1860 J . Org. Chem., Vol. 63, No. 6, 1998
Wang et al.
oxyphenyl)-4-propylhexanoate (43 mg, 82%): Rf ) 0.46 (pe-
19.17, 30.95, 33.35, 34.12, 36.21, 49.60, 52.47, 62.78, 123.75,
129.21, 146.48, 149.25, 169.43, 212.26; IR 2960, 1755, 1720,
1340 cm-1; MS (m/z, relative intensity) 305 (M+, 2), 274 (5),
156 (100), 136 (7), 124 (92), 96 (12); HRMS calcd for C16H19NO5
305.1263, found 305.1262. Methyl 2-oxo-5-(4-nitrophenyl)-3-
propylcyclopentanecarboxylate (4a ): Rf ) 0.51 (petroleum
ether/EtOAc ) 3:1); 1H NMR δ 0.95 (t, J ) 7.2 Hz, 3H), 1.35-
1.47 (m, 3H), 1.69 (q, J ) 12.2 Hz, 1H), 1.83-1.94 (m, 1H),
2.45-2.55 (m, 1H), 2.58-2.67 (m, 1H), 3.34 (d, J ) 12.0 Hz,
1H), 3.74 (s, 3H), 3.87 (dt, J ) 6.0, 12.2 Hz, 1H), 7.45 (d, J )
8.4 Hz, 2H), 8.20 (d, J ) 8.4 Hz, 2H); 13C NMR δ 13.89, 20.50,
31.62, 35.17, 43.64, 50.02, 52.76, 61.83, 124.07, 127.86, 147.09,
1
troleum ether/EtOAc ) 4:1); H NMR δ 0.86 (t, J ) 7.2 Hz,
enol form 25%), 0.88 (t, J ) 7.2 Hz, keto form 75%), 1.24-
1.30 (m, 2H), 1.45-1.50 (m, 1H), 1.55-1.72 (m, 2H), 1.82-
2.20 (m, 1H), 2.45-2.58 (m, 3H), 3.41 (d, J ) 15.5 Hz, 1H,
keto form), 3.46 (d, J ) 15.5 Hz, 1H, keto form), 3.71 (s, enol
form), 3.75 (s, enol form), 3.75 (s, keto form), 5.00 (s, enol form),
6.80 (d, J ) 8.4 Hz, enol form), 6.81 (d, J ) 8.4 Hz, keto form),
7.06 (d, J ) 8.4 Hz, 2H), 12.10 (s, enol form); 13C NMR, keto
form: δ 14.13, 20.34, 32.45, 32.91, 33.39, 48.10, 51.64, 52.21,
55.17, 113.83, 129.25, 133.50, 157.92, 167.59, 206.07; enol
form: δ 14.02, 20.46, 32.60, 34.68, 35.03, 44.99, 51.06, 55.17,
89.70, 113.72, 129.25, 133.99, 157.77, 173.04, 181.03. IR 2960,
1755, 1620, 1518, 1445, 1245 cm-1; MS (m/z, relative intensity)
292 (M+, 22), 219 (20), 158 (31), 135 (88), 121 (100), 91 (37),
78 (44); HRMS calcd for C17H24O4, 292.1675, found 292.1673.
Diazo transfer procedure as for the synthesis of 1a was
followed (442 mg, 1.5 mmol). The crude product was subjected
to column chromatography, eluting with 15:1 petroleum ether/
EtOAc to give 1f as a yellow oil (385 mg, 80%): Rf ) 0.3
(petroleum ether ) 10:1); 1H NMR δ 0.88 (t, J ) 7.2 Hz, 3H),
1.26-1.34 (m, 2H), 1.36-1.47 (m, 1H), 1.63-1.75 (m, 2H),
1.95-2.07 (m, 1H), 2.50-2.55 (m, 2H), 3.60-3.69 (m, 1H), 3.77
(s, 3H), 3.81 (s, 3H), 6.79 (d, J ) 8.3 Hz, 2H), 7.32 (d, J ) 8.3
Hz, 2H); 13C NMR δ 14.19, 20.39, 32.81, 33.89, 34.38, 46.69,
52.11, 55.23, 76.45, 113.68, 129.27, 134.12, 157.77, 161.54,
196.24; IR 2970, 2140, 1720, 1645, 1310, 1240, 1200 cm-1; MS
(m/z, relative intensity) 318 (M+, 3), 258 (10), 216 (26), 200
(32), 184 (27), 155 (53), 134 (38), 172 (19), 121 (90), 91 (100);
HRMS calcd for C17H22N2O4, 318.1580, found 318.1584.
Meth yl 2-Dia zo-3-oxo-6-(4-h yd r oxyp h en yl)-4-p r op yl-
h exa n oa te (1g). The same diazo transfer procedure as for
the synthesis of 1a was followed for 11 (220 mg, 0.79 mmol).
The crude product was subjected to column chromatography,
eluting with 4:1 petroleum ether/EtOAc to give 1g as a yellow
oil (95 mg, 39%): Rf ) 0.21 (petroleum ether/EtOAc ) 4:1).
1H NMR δ 0.88 (t, J ) 7.2 Hz, 3H), 1.24-1.38 (m, 2H), 1.40-
1.49 (m, 1H), 1.66-1.78 (m, 2H), 1.99-2.10 (m, 1H), 2.55-
2.64 (m, 2H), 3.61-3.70 (m, 1H), 3.82 (s), 7.15-7.22 (m, 4H).
13C NMR δ 14.11, 20.28, 33.01, 33.26, 34.31, 46.49, 52.11,
76.40, 121.73, 129.80, 141.48, 147.35, 161.42, 195.95. IR 2960,
2140, 1720, 1645, 1365, 1150; MS (m/z, relative intensity) 304
(M+, 3), 276 (4), 233 (28), 201 (30), 120 (75), 107 (100); HRMS
calcd for C16H20N2O4 304.1423, found 304.1399.
Gen er a l P r oced u r e for Rh (II)-Ca ta lyzed Din itr ogen
Extr u sion fr om th e Dia zo Com p ou n d 1a -g. 1a -g (0.5
mmol) in CH2Cl2 or benzene (10 mL) was added to a stirring
solution of CH2Cl2 or benzene (10 mL) containing 1.0 mol %
Rh(II) at room temperature under nitrogen atmosphere. The
green, homogeneous solution was stirred for 10 to 14 h until
the completion of the reaction, as indicated by TLC. The
catalyst was removed by a short column, and the crude
reaction mixture was analyzed by 1H NMR (400 MHz) for
product ratio determination. Further column chromatography
and preparative TLC provided pure products for identification
and characterization. Our experiment and others2c indicated
that product ratio was independent of the scale of reaction,
substrate concentration, and the catalyst mol %.
Rh (II)-Ca ta lyzed Din itr ogen Extr u sion of Meth yl 2-Di-
a zo-3-oxo-6-(4-n itr op h en yl)-4-p r op ylh exa n oa te (1a ). Fol-
lowing the general procedure, cyclization was effected on 1a
(167 mg, 0.5 mmol). The product ratios were determined by
the integration of the following peaks: δ 8.13 (d, J ) 8.4 Hz),
δ 7.36 (d, J ) 8.4 Hz) of 3a and δ 8.19 (d, J ) 8.4 Hz), δ 7.48
(d, J ) 8.4 Hz) of 4a . The isolated yields of 3a and 4a were
as follows: Rh2(OAc)4, with CH2Cl2 as solvent, 92%; with
benzene as solvent, 77%; Rh2(O2CCF3)4, 80%; Rh2(acam)4, 77%.
Pure specimens of 3a and 4a were obtained by column
chromatography and preparative TLC separation. Methyl
5-methyl-2-oxo-3-[2-(4-nitrophenyl)ethyl]cyclopentanecarbox-
ylate (3a ): Rf ) 0.33 (petroleum ether/EtOAc ) 3:1); 1H NMR
δ 1.19 (d, J ) 6.5 Hz, 3H), 1.13-1.21 (m, 1H), 1.62-1.69 (m,
1H), 2.10-2.19 (m, 1H), 2.27-2.39 (m, 2H), 2.46-2.57 (m, 1H),
2.79 (d, J ) 11.7 Hz, 1H), 2.75-2.85 (m, 2H), 3.76 (s, 3H),
7.34 (d, J ) 8.4 Hz, 2H), 8.15 (d, J ) 8.4 Hz, 2H); 13C NMR δ
148.55, 168.54, 210.14; IR 2990, 1760, 1725, 1520, 1355 cm-1
;
MS (m/z, relative intensity) 305 (M+, 17), 274 (12), 263 (75),
246 (100), 231 (72), 203 (41), 176 (51), 160 (22), 115 (23), 97
(21); HRMS calcd for C16H19NO5 305.1263, found 305.1270.
Rh (II)-Ca ta lyzed Din itr ogen Extr u sion of Meth yl 2-Di-
azo-3-oxo-6-(4-ch lor oph en yl)-4-pr opylh exan oate (1b). Fol-
lowing the general procedure, cyclization was effected on 1b
(161 mg, 0.5 mmol). The product ratios were determined by
the integration of the following peaks: δ 3.75 (s), δ 2.76 (d, J
) 11.6 Hz) of 3b and δ 3.72 (s), δ 3.27 (d, J ) 12.0 Hz) of 4b.
The isolated yields of 3b and 4b were as follows: Rh2(OAc)4,
with CH2Cl2 as solvent, 96%; with benzene as solvent, 63%;
Rh2(O2CCF3)4, 72%; Rh2(acam)4, 61%. Pure specimens of 3b
and 4b were obtained by preparative TLC separation. Methyl
5-methyl-2-oxo-3-[2-(4-chlorophenyl)ethyl]cyclopentanecarbox-
ylate (3b): Rf ) 0.46 (petroleum ether/EtOAc ) 5:1). 1H NMR
δ 1.19 (d, J ) 6.5 Hz, 3H), 1.15-1.22 (m, 1H), 1.56-1.60 (m,
1H), 2.07-2.15 (m, 1H), 2.23-2.37 (m, 2H), 2.48-2.56 (m, 1H),
2.60-2.71 (m, 2H), 2.76 (d, J ) 11.6 Hz, 1H), 3.75 (s, 3H),
7.10 (d, J ) 8.3 Hz, 2H), 7.25 (d, J ) 8.3 Hz, 2H); 13C NMR δ
19.01, 31.16, 32.59, 33.94, 36.08, 49.45, 52.23, 62.69, 128.36,
129.56, 131.59, 139.54, 169.34, 212.32; IR 2960, 1755, 1720,
1485, 1200, 1135 cm-1. MS (m/z, relative intensity) 294 (M+,
3), 263 (5), 169 (4), 156 (100), 138 (12), 124 (73), 101 (11), 69
(33); HRMS calcd for C16H19ClO3 294.1023, found 294.1020.
Methyl 2-oxo-5-(4-chlorophenyl)-3-propylcyclopentanecarboxy-
late (4b) was isolated as mobile fraction: Rf ) 0.53 (petroleum
ether/EtOAc ) 0.53); 1H NMR δ 0.95 (t, J ) 7.0 Hz, 3H), 1.31-
1.50 (m, 3H), 1.63 (q, J ) 12.2 Hz, 1H), 1.81-1.93 (m, 1H),
2.42-2.61 (m, 2H), 3.27 (d, J ) 12.0 Hz, 1H), 3.72 (s, 3H),
3.67-3.73 (m, 1H), 7.20 (d, J ) 8.4 Hz, 2H), 7.30 (d, J ) 8.4
Hz, 2H); 13C NMR δ 13.93, 20.56, 31.72, 35.54, 43.42, 50.19,
52.60, 62.28, 128.25, 128.95, 129.75, 139.57, 169.02, 211.12;
IR 2970, 1760, 1720, 1440, 1265, 1125, 1085 cm-1; MS (m/z,
relative intensity) 294 (M+, 13), 263 (10), 235 (100), 220 (25),
201 (35), 165 (30), 131 (16), 101 (13); HRMS calcd for
C
16H19ClO3 294.1023, found 294.1027.
Rh (II)-Ca ta lyzed Din itr ogen Extr u sion of Meth yl 2-Di-
azo-3-oxo-6-(4-acetam in oph en yl)-4-pr opylh exan oate (1c).
Following the general procedure, cyclization was effected on
1c (171 mg, 0.5 mmol). The product ratios were determined
by the integration of the following peaks: δ 8.32 (s), δ 7.42 (d,
J ) 8.2 Hz), δ 7.08 (d, J ) 8.2 Hz), δ 3.76 (s), δ 2.76 (d, J )
11.6 Hz) of 3c and δ 8.44 (s), δ 7.50 (d, J ) 8.3 Hz), δ 7.18 (d,
J ) 8.3 Hz), δ 3.69 (s), δ 3.29 (d, J ) 12.0 Hz) of 4c. The
isolated yields of 3c and 4c were as follows: Rh2(OAc)4, with
CH2Cl2 as solvent, 83%; with benzene as solvent, 71%;
Rh2(O2CCF3)4, 69%; Rh2(acam)4, 74%. 3c and 4c was found
to be inseparable with column chromatography and prepara-
tive TLC. A pure specimen of methyl 5-methyl-2-oxo-3-[2-(4-
acetaminophenyl)ethyl]cyclopentanecarboxylate (3c) was syn-
thesized in two steps from 3a (vide infra). 1H NMR and 13C
NMR for 3c and 4c were obtained by comparing the spectra
of the mixture and that of pure 3c. Methyl 5-methyl-2-oxo-
3-[2-(4-acetaminophenyl)ethyl]cyclopentanecarboxylate (3c):
1H NMR δ 1.18 (d, J ) 6.4 Hz, 3H), 1.13-1.22 (m, 1H), 1.55-
1.63 (m, 1H), 2.14 (s, 3H), 2.23-2.38 (m, 2H), 2.46-2.73 (m,
3H), 2.76 (d, J ) 11.6 Hz, 1H), 3.76 (s, 3H), 7.10 (d, J ) 8.2
Hz, 2H), 7.41 (d, J ) 8.2 Hz, 2H), 7.74 (s, 1H); 13C NMR δ
19.15, 24.41, 31.39, 32.82, 34.12, 36.20, 49.66, 52.38, 62.90,
120.07, 128.77, 136.08, 137.05, 168.51, 169.60, 212.96; IR 3320,
2960, 1720, 1660, 1600, 1540 cm-1; MS (m/z, relative intensity)
317 (M+, 11), 286 (10), 161 (100), 124 (76), 119 (90); HRMS