314 Nycz and Musiol
for the derivatives substituted with the alkyl and/or
aryl groups. The alkoxy group as a phosphorus sub-
stituent decreases the efficiency because the iodine
anion can also react with such substituents. The
method presented is a convenient and easy way to
control general synthesis procedure yielding diphos-
phine dioxides and hypophosphoric acid esters. The
surprising results suggest that the reaction proceeds
via radical mechanism rather than a pure nucle-
ophilic substitution.
According to Quin and Anderson [6a] we sug-
gest that >P–O− anion reacts with >P(O)X (X = Cl,
Br) electrophiles to produce >P(O)–(O)P<, as well
>P(O)–O–P< mixed anhydride, which is a key in-
termediate in the origin of >P(O)–O–(O)P< side-
product. The >P–O− anion selectively reacts with
mixed anhydrides >P(O)–O–P< to produce acid an-
ion >P(O)–O−, which reacts further with >P(O)X
giving >P(O)–O–(O)P< anhydride.
was stirred until the disappearance of the blue color.
Thus, the generated 2a (2b) (5 mmol) at −78◦C was
added to the solution of 4a,b (4c) (5 mmol) in THF
(20 mL), respectively. After 3 h at −78◦C, a sam-
ple of the reaction mixture was taken, C6D6 was
added, and the 31P NMR spectrum was recorded. The
31P NMR (THF/C6D6) spectrum of the reaction mix-
ture showed two resonance lines attributable to the
potassium salt of t-butylphenylphosphinic acid an-
ion (6b) (δ31P = 31.95) and diphosphine monoxides
(6b (δ31P = 35.82) and 5,5,5ꢁ,5ꢁ-tetramethyl-2,2ꢁ-oxy-
bis[1,3,2]dioxaphosphinane (8) (δ31P = 110.36)), re-
spectively. The 31P NMR spectra shows two groups
of signals of 1,2-di-t-butyl-1,2-diphenyldiphosphane
monoxides (7a,b) [13], for the rac and the meso iso-
mers (in a 1:4 ratio) (7a .ꢁPIII = –12.61, δPV = 50.57,
JP−P = 277.16 Hz, and 7b δPIII = –4.66, δPV = 56.04,
JP−P = 285.47 Hz). Sulfur in benzene (run 1), dry air
(run 2), or toluene and a water solution of KHSO4
(run 3) were added to the reaction mixture, respec-
tively. After 16 h, toluene/KHSO4 water solution was
added, (runs 1 and 2). The organic phase was sepa-
rated and dried (MgSO4). Then, the solvent was evap-
orated and the residue was purified by crystallization
and chromatography.
EXPERIMENTAL
All reactions were carried out under argon atmo-
sphere in anhydrous solvents (benzene, diethyl ether,
and THF dried over benzophenone ketyl, MeOH
dried over Mg, CHCl3 dried over P2O5, hexane dried
over potassium). Chromatography was carried out
on silica gel 60 (0.15–0.3 mm) Machery Nagel. NMR
measurements were performed on Varian Gemini
500 MHz or 200 MHz (all J values are given in Hz, the
chemical shifts are expressed as δ values (ppm)); MS
were acquired on a MASPEC II system [II32/99D9]
in EI mode and if necessary liquid SIMS technique
was applied. Compounds 4a,b as a meso and rac iso-
mers [12] were synthesized according to procedures
described in the literature.
Run 1: Sulfur Addition. t-Butylphenylphos-
phinic acid 6a: 0.940 g (4.7 mmol, 95%), mp = 155–
1
3
156◦C; H NMR (CDCl3) δ = 0.93 (d, JP−H = 15 Hz,
t-Bu, 9H), 6.93–7.57 (m, aromatic, 5H), 11.0 (s, OH,
1H), 31P NMR (CDCl3) δ = 52.00.
1,2-di-t-Butyl-1,2-diphenyldiphosphane P1-Oxide
P 2-Sulfide 9a,b: 9a (CHCl3) 1.189 g (3.1 mmol,
60%), mp = 174–176◦C, 1H NMR (CDCl3) δ = 0.94 (d,
3 JP(O)H = 18 Hz, t-Bu, 9H) 1.09 (d, 3 JP(S)H = 16 Hz, t-Bu,
9H), 7.27–8.74 (m, aromatic, 10H), 31P NMR (CDCl3)
δP(S) = 43.40, δP(O) = 41.11, JP−P = 52.40 Hz, MS :
(SIMS) M+ 378, HRMS: m/z Calcd for C20H28OP2S
(M+): 378.13350. Found 378.13454. 9b: (CHCl3)
Synthesis of t-Butylphenylphosphinic-5,5-di-
metyl-(1,3,2)-dioxaphosphinan Anhydride 4c
0.105 g (0.3 mmol, 6%), mp = 136–137◦C, H NMR
1
4
3
Compound 4c was prepared similarly to 4a,b
[12]; 31P NMR (THF/C6D6) δPIII = 108.59, δPV = 43.29,
2 JP−P = 26.29 Hz.
(CDCl3) δ = 1.47 (dd, JP(S)H = 1 Hz, JP(O)H = 16 Hz,
4
3
t-Bu, 9H) 1.39 (dd, JP(O)H = 1 Hz, JP(S)H = 15 Hz,
t-Bu, 9H), 7.07–7.66 (m, aromatic, 10H), 31P NMR
(CDCl3) δP(S) = 54.96, δP(O) = 53.37, JP−P = 52.40 Hz,
MS : (SIMS) M+ 378.
Reaction of Potassium Salt of t-Butylphenyl-
phosphine Oxide 2a (potassium Salt of 5,5-Di-
methyl-(1,3,2)-dioxaphosphinane-2-oxide 2b)
with t-Butylphenylphosphine t-Butylphenylphos-
phinic Anhydride (4a,b or 4c), respectively
Run 2: Dry Air. 6a 0.931g (4.7 mmol, 94%). 1,2-
di-t-Butyl-1,2-diphenyldiphosphane 1,2-Dioxide 3a,b
(mixture of meso and rac) [4,14]. 3a: (CHCl3:
MeOH = 50 : 1) 1.593 g (4.4 mmol, 88%), mpmeso
=
3
In the freshly prepared potassium naphthalenide in
25 mL of THF at −78◦C, t-butylphenylphosphinic
acid chloride (1a) (2-chloro-5,5-dimethyl-(1,3,2)-
dioxaphosphinane-2-oxide 1b) (5 mmol) in THF (5
mL) was added, respectively. The reaction mixture
205◦C, 1H NMR (CDCl3) δmeso = 0.98 (d, JP−H = 16
Hz, t-Bu, 18H), 7.40–8.45 (m, aromatic, 10H),
31P NMR (CDCl3) δmeso = 39.8, MS : (SIMS) M+
362. 3b: mprac = 192–193◦C, 1H NMR (CDCl3)
3
δrac = 1.38 (d, JP−H = 17Hz, t-Bu, 18H), 7.00-7.80
Heteroatom Chemistry DOI 10.1002/hc