Conversion of Thio- And Selenophosphoryl into Phosphoryl Group by Perfluoro cis-2,3-Dialkyloxaziridines

Full text of DOI:10.1021/jo970572a

J . Org. Chem. 1997, 62, 6401-6403
6401
Con ver sion of Th io- a n d Selen op h osp h or yl
in to P h osp h or yl Gr ou p by P er flu or o
cis-2,3-Dia lk yloxa zir id in es
Alberto Arnone,† Barbara Novo,† Massimo Pregnolato,*,‡
Giuseppe Resnati,*,† and Marco Terreni‡
Dipartimento di Chimica Farmaceutica, Universita` degli
Studi, 12 via Taramelli, I-27100 Pavia, Italy, and
C.N.R.-Centro di Studio sulle Sostanze Organiche Naturali,
Dipartimento di Chimica, Politecnico, 7 via Mancinelli,
I-20131 Milano, Italy
the corresponding oxide 3c and elemental selenium in
few minutes at -40 °C.
Received March 31, 1997
Compounds containing the thiophosphoryl moiety (PdS)
have found diversified applications in chemistry. They
have been employed as chiral auxiliary agents in ex-
traordinarily diastereoselective alkylation reactions,1 in
the resolution of racemic phenols2 and in the deter-
mination of the optical purity of alcohols and amines.3
Thiophosphoryl derivatives also proved useful in a vast
number of biological investigations. They are effective
tools for the study of enzyme-catalyzed reactions,4 potent
inhibitors of metalloproteases,5 and promising candidates
for use in oligonucleotide therapeutics.6 All of these
properties are obviously shared by the substances pos-
sessing the phosphoryl group (PdO).1-6 An easy trans-
formation of the thiophosphoryl into phosphoryl com-
pounds would provide a much greater flexibility in
preparing and studying chemical and biological proper-
ties of both classes of tetracoordinated phosphorus com-
pounds.
In the course of a study on the oxidation of some
organophosphorus agrochemicals by perfluoro cis-2,3-
dialkyloxaziridines 1a ,b,7 we noticed that these oxaziri-
dines were able to transform phosphorothioates into
corresponding phosphates. The noteworthy effectiveness
of the observed reaction prompted us to test the conver-
sion of the thiophosphoryl into phosphoryl group on other
structurally different phosphorus(V) derivatives, and
here we describe the generality of the process.
High yields of phosphoryl products were obtained also
when alkoxy and amido residues were bound to the
phosphorus atom. Under the usual reaction conditions
alkylthiophosphonates and (difluoromethylene)thiophos-
phonates, 2e and 2f, respectively, afforded nearly quan-
titative yields of the corresponding phosphonate 3e,f.
Some commonly employed agrochemicals8 and their
metabolites such as Parathion (2g) and its O-methyl
analogue (2h ), Fenitrothion (2i), Bromophos (2j), the
sulfinyl derivatives of demethon-O (2l), and demethon-
O-methyl (2k ) all have a dialkyl aryl or trialkyl phos-
phorothioate moiety which is oxidatively desulfurized
cleanly to give corresponding phosphate products 3h -l.
At room temperature the reaction occurs very rapidly also
on these substrates, but best yields are obtained per-
forming the desulfurization in the cold for longer reaction
times (Table). Side reactions are thus avoided (partial
hydrolyses of labile p-nitrophenoxy residue in 2g-i or
sulfinyl to sulfonyl oxidation in 2k ,l).
The diethylthiophosphoramidate 2m and the 1,3,2-
oxazaphospholidine 2-sulfide 2n , bearing one and two
amido residues at phosphorus, both gave desired products
3m ,n in good yields. Once again, lower reaction tem-
peratures allowed higher yields to be obtained starting
from the thiophosphoramidate 2m having two labile
p-nitrophenoxy residues, and it is interesting to observe
that desulfurization of oxazaphospholidine sulfide 2n
occurred with complete stereoselectivity (>98%) and
inversion of configuration at phosphorus (eq 2).9 The
stereochemical course of the thiophosphoryl into phos-
phoryl transformation has been described for various
reagents,11 and it was shown to depend on the substituent
at phosphorus,11i the employed oxidizing agent,10a,11n and
the reaction conditions.10c,11d,i It is noteworthy that all
When trialkyl- and triarylphosphine sulfides 2a -d
were reacted with equimolar amounts of the oxaziridine
1a in an halogenated solvent at room temperature, high
yields of the corresponding oxides 3a -d were formed (eq
1). Reactions were complete in less than 5 min, and the
only observed coproducts were the azaalkene 4a , as
shown by 19F NMR of crude reaction mixtures, and
elemental sulfur, as proven by microanalyses and exact
mass of the formed yellowish solid. Similarly, tri-
phenylphosphine selenide (2o) afforded quantitatively
(8) Worthing, C. R. The Pesticide Manual, 7th ed.;
A World
Compendium; British Crop Protection Council: Croydon, U.K., 1993.
(9) The (2S,4R,5S) configuration was assigned to the product 3n
obtained by oxidizing (2S,4R,5S)-2n with oxaziridines 1a ,b as no NOE
was observed in this diastereoisomer between the methyl on C-4 and
the methylene and aromatic protons of the benzylamido residue. This
observation suggested that the two groups are trans. In order to
confirm this assignment, (2S,4R,5S)-2n was oxidized with MCPBA.
This reagent is known to perform the oxidative desulfurization reaction
with retention of chirality on 2-(methylthio)-1,3,2-oxazaphospholidine
2-sulfides (ref 10a), phosphonamidothioates (ref 10b), phosphinothio-
ates (ref 10c), and phosphorothioates (ref 10d) and in fact a different
1,3,2-oxazaphospholidine 2-oxide 3n was formed which showed positive
NOE effects between the above described residues (see the Experi-
mental Section). These residues were thus in a cis relationship, and
the (2R,4R,5S) configuration could be assigned unequivocally to this
product.
† C.N.R., Milano; e-mail: resnati@dept.chem.polimi.it.
‡ University of Pavia.
(1) (a) Kranz, M.; Denmark, S. E.; Swiss, K. A.; Wilson, S. R. J . Org.
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S0022-3263(97)00572-0 CCC: $14.00 © 1997 American Chemical Society

6402 J . Org. Chem., Vol. 62, No. 18, 1997
Notes
Ta ble 1. Oxid a tion of Th io- a n d Selen op h osp h or yl
zation of substrates 2b,c,f,n ,o were nearly the same for
the two reagents (Table 1).
Su bstr a tes 2a -o w ith Oxa zir id in es 1a ,b
In general, reaction conditions are milder than those
required by other reagents which perform the same
reactions. For instance, high temperatures (Me2SO,11d,f
chloral,11p H2O211i), long reaction times (trifluoroacetic
anhydride11s), or great excess of the reagent (Me2SO,11d,f
ethylene oxide,11o chloral11p) are often required. The
reaction workup is notably simple since filtration of the
crude reaction mixtures (to remove sulfur) and rotary
evaporation (to eliminate excess oxaziridine 1a , if any,
and azaalkene 4a both of which are quite volatile
compounds) often afford desired products 3 in nearly pure
form.
In conclusion, perfluorooxaziridines 1 have previously
been shown to be useful reagents for the oxidation at
carbon,12a-f nitrogen,12g,h sulfur,12i,j and silicon12k sites.
Results here reported show how they are effective also
for the high yield and stereoselective transformation of
thio- and selenophosphoryl groups into phosphoryl groups
under mild reaction conditions in a wide variety of
phosphorus(V) derivatives (R1, R2, R3 ) alkyl, aryl,
O-alkyl, O-aryl, NH-alkyl, N-alkyl2 in 2 and 3).
Exp er im en ta l Section
Oxaziridines 1a ,b have been prepared in two steps starting
from commercially available perfluoro-tri-n-butyl- and -tri-n-
hexylamine.13 Dichloropentafluoropropane is a 43:56 mixture
of HCFC-225ca and HCFC-225cb (CF3CF2CHCl2 and CCl-
F2CF2CHClF, respectively) purchased from PCR incorporated.
Analytical instruments employed and spectral data format are
described in refs 7 and 12i. Starting compounds 2a -e,o have
been purchased from Aldrich, Fluka, Alfa, or Acros; 2g,h ,k ,l have
been prepared according to ref 7.
Dieth yl (1-Br om o-1,1-d iflu or om eth ylen e)th iop h osp h on -
a te (2f). A solution of diethyl (1-bromo-1,1-difluoromethylene)-
phosphonate (Aldrich, 1.07 g, 4.0 mmol) and 2,4-bis(4-methoxy-
phenyl)-1,3-dithia-2,4-diphosphetane 2,4-disulfide (Lawesson’s
reagent, 1.62 g, 4.0 mmol) in dry toluene (20 mL) was refluxed
with stirring under nitrogen for 2 h. The solvent was evaporated
under reduced pressure and the residue purified through flash
chromatography (n-hexane/ethyl acetate, 70:30) to give 736 mg
(2.60 mmol, 65% yield) of pure 2f: 1H NMR (CDCl3) δ 1.40, 4.33;
19F NMR (CDCl3) δ -62.3; 31P NMR (CDCl3) δ 69.5 (69.38).14
O,O-Bis-(4-n it r op h en yl) N,N-d iet h ylt h iop h osp h or a m i-
d a te (2m ). A suspension of N,N-diethylthiophosphoramidic
dichloride (1.00 g, 4.8 mmol) and sodium p-nitrophenate (1.56
g, 9.7 mmol) in EtOH was refluxed with stirring for 2 h. The
solvent was evaporated under reduced pressure and the residue
purified through flash chromatography (n-hexane/ethyl acetate,
80:20) to give 450 mg of 2m (1.10 mmol, 23% yield): 1H NMR
reagents but dimethyl sulfoxide11 are reported to give
retention of configuration when the phosphorus atom is
inserted in a cyclic moiety so that the stereochemical
behavior of oxaziridines 1 is quite unusual.
The perfluoro-cis-2-hexyl-3-pentyloxaziridine 1b showed
a reactivity quite similar to that of the 2-butyl-3-propyl
analogue 1a since yields, reaction times, and diastereo-
selection for the oxidative desulfurization and deseleni-
(CDCl3) δ 1.18 (t, 6H, J ) 7.2), 3.47 (dq, 4H, J H,H ) 7.2, J H,P
)
14.5), 7.37 (m, 4H, J H,P ) 1.6), 8.27 (m, 4H); 31P NMR (CDCl3)
δ 65.7. Anal. Calcd for C16H18N3O6PS: C, 46.71; H, 3.92; N,
10.21; S, 7.79. Found: C, 46.94; H, 4.18; N, 10.02; S, 7.97.
(2S,4R,5S)-2-(Ben zyla m in o)-1,3,2-oxa za p h osp h olid in e
2-Su lfid e (2n ). To a solution of 2-chloro-1,3,2-oxazaphospholi-
(11) Me2SO-H+ and Me2SO-I2: (a) Luckenbach, R. Synthesis 1973,
307. (b) Luckenbach, R.; Kern, M. Chem. Ber. 1975, 108, 3533. (c)
Mikolajczyk, M.; Luczak, J . Synthesis 1975, 114. (d) Okruszek, A.;
Stec, W. J . Tetrahedron Lett. 1982, 23, 5203. (e) Mikolajczyk, M.;
Luczak, J . Chem. Ind. (London) 1974, 701. (f) Guga, P.; Okruszek, A.
Tetrahedron Lett. 1984, 25, 2897. Me2SeO: (g) Mikolajczyk, M.;
Luczak, J . J . Org. Chem. 1978, 43, 2132. Me3SiOOSiMe3: (h)
Kowalski, J .; Wozniak, L.; Chojnowski, J . Phosphorus, Sulfur 1987,
30, 125. H2O2: (i) Stec, W. J .; Okruszek, A.; Michalski, J . J . Org. Chem.
1976, 41, 233. Dimethyldioxirane: (j) Sa´nchez-Baeza, F.; Durand, G.;
Barcelo´, D.; Messeguer, A. Tetrahedron Lett. 1990, 31, 3359. KMnO4:
(k) Horner, L. Pure Appl. Chem. 1964, 9, 225. (l) Horner, L.; Winkler,
H. Tetrahedron Lett. 1964, 175. (m) Stec, W.; Okruszek, A.; Michalski,
J . Angew. Chem., Int. Ed. Engl. 1971, 13, 491. N2O4 and HNO3: (n)
Michalski, J .; Okruszek, A.; Stec, W. J . Chem. Soc., Chem. Commun.
1970, 1495. Styrene oxide and chloral: (o) Guga, P.; Stec, W. J .
Tetrahedron Lett. 1983, 24, 3899. (p) Okruszek, A.; Stec, W. J . J .
Chem. Soc., Chem. Commun. 1984, 117. (q) Chan, T. H.; Finkenbine,
J . R. J . Am. Chem. Soc. 1972, 94, 2880. MCPBA: refs 10a-d. O3: (r)
Skowronska, A.; Krawczyk, E. Synthesis 1983, 509. Trifluoroacetic
anhydride: (s) Helinski, J ; Skrzypczynski, Z.; Wasiak, J .; Michalski,
J . Tetrahedron Lett. 1990, 31, 4081.
(12) (a) DesMarteau, D. D.; Petrov, V. A.; Montanari, V.; Pregnolato,
M.; Resnati, G. Tetrahedron Lett. 1992, 33, 7245. (b) DesMarteau, D.
D.; Donadelli, A.; Montanari, V.; Petrov, V. A.; Resnati, G. J . Am.
Chem. Soc. 1993, 115, 4897. (c) Arnone, A.; Cavicchioli, M.; Montanari,
V.; Resnati, G. J . Org. Chem. 1994, 59, 5511. (d) Arnone, A.; Bernardi,
R.; Cavicchioli, M.; Resnati, G. J . Org. Chem. 1995, 60, 2314. (e)
Cavicchioli, M.; Mele, A.; Montanari, V.; Resnati, G. J . Chem. Soc.,
Chem. Commun. 1995, 901. (f) Petrov, V. A.; Resnati, G. Chem. Rev.
1996, 96, 1809. (g) Balsarini, C.; Novo, B.; Resnati, G. J . Fluorine
Chem. 1996, 80, 31. (h) Bernardi, R.; Novo, B.; Resnati, G. J . Chem.
Soc., Perkin Trans. 1 1996, 2517. (i) DesMarteau, D. D.; Petrov, V.
A.; Montanari, V.; Pregnolato, M.; Resnati, G. J . Org. Chem. 1994,
59, 2762. (j) Be´gue´, J .-P.; M’Bida, A.; Bonnet-Delpon, D.; Novo, B.;
Resnati, G. Synthesis 1996, 399. (k) Cavicchioli, M.; Montanari, V.;
Resnati, G. Tetrahedron Lett. 1994, 35, 6329.
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(14) Piettre S. R. Tetrahedron Lett. 1996, 37, 4707.

Notes
J . Org. Chem., Vol. 62, No. 18, 1997 6403
dine 2-sulfide (Aldrich, 400 mg, 1.52 mmol) and triethylamine
(230 mg, 2.28 mmol) in THF (8 mL) was added benzylamine (163
mg, 1.52 mmol) at rt under stirring. After 2 h the reaction
mixture was washed with water and extracted with ether, and
the combined organic layers were dried (Na2SO4) and concen-
trated in vacuo. Flash chromatography (n-hexane/diethyl ether,
50:50) afforded 425 mg (1.28 mmol, 84% yield) of 2n : 1H NMR
(CDCl3) δ 0.73 (d, 3H, J H,H ) 6.8), 2.68 (d, 3H, J H,P ) 11.7), 3.58
2.81 (m, 2H), 2.93 and 3.07 (m, 2H), 3.81 (d, 6H, J H,P ) 11.2),
4.48 and 4.51 (m, 2H). Anal. Calcd for C6H15O5PS: C, 66.04;
H, 6.57; P, 13.45. Found: C, 66.27; H, 6.71; P13.28.
O,O-Dieth yl O-[2-(eth ylsu lfin yl)eth yl] p h osp h a te (3l):
oil; 1H NMR (CDCl3) δ 1.36 (dt, 6H, J H,H ) 7.2, J H,P ) 1.2), 1.37
(t, 3H, J H,H ) 7.5), 2.80 and 2.81 (m, 2H), 2.93 and 3.07 (m, 2H),
4.15 (dq, 4H, J H,H ) 7.2, J H,P ) 8), 4.46 and 4.50 (m, 2H); 31P
NMR (CDCl3) δ -1.0. Anal. Calcd for C8H19O5PS: C, 37.20;
H, 7.41; P, 11.99. Found: C, 37.42; H, 7.70; P, 11.86.
(ddq, 1H, J H,H ) 6.8 and 6.8, J H,P ) 9.1), 4.23 (dd, 1H, J H,H
)
15.8, J H,P ) 13.2), 4.24 (dd, 1H, J H,H ) 15.8, J H,P ) 12.1), 5.68
(br d, 1H, J H,H ) 6.8), 7.1-7.5 (m, 10H); 31P NMR (CDCl3) δ
80.6. Anal. Calcd for C17H21N2OPS: C, 61.43; H, 6.37; N, 8.43;
S, 9.65. Found: C, 61.64; H, 6.70; N, 8.70; S, 9.62.
O,O-Bis(4-n it r op h en yl) N,N-d iet h yla m in op h osp h a t e
(3m ): oil; 1H NMR (CDCl3) δ 1.13 (t, 6H, J ) 7.1), 3.29 (dq, 4H,
J H,H ) 7.1, J H,P ) 12.6), 7.40 (m, 4H, J H,P ) 1.0), 8.27 (m, 4H);
31P NMR (CDCl3) δ 0.3. Anal. Calcd for C16H18N3O7P: C, 48.61;
H, 4.59; N, 10.63. Found: C, 48.89; H, 4.73; N, 10.91.
(2S,4R,5S)-2-(Ben zyla m in o)-1,3,2-oxa za p h osp h olid in e
2-oxid e (3n ): 1H NMR (acetone-d6) δ 0.74 (d, 3H, J H,H ) 6.6),
2.59 (d, 3H, J H,P ) 10.0), 3.76 (ddq, 1H, J H,H ) 6.6 and 6.2, J H,P
) 16.7), 4.20 (d, 2H, J H,P ) 12.3), 5.57 (dd, 1H, J H,H ) 6.2, J H,P
) 3.5), 7.2-7.6 (m, 10H); 31P NMR (CDCl3) δ 24.5; NOE
experiments (acetone-d6), no enhancement (<0.1%) of NCH2,
NCH2ArHortho was observed on irradiation of CH3-4 and the
reverse. Anal. Calcd for C17H21N2O2P: C, 64.55; H, 6.69; N,
8.85. Found: C, 64.71; H, 6.80; N, 8.84.
Gen er a l P r oced u r e for th e Oxid a tive Desu lfu r iza tion
a n d Deselen iza tion of Com p ou n d s 2 w ith Oxa zir id in es
1a ,b. Syn th esis of Tr iisobu tylp h osp h in e Oxid e (3b). To
a solution of triisobutylphosphine sulfide 2b (200 mg, 0.85 mmol)
in CHCl3 (2 mL) was added a solution of the oxaziridine 1a (449
mg, 1 mmol) in HCFC-225ca/225cb (5 mL) at rt and under
nitrogen. After the reaction mixture was stirred for 5 min, the
starting compound had disappeared (TLC analysis). 19F NMR
of crude reaction mixture showed that the azaalkene (Z)-4a was
the only coproduct formed. The mixture was filtered, and the
exact mass and microanalysis of the separated yellowish solid
was that expected for elemental sulfur. Volatiles were removed
under reduced pressure to give 166 mg (0.76 mmol, 95% yield)
of nearly pure oxide 3b. An analytically pure sample was
obtained through flash chromatography (n-hexane/ethyl acetate,
20:80): 1H NMR (CDCl3) δ 1.08 (d, 18H, J H,H ) 6.4), 1.63 (dd,
6H, J H,H ) 6.4, J H,P ) 10.9), 2.09 (m, 3H); 31P NMR (CDCl3) δ
47.7. MS (CI, CH4) m/z 219 (M + 1). Anal. Calcd for
(2R,4R,5S)-2-(Ben zyla m in o)-1,3,2-oxa za p h osp h olid in e
2-Oxid e (3n ). MCP BA Meth od . m-Chloroperbenzoic acid (57
mg, 0.33 mmol) was added to a solution of (2S,4R,5S)-2n (100
mg, 0.30 mmol) in CHCl3. After 15 min the mixture was filtered
and the solution washed with dilute aqueous sodium carbonate.
Concentration of the organic layer and flash chromatography
(CHCl3/acetone, 50:50) of the residue gave (2R,4R,5S)-3n (85 mg,
0.27 mmol, 90% yield) in pure form: 1H NMR (acetone-d6) δ 0.68
(d, 3H, J H,H ) 6.6), 2.63 (d, 3H, J H,P ) 9.4), 3.71 (ddq, 1H, J H,H
C
12H27OP: C, 66.04; H, 12.46; P, 14.18. Found: C, 66.31; H,
12.52; P, 14.08.
) 6.6 and 6.5, J H,P ) 10.9), 4.17 (dd, 1H, J H,H ) 15.8, J H,P )
Triethylphosphine oxide (3a ), triphenylphosphine oxide (3c),
tri-p-tolylphosphine oxide (3d ), diethyl methylphosphonate (3e),
and diethyl (1-bromo-1,1-difluoromethylene)phosphonate (3f)
were identified through comparison of isolated products with
authentic samples from Alfa and Aldrich. Elemental selenium
formed in the oxidation of 2o was identified through its typical
mass spectrum.
13.1), 4.23 (dd, 1H, J H,H ) 15.8, J H,P ) 14.2), 5.60 (br d, 1H,
J H,H ) 6.5), 7.20-7.40 (m, 8H), 7.45 (m, 2H); 31P NMR (CDCl3)
δ 26.4; NOE experiments (acetone-d6) irradiation of NCH2
enhanced CH3-4 (0.5%) and NCH2ArHortho (1%), irradiation of
CH3-4 enhanced H-4 (4.5%), CH3-3 (1%), NCH2 (1%), CH2ArHortho
(0.5%).
O,O-Dimethyl O-(4-nitrophenyl) phosphate (3g),10a Paraoxon
(3h ),11j O,O-dimethyl O-(3-methyl-4-nitrophenyl) phosphate (3i),11j
and O,O-dimethyl O-(4-bromo-2,5-dichlorophenyl) phosphate
(3j),11j were identified through comparison of their spectral and
physical data with those reported in the literature.
O,O-Dim et h yl O-[2-(et h ylsu fin yl)et h yl] p h osp h a t e
Ack n ow led gm en t. We gratefully acknowledge the
financial support of the European Union (INTAS-93-
799-Ext) and MURST (Rome) for 60%. We thank Dr.
E. Benfenati (IRF “Mario Negri” Milano, Italy) for a
generous gift of Fenitrothion (2i) and Bromophos (2j).
1
(3k ): oil; H NMR (CDCl3) δ 1.37 (t, 3H, J H,H ) 7.5), 2.80 and
J O970572A