Phosphorus heterocycles from 2-(2-aminophenyl)-1H-benzimidazole

Article abstract of DOI:10.1002/hc.20022

We report the syntheses of unsaturated six-membered heterocycles bearing tri-, tetra-, and pentacoordinated phosphorus atoms derived from 2-(2-aminophenyl)-1H-benzimidazol (1). The presence of three different N-H protons allowed to prepare different compounds by selective substitution. Molecules with two (endo and exocyclic) phosphorus atoms were prepared. The free anilinic proton is the most reactive to substitution reactions, followed by the benzimidazolic, and then the anilinic proton involved in the hydrogen bond. Substitution of the exo-anilinic proton of 1 by Ph₂PCl leads a precursor with a hydrogen bond forming a six-membered ring, which could be substituted by other groups giving more complex molecules. A pentacoordinated phosphorus compound was obtained after oxidative addition of 3,5-di-tert-butyl-1,2-benzoquinone to P(III) heterocycle.

Full text of DOI:10.1002/hc.20022

Heteroatom Chemistry
Volume 15, Number 4, 2004
Phosphorus Heterocycles from
2-(2-Aminophenyl)-1H-benzimidazole
Julio Herna´ndez-D´ıaz, Angelina Flores-Parra,
and Rosalinda Contreras
Departamento de Quı´mica, Centro de Investigacio´n y de Estudios Avanzados del IPN, A.P. 14-740,
Me´xico D. F., CP 07000 Me´xico
Received 27 August 2003; revised 23 February 2004
cal interest. Compound 1 presents antipoliomielitic
ABSTRACT: We report the syntheses of unsaturated
[1], triquinocide [2], and fungicide [3] activities and
six-membered heterocycles bearing tri-, tetra-, and pen-
benzimidazoquinazolines derived from 1 have antin-
tacoordinated phosphorus atoms derived from 2-(2-
flamatory [4] and antitumoral [5,6] activities. Com-
aminophenyl)-1H-benzimidazol (1). The presence of
pound 1 has one basic pyridinic type nitrogen and
three different N H protons allowed to prepare dif-
three labile hydrogen atoms, which can be substi-
ferent compounds by selective substitution. Molecules
tuted by heteroelements. Because of these features,
with two (endo and exocyclic) phosphorus atoms were
compound 1 is a good candidate to prepare new het-
prepared. The free anilinic proton is the most reac-
erocycles by substitution of the N H protons and
tive to substitution reactions, followed by the benz-
N-coordination by atoms of 15 group as is shown in
imidazolic, and then the anilinic proton involved in
Scheme 1. Some coordination compounds derived
the hydrogen bond. Substitution of the exo-anilinic
from 1 are known (Sn(IV) [7], U(VI) [8], Fe(II) [9],
proton of 1 by Ph2PCl leads a precursor with a hy-
Sn(IV), Ti(IV), and V(IV) [10], Fe(III) [11], Ni(II)
drogen bond forming a six-membered ring, which
and Pd(II) [12]) as well as some boron heterocy-
could be substituted by other groups giving more
cles [13]. But, to our knowledge there are no reports
complex molecules. A pentacoordinated phosphorus
of phosphorus compounds derived from 1, this and
compound was obtained after oxidative addition of
the complexity of the ligand guarantees interesting
3,5-di-tert-butyl-1,2-benzoquinone to P(III) heterocy-
results, in particular that uncommon unsaturated
ꢀ
C
cle.
2004 Wiley Periodicals, Inc. Heteroatom Chem
six-membered ring phosphorus heterocycles could
be prepared. Therefore, we decided to explore reac-
tions of 1 and phosphorus reagents in order to pre-
pare heterocycles bearing tri-, tetra-, and pentacoor-
dinated phosphorus atoms. The structures were as-
15:321–332, 2004; Published online in Wiley InterScience
(www.interscience.wiley.com). DOI 10.1002/hc.20022
1
signed from the 31P NMR data and 2D H/1H COSY,
INTRODUCTION
1H/13C HETCOR, 1H/13C COLOQ, and 1H/13C HMBC
1
experiments. In DMSO-d6, H and 13C NMR spec-
2-(2-Aminophenyl)-1H-benzimidazole (1) is a poly-
functional molecule of pharmacological and chemi-
tra of 1 show 8 and 13 signals for aromatic pro-
tons and carbon atoms respectively, this means that
the structure of 1 in solution is the same that in the
solid state and that the hydrogen bond is very strong
[Esparza Ruiz, A.; Herna´ndez-D´ıaz, J.; Flores-Parra,
A.; Contreras, R. (paper in preparation)]. Two broad
1H signals at 7.32 and 12.72 ppm in a 2:1 ratio were
Correspondence to: Rosalinda Contreras; e-mail: rcontrer@
mail.cinvestav.mx.
Contract grant sponsor: Conacyt-Mexico.
Contract grant sponsor: Conacyt and Cinvestav-Mexico.
2004 Wiley Periodicals, Inc.
c
ꢀ
321

322 Herna´ndez-D´ıaz, Flores-Parra, and Contreras
SCHEME 1 Possible heterocycles from compound 1.
observed and therefore assigned to anilinic NH2 and
imidazole N H protons respectively.
+127.3 ppm presents a 2 × 13 pattern resulting from
coupling with the ring phosphorus atom and with
12 isochronous NMe2 protons [3 J(31P, 1H) = 9.5 Hz]
for the exocyclic phosphorus, whereas the signal at
+63.5 ppm was a doublet of heptets [3 J(31P, 1H) =
9.2 Hz]. Similar coupling constants were reported
for tris- [15–18] and tetraphosphazanes [19]. After
some days, compound 3 produced the new species
4 as result of the endocyclic phosphorus oxidation,
Scheme 2.
X-ray diffraction structure of 1 was recently de-
termined by us [Esparza Ruiz, A.; Herna´ndez-D´ıaz,
J.; Flores-Parra, A.; Contreras, R. (paper in prepa-
ration)]. In the solid state, compound 1 exists as
an almost planar molecule with a strong hydrogen
bond. Phosphorus heterocycles derived from 2-(2-
hydroxyphenyl)-1H-benzimidazole are reported in
this journal [14].
Reactions with PhPCl2. Because of the lower
N H proton reactivity toward a second substitu-
tion by another phosphorus atom in compound
2, it was expected that equimolar reaction of 1
with PhPCl2 could give exclusively heterocycle 5,
which effectively was observed in the reaction per-
formed in n-hexane–toluene (90:10), its 31P reso-
nance is similar to that reported for a diazaphospho-
rinone with the same phosphorus connectivity [20],
Scheme 3.
RESULTS AND DISCUSSION
Tricoordinated Phosphorus Compounds
Reaction of 1 with P(NMe2)3. Transamination
reactions of 1 with P(NMe2)3 in equimolar ratio and
in excess of the phosphorus reagent yield heterocy-
cles 2 and 3 respectively as red oils, sensitive to-
ward oxygen and moisture, Scheme 2. 31P NMR spec-
trum of 2 showed a doublet of heptets by phosphorus
coupling to NH and NMe2. Compound 3 presented
When a similar reaction was made in toluene
and NEt3, three new compounds were observed, 6,
1
two doublets at the 31P{ H} spectrum. The signal at
SCHEME 2 31P NMR data of compounds 2–4.

Phosphorus Heterocycles from 2-(2-Aminophenyl)-1H-benzimidazole 323
SCHEME 3 Synthesis and 31P NMR data of compounds 5–7.
7, and PhP(NHAr)2(8). One singlet at +137.2 (20%)
is characteristic for a PhPClN group and was as-
signed to compound 6 (for example PhPClNMe2, δ
31P + 141.0 ppm [21]). Another singlet at +55.3 (20%)
corresponds to 8 according to similarity with re-
ported bis-(benzimidazol-1-yl)-phenylphosphine (δ
31P = +50.2 ppm [22]) and bis(anilide)phenyl phos-
phine {PhP(NHPh2)2, δ 31P = + 46.8 ppm [23]}.
The two doublets at +137.2 and +63.3 ppm [40%,
2 J(31P, 31P)] = 257.8 Hz correspond to the heterocy-
cle 7, Scheme 3.
Compound 9 is not stable, after solvent elimination
a complex mixture of non identified products with δ
31P between +162 and +50 ppm was obtained.
Reaction with Ph2PCl. Equimolar reaction, at
rt, of 1 and Ph2PCl in toluene and NEt3 affords a
main product whose 31P spectra showed a singlet at
1
+28.7 ppm. H NMR spectrum presented two NH
resonances, a singlet at 10.77 ppm and a doublet at
10.59 ppm with a coupling 2 J(31P, 1H) of 7.32 Hz,
from these observations we concluded that the
structure of compound 10 results from phosphorus
substitution of the exo-anilinic N H, Scheme 5.
31P NMR data of 10 are similar to those of the
Reaction with PCl3. Addition of one equivalent
or an excess of PCl3 to ligand 1, at rt (or at −78◦C), in
toluene (or in a 90:10 n-hexane–toluene mixture) and
NEt3 affords only one product, which presents in the
1
aminophosphine [Ph2PNHPh, δ H = 4.18 ppm (d,
2 J[31P, 1H] = 7.70 Hz), δ 31P = 29.4 ppm] [26]. The
1H chemical shift of the P N H suggests a strong
intermolecular hydrogen bond. Because of the
presence of two N H protons and a Ph2P acting
1
31P{ H} spectrum two doublets that correspond to 9,
Scheme 4. Exocyclic phosphorus atom has a simi-
lar chemical shift to Cl2P-N(Me)Ph [24]. The large
2 J(31P, 31P) coupling constant values of 4 (142.3 Hz),
7 (127.8 Hz), and 9 (153.8 Hz) suggest a trans confor-
mation derived from the P-lone pair orientation with
regard the endocyclic phosphorus atom [15–19], as
can be modeled in the PM3 program for 9 [25], Fig. 1.
FIGURE 1 Model of compound 9 calculated using the PM3
program [25].
SCHEME 4 Synthesis and 31P NMR data of compound 9.

324 Herna´ndez-D´ıaz, Flores-Parra, and Contreras
SCHEME 5 Synthesis and 31P NMR data of compounds 10 and 11.
as a protecting group, compound 10 could be an
and +44.1 ppm [1 J(31P, 77Se) = 896.6 Hz] (13). In the
1H coupled 31P NMR spectra, 12 and 13 gave hep-
tets in the spectrum range observed for one of the
few known examples of unsaturated six-membered
phosphorus ring, as reported by Neda et al. [28]. 77Se
NMR spectra of 13 showed a doublet at −161.3 ppm
excellent precursor to selectively synthesize six-
membered ring heterocycles by proton substitution.
Equimolar reaction of 10 and PhPCl2 in NEt3 affords
quantitatively heterocycle 11, Scheme 5. 31P NMR
spectrum showed two doublets, the structure was
confirmed by the absence of the N H in the 1H
spectrum and the mass spectrometry (m/z = 499.30).
1
with J(77Se, 31P) = 895.3 Hz. Because of their high
stability, compounds 12 and 13 were completely
characterized by NMR and mass spectrometry (m/z
= 314.25 for 12 and m/z = 362.20 for 13).
Similar data was found for PhP(a)-[NEtP(b)-Ph2]2
δ
31
31
P
= +104.3 and δ
P
(b)
= 52.8 ppm [27].
(a)
Compound 10 was instantaneously and quan-
titatively oxidized at rt to 14 [+49.5 ppm] and 15
Tetracoordinated Phosphorus Compounds
1
[+45.3 ppm, J(31P, 77Se) = 774.4 Hz], Scheme 6. In
1
the 31P H-coupled spectra both signals displayed a
Next step in this research was to synthesize tetra-
coordinated phosphorus compounds oxidized with
sulfur and selenium, which are more stable to mois-
ture. Additional NMR information can be obtained
from the selenium derivatives.
doublet of multiplets [2 J(31P, 1H) of 11.4 and 9.4 Hz
for 14 and 15 respectively]. A doublet at −249.1 ppm,
1 J(31P, 77Se) = 774.0 Hz in the 77Se spectra confirmed
phosphorus oxidation in 15. 1H resonances of the NH
protons indicate the hydrogen bond and phosphorus
coupling [δ = 12.30 ppm, 2 J(31P, 1H) = 10.2 Hz for
Addition of equimolar amounts of elemental sul-
fur or selenium powder to compound 2 in refluxing
toluene produces 12 or 13 derivatives, Scheme 6.
2
14 and δ = 12.32 ppm, J(31P, 1H) = 9.9 Hz for 15].
1
31P{ H} NMR spectra showed singlets at +48.1 (12)
The IR spectra showed characteristic bands for N H
SCHEME 6 Oxidated compounds 12–21.

Phosphorus Heterocycles from 2-(2-Aminophenyl)-1H-benzimidazole 325
19 after 48 h of stirring at rt. 31P NMR reaction mon-
itoring revealed slow oxidation of 11 even in excess
of sulfur or selenium. In both cases only exocyclic
phosphorus was selectively oxidized, Scheme 6. The
protons involved in hydrogen bond at 3207 and 3227
cm−1 for 14 and 15 respectively. In addition, 14 and
15 are ideal candidates to build six-membered het-
erocycles, with the advantage of their stability. It is
clear that higher reactivity of 10 toward sulfur and
selenium is due to a better P-lone pair availability
compared with 2.
1
last conclusion originated from 31P{ H} NMR spec-
tra analysis, which gives two doublets at +69.8 and
+57.9 ppm with 2 J(31P, 31P) = 96.7 Hz for 18 and
at +69.5 [1 J(31P, 77Se) = 795.2 Hz] and +57.7 ppm
with 2 J(31P, 31P) = 98.8 Hz for 19. Low frequency sig-
nals produced a broad doublet whereas those at high
frequency exhibited a doublet of quintuplets pattern
Equimolar addition of S and Se powder to a
CDCl3 solution of 3 at rt immediately affords chalco-
genides 16 and 17, which showed two series of dou-
blets at +62.3 and +75.1 ppm [2 J(31P, 31P) = 95.8] for
16 and +61.9 and +74.0 ppm [2 J(31P, 31P) = 96.3 Hz]
1
by H coupling. Chemical shifts of 31P, 2 J(31P, 31P),
1
for 17 in the 31P{ H} spectra, Scheme 6. Analysis
and 1 J(31P, 77Se) values of 19 are similar to reported
diphosphanes selenides [29].
of 31P spectrum of 17 revealed that exocyclic phos-
phorus atom was selectively oxidized, because only
the doublet at +74.0 ppm gives the selenium cou-
pling 1 J(31P, 77Se) = 830 Hz. The signal at +61.9 ppm
showed a doublet of heptets by coupling to NMe2
protons. 31P signals of 16 were assigned by compari-
son with 17. Even in an excess of S or Se and stirring
at rt for 24 h endocyclic phosphorus atoms were not
oxidized. Compounds 16 and 17 were only slightly
stable toward oxygen and moisture, because they still
have a highly reactive P(III) atom.
Addition of excess of sulfur to 18 and reflux-
ing in toluene for 1 h gave compound 20 with two
2
doublets at +68.2 and +50.4 ppm and J(31P, 31P) =
12.1 Hz. By comparison to 18, signal at +50.4 ppm
was assigned to the endocyclic phosphorus. Com-
pound 20 is very stable to environment exposition
and therefore it could be a potential candidate to
coordinate metal ions [29]. Reaction of 19 with an
excess of selenium in refluxing toluene for 1 h pro-
duced the diselenium derivative 21 in a 30 % yield,
Scheme 7. Hydrolysis of the reaction mixture gave a
31P resonance at +48.5 ppm 1 J(31P, 77Se) = 880.7 Hz
On the other hand, reaction of a toluene solu-
tion of 11 and sulfur and selenium yielded 18 and
SCHEME 7 Hydrolysis of compounds 19 and 21.

326 Herna´ndez-D´ıaz, Flores-Parra, and Contreras
(50%) with another singlet at +71.2 ppm (≈15%)
[31]. These two products correspond to 22 and 23
respectively, Scheme 7.
pendently of the substituents nature [35]. According
to this, it is expected that in phosphoranes 24 the
two rings keep apical-equatorial position with the N-
Me2 group located at the equatorial site. It has been
reported that apicophilicity of a group depends on
its electronegativity, ꢀ interactions with phosphorus,
and steric factors. High electronegativity and small
size favor high apicophilicity of a substituent [35].
These facts allow to propose that anilinic nitrogen is
located at the apical position of the tbp. This hypoth-
esis was confirmed from the P H coupling constant
analysis through two and three bonds. In the 31P H-
coupled spectrum, each signal of 24 was split in an
heptet instead of doublet of heptets, with constants
3 J(31P, 1H) = 11.8 and 11.5 Hz. This result means
that N H proton is not coupled to phosphorus. If the
N H would be located in an equatorial position its
2 J(31P, 1H) constant would be similar to those found
[2 J(31P, 1H) = 17.2 Hz] for the phosphorane derived
from o-aminophenol [36]. On the other hand, the
magnitude of the coupling constant 3 J(31P, 1H) be-
tween P and N-Me2 in 24 is practically equal to that
of the phosphorane with the same connectivity re-
ported by Neda et al. [28]. According to these facts,
it is clear that in 24 the N-Me2 group is located in
the equatorial position of the tbp, whereas anilinic
nitrogen is apical due to absence of a coupling be-
tween N H proton and phosphorus. This behavior
is similar to that found in the hydrospirophospho-
rane derived from o-aminophenol [36], where cou-
pling 2 J(31P, 13C) through equatorial substituent is
big [16.5 Hz] and null through the axial one.
Compounds 18 and 19 were unstable to oxygen
and moisture. Water addition to a CDCl3 solution
1
of 19 affords 31P{ H} signals at +18.2 [1 J(31P, 1H)
= 522.2 Hz] assigned to PhPH(O)OH species [30]
1
and +46.8 ppm J(31P, 77Se) = 754.9 Hz which cor-
responds to compound 15, Scheme 7.
Pentacoordinated Phosphorus Compounds
Transamination reaction between two equivalents
of 1 and one of P(NMe2)3 should produce the
corresponding hydrospirophosphorane. However,
reactions in benzene (stirring 24 h at rt or refluxing
for 4 h) were not successful. The only product was
the P(III) compound 2, Scheme 2. A first explanation
of the lack of reactivity was found in the report that
spirophosphoranes containing a P H bond are not
stable if they are constituted by rings with more than
five atoms [32,33]. A second could be the rigidity of
the ligand once it is bonded to phosphorus and a
third one is the fact that two electrodonor nitrogen
atoms, which have a preference for the equatorial
sites of the tbp, would be located at the apical
positions.
In contrast to transamination reaction, oxida-
tive addition of 3,5-di-tert-butyl-1,2-benzoquinone to
heterocycle 2 immediately and quantitatively affords
phosphoranes 24, easily identified in the 31P spec-
trum as two singlets, in a 60:40 ratio, at −55.6 and
−56.6 ppm respectively. Asymmetry of 3,5-di-tert-
butylcatecholate fragment is responsible for observ-
ing two signals for 24. Chemical shifts of 24 are near
to those of the reported phosphoranes with the same
connectivity [34], Scheme 8.
CONCLUSION
We have found that compound 1 forms unsatu-
rated six-membered phosphorus heterocycles. The
presence of three different N H protons allowed to
prepare different compounds by selective substitu-
tion. In compound 1, the free anilinic proton is most
It is known that in phosphoranes where the phos-
phorus atom is part of 4–7 membered-rings, the rings
prefer an apical-equatorial position in the tbp, inde-
SCHEME 8 Synthesis and 31P NMR data of spirophosphoranes 24.

Phosphorus Heterocycles from 2-(2-Aminophenyl)-1H-benzimidazole 327
reactive to substitution reactions, followed by the
benzimidazolic, and finally the anilinic proton in-
volved in the hydrogen bond.
P[NMe2]3 was less reactive but more selective in
the heterocyclic formation, this behavior could be ex-
plained considering that NMe2 group is not a good
leaving group as chlorine is. Substitution of only one
proton of 1 by Ph2PCl leads to a hydrogen bond
which could be substituted by other groups giving
more complex molecules.
Compound 1 also allows to prepare derivatives
with two kind of phosphorus atoms, endo- and ex-
ocyclic. This different reactivity can be exploited to
prepare mixed compounds which, together with the
reported here, can be used as potential ligands in co-
ordination chemistry.
Dimethyl-(5H-5,6a,11-triaza-6-phospha-benzo-
[a]fluoren-6-yl)-amine (2)
To a suspension of 100 mg (0.48 mmol) of compound
1 in 10 ml of toluene, 0.09 ml (78 mg, 0.48 mmol)
of P[NMe2]3 were added. This mixture was heated
under reflux until the calculated amount of Me2NH
was evolved and titred with a 1 N HCl solution. The
resulting solution was filtered and the solvent evapo-
rated in vacuum to produce 130 mg (96%) of a red oil.
13C NMR (CDCl3): δ 149.8 (d, 2 JPC 6.2 Hz, C2), 119.0
3
(C4), 123.1 (C5), 122.4 (C6), 110.9 (d, JPC 11.4 Hz,
C7), 136.0 (d, 2 JPC 18.7 Hz, C8), 144.6 (d, 3 JPC 4.2 Hz,
2
C9), 114.5 (C10), 141.0 (d, JPC 10.4 Hz, C11), 117.3
(C12), 131.4 (C13), 120.3 (C14), 126.7 (C15), 37.4 (d,
1
2 JPC 18.7 Hz, N CH3). H NMR (CDCl3): δ 7.82 (d,
JHH 7.68 Hz, H4), 7.29 (dd, JHH 6.96 and 8.04 Hz,
H5), 7.25 (dd, JHH 7.72 and 7.68 Hz, H6), 7.60 (d,
JHH 8.08 Hz, H7), 6.93 (d, JHH 8.44 Hz, H12), 7.23 (t,
JHH 7.68 Hz, H13), 6.96 (t, JHH 7.68 Hz, H14), 8.38
(d, JHH 8.32 Hz, H15), 2.39 (d, 3 JPH 9.51 Hz, N CH3),
6.58 (d, 2 JPH 37.34 Hz, P N H). MS: m/z (%): 282.25
(4) [M]+, 238.20 (29), 237.20 (14), 210.35 (17), 209.30
(100), 208.35 (27).
Because of phosphorus acidity in a P(III) deriva-
tive, it was possible to prepare pentacoordinated
phosphorus compounds by oxidative addition of a
quinone heterocycle.
EXPERIMENTAL
All experiments were carried out under dry nitrogen
atmosphere. Solvents were dried and freshly distilled
under N2 atmosphere according to reported proce-
dures [37]. NMR spectra were recorded in DMSO-
d6 and CDCl3 on a Jeol GSX-270, Jeol Eclipse 400,
and Bruker 300 spectrometers. δ are given in ppm
and referred to Me4Si, H3PO4 (aq., 85%) [δ 31P = 0],
Dimethyl-(5-[bis(dimethylamino)phosphanyl]-
5,6a,11-triaza-6-phospha-benzo[a]fluoren-6-yl)-
amine (3)
It was synthesized following the same procedure as
for 2 using 300 mg (1.43 mmol) of 1 and five equiva-
lents (1.30 ml, 1.17 g, 7.17 mmol) of P(NMe2)3. Five
hundred and sixty milligrams (97%) of 3 were iso-
1
and neat Me2Se [δ 77Se = 0]. Assignment of H and
1
13C NMR data were supported by 2D H/1H COSY,
1H/13C HETCOR, 1H/13C COLOQ, and 1H/13C HMBC
experiments. IR spectra were taken in KBr disc us-
ing a FT Spectrum GX Perkin Elmer spectrometer. EI
mass spectra were performed in a Hewlett-Packard
HP 5989A spectrometer. Melting points were deter-
mined on a Mel Temp II equipment in an open cap-
illar tube and are not corrected. Elemental analyses
were carried out in a Flash 1112 Thermo Finnigan
analyzer.
2
lated as a red oil. 13C NMR (CDCl3): δ 149.8 (d, JPC
4.2 Hz, C2), 119.2 (C4), 123.1 (C5), 122.3 (C6), 111.1
(d, 3 JPC 11.2 Hz, C7), 136.4 (d, 2 JPC 20.3 Hz, C8), 144.7
(d, 3 JPC 3.3 Hz, C9), 120.4 (C10), 141.7 (dd, 2 JPC 13.4
and 6.6 Hz, C11), 121.3 (d, 3 JPC 22.3 Hz, C12), 130.8
(C13), 122.4 (C14), 126.9 (C15), 39.3 (d, 2 JPC 20.7 Hz,
2
P N(CH3)2), 38.8 (d, JPC 18.9 Hz, P [N(CH3)2]2),
38.7 (d, 2 JPC 18.7 Hz, P-[N(CH3)2]2). 1H NMR (CDCl3):
δ 7.87 (d, JHH 7.70 Hz, H4), 7.32 (dd, JHH 8.15 and
7.70 Hz, H5), 7.32 (dd, JHH 8.15 and JHH 7.31 Hz,
H6), 7.74 (d, JHH 7.46 Hz, H7), 7.40 (br, H12), 7.39
(br, H13), 7.18 (t, JHH 7.94 Hz, H14), 8.46 (d, JHH
7.99 Hz, H15), 2.41 (d, 3 JPH 9.96 Hz, P N(CH3)2), 2.73
(d, 3 JPH 8.99 Hz, P-[N(CH3)2]2), 2.47 (d, 3 JPH 9.11 Hz,
P-[N(CH3)2]2).
2-(2-Aminophenyl)-1H-benzimidazol (1)
Compound 1 was prepared according to described
method [38]. 13C NMR (DMSO-d6): δ (ppm) 153.1
(C2), 118.7 (C4), 122.0 (C5), 122.8 (C6), 111.3 (C7),
134.1 (C8), 143.5 (C9), 110.7 (C10), 148.8 (C11), 116.7
(C12), 130.9 (C13), 115.6 (C14), 127.8 (C15). 1H NMR
(DMSO-d6): δ (ppm) 7.69 (t, JHH 7.04 Hz, H4), 7.22 (br,
H5), 7.22 (br, H6), 7.57 (br, H7), 6.90 (d, JHH 7.92 Hz,
H12), 7.18 (dd, JHH 7.92 and JHH 7.44 Hz, H13), 6.69
(t, JHH 7.48 Hz, H14), 7.92 (d, JHH 7.92 Hz, H15), 7.32
(br, N H2), 12.72 (br, N H).
5H-6-Phenyl-5,6a,11-triaza-6-phospha-
benzo[a]fluorene (5)
To a suspension of 200 mg (0.96 mmol) of 1 in
15 ml of a 90:10 n-hexane–toluene solvent mixture
and 0.27 ml (193 mg, 1.91 mmol) of NEt3, 0.13 ml

328 Herna´ndez-D´ıaz, Flores-Parra, and Contreras
2
(171 mg, 0.96 mmol) of PhPCl2 dissolved in 3 ml of
toluene were added at rt. The reaction mixture was
stirred overnight at rt. According to 31P NMR spec-
tra of an aliquot, compound 5 was formed in quan-
titative yield. It was characterized in solution be-
cause vacuum solvent elimination produces a white
solid, which is a complex mixture of non identified
products.
C7), 136.3 (d, JPC 18.7 Hz, C8), 144.4 (C9), C10
2
2
(not observed.), 143.6 (dd, JPC 19.7, JPC 5.2, C11),
124.6 (d, 3 JPC 16.6 Hz, C12), 130.6 (C13), 124.6 (C14),
127.1 (C15), 137.8 (d, 1 JPC 18.7 Hz, Ci), 133.5 (d, 2 JPC
23.9 Hz, Co), 129.1 (d, JPC 8.3 Hz, Cm), 129.7 (Cp)
(P Ph), 137.7 (d, JPC 17.6 Hz, Ci), 131.2 (d, JPC
3
1
2
3
18.7 Hz, Co), 128.6 (d, JPC 5.2 Hz, Cm), 128.5 (d,
3 JPC 5.2 Hz, Cm), 129.5 (Cp), 129.2 (Cp) (P Ph2). 1H
NMR (CDCl3): δ 7.93 (d, JHH 7.92 Hz, H4), 7.33 (dd,
JHH 7.91 and 6.26 Hz, H5), 7.36 (dd, JHH 7.59 and
6.26 Hz, H6), 7.47 (d, JHH 7.59 Hz, H7), 7.59 (d, JHH
8.23 Hz, H12), 7.49 (m, H13), 7.15 (m, H14), 8.29 (d,
JHH 7.27 Hz, H15), 7.78–7.85 (m, Ho), 7.49 (m, Hm),
7.06 (m, Hp) (P Ph), 7.23 (m, Ho), 7.12 (m, Hm), 6.98
(dd, JHH 6.94 and 7.59 Hz, Hm), 6.62 (t, JHH 6.94 Hz,
Hp) (P Ph2). MS: m/z (%): 499.30(5) [M]+, 422.30
(2), 391.30 (13), 315.20 (16), 314.20 (16), 263.25 (20),
262.30 (100), 238.20 (33), 220.20 (24), 209.30 (27),
201.25 (39), 183.20 (38), 154.35 (24).
5-Dichlorophosphanyl-6-chloro-5,6a,11-triaza-
6-phospha-benzo[a]fluorene (9)
The synthesis was performed following the described
procedure for 5 using 200 mg (0.96 mmol) of 1, 0.27
ml (193 mg, 1.91 mmol) of NEt3, and 0.16 ml (262
mg, 1.91 mmol) of PCl3. 31P NMR of an aliquot of
the reaction mixture after overnight stirring showed
quantitative formation of 9. The product was char-
acterized in solution because vacuum solvent elim-
ination affords a complex mixture of non identified
compounds.
Dimethyl-(5H-6-thioxo-5,6a,11-triaza-6-
phospha-benzo[a]fluoren-6-yl)-amine (12)
[2-(1H-Benzoimidazol-2-yl)-phenyl]-
General Procedure. In a 25 ml round bottomed
flask equipped with a reflux condenser, 270 mg (0.96
mmol) of 2 was dissolved in 10 ml of toluene and
31 mg (0.96 mmol) of sulfur was added. This mix-
ture was heated for 2 h at toluene reflux. Then, it
was filtered to eliminate the excess of sulfur. Filtrate
was concentrated in vacuum. Two hundred and ninty
milligrams (97%) of a yellow solid was obtained. mp
196–200◦C. 13C NMR (CDCl3): δ 150.4 (C2), 119.7
(C4), 124.5 (C5), 123.9 (C6), 113.0 (C7), 133.2 (d, 2 JPC
7.3 Hz, C8), 144.5 (d, 3 JPC 12.5 Hz, C9), 112.8 (C10),
diphenylphosphanyl-amine (10)
It was prepared using the same procedure as for 5
from 200 mg (0.96 mmol) of 1, 0.27 ml (193 mg, 1.91
mmol) of NEt3, and 0.17 ml (211 mg, 0.96 mmol) of
Ph2PCl. Resulting mixture reaction after 4 h stirring
at rt was filtered to eliminate NEt3HCl. The liquid
portion was concentrated in vacuum to obtain 340
mg (90%) of 10 as a bright red oil. 13C NMR (CDCl3):
δ 152.2 (C2), 118.9 (C4), 123.1 (C5), 122.2 (C6), 110.9
2
(C7), 133.2 (C8), 143.0 (C9), 147.9 (d, JPC 16.9 Hz,
C11), 116.3 (d, 3 JPC 26.1 Hz, C12), 130.9 (C13), 117.8
(C14), 127.1 (C15), 140.7 (d, 1 JPC 10.8 Hz, Ci), 131.4
(d, 2 JPC 21.5 Hz, Co), 128.6 (d, 3 JPC 7.7 Hz, Cm), 129.0
2
3
138.9 (d, JPC 3.1 Hz, C11), 117.3 (d, JPC 11.4 Hz,
C12), 132.0 (C13), 122.3 (C14), 127.3 (C15), 37.8 (d,
2 JPC 6.2 Hz, N CH3). 1H NMR (CDCl3): δ 7.85 (d, JHH
7.27 Hz, H4), 7.39 (ddd, JHH 7.27, 7.59, and 1.65 Hz,
H5), 7.33 (ddd, JHH 7.59, 6.92, and 1.30 Hz, H6),
7.77 (dd, JHH 6.92, and 1.65 Hz, H7), 6.91 (d, JHH
8.27 Hz, H12), 7.28 (ddd, JHH 7.24, 8.24, and 1.30 Hz,
H13), 7.09 (dd, JHH 7.24, and 7.92 Hz, H14), 8.40 (dd,
1
(Cp). H NMR (CDCl3): δ 7.33 (d, JHH 6.96 Hz, H4),
7.27 (t, JHH 6.96 Hz, H5), 7.27 (t, JHH 6.96 Hz, H6),
7.66 (d, JHH 8.44 Hz, H7), 7.65 (d, JHH 8.44 Hz, H12),
7.28 (t, JHH 6.96 Hz, H13), 6.77 (dd, JHH 7.68, JHH
7.32, H14), 7.80 (d, JHH 7.72, H15), 10.77 (s, N H),
2
3
3
10.59 (d, JPH 7.32 Hz, P N H), 7.74 (ddd, JPH
8.04, JHH 7.68 and 1.84 Hz, Ho), 7.42 (m, Hm), 7.40
(m, Hp).
JHH 7.92. and 1.32 Hz, H15), 2.83 (d, JPH 12.54 Hz,
N CH3), 6.50 (d, 2 JPH 8.56 Hz, P N H). MS: m/z (%):
314.25 (60) [M]+, 270.20 (9), 255.95 (10), 239.20 (15),
238.20 (100), 209.30 (15), 160.10 (6), 91.15 (44). IR
(KBr), ꢁ (cm−1): 3395, 3221, 2918, 2849, 1690, 1615.
5-Diphenylphosphanyl-6-phenyl-5,6a,11-triaza-
6-phospha-benzo[a]fluorene (11)
Dimethyl-(5H-6-selenoxo-5,6a,11-triaza-6-
phospha-benzo[a]fluoren-6-yl)-amine (13)
To a toluene solution of 376 mg (0.96 mmol) of 10
and 0.27 ml (193 mg, 1.91 mmol) of NEt3, 0.13 ml
(171 mg, 0.96 mmol) of PhPCl2 were added at rt. Af-
ter 1 h of stirring, the reaction mixture was filtered
and the solvent evaporated to give 470 mg (98%) of
a brown oil. 13C NMR (CDCl3): δ 149.6 (C2), 119.6
To a solution of 270 mg (0.96 mmol) of 2 in toluene,
76 mg (0.96 mmol) of selenium was added and the
suspension refluxed for 4 h. Three hundred and thirty
milligrams (96%) of a yellow solid were obtained.
mp 190–192◦C. 13C NMR (CDCl3): δ 149.9 (C2), 119.8
3
(C4), 123.5 (C5), 123.5 (C6), 111.2 (d, JPC 7.3 Hz,

Phosphorus Heterocycles from 2-(2-Aminophenyl)-1H-benzimidazole 329
3
(C4), 124.5 (C5), 123.9 (C6), 113.1 (C7), 133.2 (d,
142.0 (C9), 116.0 (d, JPC 7.3 Hz, C10), 141.6 (C11),
3
2 JPC 8.3 Hz, C8), 144.6 (d, JPC 11.4 Hz, C9), 112.9
119.2 (d, 3 JPC 7.3 Hz, C12), 130.0 (C13), 120.5 (C14),
127.6 (C15), 133.6 (d, 1 JPC 18.7 Hz, Ci), 131.7 (d, 2 JPC
12.5 Hz, Co), 128.9 (d, JPC 12.5 Hz, Cm), 132.3 (d,
2
3
(C10), 138.5 (d, JPC 5.2 Hz, C11), 117.4 (d, JPC
3
10.4 Hz, C12), 132.0 (C13), 122.5 (C14), 127.3 (C15),
2
1
4 JPC 2.1 Hz, Cp). 1H NMR (DMSO-d6): δ 7.29 (d, JHH
7.24 Hz, H4), 7.20 (dd, JHH 7.27 and 7.59 Hz, H5),
7.17 (dd, JHH 7.56 and 7.27 Hz, H6), 7.49 (br, H7),
7.28 (d, JHH 8.24 Hz, H12), 7.14 (dd, JHH 8.27 and
7.24 Hz, H13), 6.98 (dd, JHH 7.24 and 7.92 Hz, H14),
8.05 (m, H15), 12.84 (s, N H), 12.32 (d, 2 JPH 8.89 Hz,
P N H), 8.07 (m, Ho), 7.52 (br, Hm), 7.52 (br, Hp).
38.0 (d, JPC 5.2 Hz, N-(CH3)2). H NMR (CDCl3):
δ (ppm) 7.84 (dd, JHH 6.59 and 1.32 Hz, H4), 7.39
(ddd, JHH 6.94, 7.59, and 1.65 Hz, H5), 7.34 (ddd, JHH
6.92, 7.59, and 1.32 Hz, H6), 7.78 (dd, JHH 6.92, and
1.65 Hz, H7), 6.91 (d, JHH 7.92 Hz, H12), 7.28 (dd,
JHH 7.59, and 7.92 Hz, H13), 7.09 (dd, JHH 7.59, and
7.92 Hz, H14), 8.39 (dd, JHH 7.92, and 1.65 Hz, H15),
3
77Se NMR: −249.1 (d, JPSe 770.0 Hz). MS: m/z (%):
1
2.87 (d, JPH 12.86 Hz, N(CH3)2), 6.47 (br, P N H).
1
77Se NMR: −161.3 (d, JPSe 895.3 Hz). MS: m/z (%):
473.05 (16) [M]+, 409.20 (6), 393.15 (28), 392.15 (90),
391.15 (24), 332.15 (9), 317.15 (22), 316.10 (100),
265.00 (14), 238.15 (35), 209.15 (43). C25H20N3PSe
(472.39) calcd.: C, 63.57; H, 4.27; N, 8.90. Found: C,
63.82; H, 4.38; N, 8.84. IR (KBr), ꢁ (cm−1): 3227, 3051,
2918, 2849, 1583.
362.20 (14) [M]+, 282.25 (3), 239.20 (16), 238.20
(100), 237.25 (37). C15H15N4PSe.2 (C3H6O) (477.40)
calcd.: C, 52.83; H, 5.69; N, 11.73. Found: C, 53.10; H,
5.69; N, 12.30. IR (KBr), ꢁ (cm−1): 3381, 3249, 2918,
2849, 1677, 1618.
[2-(1H-Benzoimidazol-2-yl)-phenyl]-
diphenylthiophosphinoyl-amine (14)
Dimethyl-(5-[bis(dimethylamino)thiophos-
phinoyl]-5,6a,11-triaza-6-phospha-
benzo[a]fluoren-6-yl)-amine (16)
To a solution of 1.88 g (4.78 mmol) of 10 in 15 ml of
toluene, 153 mg (4.78 mmol) of sulfur was added
and the suspension stirred for 5 min at rt. Com-
pound 14 precipitated as beige solid, which was fil-
tered, washed with acetone, and dried in vacuum;
1.95 g (96 %) of 14 were obtained. mp 268–272◦C.
13C NMR (DMSO-d6): δ 151.8 (C2), 118.3 (C4), 123.5
(C5), 122.4 (C6), 111.6 (C7), 135.5 (C8), 142.1 (C9),
115.7 (d, 3 JPC 7.3 Hz, C10), 141.6 (C11), 119.1 (d, 3 JPC
7.3 Hz, C12), 130.2 (C13), 120.4 (C14), 127.6 (C15),
133.9 (d, 1 JPC 11.4 Hz, Ci), 131.5 (d, 2 JPC 11.4 Hz, Co),
129.0 (d, 3 JPC 13.5 Hz, Cm), 132.2 (d, 4 JPC 3.1 Hz, Cp).
1H NMR (DMSO-d6): δ 7.33 (d, JHH 7.24 Hz, H4), 7.22
(dd, JHH 7.24 and 7.56 Hz, H5), 7.19 (t, JHH 7.56 Hz,
H6), 7.50 (br, H7), 7.31 (d, JHH 8.24 Hz, H12), 7.13
(dd, JHH 8.24 and 6.92 Hz, H13), 6.97 (t, JHH 7.27 Hz,
To a CDCl3 solution of 60 mg (0.15 mmol) of 3 in a
NMR tube, 5.0 mg (0.16 mmol) of sulfur was added
followed by vigorous stirring. 31P NMR spectra regis-
tered immediately showed quantitative formation of
16, which was not isolated. 13C NMR (CDCl3): δ 149.3
2
4
(dd, JPC 4.4 and JPC 1.3 Hz, C2), 119.7 (C4), 123.5
(C5), 123.0 (C6), 111.1 (d, 3 JPC 10.9 Hz, C7), 135.9 (d,
2 JPC 22.0 Hz, C8), 144.5 (d, 3 JPC 4.1 Hz, C9), 121.6 (d,
3 JPC 6.3 Hz, C10), 138.4 (dd, 2 JPC 2.9 and 2 JPC 2.0 Hz,
C11), 123.5 (dd, 3 JPC 4.7 and 3 JPC 1.3 Hz, C12), 130.9
(C13), 124.5 (C14), 127.1 (C15), 39.2 (d, 2 JPC 20.7 Hz,
2
P N(CH3)2), 38.7 (d, JPC 8.6 Hz, P[N(CH3)2]2), 38.7
(d, 2 JPC 7.8 Hz, P[N(CH3)2]2). 1H NMR (CDCl3): δ 7.87
(d, JHH 7.63 Hz, H4), 7.36 (dd, JHH 7.36 and 7.59 Hz,
H5), 7.32 (dd, JHH 7.36 and 7.50 Hz, H6), 7.71 (d, JHH
7.50 Hz, H7), 8.09 (d, JHH 8.35 Hz, H12), 7.45 (dd,
JHH 8.23 and 7.40 Hz, H13), 7.29 (dd, JHH 7.70 and
7.40 Hz, H14), 8.41 (d, JHH 7.70 Hz, H15), 2.40 (d,
2
H14), 8.08 (m, H15), 12.87 (s, N H), 12.30 (d, JPH
10.21 Hz, P N H), 8.08 (m, Ho), 7.52 (br, Hm), 7.52
(br, Hp). MS: m/z (%): 425.10 (34) [M]+, 393.20 (18),
392.20 (62), 349.15 (21), 348.15 (94), 317.15 (22),
316.15 (100), 285.15 (8), 269.15 (11), 238.15 (26),
217.15 (37), 139.00 (26). C25H20N3PS (425.50) calcd.:
C, 70.57; H, 4.74; N, 9.88; S, 7.54. Found: C, 70.38; H,
4.90; N, 9.75; S, 7.51. IR (KBr), ꢁ (cm−1): 3207, 3055,
2917, 2849, 1585.
3
3 JPH 10.75 Hz, P N(CH3)2), 2.83 (d, JPH 10.56 Hz,
3
P[N(CH3)2]2), 2.54 (d, JPH 10.84 Hz, P[N(CH3)2]2).
MS: m/z (%): 432.25 (6) [M]+, 388.20 (10), 314.15 (7),
238.15 (19), 237.15 (12), 151.15 (97), 119.15 (100).
Dimethyl-(5-[bis(dimethylamino)selenophos-
phinoyl]-5,6a,11-triaza-6-phospha-
benzo[a]fluoren-6-yl)-amine (17)
[2-(1H-Benzoimidazol-2-yl)-phenyl]-
diphenylselenophosphinoyl-amine (15)
It was obtained in the same way as 16 using 60 mg
(0.15 mmol) of 3 and 12 mg (0.15 mmol) of selenium
in CDCl3. According to the 31P NMR spectra the re-
action was quantitative. Compound 17 was not iso-
It was prepared in the same way as 14 using 1.88 g
(4.78 mmol) of 10 and 378 mg (4.78 mmol) of sele-
nium; 2.18 g (97%) of a beige solid were obtained. mp
270–274◦C. 13C NMR (DMSO-d6): δ 151.8 (C2), 118.3
(C4), 123.5 (C5), 122.4 (C6), 111.6 (C7), 134.8 (C8),
2
lated. 13C NMR (CDCl3): δ 149.1 (dd, JPC 4.3 and
4 JPC 1.4 Hz, C2), 119.6 (C4), 123.4 (C5), 123.0 (C6),

330 Herna´ndez-D´ıaz, Flores-Parra, and Contreras
111.0 (d, 3 JPC 10.9 Hz, C7), 135.8 (d, 2 JPC 22.1 Hz, C8),
144.4 (d, 3 JPC 4.1 Hz, C9), 121.8 (d, 3 JPC 5.9 Hz, C10),
138.1 (t, 2 JPC 2.5 Hz, C11), 123.5 (dd, 3 JPC 4.7 and 3 JPC
1.3 Hz, C12), 130.7 (C13), 124.6 (C14), 127.0 (C15),
39.4 (d, 2 JPC 20.9 Hz, P N(CH3)2), 38.9 (d, 2 JPC 8.7 Hz,
149.6 (C2), 120.0 (C4), 123.7 (C5), 124.0 (C6), 110.0
(d, 3 JPC 6.2 Hz, C7), 136.6 (d, 2 JPC 20.0 Hz, C8), 144.3
2
(C9), 123.4 (C10), 135.9 (dd, JPC 16.9 and 6.7 Hz,
3
C11), 124.8 (d, JPC 4.6 Hz, C12), 130.0 (C13), 125.4
4
(C14), 127.4 (C15), 137.9 (Ci), 132.7 (d, JPC 3.1 Hz,
4
2
1
Co), 132.1 (d, JPC 3.1 Hz, Co), 128.7 (Cm), 128.4
P[N(CH3)2]2), 38.9 (d, JPC 8.3 Hz, P[N(CH3)2]2). H
NMR (CDCl3): δ 7.85 (d, JHH 7.41 Hz, H4), 7.33 (dd,
JHH 7.41 and 7.30 Hz, H5), 7.30 (dd, JHH 7.30 and
7.69 Hz, H6), 7.69 (d, JHH 7.40 Hz, H7), 8.04 (d, JHH
8.32 Hz, H12), 7.43 (dd, JHH 7.34 and 8.32 Hz, H13),
7.28 (dd, JHH 7.77 and 7.32 Hz, H14), 8.39 (d, JHH
1
(Cm), 129.9 (Cp) (P Ph), 135.4 (d, JPC 7.7 Hz, Ci),
135.2 (d, 1 JPC 7.7 Hz, Ci), 133.0 (d, 2 JPC 12.3 Hz, Co),
132.5 (d, 2 JPC 10.0 Hz, Co), 128.6 (d, 3 JPC 3.1 Hz, Cm),
128.5 (Cm), 129.6 (Cp), 129.4 (Cp) (P Ph2). 1H NMR
(CDCl3): δ 8.00 (d, JHH 7.32 Hz, H4), 7.43 (dd, JHH 7.16
and 6.60 Hz, H5), 7.31–7.38 (m, H6, H7), 7.63 (d, JHH
8.04 Hz, H12), 6.94 (dd, JHH 8.04 and 7.32 Hz, H13),
7.03 (dd, JHH 7.72 and 7.32 Hz, H14), 8.22 (d, JHH
7.68 Hz, H15), 7.47–7.51 (m, Ho), 7.31–7.38 (m, Ho,
Hm), 7.16–7.27 (m, Hm), 7.08–7.14 (m, Hp) (P Ph),
3
7.77 Hz, H15), 2.38 (d, JPC 10.73 Hz, P N(CH3)2),
3
3
2.82 (d, JPH 10.92 Hz, P[N(CH3)2]2), 2.54 (d, JPH
11.37 Hz, P[N(CH3)2]2). 77Se NMR: −207.8 (dd, 1 JPSe
3
829.7 and JPSe 8.6 Hz). MS: m/z (%): 480.20 (3)
[M]+, 362.15 (4), 298.20 (3), 238.15 (28), 237.15 (15),
199.15 (12), 119.15 (100).
3
8.00 (dd, JPH 14.27 and JHH 6.96 Hz, Ho), 7.82 (dd,
3 JPH 13.91 and JHH 7.32 Hz, Ho), 7.31–7.38 (m, Hm),
7.08–7.14 (Hm, Hp, Hp). 77Se NMR: −181.8 (dd, 1 JPSe
792.6 and 3 JPSe 6.1 Hz). MS: m/z (%): 579.10 (1) [M]+,
395.00 (39), 393.05 (22), 391.05 (23), 315.20 (22),
314.10 (39), 269.20 (16), 238.15 (100), 186.15 (24),
108.05 (30).
5-Diphenylthiophosphinoyl-6-phenyl-5,6a,11-
triaza-6-phospha-benzo[a]fluorene (18)
It was obtained from reaction of 480 mg (0.96 mmol)
of 11 in toluene and 31 mg (0.96 mmol) of sulfur,
and stirring overnight at rt. 31P NMR showed quan-
titative formation of 18. It was not isolated due to its
great fragility and it was immediately used to prepare
compound 20. 13C NMR (CDCl3): δ 49.7 (C2), 120.1
5-Diphenylthiophosphinoyl-6-thioxo-6-phenyl-
5,6a,11-triaza-6-phospha-benzo[a]fluorene (20)
3
(C4), 123.8 (C5), 124.1 (C6), 111.1 (d, JPC 6.9 Hz,
This compound was prepared by adding 12 mg (0.38
mmol) of sulfur to a toluene solution of 200 mg (0.38
mmol) of 18 prepared freshly. After heating at re-
flux for 1 h, the reaction mixture was filtered and
the solvent evaporated in vacuum to afford 198 mg
(93%) of a yellow solid. mp 130–134◦C. Compound
20 was also obtained reacting compound 11 with an
excess of sulfur for 1 h in refluxing toluene. 13C NMR
(CDCl3): δ 150.6 (C2), 120.3 (C4), (C5), (C6), 114.2
2
C7), 136.8 (d, JPC 19.4 Hz, C8), 144.3 (C9), 123.0
2
(C10), 136.2 (dd, JPC 15.8 and 5.7 Hz, C11), 125.1
(d, 3 JPC 4.2 Hz, C12), 130.3 (C13), 125.4 (C14), 127.5
4
(C15), 138.0 (Ci), 132.6 (d, JPC 2.7 Hz, Co), 132.1
4
(d, JPC 2.7 Hz, Co), 128.9 (Cm), 128.5 (Cm), 129.9
(Cp) (P Ph), 133.8 (d, 1 JPC 6.0 Hz, Ci), 132.8 (d, 2 JPC
10.6 Hz, Co), 132.4 (dd, 2 JPC 11.0 and 4 JPC 3.3 Hz, Co),
128.7 (d, 3 JPC 3.5 Hz, Cm), 128.7 (d, 3 JPC 4.3 Hz, Cm),
1
129.5 (Cp), 129.3 (Cp) (P Ph2). H NMR (CDCl3): δ
2
3
(C7), 136.6 (d, JPC 5.7, C8), 144.6 (d, JPC 11.1 Hz,
C9), 124.8 (C10), (d, 2 JPC 2.9 Hz, C11), 128.0 (dd, 3 JPC
5.4 and 4.5 Hz, C12), 130.1 (C13), 127.0 (C14), 127.5
(C15), 134.3 (d, 1 JPC 42.3 Hz, Ci), 132.1 (dd, 2 JPC 12.2
and 4 JPC 2.8 Hz, Co), 128.9 (d, 3 JPC 15.8 Hz, Cm), 131.8
(Cp) (P Ph), 135.8 (d, 1 JPC 12.2 Hz, Ci), 132.6 (d, 2 JPC
7.98–8.05 (m, H4), 7.44 (dd, JHH 6.41 and 6.70 Hz,
H5), 7.30–7.42 (m, H6, H7), 7.65 (d, JHH 7.94 Hz,
H12), 6.95 (dd, JHH 7.50 and 7.97 Hz, H13), 7.03 (dd,
JHH 7.44 and 7.60 Hz, H14), 8.22 (d, JHH 7.47 Hz,
H15), 7.50–7.54 (m, Ho), 7.30–7.42 (m, Ho, Hm),
7.18–7.28 (m, Hm), 7.08–7.14 (m, Hp) (P Ph), 7.98–
8.05 (m, Ho), 7.75–7.82 (m, Ho), 7.30–7.42 (m, Hm),
7.08–7.14 (m, Hm, Hp, Hp) (P Ph2). MS: m/z (%):
531.20 (14) [M]+, 392.20 (35), 391.20 (100), 347.20
(12), 314.25 (17), 238.25 (10), 217.25 (43), 139.15
(14).
2
10.7 Hz, Co), 131.7 (d, JPC 11.5 Hz, Co), 128.5 (d,
3
3 JPC 8.4 Hz, Cm), 128.3 (d, JPC 8.1 Hz, Cm), 129.3
(Cp), 129.2 (Cp) (PPh2). 1H NMR (CDCl3): δ 7.99 (d,
JHH 8.34 Hz, H4), 7.48 (dd, JHH 8.16 and 7.38 Hz,
H5), 7.39 (dd, JHH 7.32 and 8.18 Hz, H6), 8.33 (d,
JHH 8.07 Hz, H7), 7.00 (d, JHH 8.30 Hz, H12), 6.78
(dd, JHH 7.27 and 7.42 Hz, H13), 7.05 (dd, JHH 7.35
and 7.90 Hz, H14), 8.15 (d, JHH 7.66 Hz, H15), 7.16–
7.36 [m, H(o), H(m), H(p)] (P Ph), 7.87–7.94 [m,
H(o)], 7.16–7.36 [m, H(m), H(p)] (P Ph2). MS: m/z
(%): 563.20 (22) [M]+, 454.15 (11), 423.20 (7), 391.20
(6), 347.20 (16), 314.20 (8), 218.20 (17), 217.20 (100),
139.15 (22).
5-Diphenylselenophosphinoyl-6-phenyl-5,6a,11-
triaza-6-phospha-benzo[a]fluorene (19)
It was prepared using the same procedure as for 18
from 480 mg (0.96 mmol) of 11 and 76 mg (0.96
mmol) of selenium. The reaction was quantitative.
Compound 19 was not isolated. 13C NMR (CDCl3): δ

Phosphorus Heterocycles from 2-(2-Aminophenyl)-1H-benzimidazole 331
76, 140859f); (c) Bell, S. C. US Patent 3 505 333, 1970;
American Home Products Corp. (Chem Abstr 1970,
73, 25507r).
Compounds 21–24
They were prepared following the same procedure as
described for 20, using 256 mg (0.44 mmol) of 19 and
45 mg (0.57 mmol) of selenium. 31P NMR spectrum
showed a mixture of the compounds 21 (30%), 22
(50%), and 23 (15%).
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Synth Commun 1999, 29, 2617.
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Spirophosphoranes (24)
To a CDCl3 solution of 40 mg (0.14 mmol) of 2 in
a NMR tube was added 31 mg (0.14 mmol) of 3,5-
di-tert-butyl-1,2-benzoquinone at rt. The phospho-
rane 24 was formed quantitatively after stirring for
30 min at rt, according to 31P NMR spectrum and it
was not isolated. 13C NMR (CDCl3): δ Major isomer
151.8 (C2), 119.2 (C4), 122.6 (C5), 122.5 (C6), 115.1
(C7), 136.8 (d, 2 JPC 2.0 Hz, C8), 144.1 (C9), 140.7 (d,
2 JPC 3.0 Hz, C11), 117.8 (d, 3 JPC 14.9 Hz, C12), 130.8
(C13), 123.0 (C14), 126.7 (C15), 142.7 (C16), 138.7
(C17), 106.5 (d, 3 JPC 17.4 Hz, C18), 145.6 (C19), 114.2
3
(C20), 132.1 (d, JPC 9.2 Hz, C21), 35.0 (C22), 31.8
2
(C23), 34.6 (C24), 29.9 (C25), 40.2 (d, JPC 7.4 Hz,
N-CH3); minor isomer 151.6 (C2), 118.9 (C4), 122.3
(C5), 122.3 (C6), 115.4 (C7), 136.4 (d, 2 JPC 2.3 Hz, C8),
2
144.3 (C9), 138.1 (d, JPC 2.3 Hz, C11), 116.8 (C12),
130.8 (C13), 123.0 (C14), 126.6 (C15), 142.4 (d, JPC
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Heteroatom Chem 2004, 15(4), 307.
2
3.0 Hz, C16), 139.0 (C17), 105.1 (d, 3 JPC 11.9 Hz, C18),
145.3 (d, 4 JPC 3.5 Hz, C19), 114.4 (C20), 134.0 (d, 3 JPC
14.1 Hz, C21), 34.7 (C22), 31.8 (C23), 34.3 (C24), 30.1
(C25), 40.2 (d, 2 JPC 7.4 Hz, N-CH3). 1H NMR (CDCl3):
δ major isomer 7.86 (d, JHH 7.61 Hz, H4), 7.27–7.38
(m, H5, H6, H13), 7.68 (d, JHH 8.48 Hz, H7), 6.83–7.00
(m, H12, H18, H20), 7.14 (t, JHH 7.71 Hz, H14), 8.47
(d, JHH 7.82 Hz, H15), 1.29 (s, H23), 1.52 (s, H25),
2.48 (d, 3 JPH 12.75 Hz, N-CH3), 5.84 (d, 2 JPH 4.52 Hz,
N H); minor isomer 7.85 (d, JHH 7.28 Hz, H4), 7.27–
7.38 (m, H5, H13), 7.22 (dd, JHH 8.24 and 7.94 Hz,
H6), 7.64 (d, JHH 8.21 Hz, H7), 6.83–7.00 (m, H12,
H18, H20), 7.14 (t, JHH 7.71 Hz, H14), 8.47 (d, JHH
7.82 Hz, H15), 1.35 (s, H23), 1.16 (s, H25), 2.50 (d,
3 JPH 12.06 Hz, N CH3), 6.13 (d, 2 JPH 4.74 Hz, N H).
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