Sigmatropic isomerizations in azaallyl systems: XX. N- Alkylbenzimidoylphosphonates

Article abstract of DOI:10.1007/s11176-005-0007-6

Synthetic approaches are developed to benzimidoylphosphoryl derivatives containing electronically and sterically diverse alkyl substituents on the nitrogen atom, as well as their prototropic isomers. Regularities in prototropic transitions in the phosphorylated C=N-C triad were revealed and applied in the synthesis of α-aminophosphonic acid derivatives. 2004 MAIK "Nauka/Interperiodica".

Full text of DOI:10.1007/s11176-005-0007-6

Russian Journal of General Chemistry, Vol. 74, No. 9, 2004, pp. 1341 1349. Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 9, 2004,
pp. 1447 1455.
Original Russian Text Copyright
2004 by Onys’ko, Kim, Rassukanaya, Kiseleva, Sinitsa.
Sigmatropic Isomerizations in Azaallyl Systems:
XX1. N-Alkylbenzimidoylphosphonates
P. P. Onys’ko, T. V. Kim, Yu. V. Rassukanaya, E. I. Kiseleva, and A. D. Sinitsa
Institute of Organic Chemistry, National Academy of Sciences of Ukraine, Kiev, Ukraine
Received November 26, 2002
Abstract Synthetic approaches are developed to benzimidoylphosphoryl derivatives containing electroni-
cally and sterically diverse alkyl substituents on the nitrogen atom, as well as their prototropic isomers.
Regularities in prototropic transitions in the phosphorylated C=N C triad were revealed and applied in the
synthesis of -aminophosphonic acid derivatives.
Imidoylphosphonates containing -hydrogen atoms
in the N-alkyl group are potential 1,3-prototropic
systems. Prototropy the phosphorylated C=N C
1,3-prototropic triad presents both theoretical and
Scheme 1.
P
P
practical interest. The A
be regarded as a phosphorus model of the bio-
chemical transamination reaction in living bodies.
B interconversion can
Ar
N
Ar
Ar
N
H
I
II
P =
(RO2)P(O), Ph2P(O), Ph3PCl, (R2N)3PCl; Ar,
Ar = Ph, RC6H4 (R = 4-MeO, 4-Me, 4-F, 3-F, 2-F, 4-Cl,
4-Br, 4-NO2, 3-NO2), 2-furyl, 2-thienyl.
P
P
C
C
N
N
H
we explored the ability to isomerization of benz-
imidoylphosphoryl derivatives with electronically and
sterically diverse substituents in the N-alkyl group.
The benzimidoylphosphoryl compounds were pre-
pared by the reaction of imidoyl chlorides III with
alkoxy derivatives of trivalent phosphorus.
A
B
The 1,3-prototropic shift in the phosphorylated
azaallyl triad makes evident genetic relation between
derivatives of imidoylphosphonic (A) and -amino-
alkylphosphonic acids (B) that attract increased in-
terest in view of their biological activity [2, 3].
Scheme 2.
Transformations like A
B belong to funda-
+
Cl
mental properties of imidoylphosphonates and form
an important method for preparing -aminoalkylphos-
phoryl derivatives [4].
+
Cl
R2POEt
R
R
R
R2POEt (IVa, IVb)
R
Ph
N
R
N
Ph
IIIa IIIe
C
In previous communications of this series we
showed that the phosphorus-containing group controls
facility and direction of prototropic migrations in the
C=N C triad. In detail it was established [4, 5] that
N-benzylbenzimidoylphosphoryl derivatives I under
mild conditions, even in the absence of bases, undergo
an irreversible 1,3-prototropic shift to form N-
benzylidene- -aminoalkylphosphoryl derivatives II
(Scheme 1).
R2P=O
O=PR2
R
R = H, R = CF3
C
N
R
Ph
Ph
N
R
H
VIa VIi
Va Vi
IIIa IIIe, R = R = H (a), Me (b); R = Me, R = Ph (c);
R = H, R = CF3 (d); R = R = CF3 (e). IVa, IVb, R =
EtO (a), Ph (b). V, VI, R = R = H, R = EtO (a); R =
R = Me, R = EtO (b), Ph (c); R = H, R = CF3, R = EtO
(d) [6], Ph (e); R = R = CF3, R = EtO (f), Ph (g); R = Me,
R = Ph, R = EtO (h), Ph (i).
To assess the effect of the N-alkyl substituent on
the prototropy in the C N C triad, in the present work
1
For communication XIX, see [1].
1070-3632/04/7409-1341 2004 MAIK Nauka/Interperiodica

1342
ONYS’KO et al.
It was established that the reaction of imidoyl chlo-
Compounds Vd and Ve were also synthesized in
an alternative way, viz. by phosphorylation of
rides IIIa IIIf with compounds IVa and IVb, ir-
respective of the nature of substituents R and R1 and
of the phosphorus reagent, follows the Arbuzov reac-
tion scheme to give phosphonates or phosphine oxides
V. That means that in this case phosphorylation is not
accompanied by the prototropic rearrangement of
compound V to imines VI. By contrast, N-benz-
imidoyl chlorides III (R = H, R = Ar) under the same
conditions react with phosphite IVa to give a mixture
of prototropic isomers I and II [5], whereas the reac-
tion with phosphinite IVb results in preferential
formation of isomer II [7]. The more complete iso-
merization in the last case is explained by the fact that
1,3-H shift takes place mainly in intermediate C,
because the strongly electron-acceptor phosphonium
group favors proton transfer [4, 5, 7, 8].
-
chlorimine VII [6]. It was found that the soft phos-
phorus nucleophile IV attacks preferentially by a soft
nucleophilic center, the sp2-hybridized imine carbon
atom in VII (Scheme 3). The reaction with triethyl
phosphite leads initially to a mixture of prototropic
isomers Vd and VId. When distilled, isomer VId
undergoes an irreversible 1,3-H shift to form imidoyl-
phosphonate Vd [6]. In the reaction of imine VII with
ethyl diphenylphosphinite, intermediate phosphine
oxide VId (
30 ppm) is formed only in trace
P
amounts (<5%). Here, evidently, isomerization takes
place mainly in quasiphosphonium salt D whose life-
time is sufficient for the D
E 1,3-H transfer to
occur (cf. [7]).
Scheme 3.
EtO+PR2 Cl
Cl
VIa, VIb
CHPh
N
Ph
CF3
CF3
N
VII
D
1,3-H
EtCl
EtO+PR2 Cl
H
O=PR2
Ph
EtCl
1,3-H
Vd, Ve
N
CF3
CF3
N
Ph
R
H
E
VId, VIe
= EtO (d), Ph (e).
Concerted stabilizing effect of the phenyl substi-
tuent at the C=N bond and the electron-acceptor tri-
fluoromethyl group on the Csp atom of the azaallyl
amounts (<5%) of isomer VIa (R = R = H, R = EtO)
2
(
4.9 ppm, d; JHP 18 Hz) and its transformation
CHP
1
3
product could be detected by H NMR.
triad renders isomers Vd and Ve thermodynamically
preferable [4, 9]. It is evident that the presence of two
CF3 groups on the Csp atom should further stabilize
Compounds Vh and Vi contain phenyl substituents
on both carbon atoms of the C=N C triad, and the
position of the prototropic equilibrium is not evident
3
imidoylphosphoryl isomers Vf and Vg. In agreement
with that, heating of compounds Vd Vg in the ab-
sence of base catalyst (at 100 C without solvent or
under reflux in toluene), as well as in the presence of
nitrogenous bases (Et3N, DABCO, and DBU) does
not cause their isomerization to VId VIg. By contrast,
imines VId and VIe slowly isomerize to Vd and Ve
even at room temperature. Imidoylphosphonate Va,
the simplest derivative of N-alkylbenzimidoylphos-
phonates, too, is prone to prototropy neither on ther-
molysis (120 C, without solvent) nor under conditions
of base catalysis (EtONa, EtOH, reflux). It is only
after prolonged heating in triethylamine that small
in this case. To find out if the Vh
VIh inter-
conversion is possible, we synthesized independently
imidoyl phosphonate Vh by Scheme 2 and its isomer
VIh, as well as compounds VIj VIu with the phos-
3
phoryl group on Csp , by Scheme 4. Phosphine oxide
VIk was prepared by the reaction of -aminobenzyl-
diphenylphosphine oxide with isobutyraldehyde di-
ethyl acetal (see Experimental). Here, however, phos-
phorotropic isomer IX formed along with compound
VIk
already during synthesis (120 160 C)
(Scheme 6).
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 74 No. 9 2004

SIGMATROPIC ISOMERIZATIONS IN AZAALLYL SYSTEMS: XX.
1343
Scheme 4.
under heating (120 160 C) undergoes phosphorotro-
pic rather than prototropic shift to form imine IX
R
2
3
O=PR2
Ph NH2
R
O=PR2
N
(
3.86 d.d, JCHP 10 Hz, JHH 6 Hz, IX/VIk ratio
1.5:1) whose stabilization is connected with the
CHP
+
O
H O Ph
2
R
presence of a favorable N-benzylidene structure.
Thermal phosphorotropic isomerization in this case is
accompanied by decomposition.
R
VIh, VIj VIu
VIj VIu, R = H; R = i-Pr, R = EtO (j), Ph (k); R = EtO,
R = t-Bu (l) [10], 4-Me2NC6H4 (m), 4-MeOC6H4 (n),
4-HOC6H4 (o), 4-MeC6H4 (p), 2,4,6-Me3C6H2 (q),
4-BrC6H4 (r), 3-NO2C6H4 (s), 4-NO2C6H4 (t) [5],
3-pirydyl (u) [11].
Scheme 6.
O=PPh2
VIk
Ph
N
Pr-i
IX
It occured that prototropic isomers Vh and VIh are
kinetically stable compounds. When heated in the
presence or in the absence of bases (Et3N, DBU) in
toluene under reflux, these compounds do not inter-
convert, whereas under more rigid conditions they de-
compose. Mixing of equimolar amounts of imidoyl-
phosphine oxide VI ( 20.1 ppm) and boron trifluo-
ride etherate in benzPene gives complex VIII (
33.5 ppm) (cf. [10]) with a more electrophilic phosP-
phonium center favoring 1,3-H transfer in the C=N C
triad [4, 5, 7, 8]. However, here, too, no prototropic
shift takes place.
Previously we observed similar reversible iso-
merization in sterically more congested homologs of
compounds VIk and IX [10].
It is important to note that the presence of an
N-benzylidene (N-heterylidene) structure makes iso-
mers VIm VIu with phosphorus on the sp3-carbon
atom thermodynamically more preferred independent-
ly of substituents in the benzene ring, be it electron-
donor (VIm VIp), electron-acceptor (VIr VIt), or
sterically congested ones (VIq).
+
O---BF3
Ph2P
It is significant that isomers V and VI have dif-
ferent spectral parameters and thus can be reliably
identified. The phosphorus signals of imidoyl deri-
vatives V ( 3 7 and 18 22 ppm for R = EtO and
Ph, respectiPvely) undergo a significant downfield
CH3
Ph
Ph
N
VIII
We previously showed [6, 12] that the trifluoro-
methyl analog of benzimidoylphosphonate Vh under
conditions of base catalysis undergo irreversible
stereoselective proton transfer (Scheme 5).
shift in going to imines VI ( 15 21 and 28 32 ppm
P
for R = EtO and Ph, respectively) in which the phos-
phorus group is connected to an sp3-carbon atom. The
vicinal coupling constants of the CHP proton in
imines VI (2JCHP 10 21 Hz) and of the =NCH proton
in their isomers V (4JHP 2 5 Hz) are the most im-
portant parameters for structural identification. The
Scheme 5.
(EtO)2P=O
Ph
H
(EtO)2P=O
chemical shifts of the carbon atoms bound to phos-
1
* N
H
*
phorus in isomers V (
220 Hz) and VI (
168 181 ppm, JCP 115
too, strongly differCPfrom each other.
CP
1
CF3
N
Ph
Me
CF3
69 73 ppm, JCP 75 160 Hz),
Me
Our results were later confirmed by Xiao et al.
[13].
A specific feature of imidoylphosphonates V (R =
EtO) is that they exist as E and Z isomers, the sterical-
ly less congested E isomers being preferred (the E/Z
ratio varies from 20:1 to 1.2:1, see Experimental).
After completion of the reaction of imidoyl chloride
IIId with triethyl phosphite (Scheme 3), the E-Vf/Z-
Vf ratio in the reaction mixture was 1.2:1, and distilla-
tion gave fractions with 5:1 and 2:1 E/Z ratios. The
NMR spectra of the E and Z isomers of (N-hexafluoro-
isopropylbenzimidoyl)phosphonates Vf differ sig-
nificantly.
In view of these data we propose that of the isomer
pairs Vh, Vi and VIh, VIi, -phosphorylated imines
VIh, VIi are thermodynamically preferred, and com-
pounds Vh, Vi do not transform into imines VIh and
VIi because of the high energy barrier. In accordance
with that, the thermodynamically preferred isomers
VIj, VIk or VIl [10] under thermolytic conditions or
in the presence of lithium diisopropylamide do not
undergo prototropic isomerization. Compound VIk
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 74 No. 9 2004

1344
ONYS’KO et al.
The major products of these reactions are phosphite
Scheme 7.
Xa and amides XI. A little phosphorylmethyl phos-
phate XVI was also spectroscopically detected, whose
formation is probably described by Scheme 10.
(EtO)2P=O
O--H
N
CF3
CF3
CF3
(EtO)2P
Ph
N
Ph
H
Scheme 10.
CF3
E-Vf
Z-Vf
6.8 ppm, 4JHP 1.2 Hz
C=N 172.7 ppm,
1JCP 135 Hz
O=P(OEt)2
(EtO)2P(O)H
4
XIV
4.5 ppm, JHP 3 Hz
C=N 181.4 ppm,
1JCP 210 Hz
P(OEt)2
Ph
HO
RR CHNH2
O
XV
O
P 2.0 ppm
P 4.3 ppm
Ph
PR2
We relate the unusually large downfield shift of the
NCH proton in the Z isomer to the anisotropic deshi-
elding effect of the phosphoryl group. The significant
increase in the gap between the NCH proton signals of
the Z and E isomers in going from compounds Va and
Vb ( 0.6 and 0.2 ppm, respectively) to compound
Vf containing the electron-acceptor trifluoromethyl
groups ( 2.3 ppm) suggests hydrogen bonding with
the phosphoryl group in the latter compound.
O
R2P
O
XVIa, R = EtO.
XVIa, R = EtO.
Evidence for the formation of compound XVIa
from hydroxyphosphonate XV has been provided by
Ruel et al. [14].
Imidoylphosphoryl compounds V are liquid (R =
EtO) or solid substances (R = Ph) stable in a dry
atmosphere but hydrolyzed with air moisture with
C P bond cleavage (1H and 31P NMR data).
In agreement with Scheme 10, the reaction of
imidoylphosphonate Va with diethyl hydrogen phos-
phite and water actually leads to phosphorylmethyl
phosphate XVIa.
Scheme 8.
Scheme 11.
R
O
O
H
(H2O)
R22P
+
N
O=P(OEt)2
Me + (EtO)2P
O
H
V
Ph
R
H
+ H2O
H
Ph
N
Xa, Xb
XI
Va
Xa
Xa
X,
R
=
EtO (a), Ph (b); XI,
R = H (a), Me (b).
R
=
Ph,
XIV
XVIa.
The realization of Schemes 10 and 11 also explains
the detection, along with phosphites X and amides XI,
of small amounts of diphosphorylated compounds
XVIa and XVIb (R = Ph) (up to 10%) upon prolon-
ged handling of imidoyl derivatives V. Compounds
XVI are readily identified in the reaction mixture by
the presence of a characteristic PhCHO multiplet in
It is not excluded that the hydrolytic instability of
imidoylphoshonates is one of the reasons for the
failure of their synthesis by condensation of benzoyl-
phosphonates XII with amines XIII (Scheme 9).
Scheme 9.
1
the H NMR spectra and doublet signals of the C
O
R
and O P=O groups (3JPP 25 35 Hz) in the 31P NMR
+
P(OEt)2
Ph
NH2
R
spectra.
H
O
Hence, N-alkylbenzimidoylphosphonates Va Vi
are steady prototropic triad systems. At the same time,
N-benzylbenzimidoylphosphonates are useful starting
materials for preparative synthesis of -aminophos-
phonates XXII and aminophosphonic acids XXIII
[15] because of the high lability of benzyl protons and
XII
XIIIa, XIIIb
(EtO)2P=O R
Xa + XIa, XIb
N
H
Ph
HO
R
XIV
the irreversibility of rearrangements like XX
XXI
(Scheme 12).
XI, XIII, R = Ph, R = H (a), M (b).
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 74 No. 9 2004

SIGMATROPIC ISOMERIZATIONS IN AZAALLYL SYSTEMS: XX.
1345
Scheme 12.
O=P(OEt)2
This method offers advantages over the transforma-
tion of imidoylphosphonates to aminophosphonates,
described in [16, 17], because it permits to avoid
reduction of the azomethine group and deprotection
by hydrogenation.
Cl
(EtO)3P
N
Ph
Ph
R
R
N
XXa XXc
The high lability of phosphorylated prototropic
triad systems like I must be accounted for in synthetic
practice. In this connection we propose that the syn-
thesis of (N-benzyl-4-methoxybenzimidoyl)phos-
phonate XXV (Scheme 13) by a procedure suggesting
stability of this isomer (prolonged heating in the
presence of bases), reported by McKay and Proctor
[18], is contrary to fact. We showed that under the
conditions in [18] not imidoylphosphonate XXV but
its isomeric -phosphorylated benzalimine XXVI is
formed. The latter was identified by a comparison
with the authentic samples synthesized by Schemes 4
[5] or 12.
O=P(OEt)2
NH2
R
O=P(OEt)2
H2O
N
Ph
R
H
H
XXIa XXIc
XXIIa XXIIc
O=P(OH)2
H2O
NH2
XXIIIa XXIIIc
XX XXIII, R = Ph (a), 4-BrC6H4 (b), 4-FC6H4 (c).
R
H
Scheme 13.
O=P(OEt)2
Ph
Ar
N
O=P(OEt)2
O=P(OEt)2
Ar N SO2
TsCl
SO2
Me
Ar
NH2
H
XXIV
Me
Ph
O=P(OEt)2
O=P(OEt)2
MeONa, MeOH
Ph
Ar
Ar
N
N
XXV
XXVI
Ar = 4-MeOC6H4.
The established regularities of prototropic transi-
tions in phosphorylated azaallyl systems containing
aryl and alkyl substituents on the carbon atoms of the
C=N-C triad allow purposeful synthesis of -amino-
phosphonic acid derivatives.
Imidoyl chlorides IIIa and IIIb [19, 20] were
prepared by the reaction of the corresponding amides
PhCONHCHRR with thionyl chloride. Compounds
IIId [6] and IIIe [21] were prepared according to
published procedures.
N-Isopropylbenzylimidoyl chloride (IIIb). Yield
70%, bp 96 102 C (10 mm Hg) {published data [20]:
bp 52 54 C (1 mm Hg)}. 1H NMR spectrum (CDCl3),
, ppm: 1.29 d (6H, Me, JHH 6.3 Hz), 4.17 septet
(1H, CH), 7.34 7.47 m (3H, Ph), 7.97 8.02 m
(2H, Ph).
EXPERIMENTAL
3
The IR spectra were registered on a UR-20 spec-
trometer. The 1H, 19F, 31P, and 13C NMR spectra were
measured on a Varian VXR-300 NMR spectrometer,
working frequences 299.95, 282.20, 121.42, and
75.429 MHz, respectively. The chemical shifts were
N-( -Phenylethyl)benzimidoyl chloride (IIIc). A
measured against internal TMS (1H, 13C), CFCl3 (19F), mixture of 0.004 mol of N-( -phenylethyl)benzamide,
and external 85% phosphoric acid (31P).
0.048 mol of triphenylphosphine, and 0.042 mol of
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 74 No. 9 2004

1346
ONYS’KO et al.
3
4
carbon tetrachloride were refluxed in 30 ml of me-
thylene chloride for 3 h. After cooling, the solvent
was removed in a vacuum, extracted with hexane, and
the residue, a light yellow liquid, was distilled in a
(CHN, JHF 6.6 Hz, JHP 1.2 Hz) (Z), 7.27 7.92 m
(5H, Ph). 13C NMR spectrum (CDCl3), , ppm: 16.1 d
(Me, JCP 6 Hz) (E), 16.3 d (Me, JCP 5 Hz) (Z),
64.4 d (CH2, JCP 5 Hz) (E), 64.0 d (CH2, JCP 7 Hz)
(Z), 64.8 m (CHN, J 30 Hz), 121.2 q (CF3 JCF
3
3
2
2
1
1
vacuum. Yield 40%, bp 132 C (0.08 mm Hg). H
1
NMR spectrum (CDCl3), , ppm: 1.56 d (3H, Me,
283 Hz), 121.7 q (CF3, JCF 284 Hz) (Z), 126.8 130.5
3
3JHH 6.6 Hz), 5.17 q (1H, CH, JHH 6.6 Hz), 7.2
1
(Ph), 181.4 d (C=N, JCP 210 Hz) (E), 172.7 d (C=N,
7.6 m (8H, Ph), 8.01 8.1 m (2H, Ph). Found, %: Cl
14.57; N 5.78. C15H14ClN. Calculated, %: Cl 14.55;
N 5.75.
1JCP 135 Hz) (Z). 19F NMR spectrum (CDCl3)
,
ppm: 70.35 d (3JHF 6.3 Hz) (E), 70.87 d (3JFFH
6.6 Hz (Z). 31P NMR spectrum (CDCl3), , ppm: 6.50
(E), 4.22 (Z), (E/Z 2:1). Found, %: P 8.13.
C14H16F6NO3P. Calculated, %: P 7.92.
Compounds Va Vd and Vf Vi. A mixture of
equimolar amounts of imidoyl chloride and ethyl di-
phenylphosphinite IVb or a 10% excess of triethyl
phosphite IVa was heated until gas evolution began.
The temperature was then raised 20 30 C over the
course of 30 min, and the reaction mixture was kept
for 0.5 h at this temperature. The product was distilled
in a vacuum or crystallized.
1-(Diphenylphosphinoyl)-4,4,4-trifluoro-3-(tri-
fluoromethyl)-1-phenyl-2-azabut-1-ene (Vg). Yield
63%, mp 98 100 C (from petroleum ether). IR spec-
1
1
trum (KBr), , cm : 1240 (P=O), 1630 C=N). H
NMR spectrum (CDCl3), , ppm: 5.57 m (1H, CHN,
3JHF 6 Hz, JHP 2.4 Hz), 7.1 7.9 m (15H, Ph). 19F
4
NMR spectrum (CDCl3), F, ppm: 70.25 d (3JFH
1-(Diethoxyphosphinoyl)-1-phenyl-2-azaprop-1-
ene (Va). Yield 70%, bp 116 1129 C (0.07 mm Hg)
{published data [22]: bp 100 101 C (0.01 mm Hg).
1H NMR spectrum (CDCl3), , ppm: 1.28 t (6H,
MeCH2), 3.34 d [4JHP 4.5 Hz (E)] and 3.93 d [4JHP
1.5 Hz (Z)] (3H, MeN), 4.17 m (4H, OCH2), 7.2
7.5 m (5H, Ph). 13C NMR spectrum (CDCl3), C, ppm:
15.8 (MeCH2), 41.6 d (MeN, 3JCP 33 Hz), 62.7 (CH2),
6 Hz). 31P NMR spectrum (CDCl3), P, ppm: 23.08.
Found, %: P 6.53. C22H16F6NOP. Calculated, %:
P 6.80.
1-(Diethoxyphosphinoyl)-1,3-diphenyl-2-azabut-
1-ene (Vh). Yield 40%, bp 164 165 C (0.06 mm Hg).
1H NMR spectrum (CDCl3), , ppm: 1.22 t (3H,
MeCH2, JHH 7.1 Hz), 1.29 t (3H, MeCH2, JHH
7.1 Hz), 1.44 d (3H, MeCH, JHH 6.4 Hz), 4.0 4.3 m
(4H, CH2O), 4.64 d.q (1H, CHN, JHH 6.5 Hz, JHP
3.2 Hz), 7.2 8.0 m (10H, Ph). 31P NMR spectrum
(PhMe), P, ppm: 7.0. Found, %: N 4.18; P 8.99.
C19H24NO3P. Calculated, %: N 4.07; P 8.97.
3
3
1
126 131 (Ph), 169.3 d (C=N, JCP 220 Hz). 31P NMR
3
spectrum (PhMe), P, ppm: 6.9 (E), 2.3 (Z) (E/Z
3
4
17:1) {published data [22]:
5.9 ppm}.
P
1-(Diethoxyphosphinoyl)-3-methyl-1-phenyl-2-
azabut-1-ene (Vb). Yield 83%, bp 122 124 C
1
(0.05 mm Hg). H NMR spectrum (acetone-d6),
,
1-(Diphenylphosphinoyl)-1,3-diphenyl-2-azabut-
1-ene (Vi). Yield 70%, viscous oil. H NMR spect-
rum (CDCl3), , ppm: 1.38 d (3H, MeCH, JHH
3
1
ppm: 1.03 d (6H, Me2CH, JHH 6 Hz), 1.15 t (6H,
MeCH2, JHH 6.9 Hz), 3.57 m (CHN, JHH 6 Hz, JHP
3
3
4
3
3
4
3.5 Hz) (E), 4.70 m (CHN, JHH 6 Hz, JHP 2 Hz) (Z),
3
4
6.3 Hz), 4.73 d.q (1H, CHN, JHH 6.3 Hz, JHP 2 Hz),
7.2 7.4 m (5H, Ph). 31P NMR spectrum (PhMe)
,
7.0 8.0 m (20H, Ph). 31P NMR spectrum (C6H6),
ppm: 20.1.
,
P
P
ppm: 7.4 (E), 3.2 (Z) (E/Z 15:1). Found, %: P 10.67.
C14H22NO3P. Calculated, %: P 10.93.
1-(Diphenylphosphinoyl)-4,4,4-trifluoro-1-
phenyl-2-azabut-1-ene (Vd). To a solution of
7 mmol of ethyl diphenylphosphinite (IVb) in 4 ml of
benzene, 7 mmol of N-benzylidene-1-chloro-2,2,2-tri-
fluoroethylamine (VII) was added. After 5 days, the
crystals that formed were filtered off and crystallized
from petroleum ether (60 80 C). Yield 70%, mp 121
1-(Diphenylphosphinoyl)-3-methyl-1-phenyl-2-
azabut-1-ene (Vc). Yield 76%, mp 129 130 C (from
1
petroleum ether). H NMR spectrum (acetone-d6), ,
3
ppm: 1.17 d (6H, Me, JHH 6.6 Hz), 3.76 m (1H,
3
4
CHN, JHH 6.6 Hz, JHP 2.1 Hz), 31P NMR spectrum
(acetone-d6), P, ppm: 20.62. Found, %: P 9.01.
C22H22NOP. Calculated, %: P 8.92.
1
123 C. IR spectrum (KBr), , cm : 1285 (P=O),
1
1-(Diethoxyphosphinoyl)-4,4,4-trifluoro-1-
phenyl-3-(trifluoromethyl)-2-azabut-1-ene (Vf).
Yield 82%, bp 104 105 C (0.07 mm Hg). IR spec-
1630 (C=N). H NMR spectrum (acetone-d6 CCl4),
3
4
, ppm: 3.98 d.q (2H, CH2, JHF 9 Hz, JHP 3.5 Hz),
7.1 m (2H, Ph), 7.2 7.4 m (9H, Ph), 7.8 7.9 m (4H,
Ph). 19F NMR spectrum (acetone-d6 CCl4), F, ppm:
1
trum (thin layer), , cm : 1060 (POC), 1290 (P=O),
1
3
1640 (C=N). H NMR spectrum (CDCl3), , ppm:
71.1 t, JFH 9 Hz. 31P NMR spectrum, P, ppm: 20.1
3
1.30 t (6H, Me, JHH 7 Hz), 4.20 m (4H, CH2O),
(C6H6), 18.4 (acetone-d6 CCl4). Found, %: F 14.83;
P 8.05. C21H17F3NOP. Calculated, %: F 14.71; P 8.0.
3
4
4.52 m (CHN, JHF 6.3 Hz, JHP 3 Hz) (E), 6.75 m
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 74 No. 9 2004

SIGMATROPIC ISOMERIZATIONS IN AZAALLYL SYSTEMS: XX.
1347
3
Compounds VIj, VIm, VIn, Vp Vr, and XXVI.
A mixture of equimolar amounts of diethyl ( -amino-
benzyl)phosphonate or ( -aminobenzyl)diphenylphos-
phine oxide and the corresponding aldehyde was
heated at 70 80 C for 3 h and then kept for 0.5 h in
an oil-pump vacuum to remove water. The product
was distilled in a vacuum.
(CDCl3), , ppm: 1.13 t (3H, MeCH2, JHH 7.1 Hz),
3
1.15 t (3H, MeCH2, JHH 7.1 Hz), 2.19 s (3H, 4-Me
C6H2), 2.40 s (6H, 2,6-Me2C6H2), 3.93 m (4H, CH2O),
2
4.82 d (1H, JHP 18.3 Hz, CHP), 6.78 7.57 m (7H,
Ph), 8.68 d (1H, JHP 4.8 Hz, CH=N). 31P NMR spec-
4
trum (CHCl3), P, ppm: 20.14. Found, %: N 3.77; P
8.27. C21H28NO3P. Calculated, %: N 3.75; P 8.29.
1-(Diethoxyphosphinoyl)-4-methyl-1-phenyl-2-
1-(4-Bromophenyl)-3-(diethoxyphosphinoyl)-3-
phenyl-2-azaprop-2-ene (VIr). Yield 79%, bp 199
200 C (0.05 mm Hg), mp 62 84 C. IR spectrum (thin
azapent-2-ene (VIl). Yield 78%, bp 121 132 C
1
(0.07 mm Hg). IR spectrum (CCl4), , cm : 1260
1
1
1
film), , cm : 1262 (P=O), 1638 (C=N). H NMR
(P=O), 1660 (C=N). H NMR spectrum (CDCl3), ,
3
spectrum (acetone-d6), , ppm: 1.17 t (6H, MeCH2),
ppm: 1.07 d (3H, Me2CH JHH 7 Hz), 1.10 d (3H,
2
3
3
4.0 m (4H, CH2O), 5.0 d (1H, CHP, JPH 18.2 Hz),
Me2CH, JHH 7 Hz), 1.18 t (3H, MeCH2, JHH 7 Hz),
3
4
1.21 t (3H, MeCH2, JHH 7 Hz), 2.5 m (1H, CHMe2),
7.3 7.9 m (9H, Ph), 8.52 d (1H, CH=N, JHP 4.5 Hz).
2
4.0 m (4H, CH2O), 4.64 d (1H, CHP, JHP),
31P NMR spectrum (CHCl3), P, ppm: 19.6. Found,
%: N 3.30; P 7.48. C18H21BrNO3P. Calculated, %:
N 3.41; P 7.55.
7.2 7.7 m (6H, Ph, CH=N). 31P NMR spectrum
(CDCl3), P, ppm: 21.24. Found, %: N 4.78; P 10.33.
C15H24NO3P. Calculated, %: N 4.71; P 10.62.
3-(Diethoxyphosphinoyl)-1-(4-hydroxyphenyl)-3-
phenyl-2-azaprop-2-ene (VIo). Equimolar amounts
of diethyl ( -aminobenzyl)phosphonate and 4-hydr-
oxybenzaldehyde were refluxed in benzene with a
Dean Stark trap for 3 h. The benzene was then eva-
porated. The residue was triturated with petroleum
ether until a white powder formed. Yield 66%, mp
3-(Diethoxyphosphinoyl)-1-[4-(dimethylamino)-
phenyl]-3-phenyl-2-azaprop-2-ene (VIm). Yield
71%, bp 200 205 C (0.05 mm Hg). IR spectrum
1
1
(CCl4), , cm : 1258 (P=O), 1640 (C=N). H NMR
3
spectrum (CDCl3), , ppm: 1.10 t (3H, MeCH2 JHH
6.9 Hz), 1.15 t (3H, MeCH2, 3JHH 6.9 Hz), 2.89 s (6H,
2
177 178 C (from benzene). IR spectrum (KBr),
,
Me2N), 3.95 m (4H, CH2O), 4.78 d (1H, CHP, JHP
1
1
cm : 1225 (P=O), 1640 (C=N). H NMR spectrum
18 Hz), 6.58 7.58 m (9H, Ph), 8.27 d (1H, CH=N,
4JHP 4.5 Hz). 31P NMR spectrum (CDCl3), P, ppm:
20.76. Found, %: N 7.51; P 8.40. C20H27N2O3P.
Calculated, %: N 7.48; P 8.27.
3
(CDCl3), , ppm: 1.13 t (3H, MeCH2, JHH 7.1 Hz),
1.17 t (3H, Me2CH2), 3.99 m (4H, CH2O), 4.79 d (1H,
2
CHP, JHP 18 Hz), 8.9 7.9 m (9H, Ph), 8.18 d (1H,
4
CH=N, JHP 4.8 Hz). 31P NMR spectrum (CHCl3),
,
P
3-(Diethoxyphosphinoyl)-1-(4-methoxyphenyl)-
3-phenyl-2-azaprop-2-ene (VIn). Yield 72%, bp
ppm: 20.6. Found, %: N 4.02; P 9.04. C18H22NO4P.
Calculated, %: N 4.03; P 8.92.
180 185 C (0.05 mm Hg). IR spectrum (CCl4),
,
1
1
3-(Diethoxyphosphinoyl)-1-(4-nitrophenyl)-3-
phenyl-2-azaprop-2-ene (VIt) was obtained analo-
gously. Yield 86%, mp 70 71 C {published data [5]:
cm : 1260 (P=O), 1645 (C=N). H NMR spectrum
3
(CDCl3), , ppm: 1.11 t (3H, MeCH2, JHH 7.1 Hz),
3
1.15 t (3H, MeCH2, JHH 7.1 Hz), 3.70 s (3H, OMe),
1
2
mp 66 68 C). H NMR spectrum (CDCl3), , ppm:
3.96 m (4H, CH2O), 4.80 d (1H, CHP, JHP 18 Hz),
3
6.82 7.7 m (9H, Ph), 8.24 d (1H, CH=N, 4JHP 4.5 Hz).
31P NMR spectrum (CDCl3), P, ppm: 20.31. Found,
%: N 3.81; P 8.47. C19H24NO4P. Calculated, %: N
3.88; P 8.57.
1.22 t (3H, MeCH2 JHH 7.1 Hz), 1.23 t (3H, MeCH2,
2JHH 7.1 Hz), 4.03 m (4H, CH2O), 4.99 d (1H, CHP,
2JHP 19.2 Hz), 7.2 8.3 m (9H, Ph), 8.50 d (1H, CH=N,
4JHP 5.1 Hz). 31P NMR spectrum (CDCl3), P, ppm:
19.5. Found, %: P 8.35. C18H21N2O5P. Calculated, %:
P 8.23.
3-(Diethoxyphosphinoyl)-1-(4-methylphenyl)-3-
phenyl-2-azaprop-2-ene (VIp). Yield 78%, bp 200
1
3-(Diethoxyphosphinoyl)-1-(3-nitrophenyl)-3-
phenyl-2-azaprop-2-ene (VIs) was prepared analo-
205 C (0.2 mm Hg). H NMR spectrum (CDCl3), ,
ppm: 1.15 m (6H, MeCH2), 2.32 s (3H, MePh),
2
gously, oil, yield 78%. IR spectrum (thin layer),
,
3.97 m (4H, CH2O), 4.84 d (1H, CHP, JHP 17.7 Hz),
1
1
4
cm : 1252 (P=O), 1646 (C=N). H NMR spectrum
(CDCl3, external HMDS), , ppm: 1.52 t (6H, MeCH2,
3JHH 7.1 Hz), 4.32 m (4H, CH2O), 5.25 d (1H, CHP,
2JHP 18 Hz), 7.6 9.06 m (10H, Ph, CH=N). Found,
%: P 8.23. C18H21N2O5P. Calculated, %: P 8.23.
7.0 7.8 m (9H, Ph), 8.3 d (1H, CH=N, JHP 4.6 Hz).
31P NMR spectrum (benzene), P, ppm: 20.95. Found,
%: P 8.87. C19H24NO3P. Calculated, %: P 8.97.
3-(Diethoxyphosphinoyl)-1-(2,4,6-trimethyl-
phenyl)-3-phenyl-2-azaprop-2-ene-(VIq). Yield 46%,
173 178 C (0.05 mm Hg). IR spectrum (CCl4),
cm : 1260 (P=O), 1638 (C=N). H NMR spectrum
,
Reaction of ( -aminobenzylidene)diphenylphos-
phine oxide with isobutyraldehyde diethyl acetal.
1
1
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 74 No. 9 2004

1348
ONYS’KO et al.
A solution of 0.5 mmol of ( -aminobenzyl)diphenyl-
phosphine oxide in 3 ml of isobutyraldehyde diethyl
acetal was heated for 125 140 C for 3 h. The tem-
perature was raised to 160 C and excess acetal was
removed in a vacuum. The residual light yellow oil
was purified by trituration with petroleum ether. Yield
75%. Characteristic multiplets of CHP protons of
phosphorotropic isomers VIk and IX were identi-
NMR spectrum (CDCl3), , ppm: 1.17 t (3H, MeCH2),
1.26 t (3H, MeCH2), 1.84 br.s (2H, NH2), 3.7 4.1 m
2
(4H, CH2O), 4.25 d (1H, CHP, JHP 17.0 Hz), 7.3
7.5 m (5H, Ph). 31P NMR spectrum (CHCl3),
,
P
ppm: 25.2 ppm. Found, %: N 5.68; P 12.80. C11H18
NO3P. Calculated, %: N 5.76; P 12.73.
( -Aminobenzyl)phosphonic acid (XXIIIa). The
mixture of isomers XXa and XXIa (see the synthesis
of XXIIa, 4.9 g, was heated for 1 h at 160 C and,
after addition of 10 ml of 6 N HCl, refluxed for 6 h
and extracted with ether (3 5 ml). The aqueous layer
was evaporated, and the dry residue was dissolved in
15 ml of anhydrous ethanol, and 1 ml of propylene
oxide was added. The precipitate that formed was
filtered off. Yield 2.2 g (78%), mp 278 280 C {pub-
1
fied in the H NMR spectrum (CDCl3), , ppm: 5.38
3
(2JHP 10 Hz) (VIk), 3.86 d.d (2JHP 15.6 Hz and JHH
6 Hz) (IX); VIk:IX 1:1.5. Found, %: N 3.36.
C23H24NOP. Calculated, %: N 3.88. The reaction of
( -aminobenzyl)diphenylphosphine oxide with iso-
butyraldehyde by Scheme 4 gives analogous results.
Reaction of imidoylphosphonate Va with diethyl
hydrogen phosphite and water (Scheme 11). Equi-
molar amounts of imidoylphosphonate Va, diethyl
hydrogen phosphite, and water were heated at 80 C
for 4.5 h (31P NMR control by the disappearance of
imidoylphosphonate). The resulting mixture was dis-
solved in diethyl ether, washed with four portions of
water, dried over MgSO4, filtered, and evaporated.
Yield of diethyl [ -(diethoxyphosphinoyloxy)benzyl]-
lished data [24]: mp 272 C}. 1H NMR spectrum
2
(CF3COOD), , ppm: 4.66 d (1H, CH, JHP 16.0 Hz),
7.1 m (5H, Ph). 31P NMR spectrum (H2O),
(H2O),
P
ppm: 10.55 d (2JPH 16.0 Hz). Found, %: C 44.20; H
5.38; N 7.52; P 16.58. C7H10NO3P. Calculated, %:
C 44.93; H 5.39; N 7.48; P 16.55.
( -Amino-4-bromobenzyl)phosphonic acid
(XXIIIb). A mixture of 6.2 g of N-benzyl-4-bromo-
benzimidoyl chloride and 3.6 g of triethyl phosphite
was heated at 130 C for 2 h and distilled in a vacuum.
Yield of phosphorylation products (a mixture of iso-
mers XXb and XXIb) 6.3 g (76%), bp 196 198 C
(0.04 mm Hg). The mixture was heated for 1 h at
180 C and, after addition of 13 ml of 6 N HCl, re-
fluxed for 7 h, diluted with equal volume of water,
and washed with diethyl ether (3 5 ml). The aqueous
layer was evaporated, the dry residue was dissolved
in 25 ml of anhydrous alcohol, and 1 ml of propylene
oxide was added. The precipitate that formed was
phosphonate (XVIa) 24%, oil. 1H NMR spectrum
(CDCl3), , ppm: 1.1 1.3 m (12H, MeCH2), 3.8
2
4.2 m (8H, CH2O), 5.56 d.d (1H, CH, JHP 13.8 Hz,
3JHP 10.2 Hz), 7.3 7.6 m (5H, Ph). 31P NMR spec-
3
trum (CDCl3), P, ppm: 0.76 d (1P, POCH, JPP
34.5 Hz), 17.16 d (1P, PCH, 3JPP 34.5 Hz). The forma-
tion of compounds XVIa or XVIb [ (CDCl3), ppm:
P
3
29.6 d (1P), 35.8 d.d (1P), JPP 25.5 Hz] was traced
by 31P and H NMR spectroscopy during prolonged
1
handling of compounds Va Vi. Published data,
,
P
3
ppm: XVIa: 16.87 d (1P), 0.95 d (1P), JPP 34.5 Hz
[14]; and XVIb: 29 and 32 (3JPP 26 Hz) [23].
1
filtered off. Yield 1.35 g (33%), mp 292 293 C. H
Diethyl ( -aminobenzyl)phosphonate (XXIIa).
A mixture of 4.9 g of N-benzylbenzimidoyl chloride
and 3.6 g of triethyl phosphite was heated at 140 C
for 2 h and distilled in a vacuum. Yield of phospho-
rylation products (a mixture of isomers XXa and
XXIa) 4.9 g (70%), bp 180 183 C (0.05 mm Hg).
The mixture was heated for 1 h at 160 C and, after
addition of 10 ml of dilute hydrochloric acid (1:1),
stirred at room temperature for 2 h. The aqueous solu-
tion was washed with ether, and most water was
evaporated in a vacuum without heating. The residue
was diluted with 100 ml of acetone. The colorless
precipitate of aminophosphonate XXIIa hydrochloride
was filtered off, washed with acetone, and dried in air.
Equimolar amount of triethylamine was added to a
suspension of the hydrochloride in ether. The preci-
pitate of triethylamine hydrochloride was filtered off,
the ether was evaporated, and the residue was distilled
in a vacuum. Yield 61%, bp 127 C (0.07 mm Hg). 1H
NMR spectrum (CF3COOD), , ppm: 4.91 d (1H, CH,
3
2JHP 17.0 Hz), 7.25 d (2H, Ph JHH 8.0 Hz). Found,
%: C 31.61; H 3.38; Br 29.88; N 5.34; P 11.50.
C7H9BrNO3P. Calculated, %: C 31.73; H 3.04; Br
30.15; N 5.29; P 11.69.
( -Amino-4-fluorobenzyl)phosphonic acid
(XXIIIc) was obtained analogously, yield 44%, mp
1
298 300 C. H NMR spectrum (CF3COOD), , ppm:
2
4.97 d (1H, CH, JHP 17.0 Hz), 7.06 t (2H, 3,5-HPh,
3
3JHH = JHF = 8.5 Hz), 7.4 m (2H, 2,6-HPh). 19F NMR
spectrum (D2O), F, ppm: 37.70 (against external
CF3COOH). Found, %: C 41.27; H 5.13; F 9.39; N
6.71; P 15.15. C7H9FNO3P. Calculated, %: C 40.99;
H 4.42; F 9.26; N 5.29; P 15.10.
Diethyl [ -(N-tosylamino)-4-methoxybenzyl]-
phosphonate (XXIV). A solution of equimolar
amounts of diethyl ( -amino-4-methoxybenzyl)phos-
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 74 No. 9 2004

SIGMATROPIC ISOMERIZATIONS IN AZAALLYL SYSTEMS: XX.
1349
phonate, 4-toluenesulfonyl chloride, and triethylamine
in diethyl ether was mixed at room temperature for
5 h. The triethylamine hydrochloride was filtered off,
and the ether was evaporated. The residue was tri-
turated with petroleum ether and washed with water.
Yield 29%, mp 114 115 C {published data [18]: mp
5. Onys’ko, P.P., Kim, T.V., Kiseleva, E.I., and Si-
nitsa, A.D., Zh. Obshch. Khim., 1987, vol. 87, no. 6,
p. 1233; Onys’ko, P.P., Kim, T.V., Kiseleva, E.I., and
Sinitsa, A.D., Phosphorus, Sulfur Silicon, 1990,
vol. 49/50, p. 73.
6. Sinitsa, A.D., Onys’ko, P.P., Kim, T.V., Kiseleva, E.I.,
Pirozhenko, V.V., Zh. Obshch. Khim., 1987, vol. 57,
no. 6, p. 1233.
7. Onys’ko, P.P., Kim, T.V., Kiseleva, E.I., and Si-
nitsa, A.D., Zh. Obshch. Khim., 1996, vol. 66, no. 8,
p. 1283.
8. Onys’ko, P.P., Kim, T.V., Kiseleva, E.I., Sinitsa, A.D.,
and Prokopenko, V.P., Zh. Obshch. Khim., 1990,
vol. 60, no. 3, p. 523.
9. Onys’ko, P.P., Kim, T.V., Kiseleva, E.I., Sinitsa, A.D.,
and Prokopenko, V.P., Zh. Obshch. Khim., 1997,
vol. 67, no. 5, p. 749.
10. Onys’ko, P.P., Kim, T.V., Kiseleva, E.I., and Si-
nitsa, A.D., Zh. Obshch. Khim., 1995, vol. 65, no. 12,
p. 1961.
11. Onys’ko, P.P., Kim, T.V., Kiseleva, E.I., and Si-
nitsa, A.D., Zh. Obshch. Khim., 1996, vol. 66, no. 6,
p. 936.
12. Onys’ko, P.P., Kim, T.V., Kiseleva, E.I., Sinitsa, A.D.,
and Kornilov, M.Yu., Zh. Obshch. Khim., 1990,
vol. 60, no. 6, p. 1304.
1
114 C}. H NMR spectrum (CDCl3), , ppm: 1.06 t
2
2
(3H, MeCH2, JHH 6.5 Hz), 1.32 t (3H, MeCH2, JHH
6.5 Hz), 2.31 s (3H, MeAr), 3.6 m (1H) and 3.9 m
(1H, CH2O), 3.74 s (3H, MeO), 4.17 quintet (2H,
CH2O, JHH 3JHP 7 Hz), 4.70 d.d (1H, CHP, JHP
23.7 Hz, JHH 8.7 Hz), 6.1 br.s (1H, NH), 6.64 d (2H,
HAr, JHH 8.1 Hz), 7.03 d (2H, HAr, JHH 8.1 Hz),
7.09 d (2H, HAr, JHH 8 Hz), 7.46 d (2H, HAr, JHH
8 Hz), 7.3 7.6 m (5H, Ph). 31P NMR spectrum
(CDCl3), P, ppm: 20.1 d.m, 2JHP 24 Hz.
3
2
3
3
3
3
3
3-(Diethoxyphosphinoyl)-3-(4-methoxyphenyl)-
1-phenyl-2-azaprop-2-ene (XXXVI). a (Scheme 13)
[18]. To a solution of 0.3 mmol of sodium in 3 ml of
absolute methanol, 0.1 mmol of diethyl [ -(N-tosyl-
benzylamino]-4-methoxybenzyl]phosphonate prepared
from compound XXIV according to [18] and heated
under reflux for 16 h. The solvent was removed, and
the residue was dissolved in ethyl acetate. The solu-
tion was washed with several portions of water, dried
over magnesium sulfate, and the solvent was removed
to give an oily final product. 1H NMR spectrum
13. Xiao, J., Zhang, X., and Yuan, C., Heteroatom. Chem.,
2000, vol. 11, no. 7, p. 535.
3
(CDCl3), , ppm: 1.22 t (3H, MeCH2, JHH 7.2 Hz),
2
1.24 t (3H, MeCH2, JHH 7.2 Hz), 3.81 m (3H, MeO),
14. Ruel, R., Bouvier, J.-P., and Young, R.N., J. Org.
Chem., 1995, vol. 60, no. 16, p. 5209.
15. Onys’ko, P.P., Kim, T.V., Kiseleva, E.I., and Si-
nitsa, A.D., USSR Inventor’s Certificate no. 1512100,
1989.
2
4.05 m (4H, CH2O), 4.88 d (1H, CHP, JPH 18 Hz),
6.91 d (2H, Ar), 7.42 m (3H, Ar), 7.55 m (2H, Ar),
4
7.82 m (2H, Ar), 8.39 d (1H, CH=N, JHP). 31P NMR
spectrum, P, ppm: 20.8.
16. Flynn, G.A., Beight, D.W., and Boehme, E.H.W.,
Tetrahedron Lett., 1985, vol. 26, no. 3, p. 285.
17. Yuan, C., Zhang, Y., Luoi, W., and Yao, Z., Hetero-
atom. Chem., 1998, vol. 9, no. 2, p. 139.
18. McKay, W.P. and Proctor, G.R., J. Chem. Soc.,
Perkin Trans. 1, 1981, p. 2443.
b. Condensation of diethyl ( -amino-4-methoxy-
benzyl)phosphonate with benzaldehyde under the
conditions used for preparing VIj, VIm, VIn, and
Vp Vr, yield 77%. The samples obtained by proce-
dures a and b and prepared by us previously [5] have
identical spectral characteristics.
19. Braun, J. and Pinkernelle, W., Chem. Ber., 1934,
vol. 67, p. 1218.
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RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 74 No. 9 2004