Cyclization of C-phosphorylated (PIII) arylformamidines to 3H-1,3-benzazaphospholes

Article abstract of DOI:10.1016/j.tet.2011.08.007

A synthesis of 3H-1,3-benzazaphospholes starting from C-phosphorylated P(III) arylformamidines has been developed. Electron-donating substituents were found to enhance markedly the rate of the cyclization, with substituents at the meta position having the greatest effect. A plausible mechanism of the cyclization was proposed based on DFT calculations.

Full text of DOI:10.1016/j.tet.2011.08.007

Tetrahedron 67 (2011) 7748e7758
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Cyclization of C-phosphorylated (PIII) arylformamidines to 3H-1,3-
benzazaphospholes
Anatolyi Marchenko a, Heorgii Koidan a, Anastasiya Hurieva a, Anatolyi Merkulov a, Aleksandr Pinchuk a,
,
b
c
c
Aleksandr Yurchenko a, Alexander B. Rozhenko a , Peter G. Jones , Holger Thonnessen ,
€
,
Aleksandr Kostyuk a
*
a Institute of Organic Chemistry, National Academy of Sciences of Ukraine, Murmanska 5, Kyiv-94 02094, Ukraine
Fakultat fur Chemie der Universitat Bielefeld, Postfach 10 01 31, 33501 Bielefeld, Germany
Institut fur Anorganische und Analytische Chemie, Technische Universitat Braunschweig, Hagenring 30, 38106 Braunschweig, Germany
b
€
€
€
c
€
€
a r t i c l e i n f o
a b s t r a c t
Article history:
A synthesis of 3H-1,3-benzazaphospholes starting from C-phosphorylated P(III) arylformamidines has
been developed. Electron-donating substituents were found to enhance markedly the rate of the cycli-
zation, with substituents at the meta position having the greatest effect. A plausible mechanism of the
cyclization was proposed based on DFT calculations.
Received 9 February 2011
Received in revised form 14 July 2011
Accepted 2 August 2011
Available online 7 August 2011
Ó 2011 Elsevier Ltd. All rights reserved.
Keywords:
3H-1,3-Benzazaphosphole
C-Phosphorylated arylformamidines
Cyclization
DFT
Reaction energy
Activation barrier
1. Introduction
4b, prepared by the reaction of dimethylamine with N,N-dimethyl-
N0-p-tolylcarbamimidoyldibromophosphine, transformed into the
3H-1,3-Benzazaphospholes have been little studied, but repre-
sent a class of potential organophosphorus ligands. The main ap-
proach to 3H-1,3-benzazaphospholes is based on alkylation of 1H-
1,3-benzazaphospholes, whose syntheses have been much better
developed.1 Thus, 1H-1,3-benzazaphospholes bearing hydrogen at
the nitrogen atom are easily lithiated with tert-butyl lithium to give
stable lithium phospholides. They can be alkylated at the phos-
phorus atom by soft electrophiles, such as alkyl halides providing
3H-1,3-benzazaphospholes. Bulkier substituents at position 2 fa-
cilitate the alkylation at the phosphorus atom.2 It should be men-
tioned that 1H-1,3-benzazaphospholes are aromatic compounds, in
contrast to 3H-1,3-benzazaphospholes.3
corresponding 3H-benzazaphosphole in vacuum distillation
123e125 ꢀC/0.03 Torr.5 The scope of the method was limited by the
poor accessibility of C-phosphorylated arylformamidines of type 4
and for a long time remained unexplored. Further investigations
became possible when a new and original method was found for
the synthesis of PIII-phosphorylated N-arylformamidines bearing
substituents both at the aromatic nucleus and at the phosphorus
atom.6
The objective of the current work is an experimental and the-
oretical study of factors influencing the cyclization of C-phos-
phorylated N-arylformamidines to 3H-1,3-benzazaphospholes.
Some 3H-1,3-benzazaphospholes have been synthesized by the
reaction of alkyl(aryl)dichlorophosphines with dilithiated aldimine
prepared by treatment of phenyl isocyanide with tert-butyl lithium,
but the method is limited exclusively to 2-tert-butyl derivatives.4
Previously we showed that C-phosphorylated arylformamidine
2. Results and discussion
To study the reaction in detail, a series of phosphorylated ami-
dines 4 were prepared (Scheme 1), both with electron-donating
and electron-withdrawing substituents at the benzene ring (com-
pounds 4aem) and bulky substituents at the phosphorus atom
(compounds 4nep). Detailed synthetic procedures are described in
our previous work.6 New compounds 2d, 2fe2h, 3d, 3fe3h, and 4d,
4fe4h were synthesized analogously. Their physical constants and
* Corresponding author. Tel.: þ380 67 209 9273; fax: þ380 44 537 3253; e-mail
address: a.kostyuk@enamine.net (A. Kostyuk).
0040-4020/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2011.08.007

A. Marchenko et al. / Tetrahedron 67 (2011) 7748e7758
7749
spectroscopic properties are given in the Experimental part. The list
of synthesized compounds is given in Table 1.
infra), are distilled in vacuo intact, and do not transform into 3H-
1,3-benzazaphospholes.
R'
N
P(NMe2)3
NMe2
4 a-p
+
-HNMe2
P
5 (5') a-p
R
Scheme 2. Synthesis of 3H-1,3-benzazaphospholes 5.
Noteworthy, while the phenyl-derivative 4a can be distilled
without change, distillation of naphthyl-substituted amidine 4m
caused complete transformation into the corresponding benzaza-
phosphole 5m. Thus, the ease of cyclization depends on the nature
of the substituent and its position in the benzene ring.
To make a preliminary assessment of the propensity of C-
phosphorylated arylformamidines 4 to cyclization, we heated their
benzene solutions in a sealed tube at 170 ꢀC, monitoring the re-
actions by 31P NMR spectroscopy after 0.5 and 15 h. Amidines 4b (4-
methyl) and 4h (3-Me) completely converted to 5b and 5h, re-
spectively. In contrast, only partial transformation was found for
isomer 4f (2-methyl), probably because it has only one free ortho
position at the benzene ring. In the most cases, along with the
cyclization, a competitive reaction leading to the formation of
hexamethylphosphorus triamide takes place (Scheme 2, Table 2).
Scheme 1. Synthesis of the starting materials 4aep.
Table 1
Substitution patterns in compounds 1e5
Entry
R
R0
Entry
R
R0
a
b
c
d
e
f
NMe2
NMe2
NMe2
NMe2
NMe2
NMe2
NMe2
NMe2
H
i
j
NMe2
NMe2
NMe2
NMe2
NMe2
5-IMIDa
t-Bu
3-Br
4-Me
4-OMe
4-NMe2
4-CF3
2-Me
2-Cl
3-OMe
3-NMe2
3-CF3
2,3-(CH)4
H
k
l
m
n
o
p
Table 2
Ratio of signal intensities of P(NMe2)3 and compounds 5þ50 after heating 4 in
a sealed tube at 170 ꢀ
C
g
h
H
H
4/5,50
0.5 h
15 h
4/5,50
0.5 h
15 h
3-Me
1-Ad
a
2-Dimethylamino-1-methylimidazol-5-yl.
a
b
c
d
e
f
0/0
3/6
0/0
4/20
0/0
0/0
0/0
13/30
33/67
21/64
30/70
0/0
h
j
k
l
m
o
p
1/11
4/96
0/100
0/0
0/100
0/0
20/80
Compound 4b was studied by single-crystal X-ray diffraction
(Fig. 1). It exists in the solid state as the Z-isomer. The aromatic ring
is rotated relative to the N1PN2 plane by 61.9ꢀ. While the C8eP1
bond is elongated (1.888 A), the C8eN2 and C8eN1 bond lengths
(1.365A and 1.290A, respectively) are typical for single and double
bonds.
0/0
15/48
36/42
0/0
0/0
g
0/0
ꢀ
ꢀ
ꢀ
The introduction of an electron-withdrawing trifluoromethyl
group at the para or ortho positions of the benzene ring (com-
pounds 4e,l) hampers the cyclization. For instance, heating ben-
zene solutions of amidines 4e,l (4- and 3-CF3) at 200 ꢀC for 15 h
does not afford even traces of benzazaphospholes 5e,l.
The results obtained allow us to rank the substituents in the fol-
lowing order by decreasing property to promote the cyclization: m-
Me2NC6H4>>a-naphthyl>m-MeOC6H4>p-Me2NC6H4>m-MeC6H4>
p-MeC6H4>p-MeOC6H4>m-BrC6H4>o-ClC6H4>o-MeC6H4>C6H5>>
p-F3CC6H4zm-F3CC6H4. Thus, with the exception of 5e,l, heating
amidines 4 in vacuum at 170 ꢀC was found to be a convenient ap-
proachforthepreparativesynthesisofbenzazaphospholes5(Table 3).
All the isolated 2-dimethylamino-3H-1,3-benzazaphospholes 5 are
bright yellow crystalline compounds, stable in an inert atmosphere.
The structure and composition were proved by standard methods,
such as 1H, 31P, and 13C NMR spectroscopy.
For meta-substituted amidines 4 the cyclization can afford
mixtures of isomeric benzazaphospholes 5 and 50. As these com-
pounds are moisture-sensitive, crude reaction mixtures were
treated with selenium to afford the corresponding benzazaphosp-
hole mixtures 6þ60, which were separated chromatographically
into the individual isomers. Thus, compounds 6h, 60h, 6j, 60j, 60i, 6l,
and 60l were isolated individually. Benzazaphospholes 6h, e, l and
60l were reduced back to the pure benzazaphospholes 5 by boiling
them with sodium in toluene (Scheme 3). Compounds 60h and 6j
were reduced by hexamethylphosphorus triamide.
Fig. 1. Crystal structure of the amidine 4b.
It was found that amidine 4k, containing a Me2N group at the
meta position of the benzene ring, cannot be separated in pure form
and cyclized spontaneously to 5k. At 20 ꢀC formation of 4k can be
monitored spectroscopically (dp¼95.9 ppm), but after 10 min only
the signal of the corresponding benzazaphosphole 5k
(
dp¼59.5 ppm) was present (Scheme 2). Other C-phosphorylated
amidines 4, with the exception of the naphthyl derivative 4m (vide

7750
A. Marchenko et al. / Tetrahedron 67 (2011) 7748e7758
Table 3
Reaction conditions and yields of benzazaphospholes 5þ50
4
T, ꢀC
Time, min
Pressure, Torr
Yield 5þ50, %
(ratio of 6 to 4 isomers)
a
b
c
d
ea
f
g
h
i
220
220
200
200
230
220
220
200
220
200
20
230
150
200
250
250
30
20
20
10
30
30
30
30
20
10
10
30
10
10
1 h
1 h
150
150
20
76
88
83
78
40
60
41
91 (1:1)
75 (1:2)
77 (10:1)
73
56 (1:3)
89
61
0
Scheme 5. Synthesis of benzazaphospholes 5o,p.
20
The influence of steric effects at the phosphorus atom was studied
by an example of amidines 4nep. Amidine 4n bearing the electron-
donating imidazol-2-yl substituent, undergoes a facile thermal cycli-
zation. Thus, even its vacuum distillation is accompanied by a partial
(9%) cyclization affording benzazaphosphole 5n. In contrast, amidines
4o,p bearing bulky substituents (t-Bu, 1-Ad) at the phosphorus atom
do not give benzazaphospholes even on prolonged heating (250 ꢀC/
20 h). Compounds 4o,p react with phosphorus trichloride affording
chlorophosphines 8o,p, which are viscous liquids, distillable at high
vacuum. It is worth noting that compounds 8o,p are the first known
representatives of phosphorusacid chlorides bearing a C-formamidine
residue. In a benzene solution in the presence of triethylamine these
compounds undergo cyclization affording benzazaphospholes 5o,p in
68%and82%yields, respectively. Thereactionproceedsprobablyviaan
SN2-mechanism at the phosphorus atom.
150
150
150
20
150
20
760
150
0.2
j
k
la
m
n
o
p
20
150
150
0
a
Experiments were carried out with catalytic amounts of salts (vide infra).
R
N
P
Se
N
P
NMe2
NMe2
NMe2
+
5 + 5'
Na
NMe2
Se
Se
R
2.1. Theoretical investigation of the reaction
6'
6
Scheme 3. Separation of isomers 5 and 50.
One of the most reliable methods of elucidating a mechanism of
cyclization is the complete quantum-chemical investigation of a po-
tential energy surface (PES) along the reaction pathway. Plausible
cyclizationroutesforamidines4aregiveninScheme 6. The formation
The corresponding sulfur derivative 7 was prepared by the one-
pot method given in Scheme 4; its identity was confirmed by
single-crystal X-ray investigation (Fig. 2). There are two in-
dependent molecules in the asymmetric unit, but these are closely
of 5 is overall exothermic (
ꢁ9.4 kcal/mol, respectively, approximation level II, see Details of
Calculations). The absence of major differences in the E values in-
DE for 5a, 5k, and 5l are ꢁ10.0, ꢁ11.2, and
ꢀ
similar (r.m.s. deviation of all non-H atoms is 0.16 A overall and only
ꢀ
D
0.05 A if ethyl and methyl groups are neglected). Molecular di-
dicates that the rate of the cyclization is probably determined not by
thermodynamic stability of the final reaction products, but by the
different activation energies in the cyclization reactions. In particular,
for considered concerted cyclization process, the PeCarom bond is
formedwiththeeliminationofdimethylamine(Scheme6). According
to our calculations, such a pathway implies high activation energies
for transition states 9. Moreover, the activation energies in cases 9a
mensions may be regarded as normal.
N
1. PBr3, Et3N
N
NMe2
NEt2
P
2.Et2NH MeO
NMe2
MeO
S
3.S
7
Scheme 4. Synthesis of benzazaphosphole 7.
N
N
N
N
N
P
P
N
X
X
N
H
N
9
4
-HNMe2
N
N
P
X
N
5
-HNMe2
N
N
N
N
H
P
P
X
N
X
N
H
N
N
Fig. 2. Thermal ellipsoid representation (50% level) of one of the two independent
molecules of compound 7 in the crystal. Bond lengths and angles at phosphorus for
ꢀ ꢀ
10
11
both independent molecules (A, ): PeN(3) 1.6545 (15), 1.6452 (15), PeC(8) 1.792 (2),
1.797 (2), PeC(1) 1.865 (2), 1.8681 (19), PeS 1.9396 (7), 1.9408 (7); N(3)ePeC(8) 112.25
(8), 112.39 (8), N(3)ePeC(1) 106.19 (8), 107.04 (8), C(8)ePeC(1) 88.23 (9), 88.67 (9),
N(3)ePeS 114.38 (7), 114.92 (6), C(8)ePeS 115.60 (6), 115.07 (6), C(1)ePeS 117.25 (6),
115.79 (6).
Scheme 6. Some mechanisms suggested for cyclization of 4.

A. Marchenko et al. / Tetrahedron 67 (2011) 7748e7758
7751
E1
(1)
(X¼H) and 9k (X¼NMe2) are almost equal (55.2 and 55.4 kcal/mol,
13/14 þ Me2NH þ
D
respectively), which do not agree with the different reaction rates
found for 4a and 4k. The reaction via the intermediary cyclic product
10 (X¼H) is unlikely because 10 does not correspond to a real energy
minimum on the PES. Proton transfer from the carbon atom to the
phosphorus atom leading to structure 11 (X¼H) is also characterized
by very high activation energy (58.6 kcal/mol). The only possibility
that excludes high activation energies is protonation of the nitrogen
atomatthebis(dimethylamino)phospinogroupwiththeformationof
intermediary products 13, followed by elimination of dimethylamine
and cyclization (Scheme 7).
We have investigated the cyclization by a concerted mechanism
calculating total energy values for 13a along the IRC. Shortening the
CipsoeP distance is accompanied by increasing the PeNHMe2 dis-
tance, forming the cyclic structure 18, a loosely bound complex of
14a with dimethylamine (Scheme 8). Probably, the reaction begins
with inversion around the imine nitrogen atom with the formation
of the isomeric cation 16 (see Supplementary data for more
structural details and total energy values). Cation 16, which can also
be considered as a phosphenium cation 15a stabilized by a mole-
cule of dimethylamine, converts into a more stable form 17, where
the p-system of the aromatic ring formally donates into the vacant
H
N
P
H
N
p-orbital at the phosphorus atom. The corresponding transition
state TS2 possesses the highest total energy at the reaction co-
ordinate (þ24.0 kcal/mol for 13a, calculation level II), and in fact
corresponds to the PeN bond dissociation. Finally, the last stage is
the cyclization with the formation of 18. The corresponding tran-
sition state TS3 is 16.7 kcal/mol higher in energy with respect to
13a. Thus, according to the calculations, the cyclization process of
13a is accompanied by a gradual weakening of the PeN bond until
it completely dissociates. Then 18 loses a dimethylamine molecule
giving the cyclic cation 14 (Scheme 7). According to calculations
based on the total energy values and ignoring the influence of the
entropy factor, this process also seems to be slightly endothermic
N
P
N
+
N
H
N
4
N
N
X
X
12
13
-HNMe
N
2
N
5
P
+
-H
X
H
N
14
Scheme 7.
(
D
E3¼3.3 and 7.4 kcal/mol). The shift of the reaction equilibrium to
the right is probably promoted by the removal of gaseous dime-
thylamine from the reaction mixture by heating under reduced
pressure.
It should be noted that the proton transfer reaction proceeds
with a low activation energy (see Supplementary data) and the
products 13 are only slightly less favorable compared to derivatives
12 (by 2.5 kcal/mol for X¼NH2 and 1.2 kcal/mol for X¼H) and are
characterized by almost identical total energies for X¼CF3. Thus, 13
can be considered as the first intermediate structure in the studied
cyclization reaction.
H
N
H
N
N
H
P
N
P
N
N
N
2.2. Cyclization mechanisms
N
13a
18
Our calculations indicate that cleavage of dimethylamine from
protonation products 13 and the subsequent cyclization to the in-
termediate cyclic cations 14 (reaction (1)) are overall endothermic
reactions. However, it should be noted that cyclization of 13k into
TS1
TS3
E1¼þ8.0 kcal/
N
H
N
N
H
14k (X¼NMe2) requires considerably less energy (
D
P
P
H
N
TS2
mol), than in the formation of 14a (X¼H) and 14l (X¼CF3) (Fig. 3)
with the endothermic reaction energy values 21.8 and 24.0 kcal/
mol, respectively (the detailed quantitative description of the two-
step cyclization reaction of 13a the reader can find in the
Supplementary data).
N
N
N
N
16
17
Scheme 8. Concerted mechanism of cyclization.
Cyclization products 14 (Fig. 3) are characterized by a mutual cis-
orientation of the hydrogen atom in the six-membered ring and the
dimethylamino group at the phosphorus atom (the corresponding
trans-isomers are less stable by 2.3e2.6 kcal/mol). It should be noted
that 14a, 14k, and 14l are markedly different in CipsoeP bond length
(Cipso indicates the carbon atom, attacked by or bound to the phos-
phorus atom). The shortest CipsoeP distance has been found for 14k
ꢀ
(1.982 A), which is, however, still noticeably longer than the corre-
ꢀ
sponding value in the final product 5k (1.834 A).
On going to 14a and 14l the CipsoeP bond elongates even more
ꢀ
(to 2.056 and 2.067 A, respectively). In the last two cyclic cations the
positive charge is to a greater extent localized on the phosphorus
atom, and they can be better represented as donoreacceptor
complexes of aminophosphenium cations with the p-system of the
aromatic ring. In contrast, the experimentally observed easy cycli-
zation of 4k we refer to the high relative stability of the in-
termediate cyclic cation 14k, that is probably referred to the
mesomeric equilibrium shown in Scheme 9.
Fig. 3. VMD views for optimized (RI-BP86/TZVP) structures 14a, 14k, and 14l.

7752
A. Marchenko et al. / Tetrahedron 67 (2011) 7748e7758
salts (vide supra), the rate of the cyclization on heating them neat
with the salts at 170 ꢀC strongly depends on the nature of the anion.
The formation of benzazaphospholes 5e (4-CF3) and 5 (50)l (3-CF3)
was complete in 10 h for the chloride salt and in 10 min/5 min for
the triflate salt. We therefore postulate different catalytic effects for
these salts. The reaction can be accelerated by the substitution of
the dimethylamino group with the nucleophilic chloride anion
forming intermediary phosphorus chlorides of type 8 (Scheme 5) or
product of its protonation 20. As it was already mentioned above,
the most energy-consuming step in the cyclization of 4 is the
elimination of dimethylamine. Similarly to 4a and 12a, no direct
cyclization pathways have been found for 8a and 20a, therefore the
PeCl bond dissociation is again an obliged reaction stage. The direct
comparison of 12a (12, X¼H) and 20a as the reactants yielding 14a,
demonstrates no thermodynamic advantages for HCl elimination
Scheme 9. Stabilization of 14k.
2.3. Acid catalysis
As noted above, for the initiation of the reaction protonation of
amidine 4 is necessary. Probably, traces of acid are present in the
solution, for example, as dimethylammonium salts (reaction (2)).
(Eq. 3,
leaving group (Eq. 4,
thylammonium chloride as the catalyst, the formation of benza-
zaphospholes is mainly accelerated by increasing of the
corresponding protonated forms 12 and 13.
D
E3¼26.8 kcal/mol, Level I) compared to dimethylamine as
D
E4¼25.9 kcal/mol). Therefore, using trie-
4 þ Me2NHþ2 /12 þ Me2NH þ
D
E2
(2)
The protonation proceeds most easily for 12k (
mol), then the exothermicity consistently decreases in going to 12a
D
E2¼ꢁ26.0 kcal/
E3
(3)
(D
E4¼ꢁ20.6 kcal/mol) and 12l (
D
E4¼ꢁ15.7 kcal/mol). Therefore, all
20a/14a þ HCl þ
D
amidines 4 are stronger bases than dimethylamine. For facilitating
the reaction it is important that the cyclic products 14a,k,l are
weaker bases than the corresponding amidines 4a,k,l. The latter are
exothermically protonated by the former initiating a new cycle of
cyclization. The complete process is depicted in Scheme 10.
12a/14a þ Me2NH þ
D
E4
(4)
The increased reactivity of 4e,l in the cyclization reaction by
using ammonium triflate as a catalyst, can be explained by more
pronounced dissociation of the PeO bond resulting from the high
stability of the isolated triflate anion in nonpolar solvents, such
as benzene. In this case a reactive phosphenium cation7 is
formed. The positively charged phosphorus attacks the electron-
rich carbon atom in the aromatic ring resulting in the cyclic
products 14. A similar mechanism we recently envisaged for the
formation of tris[2-(dimethylamino)-1-methyl-1H-imidazol-5-yl]
phosphine selenide.8
14
-5
4
4
12
18
5
13
14
-12
Scheme 10.
In contrast to the reaction with the dimethylammonium cation,
the greatest exothermic effect was observed in the case of depro-
tonation of 14l by amidine 4l (ꢁ25.2 kcal/mol), and the smallest
effect for the pair 14k and 4k (ꢁ13.7 kcal/mol). Reaction of 14a with
4a leading to the formation of 13a and 5a is characterized by the
intermediate
D
E2 value (ꢁ22.8 kcal/mol). The observed trend is not
3. Conclusion
unexpected and determined by the relative stabilities of cyclic in-
termediates 14: the most stable is 14f and the least stable is 14l. An
additional remark should be made about Scheme 9. Deprotonation
of the CH proton can also proceed via cyclic salt 19, which is the
protonated form of 5a and is significantly (by 21.1 kcal/mol) more
stable than 14a. Therefore, the former can stand as an intermediate
in the studied cyclization processes.
We have developed
a convenient approach to 3H-1,3-
benzazaphospholes starting from readily available C-phosphory-
lated arylformamidines. The proposed method allows varying
substituents both at the aryl ring and at the phosphorus atom. It has
been shown that electron-donating substituents, especially at the
meta position of the aromatic ring, markedly enhance the cycliza-
tion, whereas electron-withdrawing substituents hampers the re-
action. Sterically demanding substituents at the phosphorus atom
also have a negative effect on the cyclization. The first represen-
tatives of chlorophosphines bearing a formamidine substituent
were synthesized. These compounds can also be used for the syn-
thesis of 3H-1,3-benzazaphospholes. Quantum chemical calcula-
tions let us to leave out the direct cyclization pathways for amidines
4 and to propose an acid catalyzed concerted mechanism pro-
ceeding via intermediate cyclic cations. The addition of ammonium
chloride or triflate to the reaction mixtures significantly increases
the cyclization rate due to the higher concentration of the pro-
tonated forms of 4 and (in the case of triflate) by intermediary
formation of highly reactive phosphenium cation which further
cyclizes to benzazaphosphole 5.
H
H
N
NMe2
NMe2
N
NMe2
NMe2
N
P+
+
P
NMe2
19a
NMe2
P
Cl
Cl
R
R
20
8
2.4. Cyclization of 4b,e,l in the presence of ammonium salts
Taking into account the proposed reaction mechanism dis-
cussed above, we decided to study the cyclization of amidines 4 to
benzazaphospholes 5 in the presence of catalytic amounts of trie-
thylamine salts of hydrochloric and triflic acids. Heating a mixture
of amidine 4b and triethylammonium chloride or triethylammo-
nium triflate (5 mol %) in benzene at 170 ꢀC resulted in formation of
benzazaphosphole 5b already in 2e5 min. In the both cases the
ratio of hexamethylphosphorus triamide to benzazaphosphole was
the same as in the experiments without catalyst (Table 2). While
amidines 4e,l (4- and 3-CF3) do not cyclize without addition of the
3.1. Calculation details
All the structures corresponding to the energy local minima were
fully optimized without symmetry constraints using the TURBO-
MOLE 6.02 program packet9 The RI-BP86//TZVP approach10,11 was

A. Marchenko et al. / Tetrahedron 67 (2011) 7748e7758
7753
used for geometry optimization. The used TZVP bases were the
variant of TZV triple-zeta basis sets12 extended by adding polariza-
tion functions. This approximation is noticed in the text as Level I. A
fine SCF convergence criterion (SCFConv¼1.0ꢂ10ꢁ8 Hartree) was
used for the geometryoptimization. The finest grids wereused forall
calculations (grid¼5). Cartesian coordinates for all optimized
structures are collected in the Supplementary data. The vibration
frequencies calculated numerically checked the optimized struc-
tures to be the real minima in energy. All the IRC calculations were
carried out using the GAUSSIAN-03 program set13 within the DFT
approximation. A hybrid functional B3LYP14,15 was chosen, in com-
bination with the 6-31G* basis sets16 (Level II). The loose geometry
convergence and middle integration grid was used for a higher
performance. All the transition states were localized at approxi-
mation Level II using the structures derived from the IRC calcula-
tions, corresponding to energy maxima, as starting geometries. The
tightoptimization convergence criteria and fine grid (Int¼UltraFine)
were used for the calculations. For comparison, all the local minima
structures were recalculated using approximation Level II. The cal-
culations of the molecular vibrations were performed using Level II,
calculating analytically the first and second derivatives. These cal-
culations yielded no imaginary vibration for the local minima and
one imaginary vibration for every transition state. The program
VMD17 was used for the graphical presentation of the optimized
structures.
[Found: C, 27.30; H, 2.96; N, 7.05; P, 7.82. C9H11Cl4N2PSe requires C,
27.10; H, 2.78; N, 7.02; P, 7.76].
4.1.4. N,N-Dimethyl-N0-(3-methylphenyl)-P-(trichloromethyl)phos-
phonoselenoic diamide 2h. Yield 93.6%, white crystals, mp
119e120 ꢀC (Et2O); 1H NMR (300 MHz, CDCl3)
d 7.21 (1H, t,
J¼7.50 Hz, 5-H), 6.94e6.90 (3H, m, 2,4,6-H), 5.12 (1H, d, J¼11.0 Hz,
NH), 3.10 (6H, d, J¼10.5 Hz, PNMe2), 2.36 (3H, s, 3-Me); 13C NMR
(125 MHz, CDCl3)
d 139.42, 138.49, 129.29, 124.10, 120.24 (d,
J¼7.5 Hz), 116.33 (d, J¼6.3 Hz), 98.75 (d, J¼65.4 Hz), 39.83 (d,
J¼4.0 Hz), 21.60; 31P NMR (81 MHz, CDCl3)
d 70.2. MS (APCI): m/
z¼377 [Mꢁ1]. [Found: C, 31.86; H, 3.86; N, 7.45; P, 8.09.
C10H14Cl3N2PSe requires C, 31.73; H, 3.73; N, 7.40; P, 8.18].
4.1.5. 1,1-Bis(dimethylamino)-N0-[4-(dimethylamino)phenyl]-N,N-di-
methyl phosphinecarboximidamide selenide 3d. Yield 94%, yellow
crystals, mp 88e89 ꢀC (pentane); 1H NMR (500 MHz, CDCl3)
d 6.72
(2H, d, J¼7.0 Hz, 2,6-H), 6.68 (2H, d, J¼6.5 Hz, 3,5-H), 2.89 (6H, s,
CNMe2), 2.84 (6H, s, 4-NMe2), 2.80 (12H, d, J¼10.0 Hz, PNMe2); 13
C
NMR (125 MHz, CDCl3)
d
151.85 (d, J¼153.4 Hz), 146.40, 140.20 (d,
J¼21.4 Hz), 121.58, 113.36, 41.32, 41.19 (d, J¼2.5 Hz), 38.1 (d,
J¼1.25 Hz); 31P NMR (81 MHz, CDCl3)
d
67.5. MS (APCI): m/z¼390
[Mþ2]. [Found: C, 46.13; H, 7.43; N, 17.95; P, 8.10. C15H28N5PSe re-
quires C, 46.39; H, 7.27; N, 18.03; P, 7.98].
4.1.6. 1,1-Bis(dimethylamino)-N,N-dimethyl-N0-(2-methylphenyl)
phosphinecarboximidamide selenide 3f. Yield 95%, light yellow
crystals, mp 86e87 ꢀC (pentane); 1H NMR (500 MHz, CDCl3)
4. Experimental section
4.1. General
d
7.10e7.05 (2H, m, 3,5-H), 6.84 (1H, t, J¼7.0 Hz, 4-H), 6.64 (1H, d,
J¼7.5 Hz, 6-H), 2.83 (12H, d, J¼11.0 Hz, PNMe2), 3.84 (6H, s, CNMe2),
2.18 (3H, s, 4-Me); 13C NMR (125 MHz, CDCl3)
152.96 (d,
d
Syntheses and spectral characteristics of compounds
2aec,e,ieh; 3aec,e,ieh; 4aec,e,i,j,leh are given in our previous
work.6 Previously unknown compounds 2d, feh, 3d, feh, and 4d,
feh were synthesized by analogy.
J¼150.9 Hz), 149.20 (d, J¼21.4 Hz), 129.92, 127.96, 125.81, 121.59,
119.16, 40.93 (d, J¼4.0 Hz), 38.12 (d, J¼2.5 Hz), 18.92; 31P NMR
(81 MHz, CDCl3)
46.53; H, 6.92; N, 15.35; P, 8.40. C14H25N4PSe requires C, 46.80; H,
7.01; N, 15.59; P, 8.62].
d
66.2. MS (APCI): m/z¼361 [Mþ2]. [Found: C,
4.1.1. N0-[4-(Dimethylamino)phenyl]-N,N-dimethyl-P-(tri-
chloromethyl)phosphonoselenoic diamide 2d. Yield 75%, white
4.1.7. N0-(2-Chlorophenyl)-1,1-bis(dimethylamino)-N,N-dimethyl-
crystals, mp 95e96 ꢀC (pentane); 1H NMR (300 MHz, CDCl3)
d
7.04
phosphinecarboximidamide selenide 3g. Yield 79%, light yellow
(2H, d, J¼9.0 Hz, 2,6-H), 6.71 (2H, d, 3,5-H), 4.88 (1H, d, J¼11.4 Hz,
crystals, mp 77e78 ꢀC (pentane); 1H NMR (500 MHz, CDCl3)
d 7.28
NH), 3.09 (6H, d, J¼10.5 Hz, PNMe2), 2.91 (6H, s, 4-NMe2); 13C NMR
(1H, d, J¼8.0 Hz, 3-H), 7.12 (1H, t, 5-H), 6.84 (1H, t, J¼7.5 Hz, 6-H),
(125 MHz, CDCl3)
d
147.83, 127.65, 122.84 (d, J¼5.0 Hz), 113.59, 99.0
6.80 (1H, d, J¼8.0 Hz, 4-H), 2.91 (6H, s, CNMe2), 2.83 (12H, d,
(d, J¼62.8 Hz), 41.02, 39.95(d, J¼3.8 Hz); 31P NMR (81 MHz, CDCl3)
J¼11.0 Hz, PNMe2); 13C NMR (125 MHz, CDCl3)
d 152.43 (d,
d
72.8. MS (APCI): m/z¼408 [Mþ1]. [Found: C, 32.13; H, 4.09; N,
J¼145.9 Hz), 147.81 (d, J¼20.1 Hz), 129.25, 126.77, 124.68, 122.12,
10.25; P, 7.72. C11H17Cl3N3PSe requires C, 32.42; H, 4.20; N, 10.31; P,
7.60].
121.44, 40.80 (d, J¼2.5 Hz), 38.25 (d, J¼5.0 Hz); 31P NMR (81 MHz,
CDCl3)
d 66.4. [Found: C, 41.03; H, 6.02; N, 14.35; P, 8.10.
C13H22ClN4PSe requires C, 41.12; H, 5.84; N, 14.75; P, 8.16].
4.1.2. N,N-Dimethyl-N0-(2-methylphenyl)-P-(trichloromethyl)phos-
phonoselenoic diamide 2f. Yield 83%, white crystals, mp 111e113 ꢀC
4.1.8. 1,1-Bis(dimethylamino)-N,N-dimethyl-N0-(3-methylphenyl)
phosphinecarboximidamide selenide 3h. Yield 90%, light yellow
crystals, mp 104e105 ꢀC (pentane); IR (KBr) 2880, 1573, 1480, 1437,
(Et2O); 1H NMR (300 MHz, CDCl3)
d
7.25 (1H, d, J¼8.4 Hz, 3-H),
7.21e7.16 (2H, m, 5,6-H), 7.00 (1H, dt, J¼7.5, 1.2 Hz, 4-H), 5.11 (1H, d,
J¼11.0 Hz, NH), 3.09 (6H, d, J¼10.5 Hz, PNMe2), 2.29 (3H, s, 2-Me);
1222, 1179, 1148, 972, 691, 601 cmꢁ1 1H NMR (500 MHz, CDCl3)
;
13C NMR (125 MHz, CDCl3)
d
137.03, 130.89, 127.56 (d, J¼8.8 Hz),
d
7.09 (1H, t, J¼7.5 Hz, 5-H), 6.71 (1H, d, J¼7.5 Hz, 6-H), 6.58 (1H, s,
127.13, 123.39, 119.00 (d, J¼3.8 Hz), 99.01 (d, J¼65.4 Hz), 39.89 (d,
2-H), 6.56 (1H, d, J¼7.5 Hz, 4-H), 2.87 (6H, s, CNMe2), 2.79 (12H, d,
J¼5.0 Hz), 17.65; 31P NMR (81 MHz, CDCl3)
d 69.8. MS (APCI):
J¼11.8 Hz, PNMe2), 2.29 (3H,s, 3-Me); 13C NMR (125 MHz, CDCl3)
m/z¼408 [Mþ1]. [Found: C, 31.83; H, 3.92; N, 7.25; P, 8.10.
d
151.48 (d, J¼148.4 Hz), 149.97 (d, J¼20.1 Hz), 138.09, 128.22,
C10H14Cl3N2PSe requires C, 31.73; H, 3.73; N, 7.40; P, 8.18].
122.29, 121.03, 117.39, 41.30 (d, J¼2.5 Hz), 38.1 (d, J¼4.0 Hz), 21.5;
31P NMR (81 MHz, CDCl3)
d
66.6. MS (APCI): m/z¼361 [Mþ2].
4.1.3. N0-[2-Chlorophenyl]-N,N-dimethyl-P-(trichloromethyl)-phos-
phonoselenoic diamide 2g. Yield 69%, white crystals, mp 90e91 ꢀC
[Found: C, 46.39; H, 7.09; N, 15.45; P, 8.36. C14H25N4PSe requires C,
46.80; H, 7.01; N, 15.59; P, 8.62].
(Et2O); 1H NMR (300 MHz, CDCl3)
d
7.44 (1H, dd, J¼8.1, 1.5 Hz, 3-H),
7.39 (1H, dd, J¼8.1, 1.5 Hz, 6-H), 7.24 (1H, dt, J¼8.1, 1.5 Hz, 5-H), 6.99
4.1.9. 1,1-Bis(dimethylamino)-N0-[4-(dimethylamino)phenyl]-N,N-di-
(1H, dt, J¼7.8, 1.2 Hz, 4-H), 6.04 (d, 1H, J¼10.8 Hz, NH), 3.08 (6H, d,
methylphosphinecarboximidamide 4d. Yield 93%, yellow oil, bp
J¼10.8 Hz, PNMe2); 13C NMR (125 MHz, CDCl3)
d
135.76, 129.52,
155e157 ꢀC/0.05 Torr; 1H NMR (500 MHz, C6D6)
d 7.06 (2H, d,
127.82, 123.55 (d, J¼8.8 Hz), 123.34, 118.52 (d, J¼4.0 Hz), 98.47 (d,
J¼9.0 Hz, 2,6-H), 6.77 (2H, d, J¼9.0 Hz, 3,5-H), 2.87 (6H, s, 4-NMe2),
J¼67.9 Hz), 39.8 (d, J¼3.8 Hz); 31P NMR (81 MHz, CDCl3)
d 70.0.
2.71 (6H, s, CNMe2), 2.65 (12H, d, J¼7.5 Hz, PNMe2); 13C NMR

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A. Marchenko et al. / Tetrahedron 67 (2011) 7748e7758
(125 MHz, C6D6)
d
162.50 (d, J¼23.9 Hz), 145.6, 142.8 (d, J¼2.5 Hz),
2), and then the product was distilled at 0.05 Torr. In the case of
compounds 4a,b,m,n the residue was extracted with hot hexane,
the solvent was evaporated and the residue was crystallized. In case
of compounds 4s,d,fej the residue was dissolved in benzene and an
equivalent of finely ground selenium was added. The reaction
mixture was refluxed for 2e5 h until oxidation of the P(III) com-
pound was complete. The reaction was monitored by 31P NMR. The
unreacted selenium was separated by filtration. The filtrate was
evaporated in vacuo. The residue was crystallized. The mixture of
selenides 6 and 60hej was separated chromatographically.
121.36 (d, J¼2.5 Hz), 113.8, 41.64 (d, J¼15.0 Hz) 41.32, 39.75 (d,
J¼7.5 Hz); 31P NMR (81 MHz, C6D6)
d 96.5. [Found: C, 58.13; H, 9.33; N,
22.55; P,10.10. C15H28N5P requires C, 58.23; H, 9.12; N, 22.64; P,10.01].
4.1.10. 1,1-Bis(dimethylamino)-N,N-dimethyl-N0-(2-methylphenyl)
phosphinecarboximidamide 4f. Yield 94%, light yellow oil, bp
140e143 ꢀC/0.05 Torr; 1H NMR (300 MHz, C6D6)
d 7.11 (1H, d,
J¼7.5 Hz, 3-H), 7.06 (1H, t, J¼7.2 Hz, 5-H), 6.80 (1H, t, 4-H), 6.72 (1H,
d, J¼7.5 Hz, 6-H), 2.68 (6H, br s, CNMe2), 2.51 (12H, d, J¼8.7 Hz,
PNMe2), 2.26 (3H, s, 2-Me); 13C NMR (125 MHz, C6D6)
d 161.21 (d,
J¼22.6 Hz), 150.68 (d, J¼1.3 Hz), 129.68, 127.59, 126.96, 119.96,
4.2.1. N,N,N0,N0-Tetramethyl-3H-1,3-benzazaphosphonole-2,3-
119.75, 41.29 (d, J¼15.1 Hz), 39.21 (d, J¼8.8 Hz), 18.99; 31P NMR
diamine 5a. Yield 76%, bright yellow crystals mp 52e54 ꢀC (pen-
(81 MHz, C6D6)
d
94.5. [Found: C, 60.13; H, 9.13; N, 20.15; P, 10.97.
tane), bp 143e146 ꢀC/0.05 Torr; 1H NMR (500 MHz, C6D6)
d 7.55
C14H25N4P requires C, 59.98; H, 8.99; N, 19.98; P, 11.05].
(1H, d, J¼8.0 Hz, 7-H), 7.49 (1H, m, 4-H), 7.20 (1H, t, J¼8.0 Hz, 6-H),
6.87 (1H, m, 5-H), 2.94 (3H, br s, 2-NMe2), 2.70 (3H, br s, 2-NMe2),
4.1.11. N0-(2-Chlorophenyl)-1,1-bis(dimethylamino)-N,N-dimethyl-
phosphinecarboximidamide 4g. Yield 99%, oil, bp 150e155 ꢀC/
2.31 (6H, d, J¼9.5 Hz, 3-NMe2); 13C NMR (125 MHz, C6D6)
d 175.90
(d, J¼21.4 Hz), 159.41 (d, J¼8.8 Hz), 131.12, 129.08 (d, J¼7.5 Hz),
0.05 Torr; 1H NMR (300 MHz, C6D6)
d
7.29 (1H, dd, J¼7.8, 1.5 Hz, 3-
129.08 (d, J¼25.2 Hz), 121.40 (d, J¼7.5 Hz), 119.73, 41.55 (d,
H), 6.92 (1H, dt, J¼7.5, 1.2 Hz, 5-H), 6.73 (1H, dd, J¼7.8, 1.5 Hz, 6-H),
J¼11.3 Hz), 40.20 (br s), 37.27 (br s); 31P NMR (81 MHz, C6D6)
d 61.0.
6.54 (1H, dt, J¼7.5, 1.5 Hz, 4-H), 2.74 (6H, s, CNMe2), 2.45 (12H, d,
[Found: C, 59.42; H, 7.45; N, 19.17; P, 13.85. C11H16N3P requires C,
59.72; H, 7.29; N, 18.99; P, 14.00].
J¼8.7 Hz, PNMe2); 13C NMR (125 MHz, C6D6)
162.31 (d, J¼27.7 Hz),
d
149.08 (d, J¼1.2 Hz), 129.01, 127.60, 124.22 (d, J¼1.2 Hz), 121.63 (d,
J¼1.2 Hz)119.83, 41.34 (d, J¼16.3 Hz), 38.97 (d, J¼8.8 Hz); 31P NMR
4.2.2. N,N,N0,N0,5-Pentamethyl-3H-1,3-benzazaphosphonole-2,3-
diamine 5b. Yield 88%, bright yellow crystals mp 107e108 ꢀC
(pentane); bp 145e147 ꢀC/0.05 Torr; 1H NMR (500 MHz, C6D6)
(81 MHz, C6D6)
d 93.8. [Found: C, 52.14; H, 7.45; N, 18.75; P, 10.23.
C13H22ClN4P requires C, 51.91; H, 7.37; N, 18.63; P, 10.30].
d
7.51 (1H, d, J¼7.5 Hz, 7-H), 7.32 (1H, br s, 4-H), 7.02 (1H, d,
4.1.12. 1,1-Bis(dymethylamino)-N,N-dimethyl-N0-(3-methylphenyl)
J¼8.0 Hz, 6-H), 2.94 (3H, br s, 2-NMe2), 2.76 (3H, br s, 2-NMe2), 2.35
phosphinecarboximidamide 4h. Yield 94%, bp 125e126 ꢀC/0.05 Torr;
(6H, d, J¼9.5 Hz, 3-NMe2), 2.16 (3H, s, 5-Me); 13C NMR (125 MHz,
1H NMR (300 MHz, C6D6)
d
7.08 (1H, t, J¼7.5 Hz, 5-H), 6.71e6.73
C6D6)
d
175.37 (d, J¼22.6 Hz), 157.18 (d, J¼8.8 Hz), 131.86, 130.35 (d,
(2H, m, 2,6-H), 6.63 (1H, d, J¼7.2 Hz, 4-H), 2.73 (6H, s, CNMe2), 2.46
J¼6.3 Hz), 129.63 (d, J¼23.9 Hz), 129.13 (d, J¼7.5 Hz), 191.51, 41.57
(12H, d, J¼8.7 Hz, PNMe2), 2.20 (3H, s, 3-Me); 13C NMR (125 MHz,
(d, J¼12.6 Hz), 40.13 (br s), 37.17 (br s), 20.77; 31P NMR (81 MHz,
C6D6)
d
162.1 (d, J¼28.9 Hz), 151.87 (d, J¼6.3 Hz),137.07, 127.91,
C6D6) d 60.8. [Found: C, 61.52; H, 7.56; N, 17.93; P, 13.10. C12H18N3P
121.24 (d, J¼1.2 Hz),120.59,117.69 (d, J¼1.2 Hz), 41.51 (d, J¼16.3 Hz),
requires C, 61.26; H, 7.71; N, 17.86; P, 13.17].
39.6 (d, J¼7.5 Hz), 21.37; 31P NMR (81 MHz, C6D6)
d 96.4. [Found: C,
59.75; H, 9.16; N, 19.75; P, 10.86. C14H25N4P requires C, 59.98; H,
8.99; N, 19.98; P, 11.05].
4.2.3. N,N,N0,N0-Tetramethyl-3H-naphtho[2,1-d][1,3]-azaphospho-
nole-2,3-diamine 5m. Yield 89%, yellow crystals mp 81e82 ꢀC
(pentane), bp 150e160 ꢀC/0.02 Torr; 1H NMR (500 MHz, C6D6)
4.1.13. Reduction of 1,1-bis(dimethylamino)-N0-[3-(dimethylamino)
phenyl]-N,N-dimethylphosphine carboximidamide selenide 3k. To
a solution of compound 3k (2.41 g, 6.2 mmol) in benzene (2 mL),
a solution of trismorpholidophosphite (1.80 g, 6.2 mmol) in ben-
zene (10 mL) was added. The reaction mixture was stirred for
30 min at 20 ꢀC. 31P NMR monitoring of the reaction mixture
showed the gradual disappearance of the resulting 4k (dr¼95.9)
and formation of the corresponding benzazaphosphole 5k
d
9.09 (1H, d, J¼8.5 Hz, 9-H), 7.71 (1H, d, J¼8.0 Hz, 6-H), 7.63e7.59
(1H, m, 4-H), 7.44e7.38 (2H, m, 7,8-H), 7.33 (1H, t, J¼7.5 Hz, 5-H),
3.01 (3H, br s, 2-NMe2), 2.69 (3H, br s, 2-NMe2), 2.31 (6H, d,
J¼9.5 Hz, 3-NMe2); 13C NMR (125 MHz, C6D6)
d 177.18 (d,
J¼21.4 Hz), 155.78 (d, J¼10.1 Hz), 136.24, 128.11, 127.72, 126.54,
125.96 (d, J¼1.3 Hz), 125.37 (d, J¼23.9 Hz), 124.95, 121.71 (d,
J¼10.1 Hz), 120.86 (d, J¼7.5 Hz), 41.65 (d, J¼12.6 Hz), 40.37 (br s),
37.21 (br s); 31P NMR (81 MHz, C6D6)
d 64.5. [Found: C, 66.33; H,
(
dr¼59.5 ppm). The benzene was evaporated in vacuo, ether
6.72; N, 15.73; P, 11.40. C15H18N3P requires C, 66.41; H, 6.69; N,
15.49; P, 11.42].
(20 mL) was added, the solution was filtered and the solvents were
evaporated. The residue was crystallized from pentane yielding
(1.2 g, 73%) benzazaphosphole 5k. N,N,N0,N0,N00,N00-hexamethyl-3H-
1,3-benzazaphosphonole-2,3,6-triamine 5k, bright orange crystals
4.2.4. 3-[2-(Dimethylamino)-1-methyl-1H-imidazol-5-yl]-N,N-di-
methyl-3H-1,3-benzazaphosphonol-2-amine 5n. Yellow oil yield
mp 104e105 ꢀC (pentane); 1H NMR (500 MHz, C6D6)
d
7.48e7.46
61%, 1H NMR (300 MHz, C6D6)
d
7.68 (1H, d, J¼8.1 Hz, 7-H), 7.60 (1H,
(1H, m, 4eH), 6.99 (1H, s, 7-H), 6.30e6.28 (1H, m, 5-H), 2.81 (3H, br
d, J¼2.1 Hz, 4-H-imidazol), 7.33 (1H, m, 4-H), 7.24 (1H, d, J¼7.8 Hz,
6-H), 6.83 (1H, m, 5-H), 2.87 (3H, br s, 2-NMe2) 2.67 (3H, s, 1-
Meeimidazol), 2.45 (3H, br s, 2-NMe2), 2.36 (6H, s, 2-
s, 2-NMe2), 3.01 (3H, br s, 2-NMe2), 2.56 (6H, s, 6-NMe2), 2.41 (6H,
d, J¼9.5 Hz, 3-NMe2); 13C NMR (125 MHz, C6D6)
d 177.09 (d,
J¼22.6 Hz), 161.77 (d, J¼7.5 Hz), 153.63, 129.98 (d, J¼25.1 Hz), 115.16
NMe2eimidazol); 13C NMR (125 MHz, C6D6)
d 175.92 (d,
(d, J¼11.3 Hz), 106.23 (d, J¼7.5 Hz), 104.31, 41.22 (d, J¼12.5 Hz),
J¼12.6 Hz), 160.14 (d, J¼8.8 Hz), 158.92 (d, J¼2.5 Hz), 141.78 (d,
J¼46.5 Hz), 130.13, 129.15 (d, J¼11.3 Hz), 128.24 (d, J¼23.9 Hz),
121.60 (d, J¼7.5 Hz), 119.81, 114.09 (d, J¼36.5 Hz), 41.96, 36.94 (d,
40.40(br s), 39.95, 37.19 (br s); 31P NMR (81 MHz, C6D6)
d 59.7.
[Found: C, 58.99; H, 8.33; N, 21.33; P, 11.80. C13H21N4P requires C,
59.07; H, 8.01; N, 21.20; P, 11.72].
J¼3.8 Hz), 29.40; 31P NMR (81 MHz, C6D6)
ꢁ43.9. [Found: C, 60.03;
d
H, 6.85; N, 23.22; P, 10.10. C15H20N5P requires C, 59.79; H, 6.69; N,
23.24; P, 10.28].
4.2. General procedure of thermal cyclization of
phosphorylated (PIII) formamidines 4aed,fej,m,n
4.2.5. 5-Methoxy-N,N,N0,N0-tetramethyl-3H-1,3-benzazaphosphole-
A sample of amidine 4 (1e3 g) was heated under reduced
pressure (temperature, pressure, time and yield are given in Table
2,3-diamine 3-selenide 6c. Yield 73%, bright yellow crystals mp
132e135 ꢀC (pentane); 1H NMR (300 MHz, CDCl3)
d 7.05 (1H, dd,

A. Marchenko et al. / Tetrahedron 67 (2011) 7748e7758
7755
J¼8.4, 4.8 Hz, 7-H), 6.91 (2H, m, 4,6-H), 3.79 (3H, s, 5-OMe), 3.25
(6H, br s, 2-NMe2), 2.77 (6H, d, J¼12.3 Hz, 3-NMe2); 13C NMR
2-NMe2), 2.76 (6H, d, J¼12.3 Hz, 3-NMe2); 13C NMR (125 MHz,
CDCl3)
d
165.05 (d, J¼70.4 Hz), 155.87 (d, J¼30.2 Hz) 128.82 (d,
(125 MHz, CDCl3)
d
16339 (d, J¼73.0 Hz), 156.35 (d, J¼16.3 Hz),
J¼3.8 Hz), 128.53 (d, J¼15.1 Hz), 126.17 (d, J¼12.6 Hz), 123.48 (d,
J¼5.0 Hz), 120.30 (d, J¼118.2 Hz), 38.93 (d, J¼3.8 Hz), 36.59 (d,
147.63 (d, J¼28.9 Hz), 122.05 (d, J¼115.7 Hz), 121.04 (d, J¼7.5 Hz),
120.49 (d, J¼2.5 Hz), 112.00 (d, J¼15.1 Hz), 55.85, 38.85, 36.63 (d,
J¼5.0 Hz); 31P NMR (81 MHz, CDCl3)
d
54.2. MS (APCI): m/z¼381
J¼3.80 Hz); 31P NMR (81 MHz, CDCl3)
d
57.1. MS (APCI): m/z¼332
[Mþ2]. [Found: C, 34.66; H, 4.05; N, 11.03; P, 8.08. C11H15BrN3PSe
[Mþ2]. [Found: C, 43.51; H, 5.43; N, 12.55; P, 9.27. C12H18N3OPSe
requires C, 34.85; H, 3.99; N, 11.08; P, 8.17].
requires C, 43.65; H, 5.49; N, 12.72; P, 9.38].
4.2.11. 6-Methoxy-N,N,N0,N0-tetramethyl-3H-1,3-benzazaphosphonole-
2,3-diamine 3-selenide 6j. Rf (CH2Cl2 : EtOAc¼4:1) 0.1. Yield 40%,
bright yellow crystals mp 123e124 ꢀC (hexane); 1H NMR
4.2.6. N,N,N0,N0,N0,N00-Hexamethyl-3H-1,3-benzazaphosphole-2,3,5-
triamine 3-selenide 6d. Yield 70%, bright orange crystals mp
86e87 ꢀC (hexane); 1H NMR (300 MHz, CDCl3)
d
7.02 (1H, dd, J¼8.4,
(300 MHz, DMSO-d6)
d
7.21 (1H, dd, J¼9.3, 7.8 Hz, 4-H), 6.58 (2H,
5.1 Hz, 7-H), 6.78 (2H, m 4,6-H), 3.24 (6H, br s, 2-NMe2), 2.92 (6H, s,
m, 5,7-H), 3.78 (3H, s, 6-OMe), 3.30 (3H, br s, 2-NMe2), 3.14 (3H,
5-NMe2), 2.72 (6H, d, J¼12.0 Hz, 3-NMe2); 13C NMR (125 MHz,
br s, 2-NMe2), 2.67 (6H, d, J¼12.9 Hz, 3-NMe2); 13C NMR
CDCl3)
d
163.25 (d, J¼81.7 Hz), 148.06 (d, J¼13.8 Hz), 144.90 (d,
(125 MHz, DMSO-d6)
d
165.14 (d, J¼66.7 Hz), 164.61 (d, J¼2.5 Hz),
J¼30.2 Hz), 121.49 (d, J¼124.5 Hz), 120.86 (d, J¼7.5 Hz), 118.84 (d,
156.64 (d, J¼31.4 Hz), 128.71 (d, J¼15.1 Hz), 112.01 (d, J¼124.5 Hz),
J¼2.5 Hz), 111.50 (d, J¼15.1 Hz), 41.35, 38.67 (d, J¼3.8 Hz), 35.00 (d,
109.01 (d, J¼12.6 Hz), 104.97 (d, J¼6.3 Hz), 55.29, 39.5, 35.92 (d,
J¼5.0 Hz); 31P NMR (81 MHz, CDCl3)
d
57.6. [Found: C, 45.43; H,
J¼3.8 Hz); 31P NMR (81 MHz, DMSO-d6)
d 54.4. MS (APCI): m/
5.96; N, 16.57; P, 9.12. C13H21N4PSe requires C, 45.49; H, 6.17; N,
16.32; P, 9.02].
z¼332 [Mþ2]. [Found: C, 43.55; H, 5.65; N, 12.75; P, 9.33.
C12H18N3OPSe requires C, 43.65; H, 5.49; N, 12.72; P, 9.38].
4.2.7. N,N,N0,N0,7-Pentamethyl-3H-1,3-benzazaphosphole-2,3-
diamine 3-selenide 6f. Yield 52%, bright yellow crystals mp
93e94 ꢀC (pentane); IR (KBr) 2920, 2803, 1562, 1462, 1394, 1266,
4.2.12. N,N,N0,N0,4-Pentamethyl-3H-1,3-benzazaphosphonole-2,3-
diamine 3-selenide 60h. Rf (CH2Cl2) 0.45. Yield 38%, bright yellow
crystals mp 90e91 ꢀC(hexane); 1H NMR (300 MHz, CDCl3)
d 7.23
1173, 1138, 1065, 968, 835, 748, 703, 668, 559 cmꢁ1
;
1H NMR
(1H, dd, J¼7.8, 1.3 Hz, 6-H-Ar), 6.93 (1H, dd, J¼8.1, 4.2 Hz, 7-H), 6.75
(1H, dd, J¼7.5, 4.2 Hz, 5-H), 3.38 (3H, br s, 2-NMe2), 3.22 (3H, br s.,
2-NMe2), 2.81 (6H, d, J¼12.3 Hz, 3-NMe2), 2.43 (3H, s, 4-Me); 13C
(300 MHz, CDCl3)
d
7.18 (2H, m, 4,6-H), 6.91 (1H, dt, J¼7.5, 3.9 Hz, 6-
H), 3.37 (3H, br s., 2-NMe2), 3.25 (3H, br s, 2-NMe2), 2.76 (6H, d,
J¼12.3 Hz, 3-NMe2), 2.34 (3H, s, 7-Me); 13C NMR (125 MHz, CDCl3)
NMR (125 MHz, CDCl3)
d
164.13 (d, J¼71.7 Hz), 154.52 (d,
d
163.28 (d, J¼70.4 Hz), 152.34 (d, J¼28.9 Hz), 135.47 (d, J¼1.2 Hz),
J¼30.2 Hz), 1140.26 (d, J¼12.6 Hz), 134.20, 124.88 (d, J¼10.1 Hz),
129.23 (d, J¼6.3 Hz), 124.86 (d, J¼10.1 Hz), 123.04 (d, J¼12.6 Hz),
121.0 (d, J¼117.0 Hz), 38.69 (br s), 36.68 (d, J¼5.0 Hz), 16.60 (d,
118.93 (d, J¼144.4 Hz), 117.83 (d, J¼5.0 Hz), 38.77, 36.50 (d,
J¼5.0 Hz), 18.60 (d, J¼5.0 Hz); 31P NMR (81 MHz, CDCl3)
d 53.9. MS
J¼2.5 Hz); 31P NMR (81 MHz, CDCl3)
d
56.9. MS (APCI): m/z¼316
(APCI): m/z¼316 [Mþ2]. [Found: C, 45.93; H, 5.89; N, 13.22; P, 9.78.
[Mþ2]. [Found: C, 45.63; H, 5.69; N, 13.56; P, 9.63. C12H18N3PSe
C12H18N3PSe requires C, 45.87; H, 5.77; N, 13.37; P, 9.86].
requires C, 45.87; H, 5.77; N, 13.37; P, 9.86].
4.2.13. 4-Bromo-N,N,N0,N0-tetramethyl-3H-1,3-benzazaphosphonole-
2,3-diamine 3-selenide 60i. Rf (CH2Cl2)¼0.15. Yield 32%, bright yel-
low crystals mp 131e132 ꢀC (hexane); 1H NMR (300 MHz, CDCl3)
4.2.8. 7-Chloro-N,N,N0,N0-tetramethyl-3H-1,3-benzazaphosphole-
2,3-diamine 3-selenide 6g. Yield 27%, bright yellow crystals mp
114e115 ꢀC (hexane); 1H NMR (300 MHz, CDCl3)
d
7.38 (1H, d,
d 7.17 (1H, t, 6-H), 7.08e7.01 (2H, m, 5,7-H), 3.41 (3H, br s, 2-NMe2),
J¼7.8 Hz, 6-H), 7.25 (1H, m, 4-H), 6.93 (1H, dt, J¼7.5, 5.1 Hz, 5-H),
3.24 (3H, br s, 2-NMe2), 2.84 (6H, d, J¼12.3 Hz, 3-NMe2); 13C NMR
3.39 (3H, br s, 2-NMe2), 3.31 (3H, br s, 2-NMe2), 2.77 (6H, d,
(125 MHz, CDCl3)
d
164.43 (d, J¼81.7 Hz), 156.20 (d, J¼30.2 Hz),
J¼12.3 Hz, 3-NMe2); 13C NMR (125 MHz, CDCl3)
d
164.50 (d,
135.08, 126.51 (d, J¼7.5 Hz), 122.76 (d, J¼10.1 Hz), 121.34 (d,
J¼70.4 Hz), 150.63 (d, J¼28.9 Hz), 134.50, 125.81 (d, J¼13.8 Hz),
124.92 (d, J¼7.5 Hz), 123.83 (d, J¼13.8 Hz), 123.54 (d, J¼113.2 Hz),
J¼117.0 Hz), 119.11 (d, J¼5.0 Hz), 39.14 (br s), 38.50 (br s), 36.50 (d,
J¼5.0 Hz,); 31P NMR (81 MHz, CDCl3)
d
56.5. MS (APCI): m/z¼380
38.93, 36.63 (d, J¼3.8 Hz); 31P NMR (81 MHz, CDCl3)
d
57.4. MS
[Mþ1]. [Found: C, 34.63; H, 4.12; N, 11.05; P, 8.10. C11H15BrN3PSe
(APCI): m/z¼336 [Mþ2]. [Found: C, 39.43; H, 4.59; N, 12.56; P, 9.22.
requires C, 34.85; H, 3.99; N, 11.08; P, 8.17].
C11H15ClN3PSe requires C, 39.48; H, 4.52; N, 12.56; P, 9.26].
4.2.14. 4-Methoxy-N,N,N0,N0-tetramethyl-3H-1,-benzazaphospho-
nole-2,3-diamine 3-selenide 60j. Rf (CH2Cl2/EtOAc¼4 :1) 0.3. Yield
12%, bright yellow crystals mp 132e135 ꢀC (hexane); 1H NMR
4.2.9. N,N,N0,N0,6-Pentamethyl-3H-1,3-benzazaphosphonole-2,3-
diamine 3-selenide 6h. Rf (CH2Cl2) 0.2. Yield 35%, bright yellow
crystals mp 84e85 ꢀC(hexane); 1H NMR (300 MHz, CDCl3)
d
7.24
(300 MHz, CDCl3)
d
7.29 (1H, t, J¼8.1 Hz, 6-H), 6.73 (1H, dd, J¼7.8,
(1H, dd, J¼7.2, 9.9 Hz, 4-H), 6.94 (1H, d, J¼3.9 Hz, 7-H), 6.84 (1H, dd,
J¼7.5, 3.6 Hz, 5-H), 3.38 (3H, br s, 2-NMe2), 3.32 (3H, br s, 2-NMe2),
2.75 (6H, d, J¼12.3 Hz, 3-NMe2), 2.34 (3H, s, 6-Me); 13C NMR
3.9 Hz, 7-H), 6.49 (1H, dd, J¼8.1, 6.0 Hz, 5-H), 3.87 (3H, s, 4-OMe),
3.41 (3H, br s, 2-NMe2), 3.23 (3H, br s, 2-NMe2), 2.77 (6H, d,
J¼12.9 Hz, 3-NMe2); 13C NMR (125 MHz, CDCl3)
d 164.94 (d,
(125 MHz, CDCl3)
d
164.73 (d, J¼70.4 Hz), 154.66 (d, J¼30.2 Hz),
J¼76.7 Hz),160.40 (d, J¼7.5 Hz), 155.77 (d, J¼27.7 Hz),135.88, 113.29
(d, J¼3.8 Hz), 106.91 (d, J¼113.2 Hz), 105.78 (d, J¼6.3 Hz), 55.91,
39.09 (br s), 38.63(br s), 36.80 (d, J¼5.0 Hz); 31P NMR (81 MHz,
145.31 (d, J¼2.5 Hz), 127.43 (d, J¼13.8 Hz), 124.28 (d, J¼12.5 Hz),
121.00 (d, J¼6.3 Hz), 118.12 (d, J¼118.12 Hz), 38.92, 36.66 (d,
J¼3.8 Hz), 21.98; 31P NMR (81 MHz, CDCl3)
d
54.5. MS (APCI): m/
CDCl3) d 54.4. Found: C, 43.43; H, 5.59; N, 12.56; P, 9.22.
z¼316 [Mþ2]. [Found: C, 46.06; H, 6.01; N, 13.03; P, 9.95.
C12H18N3OPSe requires C, 43.65; H, 5.49; N, 12.72; P, 9.38.
C12H18N3PSe requires C, 45.87; H, 5.77; N, 13.37; P, 9.86].
4.2.15. N3,N3-Diethyl-5-methoxy-N2,N2-dimethyl-3H-1,3-
benzazaphosphole-2,3-diamine 3-sulfide 7. To a mixture of N0-(4-
4.2.10. 6-Bromo-N,N,N0,N0-tetramethyl-3H-1,3-btnzazaphosphonole-
2,3-diamine 3-selenide 6i. Rf (CH2Cl2)¼0.4. Yield 9%, bright yellow
crystals mp 112e113 ꢀC (hexane); 1H NMR (300 MHz, CDCl3)
methoxyphenyl)-N,N-dimethylmethanimidoformamide
56 mmol) and NEt3 (5.7 g, 57 mmol) in pyridine (40 mL) cooled to
ꢀC a solution of PBr3 (15.20 g, 56 mmol) in methylene chloride
(10
g,
d
7.29e7.11 (3H, m, 4,5,7-H), 3.39 (3H, br s, 2-NMe2), 3.23 (3H, br s,
0

7756
A. Marchenko et al. / Tetrahedron 67 (2011) 7748e7758
(40 mL) was added dropwise with stirring. The reaction mixture was
stirred for 15 h at room temperature and then cooled to ꢁ30 ꢀC.
HNEt2 (25.0 g, 0.34 mol) was added and the mixture was kept stir-
ring for 1h. The solvents and volatile products were distilled off and
the residue was kept at 100 ꢀC in vacuo (10 Torr) for 1 h. To the
residue benzene (50 mL) and sulfur (1.79 g, 56 mmol) were added
and the reaction mixture was refluxed for 3 h. The reaction mixture
was filtered and evaporated, leaving an oily residue that was tritu-
rated with methanol (5 mL). The crude solid product was recrys-
tallized from heptane giving 5.06 g of 7. (29%); bright orange crystals
39.25; H, 4.23; N, 11.55; P, 8.37. C12H15F3N3PSe requires C, 39.14; H,
4.11; N, 11.41; P, 8.41.
4.3. General method of reducing N,N,N0,N0-tetramethyl-3H-
1,3-benzazaphosphole-2,3-diamine 3-selenides 6h, e, l and 60l
with metallic sodium
A mixture of the corresponding selenide 6 (0.6 mmol) and so-
dium (1.2 mmol) dispersed in toluene (3 mL) was refluxed for 2 h.
The solution was filtered, the toluene was evaporated and the
residue was distilled.
mp 85e86 ꢀC (heptane); 1H NMR (200 MHz, CDCl3)
d 7.07e7.02 (1H,
m, 7-H), 6.94e6.86 (2H, m, 4-Hþ6-H), 3.79 (3H, s, 5-OMe), 3.35e2.91
(10H, m, 2-NMe2þ3-CH2), 1.07 (6H, t, J¼7.0 Hz, 3-CH3); 31P NMR
4.3.1. N,N,N0,N0,6-Pentamethyl-3H-1,3-benzazaphosphonole-2,3-
diamine 5h. Yield 90%, yellow oil, bp 110 ꢀC/0.05 Torr; 1H NMR
(81 MHz, CDCl3)
d 62.8. Found: C, 53.95; H, 7.18; N, 13.33; P, 10.06.
C14H22N3OPS requires C, 54.00; H, 7.12; N, 13.49; P, 9.95.
(500 MHz, C6D6)
d
7.46 (1H, s, 7-H), 7.43 (1H, dd, J¼7.5, 4.0 Hz, 4-H),
6.73 (1H, m, 5-H), 2.95 (3H, br s, 2-NMe2), 2.71 (3H, br s, 2-NMe2),
4.2.16. N,N,N0,N0-Tetramethyl-5-(trifluoromethyl)-3H-1,3-
benzazaphosphole-2,3-diamine 3-selenide 6e. A mixture of 4e (1.67 g,
5 mmol) and Et3NHþTfOꢁ (0.025 g, 0.1 mmol) was heated at 170 ꢀC
(12 Torr) over 15 min while distilling off hexamethylphosphorus
triamide and N,N-dimethyl-N0-[4-(trifluoromethyl)phenyl]meth-
animidamide. The residue was dissolved in benzene (5 mL) and Se
(0.4 g, 5 mmol) was added. The reaction mixture was stirred for 1 h
at 65 ꢀC. The reaction mixture was placed on SiO2 and chromato-
graphed (eluent CH2Cl2). Rf 0.35e0.45; 0.74 g (40%); yellow crystals
2.34 (6H, d, J¼9.0 Hz, 3-NMe2), 2.16 (3H, s, 6-Me); 13C NMR
(125 MHz, C6D6)
d
176.24 (d, J¼21.4 Hz), 159.69 (d, J¼8.8 Hz), 141.03,
128.83 (d, J¼25.1 Hz), 125.57 (d, J¼7.5 Hz), 122.35 (d, J¼6.3 Hz),
120.49, 41.30 (d, J¼12.6 Hz), 41.35 (br s), 38.23 (br s), 21.46; 31P NMR
(81 MHz, C6D6)
d 60.4. Found: C, 61.42; H, 7.45; N, 18.17; P, 13.05.
C12H18N3P requires C, 61.26; H, 7.71; N, 17.86; P, 13.17.
4.3.2. N,N,N0,N0-Tetramethyl-5-(trifluoromethyl)-3H-1,3-
benzazaphosphole-2,3-diamine 5e. Yield 90%, yellowish liquid; bp
mp 70e71 ꢀC(pentane); 1H NMR (300 MHz, CDCl3)
d 7.59e7.55 (2H,
120 ꢀC/0.05 Torr; 1H NMR (500 MHz, C6D6)
d 7.78 (1H, m, 4-H), 7.39
m, 4-Hþ6-H), 7.15 (1H, dd, J¼8.1, 4.2 Hz, 7-H), 3.41 (3H, br s, 2-NMe2),
(1H, d, J¼8.5 Hz, 6-H), 7.35 (1H, d, J¼8.0 Hz, 7-H), 2.87 (3H, br s, 2-
3.27 (3H, br s, 2-NMe2), 2.77 (6H, d, J¼12.6 Hz, 3-NMe2); 13C NMR
NMe2), 2.60 (3H, br s, 2-NMe2), 2.18 (6H, d, J¼9.0 Hz, 3-NMe2); 13
C
(125 MHz, CDCl3)
d
165.73 (d, J¼70.4 Hz), 157.50 (d, J¼30.2 Hz),
NMR (125 MHz, C6D6)
d
177.70 (d, J¼22.6 Hz), 161.99 (d, J¼8.8 Hz),
131.46 (q, J¼2.5 Hz), 125.25 (m),124.78 (qd, J¼15.1, 3.8 Hz),124.05 (q,
J¼245.2 Hz), 122.23 (d, J¼116.9 Hz), 120.17 (d, J¼6.3 Hz), 39.00 (br s),
129.41 (d, J¼5.0 Hz),128.35 (d, J¼3.8 Hz),125.86 (dq, J¼25.1, 3.8 Hz),
125.52 (q, J¼271.6 Hz), 122.80 (dd, J¼25.1, 6.3 Hz), 119.14, 41.26 (d,
36.54 (d, J¼5.0 Hz); 31P NMR (81 MHz, CDCl3)
d
54.4; 19F NMR
ꢁ62.1. MS (APCI): m/z¼370 [Mþ2]. Found: C,
J¼12.6 Hz), 39.94 (d, J¼13.8 Hz); 31P NMR (81 MHz, C6D6)
d F
58.9; 19
(188 MHz, CDCl3)
d
NMR (188 MHz, C6D6)
d
ꢁ61.1. Found: C, 49.52; H, 5.56; N, 14.33; P,
39.22; H, 4.09; N, 11.22; P, 8.31. C12H15F3N3PSe requires C, 39.14; H,
4.11; N, 11.41; P, 8.41.
10.62. C12H15F3N3P requires C, 49.83; H, 5.23; N, 14.53; P, 10.71.
4.3.3. N,N,N0,N0-Tetramethyl-6-(trifluoromethyl)-3H-1,3-benzazaphos-
4.2.17. N,N,N0,N0-Tetramethyl-6-(trifluoromethyl)-3H-1,3-
benzazaphosphole-2,3-diamine 3-selenide 6l and N,N,N0,N0-tetra-
methyl-4-(trifluoromethyl)-3H-1,3-behzazaphosphole-2,3-diamine 3-
selenide 60l. This was prepared analogously to 6e. Isomers 6l and 60l
were separated chromatographically on plates (eluent CH2Cl2).
N,N,N0,N0-Tetramethyl-6-(trifluoromethyl)-3H-1,3-benzazaphosphole-
2,3-diamine 3-selenide 6l. Rf 0.48e0.53; 0.25 g (15%); yellow crystals
mp 115e116 ꢀC (pentane); IR (KBr) 2927, 1614, 1574, 1476, 1419, 1381,
1326, 1273, 1253, 1163, 1123, 1050, 974, 889, 820, 722, 698, 675,
phole-2,3-diamine 5l. Yield 89%, yellowish crystals, mp 52e53 ꢀC, bp
1
102 ꢀC/0.05 Torr; H NMR (300 MHz, C6D6)
d 7.79 (1H, s, 7-H), 7.29
(1H, dd, J¼7.5, 3.6 Hz, 4-H), 7.03 (1H, dm, J¼7.5 Hz, 5-H), 2.87 (3H, br
s, 2-NMe2), 2.61 (3H, br s, 2-NMe2), 2.21 (6H, d, J¼9.3 Hz, 3-NMe2);
13C NMR (125 MHz, C6D6)
d
176.68 (d, J¼22.6 Hz), 159.41 (d,
J¼10.1 Hz), 133.18 (d, J¼5.0 Hz), 132.79 (q, J¼35.7 Hz), 129.07 (d,
J¼23.9 Hz), 124.96 (q, J¼272.9 Hz), 117.32 (m), 115.71(q, J¼3.8 Hz),
41.39 (d, J¼13.8 Hz), 39.90 (br s), 37.11 (br s); 31P NMR (81 MHz, C6D6)
d
59.7; 19F NMR (188 MHz, C6D6)
d
ꢁ62.6. Found: C, 49.65; H, 5.27; N,
623 cmꢁ1; 1H NMR (500 MHz, CDCl3)
d
7.42 (1H, t, J¼8.5 Hz, 4-H), 7.32
14.76; P, 10.47. C12H15F3N3P requires C, 49.83; H, 5.23; N, 14.53; P,
10.71.
(1H, d, J¼2.5 Hz, 7-H), 7.22 (1H, m, 5-H), 3.37 (3H, br s, 2-NMe2), 3.23
(3H, br s, 2-NMe2), 2.76 (6H, d, J¼12.5 Hz, 3-NMe2); 13C NMR
4.3.4. N,N,N0,N0-Tetramethyl-4-(trifluoromethyl)-3H-1,3-benzazaphos-
phole-2,3-diamine 50l. Yield 90%, yellowish crystals, mp 39e40 ꢀC;
(125MHz, CDCl3)
d
164.89(d, J¼70.4 Hz),154.93 (d, J¼30.2Hz),135.78
(qd, J¼32.7, 2.5 Hz), 125.51 (d, J¼115.7 Hz), 123.68 (q, J¼272.9 Hz),
119.69 (dq, J¼12.69, 2.5 Hz), 116.89 (m), 38.88 (d, J¼3.8 Hz), 36.19 (d,
bp 100 ꢀC/0.05 Torr; 1H NMR (500 MHz, C6D6)
d
7.49 (1H, d, J¼7.5 Hz,
J¼5.0 Hz); 31P NMR (81 MHz, CDCl3)
d
55.0; 19F NMR (188MHz, CDCl3)
7-H), 7.68 (1H, m, 5-H), 7.01 (1H, t, 6-H), 2.90 (3H, br s, 2-NMe2), 2.67
(3H, br s, 2-NMe2), 2.39 (6H, d, J¼11.7 Hz, 3-NMe2); 13C NMR
d
ꢁ63.7. MS(APCI):m/z¼370 [Mþ2]. Found:C,39.22;H, 4.04;N,11.36;
P, 8.52. C12H15F3N3PSe requires C, 39.14; H, 4.11; N, 11.41; P, 8.41.
N,N,N0,N0-Tetramethyl-4-(trifluoromethyl)-3H-1,3-behzazaphosphole-
2,3-diamine 3-selenide 60l. Rf 0.35e0.48; 0.70 g (41%); mp 126e127 ꢀC
(pentane); IR (KBr) 1565, 1399, 1320, 1173, 1117, 973, 892, 799,
(125 MHz, C6D6)
d
176.16 (d, J¼12.6 Hz), 160.01 (d, J¼8.8 Hz), 131.06
(qd, J¼31.4, 16.3 Hz), 131.01, 126.05 (d, J¼8.8 Hz), 124.97 (q,
J¼272.8 Hz), 122.78, 117.66 (m), 41.33 (br s), 39.60 (br s), 37.42 (d,
J¼3.8 Hz); 31P NMR (81 MHz, C6D6)
d
60.2; 19F NMR (188 MHz, C6D6)
698 cmꢁ1; 1H NMR (500 MHz, CDCl3)
d
7.41 (1H, t, J¼8.0 Hz, 6-H), 7.26
d
ꢁ62.33 (d, J¼24.4 Hz). Found: C, 49.99; H, 5.33; N, 14.37; P, 10.80.
(1H, dd, J¼8.0, 3.0 Hz, 7-H), 7.18 (1H, m, 5-H), 3.36 (3H, br s, 2-NMe2),
C12H15F3N3P requires C, 49.83; H, 5.23; N, 14.53; P, 10.71.
3.23 (3H, br s, 2-NMe2), 2.75 (6H, d, J¼12.0 Hz, 3-NMe2); 13C NMR
4.3.5. N,N,N0,N0,4-Pentamethyl-3H-1,3-benzazaphosphole-2,3-diamine
50h. A solution of compound 60h (0.17 g, 0.54 mmol) and (0.1 g,
0.6 mmol) of hexamethylphosphorus triamide in benzene (1 mL) was
stirred at 20 ꢀC for 10 min. The solvent was evaporated, the residue
was kept at 120 ꢀC for 10 min in vacuo (0.05 Torr) and then
(125MHz, CDCl3)
d
164.32(d, J¼85.5Hz),155.63 (d, J¼27.7Hz),134.14,
130.13 (qd, J¼32.7, 10.0 Hz), 124.14 (d, J¼5.0 Hz), 123.61 (q,
J¼275.4 Hz),120.30 (m),118.49 (d, J¼105.6 Hz), 39.22 (br s), 38.25 (br
s), 36.02 (d, J¼6.3 Hz); 31P NMR (81 MHz, CDCl3)
d
54.2; 19F NMR
(188 MHz, CDCl3)
d
ꢁ60.1. MS (APCI): m/z¼370 [Mþ2]. Found: C,

A. Marchenko et al. / Tetrahedron 67 (2011) 7748e7758
7757
recrystallized from hexane to give the product (0.07 g, 58%), yellow
crystals mp 32e34 ꢀC. 1H NMR (300 MHz, C6D6)
7.49 (1H, d,
J¼8.0 Hz, 7-H), 7.44e7.42 (1H, m, 4-H), 7.23 (1H, t, J¼8.0 Hz, 6-H),
6.88 (1H, m, 5-H), 2.80 (6H, br s, 2-NMe2), 0.95 (9H, d, J¼12.5 Hz,
d
J¼7.8 Hz, 7-H), 7.19 (1H, m, 6-H), 6.72 (1H, dd, J¼7.5, 4.8 Hz, 5-H), 2.95
CMe3); 13C NMR (125 MHz, C6D6)
d
178.08 (d, J¼24.0 Hz), 161.38, (d,
(3H, br s, 2-NMe2), 2.73 (3H, br s, 2-NMe2), 2.38 (3H, br s, 4-Me), 2.32
J¼2.5 Hz), 130.92 (d, J¼1.2 Hz), 130.06, 129.28 (d, J¼22.6 Hz), 121.19
(6H, d, J¼8.7 Hz, 3-NMe2); 13C NMR (125 MHz, C6D6)
d 175.65 (d,
(d, J¼7.5 Hz), 119.58, 34.16 (d, J¼17.6 Hz), 27.90 (d, J¼12.75 Hz),
J¼17.6 Hz), 159.06 (d, J¼10.1 Hz), 139.27 (d, J¼20.1 Hz), 131.26, 128.52
22.48; 31P NMR (81 MHz, C6D6)
d 13.2. [Found: C, 66.96; H, 8.31; N,
(d, J¼7.5 Hz), 122.38 (d, J¼3.8 Hz), 117.33, 41.44, 37.60 (d, J¼3.8 Hz),
11.65; P, 13.27. C13H19N2P requires C, 66.65; H, 8.17; N, 11.96; P,
13.22].
21.37 (d, J¼6.3 Hz); 31P NMR (81 MHz, C6D6)
d 58.1. [Found: C, 61.35;
H, 7.83; N, 17.63; P, 13.80. C12H18N3P requires C, 61.26; H, 7.71; N,
17.86; P, 13.17].
4.3.10. 3-(1-Adamantyl)-N,N-dimethyl-3H-1,3-benzazaphosphonol-
2-amine 5p. A solution of compound 8p (0.5 g, 1.4 mmol) and
triethylamine (0.14 g, 1.4 mmol) in benzene (3 mL) was heated with
stirring in a well-stoppered flask (or a sealed ampoule) at 100 ꢀC for
20 h. The precipitated solid was separated and the filtrate was
evaporated. The residue was dissolved in pentane (15 mL) at 100 ꢀC.
The solution was filtered and the solvent was evaporated to give
4.3.6. 6-Methoxy-N,N,N0,N0-tetramethyl-3H-1,3-benzazaphosphole-
2,3-diamine 5j. A solution of hexamethylphosphorus triamide
(1.04 g, 3.6 mmol) in benzene (8 mL) was added to a solution of
compound 6j (1.19 g, 3.6 mmol) in solvent (10 mL). The reaction
mixture was stirred at 50 ꢀC for 0.5 h. The solvent was evaporated in
vacuo and the residue was extracted with hot hexane (3ꢂ10 mL).
The hexane was evaporated and the residue was distilled. Yellowish
oil bp 159e160 ꢀC/0.05 Torr (0.83 g, yield 92%); 1H NMR (300 MHz,
a viscous yellow oil (0.36 g, 82%). 1H NMR (500 MHz, C6D6)
d 7.63
(1H, d, J¼8.0 Hz, 7-H), 7.43e7.46 (1H, m, 4-H), 7.23 (1H, t, J¼8.0 Hz,
6-H), 6.88e6.94 (1H, m, 4-H), 2.86 (6H, br s, 2-NMe2), 1.73 (6H, s,
PC(CH2)3), 1.64 (3H, s, CHeAd), 1.45 (6H, m, CH2eAd); 13C NMR
C6D6)
d
7.43 (1H, dd, J¼8.1, 3.6 Hz, 4-H), 7.24 (1H, dd, J¼2.4, 1.2 Hz,
7-H), 6.58 (1H, m, 5-H), 3.34 (3H, s, 6-OMe), 2.96 (3H, br s, 2-NMe2),
(125 MHz, C6D6)
d
176.76 (d, J¼25.1 Hz), 161.48, 129.93, 129.46 (d,
2.70 (3H, br s, 2-NMe2), 2.45 (6H, d, J¼9.3 Hz, 3-NMe2); 31P NMR
J¼21.4 Hz), 121.05 (d, J¼6.3 Hz),119.37, 39.54 (d, J¼8.8 Hz), 38.38 (d,
J¼18.9 Hz), 36.55, 29.08 (d, J¼7.5 Hz), 28.11 (dd, J¼127.0, J¼7.5 Hz);
(81 MHz, C6D6)
d 59.7. [Found: C, 57.79; H, 7.33; N, 16.47; P, 12.60.
C12H18N3OP requires C, 57.36; H, 7.22; N, 16.72; P, 12.33].
31P NMR (81 MHz, C6D6)
d 11.1. [Found: C, 73.00; H, 8.16; N, 9.05; P,
9.83. C19H25N2P requires C, 73.05; H, 8.07; N, 8.97; P, 9.92].
4.3.7. tert-Butyl[(Z)-(dimethylamino)(phenylimino)methyl]phosphi-
nous chloride 8o. To a solution of compound 4o (1.11 g, 4.0 mmol) in
benzene (2 mL) cooled to 0 ꢀC, a solution of phosphorus trichloride
(0.55 g, 4.0 mmol) in benzene (2 mL) was added. The reaction
mixture was stirred at 20 ꢀC for 10 min. The solvent was evaporated
in vacuo (10 Torr), and the residue was distilled. Yellowish oil bp
4.4. X-ray crystallography
Numerical details are presented in Table 4. Data collection:
Crystals were mounted in inert oil on glass fibers and transferred to
the cold gas stream of the diffractometer (Bruker SMART CCDC for
4b, Siemens P3 for 7). Measurements were performed with mon-
110e112 ꢀC/0.05 Torr, oil, yield 75%. 1H NMR (300 MHz, C6D6)
d 7.12
(2H, t, J¼7.8 Hz, 3,5-H), 6.85 (1H, t, J¼7.5 Hz, 4-H), 6.87 (2H, d,
ochromated Mo-Ka radiation. Structure refinement: The structures
J¼7.8 Hz, 2,6-H), 2.44 (6H, s, NMe2), 1.27 (9H, d, J¼13.5 Hz, CMe3);
were refined anisotropically against F2 (program SHELXL-97, G.M.
13C NMR (125 MHz, C6D6)
d
160.08 (d, J¼41.5 Hz), 150.68 (d,
€
Sheldrick, University of Gottingen). Hydrogen atoms were included
J¼9.0 Hz), 128.61, 121.63, 121.19 (d, J¼2.5 Hz), 40.75 (d, J¼7.5 Hz),
using a riding model except for methyl hydrogens, for which ide-
alized rigid groups were employed.
36.24 (d, J¼35.2 Hz), 26.54 (d, J¼16.4 Hz); 31P NMR (81 MHz, C6D6)
d
100.8. [Found: C, 57.95; H, 7.87; N, 10.63; P, 11.67. C13H20ClN2P
requires C, 57.67; H, 7.45; N, 10.35; P, 11.44].
Table 4
Details of X-ray structure analyses of 4b and 7
4.3.8. 1-Adamantyl[(Z)-(dimethylamino)(phenilimino)methyl]phos-
phinous chloride 8p. To a solution of compound 4p (0.91 g,
2.5 mmol) in benzene (2 mL) cooled to 0 ꢀC was added a solution of
phosphorus trichloride (0.34 g, 2.5 mmol) in benzene (2 mL). The
reaction mixture was stirred at 20 ꢀC for 30 min in vacuo (10 Torr).
The residue was washed with pentane (2ꢂ3 mL) and dried to give
Compound
4b
7
Formula
Mr
Habit
C14H25N4P
280.35
Yellow plate
0.4ꢂ0.15ꢂ0.04
Monoclinic
P21/c
C14H22N3OPS
311.38
Yellow prism
0.7ꢂ0.55ꢂ0.45
Monoclinic
C2/c
Crystal size/mm
Crystal system
Space group
Cell constants:
a yellowish oil (0.8 g, 90%). 1H NMR (500 MHz, C6D6)
d 7.18 (3H, m,
3,4,5-H), 6.90 (2H, d, J¼7.0 Hz, 2,6-H), 2.59 (6H, s, NMe2), 2.03 (6H,
ꢀ
a/A
9.8191 (4)
13.8618 (6)
11.5729 (6)
90
94.939(2)
90
1569.34
4
1.187
0.17
50.310 (8)
9.3053 (16)
13.748 (2)
90
91.083(10)
90
6435.0
16
1.286
s, PC(CH2)3), 1.89 (3H, s, CHeAd), 1.60 (6H, s, CH2eAd); 13C NMR
ꢀ
b/A
ꢀ
c/A
(125 MHz, C6D6)
d
159.27 (d, J¼47.8 Hz), 150.60 (d, J¼12.5 Hz),
ꢀ
ꢀ
a
/
128.47 (d, J¼35.2 Hz), 121.59 (d, J¼7.5 Hz), 121.55, 40.78 (d,
b
/
J¼6.3 Hz), 39.87 (d, J¼40.2 Hz), 38.14 (d, J¼12.6 Hz), 36.66, 28.66 (d,
ꢀ
/
g
J¼8.8 Hz); 31P NMR (81 MHz, C6D6)
d
94.23. [Found: C, 65.72; H,
3
ꢀ
V/A
7.71; N, 8.15; P, 8.91. C19H26ClN2P requires C, 65.42; H, 7.51; N, 8.03;
P, 8.88].
Z
Dx/Mg mꢁ3
m
/mmꢁ1
0.30
F(000)
608
2656
4.3.9. 3-tert-Butyl-N,N-dimethyl-3H-1,3-benzazaphosphonol-2-
amine 5o. A solution of compound 8o (0.27 g, 1.0 mmol) and NEt3
(0.2 g, 1.98 mmol) in benzene (2 mL) was heated with stirring in
a thoroughly capped flask (or sealed ampoule) at 100 ꢀC for 20 h.
The reaction mixture was cooled and the solvent was evaporated.
Pentane (10 mL) was added to the residue. The solution was fil-
tered; the solvent was evaporated to ¼ of the original volume and
was left at ꢁ20 ꢀC for 24 h. The precipitated solid was collected by
filtration to give the product (0.15 g, 68%), yellow crystals
T/ꢀC
ꢁ100
ꢁ100
2
qmax
50
50
No. of reflections:
Measured
Independent
Rint
11,200
2680
0.036
179
0.116
0.041
0.95
9640
5647
0.029
371
0.086
0.034
1.03
Parameters
wR(F2, all refl.)
R(F, >4
S
Max. Dr/e A
s
(F))
ꢀꢁ3
0.32
0.30
mp¼84e85 ꢀC (pentane). 1H NMR (500 MHz, C6D6)
d 7.65 (1H, d,

7758
A. Marchenko et al. / Tetrahedron 67 (2011) 7748e7758
3. (a) Nyulaszi, L.; Veszpremi, J. J. Mol. Struct. 1995, 347, 57; (b) Nyulaszi, L.;
Complete crystallographic data (excluding structure factors)
Veszpremi, J. Phosphorus, Sulfur Silicon 1996, 109/110, 109.
4. (a) Walborsky, H.; Ronman, P. J. Org. Chem. 1978, 43, 731; (b) Heinicke, J. J.
Organomet. Chem. 1989, 364, 17.
5. Tolmachev, A. A.; Merkulov, A. S.; Oshovskyi, G. V. Chem. Heterocycl. Compd.
(Engl. Transl.) 1997, 7, 999.
6. Marchenko, A. P.; Koidan, G. N.; Hurieva, A. N.; Merkulov, A. S.; Pinchuk, A. M.;
Kostyuk, A. N. Tetrahedron 2010, 66, 3668.
7. Dahl, O. Tetrahedron Lett. 1982, 14, 1493.
have been deposited at the Cambridge Crystallographic Data Centre
under the numbers CCDC 807930 (4b), 709630 (7). These data can
be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/
retrieving.html, or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK (fax: 44 1223 336
033; or e-mail: deposit@ccdc.cam.ac.uk).
8. Marchenko, A. P.; Koidan, H. N.; Huryeva, A. N.; Zarudnitskii, E. V.; Yurchenko,
A. A.; Kostyuk, A. N. J. Org. Chem. 2010, 75, 7141.
Acknowledgements
€
€
€
9. (a) Ahlrichs, R.; Bar, M.; Haser, M.; Horn, H.; Kolmel, C. Chem. Phys. Lett. 1989,
162, 165; (b) Ahlrichs, R.; Arnim, M. V. In Methods and Techniques in Compu-
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1995; p 509ff.
10. Becke, A. D. Phys. Rev. A 1988, 38, 3098.
11. Perdew, J. P. Phys. Rev. B 1986, 33, 8822.
We thank Professor Dr. U. Manthe, University of Bielefeld (Ger-
many) for the access to the computer cluster, TURBOMOLE v. 6.02
and GAUSSIAN-03 sets of program.
12. Schaefer, A.; Huber, C.; Ahlrichs, R. J. Chem. Phys. 1994, 100, 5829.
13. Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.;
Cheeseman, J. R.; Montgomery, J. A., Jr.; Vreven, T.; Kudin, K. N.; Burant, J. C.;
Millam, J. M.; Iyengar, S. S.; Tomasi, J.; Barone, V.; Mennucci, B.; Cossi, M.;
Scalmani, G.; Rega, N.; Petersson, G. A.; Nakatsuji, H.; Hada, M.; Ehara, M.;
Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao,
O.; Nakai, H.; Klene, M.; Li, X.; Knox, J. E.; Hratchian, H. P.; Cross, J. B.; Bakken,
V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A.
J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Ayala, P. Y.; Morokuma, K.; Voth, G.
A.; Salvador, P.; Dannenberg, J. J.; Zakrzewski, V. G.; Dapprich, S.; Daniels, A. D.;
Strain, M. C.; Farkas, O.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.; Fores-
man, J. B.; Ortiz, J. V.; Cui, Q.; Baboul, A. G.; Clifford, S.; Cioslowski, J.; Stefanov,
B. B.; Liu, G.; Liashenko, A.; Piskorz, P.; Komaromi, I.; Martin, R. L.; Fox, D. J.;
Keith, T.; Al-Laham, M. A.; Peng, C. Y.; Nanayakkara, A.; Challacombe, M.; Gill, P.
M. W.; Johnson, B.; Chen, W.; Wong, M. W.; Gonzalez, C.; Pople, J. A. Gaussian
03, Revision C.02; Gaussian: Wallingford CT, 2004.
Supplementary data
Supplementary data includes Tables S1 and S2 with the calcu-
lated total and relative energy values, a short discussion of the two-
step mechanism of cyclization of 4, Fig. S2 with the VMD repre-
sentation of the optimized structures 8 and 20 and a complete set of
Cartesian coordinates for all optimized structures. Supplementary
data associated with this article can be found, in the online version,
at doi:10.1016/j.tet.2011.08.007.
References and notes
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