Epoxidation of 4,5-dialkyl-2,3-dihydro-1Н-phosphole 1-oxides

Article abstract of DOI:10.1007/s10593-018-2255-5

[Figure not available: see fulltext.] A method was developed for the synthesis of 1,5-dialkyl(cycloalkyl,phenyl)-2-phenyl-6-oxa-2-phosphabicyclo[3.1.0]hexane 2-oxides from alkynes, involving the epoxidation of unsaturated cyclic organophosphorus compounds with m-chloroperbenzoic acid. The organophosphorus compounds were obtained by a reaction sequence consisting of catalytic cycloalumination of symmetrical acetylenes with triethylaluminum in the presence of bis(cyclopentadienyl)zirconium(IV) dichloride catalyst leading to the formation of 2,3-disubstituted aluminacyclopent-2-enes and in situ reaction of the latter with dichlorophenylphosphine.

Full text of DOI:10.1007/s10593-018-2255-5

DOI 10.1007/s10593-018-2255-5
Chemistry of Heterocyclic Compounds 2018, 54(2), 205–208
SHORT COMMUNICATIONS
Epoxidation of 4,5-dialkyl-2,3-dihydro-1Н-phosphole 1-oxides
Vladimir A. D'yakonov1, Rina A. Agliullina1, Alevtina L. Makhamatkhanova1*,
Tatyana V. Tyumkina1, Usein M. Dzhemilev1
1 Institute of Petrochemistry and Catalysis, Russian Academy of Sciences,
141 Oktyabrya Ave., Ufa 450075, Russia; е-mail: ink@anrb.ru
Submitted July 28, 2017
Accepted after revision November 13, 2017
Translated from Khimiya Geterotsiklicheskikh Soedinenii,
2018, 54(2), 205–208
R
R
O
1. AlEt3, [Zr]
2. PhPCl2, H2O2
MCPBA
58–76%
R
R
R
R
P
P
O
O
Ph
Ph
A method was developed for the synthesis of 1,5-dialkyl(cycloalkyl,phenyl)-2-phenyl-6-oxa-2-phosphabicyclo[3.1.0]hexane 2-oxides
from alkynes, involving the epoxidation of unsaturated cyclic organophosphorus compounds with m-chloroperbenzoic acid. The
organophosphorus compounds were obtained by a reaction sequence consisting of catalytic cycloalumination of symmetrical acetylenes
with triethylaluminum in the presence of bis(cyclopentadienyl)zirconium(IV) dichloride catalyst leading to the formation of 2,3-di-
substituted aluminacyclopent-2-enes and in situ reaction of the latter with dichlorophenylphosphine.
Keywords: aluminacyclopentenes, 2,3-dihydrophospholes, epoxyphospholanes, heterocyclic compounds, organoaluminum compounds,
zirconocene dichloride, cycloalumination, epoxidation, metal complex catalysis.
The growing interest toward epoxidated phospholanes is
motivated by their possible applications as synthetic
intermediates for the preparation of nucleoside
phosphosugar derivatives, such as azidothymidine (AZT),1
ribavirin,2 4'-thiodideoxynucleosides,3 and aristeromycin,4
which have shown promising activity as HIV protease
inhibitors, antitumor and antibacterial drugs. Besides that,
phosphorus compounds in general tend to have pronounced
biological activity. For example, the phosphorus compound
bialophos is known as an antifungal agent,5 while
phosphonomycin, which combines phosphonate and
epoxide groups in its molecular structure, is used as a broad
spectrum antibiotic.5,6 As recently demonstrated by
Yamashita and coauthors,7 some substituted phospholanes
exhibit antitumor activity against leukemia cells.
The starting 2,3-dihydro-1H-phosphole 1-oxides were
obtained according to a published procedure.8–10 The
aluminacyclopent-2-enes
obtained
in
situ
from
disubstituted symmetrical acetylenes and AlEt3 reacted
with РhPCl2 in PhMe over 30 min, resulting in the
replacement of Al with P atoms, leading to the formation of
the respective 2,3-dihydrophospholes in 64–88% yields.
The obtained 2,3-dihydrophospholes were then converted
to 2,3-dihydro-1H-phosphole 1-oxides 1–5 in quantitative
yields by treatment with Н2О2 (Scheme 1).
The earliest studies used Na2O2 as epoxidating agent.11,12
However, the reactions of 4,5-disubstituted 2,3-dihydro-1H-
phosphole 1-oxides 1–5 with an excess of Na2O2 in ethanol
at various temperatures from 30 to 70°С did not produce
the expected epoxides even after 6 h.
Taking into account the great medicinal potential of
cyclic phosphorus compounds, the chemistry of phospho-
sugars and their analogs represents one of the most
interesting and rapidly growing fields of medicinal
chemistry, while modification of 2,3-dihydrophospholes
provides an effective tool of synthetic exploration, enabling
the preparation of practically significant cyclic organo-
phosphorus compounds (OPC) with the required structures.
During our studies aimed at the development of
preparative methods for the synthesis of cyclic OPC, we
explored the epoxidation of our obtained compounds using
the example of 4,5-disubstituted 2,3-dihydro-1H-phosphole
1-oxides in reactions with known epoxidating agents
(peroxy acids and metal peroxides).
Scheme 1
0009-3122/18/54(2)-0205©2018 Springer Science+Business Media, LLC
205

Chemistry of Heterocyclic Compounds 2018, 54(2), 205–208
The application of a more advanced epoxidating agent –
MCPBA,13 which is widely used in alkene epoxidation
reactions, was more successful. 4,5-Disubstituted 2,3-di-
hydro-1H-phosphole 1-oxides 1–5 were found to undergo
epoxidation reaction with a triple excess of MCPBA upon
refluxing in CH2Cl2 (Scheme 2).
Scheme 2
Figure 1. Fragment of 13С NMR spectrum of epoxidated
phospholane 10.
The by-products were removed by extracting the organic
layer with aqueous NaHCO3 solution. The products were
isolated as light-yellow oily liquids.
The new 1,5-dialkyl(cycloalkyl,phenyl)-2-phenyl-6-oxa-
2-phosphabicyclo[3.1.0]hexane 2-oxides were structurally
characterized by 1H, 13C, and 31P NMR spectroscopy. Thus,
13C NMR spectra of compounds 6–10 contained characte-
ristic signals in the range of 64.9–74.0 ppm instead of the
signals of sp2-hybridized carbon atoms, providing evidence
that the epoxidation reaction had indeed occurred (Fig. 1).
Besides that, the chemical shift of phosphorus atom in
31P NMR spectra of the target products was shifted upfield
by 8–12 ppm relative to the 31P NMR signal of the starting
2,3-dihydrophosphole 1-oxides (62–64 ppm). The experi-
mentally determined chemical shift values, as well as the
heteronuclear coupling constants (JPC) for the С-1 carbon
atoms (96.6–102.7 Hz) were in agreement with the pub-
lished spectral data for the structurally related 2-methyl(phe-
nyl)-6-oxa-2-phosphabicyclo[3.1.0]hexane 2-oxides.14–16
The epoxidation reaction of 2,3-dihydro-1H-phosphole
1-oxides 1–5 was found to be nonstereoselective, since the
entire series of the synthesized compounds existed as
diastereomers in 1:2 ratio. It should be noted that the
isomers of compounds 9 and 10 had different 31P NMR
chemical shifts (Fig. 2), while 2-phenyl-6-oxa-2-phospha-
bicyclo[3.1.0]hexane 2-oxide 1,5-dialkyl derivatives 6–8
had 31P NMR signals with similar chemical shifts that
merged into one signal, which was broadened due to the
interaction with protons bonded to the ring carbon atoms.
In order to correctly determine the chemical shift values in
31P NMR spectra of 2-phenyl-6-oxa-2-phosphabicyclo[3.1.0]-
hexane 2-oxide 1,5-dialkyl derivatives 6–8, the spectra
were acquired with suppression of the proton signals.
Thus, we have demonstrated that 4,5-disubstituted
2,3-dihydro-1H-phosphole 1-oxides in reactions with an
excess of m-chloroperbenzoic acid produced the respective
epoxides in 58–76% yields. The obtained compounds may
be of considerable practical interest.
Figure 2. 31Р NMR spectrum of epoxidated phospholane 10.
(COSY) and heteronuclear (1H–13C HSQC, 1H–13C
HMBC) NMR spectra were acquired according to the
standard procedures from Bruker. Mass spectrum of com-
pound 8 was recorded on a Bruker Autoflex-III MALDI
TOF/TOF instrument for samples on 2,5-dihydroxybenzoic
acid and α-cyano-4-hydroxycinnamic acid matrices in
reflective mode, with recording of positive ions. Mass
spectra (GC-MS) of the other compounds were recorded on a
Shimadzu GC-2010 instrument equipped with a GCMS-
QP2010 Ultra mass selective detector and a Supelco 5ms
capillary column (60 m × 0.25 mm × 0.25 μm); the carrier
gas was helium; injector temperature 260°С, interface
temperature 260°С, ion source temperature 200°С.
Elemental analysis was performed on a Carlo Erba 1106
elemental analyzer. Chromatographic analysis was per-
formed on a Shimadzu GC-9A gas chromatograph, using a
2000 × 2 mm column, the stationary phase consisted of
silicone SE-30 (5%) on Сhromaton N-AW-HMDS carrier
(0.125–0.160 mm), the carrier gas was helium (30 ml/min),
temperature program from 50 to 300°С at the rate of
8°С/min. Column chromatography was performed with
Acros silica gel (0.060–0.200 mm). The reactions with
organometallic compounds were accomplished under dry
argon flow. The solvents were dried and distilled
immediately prior to the use. Commercially available
Cp2ZrCl2, phosphines (Acros), and 92% AlEt3 (from
Redkinsk Experimental Factory) were used.
Experimental
Preparation of 4,5-disubstituted 2,3-dihydro-1H-
phosphole 1-oxides 1–5 (General method). A round-bottom
flask was charged sequentially with Cp2ZrCl2 (0.15 g,
0.5 mmol), alkyne (10 mmol), and AlEt3 (1.37 ml,
1Н, 13С, and 31P NMR spectra were acquired on a Bruker
Avance-400 instrument (400, 100, and 162 MHz,
respectively) in CDCl3. The two-dimensional homonuclear
206

Chemistry of Heterocyclic Compounds 2018, 54(2), 205–208
10 mmol) with stirring at 0°C under dry argon atmosphere.
1.22 (8H, m, CH2CH3**); 1.47–1.82 (10H, m, CH2CH2CH3
and 3-CH2**); 1.93–2.18 (4H, m, 3,4-CH2**); 2.23–2.46
(2H, m, 4-CH2*); 7.24–8.01 (10H, m, H Ph**). 13C NMR
spectrum, δ, ppm (J, Hz): 14.0, 14.2, 14.3 and 14.4 (CH3);
18.5, 18.8, 19.1 and 19.3 (СH2CH3); 21.2 (J = 70.7) and
23.1 (J = 69.5, C-3); 26.5 and 26.7 (CH2CH2CH3); 28.0
(J = 12.2) and 28.5 (J = 12.2, C-4); 32.8 (CH2CH2CH3);
65.1 (J = 97.0) and 65.5 (J = 101.3, C-1); 68.3 (J = 19.8)
and 70.8 (J = 14.8, C-5); 128.5 (J = 11.7) and 128.9
(J = 11.2, C-3,5 Ph); 130.0 (J = 9.4, C-2,6 Ph); 131.1
(J = 92.5, C-1 Ph); 131.3 (J = 9.2, C-2,6 Ph); 132.2 (J = 2.4)
and 132.3 (J = 2.7, C-4 Ph). 31P NMR spectrum, δ, ppm:
53.1; 53.3. Mass spectrum, m/z (Irel, %): 278 [M]+ (100).
Found, %: С 69.08; Н 8.37. C16H23O2P. Calculated, %:
С 69.05; H 8.33.
The temperature was raised to 40°С, and the mixture was
stirred for 4 h, then diluted with PhMe (20 ml), the mixture
was cooled to –5°С, treated by dropwise addition of
РhPCl2 (1.36 ml, 10 mmol), and stirred at room tempera-
ture for an additional 30 min. The reaction mixture was
treated with saturated aqueous NH4Cl solution; the reaction
products were extracted with Et2O, dried over anhydrous
MgSO4, and the solvent was removed by evaporation. The
residue was taken up in CHCl3 (10 ml), vigorously stirred, and
treated by slow addition of 30% H2O2 (0.08 ml, 10 mmol),
then stirred for a further 1 h. The reaction mixture was then
washed with water (3×10 ml), the organic layer was dried
over anhydrous MgSO4, and the solvent was removed by
evaporation. The products were separated by vacuum
distillation. The spectral characteristics of compounds 1–5
were in agreement with the literature data.8–10
1,5-Dibutyl-2-phenyl-6-oxa-2-phosphabicyclo[3.1.0]-
hexane 2-oxide (8). Yield 1.86 g (76%), yellow oil.
IR spectrum, ν, cm–1: 3056, 2960, 2932, 2872, 2606, 2482,
1708, 1466, 1437, 1264, 1173, 1151, 1110, 838, 813, 740,
Preparation of 1,5-disubstituted 2-phenyl-6-oxa-
2-phosphabicyclo[3.1.0]hexane 2-oxides 6–10 (General
method). A solution of 4,5-dialkyl(phenyl,cyclododecyl)-
2,3-dihydro-1Н-phosphole 1-oxide 1–5 (8 mmol) in
CH2Cl2 (16 ml) was treated by the addition of MCPBA
(4.14 g, 24 mmol) and refluxed for 24 h. The reaction
mixture was neutralized with aqueous NaHCO3 solution
(7 g in 35 ml of water) with vigorous stirring for 1 h. The
aqueous layer was extracted with CHCl3 and dried over
anhydrous MgSO4. The product-containing layer was
evaporated at reduced pressure on a rotary evaporator and
purified by method of column chromatography (eluent
hexane–EtOAc–MeOH, 5:3:1). All epoxides were obtained
as 1:2 mixtures of diastereomers (a single asterisk (*) in
1Н spectra denote the signal of a single isomer, while two
asterisks (**) denote the combined signals of both
isomers).
1
704, 507, 484. H NMR spectrum, δ, ppm (J, Hz): 0.59
(3H, t, 3J = 6.8, CH2CH3*); 0.72 (3H, t, 3J = 7.2,
CH2CH3*); 0.78–0.92 (6H, m, CH2CH3**); 1.00–1.37 (8H,
m, CH2CH3**); 1.40–1.55 (8H, m, CH2CH2CH3**); 1.57–
1.75 (8H, m, CH2(CH2)2CH3**); 1.80–2.18 (6H, m,
3,4-CH2**); 2.27–2.47 (2H, m, 4-CH2*); 7.35–7.96 (10H,
m, H Ph**). 13C NMR spectrum, δ, ppm (J, Hz): 13.2,
13.3, 13.5 and 13.6 (CH3); 20.6 (J = 70.9) and 22.5 (J =
69.4, C-3); 22.4, 22.5 and 22.6 (CH2CH3); 25.1 (J = 12.2)
and 25.7 (J = 11.9, C-4); 26.3, 26.9, 27.3 and 27.5
(CH2CH2CH3); 30.1 and 30.7 (CH2(CH2)2CH3); 64.9
(J = 97.2) and 65.2 (J = 102.7, C-1); 68.5 (J = 20.8) and
70.9 (J = 14.8, C-5); 128.3 (J = 11.8) and 128.8 (J = 11.3,
C-3,5 Ph); 131.1 (J = 9.3) and 132.1 (J = 11.5, C-2,6 Ph);
131.6 (J = 90.0, C-1 Ph); 132.2 and 133.9 (C-4 Ph).
31P NMR spectrum, δ, ppm: 52.9; 53.2. Mass spectrum, m/z
(Irel, %): 307.18 [M+H]+ (100). Found, %: С 70.58; Н 8.92.
C18H27O2P. Calculated, %: С 70.56; H 8.88.
1,5-Diethyl-2-phenyl-6-oxa-2-phosphabicyclo[3.1.0]-
hexane 2-oxide (6). Yield 1.38 g (69%), yellow oil.
IR spectrum, ν, cm–1: 3058, 2960, 2932, 2602, 2486, 1715,
1466, 1437, 1270, 1168, 1150, 1134, 1070, 839, 745, 706,
1,2,5-Triphenyl-6-oxa-2-phosphabicyclo[3.1.0]hexane
2-oxide (9). Yield 1.60 g (58%), yellow oil. IR spectrum,
ν, cm–1: 3056, 2960, 2927, 2853, 1768, 1713, 1648, 1603,
1567, 1394, 1265, 1200, 1160, 1113, 1072, 1026, 904, 745,
698, 544, 527, 481. 1H NMR spectrum, δ, ppm (J, Hz): 2.13–
2.38 (4H, m, 3-CH2**); 2.58–2.96 (2H, m, 4-CH2*); 3.01–
3.16 (2H, m, 4-CH2*); 6.87–8.06 (30H, m, H Ph**).
13C NMR spectrum, δ, ppm (J, Hz): 21.2 (J = 68.9) and 23.0
(J = 69.2, C-3); 28.6 and 29.4 (C-4); 67.8 (J = 100.4) and
69.4 (J = 96.8, C-1); 70.2 (J = 21.1) and 74.0 (J = 15.0,
C-5); 126.3 and 127.1 (C-4 Ph); 127.5 (С-3,5 Ph); 127.8
(J = 11.2, C-3,5 PPh); 128.2 (J = 2.4, C-4 PPh); 129.6
(J = 90.0, С-1 PPh); 131.0 (J = 9.4, C-2,6 PPh); 132.2 (С-1
Ph); 134.4 (J = 67.8, C-1 Ph). 31P NMR spectrum, δ, ppm:
50.9; 51.9. Mass spectrum, m/z (Irel, %): 346 [M]+ (100).
Found, %: С 76.34; Н 5.55. C22H19O2P. Calculated, %:
С 76.29; H 5.53.
1
505, 484. H NMR spectrum, δ, ppm (J, Hz): 0.65–1.08
(12H, m, CH2CH3**); 1.51–1.79 (10H, m, CH2CH3 and
3-СH2**); 1.94–2.21 (4H, m, 3,4-CH2**); 2.24–2.46 (2H,
m, 4-СH2*); 7.28–7.97 (10H, m, H Ph**). 13C NMR spectrum,
δ, ppm (J, Hz): 13.4, 13.5, 13.7 and 13.8 (CH3); 21.1
(J = 70.7) and 23.0 (J = 69.5, C-3); 25.4 (J = 12.2) and 26.0
(J = 12.2, C-4); 29.8 and 30.4 (СH2CH3); 65.2 (J = 96.6)
and 65.6 (J = 101.6, C-1); 68.6 (J = 20.1) and 70.9
(J = 15.1, C-5); 128.5 (J = 11.6) and 129.0 (J = 11.3, C-3,5
Ph); 129.9 (J = 10.0, C-2,6 Ph); 129.9 (J = 90.0, C-1 Ph);
131.3 (J = 9.8, C-2,6 Ph); 132.2 (J = 2.4) and 132.3 (J = 2.6,
C-4 Ph). 31P NMR spectrum, δ, ppm: 53.2; 53.5. Mass
spectrum, m/z (Irel, %): 250 [M]+ (100). Found, %: С 67.15;
H 7.66. C14H19O2P. Calculated, %: С 67.19; Н 7.65.
2-Phenyl-1,5-dipropyl-6-oxa-2-phosphabicyclo-
[3.1.0]hexane 2-oxide (7). Yield 1.64 g (74%), yellow oil.
IR spectrum, ν, cm–1: 3062, 2961, 2932, 2873, 2605, 2482,
1771, 1712, 1574, 1465, 1437, 1246, 1177, 1152, 1132,
1-Phenyldodecahydro-3а,13-epoxycyclododeca[b]-
phosphole 1-oxide (10). Yield 1.86 g (70%), yellow oil.
IR spectrum, ν, cm–1: 3056, 2929, 2860, 1764, 1469, 1438,
1258, 1195, 1183, 1111, 820, 748, 724, 541, 516, 452.
1H NMR spectrum, δ, ppm (J, Hz): 0.84–1.76 (45H, m,
1
1109, 750, 730, 705, 502, 482. H NMR spectrum, δ, ppm
3
(J, Hz): 0.67 (3H, t, J = 7.2, CH2CH3*); 0.81 (3H, t,
3J = 7.2, CH2CH3*); 0.90–1.00 (6H, m, CH2CH3**); 1.04–
207

Chemistry of Heterocyclic Compounds 2018, 54(2), 205–208
3. Secrist III, J. A.; Riggs, R. M.; Tiwari, K. N.; Montgomery, J. A.
4,5,6,7,8,9,10,11,12,13-CH2 and 2,3-CH2**); 1.99–2.55
(3H, m, 3-CH2**); 7.22–7.74 (10H, m, H Ph**). 13C NMR
spectrum, δ, ppm (J, Hz): 21.7 (J = 15.5), 21.9, 22.0, 22.1
and 22.9 (С-4,7,8); 23.0 (J = 68.6) and 23.1 (J = 53.3, C-2);
23.3, 23.5 (J = 5.6), 25.1, 25.4, 25.7, 25.9, 26.1 (J = 2.0),
26.2, 26.4, 26.8 and 27.0 (С-5,6,9,10,11,12,13); 27.4
(J = 17.2, C-3); 65.4 (J = 99.1) and 65.9 (J = 95.5, C-13a);
69.5 (J = 21.5) and 71.7 (J = 15.6, C-3a); 128.4 (J = 11.6)
and 128.7 (J = 11.3, C-3,5 Ph); 129.9 (J = 9.6, C-2,6 Ph);
130.0 (J = 92.3, C-1 Ph); 131.3 (J = 9.1, C-2,6 Ph); 132.1
(J = 2.4) and 132.2 (J = 2.6, C-4 Ph). 31P NMR spectrum,
δ, ppm: 51.3; 54.1. Mass spectrum, m/z (Irel, %): 332 [M]+
(100). Found, %: С 72.39; Н 8.84. C20H29О2P. Calculated,
%: С 72.26; H 8.79.
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Supplementary information file containing 1H, 13C, and
31P spectra of compounds 7–10 is available at the journal
website at http://link.springer.com/journal/10593.
Dilmukhametova, L. K.; Agliullina, R. A.; Tyumkina, T. V.;
Dzhemilev, U. M. Organometallics 2015, 34, 221.
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This work received financial support from the Russian
Foundation for Basic Research (project 16-33-00193) and
grant of the President of the Russian Federation (NSh-
5240.2018.3). The structural studies were performed with
the use of Collective Usage Center ''Agidel'' at the Institute
of Petrochemistry and Catalysis, Russian Academy of
Sciences.
11. Yamashita, M.; Reddy, V. K.; Rao, L. N.; Haritha, B.; Maeda, M.;
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