mmol) in THF (5 mL) at 0 C and the mixture was stirred
for 15 h at room temperature. The mixture was extracted with
Et2O (2 ¥ 30 mL), and the combined organic layer was washed
with brine (2 ¥ 20 mL) and dried over anhydrous MgSO4. After
removing the solvents by evaporation, the crude mixture (255 mg)
of 10a and the starting material 7a was obtained (10a : 7a = 73 : 27
based on 19F NMR). 10a: 1H NMR (400 MHz, CDCl3): d 3.19 (s,
1 H, C(OH)H), 5.00 (q, 3JH,F = 6.8 Hz, 1 H, C(OH)H), 7.40–7.44
(m, 5 H, Ar–H) ppm. 19F NMR (376 MHz, CDCl3): d -78.8 (d,
3JH,F = 6.8 Hz, 3 F, CF3) ppm.
◦
1
as a colorless liquid. Bp 58.0–59.0 C (0.18 mmHg). H NMR
3
(400 MHz, CDCl3): d 5.73 (s, 1 H, OH), 7.34 (t, JH,H = 8.0 Hz,
1 H, Ar–H), 7.42 (t, 3JH,H = 8.0 Hz, 1 H, Ar–H), 7.69 (d, 3JH,H
=
F
8.0 Hz, 1 H, Ar–H), 7.78 (br d, 3JH,H = 8.0 Hz, 1 H, Ar–H) ppm. 19
NMR (376 MHz CDCl3): d -81.3 (m, 6 F, CF2CF2CF3), -112.2
(d, 2JF,F = 292.0 Hz, 2 F, CF2CF2CF3), -114.2 (d, 2JF,F = 292.0 Hz,
2 F, CF2CF2CF3), -121.3 (br d, 2JF,F = 292.0 Hz, 2 F, CF2CF2CF3),
-123.8 (br d, 2JF,F = 292.0 Hz, 2 F, CF2CF2CF3) ppm.
2,2,3,3,4,4,4-Heptafluoro-1-phenylbutan-1-one
(7c). Under
[TBPY-5-11]-1-Hydro-3,3,3¢,3¢-tetrakis(heptafluoropropyl)-1,1¢-
spirobi[3H,2,1,k5-benzoxaphosphole] (14). Under N2, a solution
of 13 (954 mg, 1.82 mmol) in THF (8 mL) was added to a
suspension of NaH (145 mg, 3.62 mmol) in THF (4 mL) at
0 ◦C, and the mixture was stirred for ◦0.5 h at room temperature.
The mixture was then cooled to -78 C, and n-BuLi (in 1.60 M
n-hexane, 1.2 mL, 1.92 mmol) was added, and the resulting
mixture was stirred for 1 h at the same temperature. After that,
the mixture was transferred to a solution of PCl3 (0.080 mL,
0.91 mmol) in THF (15 mL) at -78 ◦C. The mixture was warmed
to room temperature and stirred for 6 h. The reaction was
quenched with 6 M HCl (20 mL) at 0 ◦C. The mixture was
extracted with ether (2 ¥ 40 mL), and the organic layer was
washed with brine (2 ¥ 30 mL) and dried over anhydrous MgSO4.
After removing the solvents by evaporation, the resulting crude
mixture was separated by column chromatography (n-hexane),
followed by reversed-phase HPLC (MeCN) to afford a white
solid of 14 (RT = 8.7 min: 102.4 mg, 0.111 mmol, 12%). Mp
N2, PhLi (1.07 M cyclohexane/Et2O solution, 60 mL, 64.2 mmol)
was added to a solution of ethyl heptafluorobutyrate (12.9 g,
53.0 mmol) in THF (300 mL) at -78 ◦C, and the mixture was
stirred for 2 h at the same temperature. The reaction was then
treated with HCl (2 M, 50 mL) at -78 ◦C and the resulting
mixture was stirred for 1 h at room temperature. The mixture was
extracted with Et2O (2 ¥ 100 mL), and the combined organic layer
was washed with brine (2 ¥ 80 mL) and dried over anhydrous
MgSO4. After removing the solvents by evaporation, the yellow
oil was subjected to distillation to afford 7c (12.3 g, 45.0 mmol,
◦
1
85%) as a colorless liquid. Bp 78.0–78.8 C (26.5 mmHg). H
NMR (400 MHz, CDCl3): d 7.55 (t, 3JH,H = 8 Hz, 2 H, Ar–H), 7.71
(t, 3JH,H = 8.0 Hz, 1 H, Ar–H), 8.07 (d, 3JH,H = 8.0 Hz, 2 H, Ar–H)
ppm. 19F NMR (376 MHz, CDCl3): d -80.6 (t, 3JF,F = 8.6 Hz, 3 F,
CF2CF2CF3), -113.9 (q, 3JF,F = 8.6 Hz, 2 F, CF2CF2CF3), -125.9
(m, 2 F, CF2CF2CF3) ppm.
1,1,1,2,2,3,3,5,5,6,6,7,7,7-Tetradecafluoro-4-phenylheptan-4-ol
(8c). Under N2, t-BuOK (1.0 M THF solution, 5.5 mL,
5.5 mmol) was added to a solution of 7c (3.01 g, 11.0 mmol)
in THF (50 mL) at 0 ◦C and the resulting mixture was stirred
for 24 h at room temperature. After the solvents were removed
by evaporation, CH2Cl2 (30 mL) was added. Trifluoroacetic acid
(15.0 mL, 202 mmol) was then added to the mixture at 0 ◦C, and the
mixture was stirred for 20 h at room temperature. The reaction was
quenched with saturated aqueous Na2CO3 (100 mL). The mixture
was extracted with Et2O (2 ¥ 50 mL), and the combined organic
◦
1
103.0–104.0 C. H NMR (400 MHz, CDCl3): d 7.67–7.76 (m,
1
4 H, Ar–H), 7.82 (s, 2 H, Ar–H), 7.98 (d, JH,P = 708 Hz, 1 H,
P–H), 8.34–8.38 (m, 2 H, Ar–H) ppm. 19F NMR (376 MHz,
3
CDCl3): d -80.9 (t, JF,F = 13.5 Hz, 6 F, CF2CF2CF3), -81.4
3
4
(dd, JF,F = 13.5 Hz, JF,F = 9.7 Hz, 6 F, CF2CF2CF3), -112.4 (d,
2JF,F = 296 Hz, 2 F, CF2CF2CF3), -112.9 (br d, JF,F = 296 Hz, 2
2
2
F, CF2CF2CF3), -115.3 (br d, JF,F = 296 Hz, 2 F, CF2CF2CF3),
-115.7 (d, 2JF,F = 296 Hz, 2 F, CF2CF2CF3), -119.4 (br d, 2JF,F
=
296 Hz, 2 F, CF2CF2CF3), -125.0 (s, 4 F, CF2CF2CF3), -125.7 (br
This journal is
The Royal Society of Chemistry 2010
Dalton Trans., 2010, 39, 9823–9829 | 9827
©

View Article Online
2
d, JF,F = 296 Hz, 2 F, CF2CF2CF3) ppm. 31P NMR (162 MHz,
were processed using SCALEPACK. The structures were solved
by a direct method with the SHELX-97 program.27 Refinement
on F2 was carried out using the full-matrix least-squares by
the SHELX-97 program.27 All non-hydrogen atoms were refined
using the anisotropic thermal parameters. The hydrogen atoms
were included in the refinement along with the isotropic thermal
parameters.
CDCl3): d -46.3 ppm.
[TBPY-5-12]-1-Methyl-3,3,3¢,3¢-tetrakis(heptafluoropropyl)-1,1¢-
spirobi[3H,2,1,k5-benzoxaphosphole] (5a). Under Ar, to
a
solution of 14 (45.5 mg, 0.0496 mmol) in Et2O (3 mL) was added
MeLi (1.04 M diethyl ether solution, 0.200 mL, 0.208 mmol)
at -78 ◦C. The mixture was then stirred for 2 h at room
temperature. I2 (53 mg, 0.207 mmol) was added to the mixture
Crystal data for 5a. C27H11F28O2P, M = 930.33, triclinic, space
◦
˚
◦
˚
˚
3
¯
group P1,◦a = 9.4620(2) A, b = 10.5790(2) A, c = 15.9370(7) A, a =
at -78 C and the resulting solution was stirred for 1 h at room
◦
˚
83.813(1) , b = 89.440(1) , g = 84.867(1) , V = 1579.62(5) A , T =
173(2) K, Z = 2, Data/restraints/parameters = 6994/0/524, R1 =
0.0471 (I > 2s(I)), wR2 (all data) = 0.1635, GOF = 1.087.
temperature. The reaction was quenched with aqueous Na2S2O3
(20 mL). The mixture was extracted with Et2O (2 ¥ 60 mL),
and the organic layer was washed with brine (2 ¥ 50 mL) and
dried over anhydrous MgSO4. After removing the solvents by
evaporation, the resulting crude mixture was separated by column
chromatography (n-hexane : CH2Cl2 = 5 : 1) to afford a white
solid of 5a (45.3 mg, 0.0486 mmol, 98%). Colorless crystals of
5a suitable for X-ray analysis were obtai◦ned by recrystallization
from CH2Cl2–n-hexane. Mp 100.0–101.0 C (decomp.). 1H NMR
(400 MHz, C6D6): d 1.91 (d, 3JH,P = 12 Hz, 3 H, CH3), 6.93–7.02
(m, 4 H, Ar–H), 7.15–7.23 (m, 2 H, Ar–H), 7.53 (br s, 2 H, Ar–H)
ppm. 19F NMR (376 MHz, C6D6): d -80.8 (br s, 6 F, CF2CF2CF3),
Crystal data for 6a. C27H11F28O2P, M = 930.33, monoclinic,
˚
˚
space group C2/c, a = 23.7910(4) A, b◦= 11.5480(2) A, c =
◦
3
˚
˚
11.9090(7) A, a = g = 90 , b = 99.800(1) , V = 3224.12(9) A ,
T = 200(2) K, Z = 4, Data/restraints/parameters = 3848/0/260,
R1 = 0.0535 (I > 2s(I)), wR2 (all data) = 0.1704, GOF = 1.158.
Kinetic measurements of the isomerization of 5a to 6a
Samples (ª 8 mg) of 5a dissolved in C6D6 (0.6 mL) were sealed in an
NMR tube under N2. Kinetic measurements of the pseudorotation
process were carried out on a JEOL EX-400 spectrometer by
monitoring 1H NMR signals in a variable temperature mode, and
the specified temperatures were maintained throughout each set
of measurements (error within 1 ◦C). The observed temperatures
2
-81.3 (s, 6 F, CF2CF2CF3), -110.3 (br d, JF,F = 298 Hz, 4 F,
2
CF2CF2CF3), -114.5 (br d, JF,F = 298 Hz, 4 F, CF2CF2CF3),
-122.9 (br d, 2JF,F = 298 Hz, 4 F, CF2CF2CF3), -126.1 (br d, 2JF,F
=
298 Hz, 4 F, CF2CF2CF3) ppm. 31P NMR (162 MHz, C6D6): d
-4.5 ppm. Found: C, 34.80; H, 1.13. Calc. for C23H11F20O2P: C,
34.86; H, 1.19%.
1
were calibrated with the H NMR chemical shift difference in
signals of neat 1,3-propanediol (high temperature region) and
MeOH (low temperature region). The data were analyzed based
on first-order kinetics using the equation of ln (C0/C5a) = kT,
in which C0 = ratio of 5a at t = 0, C5a = ratio of 5a at arbitrary
intervals. Here C0 = C5a + C6a, C0/C5a = (C5a + C6a)/C5a = 1 +
1/(C5a/C6a). The ratio C5a/C6a was determined by the integration
[TBPY-5-11]-1-Methyl-3,3,3¢,3¢-tetrakis(heptafluoropropyl)-1,1¢-
spirobi[3H,2,1,k5-benzoxaphosphole] (6a). A C6D6 (0.8 mL)
solution of 5a (21.0 mg, 0.0225 mmol) was heated at 100 ◦C
for 8 h. After concentration in vacuo, a white solid of 6a was
obtained (19.8 mg, 0.212 mmol, 94%). Colorless crystals of 6a
suitable for X-ray analysis were obtained by recrystallization from
CH2Cl2–n-hexane. Mp 110.0–110.8 ◦C. 1H NMR (400 MHz,
1
of H NMR signals of the methyl group at 60, 65, 70, 75, and
◦
80 C. Rate constants for the stereomutation from O-equatorial
2
3
C6D6): d 1.74 (d, JH,P = 16 Hz, 3 H, CH3), 7.04 (t, JH,H
=
phosphorane 5a to O-apical phosphorane 6a are shown in Table 4.
3
7.6 Hz, 2 H, Ar–H), 7.16 (t, JH,H = 7.6 Hz, 2 H, Ar–H), 7.50
(br s, 2 H, Ar–H), 8.52–8.58 (m, 2 H, Ar–H) ppm. 19F NMR
3
Acknowledgements
(376 MHz, C6D6): d -81.2 (t, JF,F = 12.5 Hz, 6 F, CF2CF2CF3),
3
4
-81.6 (dd, JF,F = 12.5 Hz, JF,F = 9.8 Hz, 6 F, CF2CF2CF3),
This research was supported by a Grant-in-Aid for Scientific
Research on Priority Areas (No. 17350021) from the Ministry
of Education, Culture, Sports, Science and Technology, Japan.
2
2
-111.2 (d, JF,F = 294 Hz, 2 F, CF2CF2CF3), -112.2 (dm, JF,F
294 Hz, 2 F, CF2CF2CF3), -113.6 (dm, JF,F = 294 Hz, 2 F,
=
2
2
CF2CF2CF3), -114.6 (dm, JF,F = 294 Hz, 2 F, CF2CF2CF3),
-118.7 (dm, 2JF,F = 294 Hz, 2 F, CF2CF2CF3), -123.6 (dm, 2JF,F
=
2
References
294 Hz, 2 F, CF2CF2CF3), -125.5 (dm, JF,F = 294 Hz, 2 F,
CF2CF2CF3), -126.4 (dm, JF,F = 294 Hz, 2 F, CF2CF2CF3); 31P
2
1 (a) K.-y. Akiba, Chemistry of Hypervalent Compounds, Wiley-VCH,
New York, 1999; (b) R. R. Holmes, Pentacoordinated Phosphorus -
Structure and Spectroscopy, ACS Monographs 175, 176, vol, I, II;
American Chemical Society, Washington, DC, 1980; (c) D. E. C.
Corbridge, Phosphorus: An Outline of Its Chemistry, Biochemistry, and
Technology, Elsevier, Amsterdam, 4th edn, 1990, ch. 14, pp. 1233–1256;
(d) R. Burgada, and R. Setton, in The Chemistry of Organophosphorus
Compounds, ed. F. R. Hartley, Wiley-Interscience, Chichester, UK,
1994, vol. 3, pp. 185–277.
NMR (162 MHz, C6D6): d -20.1 ppm. Found: C, 34.58; H, 1.05.
Calc. for C23H11F20O2P: C, 34.86; H, 1.19%.
X-Ray single crystal diffraction data X-ray of 5a and 6a†
Crystals suitable for the X-ray structural determination were
mounted on a Mac Science DIP2030 imaging plate diffractometer
and irradiated with graphite monochromated Mo-Ka radiation
2 For the N-X-L designation, see: C. W. Perkins, J. C. Martin, A. J.
Arduengo, W. Lau, A. Alegria and J. K. Kochi, J. Am. Chem. Soc.,
1980, 102, 7753–7759.
˚
(l = 0.71073 A) for the data collection. The unit cell parameters
3 (a) A. C. Hengge, Acc. Chem. Res., 2002, 35, 105–112 and references
therein; (b) S. D. Lahiri, G. Zhang, D. Dunaway-Mariano and K. N.
Allen, Science, 2003, 299, 2067–2071; (c) R. R. Holmes, Acc. Chem.
Res., 2004, 37, 746–753; (d) F. H. Westheimer, Acc. Chem. Res., 1968, 1,
70–78; (e) G. R. J. Thatcher and R. Kluger, Adv. Phys. Org. Chem., 1989,
were determined by separately autoindexing several images in
each data set using the DENZO program (MAC Science).26 For
each data set, the rotation images were collected in 3 degree
increments with a total rotation of 180◦ about the f axis. The data
9828 | Dalton Trans., 2010, 39, 9823–9829
This journal is
The Royal Society of Chemistry 2010
©

View Article Online
25, 99–265; (f) for recent mechanistic studies on phosphoryltransfer
reaction, see: C. S. Lo´pez, O. N. Faza, A. R. de Lera and D. M.
York, Chem.–Eur. J., 2005, 11, 2081–2093 and references therein; (g) T.
Uchimaru, M. Uebayasi, T. Hirose, S. Tsuzuki, A. Yliniemela¨, K.
Tanabe and K. Taira, J. Org. Chem., 1996, 61, 1599–1608.
S. Kojima, Y. Yamamoto, K.-y. Akiba, S. Re and S. Nagase, Inorg.
Chem., 2006, 45, 7269–7277; (g) S. Kojima, M. Nakamoto and K.-y.
Akiba, Eur. J. Org. Chem., 2008, 1715–1722.
10 X.-D. Jiang, K.-i. Kakuda, S. Matsukawa, H. Yamamichi, S. Kojima
and Y. Yamamoto, Chem.–Asian J., 2007, 2, 314–323.
4 (a) M. Nakamoto, S. Kojima, S. Matsukawa, Y. Yamamoto and
K.-y. Akiba, J. Organomet. Chem., 2002, 643–644, 441–452; (b) S.
Matsukawa, K. Kajiyama, S. Kojima, S.-y. Furuta, Y. Yamamoto
and K.-y. Akiba, Angew. Chem., Int. Ed., 2002, 41, 4718–4722; (c) S.
Trippett, Phosphorus Sulfur Relat. Elem., 1976, 1, 89–98; (d) S. Trippett,
Pure Appl. Chem., 1974, 40, 595–604; (e) G. Buono and J. R. Llinas, J.
Am. Chem. Soc., 1981, 103, 4532–4540; (f) M. Eisenhut, H. L. Mitchell,
D. D. Traficante, R. J. Kaufman, J. M. Deutch and G. M. Whitesides,
J. Am. Chem. Soc., 1974, 96, 5385–5397; (g) C. G. Moreland, G. O.
Doak, L. B. Littlefield, N. S. Walker, J. W. Gilje, R. W. Braun and A. H.
Cowley, J. Am. Chem. Soc., 1976, 98, 2161–2165; (h) L. V. Griend and
R. G. Cavell, Inorg. Chem., 1983, 22, 1817–1820; (i) S. Kumaraswamy,
C. Muthiah and K. C. Kumara Swamy, J. Am. Chem. Soc., 2000, 122,
964–965; (j) P. Kommana, S. Kumaraswamy, J. J. Vittal and K. C.
Kumara Swamy, Inorg. Chem., 2002, 41, 2356–2363; (k) P. Kommana,
N. S. Kumar, J. J. Vittal, E. G. Jayasree, E. D. Jemmis and K. C. Kumara
Swamy, Org. Lett., 2004, 6, 145–148.
11 (a) X.-D. Jiang, S. Matsukawa and Y. Yamamoto, Dalton Trans.,
2008, 3678–3687; (b) X.-D. Jiang, S. Matsukawa, H. Yamamichi and
Y. Yamamoto, Heterocycles, 2007, 73, 805–824; (c) X.-D. Jiang, S.
Matsukawa, H. Yamamichi and Y. Yamamoto, Inorg. Chem., 2007, 46,
5480–5482; (d) X.-D. Jiang and Y. Yamamoto, J. Organomet. Chem.,
2010, 695, 740–746.
12 (a) Organofluorine Chemistry: Principles and Commercial Applications,
R. E. Banks, B. E. Smart and J. C. Tatlow Eds, Plenum: New York,
1994; (b) J. T. Welch and S. Eswaraksrishnan, Fluorine in Bioorganic
Chemistry, Wiley: New York, 1991; (c) D. Cartwright, Recent De-
velopments in Fluorine-Containing Agrochemicals. In Organofluorine
Chemistry: Principles and Commercial Applications, R. E. Banks, B.
E. Smart and J. C. Tatlow Eds,. Plenum: New York, 1994; (d) B. E.
Smart, Characteristics of C–F systems. In Organofluorine Chemistry:
Principles and Commercial Applications, R. E. Banks, B. E. Smart and
J. C. Tatlow Eds, Plenum: New York, 1994; (e) J. D. Dunitz and R.
Taylor, Chem.–Eur. J., 1997, 3, 89–98.
5 (a) R. Hoffmann, J. M. Howell and E. L. Muetterties, J. Am. Chem.
Soc., 1972, 94, 3047–3058; (b) R. S. McDowell and A. Streitwieser,
Jr., J. Am. Chem. Soc., 1985, 107, 5849–5855; (c) J. A. Deiters, R. R.
Holmes and J. M. Holmes, J. Am. Chem. Soc., 1988, 110, 7672–7681;
(d) P. Wang, Y. Zhang, R. Glaser, A. E. Reed, P. v. R. Schleyer and A.
Streitwieser, Jr., J. Am. Chem. Soc., 1991, 113, 55–64; (e) H. Wasada
and K. Hirao, J. Am. Chem. Soc., 1992, 114, 16–27; (f) G. R. J. Thatcher
and A. S. Campbell, J. Org. Chem., 1993, 58, 2272–2281; (g) P. Wang,
Y. Zhang, R. Glaser, A. Streitwieser and P. v. R. Schleyer, J. Comput.
Chem., 1993, 14, 522–529; (h) B. D. Wladkowski, M. Krauss and W. J.
Stevens, J. Phys. Chem., 1995, 99, 4490–4500.
13 I. Ruppert, K. Schlich and W. Volbach, Tetrahedron Lett., 1984, 25,
2195–2198.
14 V. A. Petrov, Tetrahedron Lett., 2001, 42, 3267–3269.
15 (a) J. Russell and N. Roques, Tetrahedron, 1998, 54, 13771–13782; (b) S.
Large, N. Roques and B. R. Langlois, J. Org. Chem., 2000, 65, 8848–
8856.
16 (a) L. Jablonski, J. Joubert, T. Billard and B. R. Langlois, Synlett,
2003, 2, 230–232; (b) D. Inschauspe, J.-B. Sortais, T. Billard and B. R.
Langlois, Synlett, 2003, 2, 233–235; (c) L. Jablonski, T. Billard and B.
R. Langlois, Tetrahedron Lett., 2003, 44, 1055–1057.
17 J. Joubert, S. Roussel, C. Christophe, T. Billard, B. R. Langlois and T.
Vidal, Angew. Chem., Int. Ed., 2003, 42, 3133–3136.
6 R. S. Berry, J. Chem. Phys., 1960, 32, 933–938.
7 (a) S. Kojima, K. Kajiyama, M. Nakamoto and K.-y. Akiba, J. Am.
Chem. Soc., 1996, 118, 12866–12867; (b) S. Kojima, K. Kajiyama, M.
Nakamoto, S. Matsukawa and K.-y. Akiba, Eur. J. Org. Chem., 2006,
218–234.
8 (a) J. C. Martin, Science, 1983, 221, 509–514; (b) W. H. Stevenson III, S.
Wilson, J. C. Martin and W. B. Farnham, J. Am. Chem. Soc., 1985, 107,
6340–6352; (c) R. S. Michalak, S. R. Wilson and J. C. Martin, J. Am.
Chem. Soc., 1984, 106, 7529–7539; (d) T. Kawashima, K. Kato and R.
Okazaki, J. Am. Chem. Soc., 1992, 114, 4008–4010; (e) Y. Uchiyama, K.
Kato and T. Kawashima, J. Am. Chem. Soc., 2003, 125, 13346–13347;
(f) Y. Uchiyama, K. Kato and T. Kawashima, J. Org. Chem., 2006, 71,
659–670.
9 (a) K. Kajiyama, M. Yoshimune, M. Nakamoto, S. Matsukawa, S.
Kojima and K.-y. Akiba, Org. Lett., 2001, 3, 1873–1875; (b) S. Kojima,
M. Sugino, S. Matsukawa, M. Nakamoto and K.-y. Akiba, J. Am.
Chem. Soc., 2002, 124, 7674–7675; (c) S. Matsukawa, S. Kojima, K.
Kajiyama, Y. Yamamoto, K.-y. Akiba, S. Re and S. Nagase, J. Am.
Chem. Soc., 2002, 124, 13154–13170; (d) S. Matsukawa, Y. Yamamoto
and K.-y. Akiba, Heterocycles, 2003, 59, 707–719; (e) K. Kajiyama,
M. Yoshimune, S. Kojima and K.-y. Akiba, Eur. J. Org. Chem., 2006,
2739–2746; (f) T. Adachi, S. Matsukawa, M. Nakamoto, K. Kajiyama,
18 T. Billard, B. R. Langlois and G. Blond, Tetrahedron Lett., 2000, 41,
8777–8780.
19 E. T. McBee, C. W. Roberts and A. F. Meiners, J. Am. Chem. Soc.,
1957, 79, 335–337.
20 (a) P. G. Gassman and N. J. O’Reilly, Tetrahedron Lett., 1985, 26,
5243–5246; (b) K. Kawakami and H. G. Kuivila, J. Org. Chem., 1969,
34, 1502–1504; (c) A. Solladie-Cavallo and J. Suffert, Tetrahedron Lett.,
1984, 25, 1897–1900; (d) A. Solladie-Cavallo and J. Suffert, Synthesis,
1985, 659–662.
21 (a) E. T. McBee, C. W. Roberts and S. G. Curtis, J. Am. Chem. Soc.,
1955, 77, 6387–6390; (b) J. A. Beel, H. C. Clark and D. Whyman, J.
Chem. Soc., 1962, 4423–4425.
22 T. A. Geissman, Org. React., 1944, 2, 94–113.
23 R. Stewart and R. Van Der Linden, Can. J. Chem., 1960, 38, 399–406.
24 (a) J. H. Simons and E. O. Ramler, J. Am. Chem. Soc., 1943, 65, 389–
392; (b) J. P. Guthrie and J. Cossar, Can. J. Chem., 1990, 68, 1640–1642.
25 R. P. Singh, G.-F. Cao, R. L. Kirchmeier and J. M. Shreeve, J. Org.
Chem., 1999, 64, 2873–2876.
26 Z. Otwinowski and W. Minor, Methods Enzymol., 1997, 276, 307–326.
27 G. M. Sheldrick, SHELX-97, University of Go¨ttingen, Go¨ttingen,
Germany, 1997.
This journal is
The Royal Society of Chemistry 2010
Dalton Trans., 2010, 39, 9823–9829 | 9829
©