Synthesis of 2-(arylamino)ethyl phosphonic acids via the aza-Michael addition on diethyl vinylphosphonate

Article abstract of DOI:10.1016/j.tet.2012.10.059

A simple way of synthesising 2-(arylamino)ethyl phosphonic esters and acids via the aza-Michael addition of amines to diethyl vinylphoshonate 'on water' was developed. Various 2-(arylamino)ethyl phosphonates were initially produced through the condensation of primary and secondary amines with diethyl vinylphosphonate, focussing on those bearing one aromatic moiety, giving generally good to high yields (i.e.; 75-100%). These phosphonic esters were then hydrolysed in presence of bromomethylsilane to give quantitatively the corresponding phosphonic acids.

Full text of DOI:10.1016/j.tet.2012.10.059

Tetrahedron 69 (2013) 115e121
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Tetrahedron
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Synthesis of 2-(arylamino)ethyl phosphonic acids via the
aza-Michael addition on diethyl vinylphosphonate
*
ꢀ
Nadine Bou Orm, Yasmina Dkhissi, Stephane Daniele, Laurent Djakovitch
ꢀ
Universite de Lyon, CNRS, UMR 5256, IRCELYON, Institut de recherches sur la catalyse et l’environnement de Lyon, 2 avenue Albert Einstein, F-69626 Villeurbanne cedex, France
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 3 May 2012
Received in revised form 16 October 2012
Accepted 19 October 2012
Available online 29 October 2012
A simple way of synthesising 2-(arylamino)ethyl phosphonic esters and acids via the aza-Michael ad-
dition of amines to diethyl vinylphoshonate ‘on water’ was developed. Various 2-(arylamino)ethyl
phosphonates were initially produced through the condensation of primary and secondary amines with
diethyl vinylphosphonate, focussing on those bearing one aromatic moiety, giving generally good to high
yields (i.e., 75e100%). These phosphonic esters were then hydrolysed in presence of bromomethylsilane
to give quantitatively the corresponding phosphonic acids.
Keywords:
Ó 2012 Elsevier Ltd. All rights reserved.
b
b
-Aminophosphonic esters
-Aminophosphonic acids
‘On water’ aza-Michael addition
Selective phosphonic ester hydrolysis
1. Introduction
presence of basic catalysts and under extreme temperature con-
ditions and prolonged reaction times.1 It was also seen that the
Organophosphorus compounds are commonly identified as key
intermediates in the study of various biochemical processes.1 Some
of them demonstrated also various biological activity as antibac-
terial, anti-HIV or protease inhibitors.1,2 This attractive area has led
to the synthesis of numerous so-called ‘phosphorus analogues’.3
Michael reaction of primary amines with diethyl vinylphosphonate
was complete after 24 h at 70 ꢀC in presence of ethanol.25 Under
these conditions, the reaction between benzylamine and diethyl
vinylphosphonate in 1:1 ratio led selectively to the monoaddition.
Secondary amines react exothermically with diethyl vinyl-
phosphonate in the absence of solvent; piperidine and dimethyl-
amine constituting relevant examples. Among these substrates,
cyclic amines showed good reactivity that was exploited by Bau-
mann et al. for the addition of morpholine to diethyl vinyl-
phosphonate.26 Improvements were recently reported: in 2007,
Brindaban27 developed a green procedure for the aza-Michael re-
Among these, b-aminophosphonic esters and acids represent an
important family to which belong naturally occurring molecules
isolated from Celiate protozoa.4 Thus the development of useful
procedure for the synthesis of b-aminophosphonic esters and acids
is of crucial importance, particularly when considering a broad
evaluation of their biological properties.
Various synthetic methods5 have been reported to synthesise 2-
(amino)ethylphosphonic esters including carbonephosphorus,6e15
carbonecarbon16e19 or carbonenitrogen20,21 bond formations.
Among these methods, the aza-Michael reaction leading to the
formation of a carbonenitrogen bond appears to be probably the
most versatile. However, the efficiency of this reaction depends on
the nature of amines that still constitute a severe limitation in some
cases. A wide range of primary and secondary amines has been used
in reactions engaging the diethyl vinylphosphonate as a coupling
partner in the aza-Michael addition. Without being exhaustive the
main contributions refer to the use of cyclodextrine,22 DBU23 or
Al2O324 as catalyst. Primary amines were shown to react only in the
action in water without catalyst or organic solvent, using a,b-un-
saturated carboxylic esters, ketones, nitriles and amides; in 2008,
Matveeva3,28 showed that water as a solvent accelerates the addi-
tion of various amines to diethyl vinylphosphonate to yield
b-
aminophosphonates. Recently, the procedure was extended to
amino acids as suitable N-nucleophiles.28e30 Generally, aromatic
amines were shown to be inefficient with regards to Michael ad-
dition due to the significant influence of nucleophilic and steric
properties on the reaction rate. Therefore, for these substrates,
improvement of the aza-Michael reaction constitutes a challenging
topic.
If b-aminophosphonic esters represent an interesting class of
compounds, their corresponding acids are more desirable when
considering biochemical processes and corresponding biological
relevance. Unfortunately, acids derivatives are not directly syn-
thesisable via aza-Michael addition due to function incompatibility.
* Corresponding author. Tel.: þ33 472 445 381; fax: þ33 472 445 399; e-mail
address: laurent.djakovitch@ircelyon.univ-lyon1.fr (L. Djakovitch).
0040-4020/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2012.10.059

116
N. Bou Orm et al. / Tetrahedron 69 (2013) 115e121
To access this family, hydrolysis of corresponding esters remain the
best alternative. Few methods have been reported in the literature.
Direct acid catalysed hydrolysis of phosphonic esters requires
generally drastic temperature conditions as well as the use of
strong hydracids (HI>HBr>HCl).31 On the other hand, base cata-
lysed reactions led generally to the formation of the corresponding
monoester. Thus, while not catalytic, the use of halogeno-
trimethylsilanes as hydrolysing agents seemingly represents the
best choice. Given the balance between the cost and the reactivity,
bromotrimethylsilane constitutes the best compromise.32
to diethyl vinylphosphonate in presence of water (Scheme 2). To
begin with, amines 1aei, namely, benzylamine 1a, N-benzylme-
thylamine 1b, N-naphthylmethylamine 1c, dibenzylamine 1d,
1,2,3,4-tetrahydroisoquinoline 1e, phenethylamine 1f, N-methyl-
ethylenediamine 1g, diisopropylamine 1h, and dipropylamine 1i
were selected and evaluated in this reaction (see Table 2).
In this paper we report the synthesis of 2-(amino)ethyl phos-
phonic acids through the aza-Michael addition of amine to diethyl
vinylphosphonate followed by hydrolysis, focussing on aromatic
amines towards 2-(arylamino)ethylphosphonic compounds.
Scheme 2.
2. Results and discussions
Table 2
Aza-Michael reaction of diethyl vinylphosphonate and various amines in degassed
water according to Scheme 2
2.1. Synthesis of phosphonic esters 2
Entry
Amine
Product
Reaction
time
Yielda
(%)
Initially, we evaluated the influence of various solvents on the
aza-Michael equimolar reaction of benzylamine with diethyl
vinylphosphonate under inert atmosphere of argon (Scheme 1),
a reaction that was previously described in the literature and for
which the authors described optimised conditions (water, room
temperature, 24 h or water, 100 ꢀC, 45 min).3
1
2
1a
1b
2a
2b
45 min
45 min
94
100
3
1c
2c
45 min
75
Scheme 1.
4
5
1d
1e
2d
2e
45 min
45 min
35
As reported in the Table 1, the presence of water has a strong
kinetic effect. While the reaction without solvent proceeded quan-
titatively at 25 ꢀC within 11 days (Table 1, entry 1) that carried out at
120 ꢀC was completed after 24 h. Thus, increasing the reaction
temperature allowed to shorten the reaction time in absence of
solvent (Table 1, entries 1e4); however, this was accompanied by
the formation of side products that decreased chemical yields and
selectivity. The use of dry alcoholic solvents like EtOH or MeOH
allowed to improve the reaction conditions (Table 1, entries 6 and 8),
nevertheless, despite their polar character better results were ob-
tained by adding water (Table 1, entry 7). But none of these condi-
tions compete with reaction in water that was completed within
only 45 min at 100 ꢀC in high chemical yield (Table 1, entry 5).
100
6
7
1f
2f
45 min
97
b
1g
2g1
2g2
45 min
45 min
100
100
c
8
9
1h
1i
2h
2i
5 min
5 min
100
100
Table 1
Aza-Michael addition of benzylamine in different solvent and temperature
conditions
Reaction conditions: 8.4 mmol of amine, 8.4 mmol of diethyl vinylphosphonate,
Entry
Solvent
Tꢀ (ꢀC)
Reaction time
Yielda (%)
2 mL of distilled water, reflux, 5e45 min.
a
1
2
3
4
5
6
7
8
No solvent
No solvent
No solvent
No solvent
H2O
EtOH
H2O/EtOH 1/1
MeOH
25
70
120
120
Reflux
Reflux
Reflux
Reflux
11 days
18 h
18 h
96
56
86
86
94
62
87
66
Isolated yields.
b
Mono-adduct; ratio amine/diethyl vinylphosphonate¼5:1.
c
Bis-adduct; ratio amine/diethyl vinylphosphonate¼1:5.
24 h
45 min
45 min
45 min
45 min
As expected secondary amines were more reactive than primary
amines resulting in reaction completion within 45 min. Apart from
dibenzylamine 1d (Table 2, entry 4) that gave a poor selectivity and
corresponding poor yield due to possible steric effects, all evaluated
amines displayed good and repeatable results giving high yields of
at least 75%. The reactions involving N-benzylmethylamine 1b
(Table 2, entry 2) and 1,2,3,4-tetrahydroisoquinoline 1e (Table 2,
entry 5) were very selective leading to quantitative yields. The re-
activities of diisopropylamine 1h (Table 2, entry 8) and dipropyl-
amine 1i (Table 2, entry 9) are particularly remarkable as
Reaction conditions: 8.4 mmol of amine, 8.4 mmol of diethyl vinylphosphonate,
2 mL solvent, TꢀC, time. Solvents are degassed before use.
a
Isolated yields.
Having demonstrated that water is the solvent of choice to per-
form this reaction (agreeing with reported literature3,27,33,34), we
next evaluated the aza-Michael additions of primary and secondary
amines, focussing particularly on those bearing an aromatic group,

N. Bou Orm et al. / Tetrahedron 69 (2013) 115e121
117
quantitative conversions are achieved in only 5 min. In all cases, 1H
NMR showed the disappearance of the vinylic protons at w6 ppm,
and a corresponding appearance of shifts relating to aliphatic
protons at w2 ppm (CH2P) and w2.8 ppm (CH2N), giving proof
of reaction. The 31P NMR showed one phosphorous species at
w30 ppm attributed to the expected product, differing from the
signal of the starting material ( w17 ppm).
evaluated the influence of both the atmosphere and the reaction
time. Thus several experiments were conducted under either air
or inert atmosphere of argon, with two different reaction times
(Table 4).
d
d
d
d
Table 4
d
Aza-Michael reaction of diethyl vinylphosphonate with N-naphthylmethylamine 1c
in degassed water under different reaction conditions
The specific case of N-methylethylenediamine 1g requires more
details. While the dual reactivity of ethylene diamine was pre-
viously described by Odinets et al.3 indicating that when the di-
amine is used in the ratio 1:1, only the mono adducts was formed
while bis-addition was observed with a ratio diethyl vinyl-
phosphonate/amine¼1:2. To the best of our knowledge, no exam-
ple concerning the selectivity of the reaction when engaging
a diamine in which primary and secondary amine functionality are
present was previously reported. In order to answer this question
we then engaged N-methylethylenediamine 1g. As reported in
Table 3, using a 1:1 ratio between the amine 1g and the vinyl-
phosphonate resulted in a mixture of mono- and bis-adduct com-
pounds, in favour of the mono-derivative with a 77% selectivity.
Increasing the amine loading to 2:1 allowed to enhance the selec-
tivity towards the mono-adduct derivative; the best being achieved
by using a ration amine : vinylphosphonate¼5:1. Reacting N-
methylethylenediamine 1g with diethyl vinylphosphonate in a ra-
tio 1:5 deliver cleanly the expected bis-adduct. Interestingly
a lower vinylphosphonate loading allowed already to obtain se-
lectively (i.e., 89%) the bis-adduct.
Entry
Reaction conditions
Conv.
(%)a
Sel.
Yielda
(%)
(%)a
1
2
3
4
45 mineAir
90 mineAir
45 mineInert atmosphere
90 mineInert atmosphere
75
92
78
92
80
96
96
95
60
88
75
87
Reaction conditions: 8.4 mmol of amine, 8.4 mmol of diethyl vinylphosphonate,
2 mL of distilled water, reflux, 45 min.
a
Determined by GC after calibrating the signals corresponding to the starting
materials and the products using analytically pure samples versus n-dodecane.
If conversion versus diethyl vinylphosphonate is not affected by
the nature of the atmosphere for a given reaction time, the selec-
tivity of the reaction does depend on the nature it; however not
linearly. Thus, when working at a run time of 45 min the selectivity
of the reaction drops from 96% under inert atmosphere to 80%
under air, the influence is less marked when working for 90 min as
apparently the same selectivity is achieved (i.e., ca. 95%). This in-
dicates that the aforementioned effect would be more pronounced
when working at short reaction time (i.e., 45 min) due to the lim-
ited conversion. In conclusion, these results showed that the re-
action is sensitive towards oxygen, leading probably to the
formation of side products due to amine degradation by the dis-
solved oxygen. To our opinion, this is most likely related to the
difficulties in achieving a strictly inert atmosphere when working
in water.
Table 3
Optimisation of the reaction of N-methylethylenediamine 1g with diethyl vinyl-
phosphonate and various amines in degassed water according to Scheme 2
Selectivity (%)a
Mono
Bis
(equiv)
(equiv)
With these results in hand, next we evaluated several aromatic
amines derived from aniline, as well as carbamates, in order to
assess the scopes and limitations of the procedure. Thus, aniline 1k,
ethylaniline 1l, aminopyrene 1m, and benzylcarbamate 1n were
engaged in the aza-Michael addition to vinyl diethylphosphonate
(Table 5). At first, all reactions were carried out in water.
1
1
1
1
2
5
1
1.5
2
5
1
77
46
5
0
97
100
23
54
89
100
3
1
0
Reaction conditions: 8.4 (mmol ꢁ equiv) of amine, 8.4 (mmol ꢁ equiv) of diethyl
vinylphosphonate, 2 mL of distilled water, reflux, 45 min.
a
Determined by GC after calibrating the signals corresponding to the starting
materials and the products using analytically pure samples versus n-dodecane.
Table 5
Aza-Michael reaction of diethyl vinylphosphonate with 1ken in degassed water or
water/EtOH
The structures of both compounds were certified by NMR and
Mass analyses. The bis-adduct 2g2 deliver clear signal in 31P at
30.84 and 30.09 ppm, and 13C NMR at 26.14 and 23.31 with CeP
coupling constant 1J(C,P)¼139.1 and 138.4 Hz, respectively, in full
agreement with the structure. Additionally, Mass Spectra with
(m/z)¼403.21 confirm the identification. As for 2g2, the mono-
adduct derivative 2g1 show signal at 30.15 ppm in 31P NMR
and at 23.64 ppm in 13C NMR with a 1J(C,P) coupling constant of
139.1 Hz attributed to R(CH3)NCH2CH2PO(OEt)2 in which the
secondary amine function of 1h reacted with the diethyl vinyl-
phosphonate. This attribution is supported by comparisons to
NMR data of 2g1 to 2b versus 2a and 2f. Mass spectra with (m/
z)¼286.15 support mono-addition. In no case the mono-addition
due to the reaction of primary amine side (i.e., R-NH2) was
observed.
Entry
Amine
Solvent
H2O
Reaction
time
1
2
1k
1l
45 min
H2O
45 min
6 h
H2O/EtOH
45 min
6 h
3
4
1m
1n
H2O
45 min
6 h
45 min
6 h
H2O/EtOH
If aza-Michael addition of evaluated amines to diethyl vinyl-
phosphonate is generally exempt of by-products, impurities and
side products were observed for that with N-naphthylmethyl-
amine 1c (Table 2, entry 3). This was interpreted as a conse-
quence of the degradation of 1c under the reaction conditions. In
order to identify the causes of formation of side products, we
H2O/EtOH
45 min
6 h

118
N. Bou Orm et al. / Tetrahedron 69 (2013) 115e121
Table 6
Hydrolysis of
Surprisingly, no product was observed whatever the reaction time.
If this assumption agrees with some literature for 1k,3 it was
somewhat unexpected for 1l that is supposed to be more nucleo-
philic. Next we envisioned that the lack of solubility of 1len in
water could affect their reactivity, encouraging us to evaluate their
reactivity in a mixture H2O/EtOH (1:1) were these amines are sol-
uble. Unfortunately, under these conditions no product was formed
indicating that the limitation of the procedure is closely linked to
the nucleophilic character of the engaged amine in such aza-
Michael reaction.
b-aminophosphonic ethyl esters according to Scheme 3
Entry
Amine
Equiv
BrSiMe3
Product
Yield
(%)
1
4.8
6.8
4a
67
100
2
3
4.8
4b
4c
100
4.8
6.8
52
100
2.2. Synthesis of phosphonic acids
As described in introduction, the route to prepare phosphonic
acids requires a two step procedure: 1/the synthesis of phosphonic
esters; 2/the selective hydrolysis to obtain the corresponding acids.
Thus we evaluated the hydrolysis of the previously prepared
phosphonic esters 2aeg towards the corresponding acids 4aeg
using bromotrimethylsilane as cleaving agent. As depicted in
Scheme 3, this procedure proceed through the trimethylsilyl in-
termediates, that were in the range of our reaction sets isolated
while this is not required. Such an approach allowed us to optimise
the reaction conditions.
4
4.8
4e
100
6
7
4.8
4.8
4f
100
100
4g1
mass spectra and NMR analyses did not correspond to the expected
structure. Further characterisations are necessary in order to
identify the obtained molecule.
Scheme 3.
3. Conclusion
The reaction was monitored by 1H NMR following both the
appearance of a signal related to the protons of trimethylsilyl
Novel 2-(arylamino)ethyl phosphonic ethyl esters bearing an
aromatic moiety were synthesised via a direct aza-Michael addition
of the corresponding amines to diethyl vinylphosphonate. Once
optimised the reaction gave nearly quantitative yields towards the
expected compounds, except for dibenzylamine that led to low
yield due to steric hindrance. These compounds were then further
quantitatively transformed to the corresponding acids via an opti-
mised two step hydrolysis.
moiety (
of the aromatic groups (
d
w0 ppm) and the ratio between these protons and those
w7 ppm). Additionally, the conversion of
d
the phosphonic ethyl esters towards the corresponding silyl and
acid derivatives was monitored by the chemical shifts in 31P NMR at
each hydrolysis step.
The results reported in Table 6 indicate that the ratio phos-
phonic esters/bromotrimethylsilane depends on the nature of the
substrate. Thus, while 4.8 equiv of bromotrimethylsilane were
sufficient to quantitatively hydrolyse the esters 2a and 5a, a larger
excess (i.e., 6.8 equiv) should be used when engaging the esters 1a
and 3a. This is most likely related to the nature of the latter sub-
strates that present a relatively acidic proton on the amine function
that can therefore deliver under the reaction conditions the cor-
responding N-silylated compound consuming thus bromo-
trimethylsilane. Such a hypothesis was confirmed by analysing the
crude reaction mixture by 1H NMR that present in these cases
several signals in the range of ꢂ0.5e1 ppm attributed to the various
N- and O-trimethylsilyl groups. Thank to the use of a larger excess
of bromotrimethylsilane, such a disappointing partial hydrolysis of
the phosphonic ethyl esters could be avoided.
4. Experimental section
4.1. General
All commercial materials were used without further purifica-
tion. Analytical thin layer chromatography (TLC) was performed on
Fluka Silica Gel 60 F254. GC analyses were performed on a HP 4890
chromatograph equipped with a FID detector, a HP 6890 auto-
sampler and
a
HP-5 column (cross-linked 5% phenyl-
m film thickness) with
methylsiloxane, 30 mꢁ0.25 mm i.d.ꢁ0.25
m
nitrogen as carrier gas. GCeMS analyses were obtained on a Shi-
madzu GCeMS-QP2010S equipped with a Sulpelco SLB-5MS col-
umn
(95%
methylpolysiloxaneþ5%
phenylpolysiloxane,
m) with Helium as carrier gas. Ionisation
NMR analyses of the compounds 4aen gave data in accordance
30 mꢁ0.25 mmꢁ0.25
m
with the proposed structure. Particularly, in 1H NMR, the shifts at
was done by electronic impact at 70 eV. Conversions were de-
termined by GC based on the relative area of GC-signals referred to
an internal standard (biphenyl) calibrated to the corresponding
pure compounds. The experimental error was estimated to be
Drel¼ꢃ5%. Chemical yields refer to pure isolated substances. Puri-
fication of products was accomplished by flash chromatography
performed at a pressure slightly greater than atmospheric pressure
using silica (MachereyeNagel Silica Gel 60, 230e400 mesh) with
the indicated solvent system. Liquid NMR spectra were recorded on
a BRUKER AC-250 spectrometer. All chemical shifts were measured
relative to residual 1H or 13C NMR resonances in the deuterated
d
wꢂ0.5e0.5 ppm related to the appearance of the 18 protons of
the trimethylsilyl groups. 31P NMR showed a shift at
w9e11 ppm
attributed to the phosphonic trimethylester group, differing from
the signal in the starting material ( w17 ppm). Concerning the
target acids 4aeg, 31P NMR presented a shift at
w19 ppm at-
d
d
d
tributed to the phosphonic acid group. For these compounds, IR
analyses showed characteristic large absorption bands between
2500 and 3000 cmꢂ1. Unexpectedly, the double adduct 2g2 on N-
methylethylenediamine 1g did not deliver the corresponding
double acid leading to the formation of a single compound those

N. Bou Orm et al. / Tetrahedron 69 (2013) 115e121
119
solvents: CDCl3,
d
: 7.25 ppm for 1H, 77.0 ppm for 13C; D2O,
: 3.31 ppm (quintet) for 1H, 49.0 ppm for
d
:
3.11 (s, 1H, NH), 3.05 (t, J¼7.27 Hz, 1H, CH2N), 2.99 (t, J¼7.43 Hz, 1H,
CH2N), 2.09 (t, J¼7.32 Hz, 1H, CH2P), 2.02 (t, J¼7.37 Hz, 1H, CH2P),
4.79 ppm for 1H; MeOD,
d
13C. Data are reported as follows: chemical shift, multiplicity
(s¼singlet, d¼doublet, t¼triplet, q¼quartet, m¼multiplet,
br¼broad). High resolution mass spectra (HRMS) were recorded on
a Thermo Finnigan MAT 95 XL spectrometer, with isobutan as re-
actant gas for CI at the ‘Centre Commun de Spectrometrie de Masse,
UMR5246 CNRS-Universite Claude Bernard Lyon 1’. Compound 2h
1.25 (t, J¼7.03 Hz, 6H, CH3). 13C NMR (62.9 MHz, CDCl3):
d: 134.20
(CqeC10H7), 133.82 (CqeC10H7), 131.64 (CqeC10H7), 128.72
(CHeC10H7), 128.06 (CHeC10H7), 126.37 (CHeC10H7), 126.32
(CHeC10H7), 125.71 (CHeC10H7), 125.38 (CHeC10H7), 123,51
(CHeC10H7), 61.7 (d, J¼6.44 Hz, CH2O), 50.73 (d, J¼6.9 Hz,
CH2eC10H7), 42.99 (d, J¼3.2 Hz, CH2N), 25.97 (d, J¼139.43 Hz,
ꢀ
ꢀ
gave analytical analyses in agreement with reported data (CAS
Number [500882-07-05]).
CH2P), 16.33 (d, J¼6 Hz, CH3). 31P NMR (101 MHz, CDCl3):
d: 30.20.
HR ESIMS: calcd for C17H24NO3P [MþH]þ 322.1567, found m/z
322.1571.
4.2. General procedure for the preparation of phosphonic
esters
To a 50 mL round bottom flask fitted with a reflux condenser
was added 8.4ꢁ10ꢂ3 mol of amine, 8.4ꢁ10ꢂ3 mol of diethyl vinyl-
phosphonate and 2 mL of degassed distilled water. The reaction
mixture was heated under reflux at 100 ꢀC for 45 min and the water
subsequently removed by freeze drying delivering thus analytically
pure compounds. The product were characterised by GC, GCeMS,
1H, 13C and 31P NMR, HRMS.
Compound 2d was obtained as orange oil (35%). C20H28NO3P
(361.18) m/z (GCeMS)¼362 [MHþ].
1H NMR (250 MHz, CDCl3):
d: 7.52e7.13 (m, 10H, C6H5),
O
O
4.14e3.91 (m, 4H, CH2O), 3.83 (s, 4H, C6H5CH2), 2.80 (ddd,
J¼10.8 Hz, 7.5, 5.4 Hz, 2H, CH2N), 2.46 (d, J¼34.5 Hz, 2H, CH2P),
P
N
H
O
1.35e1.11 (m, 6H, CH3). 31P NMR (101 MHz, CDCl3):
d: 31.03.
Compound 2a was obtained as yellow oil (94%). 1H NMR
(250 MHz, CDCl3):
d
: 7.29e7.14 (m, 5H, C6H5), 4.02 (q, J¼7.28 Hz, 4H,
CH2O), 3.73 (s, 2H, C6H5CH2), 2.89 (t, J¼7.42 Hz, 1H, CH2NH), 2.83 (t,
J¼7.34 Hz, 1H, CH2NH), 2.31 (s, 1H, NH), 1.99 (t, J¼7.16 Hz, 1H, CH2P),
1.91 (t, J¼7.24 Hz, 1H, CH2P), 1.23 (t, J¼7.00 Hz, 6H, CH3). 13C NMR
Compound 2e was obtained as yellow oil (100%). 1H NMR
(250 MHz, CDCl3):
(62.9 MHz, CDCl3): d: 138.63 (CqeC6H5), 128.40 (CHeC6H5), 128.10
d
: 7.14e6.96 (m, 4H, C6H4), 4.07 (q, J¼7.11 Hz, 4H,
(CHeC6H5), 127.08 (CHeC6H5), 61.53 (d, J¼6.44 Hz, CH2O), 53.40
CH2O), 3.63 (s, 2H, CH2N), 2.97e2.69 (m, 6H, CH2N and CH2),
(CH2eC6H5), 42.6 (d, J¼3.4 Hz, CH2N), 26.24 (d, J¼137.95 Hz, CH2P),
2.17e1.97 (m, 2H, CH2P), 1.28 (t, J¼7.1 Hz, 6H, CH3). 13C NMR
16.39 (d, J¼6.00 Hz, CH3). 31P NMR (101 MHz, CDCl3):
d: 30.35. HR
ESIMS: calcd for C13H22NO3P [MþH]þ 272.1410, found m/z
(62.9 MHz, CDCl3): d: 133.93 (CqeC6H4), 133.82 (CqeC6H4), 128.62
(CHeC6H4), 126.53 (CHeC6H4), 126.28 (CHeC6H4), 125.70
(CHeC6H4), 61.62 (d, J¼6.46 Hz, CH2O), 55.31 (CH2N), 51.29 (CH2N),
50.47 (CH2N), 28.83 (CH2), 23.98 (d, J¼139.13 Hz, CH2P), 16.43 (d,
272.1409.
O
O
J¼6.10 Hz, CH3). 31P NMR (101 MHz, CDCl3):
d: 30.18. HR ESIMS:
P
N
calcd for C15H24NO3P [MþH]þ 298.1567, found m/z 298.1572.
O
Compound 2b was obtained as orange oil (100%). 1H NMR
(250 MHz, CDCl3):
d
: 7.31e7.08 (m, 5H, C6H5), 3.98 (q, J¼7.34 Hz, 4H,
CH2O), 3.42 (s, 2H, C6H5CH2), 2.72e2.57 (m, 2H, CH2N), 2.12 (s, 3H,
NCH3), 2.03e1.80 (m, 2H, CH2P), 1.19 (t, J¼7.07 Hz, 6H, CH3). 13C
Compound 2f was obtained as yellow oil (100%). 1H NMR
(250 MHz, CDCl3):
d
: 7.25e7.05 (m, 5H, C6H5), 3.96 (t, J¼7.09 Hz, 4H,
NMR (62.9 MHz, CDCl3): d: 138.28 (CqeC6H5), 128.92 (CHeC6H5),
CH2O), 2.91e2.66 (m, 6H, C6H5CH2 and CH2NH), 2.50 (s, NH), 1.90 (t,
J¼7.35 Hz, 1H, CH2P), 1.83 (t, J¼7.43 Hz, 1H, CH2P), 1.19 (t, J¼7.24 Hz,
128.18 (CHeC6H5), 127.05 (CHeC6H5), 61.47 (CH2N), 61.41 (d,
J¼6.7 Hz, CH2O), 50.30 (CH2eC6H5), 41.34 (CH3N), 23.6 (d,
J¼138.29 Hz, CH2P), 16.35 (d, J¼6.02 Hz, CH3). 31P NMR (101 MHz,
6H, CH3). 13C NMR (62.9 MHz, CDCl3):
d: 139.65 (CqeC6H5), 128.57
(CHeC6H5), 128.37 (CHeC6H5), 126.10 (CHeC6H5), 61.46 (d,
J¼6.46 Hz, CH2O), 50.67 (CH2eNH), 43.11 (d, J¼3.25 Hz, CH2N),
36.09 (CH2eC6H5), 26.27 (d, J¼139.32 Hz, CH2P),16.33 (d, J¼5.97 Hz,
CDCl3):
d
: 30.48. HR ESIMS: calcd for C14H24NO3P [MþH]þ 286.1567,
found m/z 286.1572.
CH3). 31P NMR (101 MHz, CDCl3):
d: 30.15. HR ESIMS: calcd for
C14H24NO3P [MþH]þ 286.3231, found m/z 286.3235.
Compound 2c was obtained as yellow oil (88%). Noteworthy, the
reaction mixture was heated under reflux at 100 ꢀC for 90 min and
under an inert atmosphere. 1H NMR (250 MHz, CDCl3):
(m, 7H, C10H7), 4.24 (s, 2H, C10H7CH2), 4.04 (q, J¼7.12 Hz, 4H, CH2O),
d
: 8.24e7.24
Compound 2g1 was obtained as a colourless viscous oil (100%).
1H NMR (250 MHz, CDCl3):
d: 4.17e3.97 (m, 4H, CH2O), 3.02 (s, 2H,

120
N. Bou Orm et al. / Tetrahedron 69 (2013) 115e121
NH2), 2.84e2.74 (m, 2H, CH2NH2), 2.73e2.59 (m, 2H, CH2NCH3),
2.44 (t, J¼5.98 Hz, 2H, CH2NCH3), 2.21 (s, 3H, CH3N), 2.00e1.86 (m,
2H, CH2P), 1.30 (t, J¼7.13 Hz, 6H, CH3). 13C NMR (62.9 MHz, CDCl3):
d
: 61.58 (d, J¼6.48 Hz, CH2O), 58.65 (CH2N(CH3)CH2), 50.58 (d,
J¼2 Hz, CH2N(CH3)CH2), 41.54 (CH3N), 38.91 (CH2NH2), 23.64 (d,
J¼139.12 Hz, CH2P), 16.42 (d, J¼6.02 Hz, CH3). 31P NMR (101 MHz,
Compound 3a 1H NMR (250 MHz, CDCl3):
d: 7.42e6.84 (m, 5H,
CDCl3):
d
: 30.15. HR ESIMS: calcd for C9H23N2O3P [MþH]þ 239.1519,
C6H5), 3.93e3.58 (m, 2H, C6H5CH2), 3.17 (q, J¼7.22 Hz, 2H, CH2NH),
2.97e2.55 (m, 2H, CH2P), 0.13e0.34 (m, 18H, SiCH3). 31P NMR
found m/z 239.1516.
(101 MHz, CDCl3): d: 21.43.
O
O
H
N
O
P
N
P
O
O
O
Compound 4a was obtained as a white solid (100%). C9H14NO3P
(215.29). FT-IR (KBr) (cmꢂ1): 3600e3300m (
NeH); 2960e2850s
C]C); 1470e1430m
P]O), 1167e1006m ( PeO, PeC); 720w
CeH), 710e685s (mono-substituted benzene ring). 1H NMR
Compound 2g2 was obtained as a colourless viscous oil (100%).
1H NMR (250 MHz, CDCl3):
: 4.05e3.85 (m, 8H, CH2O), 3.00 (s, 1H,
NH), 2.85e2.7 (m, 2H, CH2NH), 2.62e2.48 (m, 4H, CH2NH and
CH2NCH3), 2.45e2.32 (m, 2H, CH2NCH3), 2.08 (s, 3H, CH3N),
1.98e1.68 (m, 4H, CH2P), 1.18 (t, J¼7.11 Hz, 12H, CH3). 13C NMR
n
d
(
(
(
n
CeH); 2700e2560m
CeH), 1240e1180s (
(nOeH); 1600m (n
d
n
n
n
(250 MHz, MeOD): d: 7.46e7.15 (m, 5H, C6H5), 4.14 (s, 2H, C6H5CH2),
3.19 (dt, J¼16.8, 5.3 Hz, 2H, CH2NH), 2.04e1.80 (m, 2H, CH2P). 13
C
(62.9 MHz, CDCl3):
d
: 61.42 (d, J¼6.45 Hz, CH2O), 61.37 (d,
J¼6.46 Hz, CH2O), 55.9 (CH2N(CH3)CH2), 50.42 (d, J¼1.45 Hz,
CH2N(CH3)CH2), 46.45 (CH2NHCH2), 43.19 (d, J¼2.71 Hz,
CH2NHCH2), 41.37 (CH3N), 26.14 (d, J¼139.07 Hz, CH2P), 23.31 (d,
J¼138.36 Hz, CH2P), 16.27 (d, J¼5.90 Hz, CH3). 31P NMR (101 MHz,
NMR (62.9 MHz, MeOD): dppm
: 130.66 (CqeC6H5), 129.38
(CHeC6H5), 128.97 (CHeC6H5), 128.56 (CHeC6H5), 50.38
(CH2eC6H5), 41.92 (CH2N), 23.91 (d, J¼138.35 Hz, CH2P). 31P NMR
(101 MHz, MeOD): d: 19.91. Elemental Analysis: calcd: C, 50.23; H,
CDCl3):
d
: 30.84; 30.09. HR ESIMS: calcd for C15H36N2O6P2 [MþH]þ
6.56; N, 6.51; O, 22.31; P, 14.39; found: C, 50.53; H, 6.58; N, 6.48; P,
14.34.
403.2121, found m/z 403.2120.
Compound 3b 1H NMR (250 MHz, CDCl3):
d: 7.10e7.58 (m, 5H,
C6H5), 3.14 (s, 2H, C6H5CH2), 2.45 (dt, J¼7.3, 5.4 Hz, 2H, CH2N), 2.02
Compound 2i was obtained as yellow oil (100%). 1H NMR
(400 MHz, CDCl3): d: 4.08e3.95 (m, 4H, CH2O), 2.75e2.66 (m, 2H,
(s, 3H, CH3N), 1.74 (m, 2H, CH2P), ꢂ0.11 (d, J¼52.9 Hz, 18H, SiCH3).
31P NMR (101 MHz, CDCl3):
d: 11.32.
(CH2)2NCH2), 2.31e2.25 (m, 4H, CH2N(CH2)CH2), 1.88e1.76 (m, 2H,
CH2P), 1.43e1.31 (m, 4H, CH2CH2CH3), 1.251 (t, J¼7.15 Hz, 6H,
OCH2CH3), 0.802 (t, J¼7.44 Hz, 6H, CH2CH3). 13C NMR (100 MHz,
CDCl3):
d
: 61.63 (d, J¼6.28 Hz, CH2O), 55.68 (CH2NCH2), 46.93
((CH2)2NCH2), 22.90 (d, J¼137.00 Hz, CH2P), 20.54 (CH2CH2CH3),
16.63 (d, J¼6.33 Hz, OCH2CH3), 12.05 (d, J¼6.33 Hz, CH2CH2CH3). 31
P
Compound 4b was obtained as viscous colourless oil (100%).
C10H16NO3P (229.21). FT-IR (KBr) (cmꢂ1): 3002e2823s (
CeH);
NMR (160 MHz, CDCl3): d
: 32.40. GCeMS: calcd for C12H28NO3P Mþ
n
265.32; found m/z [Mþ] 265.20 (7.5%); [MꢂC2H5]¼236.15 (100%);
[MꢂPO(OC2H5)2]¼114.15 (70%); [N(C3H7)2]¼100.15 (65%).
2749e2625m
1262e1138s (
(
n
OeH); 1652m
(
n
C]C); 1489e1436m CeH),
(
d
nP]O), 1138e999m (
n
PeO, PeC); 740w (nCeH),
727e688s (mono-substituted benzene ring). 1H NMR (250 MHz,
4.3. General procedure for the preparation of phosphonic
acids
D2O):
d
: 7.53e7.26 (m, 5H, C6H5), 4.35 (dd, J¼14.7, 8.2 Hz,1H, CH2N),
4.21e4.02 (m, 1H, CH2N), 3.48e3.06 (m, 2H, C6H5CH2), 2.68 (d,
J¼5.7 Hz, 2H, CH2P). 13C NMR (62.9 MHz, MeOD):
d: 130.41
To a three necked round bottom flask fitted with a reflux con-
(CqeC6H5), 129.42 (CHeC6H5), 129.39 (CHeC6H5), 128.73
(CHeC6H5), 58.65 (CH2eC6H5), 51.87 (CH2N), 37.78 (CH3N), 23.00
denser, an argon bubbler and a dropping funnel was added
8.4ꢁ10ꢂ3 mol
b-aminophosphonic ethyl ester and the system was
(d, J¼130.46 Hz, CH2P). 31P NMR (101 MHz, D2O):
d: 18.00. Ele-
purged under an argon flow for 5 min. Following this, 2.4 equiv of
bromotrimethylsilane (2.0ꢁ10ꢂ2 mol, 2.64 mL) for the synthesis
involving secondary amines or 3.4 equiv of bromotrimethylsilane
(2.86ꢁ10ꢂ2 mol, 3.77 mL) for the synthesis involving primary
amines were added dropwise to the reaction mixture. The reaction
mixture was subsequently stirred at room temperature for 3 h. The
air and moisture sensitive intermediate b was characterised by 1H
and 31P NMR. To the reaction mixture was added an excess of
methanol (10 mL) at room temperature over 15 min under inert
atmosphere. After removing the volatile compounds (solvent,
silylated side products), the analytically pure phosphonic acid 1e5c
were obtained and characterised by 1H, 13C and 31P NMR, and IR.
mental Analysis: calcd: C, 52.40; H, 7.04; N, 6.11; O, 20.94; P, 13.51;
found: C, 52.34; H, 7.00; N, 6.07; P, 13.48.
Compound 3c 1H NMR (250 MHz, CDCl3)
d: 8.22 (s, 1H, C10H7),
8.00e7.61 (m, 2H, C10H7), 7.61e7.18 (m, 4H, C10H7), 4.46e4.22 (m,
2H, C10H7CH2), 3.12e2.80 (m, 2H, CH2NH), 2.28e1.95 (m, 2H, CH2P),
0.34e0.35 (m, 18H, SiCH3). 31P NMR (101 MHz, CDCl3):
d: 9.11.

N. Bou Orm et al. / Tetrahedron 69 (2013) 115e121
121
128.35 (CHeC6H5), 49.87 (CH2NH), 44.19 (CH2NH), 33.43
(CH2eC6H5), 25.62 (d, J¼139.59 Hz, CH2P). 31P NMR (101 MHz,
CDCl3): d: 21.58. Elemental Analysis: calcd: C, 52.40; H, 7.04; N, 6.11;
O, 20.94; P, 13.51; found: C, 52.39; H, 7.08; N, 6.13; P, 13.49.
Compound 4c was obtained as orange solid (100%). C13H16NO3P
(265.35). FT-IR (KBr) (cmꢂ1): 3630e3250m (
NeH); 2960e2850s
C]C); 1479e1450m
PeO, PeC); 1239e1179s ( P]O), 766s
n
(
n
CeH); 2700e2560m
CeH), 1123e1003m (
(nOeH); 1574m (n
n
(d
n
Compound 4g1 was obtained as yellow oil (100%). C5H15N2O3P
(naphthalene), 795m (mono-substituted benzene ring). 1H NMR
(182.15) FT-IR (KBr) (cmꢂ1): 3600e3280m (
n
NeH); 3035e2852s
(250 MHz, MeOD):
d
: 8.21 (s, 1H, C10H7), 8.05 (dd, J¼28.7, 20.9 Hz,
(
(
(
n
CeH); 2710e2583m (
CeH), 1246e1176s (
CeH). 1H NMR (250 MHz, MeOD):
n
OeH); 1620e1556m (
P]O), 1175e998m (
dNH2); 1482e1440m
2H, C10H7), 7.73e7.47 (m, 4H, C10H7), 4.76 (d, J¼3.4 Hz, 2H,
C10H7CH2), 2.12 (ddd, J¼36.1, 22.1, 14.2 Hz, 2H, CH2N), 1.29 (ddd,
d
n
n
PeO, PeC); 743w
n
d: 2.98 (s, 2H, NH2), 2.88e2.65
J¼28.4, 17.8, 10.7 Hz, 2H, CH2P). 13C NMR (62.9 MHz, MeOD):
d:
(m, 2H, CH2NH2), 2.69e2.58 (m, 2H, CH2NCH3), 2.55e2.41 (m, 2H,
135.43 (CqeC10H7), 132.61 (CqeC10H7), 131.70 (CqeC10H7), 130.49
(CHeC10H7), 130.14 (CHeC10H7), 128.58 (CHeC10H7), 128.32
(CHeC10H7), 127.67 (CHeC10H7), 126.55 (CHeC10H7), 123,96
(CHeC10H7), 49.92 (CH2eC10H7), 44.19 (CH2N), 25.53 (d,
CH2NCH3), 2.12 (s, 3H, CH3N), 1.98e1.79 (m, 2H, CH2P). 13C NMR
(62.9 MHz, MeOD):
CH2), 42.03 (CH3N), 38.93 (CH2NH2), 21.18 (d, J¼138.91 Hz, CH2P).
31P NMR (101 MHz, MeOD):
: 21.32. Elemental Analysis: calcd: C,
d: 58.05 (CH2N(CH3)CH2), 51.58 (CH2N(CH3)
d
J¼139.10 Hz, CH2P). 31P NMR (101 MHz, MeOD):
d: 20.52. Elemental
32.97; H, 8.30; N, 15.38; O, 26.35; P, 17.00; found: C, 32.95; H, 8.29;
N, 15.40; P, 17.05.
Analysis: calcd: C, 58.87; H, 6.08; N, 5.28; O,18.10; P,11.68; found: C,
58.83; H, 6.02; N, 5.24; P, 11.63.
References and notes
1. Palacios, F.; Alonso, C.; de los Santos, J. M. Chem. Rev. 2005, 105, 899e931.
2. Gumiena-Kontecka, E.; Galezowska, J.; Drag, M.; Lataika, R.; Kafarski, P.;
Kozlowski, H. Inorg. Chim. Acta 2004, 357, 1632e1636.
3. Matveeva, E. V.; Petrovski, P. V.; Odinets, I. L. Tetrahedron Lett. 2008, 49,
6129e6133.
4. Horiguchi, M.; Kandatsu, M. Nature 1959, 184, 901e902.
5. Dembitsky, V. M.; Al Quntar, A. A. A.; Haj-Yehiaa, A.; Srebnik, M. Mini-Rev. Org.
Chem. 2005, 2, 91e109.
Compound 3e 1H NMR (250 MHz, CDCl3):
d: 7.10 (m, 4H, C6H4),
4.10 (m, 3H, CH2N and CHaHbN), 3.03 (m, 5H, CH2N, CHaHbN and
CH2), 2.11 (m, 2H, CH2P), 0.38e0.11 (m, 18H, SiCH3). 31P NMR
6. Odinets, I. L.; Artyushin, O. I.; Shevchenko, N.; Petrovskii, P. V.; Nenajdenko, V.
G.; Roschenthaler, G.-V. Synthesis 2009, 577e582.
(101 MHz, CDCl3). 31P NMR (101 MHz, CDCl3)
d 11.50.
7. Michaelis, A.; Kaehne, R. Ber. Dtsch. Chem. Ges. 1898, 31, 1048e1055.
8. Boutagy, J.; Thomas, R. Chem. Rev. 1974, 74, 87e99.
9. Arbuzov, A. E. J. Russ. Phys.-Chem. Soc. 1906, 38, 687.
10. Bhattacharya, A. K.; Thyagarajan, G. Chem. Rev. 1981, 81, 415e430.
11. Hirao, T.; Masunaga, T.; Ohshiro, Y.; Agawa, T. Tetrahedron Lett. 1980, 21,
3595e3598.
12. Hirao, T.; Masunaga, T.; Ohshiro, Y.; Agawa, T. Synthesis 1981, 56e57.
13. Hirao, T.; Masunaga, T.; Yamada, N.; Ohshiro, Y.; Agawa, T. Bull. Chem. Soc. Jpn.
1982, 55, 909e913.
14. Kalek, M.; Ziadi, A.; Stawinski, J. Org. Lett. 2008, 10, 4637e4640.
15. Gooßen, L. J.; Dezfuli, M. K. Synlett 2005, 445e448.
16. Pavan, M. P.; Manab, C.; Swamy, K. C. K. Eur. J. Org. Chem. 2009, 2009,
5927e5940.
OH
N
P
OH
O
Compound 4e was obtained as orange solid (100%). C11H16NO3P
(245.25). FT-IR (KBr) (cmꢂ1): 3033e2854s (
CeH); 2784e2519m
OeH); 1650m ( C]C); 1469e1401m ( CeH), 1229e1181s ( P]
O), 1180e1090m ( PeO, PeC); 765e724w (bisubstituted aromatic
n
(n
n
d
n
n
ring). 1H NMR (250 MHz, MeOD):
d: 7.11e7.38 (m, 4H, C6H4), 4.38 (s,
17. Tarabay, J.; Al-Maksoud, W.; Jaber, F.; Pinel, C.; Prakash, S.; Djakovitch, L. Appl.
2H, CH2N), 3.82 (t, J¼16.6 Hz, 1H, CHaHbN), 3.64e3.30 (m, 3H,
Catal., A 2010, 388, 124e133.
CHaHbN and CH2), 2.00 (ddd, J¼22.3, 15.0, 7.2 Hz, 2H, CH2P). 13C
18. Xu, Y.; Jin, X.; Huang, G.; Huang, Y. Synthesis 1983, 556e558.
19. Al-Maksoud, W.; Mesnager, J.; Jaber, F.; Pinel, C.; Djakovitch, L. J. Organomet.
Chem. 2009, 694, 3222e3231.
20. Makarov, M. V.; Rybalkina, E. Y.; Roeschenthaler, G.-V.; Short, K. W.; Timofeeva,
T. V.; Odinets, I. L. Eur. J. Med. Chem. 2009, 44, 2135e2144.
21. Vicario, J.; Aparicio, D.; Palacios, F. J. Org. Chem. 2009, 74, 452e455.
22. Surendra, K.; Srilakshli-Krishnaveni, N.; Sridhar, R.; Rama-Rao, K. Tetrahedron
Lett. 2006, 47, 2125e2127.
NMR (62.9 MHz, MeOD): d: 132.04 (CqeC6H4), 129.90 (CqeC6H4),
129.52 (CHeC6H4), 128.84 (CHeC6H4H), 128.31 (CHeC6H4), 127.88
(CHeC6H4), 54.08 (CH2N), 52.82 (CH2N), 51.01 (CH2N), 26.53 (CH2),
24.18 (d, J¼136.94 Hz, CH2P). 31P NMR (101 MHz, MeOD):
d: 11.39.
Elemental Analysis: calcd: C, 54.77; H, 6.69; N, 5.81; O, 19.90; P,
12.84; found: C, 54.73; H, 6.65; N, 5.78; P, 12.81.
23. Chang-Eun, Y.; Mi-Jeong, K.; Moon-Kim, B. Tetrahedron 2007, 63, 904e909.
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2010, 66, 5373e5377.
€
€
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9548e9555.
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I. L. C. R. Chim. 2010, 13, 964e970.
Compound 4f was obtained as yellow oil (100%). C10H16NO3P
(229.21). FT-IR (KBr) (cmꢂ1): 3600e3280m (
n
NeH); 2902e2850s
C]C); 1482e1440m
PeO, PeC); 765w ( C-
29. Matveeva, E. V.; Shipov, A. E.; Odinets, I. L. Phosphorus, Sulfur and Silicon Relat.
(n
CeH); 2700e2560m
(nOeH); 1644m (n
Elem. 2011, 186, 698e706.
30. Matveeva, E. V.; Shipov, A. E.; Petrovskii, P. V.; Odinets, I. L. Tetrahedron Lett.
2011, 52, 6562e6565.
31. Pelaprat, N.; Rigal, G.; Boutevin, B. Eur. Polym. J. 1996, 32, 1189e1197.
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34. Odinets, I. L.; Matveeva, E. V. Russ. Chem. Rev. 2012, 81, 221e238.
(d
CeH), 1248e1180s ( P]O), 1167e1012m (
n
n
n
H), 710e685s (mono-substituted benzene ring). 1H NMR (250 MHz,
MeOD):
CH2NH), 2.56 (s, NH), 1.85e1.62 (m, 2H, CH2P). 13C NMR (62.9 MHz,
MeOD): : 137.57 (CqeC6H5), 130.03 (CHeC6H5), 129.80 (CHeC6H5),
d: 7.36e7.12 (m, 5H, C6H5), 2.95e2.85 (m, 6H, C6H5CH2 and
d