Reactions and Properties of Spirophosphoranes
A R T I C L E S
benzyl bromide (1.50 mL, 12.6 mmol) was added. The mixture was
stirred for 7 h at room temperature. After the solution was treated with
water (100 mL), the mixture was extracted with Et2O (100 mL × 2),
the ethereal layer was washed with brine (100 mL), and the extract
was dried over MgSO4. The crude white solid was recrystallized from
n-hexane/CH2Cl2 to afford colorless crystals of 2c (4.34 g, 7.15 mmol,
experimental results and gave clearer insights into the present
chemistry. The results presented here show that anti-apicophilic
phosphoranes have provided new insights into a full picture of
the nature of the pentacoordinate state of phosphorus. Here, we
have presented a new, unique, and well-designed example in
the chemistry of stereoelectronic effects. Further investigations
concerning this unique group of compounds are currently
ongoing.
1
90.7%). H NMR (CDCl3, δ) 8.24 (dd, 2H, J ) 10.7, 8.1 Hz), 7.71-
7.57 (m, 6H), 7.15-7.08 (m, 3H), 6.99-6.96 (m, 2H), 3.76 (dd, 1H,
2
2
2JP-H ) 15.6 Hz, JH-H ) 13.7 Hz), 3.71 (dd, 1H, JP-H ) 13.7 Hz,
2JH-H ) 13.7 Hz); 19F NMR (CDCl3, δ) -74.6 (q, 6F, JF-F ) 9.8
4
Experimental Section
Hz), -75.0 (q, 6F, JF-F ) 9.8 Hz); 31P NMR (CDCl3, δ) -22.0; mp
4
General. Melting points were measured with a Yanaco micro melting
128-129 °C. Anal. Calcd for C25H15F12O2P: C, 49.52; H, 2.49.
Found: C, 49.25; H, 2.18.
1
point apparatus and are uncorrected. H NMR (400 MHz), 13C NMR
(100 MHz), 19F NMR (376 MHz), and 31P NMR (162 MHz) spectra
Observation of 12-P-6 Phosphate Bearing a P-F Bond (4). To a
THF (0.6 mL) solution of 1b (25 mg, 0.044 mmol) in an NMR tube
was added TBAF (tetra-n-butylammonium fluoride, 1.0 M solution in
THF, 0.05 mL, 0.05 mmol) at room temperature. Then the NMR tube
was loaded into an NMR spectrometer (JEOL EX-400) at -30 °C.
After 10 min, 31P and 19F NMR spectra were recorded. 19F NMR (THF,
1
were recorded on a JEOL EX-400 spectrometer. H NMR chemical
shifts (δ) are given in ppm downfield from Me4Si, determined by
residual chloroform (δ ) 7.26). 13C NMR chemical shifts (δ) are given
in ppm downfield from Me4Si, determined by chloroform-d (δ ) 77.0).
19F NMR chemical shifts (δ) are given in ppm downfield from external
CFCl3. 31P NMR chemical shifts (δ) are given in ppm downfield from
external 85% H3PO4. Elemental analyses were performed on a Perkin-
Elmer 2400 CHN elemental analyzer.
1
δ) -51.4 (4, br d, 1F, JP-F ) 706 Hz), -72.8 (1b, br s, 6F), -73.2
(4, br s, 3F), -74.1 (4, br s, 9F), -75.3 (1b, br s, 6F); 31P NMR (THF,
1
δ) -0.8 (1b, s), -105.0 (4, d, JP-F ) 706 Hz); 1b/4 ) ca. 1:1.
All reactions were carried out under N2 or Ar. THF and Et2O were
freshly distilled from Na-benzophenone, n-hexane was distilled from
Na, and all other solvents were distilled from CaH2. Preparative thin-
layer chromatography was carried out on plates of Merck silica gel 60
GF254. Merck silica gel 60 was used for column chromatography.
[TBPY-5-12]-1-Phenylmethyl-3,3,3′,3′-tetrakis(trifluoromethyl)-
1,1′-spirobi[3H,2,1,λ5-benzoxaphosphole] (1c). n-BuLi (1.50 M hex-
ane solution, 19.3 mL, 30.3 mmol) was added to a mixture of t-BuOK
(3.41 g, 30.4 mmol) and toluene (3.30 mL, 31.0 mmol) suspended with
n-hexane (15 mL) at room temperature. This mixture was vigorously
stirred for 1 h. At 0 °C, Et2O (35 mL) was added to the mixture, and
then a solution of 3 (5.10 g, 9.88 mmol) in Et2O (60 mL) was transferred
dropwise. The mixture was stirred for 9 h at room temperature. Iodine
(7.90 g, 31.1 mmol) was added at -78 °C, and the resulting mixture
was stirred for 1 h. After the cooling bath was removed, stirring was
continued until the color of the mixture became dark-brown. After the
solution was treated with Na2S2O3 (aq) (100 mL), the mixture was
extracted with Et2O (100 mL × 2), and the ethereal layer was washed
with brine (100 mL) and dried over anhydrous MgSO4. The crude
product was subjected to column chromatography (n-hexane/CH2Cl2
) 2:1). The resulting pale red solid was washed with n-hexane to yield
a crystalline white solid of 1c (4.73 g, 7.81 mmol, 79.0%). Colorless
crystals suitable for X-ray analysis were obtained by recrystallization
from CH3CN. 1H NMR (CDCl3, δ) 7.73-7.71 (m, 2H), 7.66-7.61 (m,
2H), 7.58-7.51 (m, 4H), 7.14-7.11 (m, 3H), 6.98-6.97 (m, 2H), 3.96
(d, 2H, 2JP-H ) 10.7 Hz); 13C NMR (CDCl3, δ) 134.5 (d, 2JC-P ) 16.7
Hz), 134.4 (d, 1JC-P ) 82.5 Hz), 132.4 (d, JC-P ) 12.5 Hz), 132.2 (d,
JC-P ) 2.5 Hz), 131.3 (d, JC-P ) 10.8 Hz), 130.5 (d, JC-P ) 7.5 Hz),
Reaction of the R-Anion of 2c (8a-K(18-crown-6)) with PhCHO.
A THF (1.5 mL) solution of 2c (182 mg, 0.301 mmol) and 18-crown-6
ether (83.0 mg, 0.314 mmol) was added to a THF (0.5 mL) suspension
of KH (excess), and then the mixture was stirred for 20 min at room
temperature. After removal of KH by filtration and washing with THF
(1 mL), benzaldehyde (0.04 mL, 0.39 mmol) was added at 0 °C. The
mixture was stirred for 6 h at room temperature, and then the reaction
was quenched with aqueous NH4Cl. The mixture was extracted with
Et2O (80 mL), and the combined organic solution was washed with
brine (50 mL) and dried over anhydrous MgSO4. After the solvents
were removed by evaporation, the crude product was subjected to TLC
(n-hexane) to afford cis-stilbene (42.1 mg, 0.234 mmol, 77.6%) and
trans-stilbene (10.8 mg, 0.060 mmol, 19.9%). Total yield of stilbene
was 97.5% (cis/trans ) 80:20). cis-Stilbene 1H NMR (CDCl3, δ): 7.29-
7.20 (m, 10H), 6.62 (s, 2H). trans-Stilbene 1H NMR (CDCl3, δ): 7.55
(d, 4H, J ) 7.2 Hz), 7.39 (t, 4H, J ) 7.2 Hz), 7.29 (t, 2H, J ) 7.2 Hz),
7.14 (s, 2H).
Synthesis of 18B. To a THF (15 mL) solution of 1c (912 mg, 1.50
mmol) was added n-BuLi (1.50 M hexane solution, 1.10 mL, 1.65
mmol) at 0 °C. The mixture was stirred for 20 min at 0 °C, and then
benzaldehyde (0.18 mL, 1.77 mmol) was added. The mixture was stirred
for 64 h at room temperature, and then the reaction was quenched with
aqueous NH4Cl. The mixture was extracted with Et2O (150 mL), and
the extract was washed with brine (150 mL) and dried over anhydrous
MgSO4. After the solvents were removed by evaporation, the crude
product was separated by TLC (n-hexane/benzene ) 1:5) to afford a
white solid of 18B (620 mg, 0.870 mmol, 57.8%). Colorless crystals
suitable for X-ray analysis were obtained by recrystallization from
CDCl3. 1H NMR (CDCl3, δ) 7.86-7.84 (m, 1H), 7.71-7.68 (m, 2H),
7.61-7.46 (m, 3H), 7.31-7.27 (m, 1H), 7.13-6.88 (m, 8H), 6.54 (br,
129.8 (d, JC-P ) 10.0 Hz), 128.2 (d, JC-P ) 4.2 Hz), 126.8 (d, JC-P
)
)
1
5.0 Hz), 125.4 (d, JC-P ) 10.0 Hz), 122.1 (dq, J ) 8.3 Hz, JC-F
1
2
286 Hz), 121.8 (q, JC-F ) 287 Hz), 79.8 (septet, JC-F ) 31.7 Hz),
3H), 5.20-5.15 (m, 1H), 4.50-4.00 (br, 1H), 3.72-3.69 (m, 1H); 19
F
47.6 (d, 1JC-P ) 109 Hz); 19F NMR (CDCl3, δ) -75.1 (q, 6F, 4JF-F
)
NMR (CDCl3, δ) -74.3 (br s, 3F), -74.6 (br s, 3F), -75.2 (br s, 3F),
-76.0 (br s, 3F); 31P NMR (CDCl3, δ) -0.6 (br); mp 148-149 °C
(decomp). Anal. Calcd for C32H21F12O3P: C, 53.94; H, 2.97. Found:
C, 53.99; H, 3.08.
8.6 Hz), -76.3 (q, 6F, JF-F ) 8.6 Hz); 31P NMR (CDCl3, δ) -8.0;
mp 134-135 °C (decomp). Anal. Calcd for C25H15F12O2P: C, 49.52;
H, 2.49. Found: C, 49.77; H, 2.39.
4
[TBPY-5-11]-1-Phenylmethyl-3,3,3′,3′-tetrakis(trifluoromethyl)-
1,1′-spirobi[3H,2,1,λ5-benzoxaphosphole] (2c).19 To a Et2O (50 mL)
solution of 3 (4.07 g, 7.88 mmol) was added DBU (1.80 mL, 12.0
mmol) at room temperature. After the mixture was stirred for 30 min,
Isolation of 12-P-6 Phosphate Bearing an Oxaphosphetane Ring
(22B-K(18-crown-6)). 18B (299 mg, 0.420 mmol) and 18-crown-6
ether (113 mg, 0.428 mmol) were dissolved into CH2Cl2 (4 mL), and
then the solution was added to a CH2Cl2 (1 mL) suspension of KH
(excess) at 0 °C. The mixture was stirred for 10 min, and then the
remaining KH was removed by filtration and washed with CH2Cl2 (1
mL). The Schlenk apparatus was sealed, and the resulting pale yellow
filtrate was allowed to stand for 7 days. Dry n-hexane was slowly added
so as to create a two-phase solution, which was allowed to stand for 6
(27) Kawashima, T.; Kato, K.; Okazaki, R. J. Am. Chem. Soc. 1992, 114, 4008-
4010. Correction: J. Am. Chem. Soc. 1998, 120, 6848.
(28) Kawashima, T.; Kato, K.; Okazaki, R. Angew. Chem., Int. Ed. Engl. 1993,
32, 869-870. Correction: Angew. Chem., Int. Ed. Engl. 1998, 37, 1606.
(29) Kojima, S.; Sugino, M.; Matsukawa, S.; Nakamoto, M.; Akiba, K.-y. J.
Am. Chem. Soc. 2002, 124, 7674-7675.
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J. AM. CHEM. SOC. VOL. 124, NO. 44, 2002 13169