P-chiral phosphinoselenoic chlorides and optically active P-chiral phosphinoselenoic amides: Synthesis and stereospecific interconversion with extrusion and addition reactions of the selenium atom

Article abstract of DOI:10.1246/cl.2004.878

An efficient synthesis of P-chiral phosphinoselenoic chlorides and the first optically active P-chiral phosphinoselenoic amides was successfully achieved. Stereospecific interconversion with the extrusion of selenium atom from optically active phosphinose

Full text of DOI:10.1246/cl.2004.878

878
Chemistry Letters Vol.33, No.7 (2004)
P-Chiral Phosphinoselenoic Chlorides and Optically Active P-Chiral Phosphinoselenoic Amides:
Synthesis and Stereospecific Interconversion with Extrusion
and Addition Reactions of the Selenium Atom
Tsutomu Kimura and Toshiaki Muraiꢀ
Department of Chemistry, Faculty of Engineering, Gifu University, Yanagido, Gifu 501-1193
(Received May 14, 2004; CL-040555)
An efficient synthesis of P-chiral phosphinoselenoic chlor-
ides and the first optically active P-chiral phosphinoselenoic
amides was successfully achieved. Stereospecific interconver-
sion with the extrusion of selenium atom from optically active
phosphinoselenoic amides and the addition of selenium atom
to optically active aminophosphines were also investigated.
were observed at 88 ꢁ 23 ppm. Introduction of an aryl group
to the phosphorus atom shifted the signals upfield. In the
77Se NMR spectra, signals of chlorides 1 were observed in the
range of ꢂ219 to ꢂ48 ppm, and those of the chlorides bearing
two aryl groups 1d–1f were downfield of those of 1a–1c. Typical
coupling constants of P=Se bonds (846 ꢁ 8 Hz) were detected,
and these were almost independent of the substituents on the
phosphorus atom.
P-Chiral organophosphorus compounds1 are important not
only in stereochemical studies of organophosphorus compounds
but also as chiral ligands in transition metal-catalyzed asymmet-
ric reactions.2 Their key precursors, P-chiral chlorophosphines,3
and phosphinic chlorides,4 have been reported, but these have to
be handled carefully because of their sensitivity toward air and
water. Alternatively, P-chiral phosphinothioic chlorides3,5 have
been reported, although their synthesis involves several steps
from readily available materials. The main drawback of phos-
phine oxides and sulfides is the fact that their reduction to triva-
lent phosphorus compounds requires strong reducing agents.1
Moreover, the stereochemical course of the reduction depends
on the reducing agents. Very recently, P-chiral chlorophosphine
boranes have been introduced for use as good precursors of P-
chiral organophosphorus compounds.6 Nevertheless, more sta-
ble, but still reactive, P-chiral chlorophosphine equivalents are
needed to conveniently provide optically active P-chiral organo-
phosphorus compounds. We recently studied the synthesis and
properties of phosphinoselenoic acid derivatives.7 We report
here the synthesis of P-chiral phosphinoselenoic chlorides and
the first optically active P-chiral phosphinoselenoic amides.
Stereospecific interconversion with the extrusion of selenium
atom from optically active phosphinoselenoic amides and the ad-
dition of selenium atom to optically active aminophosphines are
also described.
Initially, a one-pot synthetic procedure to give P-chiral phe-
nylphosphinoselenoic chlorides8 1 was developed. After several
disappointing results, the dropwise addition of a THF solution of
Grignard reagent to a suspension of PhPCl2 and elemental sele-
nium in THF enabled the highly efficient synthesis of P-chiral
phosphinoselenoic chlorides 1 (Table 1).9 Notably, no decompo-
sition of 1 took place during purification by column chromatog-
raphy on silica gel. Various alkyl Grignard reagents were used to
give the chlorides 1a–1c in high to excellent yields (Entries 1–3).
In reactions with aryl Grignard reagents, the yields of the prod-
ucts 1d–1f decreased to some extent (Entries 4–6).10 In all cases,
the chlorides obtained were stable under air and in water. This is
in marked contrast to the stability of phosphinic chlorides, which
are readily hydrolyzed.
Table 1. Synthesis and selected NMR spectroscopic data of
P-chiral phosphinoselenoic chlorides 1a
Se
RMgX
PhPCl
+ Se
P
2
Ph
Cl
THF
0 °C, dropwise
toluene
reflux, 1 h
R
1
Yieldb 31P NMR 77Se NMR JP{Se
1
Entry
1
R
%
ppm
ppm
Hz
1
2
3
4
5
6
1a
1b
1c
i-Pr
c-C6H11
t-Bu
91
96
94
38
72
68
100.2
95.8
111.0
66.3
72.1
69.9
ꢂ219:7 841.9
ꢂ196:5 840.4
ꢂ171:5 837.3
ꢂ48:4 840.4
ꢂ68:4 846.4
ꢂ67:3 853.9
1d o-MeOC6H4
1e p-MeC6H4
1f p-ClC6H4
aThe reaction was carried out with 8–30 mmol of PhPCl2 and al-
kyl (1.0 equiv.) or aryl (0.2 equiv.) Grignard reagents in the pres-
ence of elemental selenium (1.1 equiv.) in THF under Ar.
bYields of isolated products based on the Grignard reagents.
P-Chiral phosphinoselenoic chlorides 1 showed high reac-
tivity toward heteroatom-containing nucleophiles at the phos-
phorus atom. Among them, the first example of optically active
P-chiral phosphinoselenoic amides 3 was synthesized by react-
ing 1 with optically active lithium amides 2 (Eq 1).11 Two dia-
stereomers of 3 were formed in a nearly equal ratio in high
yields, and the two diastereomers were successfully separated
by column chromatography on silica gel.
Li
Se
P
R
Se
P
Ph
Se
P
R
N
R'
H
2
+
Ph
(1)
Ph
R
N
N
Cl
R'
R'
THF
0 °C then rt, 2 h
H
H
1
(R ,S)-3
P
(S ,S)-3
P
3a: R = i-Pr, R' = c-C H
40%
41%
41%
51%
6
11
3b: R = c-C H , R' = 1-Naphthyl 34%
6
11
3c: R = t-Bu, R' = Ph
34%
The absolute configuration of phosphinoselenoic amide
(RP; S)-3c was determined by X-ray molecular structure analysis
(Figure 1).12 The phosphorus atom adopts a slightly distorted tet-
rahedral structure.
The phosphinoselenoic chlorides 1 were characterized spec-
troscopically. In the 31P NMR spectra, signals of chlorides 1
Finally, interconversion between optically active phosphi-
noselenoic amides and trivalent aminophosphines13 was studied
Copyright Ó 2004 The Chemical Society of Japan

Chemistry Letters Vol.33, No.7 (2004)
879
‘‘Asymmetric Catalysis in Organic Synthesis,’’ John Wiley &
Sons, New York (1994).
3
4
5
J. Omelanczuk, Heteroat. Chem., 3, 403 (1992).
L. Horner and B. Schlotthauer, Phosphorus Sulfur, 4, 155 (1978).
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mun., 1977, 66.
´
6
a) C. Bauduin, D. Moulin, E. B. Kaloun, C. Darcel, and S. Juge,
J. Org. Chem., 68, 4293 (2003). b) H. Lam, D. J. Aldous, and
K. K. Hii, Tetrahedron Lett., 44, 5213 (2003).
7
8
T. Murai, T. Kimura, A. Miwa, D. Kurachi, and S. Kato, Chem.
Lett., 2002, 914.
P-Chiral phosphinoselenoic chlorides are rare, but not unknown:
E. V. Bayandina, I. A. Nuretdinov, and L. V. Nurmukhamedova,
Zh. Obshch. Khim., 48, 2673 (1978).
Figure 1. ORTEP drawing of (RP; S)-3c with thermal ellipsoids
(non-H atoms) at the 50% probability level. Hydrogen atoms
(except for H1 and H2) areꢃomitted for clarity. Selꢃected bond
ꢀ
lengths [A], bond angles [ ] and torsion angle [ ]: P1–Se1
9
Typical experimental procedure for the synthesis of the chlorides
1: To a suspension of elemental selenium (33.0 mmol) in THF
(150 mL) was added PhPCl2 (30.0 mmol) at room temperature
under an Ar atmosphere. To this mixture was added t-BuMgCl
(1.0 M solution in THF, 30.0 mmol) in THF (120 mL) dropwise
over a period of 1 h at 0 ꢃC with vigorous stirring. After the sol-
vent was removed, toluene (80 mL) was added to the residue, the
mixture was stirred under reflux in toluene for 1 h, and the insolu-
ble parts were filtered off. After the solvent was removed, the re-
sulting oil was purified by column chromatography on silica gel
(hexane:CH2Cl2 = 1:1) to give 1c (94%) as a colorless solid.
2.1180(7), P1–N1 1.652(2); Se1–P1–N1 113.00(8), Se1–P1–
C1 110.75(9), Se1–P1–C2 112.47(10), N1–P1–C1 105.7(1),
N1–P1–C2 106.8(1), P1–N1–C3 126.2(2); Se1–P1–N1–C3
ꢂ12:0ð3Þ.
because the stereochemical outcome of this type of reaction is of
great interest.1 The selenium atom of 3 was completely extruded
at room temperature by reacting with Bu3P (Scheme 1). Notably,
the extrusion reaction of the selenium atom of (RP; S)-3c
proceeded with retention of configuration. Furthermore, the ad-
dition of a selenium atom to aminophosphine14 (SP; S)-4c also
proceeded with retention of configuration. An identical stereo-
chemical course was observed for a similar reaction of the dia-
stereomer (SP; S)-3c.
10 It is very important to control the ratio of the reagents. Otherwise,
products in which two equivalents of the Grignard reagent are
introduced to the phosphorus atom of PhPCl2 are formed.
11 Typical experimental procedure for the synthesis of the amides 3:
To a solution of (S)-1-phenylethylamine (2.2 mmol) in THF
(5 mL) was added butyllithium (1.6 M solution in hexane,
2.0 mmol) at 0 ꢃC, and the reaction mixture was stirred at that
temperature for 10 min. To a solution of 1c (2.0 mmol) in THF
(5 mL) was added the reaction mixture at 0 ꢃC, and the mixture
was stirred at room temperature for 2 h. The mixture was extract-
ed with CH2Cl2 (50 mL), and the organic layer was washed with
water (50 mL ꢄ 2), dried over MgSO4 and filtered off. After the
solvent was removed, the resulting oil was purified by column
chromatography on silica gel (hexane:CH2Cl2 = 1:1) to give
(RP; S)-3c (Rf ¼ 0:4, 34%) as a colorless solid and (SP; S)-3c
(Rf ¼ 0:3, 51%) as a colorless solid. The optical purity of 3
retention
Bu P
3
retention
Se
b
Se
P
(R ,S)-3c
P
P
t-Bu
t-Bu
Ph
N
Ph
N
Ph
a
Ph
(R ,S)-3c
H
H
(S ,S)-4c
P
P
retention
retention
Bu P
3
Se
b
(S ,S)-3c
P
(R ,S)-4c
P
(S ,S)-3c
P
a
Scheme 1. Stereochemistry of interconversion between 3c and
4c. (a) THF, rt, 1 h; (b) THF, rt, 15 min.
20
was determined by 31P NMR spectra. ½ꢀꢅD (c ¼ 1:0, CH2Cl2):
(RP; S)-3a, ꢂ33ꢃ; (SP; S)-3a, þ25ꢃ; (RP; S)-3b, ꢂ13ꢃ; (SP; S)-
3b, þ27ꢃ; (RP; S)-3c, ꢂ40ꢃ; (SP; S)-3c, ꢂ62ꢃ.
In summary, we have reported the synthesis of P-chiral
phosphinoselenoic chlorides and the first optically active P-chi-
ral phosphinoselenoic amides. We described the stereospecific
interconversion between the amides and aminophosphines. The
broad applicability of chlorides has promoted synthetic studies
on a series of P-chiral phosphinoselenoic acid derivatives.15
The application of optically active P-chiral phosphinoselenoic
amides and aminophosphines as chiral ligands13,16 is also under
investigation.
12 Crystallographic data for (RP; S)-3c: C18H24NPSe, fw ¼ 364:33,
orthorhombic, space group P212121, a ¼ 7:223ð2Þ, b ¼
ꢀ
ꢀ 3
13:269ð4Þ, c ¼ 19:121ð6Þ A, V ¼ 1832ð1Þ A , Z ¼ 4, Dcalcd
¼
1:320 g cmꢂ3, T ¼ 296 K, R ¼ 0:045 Rw ¼ 0:059, Flack param-
eter = 0.006(9), 3474 reflections (I > 2ꢁðIÞ). Crystallographic
data reported in this paper have been deposited with the Cam-
bridge Crystallographic Data Center (CCDC) as supplementary
publication no. CCDC-235151. Copies of the data can be ob-
tained free of charge on application to CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK (fax: (+44)1223-336-003; e-mail:
deposit@ccdc.cam.ac.uk).
This research was supported by Grant-in-Aid for Scientific
Research on Priority Area (No. 16033224, ‘‘Reaction Control
of Dynamic Complexes’’) from the Ministry of Education,
Culture, Sports, Science and Technology of Japan.
13 a) R. Ewalds, E. B. Eggeling, A. C. Hewat, P. C. J. Kamer, P. W.
N. M. van Leeuwen, and D. Vogt, Chem.—Eur. J., 6, 1496
´
(2000). b) D. Moulin, C. Darcel, and S. Juge, Tetrahedron:
Asymmetry, 10, 4729 (1999).
References and Notes
1
14 The absolute configuration of 4c was assigned on the basis of
their NMR spectroscopic data, and the optical purity of 4c was
determined by 31P NMR spectra: O. I. Kolodiazhnyi, E. V.
Gryshkun, N. V. Andrushko, M. Freytag, P. G. Jones, and R.
Schmutzler, Tetrahedron: Asymmetry, 14, 181 (2003).
15 R. P. Davies and M. G. Martinelli, Inorg. Chem., 41, 348 (2002).
16 a) Y. K. Kim, T. Livinghouse, and Y. Horino, J. Am. Chem. Soc.,
125, 9560 (2003). b) M. Shi and W.-S. Sui, Tetrahedron:
Asymmetry, 11, 835 (2000).
K. M. Pietrusiewicz and M. Zablocka, Chem. Rev., 94, 1375
(1994).
2
a) T. Imamoto, in ‘‘Handbook of Organophosphorus Chemistry,’’
ed. by R. Engel, Marcel Dekker, New York (1992), pp 1–53.
b) ‘‘Comprehensive Asymmetric Catalysis,’’ ed. by E. N.
Jacobsen, A. Pfaltz, and H. Yamamoto, Springer, Berlin
(1999). c) ‘‘Catalytic Asymmetric Synthesis,’’ 2nd ed., ed. by
I. Ojima, VCH Publishers, Weinheim (2000). d) R. Noyori,
Published on the web (Advance View) June 14, 2004; DOI 10.1246/cl.2004.878