Synthesis and structural investigation of N-acyl selenophosphoramides

Article abstract of DOI:10.1039/b907641g

2-Amino-2-seleno-5,5-dimethyl-1,3,2-dioxaphosphorinane reacts with acyl chlorides (4-chlorobenzoyl chloride or pivaloyl chloride) yielding the respective N-acyl selenophosphoramides. These derivatives do not isomerise to the related selenocarbonyl imides.

Full text of DOI:10.1039/b907641g

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PAPER
www.rsc.org/obc | Organic & Biomolecular Chemistry
Synthesis and structural investigation of N-acyl selenophosphoramides†
Grzegorz Cholewinski,a Jaroslaw Chojnacki,b Jerzy Pikiesb and Janusz Rachon*a
Received 16th April 2009, Accepted 8th July 2009
First published as an Advance Article on the web 7th August 2009
DOI: 10.1039/b907641g
2-Amino-2-seleno-5,5-dimethyl-1,3,2-dioxaphosphorinane reacts with acyl chlorides (4-chlorobenzoyl
chloride or pivaloyl chloride) yielding the respective N-acyl selenophosphoramides. These derivatives
do not isomerise to the related selenocarbonyl imides. X-ray study of N-(4-chlorobenzoyl)-2-amino-
2-seleno-5,5-dimethyl-1,3,2-dioxaphosphorinane indicates that the selenium atom is placed in the
equatorial position. The next compound studied, N-pivaloyl-2-amino-2-seleno-5,5-dimethyl-1,3,2-
dioxaphosphorinane, crystallises with both axial/equatorial conformers present in the asymmetric unit.
Finally, 2-amino-2-seleno-5,5-dimethyl-1,3,2-dioxaphosphorinane is present in the solid state in the
form with the selenium atom in the axial position. The results are presented together with X-ray
structures of previously synthesised and described cyclic O-acyl monoselenophosphates.
>P(Se)O- with acyl chlorides. Some of these compounds isomerise
to Se-acyl derivatives 7 (Scheme 1). All the collected experimental
Introduction
data indicate that this process has a radical mechanism.7
In this paper we present a synthesis of N-acyl selenophospho-
ramides 8 together with their X-ray structures, and we discuss
their tendency to isomerise. The isomerisation of imides 8 to 9
(Scheme 2) could give selenoacylating agents, analogous to sulfur
derivatives 1 and 4. The X-ray structures of 8 were compared with
those obtained for O-acyl monoselenophosphates 6.
Selenium compounds play an important role in biological pro-
cesses, and their synthesis has been intensively studied.1 The sulfur
analogues of acyl selenophosphates S-acyl dithiophosphates 12,3
and N-acyl thiophosphoramides 44–6 are not stable and isomerise
to the respective thiocarbonyl derivatives 2, 3 and 5 (Scheme 1).
As a result, they can be used as an efficient and chemoselective
thioacylating agents. The influence of substituents R1and R2 at the
phosphorus atom, R3 at the acyl carbon and R4 at the nitrogen
atom on isomerisation was investigated, but the mechanism of
this process has not been elucidated so far. It was established,
however, that the presence of alkoxyl groups R1, R2 and an alkyl
or aryl group R4 is necessary for isomerisation.2,6
Scheme 2
Results and discussion
For our investigations we chose derivatives of 2-seleno-5,5-
dimethyl-1,3,2-dioxaphosphorinane. These turned out to be stable
and crystalline,2 as is crucial for X-ray studies. The related S-acyl
dithiophosphates 1 and O-acyl monoselenophosphates 6 with the
same R1 and R2 groups are known to have a high tendency to
isomerise.2,7
N-acyl selenophosphoramides 8a and 8b were prepared via
reaction of selenophosphoric acid amide 11a with acyl chlorides
12a,b (Scheme 3).
Scheme 1
The starting material for selenophosphoric acid amides was
2-chloro-5,5-dimethyl-1,3,2-dioxaphosphorinane 10.8 2-Amino-2-
seleno-5,5-dimethyl-1,3,2-dioxaphosphorinane 11a was obtained
by addition of 10 to liquid ammonia followed by selenization.
In the case of 2-phenylamino-2-seleno-5,5-dimethyl-1,3,2-
dioxaphosphorinane 11b, 10 was treated with aniline accord-
ing to the procedure described by Stec and Zielinska et al.9
2-Methylamino-2-seleno-5,5-dimethyl-1,3,2-dioxaphosphorinane
11c was synthesized by the reaction of 2-chloro-2-seleno-5,5-
dimethyl-1,3,2-dioxaphosphorinane (obtained by heating 10 with
selenium in toluene)10 with a methanolic solution of methylamine.
Recently, we synthesized O-acyl monoselephosphates 6 in
the reaction of the respective monoselenophosphoric acid salts
aDepartment of Organic Chemistry, Chemical Faculty, Gdansk University
of Technology, G. Narutowicza 11/12, 80-233, Gdansk
bDepartment of Inorganic Chemistry, Chemical Faculty, Gdansk University
of Technology, G. Narutowicza 11/12, 80-233, Gdansk
† Electronic supplementary information (ESI) available: X-ray data,
Figs. S1–S3, and NMR spectra. CCDC reference numbers CCDC 717028
(6c), 717029 (6d), 717030 (6e), 717031 (8a), 717032 (8b) and 717033 (11a).
For ESI and crystallographic data in CIF or other electronic format see
DOI: 10.1039/b907641g
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Scheme 3
Subsequently, selenophosphoric acid amides 11a–c were met-
allated with sodium hydride in THF and then treated with acyl
chlorides 12a,b. These synthetic routes are presented in Scheme 3.
N-Acyl selenophosphoramides 8a and 8b were isolated and
fully characterized. Attempts to synthesize 8c–f via reactions of
selenophosphoric acid amides 11b and 11c with acyl chlorides
12a,b were not successful. Moreover, no isomerisation products
9 (according to Scheme 2) were observed. These results clearly
indicate that the presence of a hydrogen atom at nitrogen
is crucial for the stability and successful synthesis of N-acyl
monoselenophosphates.
selenophosphoramide 11a are given in Table S1†. The ORTEP12
views of 6c, 8b and 11a are shown in Figs. 1–3, and views of 6d, 6e
and 8a, Figs. S1–3, respectively.
In the next stage of our studies, the stability of N-acyl
selenophosphoramides 8a,b was examined. The samples of 8a and
8b were heated in three different solvents (chloroform, benzene,
toluene) and the progress of the reactions monitored by 31P NMR
spectroscopy. No isomerisation to 9 (according to Scheme 2) was
observed; however, partial decomposition of the compounds in
boiling toluene occurred.
Fig. 1 The molecular structure of O-(p-chlorobenzoyl)-2-oxo-2-seleno-
5,5-dimethyl-1,3,2-dioxaphosphorinane 6c◦. Displacement ellipsoids 50%.
˚
Selected bond lengths (A) and angles ( ): O1–P1 1.5693(13), O2–P1
The only similarity of N-acyl selenophosphoramides 8 to their
sulfur analogues 4, investigated by DeBruin,4–6 was the stability of
compounds with R4 = H. To explain this, DeBruin suggested the
formation of a tautomer 13, which should be fairly stable due to
an intramolecular hydrogen bond (Scheme 4) and which hinders
8 from forming a bicyclic intermediate 14 (postulated during
isomerisation of 4 to 5, and observed for R4 = alkyl or aryl).4 The
selenium analogue of 14 could be less stable because of weaker
bonds and stronger angle distortions11 and thus decomposition
instead of isomerisation was observed.
1.5747(13), C6–C7 1.478(3), O1–P1–O3 104.93(7), O2–P1–O3 99.12(7),
P1–O3–C6 122.19(11), Se1–P1–O3–C6 -65.46(13).
Fig. 2 The molecular structure of N-pivaloyl-2-amino-2-seleno-5,5-
dimethyl-1,3,2-dioxaphosphorinane 8b. Displacement ellipsoids 50%.
Scheme 4
◦
˚
Selected bond lengths (A) and angles ( ): 8b-Se-a O1–P1 1.5889(18),
O2–P1 1.5898(17), C6–C7 1.528(3), O1–P1–N1 103.40(11), O2–P1–N1
105.13(10), P1–N1–C6 125.50(19), P1–N1–H1 114(2), C6–P1–H1
120(2), Se1–P1–N1–C6 173.37(18). 8b-Se-e O11–P2 1.5745(18), O12–P2
1.5760(18), C16–C17 1.520(6), O11–P2–N2 106.76(11), O12–P2–N2
100.32(10), P2–N2–C16 122.95(13), P2–N2–H2 113(2), C16–N2–H2
120(2), Se2–P2–N2–C16 64.3(2).
However, our X-ray investigations of N-acyl selenophospho-
ramides 8a and 8b excluded formation of tautomers like 13 in
the solid state. Thus, the explanation of the stability of 8 and
related compounds in terms of the intramolecular stabilization
of tautomer 134 seems not to be acceptable. The basic crystal
data, description of the diffraction experiment, and details of the
structure refinement for the stable acyl monoselenophosphates
6c, 6d and 6e, the N-acyl selenophosphoramides 8a and 8b and
The most diagnostic spectral parameters of these compounds
1
are chemical shifts d (ppm) and coupling constants JP–Se
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Table 1 31P NMR and X-ray structural analysis for the stable and crystalline anhydrides 6a–e and imides 8 and 11a
31P NMR: d
P1–O3 or
P1–N1 (A)
O3–C6 or
˚
R1
R2
R3
(ppm)/1JP–Se (Hz)
P1 Se1 (A)
N1–C6 (A)
C
O (A)
˚
˚
˚
=
=
6a
Ph
Ph
Ph
Ph
p-ClPh
t-Bu
p-ClPh
p-MeOPh
p-NO2Ph
p-ClPh
t-Bu
81.2/859
78.6/852
51.9/1056
52.4/1057
51.4/1064
56.4/941
58.4/932
58.4/932
71.0/894
2.0774(11)
2.0769(11)
2.0469(5)
2.0517(7)
2.0433(11)
2.0492(10)
2.0647(8)
2.0655(7)
2.0948(6)
1.653(3)
1.650(3)
1.6352(13)
1.628(2)
1.650(3)
1.674(3)
1.688(2)
1.651(2)
1.604(2)
1.380(5)
1.386(4)
1.382(2)
1.388(3)
1.369(5)
1.373(4)
1.382(3)
1.396(3)
—
1.197(5)
1.200(4)
1.200(2)
1.194(3)
1.190(5)
1.207(4)
1.218(3)
1.214(3)
—
6b
6c
6d
6e
8a
8b-Se-e
8b-Se-a
11a
t-Bu
—
electron-withdrawing substituents shorten the P1–Se1 and C6–O3
bonds and lengthen the P1–O3 bond.
In the next series of X-ray measurements we attempted to
characterise the structures of imides 8a and 8b. Similarly to
anhydrides 6c–6e, the selenium in 8a was found to be in the
equatorial position. Imide 8b crystallized with two molecules in
the asymmetric unit, one with the selenium atom in the equatorial
position (8b-Se-e) and one with Se in the axial (8b-Se-a) position.
The preference for the axial position in the chair conformations
of six-membered rings is higher for more electronegative groups,17
and increases if the anomeric substituent X (N, O or Se) has
electron-withdrawing character, due to lowering the energy of the
exocyclic s*(P–X) orbital.18 Hence, we have competition between
Se and the other group to occupy the axial position.
Fig.
3 The molecular structure of 2-amino-2-seleno-5,5-dimethyl-
1,3,2-dioxaphosphorinane 11a. Displacement ellipsoids 50%. Selected
◦
˚
Acyloxy groups -O–CO–R show a high tendency to prefer
axial positions, so in 6c–6e selenium atoms adopt the equatorial
position exclusively. The amido groups –NH–CO–R have a lower
preference for the axial positions.
bond lengths (A) and angles ( ): O1–P1 1.5855(16), O2–P1 1.5909(15),
N1–H1a 0.81(3), N2–H1b 0.81(3), O1–P1–N1 107.27(11), O2–P1–N1
102.97(11), P1–N1–H1a 118(2), P1–N1–H1b 117(2), H1a–N1–H1b
118(2), Se1–P1–N1–H1a -180(2), Se1–P1–N1–H1b 31(2).
The imide 8b bears a bulky, electron-donating group in its acyl
part. Thus the tendency to occupy the axial position is lower for
8b than for 8a, which results in an equilibrium between 8b-Se-e
and 8b-Se-a. It is noteworthy that imide 8b had a sufficiently
(31P NMR). The NMR measurements for mixed anhydrides 6 were
reported previously.7 In this paper we compare them with those
received for mixed imides 8. The selected parameters of X-ray
results for 6c–6e, 8a, 8b and 11a are presented in Table 1 together
with data of acyclic compounds 6a13 and 6b14 and compared with
NMR-data.
=
weakened axial preference of amido group to have an axial P Se
bond, despite the presence of the electron-withdrawing carbonyl
group connected to the bridging NH unit.
The geometry around the N1 atom in 8a is not strictly planar,
the sum of angles being 357(3)◦. The torsion angle C6–N1–P1–
Se1 is 63.4(3)◦. The conformation around P–N bond puts the lone
Table 1 shows data for anhydrides 6c–6e known to crystallise as
anomers with the large selenium atom in the equatorial position.
This is in accordance with an increasing tendency to adopt an axial
position with the electron-withdrawing character of an anomeric
substituent,15 here the P1–O3 bond. The R1, R2 substituents at
pair of the almost planar N1 atom19 antiperiplanar to P1 Se1 and
=
antiperiplanar to the P1–O1 bonds, and thus the reverse anomeric
=
interactions nN→s*(P1 Se1) and nN→s*(P1–O1) are possible.
1
phosphorous have significant impact on d, JP–Se, and also the
In the literature are reported structural evaluations concern-
=
P Se bond length in the case of mixed anhydrides 6a–6e. The
ing
5,5-dimethyl-2-(phenylamino)-1,3,2-dioxaphosphorinane-
5,5-dimethyl-2-(o-nitrophenyl)amino-1,3,2-dioxa-
acyclic compounds 6a and 6b with R1 = R2 = Ph indicate longer
P1–Se1 distances and smaller 1JP1–Se1 coupling constants than the
cyclic ones 6c, 6d and 6e.
2-selenide,20
phosphorinane-2-selenide21 and 2-((3,5-dichlorophenyl)amino)-
5,5-dimethyl-1,3,2-dioxaphosphorinane-2-selenide,22 in which the
nitrogen atom bears an electron-withdrawing group. All these
compounds display in the solid state axial P–N bonds and Se in
the equatorial position.
These differences are not due to the cyclic arrangement of
R1 and R2 in 6c–6e but due to the alkoxyl character of these
=
groups. Triphenoxyphosphine selenide has a P Se bond length
16
˚
=
of 2.052 A, very near to the P Se distances in 6c, 6d and 6e.
There are small but distinct differences in bond distances in
8b-Se-a and 8b-Se-e. Isomer 8b-Se-a with axial Se has slightly
The substituents in the phenyl ring of the acyl part in 6c, 6d and
6e exert small, but distinct influences on the bond lengths. The
=
=
shorter P–N and C O bonds and slightly longer P Se and
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Table 2 Results of theoretical calculations, and comparison of energies
for equatorial and axial conformers of 8b. All optimised structures were
checked that they represented true minima by calculating the IR spectra,
in which no imaginary frequencies were presenta
Interestingly, the torsion angle Se–P–N–C in both theoretically
optimised structures 8b was very similar (ca. 180◦). Calculation of
vibrational spectrum for both 8b conformers shows that the two
least energetically demanding vibration modes can be described as
rotations of the terminal tert-butyl group and deformation of the
above-mentioned Se–P–N–C torsion. This helps us to rationalise
the facts that one of the tert-butyl groups is disordered and that
the torsion is altered in the solid state (compared to the isolated
molecule).
Method
b3lyp/3-21G*
MP2/3-21G*
HF/3-21G*
8b-Se-e (a.u.)
8b-Se-a (a.u.)
DE(e–a) (a.u.)
DE(e–a)
-3400.16073652 -3395.21504485
-3400.16132766 -3395.21870627
-3393.6072951
-3393.6040368
-0.00325
0.00059114
0.37
0.00366142
2.30
-2.04
The natural bond orbitals (NBO) analysis30 of the optimised
structures suggests that the most (energetically) important donor–
(kcal/mol)
a Note that the two molecules of 8b are additionally involved in intermolec-
ular hydrogen bonding of the N–H ◊ ◊ ◊ O type, which can also facilitate
deformation of torsion angles.
=
acceptor intramolecular interactions are lpN→p*(C O), then
lpSe→s*(P–N), lpSe→s*(P–O), lpO→s*(P–N) and lpO→s*(Se–
P). The program interprets the P–Se system as a single bond with
separated charges and three lone pairs on the selenium atom. Two
of the pairs have mainly p-character, while the last pair has a big
s-function contribution, and is inactive in intramolecular donor–
acceptor interactions.
C–N bonds than 8b-Se-e. There are, however, major differences in
conformations around the P–N bonds and geometries around the
N atoms.
The structural features of 8b-Se-e are similar to those of
8a. The P2 atom and the N2–H2 and C16–O13 bonds are
In amide 11a selenium atoms adopt the axial position, ex-
clusively. This compound has the shortest P–N and the longest
=
=
almost in one plane, but the P2 Se2 bond is out of plane.
P Se distances of all derivatives 6 and 8 under investigation
(and the smallest JP–Se value as well). The geometry around
The torsion angle Se2–P2–N2–C16 is 64.3(2)◦, and the sum of
1
angles around N2 is 356(2)◦. The lone electron pair of N2 can be
N atom is not planar, and the sum of angles around N1 is
353(2)◦; the lone pair at N1 cannot act as a donor to s*(P1–Se1).
The solid-state structure of the related 5,5-dimethyl-2-ethylamino-
1,3,2-dioxaphosphorinane-2-selenide27 has similar features.
=
mixed with s*(P2 O11) and with s*(P2–Se2) in reverse anomeric
interactions, although additional NBO calculations (see below)
indicate that the energetic stabilization due to this interaction is of
minor importance.
In 8b-Se-a the geometry around N1 is planar, while the sum
Solid-state intermolecular interactions
◦
=
of angles around N2 is 360(2) . The P1 Se1, N1–H1 and C6–O3
The packing of molecules 6c–e and 8a is reinforced by p–p stack-
ing interactions between phenyl rings. The centroid-to-centroid
distances for the neighbouring rings are given in Table 3. This
interaction is the strongest for nitrophenyl-substituted derivative
6e.
A relatively strong N–H ◊ ◊ ◊ O hydrogen bond is found in
structure 8b between the two axial/equatorial conformers. Inter-
estingly, both hydrogen atoms in 11a are directed towards the
selenium atoms, which could be an indication of a weak hydrogen
bond of the N–H ◊ ◊ ◊ Se type. Due to the partial negative charge of
the Se atom, its acceptor properties should be enhanced.
bonds are almost in one plane, and the torsion angle Se1–P1–N1–
C6 is 173.37(18)◦. The lone pair of the planar N1 atom19 cannot
=
be antiperiplanar to the P1 Se1 bond, and thus it cannot act
=
as a donor in anomeric interaction nN→s*(P Se). It is almost
antiperiplanar to the P1–O1 and to P1–O2 bonds and can act in
anomeric interactions nN→s*(P1–O1) and nN→s*(P1–O2). The
lone pairs of endocyclic O1 and O2 atoms are antiperiplanar to
=
the P1 Se1 bond and can act as donors in anomeric interactions
=
nO→s*(P Se).
The selenium atom can adopt the equatorial posi-
tion in trans-2-t-butylamino-4-methyl-1,3,2-dioxaphosphorinane-
2-selenide,23 or the axial position in cis-2-t-butylamino-4-methyl-
1,3,2-dioxaphosphorinane-2-selenide24 and cis-2-t-butylamino-
4,4,6-trimethyl-1,3,2-dioxaphosphorinane-2-selenide.25 It is worth
pointing out that the imido compound 8b and amido
compounds23,24,25 with a t-butyl group show similar axial–
equatorial preferences.
Conclusions
The presence of the hydrogen at the nitrogen bridge atom is
crucial for stability of N-acyl selenophosphoramides 8. The
substituents in the acyl part and the type of the bridge atom
determine the conformation of the six-membered cyclic derivatives
of selenophosphoric acid 6c–e and 8a,b. The amido group
-NH–CO–C6H5–4-Cl in imide 8a occupies the axial position, as
for the acyloxy groups -O–CO–R in anhydrides 6c–e. In contrast,
N-pivaloyl selenophosphoramide 8b gave two chair conformations
8b-Se-a and 8b-Se-e due to a lower electron-withdrawing effect
In order to get a deeper insight into relative stability of axial and
equatorial conformers of 8b, additional theoretical investigations
were carried out. The results of the optimisations (see Table 2)
indicate that the axial conformer is energetically more stable,
although a method including electron correlation (more advanced
than simple HF) should be used to reach this conclusion.
The difference in energy between the two forms is not crucial
for excluding one specific conformer from crystalisation. One
additional explanation for co-crystallisation can be hydrogen
bond formation between the two molecules (see Fig. 2). In all
investigated compounds (6c, 6d, 6e, 8a, 8b and 11a) predictions
based on the anomeric effect are in accordance with X-ray
structure determinations.
Table 3 Data concerning p–p stacking interactions between phenyl rings
in 6c–e and 8a
Compound
6c
6d
6e
8a
Centroid-to-centroid
distance (A)
4.626
4.026
3.717
4.223
˚
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of the acyl part and a higher energy of the antibonding P–N
orbital. These results clearly indicate a correlation between
anomeric interactions nO→s*(P–X) (where X = O or NH) and
the conformer distribution for 6c–e and 8a,b. This relationship is
extended to derivatives without an acyl group at the N atom, viz.
selenophosphoramide 11a, in which selenium is found only in the
axial position despite its size.
2-Amino-2-seleno-5,5-dimethyl-1,3,2-dioxaphosphorinane 11a.
2-Chloro-5,5-dimethyl-1,3,2-dioxaphosphorinane 108 (0.05 mol)
was added portionwise to liquid ammonia (100–125 mL) at -33 ◦C
with stirring. After vigorous reaction, selenium powder (0.05 mol)
was added and stirring continued for 6 h. Then, cooling bath
(acetone + CO2) was taken away and ammonia evaporated with
stirring. THF (50 mL) was poured onto the remaining material and
the reaction mixture was stirred for 12 h. The solids were filtered off
and washed with THF. The solvent was removed in vacuum, and
the crude product purified by column chromatography (eluent:
petroleum ether–dichloromethane) to give 11a (6.87 g, 60%). The
product was crystallized (petroleum ether–dichloromethane) for
crystallography purposes.
Experimental
O-Acyl monoselenophosphates 6 were obtained by the reaction of
the respective monoselenophosphoric acid salt with acyl chloride.7
Preparation of mixed imides 8 was carried out under argon
in THF dried over potassium with benzophenone as indicator.
Chromatography was carried out on Silica Gel 60 (0.05–0.2mm)
Mp 69–71 ◦C; dP (acetone-d6) 71.0 (1JPSe 894); dH (acetone-
2
d6): 0.86 (3Ha, s, CH3), 1.20 (3He, s, CH3), 3.72 (2Ha, dd, JHa–He
R
3
2
3
Macherey Nagelꢀ. NMR was performed on a Varian Gemini
10.5, JHa–P 26.4, CH2O), 4.26 (2He, dd, JHe–Ha 10.5, JHe–P 5.1,
CH2O), 5.24 (2H, s, NH2); dC (acetone-d6) 20.08, 21.90, 32.33
500 MHz, J values are given in Hz. IR spectra were acquired
on a Bruker IFS66 instrument. Mass spectra were acquired on a
MASPEC II system [II32/99D9] in the EI mode if not otherwise
specified.
(d, J 5.0), 78.60 (d, J 5.0); nmax/cm-1 518 (P Se); m/z 228.9779
=
(C5H12NO2P80Se requires 228.9771).
2-Phenylamino-2-seleno-5,5-dimethyl-1,3,2-dioxaphosphorinane
11b. This was prepared from 2-chloro-5,5-dimethyl-1,3,2-
dioxaphosphorinane 108 according to the procedure described by
Stec and Zielinska et al.9
X-ray structural analysis
Experimental diffraction data were collected on KM4CCD kappa-
geometry diffractometer, equipped with a Sapphire2 CCD detec-
tor. An enhanced X-ray Mo Ka radiation source with a graphite
monochromator was used. The preliminary calculations were
made using CrysAlis software package.28 Structure solution and
final refinement were carried out using the SHELX-97 program
package.29
Structures were solved by direct methods and all of the non-
hydrogen atoms were refined with anisotropic thermal parameters
by full-matrix least squares procedure based on F2. All C–H
hydrogen atoms were refined using isotropic model with Uiso(H)
values fixed to be 1.5 times Ueq of C atoms for CH3 or 1.2 times Ueq
for CH2 and CH groups. All N–H hydrogen atoms were refined
freely without restraints. Analytical absorption corrections based
on a multi-faceted model of crystal shape were applied using
CrysAlis171 program.28
Mp 174–175 ◦C (Lit.,9 mp 175–176 ◦C); dP (CDCl3) 65.9 (1JPSe
909) (Lit.,9 dP (CDCl3) 62); dH(CDCl3) 0.92 (3Ha, s, CH3), 1.11
2
3
(3He, s, CH3), 3.83 (2Ha, dd, JHa–He 11.0, JHa–P 25.1, CH2O),
4.44 (2He, dd, 2JHe–Ha 10.7, 3JHe–P 5.8, CH2O), 5.6 (1Hamide, s), 7.15
(1Harom, m), 7.23 (2Harom, m), 7.32 (2Harom, t, 3J 7.8).
2-Methyloamino-2-seleno-5,5-dimethyl-1,3,2-dioxaphosphori-
nane 11c. To
a
solution of 2-chloro-5,5-dimethyl-1,3,2-
dioxaphosphorinane 108 (17.8 mmol) was added triethylamine
(17.8 mmol). Then, to the reaction mixture was added dropwise
methylamine (9.0 mL, 2 M in methanol) at room temperature
with stirring. After 2 h the solvent was evaporated and the crude
product purified by column chromatography (eluent: CH2Cl2–
petroleum ether 1:2) to give 11c (15.17 g, 53%).
Mp 79–81 ◦C; dP (CDCl3) 71.2 (1JP–Se 893); dH(CDCl3) 0.89
(3Ha, s, CH3), 1.28 (3He, s, CH3), 2.78 (3H, d, 3JH–P 13.2, NCH3),
3.75 (2Ha, dd, 2JHa–He 11.2, 3JHa–P 25.9, CH2O), 4.41 (2He, dd, 2JHe–Ha
The structure of 8b contains one tert-butyl group (C17–C20)
in molecule 8b-Se-e disordered over two positions occupied with
probabilities 0.778(6)/0.222(6).
3
10.7, JHe–P 3.4, CH2O); m/z 243.9998 (C6H14NO2P80Se requires
244,0000) in ESI mode.
Theoretical quantum-chemical calculations
Selenophosphoryl carbonyl imides 8a and 8b. To a suspen-
sion of sodium hydride (10–12 mmol) in 15 mL of THF was
added 2-amino-2-seleno-5,5-dimethyl-1,3,2-dioxaphosphorinane
11a (5 mmol) at 0 ◦C. After all hydrogen had evolved, the
respective acyl chloride 12a,b (5 mmol) was added portionwise
and stirring was continued at room temperature for 1 h. Then, the
reaction mixture was filtered, evaporated under reduced pressure,
dissolved in chloroform (100 mL) and washed with 1 M NH4Cl.
Subsequently, the organic layer was separated, dried over MgSO4,
filtered and evaporated. The crude product was purified by column
chromatography (eluent: petroleum ether–dichloromethane). The
product was crystallized (petroleum ether–dichloromethane) for
crystallography purposes.
Calculations were carried out at the Academic Computer Center
in Gdan´sk (TASK). The Gaussian 03 program package, including
the NBO module,30 was used for the entire investigation. Both
conformers of 8b were cut out of the X-ray structure and their
geometry optimised using the Gaussian 03 package.26 Density
functional theory with B3LYP functional and Møller–Plesset
second-order perturbation theory were selected as the minimi-
sation methods.
Synthesis
2-Chloro-2-seleno-5,5-dimethyl-1,3,2-dioxaphosphorinane. This
was prepared from 2-chloro-5,5-dimethyl-1,3,2-dioxaphos-
phorinane 108 according to the procedure described by Michalska
et al.10
N-(p-Chlorobenzoyl)-2-amino-2-seleno-5,5-dimethyl-1,3,2-di-
oxaphosphorinane 8a (2.46 g, 67%), mp 163–164 ◦C with decompo-
sition, dP (CDCl3) 56.4 (1JPSe 941); dH(CDCl3) 1.19 (3Ha, s, CH3),
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1.26 (3He, s, CH3), 4.28 (2Ha, dd, 2JHa–He 10.7, 3JHa–P 12.7, CH2O),
8 C. Patoi, L. Ricard and Ph. Savignac, J. Chem. Soc., Perkin Trans. 1,
1990, 1577–1581.
9 K. Lesiak, Z. J. Les´nikowski, W. J. Stec and B. Zielin´ska, J. Pol. Chem.,
2
3
4.38 (2He, dd, JHe–Ha 10.7, JHe–P 14.2, CH2O), 7.46 (2Harom, d,
3JH–H 8.3), 7.59 (1Hamide, d, 2JH–P 17.1); 7.78 (2Harom, d, 3JH–H 8.8);
dC(CDCl3) 22.01; 22.53; 32.89 (d, J 7.6), 79.05 (d, J 8.0), 129.49,
129.58, 130.65 (d, J 7.6), 140.03, 165.25 (d, J 8.0); nmax/cm-1 566
1979, 53, 2041–2050.
10 M. Michalska, I. Orlich-Kre˛zel and J. Michalski, Tetrahedron Lett.,
˙
1978, 34, 2821–2824.
11 C. Paulmier, Selenium Reagents and Intermediates in Organic Synthesis,
Pergamon Press, 1986, p. 6.
80
35
=
=
(P Se), 1653 (C O); m/z 366.9648 (C12H15NO3P Se Cl requires
366.9643).
12 C. K. Johnson, ORTEPII Report, ORNL-5138, Oak Ridge National
N-Pivaloyl-2-amino-2-seleno-5,5-dimethyl-1,3,2-dioxaphospho-
rinane 8b (1.75 g, 56%), mp 119–120.5 ◦C; dP (CDCl3) 58.4 (1JPSe
932); dH(CDCl3) 1.10 (3Ha, s, CH3), 1.22 (9H, s, CH3), 1.24 (3He, s,
CH3), 4.20–4.27 (4H, m), 6.93 (1Hamide, d, 2JH–P 18.1); dC(CDCl3)
22.16, 22.35, 27.34, 32.88 (d, J 7.6), 40.32 (d, J 6.1), 78.70 (d, J
Laboratory, Tennessee, USA, 1976.
13 G. Cholewinski, J. Chojnacki, J. Pikies and J. Rachon, Acta Crystallogr.,
Sect. E: Struct. Rep. Online, 2009, 65, o855.
14 G. Cholewinski, J. Chojnacki, J. Pikies and J. Rachon, Acta Crystallogr.,
Sect. E: Struct. Rep. Online, 2009, 65, o853–o854.
15 E. Juaristi and G. Cuevas, Tetrahedron, 1992, 48, 5019–5087.
16 J. Clade and M. Jansen, Z.Kristallogr.-New Cryst. Struct., 2005, 220,
234–236.
17 D. G. Gorenstein, Chem. Rev., 1987, 87, 1047–1077.
18 W. G. Bentrude, W. N. Setzer, E. Ramli, M. Khan and A. E. Sopchik,
J. Org. Chem., 1991, 56, 6127–6131.
19 D. B. Chesnut, J. Phys. Chem. A, 2000, 104, 7635–7638.
20 T. J. Bartczak, Z. Gałdecki, H. B. Trzez´win´ska and W. M. Wolf, Acta
Crystallogr., Sect. C: Cryst. Struct. Commun., 1983, 39, 731–732.
21 W. M. Wolf and T. J. Bartczak, Acta Crystallogr., Sect. C: Cryst. Struct.
Commun., 1989, 45, 1767–1770.
22 T. J. Bartczak and W. Wolf, Acta Crystallogr., Sect. C: Cryst. Struct.
Commun., 1983, 39, 224–227.
23 T. J. Bartczak, A. Christensen, R. Kinas and W. J. Stec, Cryst. Struct.
Commun., 1976, 5, 21–24.
24 T. J. Bartczak, A. Christensen, R. Kinas and W. J. Stec, Cryst. Struct.
Commun., 1975, 4, 701–704.
7.6); 177.91 (d, J 11.4); nmax/cm-1 536 (P Se), 562; 1688, 1716
(C O); m/z 313.0358 (C10H20NO3P Se requires 313.0346).
=
80
=
Attempted synthesis of N-substituted mixed imides 8c–8f.
To a suspension of sodium hydride (5–6 mmol) in 15 mL
of THF was added 2-phenylamino-2-seleno-5,5-dimethyl-1,3,2-
dioxaphosphorinane 11b (5 mmol) or 2-methylamino-2-seleno-
5,5-dimethyl-1,3,2-dioxaphosphorinane 11c (5 mmol) at 0 ◦C.
After all the hydrogen had evolved, the respective acyl chloride
12a,b (5 mmol) was added portionwise and stirring was continued
at room temperature for 1 h. 31P NMR analysis of the crude
reaction mixtures indicated numerous side-products. There was
no resonance signal for expected product 8c–8f or for the
isomerisation products 9c–9f.
25 R. Kinas, W. J. Stec and C. Kru˝ger, Phosphorus and Sulfur, 1978, 4,
295–298.
26 Gaussian 03, Revision D.01, M. J. Frisch, G. W. Trucks, H. B. Schlegel,
G. E. Scuseria, M. A. Robb, J. R. Cheeseman, J. A. Montgomery, Jr.,
T. Vreven, K. N. Kudin, J. C. Burant, J. M. Millam, S. S. Iyengar, J.
Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega,
G. A. Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R.
Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao,
H. Nakai, M. Klene, X. Li, J. E. Knox, H. P. Hratchian, J. B. Cross,
V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann,
O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, P. Y.
Ayala, K. Morokuma, G. A. Voth, P. Salvador, J. J. Dannenberg, V. G.
Zakrzewski, S. Dapprich, A. D. Daniels, M. C. Strain, O. Farkas,
D. K. Malick, A. D. Rabuck, K. Raghavachari, J. B. Foresman, J. V.
Ortiz, Q. Cui, A. G. Baboul, S. Clifford, J. Cioslowski, B. B. Stefanov,
G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. L. Martin, D. J.
Fox, T. Keith, M. A. Al-Laham, C. Y. Peng, A. Nanayakkara, M.
Challacombe, P. M. W. Gill, B. Johnson, W. Chen, M. W. Wong, C.
Gonzalez and J. A. Pople, Gaussian, Inc., Wallingford, CT, 2004.
27 T. J. Bartczak, Z. Gałdecki, W. M. Wolf, K. Lesiak and W. J. Stec, Acta
Crystallogr., Sect. C: Cryst. Struct. Commun., 1986, 42, 244–246.
28 CrysAlis CCD, CrysAlis RED and associated programs, Oxford Diffrac-
tion Ltd, Abingdon, England, 2006.
Thermodynamic stability of 8a and 8b. A solution of corre-
sponding imide 8a,b (1 mmol) in chloroform (5 mL) was prepared
and monitored by 31P NMR spectroscopy at room temperature.
Both imides were stable when the solutions were refluxed in
chloroform (b.p. 61 ◦C) for 4 h, and no reaction was detected.
Other solvents were also examined (benzene (b.p. 80 ◦C), toluene
(b.p. 111 ◦C)) with a 4 h monitoring time. During heating in
toluene, initial symptoms of decomposition were observed. No
isomerisation was noted in these experiments.
References
1 G. Mugesh, W.-W. du Mont and H. Sies, Chem. Rev., 2001, 101, 2125–
2179.
2 L. Doszczak and J. Rachon, J. Chem. Soc., Perkin Trans. 1, 2002, 1271–
1279.
3 L. Doszczak and J. Rachon, Synthesis, 2002, 1047–1052.
4 K. E. DeBruin and E. E. Boros, Tetrahedron Lett., 1989, 30, 1047–
1050.
5 K. E. DeBruin and E. E. Boros, Phosphorus, Sulfur Silicon Relat. Elem.,
1990, 49/50, 139–142.
29 G. M. Sheldrick, Acta Crystallogr., Sect. A: Found. Crystallogr., 2008,
64, 112–122.
30 NBO Version 3.1: E. D. Glendening, A. E. Read, J. E. Carpenter, F.
Weinhold;, A. E. Reed and F. Weinhold, J. Chem. Phys., 1983, 78,
4066–4073; A. E. Reed and F. Weinhold, J. Chem. Phys., 1985, 83,
1736.
6 K. E. DeBruin and E. E. Boros, J. Org. Chem., 1990, 55, 6091–6098.
7 J. Rachon, G. Cholewinski and D. Witt, Chem. Commun., 2005, 2692–
2694.
4100 | Org. Biomol. Chem., 2009, 7, 4095–4100
This journal is
The Royal Society of Chemistry 2009
©