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Ovakimyan et al.
cal parameters are consistent with the data published in the
literature.
The reaction of salt 5 with a methanolic solution of
sodium methoxide afforded triphenylphosphine oxide and
O,Pꢀbetaine 6 (Scheme 4).
Triphenyl(2ꢀphenylhydrazinoethyl)phosphonium bromide (3).
A. Phenylhydrazine (2.8 g, 2.6 mmol) was added to a solution
of (2ꢀphenoxyethyl)triphenylphosphonium bromide (1) (6 g,
13 mmol) in MeOH (40 mL) and the reaction mixture was kept
at ∼20 °C for 3 days. The solvent was distilled off and the dry
residue was thoroughly washed with dry ether. The ethereal
extracts were combined and the ether was distilled off. Distillaꢀ
tion of the residue afforded the phenol with the b.p. 70 °C
(10 Torr) in a yield of 1 g (81%). The residue obtained after
washing with ether was dried and recrystallized from an ethyl
acetate—ethanol mixture to obtain salt 3 in a yield of 4.8 g
(76.9%), m.p. 218 °C. Found (%): Br, 16.10. C26H26BrN2P.
Calculated (%): Br, 16.77. 1H NMR, δ: 3.28 (dt, 2 H, NCH2,
Scheme 4
3JP,H = 11.1 Hz, 3JH,H = 7.0 Hz); 4.04 (dt, 2 H, PCH2, 2JP,H
=
The formation of betaine structure 6 is supported
both by the fact that the 31P NMR spectrum has a signal
in the region (δ +33.5) characteristic of triphenylphosphoꢀ
nium salts as well as by the upfield shifts of the signals
12.9 Hz, 3JH,H = 7.0 Hz); 6.63 (t, 1 H, pꢀPhN, 3JH,H = 7.2 Hz);
3
6.79 (d, 2 H, oꢀPhN, JH,H = 8.1 Hz); 7.01 (dd, 2 H, mꢀPh);
7.56—7.78 (m, 15 H, Ph3P). 13C NMR, δ: 22.22 (d, PCH2,
1J = 49.4 Hz); 44.64 (CH2N); 149.28 (ipsoꢀNPh); 128.67 and
113.27 (oꢀ and mꢀNPh); 118.37 (pꢀNPh); 118.41 (d, ipsoꢀPPh,
1
for the methylene protons in the H NMR spectrum of
compound 6 compared to those observed in the specꢀ
trum of the starting salt 5.
Phosphobetaine 6 readily reacted with iodomethane
to give the corresponding phosphonium salt 7 (Scheme 5)
whose 1H NMR spectrum has a signal at δ 3.4 characterꢀ
istic of the methoxy group.
1JP,C = 86.0 Hz); 130.32, 133.99 (d, oꢀ and mꢀPPh, JP,C
12.8 Hz, JP,C = 9.8 Hz); 134.82 (pꢀPPh).
=
B. Triethylamine (0.8 g, 8 mmol) was added to a mixture of
1,2ꢀbis(triphenylphosphonium)ethane dibromide (2) (6 g,
8 mmol) and phenylhydrazine (1.6 g, 16 mmol) in MeOH
(30 mL) and the reaction mixture was kept at ∼20 °C for 24 h.
The solvent was distilled off and the residue was thoroughly
washed with dry ether. After the removal of the ether from
the combined ethereal extracts, triphenylphosphine (m.p.
78—82 °C) was isolated in a yield of 1.8 g (85%). A mixture
with an authentic sample showed no melting point depression.
The residue was washed with ether and dried in vacuo. After
recrystallization from an ethyl acetate—ethanol mixture, salt 3
was obtained in a yield of 3.4 g (87.5%). Its physicochemical
constants were identical with those described above.
Scheme 5
Reaction of salt 3 with sodium hydroxide. A 25% aqueous
solution of NaOH was added to a solution of salt 3 (2.5 g,
5 mmol) in benzene (0.3 g, 7 mmol). The reaction mixture was
kept at ∼20 °C for 3 days. The benzene solution was decanted.
The residue was twice washed with benzene and dried to obtain
unconsumed starting salt 3 in a yield of 1 g (40%). A mixture of
the cis and trans isomers of phenylhydrazone 4 was isolated
from the combined benzene solutions in a yield of 0.9 g (54%),
m.p. 193—194 °C. Found (%): C, 72.2; H, 6.02. C20H19N2OP.
Apparently, triphenylphosphine oxide in this reacꢀ
tion was produced according to a scheme involving synꢀ
chronous cyclization—cleavage of intermediate phosꢀ
phorane 8 (Scheme 6).
Scheme 6
Calculated (%): C, 71.85; H, 5.68. 1H NMR, δ: 3.44 and 3.49
1
(both t, 1 H each, PCH2, JP,C
=
2JH,H = 6.2 Hz); 6.51 (q,
0.5 H, =CH, 3JH,H = 3JH,H = 6.2 Hz); 6.79—6.89 and 7.10—7.32
(both m, 5.5 H, NPh, 0.5 H, =CH); 7.54—7.81 (m, 10 H,
PPh2). 31P NMR, δ: 32.75, 30.91.
(2ꢀHydroxyaminoethyl)triphenylphosphonium bromide (5).
Triethylamine (3 g, 0.03 mol) was added to a mixture of
1,2ꢀbis(triphenylphosphonium)ethane dibromide (2) (7.1 g,
0.01 mol) and hydroxylamine hydrochloride (0.7 g, 0.01 mol)
in CHCl3 (40 mL). The reaction mixture was refluxed for 13 h
and then water (10 mL) was added. The organic layer was
separated and dried over MgSO4. After the removal of CHCl3,
the residue was washed with ether and ethyl acetate. Triphenylꢀ
phosphine was isolated from the combined extracts in a yield of
1.9 g (72%) (m.p. 78—80 °C). A mixture with an authentic
sample showed no melting point depression. The residue was
Experimental
The 1H, 13C, and 31P NMR spectra were recorded on a
Mercuryꢀ300 Varian spectrometer (300 MHz) in CDCl3. Crysꢀ
tals of compound 3 suitable for Xꢀray diffraction analysis were
prepared by slow evaporation of a solution of 3 in an ethyl
acetate—ethanol mixture. The starting salts 1 and 2 were synꢀ
thesized according to known procedures.2,3 Their physicochemiꢀ
Ovakimyan
