Alkylation of Pyrrolidine-2,5-dione with 2-(3,4-Dihydro-1-napthalenyl)ethyl-4-methylphenylsulphonates: A New and General Approach to 13-Azaequilenin Analogs

Article abstract of DOI:10.1081/SCC-120027232

Pyrrolidine-2,5-dione was N-alkylated with three different 2-(3,4-dihydro-1-napthalenyl)ethyl-4-methylphenylsulphonates to give the corresponding seco-azasteroids which on chemoselective dehydrogenation, reduction with NaBH₄ in MeOH at 0°C gave the corresponding 5-hydroxy-2-pyrrolidones. Intramolecular cyclization of these 5-hydroxy-2-pyrrolidones afforded the corresponding title compounds.

Full text of DOI:10.1081/SCC-120027232

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Alkylation of Pyrrolidine‐2,5‐dione with
2‐(3,4‐Dihydro‐1‐napthalenyl)ethyl‐4‐methylphenylsulph
A New and General Approach to 13‐Azaequilenin
Analogs
J. A. Parihar a & M. M. V. Ramana a
a Department of Chemistry, University of Mumbai, Vidyanagari, Santacruz (E), Mumbai,
400098, India
Published online: 16 Aug 2006.
To cite this article: J. A. Parihar & M. M. V. Ramana (2004) Alkylation of Pyrrolidine‐2,5‐dione with
2‐(3,4‐Dihydro‐1‐napthalenyl)ethyl‐4‐methylphenylsulphonates: A New and General Approach to 13‐Azaequilenin Analogs,
Synthetic Communications: An International Journal for Rapid Communication of Synthetic Organic Chemistry, 34:1,
11-18, DOI: 10.1081/SCC-120027232
To link to this article: http://dx.doi.org/10.1081/SCC-120027232
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SYNTHETIC COMMUNICATIONSw
Vol. 34, No. 1, pp. 11–18, 2004
Alkylation of Pyrrolidine-2,5-dione with
2-(3,4-Dihydro-1-napthalenyl)ethyl-4-
methylphenylsulphonates: A New and
General Approach to 13-Azaequilenin
Analogs
*
J. A. Parihar and M. M. V. Ramana
Department of Chemistry, University of Mumbai, Mumbai, India
ABSTRACT
Pyrrolidine-2,5-dione was N-alkylated with three different 2-(3,4-
dihydro-1-napthalenyl)ethyl-4-methylphenylsulphonates to give the
corresponding seco-azasteroids which on chemoselective dehydrogena-
tion, reduction with NaBH4 in MeOH at 08C gave the corresponding
5-hydroxy-2-pyrrolidones. Intramolecular cyclization of these 5-
hydroxy-2-pyrrolidones afforded the corresponding title compounds.
Key Words: N-Alkylation; Chemoselective dehydrogenation; Imide
reduction; Intramolecular cyclization; 13-Azasteroids.
*
Correspondence: M. M. V. Ramana, Department of Chemistry, University of
Mumbai, Vidyanagari, Santacruz (E), Mumbai 400098, India; E-mail: mmvramana@
chem.mu.ac.in.
11
DOI: 10.1081/SCC-120027232
0039-7911 (Print); 1532-2432 (Online)
www.dekker.com
Copyright # 2004 by Marcel Dekker, Inc.

12
Parihar and Ramana
Several azasteroids[1–7] have been synthesized due to their potential
biological properties such as analgesic,[2] antiandrogenic,[8] antiphlo-
gistic,[9,10] antimicrobial,[11,12] antileukemia,[13,14] antifungal,[15,16] bacter-
icides,[17,18] antiestrogenic,[19] antifertility,[20] and cardiotonic and
hypotensive activity.[21,22] These observations and our interest in the synthesis
of azasteroids led us to investigate a new synthesis of the title compounds.
More recently, we have reported a fruitful preparation of 2-(3,4-dihydro-
1-napthalenyl)ethyl-4-methylphenylsulphonates[23] from the corresponding
alcohols and 4-methylphenylsulphonyl chloride in presence of pyridine in
CHCl3. In our investigation of a new synthesis of the title compounds, we
N-alkylated pyrrolidine-2,5-dione 1 with 2a–c using K2CO3 in dry DMF
under reflux for 45 min to afford the corresponding seco-azasteroids 3a–c. It is
noteworthy that earlier 3a has been synthesized by Schleigh et al.[1] using K
salt of 1 in MeOH in 42 h. 3a–c were then heated with 5% Pd-C at 2508C to
give the corresponding dehydrogenated seco-azasteroids 4a–c for the first
time. It is noteworthy that only carbocyclic ring was dehydrogenated
chemoselectively to afford 4a–c. The structures of 4a–c were ascertained
from their elemental and spectroscopic data. The MS spectrum of 4a showed
its molecular ion peak and PMR spectrum displayed 4H singlet at 2.66 d, one
2H triplet at 3.33 d and one 2H triplet at 3.87 d in the aliphatic region. 4a–c
were then reduced selectively at one of the carbonyl group with NaBH4 in dry
Scheme 1. Reagents and conditions: 1) K3CO3, dry DMF, reflux, 45 min. 2) 5% Pd-C,
2508C, 15 min, 3) NaBH4, dry MeOH, 08C, N2, 4) POCl3, 508C, 8 h.

Pyrrolidine-2,5-dione
Table 1. Synthesis of 13-azaequilenin analogs.
13
Compound
R1
H
R2
H
mpa (8C)
Yieldb (%)
78
3a
88
(lit[1] mp : 88–89)
104
3b
3c
4a
CH3
CH3
H
H
CH3
H
76
78
72
180
89
(Lit[1] mp : 88–90)
4b
4c
5a
CH3
CH3
H
H
CH3
H
108
159
70
69
60
113
(Lit[25] mp : 113–115)
72
5b
5c
6a
CH3
CH3
H
H
CH3
H
60
52
65
80
126
(Lit[7] mp : 126–128)
6b
6c
CH3
CH3
H
CH3
102
128
59
67
aMelting points are uncorrected.
bYield refers to purified product.
MeOH[24] at 08C under N2 to give the corresponding 5-hydroxy-2-pyrroli-
dones 5a–c which were then subjected to intramolecular cyclization in POCl3
at 508C under N2 for 8 h to afford the corresponding title compounds 6a–c
(Sch. 1, Table 1). The structures of 6a–c were ascertained from their elemental
and spectroscopic data. The MS spectrum of 6a showed its molecular ion peak
at m/z ¼ 237 and base peak at m/z ¼ 236 (Mþ 2 1) for the loss of H radical
and PMR spectral data was consistent with the reported data.[7]
In conclusion, the present work describes a new synthesis of the title
compounds 6a–c starting from 4-methylphenylsulphonates 2a–c which
involves N-alkylation of 1 with 2a–c, chemoselective dehydrogenation of
3a–c, selective reduction of 4a–c and then finally intramolecular cyclization
of 5a–c in POCl3. Thus the method is short, general and utilizes easily
accessible materials.
EXPERIMENTAL
1. General Procedure for the Synthesis of
Seco-azasteroids (3)
A mixture of 4-methylphenylsulphonate 2a–c (2 mmole), pyrrolidine-
2,5-dione 1 (294 mg, 3 mmole), anhyd. K2CO3 (1 g, 7.25 mmole) and dry

14
Parihar and Ramana
DMF (20 cm3) was refluxed with stirring for 45 min. The reaction mixture was
diluted with water and extracted with EtOAc (4 Â 50 cm3). The combined
EtOAc extracts were washed with water (3 Â 50 cm3) and then dried
(anhydrous Na2SO4). Evaporation of the solvent gave a brown residue which
was purified by column chromatography [alumina (neutral), CHCl3 : MeOH
(99.50 : 0.50)] to afford the corresponding seco-azasteroid 3a–c.
1-[2-(3,4-Dihydro-1-naphthalenyl)ethyl]pyrrolidine-2,5-dione (3a).
IR (KBr): 1700, 1780 (C55O str.) cm21 1H-NMR (CDCl3, 60 MHz):
;
d ¼ 2.0–3.0 (10H, m), 3.66 (2H, t, J ¼ 7 Hz, CH2–N), 5.83 (1H, t, J ¼ 5 Hz,
C55C–H), 7.0–7.5 (4H, m, Ar–H); MS: m/z ¼ 255 (Mþ, 34%), 156 (100),
155 (95), 141 (95), 127 (95), 126 (73), 128 (69), 115 (52); UV (CHCl3): lmax
,
nm (log 1) ¼ 261 (3.92); Anal. Calcd for C16H17NO2: C, 75.27; H, 6.71; N,
5.49. Found: C, 75.38; H, 6.67; N, 5.54.
1-[2-(3,4-Dihydro-7-methyl-1-naphthalenyl)ethyl]pyrrolidine-2,5-
dione (3b). IR (KBr): 1700, 1775 (C55O str.) cm21 1H-NMR (CDCl3,
;
60 MHz): d ¼ 2.0–2.93 (13H, m); 3.66 (2H, t, J ¼ 7 Hz, CH2–N); 5.79 (1H, t,
J ¼ 5 Hz, C55C–H); 6.8–7.36 (3H, m, Ar–H); MS: m/z ¼ 269 (Mþ, 41%),
170 (76), 155 (88), 143 (100), 142 (44), 141 (44), 127 (44), 115 (23); UV
(CHCl3): lmax, nm (log 1) ¼ 262 (3.93); Anal. Calcd for C17H19NO2: C,
75.81; H, 7.11; N, 5.20. Found: C, 75.73; H, 7.08; N, 5.24.
1-[2-(3,4-Dihydro-6,7-dimethyl-1-naphthalenyl)ethyl]pyrrolidine-
1
2,5-dione (3c). IR (KBr): 1705, 1775 (C55O str.) cm21; H-NMR (CDCl3,
60 MHz): d ¼ 2.0–3.0 (16H, m); 3.66 (2H, t, J ¼ 7 Hz, CH2–N); 5.76 (1H, t,
J ¼ 5 Hz, C55C–H); 6.93 (1H, s, Ar–H); 7.16 (1H, s, Ar–H); MS: m/z ¼ 283
(Mþ, 54%), 184 (54), 182 (41), 169 (78), 157 (100), 141 (34), 127 (20), 115
(14); UV (CHCl3): lmax, nm (log 1) ¼ 266 (3.94); Anal. Calcd for
C18H19NO2: C, 76.30; H, 7.47; N, 4.94. Found: C, 76.42; H, 7.41; N, 4.80.
2. General Procedure for the Synthesis of Dehydrogenated
Seco-azasteroids (4a–c)
Seco-azasteroid 3a–c (200 mg) was heated with 5% Pd–C (100 mg) at
2508C for 15 min. It was extracted with hot EtOAc (4 Â 50 cm3). The
combined EtOAc extracts were filtered to remove the traces of catalyst.
Evaporation of the solvent gave a brown residue which was purified by
column chromatography [silica gel, CHCl3 : MeOH (99.5 : 0.5)] to furnish the
corresponding dehydrogenated compound 4a–c.
1-[2-(1-Naphthalenyl)ethyl]pyrrolidine-2,5-dione (4a). 1H-NMR
(CDCl3, 500 MHz): d ¼ 2.66 (4H, s, CO–CH2CH2–CO), 3.33 (2H, t,
J ¼ 7.8 Hz, Ar–CH), 3.87 (2H, t, J ¼ 7.8 Hz, N–CH), 7.38–7.76 (5H, m, H3-
7 of naphthalene ring), 7.86 (1H, d, J ¼ 8.0 Hz, H2 of naphthalene ring), 8.22

Pyrrolidine-2,5-dione
15
(1H, d, J ¼ 8.3 Hz, H8 of naphthalene ring); MS: m/z ¼ 253 (Mþ, 24%), 155
(15), 154 (100), 153 (45), 152 (12), 141 (47), 139 (10), 115 (33); UV (CHCl3):
l
max, nm (log 1) ¼ 271 (3.68); 283 (3.78); 291 (3.60); Anal. Calcd for
C16H15NO2: C, 75.87; H, 5.97; N, 5.53. Found: C, 75.77; H, 6.01; N, 5.51.
1-[2-(7-Methyl-1-naphthalenyl)ethyl]pyrrolidine-2,5-dione (4b). IR
(KBr): 1700,1770 (C55O str.) cm21; H-NMR (CDCl3, 60 MHz): d ¼ 2.0–
1
2.8 (7H, m), 3.25 (2H, t, J ¼ 8 Hz, Ar–CH2), 3.9 (2H, t, J ¼ 8 Hz, N–CH2),
7.0–8.25 (6H, m, Ar–H); UV (CHCl3): lmax, nm (log 1) ¼ 271 (3.79), 283
(3.87), 291 (3.70); Anal. Calcd for C17H17NO2: C, 76.38; H, 6.41; N, 5.24.
Found: C, 76.48; H, 6.44; N, 5.30.
1-[2-(6,7-Dimethyl-1-naphthalenyl)ethyl]pyrrolidine-2,5-dione (4c).
IR (KBr): 1700, 1770 (C55O str.) cm21 1H-NMR (CDCl3, 60 MHz):
;
d ¼ 2.0–2.8 (10H, m), 3.33 (2H, t, J ¼ 8 Hz, Ar–CH2), 3.9 (2H, t, J ¼ 8 Hz,
N–CH2), 7.0-8.1 (5H, m, Ar–H); MS: m/z ¼ 281 (Mþ, 34%), 183 (14), 182
(100), 170 (10), 169 (73), 168 (15), 167 (97), 165 (17), 154 (13), 153 (27), 152
(26), 128 (8); UV (CHCl3): lmax, nm (log 1) ¼ 272 (3.84), 280 (3.92), 292
(3.68); Anal. Calcd for C18H19NO2: C, 76.84; H, 6.81; N, 4.98. Found: C,
76.79; H, 6.78; N, 4.95.
3. General Procedure for the Synthesis of Hydroxy
Lactams (5a–c)
To a well-stirred mixture of dehydrogenated product 4a–c (1 mmole) in
dry MeOH (50 cm3) under N2 was added NaBH4 (76 mg, 2 mmole) in dry
MeOH (20 cm3) at 08C during a period of 15 min. The mixture was stirred at
the same temperature for additional 2 h. MeOH was removed under vacuum at
R.T. and the residue was quenched with 5% NH4Cl solution (100 cm3). It was
extracted with CHCl3 (3 Â 25 cm3). The combined CHCl3 extracts were
washed with water (2 Â 25 cm3) and then dried (anhyd. Na2SO4). Evaporation
of solvent gave a brown residue which was purified by column
chromatography [alumina (basic), CHCl3 : MeOH (98 : 2)] to furnish the
corresponding hydroxy lactam 5a–c.
1-[2-(1-Naphthalenyl)ethyl]-5-hydroxy-2-pyrrolidone (5a). IR (oil
film): 1680 (C55O str.), 3350 (O–H str.); 1H-NMR (CDCl3, 200 MHz):
d ¼ 2.23–2.81 (7H, m, Haliphatic and 1 OH), 3.33 (1H, m, N–CH), 3.65 (1H,
m, N-CH), 5.14 (1H, t, J ¼ 5.2 Hz, N–CH–O), 7.00–7.28 (7H, m, Ar–H);
UV (CHCl3): lmax, nm (log 1) ¼ 269 (3.67); 284 (3.89); 295 (3.61); Anal.
Calcd for C17H19NO2: C, 75.27; H, 6.71; N, 5.40. Found: C, 75.19; H, 6.77;
N, 5.45.
1-[2-(7-Methyl-1-naphthalenyl)ethyl]-5-hydroxy-2-pyrrolidone (5b).
IR (oil film): 1685 (C55O str.), 3400 (O–H str.); 1H-NMR (CDCl3, 200 MHz):

16
Parihar and Ramana
d ¼ 2.23–2.77 (10H, m, Haliphatic and 1 OH), 3.38 (1H, m, N–CH), 3.63 (1H,
m, N–CH), 5.11 (1H, t, J ¼ 5.2 Hz, N–CH–O), 6.97–7.22 (6H, m, Ar–H);
UV (CHCl3): lmax, nm (log 1) ¼ 271 (3.73); 282 (3.84); 290 (3.66); Anal.
Calcd for C17H19NO2: C, 75.81; H, 7.11; N, 5.20. Found: C, 75.69; H, 7.14;
N, 5.15.
1-[2-(6,7-Dimethyl-1-naphthalenyl)ethyl]-5-hydroxy-2-pyrrolidone
(5c). IR (oil film): 1685 (C55O str.), 3350 (O–H str.) cm21 1H–NMR
;
(CDCl3, 200 MHz): d ¼ 2.23–2.93 (13H, m, Haliphatic and 1 OH), 3.36 (1H, m,
N–CH), 3.66 (1H, m, N–CH), 5.26 (1H, t, J ¼ 5.2 Hz, N–CH–O), 6.84–7.25
(5H, m, Ar–H); UV (CHCl3): lmax, nm (log 1) ¼ 272 (3.84), 281 (3.90), 291
(3.72); Anal. Calcd for C18H21NO2: C, 76.30; H, 7.47; N, 4.94. Found: C,
76.42; H, 7.42; N, 4.99.
4. General Procedure for the Synthesis of
Title Compounds (6)
A mixture of hydroxy lactam 5a–c (50 mg) and POCl3 (8 g) was allowed
to stand under N2 at 508C for 8 h. The reaction mixture was poured onto ice
and allowed to stand overnight. It was extracted with CHCl3 (3 Â 25 cm3).
The combined CHCl3 extracts were washed with 10% Na2CO3 (2 Â 25 cm3),
water (2 Â 25 cm3) and then dried (anhyd. Na2SO4). Evaporation of solvent
gave a brown residue which was purified by column chromatography [alumina
(basic), CHCl3 : MeOH (99.5 : 0.5)] to afford the corresponding title
compound 6a–c.
5,6,10,10a-Tetrahydrobenzo[f]pyrrolo[2,1-a]isoquinolin-8[9H]-one
(6a). IR (KBr): 1680 (C55O str.) cm21; MS: m/z ¼ 237 (Mþ, 63%), 236
(Mþ 2 1, 100), 181 (10), 180 (24), 165 (11), 153 (73), 152 (15); UV (CHCl3):
l
max, nm (log 1) ¼ 272 (3.83), 281 (3.86), 293 (3.71); Anal. Calcd for
C17H17NO: C, 81.24; H, 6.82; N, 5.57. Found: C, 81.36; H, 6.80; N, 5.61.
5,6,10,10a-Tetrahydro-3-methylbenzo[f]pyrrolo[2,1-a]isoquinolin-
;
8[9H]-one (6b). IR (KBr): 1685 (C55O str.) cm21 1H-NMR (CDCl3,
200 MHz): d ¼ 2.51 (3H, s, CH3), 3.01–3.52 (7H, m), 4.01 (1H, m, H10a),
4.31 (1H, m, H6), 7.21–7.81 (5H, m, Ar–H); UV (CHCl3): lmax, nm
(log 1) ¼ 271 (3.78), 281 (3.89), 291 (3.69); Anal. Calcd for C17H17NO: C,
81.24; H, 6.82; N, 5.57. Found: C, 81.36; H, 6.80; N, 5.61.
5,6,10,10a-Tetrahydro-2,3-dimethylbenzo[f]pyrrolo[2,1-a]iso-
quinolin-8[9H]-one (6c). IR (KBr): 1680 (C55O str.) cm21 1H-NMR
;
(CDCl3, 200 MHz): d ¼ 2.50 (3H, s, CH3), 2.52 (3H, s, CH3), 3.09–3.65 (7H,
m), 4.03 (1H, m, H10a), 4.38 (1H, m, H6), 7.08–7.60 (4H, m, Ar–H); UV
(CHCl3): lmax, nm (log 1) ¼ 272 (3.84), 281 (3.90), 293 (3.71); Anal. Calcd
for C18H19NO: C, 81.47; H, 7.22; N, 5.28. Found: C, 81.39; H, 7.28; N, 5.24.

Pyrrolidine-2,5-dione
17
ACKNOWLEDGMENT
One of the authors (JAP) is thankful to UGC, New Delhi, for financial
assistance.
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Received in the USA July 22, 2003