References
<A NAME="RU05602ST-1">1</A>
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Heterocyclic Chemistry
Vol. 2:
Bird CW.
Pergamon Press;
Oxford:
1996.
For recent examples of pyrrole syntheses
based on Paal-Knorr reaction, see:
<A NAME="RU05602ST-2A">2a</A>
Hewton CE.
Kimber MC.
Taylor DK.
Tetrahedron Lett.
2002,
43:
3199
<A NAME="RU05602ST-2B">2b</A>
Takaya H.
Kojima S.
Murahashi S.-I.
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2001,
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421
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Braun RU.
Zeitler K.
Muller TJJ.
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<A NAME="RU05602ST-2D">2d</A>
Surya Prakash Rao H.
Jothilingam S.
Tetrahedron
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2001,
42:
6595
For recent examples of pyrrole syntheses
that are not based on Paal-Knorr reaction, see:
<A NAME="RU05602ST-3A">3a</A>
Chen N.
Lu Y.
Gadamasetti K.
Hurt CR.
Norman MH.
Fotsch C.
J. Org. Chem.
2000,
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2603
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Katritzky AR.
Huang
T.-B.
Voronkov MV.
Wang M.
Kolb H.
J. Org. Chem.
2000,
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8819
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Gabriele B.
Salerno G.
Fazio A.
Bossio MR.
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2001,
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1339
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Kel’in AV.
Sromek AW.
Gevorgyan V.
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2001,
123:
2074
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Allin SM.
Barton WRS.
Bowman WR.
McInally T.
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2001,
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7887
<A NAME="RU05602ST-3F">3f</A>
Lagu B.
Pan M.
Wachter MP.
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6027
<A NAME="RU05602ST-4">4</A>
Doyle MP.
McKervey MA.
Ye T.
Modern Catalytic Methods for Organic Synthesis
with Diazo Compounds
Wiley Interscience;
New
York:
1998.
<A NAME="RU05602ST-5A">5a</A>
Calter MA.
Sugathapala PM.
Zhu C.
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3837
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Calter MA.
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8813
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<A NAME="RU05602ST-6">6</A>
General procedure for the TiCl4-promoted
condensation of α-diazo-β-ketoester 1 with N-tosylimine:
To a solution of 2a (10.0 mmol) in anhydrous
CH2Cl2 (20 mL) at -41 °C
were added dropwise TiCl4 (11.0 mmol) and Et3N
(11.0 mmol). After the resulting red-dark solution was stirred at -41 °C
for 1 h, a solution of N-tosylimine (4
mmol) in anhydrous CH2Cl2 (4 mL) was added
dropwise. The reaction mixture was stirred at -41 °C
for 9 h and then was quenched with saturated aqueous NH4Cl
(5 mL). The organic layer was separated and the aqueous layer was
extracted with CH2Cl2 (2 × 20 mL).
The combined organic layers were washed with saturated aqueous NaHCO3 (2 × 20
mL), and then dried over Na2SO4. The product
was purified by flash chromatography to yield 3a (Ar = Ph)
as white solid (1.03 g, 62%). Mp 140-142 °C;
IR (KBr) 3223, 2152, 1748, 1625 cm-1; 1H
NMR (200 MHz, CDCl3) δ 1.32 (t, J = 7 Hz, 3 H), 2.37 (s, 3 H), 3.19
(dd, J = 15.6, 5.4 Hz, 1 H),
3.36 (dd, J = 15.6, 8 Hz, 1 H),
4.28 (q, J = 7 Hz, 2 H), 4.76-4.86
(m, 1 H), 5.69 (d, J = 7.8 Hz,
1 H), 7.14-7.20 (m, 7 H), 7.58 (d, J = 8.2
Hz, 2 H); 13C NMR (50 MHz, CDCl3) δ 14.2,
21.4, 46.3, 54.5, 61.6, 76.8, 126.3, 127.0, 127.4, 128.4, 129.2,
137.4, 140.1, 143.0, 161.1, 189.8; MS m/z (FAB):
416 [(M+H)+, 13],
388 (3), 344 (2), 261 (11), 245 (69), 219 (20), 181 (12), 171 (49),
139 (23), 115 (38), 91 (100), 77 (22), 59 (38), 41 (53). Anal. Calcd
for C20H21N3O5S: C,
57.82; H, 5.09; N, 10.11. Found: C, 57.85; H, 5.09; N, 10.01.
For examples of intramolecular N-H
bond insertion, see:
<A NAME="RU05602ST-7A">7a</A>
Moyer MP.
Feldman PL.
Rapoport H.
J. Org. Chem.
1985,
50:
5223
<A NAME="RU05602ST-7B">7b</A>
Wang J.
Hou Y.
J. Chem. Soc., Perkin Trans. 1
1999,
2277
<A NAME="RU05602ST-8">8</A>
General procedure for the diazo decomposition
of 3 with catalyst Rh2(OAc)4:
A solution of 3a (Ar = Ph, 1.0
mmol) in benzene (30 mL) containing Rh2(OAc)4 (0.01
mmol) was heated under reflux for 10 min. The solution was cooled
to room temperature and was concentrated. Purification by flash
chromatography provided 4a (Ar = Ph,
75% yield) as white solid.
4a:
Mp 138-140 °C; IR (KBr) 3453, 3304, 3278, 1692
cm-1; 1H
NMR (200 MHz, CDCl3) δ 1.37 (t, J = 7.2 Hz, 3 H), 4.37 (q, J = 7.2 Hz, 2 H), 6.16 (d, J = 3.2 Hz, 1 H), 7.25-7.79 (m,
5 H), 7.91 (br, s, 1 H), 8.76 (br, d, 1 H); 13C
NMR (50 MHz, CDCl3) δ 14.6, 61.2, 95.9, 106.2,
124.9, 128.2, 128.6, 131.1, 136.0, 155.2, 162.0; MS m/z (EI) 231 (M+,
91), 203 (3), 185 (100), 156 (18), 129 (12), 102 (72), 77 (14),
51 (6); Anal. Calcd for C13H13NO3:
C, 67.52; H, 5.67; N, 6.06. Found: C, 67.45; H, 5.59; N, 5.91.
4b: Mp 91-93 °C; IR (KBr)
3489, 3310, 1696, 1677 cm-1; 1H
NMR (200 MHz, CDCl3) δ 1.37 (t, J = 7.2 Hz, 3 H), 2.43 (s, 3
H), 4.35 (q, J = 7.2 Hz, 2 H),
5.98 (d, J = 2.6 Hz, 1 H), 7.23-7.37(m,
4 H), 7.76 (br, s, 1 H), 8.11 (br, s, 1 H); 13C NMR
(50 MHz, CDCl3) δ 14.5, 20.7, 60.0, 98.8, 105.5, 126.0,
128.3, 128.4, 130.9, 131.5, 135.7, 135.9, 153.7(br), 162.0(br);
MS m/z (EI) 245 (M+,
100), 222 (3), 199 (93), 193 (28), 171 (12), 144 (12), 134 (12),
123 (28), 116 (63), 95 (7), 91 (6), 77 (6), 57 (6), 43 (7). Anal.
Calcd for C14H15NO3: C, 68.56;
H, 6.16; N, 5.71. Found: C, 68.45; H, 6.18; N, 5.61.
4c: Mp 203 °C; IR (KBr) 3501,
3337, 2227, 1669 cm-1; 1H NMR
(200 MHz, CDCl3/DMSO-d
6
) δ 1.41 (t, J = 7.2 Hz, 3 H), 4.39 (q, J = 7.2 Hz, 2 H), 6.17 (d, J = 2.8 Hz, 1 H), 7.44-7.56
(m, 2 H), 7.89-7.95 (m, 2 H), 8.15 (s, 1 H), 10.91 (br,
s, 1 H); 13C NMR (50 MHz, CDCl3/DMSO-d
6
) δ 14.1,
59.4, 95.7, 106.9, 112.0, 118.1, 128.0, 128.9, 129.9, 132.2, 132.5, 152.7,
161.4; MS m/z (EI) 256 (M+,
14), 241 (2), 210 (20), 178 (5), 171 (43), 155 (57), 127 (14),
107 (22), 91 (100), 65 (39), 57 (31), 39 (18); Anal. Calcd for C14H12N2O3:
C, 65.62; H, 4.72; N, 10.93. Found: C, 65.81; H, 4.59; N, 10.83.
4d: Mp 150-152 °C; IR
(KBr) 3269, 1680, 1661 cm-1; 1H NMR
(200 MHz, CDCl3/DMSO-d
6
) δ 1.37 (t, J = 7.2 Hz,
3 H), 4.34
(q, J = 7.2 Hz, 2 H), 5.94 (d, J = 2.8 Hz, 1 H), 6.88 (d, J = 16.4 Hz, 1 H), 7.06 (d, J = 16.4 Hz, 1 H), 7.21-7.44 (m,
5 H), 7.91 (s, 1 H), 11.0 (br s, 1 H); 13C
NMR (50 MHz, CDCl3/DMSO-d
6
) δ 14.0, 58.9, 94.8,
105.2, 117.6, 125.4, 126.9, 127.9, 128.3, 133.8, 136.0, 152.6, 161.1;
MS m/z (EI) 257 (M+,
100), 210 (88), 183 (11), 182 (6), 167 (8), 154 (28), 128 (46),
102 (5), 77 (6), 51 (5), 29 (5); Anal. Calcd for C15H15NO3:
C, 70.02; H, 5.88; N, 5.44. Found: C, 70.22; H, 6.08; N, 5.29.
4e: Mp 131-133 °C; IR
(KBr) 3306, 1667, 1564 cm-1; 1H NMR
(200 MHz, CDCl3) δ 1.38 (t, J = 7.2
Hz, 3 H), 4.38 (q, J = 7.2 Hz,
2 H), 6.06 (d, J = 2.6 Hz, 1
H), 6.45-6.47 (m, 1 H), 6.56 (d, J = 3.4
Hz, 1 H), 7.41-7.42 (m, 1 H), 7.92 (br s, 1 H), 8.59 (br
s, 1 H); 13C NMR (50 MHz, CDCl3) δ 14.5, 60.1,
94.6, 105.4, 106.2, 111.7, 126.8, 142.0, 146.5, 154.4, 162.1; MS m/z (EI) 221 (M+,
95), 193.3 (4), 175 (100), 147 (26), 139 (2), 119 (15), 92 (52),
91 (8), 63 (15), 39 (12); Anal. Calcd for C11H11NO4:
C, 59.73; H, 5.01; N, 6.33. Found: C, 59.65; H, 4.97; N, 6.13.
4f: Mp 129-130 °C; IR
(KBr) 3502, 3289, 1677, 1574, 1539 cm-1; 1H
NMR (200 MHz, CDCl3) δ 1.38 (t, J = 7.2 Hz, 3 H), 4.37 (q, J = 7.2 Hz, 2 H), 5.99 (d, J = 3Hz, 1 H), 6.93-7.26
(m, 2 H), 8.08 (br s, 1 H), 8.84 (br, s, 1 H); 13C
NMR (50 MHz, CDCl3) δ 14.5, 60.3, 96.6, 123.7,
127.9, 129.7, 130.7, 131.9, 139.0, 144.5, 160.9; MS m/z (EI) 317 (M+, 80Br,
74), 315 (M+, 78Br, 71), 271 (100),
242 (12), 215 (9), 188 (37), 162 (76), 155 (17), 133 (14), 108 (19),
91 (40), 82 (9), 63 (14), 45 (5); Anal. Calcd for C11H10BrNO3S:
C, 41.79; H, 3.19; N, 4.43. Found: C, 41.85; H, 3.26; N, 4.40.
4g: Mp 139-142 °C; IR
(KBr) 3320, 1590, 1567 cm-1; 1H NMR
(200 MHz, CDCl3) δ 6.14 (d, J = 2.4
Hz, 1 H), 6.50 (dd, J = 3.5,
1.7 Hz, 1 H), 6.66 (d, J = 3.5
Hz, 1 H), 7.44 (d, J = 1.7 Hz,
1 H), 7.50-7.59 (m, 3 H), 7.77-7.82 (m, 2 H), 8.26
(br s, 1 H), 10.43 (br s, 1 H); 13C
NMR (50 MHz, CDCl3) δ 94.8, 108.2, 112.1, 116.0,
127.5, 129.0, 129.8, 131.6, 137.7, 142.7, 145.9, 159.3, 184.0; MS m/z (EI) 253 (M+,
100), 236 (5), 224 (4), 196 (4), 176 (30), 147 (7), 120 (9), 105
(37), 92 (24), 91 (3), 77 (49), 65 (20), 51 (17), 39 (15); Anal.
Calcd for C15H11NO3: C, 71.14;
H, 4.38; N, 5.53. Found: C, 70.98; H, 4.37; N, 5.46.
4h: Mp 159-161 °C; IR
(KBr) 3322, 2261, 1626, 1592, 1550, 1503 cm-1; 1H
NMR (200 MHz, CDCl3) δ 6.10 (d, J = 2 Hz, 1 H), 6.79 (d, J = 16.5 Hz, 1 H), 7.00 (d, J = 16.5 Hz, 1 H), 7.28-7.54
(m, 8 H), 7.68-7.72 (m, 2 H), 8.41 (br s, 1 H), 10.40 (br
s, 1 H); 13C NMR (50 MHz, CDCl3) δ 96.3, 116.6,
117.3, 126.6, 127.5, 128.5, 128.8, 128.9, 131.6, 132.0, 135.9, 137.7,
138.0, 159.5, 183.8; MS m/z (EI)
289 (M+, 100), 288 (27), 270 (10), 212 (13),
156 (6), 128 (23), 105 (49), 77 (31), 51 (7); Anal. Calcd for C19H15NO2:
C, 78.87; H, 5.23; N, 4.84. Found: C, 78.80; H, 5.21; N, 4.74.
4i: Mp 178-180 °C(decomposed);
IR (KBr) 3272, 1614, 1585, 1534 cm-1; 1H
NMR (200 MHz, CDCl3) δ 2.48 (s, 3 H), 3.85 (s,
3 H), 6.01 (d, J = 2.8 Hz, 1
H), 6.93 (d, J = 8.6 Hz, 2 H),
7.62 (d, J = 8.6 Hz, 2 H), 9.47
(br s, 1 H), 10.59 (br, s, 1 H); MS m/z (EI)
231 (M+, 100), 216 (93), 202 (9), 188 (5), 174
(8), 161 (15), 146 (4), 133 (18), 118 (7), 117 (8), 102 (3), 89
(12), 77 (4), 63 (6), 43 (13); Anal. Calcd for C13H13NO3:
C, 67.52; H, 5.67; N, 6.06. Found: C, 67.41; H, 5.71; N, 6.01.
<A NAME="RU05602ST-9">9</A>
p-Toluenesufinic
acid was further converted to thiosulfonic ester, which is isolated
and characterized.