Preparation and properties of fluorenylidenephosphines bearing an electron-donating substituent, 2-alkoxy-4,6-di-t-butylphenyl or 2-(alkoxymethyl)-4,6-di-t-butylphenyl

Article abstract of DOI:10.1016/S0040-4039(02)01860-9

Fluorenylidenephosphines having a 2,4-di-t-butyl-6-methoxyphenyl, 2,4-di-t-butyl-6-(methoxymethyl)phenyl or 2,4-di-t-butyl-6-(phenoxymethyl)phenyl group were prepared. ³¹P NMR chemical shifts of the fluorenylidenephosphines indicated that electron-donating effects through space are not so strong between the alkoxy group and the double-bonded phosphorus atom. The structure of a tungsten carbonyl complex of [2,4-di-t-butyl-6-(phenoxymethyl)phenyl](fluorenylidene)phosphine was analyzed by X-ray crystallography.

Full text of DOI:10.1016/S0040-4039(02)01860-9

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 43 (2002) 7953–7959
Preparation and properties of fluorenylidenephosphines bearing
an electron-donating substituent, 2-alkoxy-4,6-di-t-butylphenyl or
2-(alkoxymethyl)-4,6-di-t-butylphenyl
Kozo Toyota, Subaru Kawasaki and Masaaki Yoshifuji*
Department of Chemistry, Graduate School of Science, Tohoku University, Aoba, Sendai 980-8578, Japan
Received 31 July 2002; revised 29 August 2002; accepted 30 August 2002
Abstract—Fluorenylidenephosphines having a 2,4-di-t-butyl-6-methoxyphenyl, 2,4-di-t-butyl-6-(methoxymethyl)phenyl or 2,4-di-
t-butyl-6-(phenoxymethyl)phenyl group were prepared. 31P NMR chemical shifts of the fluorenylidenephosphines indicated that
electron-donating effects through space are not so strong between the alkoxy group and the double-bonded phosphorus atom. The
structure of a tungsten carbonyl complex of [2,4-di-t-butyl-6-(phenoxymethyl)phenyl](fluorenylidene)phosphine was analyzed by
X-ray crystallography. © 2002 Elsevier Science Ltd. All rights reserved.
Studies on intramolecular donor-stabilized species1
have recently been developed in main-group element
chemistry. Tuning of the electronic effect in such sys-
tems and comparison of properties of the electronically
perturbed compounds with those of kinetically stabi-
lized compounds are now subjects of interest. We have
studied the kinetic stabilization in multiple-bonded
phosphorus compounds. The 2,4,6-tri-t-butylphenyl
(hereafter abbreviated to Mes*) group is a typical and
powerful bulky protecting group, and by utilizing this
substituent we and others have successfully prepared
various types of phosphorus compounds of unusual
structures2 such as diphosphenes,3 phosphacumulenes,4
phospharadialenes,5 and dichalcogenoxophosphoranes.6
In the course of our continuing efforts towards system-
atic modification of the Mes* group, we have examined
various substituents such as 2,4-di-t-butyl-6-(dialkyl-
amino)phenyl,7 2,4-di-t-butyl-6-(dialkylaminomethyl)-
phenyl,8 2,4-di-t-butyl-6-methoxyphenyl,9 and 2,4-di-t-
butyl-6-(methoxymethyl)phenyl.10 For example, we
have prepared dithioxophosphorane derivatives 1a–f
(Schemes 1 and 2). The Mes*-substituted dithioxophos-
phorane 1a is thermally stable under an inert atmo-
sphere,6a–c whereas donor-stabilized compounds 1b7a
and 1c8a are stable even in air. On the other hand,
compound 1d is stable only in a solution and dimerizes
to trans- and cis-2 upon concentration.9 Compound 1e
rearranged to 310b at 180°C.11 A similar rearrangement
proceeds in the case of 1f to give 4.12
The research of structure–property relationships of
other essentially reactive species, such as phos-
phaethenes (phosphaalkenes), is also important. Polar-
ization of the ꢀPꢁCꢂ bond in phosphaethenes (in the
classical notation, Pd+=Cd−) is supposed to be not so
large as that of the ꢀPꢁS bond (Pd+=Sd−) in dithiox-
ophosphoranes. Thus, it is interesting to know how the
donor-stabilization operates in the two different sys-
Keywords: phosphorus compounds; phosphaalkenes; donors; steric
effects.
* Corresponding author. Tel./fax: +81 22 217 6562; e-mail: yoshifj@
mail.cc.tohoku.ac.jp
Scheme 1.
0040-4039/02/$ - see front matter © 2002 Elsevier Science Ltd. All rights reserved.
PII: S0040-4039(02)01860-9

7954
K. Toyota et al. / Tetrahedron Letters 43 (2002) 7953–7959
Then preparation of 8g, bearing the 2,4-di-t-butyl-6-
(methoxymethyl)phenyl, was examined in a similar
manner. Although the formation of a trace amount of
8g was observed by 31P NMR spectroscopy after the
successive treatment of dichlorophosphine 5g with 9-
fluorenyllithium and DBU, an attempted isolation of 8g
failed due to decomposition. Moreover, the instability
of dichlorophosphine 5g seems to limit its synthetic
applications: As we have observed previously,10
a
cyclization reaction of 5g occurs15 at room temperature
(Scheme 4) to eliminate chloromethane.
Thus, in order to suppress the instability, phen-
oxymethyl congener 5h (as an alternative starting mater-
ial for various phosphorus species) was prepared as
follows (Scheme 5): a mixture of 2-bromo-1-bromo-
methyl-3,5-di-t-butylbenzene (9,10a 5.00 g, 13.8 mmol),
phenol (16.3 mmol), potassium carbonate (22.7 mmol),
and potassium iodide (1.5 mmol) in DMF (30 mL) was
stirred at room temperature for 28 h to give 10 in 88%
yield.
Scheme 2.
tems. We now report here the preparation and proper-
ties of phosphaethenes bearing bulky aryl substituents
with electron-donating alkoxy or aryloxy groups at the
o-position.13
When bromobenzene 10 was treated with butyllithium
and water successively, compound 11 was formed to
show that the halogen–metal exchange reaction pro-
ceeded. Reaction of 10 with butyllithium followed by
treatment with PCl3 afforded dichlorophosphine 5h
[31P{1H} NMR (162 MHz, CDCl3) l=162.3; MS m/z
(rel. intensity) 400 (M++4; 0.3), 398 (M++2; 1), 396 (M+;
2), and 303 (M+−OPh; 100)]. Dichlorophosphine 5h is
stable at room temperature under an inert atmosphere
and the cyclization reaction did not occur, while 5h
reacted with methanol to give 12, in contrast to 5g.
First, a fluorenylidenephosphine bearing a 2,4-di-t-
butyl-6-methoxyphenyl (abbreviated to Mox) group
was prepared as follows (Scheme 3): 9-fluorenyllithium
was allowed to react with dichlorophosphine 5d9a in
THF at −78°C to form chloro(fluorenyl)phosphine 6d
[31P NMR (81 MHz, CDCl3) l=83.9; MS m/z (rel.
intensity) 452 (M++2; 13), 450 (M+; 34), and 285 (Mox-
PCl+; 100)]. Then 6d in THF was treated with 1,8-diaza-
bicyclo[5.4.0]undec-7-ene (DBU) in the presence of
Reaction of 5h with 9-fluorenyllithium gave chloro-
(fluorenyl)phosphine 6h [31P NMR (162 MHz, CDCl3)
l=82.2; MS m/z (rel. intensity) 528 (M++2; 0.8), 526
,
molecular sieves 4 A MS to give fluorenylidenephos-
phine 8d in 70% yield.14
(M+; 2), and 165 (C13H9 ; 100)] (Scheme 3). Treatment
+
of 6h with DBU formed the corresponding fluorenyl-
idenephosphine 8h, although an attempted isolation of
8h from the reaction mixture failed because a decompo-
sition reaction occurred during the isolation process.
However, 8h was successfully isolated in the reaction of
7h [31P NMR (162 MHz, THF–C6D6) l=95.8] with
potassium fluoride in the presence of 18-crown-6 (83%
yield based on 10). Although fluorenylidenephosphine
8h itself was not so stable in air and was gradually
hydrolyzed by moisture to give 13 (Scheme 6), pen-
tacarbonyltungsten complex 14 [formed by reaction of
8h with W(CO)5(thf) in THF, 22% yield] was stable in
air.
Scheme 3.
Scheme 4.

K. Toyota et al. / Tetrahedron Letters 43 (2002) 7953–7959
7955
Scheme 5.
importance of intramolecular coordination. The value
,
for 14 is 3.438(6) A, which means it is slightly out of
van der Waals contact [the sum of van der Waals radii
23
,
of the atoms is 3.30 A], in contrast to the case of 1c
or the donor-stabilized silene 17, where the nitrogen
atoms participate in the intramolecular donor stabiliza-
tion. The distance between the phosphorus center and
the nitrogen atom is 1.921(8) A in 1c [sum of van der
Waals radii of the atoms (3.44 A)].
distance between the nitrogen atom and the silicon
atom is 2.004(2) A, which is much shorter than the sum
of van der Waals radii of the atoms (3.54 A).
,
8a,23
,
In 17, the
,
13b,23
,
Table 1 shows 31P NMR data of fluorenylidenephosphi-
nes 8d,g,h, and some of the related phosphaethenes. A
signal of 8d showed a higher-field shift in 31P NMR
spectrum, compared to that of the kinetically stabilized
molecule 8a,16 while a chemical shift of 8d was very
close to those of methoxymethyl congener 8g and phe-
noxymethyl congener 8h. Although the anisotropic
effect of the aromatic ring in 8h should be taken into
account, these facts may indicate that the alkoxy group
has an electron-donating effect on the phosphorus atom
in 8d,g,h. However, the electron-donating effect in
8d,g,h is not so strong according to the 31P NMR study.
This resembles the case of 1d: 31P NMR signal of 1d
[lP(C6D6)=277.6] is close to that of 1a [lP(CDCl3)=
Scheme 6.
The structure of complex 14 was analyzed by X-ray
crystallography.19 Fig. 1 shows an ORTEP20 drawing of
the molecular structure. The atoms W(1), P(1), C(1),
C(2), and C(13) lie on the same plane within 0.09 A,
and the atom C(14) deviates 0.37(1) A from the plane.
,
,
Sums of the angles around P(1) and C(1) are 358.2 and
359.8°, respectively, indicating that the pyramidariza-
tion at the phosphorus center is small and the phospho-
rusꢀcarbon double bond system is essentially planar in
14. The aromatic ring C(15)–C(19) is nearly perpendic-
ular to the ꢀPꢁCꢂ plane (interplanar angle: 91.5(2)°).
The bond length of the phosphorusꢀcarbon double
,
bond in 14 is 1.692 (8) A, which is longer than that in
21
,
1,6-diphosphahexa-1,5-diene complex 15 [1.66(7) A]
22
,
or 1-phosphabutatriene complex 16 [1.664(6) A]
(Chart 1). This fact may suggest that the bond order of
the PꢁC bond in 14 is decreased by a slight interaction
with the phenoxy group, although the phospho-
,
rusꢀtungsten bond length in 14 [2.496(2) A] is shorter
,
than that for 15 [2.539(2) A] and close to that for 16
,
[2.506(1) A].
The distance between the phosphorus atom and the
oxygen atom of the phenoxy group might indicate the
Chart 1.

7956
K. Toyota et al. / Tetrahedron Letters 43 (2002) 7953–7959
Figure 1. Molecular structure of 14, showing the atomic labeling scheme with thermal ellipsoids (30% probability). Some selected
,
bond lengths (A) and angles (°): P(1)–W(1), 2.496(2); P(1)–C(1), 1.692(8); P(1)–C(14), 1.834(7); W(1)–P(1)–C(1), 133.3(3);
W(1)–P(1)–C(14), 115.3(3); P(1)–C(1)–C(2), 129.6(6); P(1)–C(1)–C(13), 125.2(6); C(1)–P(1)–C(14), 109.6(4); C(2)–C(1)–C(13),
105.0(6).
298.2] and the oxygene–phosphorus interaction in 1d
seems to be weak, while the chemical shift of 1c
[lP(CDCl3)=149.6] appears upfield by ca. 150 ppm to
that of 1a and strong nitrogen–phosphorus interaction
was observed in the crystal of 1c (see above). In addi-
tion, the instability of 8d,g,h suggests that the donor
groups in these molecules do not sufficiently stabilize
the phosphorusꢀcarbon double bond, while kinetically
stabilized 8a is very stable at room temperature even in
air.
the aromatic ring. Further studies on structure–prop-
erty relationships of the phosphaethenes are in pro-
gress.
Selected data of compounds
8d: Yellow powder, mp 142–145°C; 1H NMR (600
MHz, CD2Cl2) l=1.40 (9H, s, p-t-Bu), 1.41 (9H, s,
o-t-Bu), 3.60 (3H, s, OMe), 6.33 (1H, m), 6.82 (1H, m),
6.89 (1H, d, J=1.3 Hz), 7.19 (1H, m), 7.27–7.33 (3H,
m), 7.60 (1H, m), 7.64 (1H, m), and 8.16 (1H, m);
1
13C{1H} NMR (150 MHz, CD2Cl2) l=171.8 (d, JPC
=
In summary, an alkoxy group or alkoxymethyl group at
the o-position in arylphosphaethene does not strongly
stabilize the PꢁC system, similarly to the cases of
dithioxophosphorane derivatives 1d,f. Nevertheless,
modification of the 2,4-di-t-butyl-6-(phenoxymethyl)-
phenyl group in the phenyl moiety seems to be promis-
ing for the purpose of fine-tuning the electronic state of
a multiple-bonded phosphorus compound, because the
electron-donating ability of the oxygen atom can be
changed by introducing various functional groups into
40.1 Hz, P=C); 31P{1H} NMR (81 MHz, C6D6) l=
246.4; UV (hexanes) 225 (log m 4.2), 238 (4.6), 253 (4.3),
266 (4.4) 270 (4.4), 275 (4.5), 308 (3.6), and 363 nm
(4.2); IR (KBr) 1647, 1589, 1442, 1394, 1325, 1207,
1055, 847, 769, and 729 cm−1; MS (70 eV) m/z (rel
intensity) 414 (M+; 100), 249 (MoxP+−1; 75), 233
(MoxP+−Me−2; 6), 219 (Mox+; 5), 193(M+−Mox−2;
20), 165 (Fluorene+; 42), and 57 (t-Bu+; 20). Found:
m/z 414.2115. Calcd for C28H31OP: M, 414.2113.

K. Toyota et al. / Tetrahedron Letters 43 (2002) 7953–7959
Table 1. 31P NMR data of fluorenylidenephosphines in CDCl3
7957
a
R
m
lP
JWP (Hz)
t-Bu
None
None
None
None
None
None
W(CO)5
(8a)
256.5b
257.2
254.0
247.9
249.7
245.8
193.9
i-Prc
Mec
OMe
CH2OMe
CH2OPh
CH2OPh
(8d)
(8g)
(8h)
(14)
281.4
a Relative to external 85% H3PO4.
b In Ref. 16, lP=253.1 in C6H6.
c Formed from the corresponding dichlorophosphines17,18 by a method similar to that for 8d. Attempted isolation using silica gel column
chromatography failed.
3
1
o-t-Bu), 3.84 (3H, d, JPH=12.3 Hz, OMe), 5.51 (1H,
8h: Yellow oil; H NMR (400 MHz, CDCl3) l=1.44
2
2
d, JHH=13.0 Hz, CH
Hz, CHH%O), 6.97 (1H, t, J=7.5 Hz), 7.05 (2H, d,
6 H’O), 5.61 (1H, d, JHH=13.0
(9H, s, p-t-Bu), 1.54 (9H, s, o-t-Bu), 4.82 (1H, d,
2JHH=12.7 Hz, CH
6
HO), 5.30 (1H, d, JHH=12.7 Hz,
2
6
J=8.6 Hz), 7.30 (2H, dd, J=8.6 Hz and J=7.5 Hz),
7.51 (1H, d, J=6.0 Hz), 7.64 (1H, s), and 8.46 (1H, d,
1JPH=569.4 Hz, PH); 13C{1H} NMR (100 MHz,
CHHO), 6.10 (1H, dd, J=8.0 Hz and J=2.6 Hz),
6
6.8–6.9 (4H, m), 7.16 (2H, m), 7.25 (2H, d, J=7.5 Hz),
7.35 (2H, dd J=7.5 Hz and J=7.5 Hz), 7.56 (1H, d,
J=1.6 Hz), 7.63 (2H, dd, J=8.0 Hz and J=8.0 Hz),
7.68 (1H, br. s), and 8.14 (1H, dd, J=8.0 Hz and
J=7.5 Hz); 13C{1H} NMR (100 MHz, CDCl3) l=70.5
(d, 3JPC=9.1 Hz, CH2O), 173.4 (d, 1JPC=43.1 Hz,
PꢁC); 31P{1H} NMR (162 MHz, CDCl3) l=245.8; UV
(hexanes) 256 (log m 4.24), 266 (4.33), 275 (4.38), and
365 nm (4.08); IR (NaCl) 1722, 1597, 1492, 1444, 1365,
1295, 1234, 1172, 1033, 883, 759, and 690 cm−1; MS (70
eV) m/z (rel. intensity) 490 (M+; 65), 397 (M+−OPh;
100), 383 (M+−CH2OPh; 34), 341 (M+−OPh−t-Bu+1;
2
CDCl3) l=53.8 (d, JPC=6.1 Hz, P-OMe) and 68.5 (d,
3JPC=6.4 Hz, CH2O); 31P NMR (162 MHz, CDCl3)
l=31.9 (d, 1JPH=569.6 Hz); IR (NaCl) 3060–2870
(br.), 2431, 1727, 1600, 1546, 1496, 1402, 1375, 1240,
1220, 1010, 883, 838, 790, 855, and 692 cm−1; MS (70
eV) m/z (rel. intensity) 374 (M+; 8), 356 (M+−O−H−1;
11), and 281 (M+−OPh; 100). Found: m/z 374.2008.
Calcd for C22H31O3P: M, 374.2011.
1
13: Colorless powder, mp 206–208°C; H NMR (500
MHz, CDCl3) l=1.03 (9H, s, p-t-Bu), 1.43 (9H, s,
o-t-Bu), 4.95 (1H, dd, JPH=24.5 Hz, JHH=7.0 Hz,
41), 165 (C13H9 ; 32), 149 (84), and 57 (t-Bu+; 86).
+
2
3
Found: m/z 490.2432. Calcd for C34H35OP: M,
2
P-CH), 5.35 (1H, d, JHH=11.3 Hz, CH
6
H%O), 6.25 (1H,
d, J=7.5 Hz), 6.41 (1H, d, JHH=11.3 Hz, CHH%O),
6.91 (1H, dd, J=7.5 Hz and J=7.5 Hz), 6.98 (1H, t,
490.2426.
2
6
10: Colorless powder, mp 62–64°C; 1H NMR (400
MHz, CDCl3) l=1.36 (9H, s, p-t-Bu), 1.63 (9H, s,
o-t-Bu), 5.22 (2H, s, CH2O), 7.05 (2H, d, J=7.5 Hz),
7.10 (1H, t, J=8.7 Hz), 7.38 (2H, dd, J=8.7 Hz and
J=7.5 Hz), 7.53 (1H, d, J=2.4 Hz), and 7.55 (1H, d,
J=2.4 Hz); 13C{1H} NMR (100 MHz, CDCl3) l=71.6
(CH2O); IR (KBr) 1595, 1495, 1471, 1427, 1387, 1365,
1265, 1174, 1080, 1020, 885, 835, 750, and 692 cm−1;
MS (70 eV) m/z (rel. intensity) 376 (M++2; 10), 374
(M+; 10), 283 (M+−OPh+2; 75), 281 (M+−OPh; 76), 187
(M+−Br−CH2OPh+1; 6), and 57 (t-Bu+; 100). Found:
m/z 374.1247. Calcd for C21H27BrO: M, 374.1245.
1
3
J=7.3 Hz), 7.08 (1H, dd, JPH=502.6 Hz and JHH
=
7.0 Hz, PH), 7.10 (2H, d, J=8.0 Hz), 7.26–7.31 (1H,
m), 7.30 (2H, dd, J=8.0 Hz and J=7.3 Hz), 7.40 (1H,
dd, J=7.5 Hz and J=7.5 Hz), 7.47 (1H, dd, J=7.5 Hz
and J=7.5 Hz), 7.55 (1H, d, J=4.5 Hz), 7.69 (1H, s),
7.73 (1H, d, J=7.5 Hz), 7.81 (1H, d, J=7.5 Hz) and
8.05 (1H, d, J=7.5 Hz); 13C{1H} NMR (125 MHz,
1
CDCl3) l=50.8 (d, JPC=56.3 Hz, P-CH) and 68.5 (d,
3JPC=6.0 Hz, CH2O); 31P NMR (162 MHz, CDCl3)
1
2
l=30.8 (dd, JPH=502.6 Hz and JPH=24.5 Hz); IR
(KBr) 3133, 2998, 1596, 1485, 1448, 1230, 1180, 1008,
800, and 748 cm−1; MS (70 eV) m/z (rel. intensity) 508
(M+; 10), 415 (M+−OPh; 13), 343 (M+−C13H9; 51), 325
(M+−C13H10+−OH; 11), 249 (M+−C13H10−OPh; 42), and
165 (C13H9 ; 100). Found: m/z 508.2502. Calcd for
C34H37O2P: M, 508.2531.
11: Colorless crystals, mp 53–54°C; 1H NMR (400
MHz, CDCl3) l=1.36 (18H, s, t-Bu), 5.05 (2H, s,
CH2O), 6.99 (1H, t, J=7.6 Hz), 7.04 (2H, dd, J=8.8
Hz and J=1.2 Hz), 7.30–7.35 (4H, m), and 7.43 (1H, t,
J=1.8 Hz); 13C{1H} NMR (100 MHz, CDCl3) l=71.2
(CH2O); IR (KBr) 1599, 1494, 1473, 1367, 1295, 1238,
1172, 1081, 1014, 879, 829, 752. 713, and 692 cm−1; MS
(70 eV) m/z (rel. intensity) 297 (M++1; 100). Found:
m/z 296.2132. Calcd for C21H28O: M, 296.2140.
14: Orange prisms, mp 167°C (decomp.); 1H NMR (400
MHz, CDCl3) l=1.43 (9H, s, p-t-Bu), 1.57 (9H, s,
o-t-Bu), 5.17 (1H, dd, 2JHH=12.3 Hz and 4JP4H=1.6
2
Hz, CH
2.2 Hz, CHH
6
H%O), 5.52 (1H, dd, JHH=12.3 Hz and JPH
=
6
%O), 6.44 (1H, dd, J=8.0 Hz and J=3.6
Hz), 6.64–6.66 (2H, m), 6.83–6.90 (2H, m), 7.08–7.11
(2H, m), 7.24 (1H, ddd, J=7.4 Hz, J=7.4 Hz, and
12: Colorless crystals, mp 77–79°C; 1H NMR (400
MHz, CDCl3) l=1.31 (9H, s, p-t-Bu), 1.57 (9H, s,

7958
K. Toyota et al. / Tetrahedron Letters 43 (2002) 7953–7959
J=2.4 Hz), 7.34 (1H, dd, J=7.8 Hz and J=7.8 Hz),
7.41 (1H, ddd, J=7.4 Hz, J=7.4 Hz, and J=2.0 Hz),
7.62 (1H, d, J=7.2 Hz), 7.67 (1H, d, J=7.6 Hz),
7.72–7.78 (2H, m), and 8.69 (1H, dd, J=7.6 Hz and
J=4.0 Hz); 13C{1H} NMR (100 MHz, CDCl3) l=69.7
(d, 3JPC=8.6 Hz, CH2O), 168.2 (d, 1JPC=40.4 Hz,
Hirano, M.; Toyota, K. Chem. Lett. 1993, 1715; (c)
Yoshifuji, M.; Sangu, S.; Kamijo, K.; Toyota, K. J.
Chem. Soc., Chem. Commun. 1995, 297; (d) Yoshifuji,
M.; Sangu, S.; Kamijo, K.; Toyota, K. Chem. Ber. 1996,
129, 1049.
8. (a) Yoshifuji, M.; Kamijo, K.; Toyota, K. Tetrahedron
Lett. 1994, 35, 3971; (b) Yoshifuji, M.; Kamijo, K.;
Toyota, K. Chem. Lett. 1994, 1931; (c) Kamijo, K.;
Otoguro, A.; Toyota, K.; Yoshifuji, M. Bull. Chem. Soc.
Jpn. 1999, 72, 1335.
9. Yoshifuji, M.; An, D.-L.; Toyota, K.; Yasunami, M.
Chem. Lett. 1993, 2069.
10. (a) Yoshifuji, M.; Kamijo, K.; Toyota, K. Bull. Chem.
Soc. Jpn. 1993, 66, 3440; (b) Kamijo, K.; Toyota, K.;
Yoshifuji, M. Chem. Lett. 1999, 567.
11. An attempted preparation of a methoxymethyl congener
of 1e, by a reaction of the corresponding primary phos-
phine with elemental sulfur in benzene in the presence of
DBU at room temperature, resulted in a complex mix-
ture of products.10b
2
1
PꢁC6 ), 195.9 (d, JPC=9.6 Hz, satellite JWC=125.7 Hz,
2
COeq), and 198.8 (d, JPC=31.7 Hz, COax); 31P NMR
(162 MHz, CDCl3) l=193.9 (satellite, 1JWP=281.4
Hz); UV (hexanes) 211 (log m 4.90), 337 (3.88), and 474
nm (4.38); IR (KBr) 2071, 1957, 1919, 1597, and 1232
cm−1; MS (70 eV) m/z (rel. intensity) 814 (M+; 6), 730
(M+−3CO; 8), 674 (M+−5CO; 8), 490 (M+−W(CO)5;
42), 397 (M+−OPh−W(CO)5; 63), 341 (M+−t-Bu−OPh−
W(CO)5; 23), 165 (Flu++1; 34), 57 (t-Bu+; 89), and 28
(CO+; 100).
Acknowledgements
12. Yoshifuji, M.; Nakazawa, M.; Sato, T.; Toyota, K. Tet-
rahedron 2000, 56, 43.
This work was supported in part by the Grants-in-Aid
for Scientific Research on Priority Area (Nos. 09239104
and 12020205) from the Ministry of Education, Cul-
ture, Sports, Science and Technology, Japan.
13. A part of this work, including the preparation of 8d,
was presented at the 78th National Meeting of the
Chemical Society of Japan, Funabashi, March 2000,
Abstr., No. 2G310. Recently, Oehme and co-workers
reported the preparation of intramolecularly donor-sta-
bilized silenes: (a) Mickoleit, M.; Schmohl, K.; Kempe,
R.; Oehme, H. Angew. Chem., Int. Ed. 2000, 39, 1610;
(b) Mickoleit, M.; Kempe, R.; Oehme, H. Chem. Eur. J.
2001, 7, 987.
14. When dichloro[2,4-di-t-butyl-6-(dimethylamino)phenyl]-
phosphine was used instead of 5d, a signal at lP (THF–
C6D6)=252 was observed by 31P NMR spectroscopy.
However, an attempted isolation of the corresponding
compound failed. We tentatively assign the signal to
[2,4 - di - t - butyl - 6 - (dimethylamino)phenyl](9 - fluorenyl-
idene)phosphine.
15. An analogous cyclization reaction has recently been
reported: (a) Kobayashi, J.; Goto, K.; Kawashima,
T. J. Am. Chem. Soc. 2001, 123, 3387; (b) Kobayashi,
J.; Goto, K.; Kawashima, T.; Schmidt, M. W.; Nagase,
S. J. Am. Chem. Soc. 2002, 124, 3703. See also, Ref.
12.
16. Romanenko, V. D.; Ruban, A. V.; Povolotskii, M. I.;
Polyachenko, L. K.; Markovskii, L. N. Zh. Obshch.
Khim. 1986, 56, 1186.
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13.536(2), c=10.908(3) A, h=90.05(1), i=107.02(4),
3
,
k=94.28(1)°, V=1776(1) A , Z=2,
Dcalcd=1.523 g
cm−1, v(Mo Ka)=33.45 cm−1. 5602 Unique reflections
with 2q550.1° were collected at 150 K. Of these 5448
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