Solid-state conformation of the 1,3,2-oxazaphospholane ring in 2-dialkylamino-3,4-dimethyl-5-phenyl-1,3,2-oxazaphospholane sulfides

Article abstract of DOI:10.1002/hc.1023

Dialkylamino-3,4-dimethyl-5-phenyl-1,3,2-oxazaphospholane sulfides (where the alkyl is an isopropyl, ethyl or methyl group) was obtained by sulfurization of the respective phospholanes. The structures of these compounds were determined by X-ray crystal structure analysis. Five-membered rings exist in the envelope conformation in the crystalline state. The planar part of the 1,3,2-oxazaphospholane rings undergoes twisting with the enlargement of a substituent. The environment of the Patom has the geometry of a distorted tetrahedron.

Full text of DOI:10.1002/hc.1023

Heteroatom Chemistry
Volume 12, Number 3, 2001
S
olid-State Conformation of the 1,3,2-
Oxazaphospholane Ring in 2-Dialkylamino-3,4-
dimethyl-5-phenyl-1,3,2-oxazaphospholane
Sulfides
1
1
2
Rafal Kruszynski, Tadeusz J. Bartczak, and Piotr Majewski
1
X-Ray Crystallography Laboratory, Institute of General and Ecological Chemistry, Technical
˙
University of Ł o´ d z´ -Politechnika Ł o´ dzka, Zeromskiego 116, 90-924 Ł o´ d z´ , Poland
2
˙
Institute of Organic Chemistry, Technical University of Ł o´ d z´ -Politechnika Ł o´ dzka, Zeromskiego
1
16, 90-924 Ł o´ d z´ , Poland
Received 7 September 2000; revised 29 November 2000
tures composed of 1,3,2-oxazaphospholane rings de-
scribed in the literature [1–4], but only for 71
different structures have three-dimensional param-
eters been determined. Statistically, most preferred
is the envelope conformation with carbon bonded to
nitrogen at the flap (28 structures), the next most
preferred conformation has carbon bonded to oxy-
gen at the flap (19 structures). Moreover, 7 envelope
structures exist with N at the flap, 3 with P at the
flap, but only 1 with O at the flap, and there are only
ABSTRACT: Dialkylamino-3,4-dimethyl-5-phenyl-
1,3,2-oxazaphospholane sulfides (where the alkyl is an
isopropyl, ethyl or methyl group) was obtained by sul-
furization of the respective phospholanes. The struc-
tures of these compounds were determined by X-ray
crystal structure analysis. Five-membered rings exist
in the envelope conformation in the crystalline state.
The planar part of the 1,3,2-oxazaphospholane rings
undergoes twisting with the enlargement of a substit-
uent. The environment of the P atom has the geometry
of a distorted tetrahedron. ᭧ 2001 John Wiley & Sons,
Inc. Heteroatom Chem 12:146–150, 2001
5
planar structures. Eight structures have an ideal
half-chair conformation. The conformation adopted
depends on the substituents both at phosphorus and
at the other atoms of the ring [1]. In this article, we
attempt to present the influence of substituents at
the phosphorus atom on the geometry of 1,3,2-oxa-
zaphospholane rings.
INTRODUCTION
Five-membered rings are highly fluxional and capa-
ble of adopting a range of nonplanar conformations
separated by very small energy barriers in solution
SYNTHESIS
[1]. In the solid state, one single conformation usu-
Homochiral chlorophosphoroamidite [(1R,2S)-O,N-
ephedrine]PCl (2) has been synthesized [4,5] by the
reaction of the trimethylsilyl derivate of (מ)ephed-
rine (1) with phosphorus trichloride. The chloride 2
obtained reacts stereoselectively with trimethyl-
silyldialkylamines to give liquid 2-dialkylamino-
3,4-dimethyl-5-phenyl-1,3,2-oxazaphospholanes (3),
ally exists, depending on the substituents and crystal
packing. Five-membered rings can adopt the enve-
lope or half-chair conformation. There are 91 struc-
Correspondence to: Tadeusz J. Bartczak.
Contract Grant Sponsor: State Committee for Scientific Research.
᭧
2001 John Wiley & Sons, Inc.
1
46

Conformation of 1,3,2-Oxazaphospholane Ring in 2-Dialkylamino-3,4-dimethyl-5-phenyl-1,3,2-oxazaphospholaneSulfides 147
FIGURE 3 The molecular conformation of 4-3 with atom
numbering.
SCHEME 1 Reactions in synthesis.
FIGURE 4 Torsion angles (Њ) and asymmetry parameters.
X-RAY CRYSTALLOGRAPHY
The crystals were mounted in turn on a KUMA-4 au-
tomatic four-circle diffractometer and used for data
collection. All three-dimensional X-ray intensity
data were collected with graphite monochromated
FIGURE 1 The molecular conformation of 4-1 with atom
numbering.
˚
Cu-K radiation (k ס 1.54178 A) at room tempera-
␣
ture with the x-2h scan modes. The unit cell param-
eters were determined from least-squares refinement
of the setting angles of 99 reflections in the h range
5
–60Њ. Details concerning crystal data and refine-
ment are given in Table 1. Examination of two stan-
dard reflections, monitored after each 100 reflec-
tions measured, showed 11.6% loss of the intensity
for 4-1, 1.18% for 4-2, and 3.59% for 4-3. During the
data reduction the decay correction coefficients were
taken into account. The transparent, colorless crys-
tals of 4-1, 4-2, and 4-3 did not change their appear-
ances during the data collection. Lorentz-polariza-
tion correction was applied to the intensity data. The
maximum and minimum transmission factors were
0.5989 and 0.5989 for 4-1, 0.4100 and 0.2687 for 4-
FIGURE 2 The molecular conformation of 4-2 with atom
numbering.
2, 0.5803 and 0.3358 for 4-3. The structures of the
crystals were solved by direct methods and subse-
quently completed by difference Fourier recycling.
All the nonhydrogen atoms were refined anisotropi-
cally using full-matrix, least-squares technique on
which were sulfurized, in a reaction which has been
shown to proceed with retention of configuration at
phosphorus [4], to give crystalline 2-dialkylamino-
2
3
,4-dimethyl-5-phenyl-1,3,2-oxazaphospholane sul-
F . The hydrogen atoms were treated as riding on the
i
˚
phides (4), R ס Pr (4-1), Et (4-2), Me (4-3) (Scheme
).
adjacent carbon atom [d(C–H) ס 0.96 A] and refined
1
with the individual isotropic temperature factor

1
48 Kruszynski, Bartczak, and Majewski
a
TABLE 1 Crystal Data
4-1
4-2
4-3
Empirical formula
Formula weight
Crystal system, space group
Unit cell dimensions (A) a
C H N OPS
326.43
Orthorhombic, P2 2 2
7.481(1)
11.536(1)
22.226(2)
C H N OPS
298.37
Orthorhombic, P2 2 2
6.888(1)
9.420(1)
25.706(4)
C H N OPS
270.32
Monoclinic, P21
6.637(1)
11.616(1)
9.565(1)
98.94(1)Њ
728.46(15)
2, 1.232
16
27
2
14 23
2
12 19
2
1
1
1
1 1 1
˚
b
c
b
˚
3
Volume (A )
1918.1(4)
1667.9(4)
4, 1.188
3
Z, Calculated density (mg/m ) 4, 1.130
Absorption coefficient (CuK␣)
מ1
(mm
)
2.28
704
2.58
640
2.91
288
F (000)
Crystal size (mm)
h range for data collection (Њ)
Index ranges
0.25 ן 0.25 ן 0.25
3.98–75.19
מ9 Յ h Յ 9,
מ14 Յ k Յ 14, מ1 Յ l Յ 27
8023/3916
0.1028
0.42 ן 0.44 ן 0.69
3.44–80.26
מ8 Յ h Յ 1,
מ12 Յ k Յ 1, מ1 Յ l Յ 32
2824/2617
0.0609
0.21 ן 0.36 ן 0.48
4.68–82.83
מ8 Յ h Յ 8, מ14
Յ k Յ 14, מ12 Յ l Յ 5
3457/3068
0.0770
Reflections collected/unique
Rint
Completeness
Goodness-of-fit on F
99.4% to 2h ס 75.19Њ
0.912
100.0% to 2h ס 80.26Њ
1.061
96.5% to 2h ס 96.5Њ
1.110
2
Final R indices [l Ͼ 2r(l)] R1
wR2
R indices (all data) R1
wR2
0.0466,
0.0944
0.2215,
0.1439
0.0390,
0.1089
0.0433,
0.1120
0.0576,
0.1636
0.0645,
0.1898
No. of parameters
Flack parameter
Extinction coefficient
Largest diff. peak and hole
190
0.02(4)
–
173
0.02(3)
0.0074(8)
155
0.06(4)
0.031(4)
˚
מ3
(max/min DF), exA
0.143/מ0.197
0.416/מ0.210
0.409/מ0.290
a
˚
Details in common: diffractometer KUMA4, T ס 293 K, k(CuK␣) ס 1.54178 A, decay correction coefficient was used, refinement method: full-
2
matrix least-squares on F , the hydrogen atom positions were set in calculated positions and were treated as riding on the adjacent carbon,
software: SHELXS97, SHELXL97, XP (SHELXTL).
equal to 1.5 times the value of equivalent tempera-
ture factor of the parent carbon atom for hydrogen
atoms bonded in methyl groups and 1.2 for all other
hydrogen atoms. The solutions and refinements
were performed with SHELXS97 [6] and
SHELXL97 [7]. The graphical manipulations were
performed using the XP routine of the SHELXTL
The molecular geometries of all compounds 4
determined are similar. Only slight differences exist
in the bonding pattern of oxazaphospholane rings,
mainly in the structure of 4-3. The greatest differ-
ence is found in the length of the bond C(1)–O(1)
(Table 2). The bonds P(1)–S(1) and P(1)–N(2) don’t
depend on substituents and are the same within the
range of three standard deviations. The sum of bond
angles at the ring C(2) atom increase and at N(1)
decrease with an increase of the size of the substit-
uent, which indicates that the atom N(1), gains more
of a pyramidal configuration in opposition to C(1),
the configuration of which become less pyramidal.
This affects the conformation of the oxazaphospho-
lane rings. The rings exist in crystals in the envelope
conformation with C(2) at the flap. Maximum devi-
ations from calculated least-squares planes through
[8]. Atomic scattering factors were those incorpo-
rated in the computer programs. Bond distances are
listed in Table 2 and angles in Table 3. Full crystal-
lographic details have been deposited with CCDC
[9].
RESULTS AND DISCUSSION
A perspective view of each of the structures together
with their atom numbering scheme are shown in
Figure 1, 2, and 3, hydrogen atoms being omitted for
clarity. Because the molecules exhibited rather large
thermal motion, structures are plotted with 30%
probability of thermal ellipsoids.
atoms C(1)–O(1)–P(1)–N(1) are 0.044(2), 0.012(1),
0.034(2) A˚ in the 4-1, 4-2, and 4-3 structures, respec-
tively, and the same also occurs for atom O(1). The
flapping atom C(2) deviates from the described least-

Conformation of 1,3,2-Oxazaphospholane Ring in 2-Dialkylamino-3,4-dimethyl-5-phenyl-1,3,2-oxazaphospholaneSulfides 149
˚
TABLE 2 Bond Lengths (A)
TABLE 3 Bond Angles (Њ)
4-1
4-1
4-2
4-3
4-2
4-3
P(1)–O(1)
P(1)–N(2)
P(1)–N(1)
P(1)–S(1)
N(1)–C(4)
N(1)–C(2)
O(1)–C(1)
C(1)–C(5)
C(1)–C(2)
C(2)–C(3)
C(5)–C(6)
C(5)–C(10)
C(6)–C(7)
C(7)–C(8)
C(8)–C(9)
C(9)–C(10)
N(2)–C(11)
N(2)–C(14)
N(2)–C(13)
N(2)–C(12)
1.608(3)
1.632(4)
1.646(4)
1.921(2)
1.455(6)
1.479(6)
1.459(5)
1.498(7)
1.539(6)
1.518(6)
1.374(7)
1.391(7)
1.362(8)
1.372(10)
1.363(11)
1.401(8)
1.481(7)
1.502(7)
1.600(2)
1.629(2)
1.645(2)
1.935(1)
1.451(3)
1.466(3)
1.449(3)
1.505(3)
1.538(3)
1.521(3)
1.380(4)
1.378(4)
1.396(5)
1.365(7)
1.363(6)
1.388(4)
1.472(3)
1.609(3)
1.628(4)
1.622(4)
1.932(1)
1.452(6)
1.465(5)
1.423(5)
1.507(6)
1.507(6)
1.516(6)
1.370(7)
1.388(8)
1.398(12)
1.369(16)
1.358(16)
1.392(8)
1.446(6)
O(1)–P(1)–N(2)
O(1)–P(1)–N(1)
N(2)–P(1)–N(1)
O(1)–P(1)–S(1)
N(2)–P(1)–S(1)
N(1)–P(1)–S(1)
C(4)–N(1)–C(2)
C(4)–N(1)–P(1)
C(2)–N(1)–P(1)
C(1)–O(1)–P(1)
O(1)–C(1)–C(5)
O(1)–C(1)–C(2)
C(5)–C(1)–C(2)
N(1)–C(2)–C(3)
N(1)–C(2)–C(1)
C(3)–C(2)–C(1)
C(6)–C(3)–C(10)
C(6)–C(5)–C(1)
C(10)–C(5)–C(1)
C(7)–C(6)–C(5)
C(6)–C(7)–C(8)
C(9)–C(8)–C(7)
C(8)–C(9)–C(10)
C(5)–C(10)–C(9)
C(11)–N(2)–P(1)
C(11)–N(2)–C(14)
109.2(2)
94.1(2)
109.1(1)
94.2(1)
110.3(2)
94.7(2)
106.1(2)
111.9(1)
114.9(2)
118.6(2)
119.1(4)
121.3(4)
110.9(3)
114.4(3)
108.6(4)
106.2(4)
116.7(4)
114.3(4)
102.6(4)
116.6(4)
118.4(5)
119.5(6)
122.0(6)
121.5(7)
119.7(8)
121.1(8)
118.9(8)
120.3(6)
126.6(4)
116.1(4)
117.0(4)
114.6(5)
114.6(6)
113.2(6)
112.6(6)
114.0(6)
111.0(6)
107.9(1)
113.9(1)
111.8(1)
118.5(1)
119.4(2)
121.4(2)
111.7(1)
113.9(1)
110.2(2)
105.6(2)
115.1(2)
113.8(2)
101.5(2)
114.9(2)
119.5(2)
118.5(2)
121.9(2)
119.6(4)
120.3(4)
120.3(3)
120.1(4)
120.2(3)
124.6(2)
105.2(2)
112.1(1)
112.5(2)
120.6(2)
120.6(4)
124.4(3)
111.0(3)
111.9(2)
110.2(3)
106.4(3)
116.4(3)
112.4(4)
101.2(3)
114.6(4)
119.3(5)
118.6(5)
122.1(4)
119.2(8)
121.4(7)
119.3(7)
120.4(9)
120.3(6)
122.5(4)
a
b
c
1.487(3)
1.470(8)
a
a
a
c
b
b
C(11)–C(12)
C(11)–C(13)
C(14)–C(16)
C(14)–C(15)
C(11)–C(12)
C(13)–C(14)
1.521(7)
1.530(8)
1.493(7)
1.518(8)
1.488(5)
1.471(5)
a
a
C(14)–N(2)–P(1)
N(2)–C(11)–C(12)
N(2)–C(11)–C(13)
a
Only for 4-1.
a
a
b
Only for 4-2.
c
Only for 4-3.
a
a
C(12)–C(11)–C(13)
a
C(16)–C(14)–N(2)
C(16)–C(14)–C(15)
˚
squares planes by 0.506(7), 0.532(3), and 0.547(5) A,
respectively, for 4-1, 4-2, and 4-3, which is consistent
with an enlargement of the angle between planes
C(1)–O(1)–P(1)–N(1) and C(1)–C(2)–N(1). These an-
gles amount to 32.36 (51), 34.12 (20) and 35.62 (31)Њ.
Only the five-membered ring of 4-2 forms an almost
a
N(2)–C(14)–C(15)
C(13)–N(2)–P(1)
b
119.86(6)
114.6(3)
113.1(3)
115.4(2)
b
b
b
c
N(2)–C(11)–C(12)
C(14)–C(13)–N(2)
C(11)–N(2)–C(13)
C(11)–N(2)–C(12)
115.6(5)
118.9(3)
c
C(12)–N(2)–P(1)
ideal envelope with asymmetry parameters DC ס
s
a
Only for 4-1.
1
.08(16), DC ס 16.62(19) [3]. In 4-3, the envelope is
b
2
Only for 4-2.
c
slightly distorted (asymmetry parameters DC ס
Only for 4-3.
s
5
.78(35), DC ס 11.69(28)), and for 4-1, there is
2
rather a combination of a C(2)-envelope and half
chair than only an envelope (asymmetry parameters
DC ס 10.50(44), DC ס 4.93(37)). Moreover, the tor-
in the region of C(10), which causes a small length-
ening of C(10)–C(5) and C(10)–C(9) bonds. With an
increase in the size of the substituent, the S(1) atom
becomes more equatorial and the N(2) atom be-
comes less equatorial in relation to the calculated
least-square plane through the N(1)–P(1)–O(1)–C(1)
atoms, and finally, for 4-3, the angles between the
S(1)-plane and the N(2)-plane are equal within ex-
perimental error. The environments of the P atoms
in all of the compounds are comparable and have
the geometry of a distorted tetrahedron. There is
only one angle considerably smaller than tetra-
hedral: the five-membered ring angle O(1)–P(1)–
s
2
sion angle N(1)–P(1)–O(1)–C(1) in 4-1 has an oppo-
site sign to that of 4-3, which means that the last
square plane calculated through these atoms is
twisted in the opposite direction. Values of torsion
angles and placement of asymmetry parameters are
shown in Figure 4. The angle between the least-
squares planes calculated through N(1)–P(1)–O(1)–
C(1) and the phenyl ring increases with enlargement
of the substituent and has values of 37.26(24)Њ for 4-
3, 42.86(12)Њ for 4-2, and 53.11(15)Њ for 4-1. The
phenyl ring in 4-1 shows symptoms of slight disorder

1
50 Kruszynski, Bartczak, and Majewski
R. Z.; Turdybekov, K. M.; Struchkov, Yu. T. Zh
Obshch Khim 1992, 62, 1522–1530; (t) Peper, V.;
Stingl, K.; Thumler, H.; Saak, W.; Haase, D.; Pohl, S.;
Juge, S.; Martens, J. Liebigs Ann Chem 1995, 2123–
N(1), as expected [1,3]. The N(1)–O(1)–N(2) angle is
smaller, and the O(1)–P(1)–S(1) and N(1)–P(1)–S(1)
angles are slightly larger than tetrahedral. The larg-
est angle is that of N(1)–P(1)–S(1). The N(2)–P(1)–
S(1) angle is practically tetrahedral. In the structure
of the 4-3 atom, N(1) has nearly a planar coordina-
2
131; Antipin, M. Yu.; Struchkov, Yu. T.; Tikhonina,
N. A.; Gilyarov, V. A.; Kabachnik, M. I. Zh Strukt
Khim 1981, 22, 93–98; (u) Duthu, B.; El Abed, K.;
Houalla, D.; Wolf, R.; Jaud, J. Can J Chem 1992, 70,
tion, as shows by the sum of angles being equal to
8
09–816; (v) Sournies, F.; Zai, K.; Vercruysse, K.; La-
barre, M. C.; Labarre, J. F. J Mol Struct 1997, 412, 19–
6; (w) Hersh, W. H.; Xu, P.; Simpson, C. K.; Wood,
2
3
56.0Њ. This planarity testifies to sp hybridization at
nitrogen. This probably causes a shortening of the
2
˚
P(1)–N(1) bond, 1.622(4) A, as compared with
T.; Rheingold, A. L. Inorg Chem 1998, 37, 384–385;
(x) Welch, S. C.; Levine, J. A.; Bernal, I.; Cetrullo, J. J
Org Chem 1990, 55, 5991–5995; (y) Pastor, S. D.; Rod-
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˚
1
.646(4) and 1.645(2) A for 4-1 and 4-2, respectively.
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6
3–68; (s) Gazaliev, A. M.; Nurkenov, O. A.; Kasenov,