Synthesis of novel (3a,S)-1-aryl/aryloxy/alkoxy-3a,4-dihydro-3H-1λ5- [1,3,2]oxazaphospholo [3,4-a] indole-1-ones, thiones, and selenones

Article abstract of DOI:10.1080/00397910801914236

Synthesis of novel (3a,S)-1-aryl/aryloxy/alkoxy-3a,4-dihydro-3H-1λ5- [1,3,2]oxazaphospholo [3,4-a] indole-1-ones, thiones, and selenones was achieved in two steps with high yields from 2,3-dihydro-1H-indol-2(S)yl methanol (1) and dichlorophenyl phosphine/ethyl dichlorophosphite (2a and b) in the presence of triethylamine in dry THF followed by treatment with hydrogen peroxide, sulfur, and selenium. The compounds 4g-k have been synthesized by the direct cyclocondensation of 1 with different substituted phenyl phosphorodichloridates (2c-e, g) and bis(2-chloroethyl) phosphoramidic dichloride (2f). Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397910801914236

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Synthesis of Novel (3a,S)‐1‐Aryl/aryloxy/
alkoxy‐3a,4‐dihydro‐3H‐1λ5‐[1,3,2]oxazaphospho
[3,4‐a] indole‐1‐ones, Thiones, and
Selenones
B. Hari Babu a , G. Syam Prasad a , C. Naga Raju a & C. Suresh Reddy a
a Department of Chemistry , Sri Venkateswara University , Tirupati, India
Published online: 25 Apr 2008.
To cite this article: B. Hari Babu , G. Syam Prasad , C. Naga Raju & C. Suresh Reddy (2008) Synthesis of Novel
(3a,S)‐1‐Aryl/aryloxy/alkoxy‐3a,4‐dihydro‐3H‐1λ5‐[1,3,2]oxazaphospholo [3,4‐a] indole‐1‐ones, Thiones, and
Selenones, Synthetic Communications: An International Journal for Rapid Communication of Synthetic Organic
Chemistry, 38:9, 1398-1406, DOI: 10.1080/00397910801914236
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Synthetic Communicationsw, 38: 1398–1406, 2008
Copyright # Taylor & Francis Group, LLC
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910801914236
Synthesis of Novel (3a,S)-1-Aryl/aryloxy/
alkoxy-3a,4-dihydro-3H-1l5-
[1,3,2]oxazaphospholo [3,4-a] indole-1-ones,
Thiones, and Selenones
B. Hari Babu, G. Syam Prasad, C. Naga Raju, and
C. Suresh Reddy
Department of Chemistry, Sri Venkateswara University, Tirupati, India
Abstract: Synthesis of novel (3a,S)-1-aryl/aryloxy/alkoxy-3a,4-dihydro-3H-1l5-
[1,3,2]oxazaphospholo [3,4-a] indole-1-ones, thiones, and selenones was achieved in
two steps with high yields from 2,3-dihydro-1H-indol-2(S)yl methanol (1) and dichlor-
ophenyl phosphine/ethyl dichlorophosphite (2a and b) in the presence of triethylamine
in dry THF followed by treatment with hydrogen peroxide, sulfur, and selenium. The
compounds 4g–k have been synthesized by the direct cyclocondensation of 1 with
different substituted phenyl phosphorodichloridates (2c–e, g) and bis(2-chloroethyl)
phosphoramidic dichloride (2f).
Keywords: Dichlorophenyl phosphine, 2,3-dihydro-1H-indol-2(S)yl methanol,
2-ethyl(S)-carboxyindole
INTRODUCTION
Extensive investigation of compounds containing P-N linkages by numerous
research groups have led to many interesting and far-reaching develop-
ments.[1] Organophosphorus heterocycles bearing P-N functionality have
shown antitumor, pesticidal, and medicinal activity.[2–4] Since the ingenious
introduction of chiral catalysts containing the N-P55O structural framework
Received October 12, 2007
Address correspondence to C. Naga Raju, Department of Chemistry, Sri Venkates-
wara University, Tirupati 517 502, Andhra Pradesh, India. E-mail: naga_raju04@
yahoo.co.in
1398

Synthesis of Thiones and Selenones
1399
by Wills,[5–7] there has been an increasing interest in the development of
novel classes of chiral catalysts containing the N-P55O structural
framework. A few chiral catalysts containing the N-P55O structural
framework having the (5S)-1,3-diaza-2-phospha-2-oxo-3-phenylbicyclo
[3.3.0] octane moiety with amino groups of varying steric requirements on
phosphorus have been synthesized, and their applications in the borane-
mediated asymmetric reduction of prochiral ketones to alcohols with enantio-
mer excess have been studied.[8–10] Recently, we turned our attention to chiral
phosphoramides as part of our ongoing research program, and we have syn-
thesized the novel chiral phosphoramides, characterized by spectral data.
RESULTS AND DISCUSSION
Synthesis of novel (3a,s)-1-aryl/aryloxy/alkoxy-3a,4-dihydro-3H-1l5-
[1,3,2]oxaza phospholo[3,4-a]indole-1-ones, thiones, and selenones 4a–f was
accomplished in two steps. The synthetic route involves the cyclization of
equimolar quantities of 2,3-dihydro-1H-indole-2(S)-yl methanol (1) with
dichlorophenylphosphine/ethyldichlorophosphite 2a and b in the presence of
triethylamine in dry tetrahydrofuran at 45–50 8C. They were further
converted to the corresponding oxides, sulfides, and selenides by reacting
them with hydrogen peroxide, sulfur, and selenium respectively. Compounds
4g–k were prepared by the direct cyclocondensation of equimolar quantities
of 1 with various aryl phosphorodichloridates 2c–e, 2 g, and bis(2-chloroethyl)
phosphoramidic dichloride 2f in the presence of triethylamine in dry tetrahydro-
furan at 45–50 8C. Purification of these products 4a–k was achieved by filtering
the reaction mixture to separate the triethylamine hydrochloride, evaporating the
filtrate in a rotaevaporator under vacuum to obtain a residue, washing it with
water, and recrystallzing it from ethanol. Physical data along with IR absorp-
tions, elemental analysis, and 31P NMR of 4a–k are given in Table 1. Tables
1
2–4 contain H NMR, 13C NMR, and mass spectral data. The IR spectra
showed characteristic bands[11,12] at 1276–1228 (P55O), 807–804 (P55S),
685–684 (P55Se), 786–721 (P-Naliph), and 1172–1130 (P-Oaliph) cm21
.
The 1H NMR spectra of 4a–k (Table 2) showed[13] a doublet for H-3 at d
3.87–3.71 (J ¼ 38.2–25.3 Hz), and H-4 gave a signal at d 3.53–3.31 (J ¼ 7.3–
4.8 Hz). H-3a, which is attached to the chiral carbon resonated as a multiplet in
the range of 5.23–4.21 ppm. The 13C NMR spectra (Table 3) were recorded for
a few members of the title compounds (4b, c, j, and i). The chemical shifts for
C-4a, C-5, C-6, C-7, C-8, and C-8a appeared at 128.3–127.2, 126.8–124.6,
130.0–128.1, 124.7–120.3, 136.7–129.1, and 142.6–136.2 respectively. The
oxygen-bearing C-3 resonated[8] at 58.3–53.6 ppm as
a
doublet
(2JPOC ¼ 5.2 Hz). The carbons of C-10, C-(20,60), C-(30,50), and C-40 of 4b
and 4c gave chemical shifts at d 130.4–130.2, 132.9–132.7, 127.8–127.6,
and 131.8–131.7 respectively. The carbon chemical shifts of the phenoxy
group in 4g and 4i were observed in the expected range.[13]

Table 1. Physical, IR, and 31P NMR spectral data of 4a–k
Elemental analysis found (Calcd.) (%)
IR (cm21
P55O/S/Se P-Naliph P-Oaliph 31P NMRb,c
)
Compd. Molecular formula Mp (8C) Yielda
C
H
N
4a
4b
4c
4d
4e
4f
C15H14NO2P
113–115
135–137
152–154
103–105
117–119
130–132
119–121
123–125
109–111
121–123
128–130
62
68
63
58
67
61
67
63
65
63
60
66.36 (66.42) 5.09 (5.16) 5.13 (5.16)
62.62 (62.71) 4.83 (4.87) 4.81 (4.87)
53.80 (53.89) 4.13 (4.19) 4.10 (4.19)
55.19 (55.23) 5.79 (5.85) 5.82 (5.85)
51.70 (51.76) 5.46 (5.49) 5.43 (5.49)
46.11 (46.15) 4.84 (4.89) 4.85 (4.89)
62.63 (62.71) 4.82 (4.87) 4.84 (4.87)
55.92 (55.98) 4.01 (4.04) 4.30 (4.35)
54.15 (54.21) 3.86 (3.91) 8.38 (8.43)
46.50 (46.56) 5.02 (5.07) 8.31 (8.35)
49.11 (49.18) 3.59 (3.55) 3.79 (3.82)
1262
804
721
778
751
786
762
768
754
753
768
774
758
1161
1168
1163
1186
1172
1168
1169
1168
1138
1130
1165
15.50
16.92
19.52
2.45
5.13
6.49
3.82
3.27
5.02
5.12
3.51
C15H14NOPS
C15H14NOPSe
C11H14NO3P
685
1228
807
C11H14NO2PS
C11H14NO2PSe
C15H14NO3P
684
4g
4h
4i
1272
1276
1276
1262
1271
C15H13NO3PCl
C15H13N2O5P
C13H17N2O2PCl2
C15H13NO3PBr
4j
4k
aRecrystallized from ethanol.
bRecorded in CDCl3.
cChemical shifts in ppm from 85% phosphoric acid.

Synthesis of Thiones and Selenones
1401
Table 2. 1H NMR spectral dataa,b of 4a–k
-CH2-
(4)
Compd.
-OCH2-
-CH-(3a)
Ar-H
R
4a
3.76
(d, 34.3, 2H)
3.73
5.16–4.92
(m)
3.46
(d, 6.5)
3.47
7.76–6.86
(m, 9H)
4b
4c
4d
4e
4f
5.23–4.95
(m)
7.87–7.09
(m, 9H)
(d, 31.7, 2H)
3.71
(d, 7.3)
3.53
5.18–4.91
(m)
7.08–6.86
(m, 9H)
(d, 33.9, 2H)
3.87
(d, 6.2)
3.32
5.16–4.94
(m)
7.78–7.62 4.13 (q, 2H, OCH2)
(m, 4H) 1.29 (t, 3H, CH3)
7.78–7.62 4.11 (q, 2H, OCH2)
(m, 4H) 1.29 (t, 3H, CH3)
7.25–7.02 4.11 (q, 2H, OCH2)
(d, 25.4, 2H)
3.87
(d, 5.1)
3.35
5.19–4.96
(m)
(d, 25.3, 2H)
3.86
(d, 4.8)
3.31
5.23–4.91
(m)
(d, 35.2, 2H)
3.87
(d, 5.3)
3.32
(m, 4H)
7.25–6.38
(m, 9H)
1.28 (t, 3H, CH3)
4g
4h
4i
5.17–4.96
(m)
(d, 36.1, 2H)
3.82
(d, 7.0)
3.35
5.11–4.93
(m)
7.51–7.23
(m, 8H)
(d, 25.3, 2H)
3.71
(d, 6.3)
3.32
5.19–4.83
(m)
7.69–7.02
(m, 8H)
7.44–7.11 3.65–3.41 (m, 4H,
(d, 38.2, 2H)
3.87
(d, 31.5, 2H)
(d, 5.1)
3.31
(d, 7.3)
4j
4.49–4.21
(m)
(m, 4H)
CH2Cl) 3.77-3.74
(m, 4H, -N-CH2)
4k
3.79
(d, 27.2, 2H)
4.82–4.27
(m)
3.30
(d, 5.9)
7.53–7.27
(m, 8H)
aRecorded in CDCl3.
bChemical shifts in ppm.
The 31P NMR chemical shifts of the compounds 4d–k appeared in the
range of 6.49–2.45 ppm. Other members 4a–c gave 31P NMR chemical
shifts in the expected[14] range depending on elements present at the phos-
phorus atom (i.e. P55O, P55S, and P55Se). Mass spectral analysis was made
for four compounds (Table 4), and the data confirmed the structures of the
title compounds (4c, 4e, 4i, and 4j).
EXPERIMENTAL
The melting points were determined on a Mel-temp apparatus and are uncor-
rected. Elemental analyses were performed by the Central Drug Research
Institute, Lucknow, India. All IR spectra were recorded as KBr pellets on a
1
Perkin-Elmer 1430 unit; H, 13C, and 31P NMR spectra were recorded on an
1
AM 400- MHz spectrometer, operating at 400 MHz for H, 100 MHz for

Table 3. 13C NMR chemical shiftsa,b of some members of 4a–k
Compd. -CH2 (3) -CH (3a) -CH2 (4)
C-4a
C-5
C-6
C-7
C-8
C-8a
C10
C20 and C60 C30 and C50
C40
4b
4c
4g
4i
58.2
57.1
58.3
53.6
45.8
46.3
46.1
45.8
31.2
31.1
32.3
35.3
127.7
127.6
127.2
127.6
124.6
125.2
125.0
125.2
128.3
128.1
128.5
128.5
120.3
124.7
121.7
123.6
129.6
129.1
129.3
128.6
138.5
136.2
138.4
137.1
132.9
132.7
148.2
154.9
130.4
130.2
130.8
120.6
127.8
127.6
127.3
125.9
131.8
131.7
131.5
144.3
aChemical shifts in ppm.
bRecorded in CDCl3.

Synthesis of Thiones and Selenones
1403
Table 4. Mass spectral data of 4c, 4e, 4i, and 4j
Compd.
m/z (Relative abundance)
4c
335 (Mþ þ1, 32), 334 (Mþ†, 18), 327 (9), 315 (13), 304 (7), 285 (6), 257
(17), 250 (14), 235 (28), 213 (78), 185 (22), 138 (100).
4e
4i
256 (Mþ þ 1, 28), 255 (Mþ†, 11), 241 (23), 237 (12), 212 (21), 203 (34), 197
(21), 183 (12), 177 (18), 152 (34), 138 (100).
333 (Mþ þ1, 24), 332 (Mþ†, 16), 323 (3), 314 (3), 298 (5), 288 (4), 272 (8),
264 (7), 251 (12), 239 (6), 235 (12), 229 (56), 219 (9), 213 (14), 203 (8),
187 (6), 181 (9), 175 (22), 165 (9), 159 (100), 155 (12), 143 (9).
339 (Mþ þ4, 35), 337 (Mþ þ 2, 28), 335 (Mþ†, 11), 322 (5), 307 (2), 284
(16), 265 (4), 241 (3), 228 (8), 211 (5), 207 (8), 191 (4), 177 (84), 161 (57),
149 (41), 127 (36), 121 (23), 105 (15), 91 (12), 77 (13), 57 (31), 44 (100).
4j
13C, and 161.9 MHz for 31P as solutions in CDCl3. The chemical shifts were
referenced to TMS (1H and 13C) and 85% H3PO4 (31P) (Scheme 1).
Preparation of (2S)-2,3-Dihydro-1H-2-indolylmethanol (1)
To a stirred and ice-cold suspension of LiAlH4 (3.10 g, 0.0817 mol) in dry THF
(100 mL), a solution of 2-ethyl(S)-carboxyindole (7.60 g, 0.039 mol) in dry THF
(35 mL) was added dropwise. The mixture was stirred and refluxed for 3 h and
then cooled, and the excess of LiAlH4 was decomposed by the addition of a
mixture of water (6.2 mL) and THF (50 mL). After stirring at room temperature
for 1 h, the inorganic salts were filtered off and washed with hot EtOAc
(3 ꢀ 50 mL). The combined organic filtrate and washings were dried
(Na2SO4) and evaporated under reduced pressure to give the crude amino
alcohol[14] as a crystalline product, which was filtered off, washed with Et2O,
and recrystallized from EtOAc. Yield: 4.03 g (68%), mp 127 8C.
Preparation of (3a,S)-1-Phenyl-3a,4-dihydro-3H-1l5-
[1,3,2]oxazaphospholo[3,4-a]indol-1-one (4a)
To a cooled (0 8C) and stirred solution of 2,3-dihydro-1H-indole-2(S)yl
methanol (1, 0.74 g, 0.005 mol) and triethylamine (1.01 g, 0.01 mol) in 25 mL
of dry tetrahydrofuran under nitrogen gas, a solution of dichlorophenylphosphine
(2a, 0.895 g, 0.005 mol) in 10 mL of dry tetrahydrofuran was added over a period
of 20 min. After completion of the addition, the temperature of the reaction

1404
B. H. Babu et al.
Scheme 1.
mixture was raised to 45–50 8C and stirred for 1 h to form the intermediate,
1-phenyl-3a(S),4-dihydro-3H-[1,3,2] oxazaphosphino[3,4-a]indole (3a). The
progress of the reaction was judged by the thin-layer chromatography (TLC)
of the reaction mixture. After completion of the reaction, it was filtered under
nitrogen atmosphere. Triethylamine hydrochloride and the solvent were
removed, from the filtrate in a rota-evaporator. The crude product 3a obtained
was dissolved in dichloromethane (30 mL), and hydrogen peroxide (30%
H2O2, 0.2 mL, 0.005 mol) was added to it dropwise at 0–5 8C. The reaction
mixture was brought to 45–508C and kept with stirring for 2 h for the completion
of oxidation as indicated by TLC analyses. The solvent was evaporated from the
filtrate in a rota-evaporator. The resulting crude product was recrystallized from
ethanol to yield 0.83 g (62%) of 4a, mp 113–115 8C.
Preparation of (3a,S)-1-(4-Nitrophenoxy)-3a,4-dihydro-3H-1l5-
[1,3,2]oxazaphospholo[3,4-a]indol-1-one (4i)
A solution of 4-nitrophenyl phosphorodichloridate (2e, 1.2 g, 0.005 mol) in
20 mL of dry tetrahydrofuran was added over a period of 20 min at 0 8C to

Synthesis of Thiones and Selenones
1405
a stirred solution of 2,3-dihydro-1H-indol-2(S)yl methanol (1, 0.745 g, 0.005
mol) and triethylamine (1.01 g, 0.01 mol) in 50 mL of dry tetrahydrofuran.
After completion of the addition, the temperature of the reaction mixture
was raised to 45–50 8C and kept for 3–4 h with stirring. The progress of
the reaction mixture was monitored by TLC analyses. The precipitated tri-
ethylamine hydrochloride was filtered, and the filtrate, was evaporated in a
rota-evaporator. The residue obtained was washed with water followed by
chilled ethanol. Colorless crystals were obtained after recrystallization of
the product from ethanol to yield 1.30 g (65%) of 4i, mp 109–111 8C.
ACKNOWLEDGMENTS
The authors express thanks to Prof. C. Devendranath Reddy, Sri Venkateswara
University, Tirupati, for his encouragement and helpful discussions and the
director of Central Drug Research Institute (CDRI), Lucknow and Sophisti-
cated Instrumentation Facility (SIF), Indian Institute of Science (IISc),
Bangalore for the elemental analyses and spectral data.
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