Synthesis and Fragmentation of New 2-Phosphabicyclo[2.2.2]octene 2-Oxides 631
8Ab: Repeated column chromatography affo-
trichlorosilane. The contents of the flask were stirred
at the boiling point in a nitrogen atmosphere for 8 h.
After filtration, the filtrate was concentrated in vacuo
to give a mixture of phosphinous chlorides 11A and
11B almost quantitatively.
rded 8Ab in a pure form; mp 185–187◦C (acetone);
1
31P and 13C NMR, Table 2; H NMR (CDCl3) δ 1.94
2
(d, JPH = 13.6, P CH3), 2.12 (s, C CH3), 6.65 (dd,
3
3 JPH = JHH = 6.9, C6 H).
8Bb: 31P and 13C NMR, Table 2.
Because of the sensitivity of the intermediate
(11) toward air and moisture, it was immediately
used in the next step. To ∼2.2 g (∼6.2 mmol) of
phosphinous chloride 11 in 60 ml of dry tetrahydro-
furan was added 7.8 mmol of arylmagnesium bro-
mide [prepared from 0.19 g (7.9 mmol) of magne-
sium and 2.2 g (7.8 mmol) of 2,4,6-triisopropyl-1-
bromobenzene in 20 ml of tetrahydrofuran] and the
mixture was stirred at the boiling point for 14 h. The
solvent was evaporated and the residue containing
arylphosphine 12 was taken up in the mixture of
60 ml of chloroform and 10 ml of water. The chlo-
roform phase was treated with 1.4 ml (∼12.4 mmol)
of 30% hydrogen peroxide at 0◦C, the cooling bath
was removed and the mixture stirred further at 26◦C
for 1.5 h. Excess of the peroxide was removed by
extraction with 3 × 25 ml of water. The chloroform
phase was dried (Na2SO4) and the solvent evapo-
rated to afford a 4:1 mixture of phosphine oxides
9Ac (δP 43.4) and 9Bc (δP 42.3). Repeated column
chromatography (3% methanol in chloroform, silica
gel) furnished 0.83 g (25%) 9Ac in a pure form.
9Ac: 31P NMR (CDCl3) δ 40.4; 13C NMR (CDCl3)
X-ray Structure Determination
for Compound 8Ab
Single crystals of 8Ab were obtained by slow
evaporation of an acetone solution of the com-
pound. The crystals are monoclinic, space group
˚
P21/n, a = 15.01(2), b = 6.56(1), c = 36.32(4) A, β =
◦
3
−3
˚
94(2) , V = 3569(8) A , Z = 4, Dc = 1.430 g cm .
The asymmetric unit contains two molecules of
8Ab, an acetone molecule, and a partially occu-
pied water (occupancy refined to 0.378) molecule
C33H36.76Cl2N6O7.38P2, Mw = 768.36. X-ray data were
collected from a crystal, having dimensions of 0.3 ×
0.05 × 0.05 mm3 by a Rigaku RAXIS-II imaging plate
detector using graphite monochromated Mo Kꢀ ra-
diation. A total of 3175 unique reflections were col-
lected, 2θmax = 42.86◦. The structure was solved by
direct methods using the teXsan package [12]. Re-
finements were carried out using the SHELXL-97
program [13] for 469 variables. All non-hydrogen
atoms were refined by the anisotropic mode, the hy-
drogen atoms being generated based upon geomet-
ric evidence and refined using the riding model. Two
hundred eighty nine restraints were applied. The ex-
tinction coefficient was refined to 0.025. At the end
of the refinement R = 0.0841, Rw = 0.2229(I > 2ꢁI),
and R = 0.1241, Rw = 0.2589 (all reflections). The
highest residual peak of the final difference electron
ꢁ
δ 23.7 (C4 CH(CH3)2), 23.9 (J = 10.3, C4 CH3),
ꢁ
ꢁ
25.1 (C2 CH(CH3)2), 25.2 (C6 CH(CH3)2), 32.4
ꢁ
ꢁ
(C2 CHMe2), 34.3 (C4 CHMe2), 41.5 (C7), 42.4 (J =
63.6, C1), 43.5 (J = 71.0, C3), 44.6 (J = 5.8, C4), 49.8
ꢁ
(J = 9.8, C8), 121.8 (C6), 123.3 (J = 11.3, C3 ), 126.7
ꢁꢁ
ꢁꢁ
ꢁꢁ
(C3 ), 129.1 (C4 ), 129.4 (C2 ), 140.2 (J = 10.3, C5),
ꢁ
ꢁ
152.4 (J = 10.8, C2 ), 153.1 (C4 ), 174.5 (C9), 176.5
1
(J = 14.8, C11); H NMR (CDCl3) δ 1.26 (d, J = 6.9,
−3
˚
density map was 0.38(8) eA .
ꢁ
C4 CH(CH )2), 1.31 (d, J = 6.2, ortho CH(CH3)2),
3
1.72 (s, C4 CH3), 6.12 (dd, 3 JPH = JHH = 7.7, C6 H);
3
FAB–MS: (M + H)+ = 538; (M + H)f+ound = 538.2169,
Preparation of the P-(2,4,6-Triisopropylphenyl)
2-Phosphabicyclo[2.2.2]octene 2-Oxides 9Ac
and 9Bc
C31H38ClNO3P requires 538.2278.
To 2.4 g (6.2 mmol) of phosphinic ester 2 (Y EtO,
Q NPh) in 50 ml of dry chloroform was added 1.9 g
(9.0 mmol) of phosphorus pentachloride, and the
mixture was stirred at the boiling point for 5 days.
The solvent and the volatile components were re-
moved in vacuo to leave a mixture of phosphinic
chlorides 10A and 10B in quantitative yields suit-
able for further transformation [31P NMR (CDCl3) δ
57.2 (72%) for 10A and δ 57.1 (28%) for 10B; MS,
m/z 369 (M+)].
General Procedure for the Phosphorylation
of Methanol Using Precursors 7, 9a, 9d, and 9c
The solution of 0.240 mmol of the phosphabicy-
clooctene (7, 9a, 9d, or 9c,) consisting of isomers,
in 45 ml of acetonitrile and 4 ml of methanol was
irradiated in a photochemical reactor with a mercury
lamp (125 W) for the appropriate time (see below).
Volatile components were removed, and the residue
so obtained was purified by flash column chromato-
graphy (silica gel, 3% methanol in chloroform) to af-
ford the respective phosphinates (13a, 13d, and 13c)
alone or along with unreacted starting material.
To ∼2.3 g (∼6.2 mmol) of phosphinic chloride
10 in 40 ml of degassed benzene was added 2.3 ml
(28 mmol) of pyridine and 1.2 ml (11.9 mmol) of