Reactions of 1,2-imino alcohols with phosphoromonochloridites: Formation of 2-iminoalkyl(phenyl) phosphites

Article abstract of DOI:10.1023/B:RUGC.0000045871.34621.83

1,2-Imino alcohols existing in a tautomeric equilibrium with the corresponding 1,3-oxazolidines react with phosphoromonochloridites in ether in the presence of triethylamine to form 2-iminoalkyl(phenyl) phosphites as the only reaction products.

Full text of DOI:10.1023/B:RUGC.0000045871.34621.83

Russian Journal of General Chemistry, Vol. 74, No. 7, 2004, pp. 1097 1100. Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 7, 2004,
pp. 1187 1190.
Original Russian Text Copyright
2004 by Dimukhametov, Bayandina, Davydova, Al’fonsov.
Reactions of 1,2-Imino Alcohols with Phosphoromonochloridites:
Formation of 2-Iminoalkyl(phenyl) phosphites
M. N. Dimukhametov, E. V. Bayandina, E. Yu. Davydova, and V. A. Al’fonsov
Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Center,
Russian Academy of Sciences, Kazan, Tatarstan, Russia
Received July 22, 2002
Abstract 1,2-Imino alcohols existing in a tautomeric equilibrium with the corresponding 1,3-oxazolidines
react with phosphoromonochloridites in ether in the presence of triethylamine to form 2-iminoalkyl(phenyl)
phosphites as the only reaction products.
Phosphorylation of imino alcohols with Hal P(III)
derivatives is studied insufficiently. Published data
[1 4] deal with the phosphorylation of imino phenols
with P(III) acid chlorides. It was shown that P(III)
imino derivatives primarily formed in these reactions
in the presence of organic bases undergo further
transformations to give polycyclic phosphoranes as
the final products. In the previous paper we reported
that phosphorochloridites react with aliphatic 1,2-imino
alcohols in the presence of triethylamine to form
-imino phosphites, which under the action of acetic
acid readily cyclize to 1,4,2-oxazaphosphorines [5].
These compounds are the only products when these
reactions are carried out without introducing addi-
tional bases [6, 7]. Imino phosphites stable under the
common conditions were recently obtained by alco-
holysis of amido esters of P(III) acids with 1,2-imino
alcohols [8]. It should be noted that none of the cited
works gave due attention to the well-known fact of
the existence of imino alcohols, especially 1,2-imino
alcohols, as an equilibrium mixture of two tautomers
having the open-chain and cyclic (1,3-oxazolidine)
structures [9, 10]. In this connection, the probability
of the reaction of 1,2-imino alcohols with P(III)
halides along at least two pathways with the forma-
tion of several reaction products cannot be ruled out.
In this work we studied the reaction of some
1,2-imino alcohols with phosphoromonochloridites in
the presence of triethylamine.
1,2-Imino alcohols Ia Ic were prepared by the re-
action of 1,2-amino alcohols with benzaldehyde in
refluxing benzene with the removal of the released
water using a Dean Stark trap. The physicochemical
constants of Ia Ic were close to the published data
(see Experimental).
OH
OH
O
H
X
Y
X
Y
X
Y
+ PhCH=O
NH2
H2O
Ph
N
H
N=CHPh
Ia Ic
I a I c
X
Y
=
(a),
(b),
(c).
\
\
\
Et \
1
The H NMR spectra of all imino alcohols Ia Ic in
CDCl3 contain a strong singlet at 8 ppm correspond-
ing to the HC=N proton of the open-chain tautomer.
At the same time, in the spectra of imino alcohols Ia
and Ib, weaker signals were observed in the range
5 6 ppm; similarly to [9], these signals can be as-
signed to the proton at C2 in 1,3-oxazolidines I a and
I b. This proton in I a gives one singlet, and in I b,
two singlets in approximately 2:1 ratio. In the latter
case, the splitting is caused by the existence of
1070-3632/04/7407-1097 2004 MAIK Nauka/Interperiodica

1098
DIMUKHAMETOV et al.
1,3-oxazolidine I b as a mixture of diastereomers
(cis/trans isomers). The ratio of the tautomers found
from the integral intensity of the signals of the indi-
cator protons of the two tautomeric forms is as
follows: Ia/I a 10:1, Ib/I b 5.5:1.
philicity of the phenolic OH group as compared to
hydroxy group of aliphatic alcohols, which prevents
the intramolecular nucleophilic attack of the hydroxy
group of 1,2-imino alcohol at the imine carbon atom.
Available data indicate that, on introduction of the
electron-accepting CF3 group to the imine carbon
atom, the attack of phenolic hydroxy group at the
electrophilic imine carbon atom becomes possible.
The corresponding aromatic 1,2-imino alcohol in the
crystal has the 1,3-oxazolidine structure [11].
In the expected range of the NMR spectrum of 1,2-
imino alcohol Ic, no signals of the protons of the
cyclic tautomer I c were observed. This fact shows
that 2-(N-benzylidenamino)phenol Ic under the
common conditions in chloroform exists as an open-
chain tautomer. In other words, the amount of 1,3-
oxazolidine I c in so small that it cannot be detected
by NMR spectroscopy. Formation of cyclic tautomer
in this case is evidently prevented by the strain
appearing in the five-membered ring annelated with
the aromatic ring. Another possible reason of the
Reactions of imino alcohols Ia Ic with phosphoro-
monochloridites were carried out in anhydrous ether
or benzene in the presence of triethylamine. The 31P
NMR spectra of all the crude products contain a
singlet at 128 140 ppm, i.e., in the range typical of
absence of the cyclic tautomer is the decreased nucleo- neutral phosphites.
OP(OR)2
(RO)2PCl, Et3N
X
I a I c
Ia Ic
Et3N HCl
Y
N=CHPh
II IX
O
O
X
Y
X
Y
, R = Et (II), OCH2CH2Cl (IV); (RO)2 =
(III),
=
Et \
, R = Et (V); (RO)2 =
(VI).
=
\
\
\
O
O
O
X
Y
(VIII).
, R = Et (VII), OCH2CH2Cl (IX); (RO)2 =
=
O
The reaction products were purified by distillation
at reduced pressure. In some cases, after filtering off
triethylamine hydrochloride and removing the solvent,
keeping the crude products in a vacuum was sufficient.
The isolated 2-iminoalkenyl(phenyl) phosphites II IX
are either low-viscous colorless liquids (II VI) or
light yellow oils (VII IX). Their purity and structures
which exist in a dynamic tautomeric equilibrium with
1,3-oxazolidines I a I v, is evidently caused by the
fact that the OH group in Ia Ic is much more reac-
tive than the NH group in I a I c, and, as the imino
alcohols are consumed, the balance Ia Ic
I a I c
shifts to the left until the cyclic tautomer fully dis-
appears. In this connection, it should be noted that
phosphorochloridites as electrophilic reagents relative
to imino alcohols differ from such electrophiles as
isocyanates. Witek et al. [12] have shown that 1,2-
imino alcohols obtained from ethanolamine and para-
substituted benzaldehydes react with isocyanates to
form only the 1,3-oxazolidine derivatives.
1
were confirmed by H and 31P NMR spectra and also
by IR spectroscopy and elemental analysis. The 31P
{1H} NMR spectra of the distilled products contained
the singlets in the same range as the spectra of the
crude reaction mixture. The 1H NMR spectra in
CDCl3 contained the characteristic singlet of the
HC=N proton at 8 ppm. The presence of the free
imino group was confirmed by the medium-intensity
1
IR absorption band at 1640 1650 cm .
Thus, 1,2-imino alcohols react with phosphoro-
monochloridites in the presence of an organic base
similarly to the usual alcohols to form 2-iminoalkyl-
(phenyl) phosphites.
Formation of 2-iminoalkyl(phenyl) phosphites
II IX as the only products in the reaction of phos-
phoromonochloridites with imino alcohols Ia Ic,
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 74 No. 7 2004

REACTIONS OF 1,2-IMINO ALCOHOLS WITH PHOSPHOROMONOCHLORIDITES
1099
EXPERIMENTAL
phosphite IV was prepared similarly to II from
3.57 g of 2-(benzylidenamino)ethanol Ia, 2.42 g of
triethylamine, and 5.40 g of bis(2-chloroethyl) phos-
phorochloridite. Yield 6.87 g (88%), bp 195 197 C
The H NMR spectra of I IX and 31P {1H} NMR
spectra of compounds II IX in CDCl3 were recorded
on Bruker WM-250 (250 MHz, chemical shifts
measured relative to residual solvent protons) and
Bruker CXP-100 (36.49 MHz, chemical shifts
measured relative to external 85% H3PO4) spectrom-
eters, respectively. The IR spectra (thin layer for Ia,
Ib, and II IX; mull in mineral oil for Ic) were ob-
tained on a UR-20 spectrometer. The optical rotation
was measured on a Polamat A polarimeter.
1
(0.4 mm), n2D0 1.5285. IR spectrum, , cm : 1650
1
1
(C=N), 1228, 1075 (P O C). H NMR spectrum, ,
ppm: 3.41 4.01 m (12H, 3CH2CH2), 7.16 7.79 m
(5H, C6H5), 8.12 s (1H, HC=N). 31P NMR spectrum,
P, ppm: 140.8 s. Found, %: C 46.37; H 5.65; Cl
20.79; N 3.86; P 8.92. C13H18Cl2NO3P. Calculated,
%: C 46.15; H 5.33; Cl 21.00; N 4.14; P 9.17.
2-(R)-(N-Benzyliden)aminobutyl diethyl phos-
phite V. A solution of 0.70 g of diethyl phosphoro-
chloridite was added dropwise with stirring at +5 C
undr argon to a solution of 0.81 g of R-(+)-2-(benzyl-
idenamino)butanol Ib and 0.46 g of triethyl-
amine in 30 ml of absolute benzene,. After the addi-
tion of the phosphorochloridite was complete, the
mixture was kept for 1.5 h at room temperature. The
precipitate of triethylamine hydrochloride was filtered
off, the solvent was removed at reduced pressure, and
the product was dried in a vacuum (1 mm, 50 C) for
0.5 h. Yield 1.15 g (88%), n2D0 1.5148. IR spectrum, ,
The 1,2-imino alcohols Ia Ic obtained had the
following physicochemical constants. 2-(Benzyliden-
amino)ethanol Ia: bp 94 96 C (0.05 mm), nD20
1.5725 (published data: bp 135 136.5 C (15 mm)
[12]). R-(+)-2-(Benzylidenamino)butan-1-ol Ib was
prepared from R-( )-2-aminobutanol with [ ]2D0 7.01
(pure liquid); bp 73 C (0.06) mm, mp 54 55 C, [ ]D20
+28.0 (c 13.2, MeOH) (published data: bp 55 56 C,
[ ]2D0 +39.30 [13]). 2-(Benzylidenamino)phenol Ic:
mp 94 C (from benzene); published data: mp 95 C
[14]).
1
1
cm : 1645 (C=N), 1045 (P O C). H NMR spec-
trum, , ppm: 0.82 t (3H, CH3CH2CH, JHH 7.5 Hz),
1.24 t (6H, 2CH3CH2O, JHH 7 Hz), 1.57 m (2H,
CH3CH2CH), 3.22 m (1H, CH3CH2CH), 3.60 4.10 m
(6H, 2CH3CH2, NCHCH2), 7.10 7.70 m (5H, C6H5),
8.12 s (1H, HC=N). 31P NMR spectrum, P, ppm:
138.9 s. Found, %: C 60.97; H 8.42; N 5.20; P 10.60.
C15H24NO3P. Calculated, %: C 60.61; H 8.08; N 4.71;
P 10.44.
2-(Benzylidenamino)ethyl diethyl phosphite
II. A solution of 1.80 g of diethyl phosphorochloridite
was added dropwise at +5 C under dry argon to a
solution of 1.71 g of 2-(benzylidenamino)ethanol Ia
and 1.20 g of triethylamine in 30 ml of absolute ether.
After the addition was complete, the mixture was kept
at room temperature for 1.5 h. The precipitate of tri-
ethylamine hydrochloride was filtered off, and the
solvent was removed in a vacuum. Phosphite II was
isolated pure by vacuum distillation. Yield 2.66 g
(86%), bp 119 121 C (0.25 mm), n2D0 1.5148. IR
spectrum, , cm : 1648 (C=N), 1029 (P O C). H
NMR spectrum, , ppm: 1.06 t (6H, 2CH3, JHH 7 Hz),
3.67 3.96 m (8H, 4CH2), 7.15 7.71 m (5H, C6H5),
8.13 s (1H, HC=N). 31P NMR spectrum, P, ppm:
140.1 s. Found, %: C 58.25; H 7.22; N 4.81; P 11.29.
C13H20NO3P. Calculated, %: C 57.99; H 7.43; N 5.20;
P 11.52.
[2-(R)-(Benzylidenamino)butyl]ethylene
phite VI was prepared similarly to II from 2.70 g of
R-(+)-2-(benzylidenamino)butanol Ib, 1.54 of
phos-
1
1
g
triethylamine, and 1.93 g of ethylene phosphorochlo-
ridite. Yield 3.20 g (80%), bp 163 165 C (0.4 mm),
1
n2D0 1.5386. IR spectrum, , cm : 1645 (C=N), 1015,
1
1048 (P O C). H NMR spectrum, , ppm: 0.88 t
3
(3H, CH3, JHH 7.5 Hz), 1.65 m (2H, CH3CH2),
3.22 m (1H, CH2CHN), 3.93 m (4H, OCH2CH2O),
4.11 m (2H, OCH2CH), 7.40 7.78 (5H, C6H5), 8.26 s
(1H, HC=N). 31P NMR spectrum, P, ppm: 135.2 s.
Found, %: C 57.97; H 6.42; N 5.20; P 11.50.
C13H18NO3P. Calculated, %: C 58.43; H 6.74; N 5.24;
P 11.61.
2-(Benzylidenamino)ethyl ethylene phosphite III
was prepared similarly to II from 4.12 g of 2-(benzyl-
idenamino)ethanol Ia, 2.79 g of triethylamine, and
3.50 g of ethylene phosphorochloridite. Yield 6.21 g
(94%), bp 140 141 C (0.4 mm), n2D0 1.5570. IR
1
spectrum, , cm : 1647 (C=N), 1018, 1045 (P O C).
1H NMR spectrum, , ppm: 3.80 4.21 m (8H,
2CH2CH2), 7.24 7.84 m (5H, C6H5), 8.22 s (1H,
2-(Benzylidenamino)phenyl diethyl phosphite
VII was prepared similarly to V from 1.13 g of 2-
(benzylidenamino)phenol Ic, 0.58 g of triethylamine,
and 0.90 g of diethyl phosphorochloridite. Yield
HC=N). 31P NMR spectrum, P, ppm: 135.8 s. Found,
%: C 54.91; H 6.16; N 5.55; P 13.25. C11H14NO3P.
Calculated, %: C 55.23; H 5.86; N 5.86; P 12.97.
1
1.70 g (93%), n2D0 1.5912. IR spectrum, , cm : 1628
1
(C=N), 1025 (P O C). H NMR spectrum, , ppm:
2-(Benzylidenamino)ethyl bis(2-chloroethyl)
1.28 t (6H, 3CH3, JHH 7 Hz), 4.06 m (4H, 2CH2),
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 74 No. 7 2004

1100
DIMUKHAMETOV et al.
6.80 7.35 m (4H, C6H4), 7.45 7.93 m (5H, C6H5),
3. Schmidpeter, A. and Weinmaier, J.H., Chem. Ber.,
8.48 s (1H, HC=N). 31P NMR spectrum, P, ppm:
133.1 s. Found, %: C 64.10; H 6.50; N 4.63; P 9.97.
C17H20NO3P. Calculated, %: C 64.35; H 6.32; N 4.42;
P 9.78.
1978, vol. 111, no. 6, p. 2086.
4. Harper, S.D. and Arduengo, A.J., J. Am. Chem. Soc.,
1982, vol. 104, no. 9, p. 2497.
5. Dimukhametov, M.N., Bayandina, E.V., Davydo-
va, E.Yu., and Al’fonsov, V.A., Zh. Obshch. Khim.,
2001, vol. 71, no. 8, p. 1397.
2-(Benzylidenamino)phenyl ethylene phosphite
VIIII was prepared similarly to V from 3.15 g of
2-(benzylidenamino)phenol Ic, 1.61 g of triethylamine,
and 2.02 g of ethylene phosphorochloridite. Yield
6. Dimukhametov, M.N., Bajandina, E.V., Davydo-
va, E.Yu., Dobrynin, A.B., Gubaidullin, A.T., Lit-
vinov, I.A., and Al’fonsov, V.A., Mendeleev Commun.,
2001, no. 5, p. 196.
4.21 g (92%), n2D0 1.6348. IR spectrum, , cm : 1625
1
1
(C=N), 1015 (P O C). H NMR spectrum, , ppm:
3.83 4.26 m (4H, OCH2CH2O), 6.95 7.26 m (4H,
C6H4), 7.36 7.97 m (5H, C6H5), 8.43 s (1H, HC=N).
31P NMR spectrum, P, ppm: 128.8 s. Found, %: C
62.97; H 4.49; N 5.20; P 11.22. C15H14NO3P. Cal-
culated, %: 62.72; H 4.88; N 4.88; P 10.88.
7. Dimukhametov, M.N., Davydova, E.Yu., Bajandi-
na, E.V., Dobrynin, A.V., Litvinov, I.A., and Alfon-
sov, V.A., Mendeleev Commun., 2002, no. 6, p. 222.
8. Gavrilov, K.N., Polosukhin, A.I., Bondarev, O.G.,
Korostylev, A.I., Lyubimov, S.E., Shiryaev, A.A.,
Starikova, Z.A., and Davankov, V.A., Mendeleev
Commun., 2001, no. 1, p. 33.
2-(Benzylidenamino)phenyl
bis(2-chloroethyl)
phosphite IX was prepared similarly to phosphite V
from 3.49 g of 2-(benzylidenamino)phenol Ic, 1.79 g
of triethylamine and 4 g of bis(2-chloroethyl) phos-
phorochloridite. Yield of IX 6.70 g (98%), n2D0 1.5994.
9. Paukstelis, J.V. and Hammaker, R.M., Tetrahedron
Lett., 1968, no. 32, p. 3557.
1
IR spectrum, , cm : 1626 (C=N), 1021, 1074
1
(P O C). H NMR spectrum, , ppm: 3.60 t (4H,
10. Paukstelis, J.V. and Lambing, L.L., Tetrahedron Lett.,
2ClCH2, JHH 6.0 Hz), 4.17 m (4H, 2OCH2), 6.80
7.24 m (4H, C6H4), 7.42 7.87 m (5H, C6H5), 8.41 s
1970, no. 5, p. 299.
(1H, HC=N). 31P NMR spectrum, P, ppm: 132.6 s.
Found, %: C 52.61; H 4.91; Cl 18.78; N 3.42; P 7.75.
C17H18Cl2NO3P. Calculated, %: C 52.85; H 4.66; Cl
18.39; N 3.63; P 8.03.
11. Bouillon, J.P., Wynants, C., Janousek, Z., Viehe, H.G.,
Tinant, B., Feneau-Dupont, J., and Declerc, J.P., Bull.
Soc. Chim. Belg., 1994, vol. 103, no. 2, p. 243.
12. Witek, S., Bielawska, A., and Bielawski, J., Polish J.
Chem., 1981, vol. 55, no. 10, p. 2025.
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13. Kumar, G.B. and Shah, A.C., Indian J. Chem. (B),
1. Schmidpeter, A. and Weinmaier, J.H., Angew. Chem.,
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1996, vol. 35, no. 1, p. 79.
2. Schmidpeter, A. and Weinmaier, J.H., Angew. Chem.,
1977, vol. 89, no. 12, p. 903.
14. Beilsteins Handbuch der organischen Chemie,
vol. XIII, p. 368.
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