References and Notes
1
Ruxer JM.
Lachoux C.
Ousset JB.
Torregrosa JL.
Mattioda GJ.
J. Heterocycl. Chem.
1994,
31:
409
2
Ungureanu M.
Mangalagiu I.
Grosu G.
Petrovanu M.
Ann. Pharm. Fr.
1997,
55:
69
3
Nasir AI.
Gundersen L.-L.
Rise F.
Antonsen Ø.
Kristensen T.
Langhelle B.
Bast A.
Custers I.
Haenen GRMM.
Wikström H.
Bioorg. Med. Chem. Lett.
1998,
8:
1829
4
Østby OB.
Dalhus B.
Gundersen L.-L.
Rise F.
Bast A.
Haenen GRMM.
Eur. J. Org. Chem.
2000,
3763
5
Østby OB.
Gundersen L.-L.
Rise F.
Antonsen Ø.
Fosnes K.
Larsen V.
Bast A.
Custers I.
Haenen GRMM.
Arch. Pharm. Pharm. Med. Chem.
2001,
334:
21
6a Ohtani M, Fuji M, Fukui Y, and Adachi M. inventors; WO 059999.
6b Salvati ME, Illig CR, Wilson KJ, Chen J, Meegalla SK, and Wall MJ. inventors; US 7030112.
6c Fu J.-M. inventors; US 7074791.
7
Cheng Y.
Ma B.
Wudl F.
J. Mater. Chem.
1999,
9:
2183
8
Mitsumori T.
Bednikov M.
Sedo J.
Wudl F.
Chem. Mater.
2003,
15:
3759
9
Mitsumori T.
Craig IM.
Martini IB.
Schwartz BJ.
Wudl F.
Macromolecules
2005,
38:
4698
10
Swamy KMK.
Park MS.
Han SJ.
Kim SK.
Kim JH.
Lee C.
Bang H.
Kim Y.
Kim S.-J.
Yoon J.
Tetrahedron
2005,
61:
10227
11
Zbancioc GN.
Mangalagiu II.
Synlett
2006,
804
12
Kuhla DE.
Lombardino JG.
Adv. Heterocycl. Chem.
1977,
21:
50
13
Satoh K.
Miyasaka T.
Arakawa K.
Yakugaku Zasshi
1977,
97:
422
14
Stetter H.
Landscheidt A.
J. Heterocycl. Chem.
1979,
16:
839
15
Abdelrazek FM.
Synth. Commun.
2005,
35:
2251
16a
Ohsawa A.
Abe Y.
Igeta H.
Bull. Chem. Soc. Jpn.
1980,
53:
3273
16b
Ohsawa A.
Abe Y.
Igeta H.
Chem. Pharm. Bull.
1980,
28:
3488
17
Khlebnikov AF.
Kostik EI.
Kostikov RR.
Synthesis
1993,
568
18
Veeraraghavan S.
Bhattacharjee D.
Popp FD.
J. Heterocycl. Chem.
1981,
18:
443
19
Siriwardana AI.
Nakamura I.
Yamamoto Y.
J. Org. Chem.
2004,
69:
3202
20
Flitsch W.
Kramer U.
Tetrahedron Lett.
1968,
12:
1479
For reviews on mesoionic compounds including münchnones, see:
21a
Palmer DC. In
Oxazoles: Synthesis, Reactions and Spectroscopy
Part A:
John Wiley and Sons;
New Jersey:
2003.
p.473-576
21b
Gribble GW. In Synthetic Applications of Dipolar Cycloaddition Chemistry towards Heterocycles and Natural Product
Padwa A.
Pearson WH.
John Wiley and Sons;
New York:
2002.
p.681-754
21c
Potts KT. In 1,3-Dipolar Cycloaddition Chemistry
Vol. 2:
Padwa A.
Wiley;
New York:
1984.
p.1-81
21d
Ollis WD.
Stanforth SP.
Ramsden CA.
Tetrahedron
1985,
41:
2239
21e
Ramsden CA.
Newton CG.
Tetrahedron
1982,
38:
2965
21f
Ramsden CA. In Comprehensive Organic Chemistry
Vol. 4:
Barton DHR.
Ollis WD.
Academic Press;
New York:
1979.
p.1171-1228
21g
Ollis WD.
Ramsden CA.
Adv. Heterocycl. Chem.
1976,
19:
1
22a
Huisgen R.
Gotthardt H.
Bayer HO.
Angew. Chem., Int. Ed. Engl.
1964,
3:
135
22b
Huisgen R.
Gotthardt H.
Bayer HO.
Chem. Ber.
1970,
103:
2356
23a
King JA.
McMillan FH.
J. Am. Chem. Soc.
1952,
74:
3222
23b
McMillan FH.
McMillan GB.
Kun KA.
King JA.
J. Am. Chem. Soc.
1956,
78:
407
23c
McMillan FH.
McMillan GB.
Kun KA.
King JA.
J. Am. Chem. Soc.
1956,
78:
2642
23d
Sayed AA.
Jahine H.
Zaher H.-A.
Sherif O.
Indian J. Chem.
1975,
13:
1142
23e
Ismail MF.
Shams NA.
Abdel Rahman SE.
Fateen AK.
Rev. Roum. Chim.
1979,
24:
899
23f
Jahine H.
Zaher HA.
Akhnookh Y.
El-Gendy Z.
Indian J. Chem., Sect. B: Org. Chem. Incl. Med. Chem.
1978,
16:
1000
24a
Tišler M.
Stanovnik B.
Adv. Heterocycl. Chem.
1968,
9:
211
24b
Tišler M.
Stanovnik B.
Adv. Heterocycl. Chem.
1979,
24:
365
24c
Tišler M.
Stanovnik B.
Adv. Heterocycl. Chem.
1990,
49:
385
24d
Csende F.
Szabo Z.
Bérnath G.
Stáger G.
Synthesis
1995,
1240
25
General Procedure for the Synthesis of Compounds 5
3 (2H)-Pyridazinone acid 2 (5 mmol) were suspended with stirring in Ac2O (5 mL) and then DMAD (5.5 mmol) was added.The reaction mixture was kept at ca. 90 °C for 3-4 h. The pyrrolopyridazine derivatives 5 were isolated by filtration or by evaporation of the solvent. In the latter case, the crude product was purified by recrystallization or by column chromatography using CH2Cl2 as eluent.
Dimethyl 2,7-Dimethylpyrrolo[1,2-
b
]pyridazine-5,6-dicarboxylate (5a)
Colorless crystals from EtOH with mp 135-136 °C; yield 60%. Anal. Calcd for C13H14N2O4: C, 59.54; H, 5.38; N, 10.68. Found: C, 59.87; H, 5.70; N, 10.93. 1H NMR (300 MHz, CDCl3): δ = 2.52 (s, 3 H, 2-Me), 2.61 (s, 3 H, 7-Me), 3.89, 3.95 (2 s, 6 H, 2 MeO), 6.76 (d, 1 H, J = 9.3 Hz, H-3), 8.27 (d, 1 H, J = 9.3 Hz, H-4). 13C NMR (75 MHz, CDCl3): δ = 9.7 (7-Me), 21.8 (2-Me), 51.3, 52.2 (2 MeO), 101.6 (C-5), 116.3 (C-3), 117.7, 127.6, 128.3 (C-4a, C-6, C-7), 127.5 (C-4), 152.4 (C-2), 163.8, 166.3 (2 COO).
26
General Procedure for the Synthesis of Compounds 3
Acid 6b or 6d (1 g) in Ac2O (3 mL) was kept at ca. 90 °C for 3 h. The yellow precipitate was filtered and washed with Ac2O and then with anhyd Et2O.
3-Methyl-6-phenyloxazolo[3,2-
b
]pyridazinium-2-oxide (3b)
Yellow crystals from Ac2O with mp 199-202 °C; yield 72%. Anal. Calcd for C13H10N2O2: C, 69.02; H, 4.46; N, 12.38. Found: C, 69.43; H, 4.78; N, 12.70. 1H NMR (300 MHz, CDCl3): δ = 2.36 (s, 3 H, 3-Me), 7.31, 7.36 (2 d, 2 H, J = 8.8 Hz, H-7, H-8), 7.48-7.53, 7.89-7.94 (2 m, 5 H, H-2′, H-3′, H-4′, H-5′, H-6′). 13C NMR (75 MHz, CDCl3): δ = 6.9 (3-Me), 94.7 (C-3), 110.0, 112.3 (C-7, C-8), 126.7, 129.0 (C-2′, C-3′, C-5′, C-6′), 130.2 (C-4′) 134.6 (C-1′), 138.4 (C-8a), 153.9 (C-6), 160.4 (2-CO).
27
General Procedure for the Synthesis of 7 and 8
The experimental procedure for compounds 7 and 8 was similar to those for pyrrolopyridazines 5. The two compounds were isolated by column chromatography using neutral alumina (Merck 200-20 mesh) and CH2Cl2 as eluent.
Dimethyl 2-Methylpyrrolo[1,2-
b
]pyridazine-5,6-dicarboxylate (7a)
Colorless crystals from EtOH with mp 89-91 °C; yield 22%. Anal. Calcd for C12H12N2O4: C, 58.06; H, 4.87; N, 11.29. Found: C, 59.34; H, 5.21; N, 10.50. 1H NMR (300 MHz, CDCl3): δ = 2.52 (s, 3 H, 2-Me), 3.91, 3.92 (2 s, 6 H, 2 MeO), 6.75 (d, 1 H, J = 9.3 Hz, H-3), 7.92 (s, 1 H, H-7), 8.26 (d, 1 H, J = 9.3 Hz, H-4). 13C NMR (75 MHz, CDCl3): δ = 21.7 (2-Me), 51.4, 52.1 (2 MeO), 103.4 (C-5), 117.3 (C-3), 117.9, 128.7 (C-4a, C-6, C-7), 121.0 (C-7), 128.2 (C-4), 153.4 (C-2), 163.7, 164.5 (2 COO).
Dimethyl 3-[(
E
)-(Buten-2-yl-1,4-dioate)]-6-methyloxazolo[3,2-
b
]pyridazinium-2-oxide (8a)
Yellow crystals from MeCN with mp 180-183 °C; yield 39%. Anal. Calcd for C13H12N2O6: C, 53.43; H, 4.14; N, 9.59. Found: C, 53.59; H, 4.33; N, 9.74. 1H NMR (300 MHz, CDCl3): δ = 2.65 (s, 3 H, 6-Me), 3.76, 3.99 (2 s, 6 H, 2 MeO), 6.97 (s, 1 H, =CHCOO), 7.21 (d, 1 H, J = 8.8 Hz, H-7), 7.45 (d, 1 H, J = 9.3 Hz, H-8). 13C NMR (75 MHz, CDCl3): δ = 21.6 (6-Me), 51.7, 52.9 (2 MeO), 94.2 (C-3), 109.5 (C-10), 113.1 (C-8), 121.5 (C-7), 135.6 (C-9), 140.8 (C-8a), 155.4 (C-6), 156.8 (2-CO), 166.1, 166.7 (2 COO). Off-resonance NMR experiment: J
C-3-H-10 = 6.3 Hz; J
9-CO-H-10 = 11.5 Hz.
28a
Pleininger H.
Wild D.
Chem. Ber.
1966,
99:
3070
28b
Fried F.
Taylor JB.
Westwood R.
J. Chem. Soc., Chem. Commun.
1971,
226
28c
Kon Thoo Lin PVS.
Buchan R.
Fraser M.
McHattie D.
Heterocycles
1990,
31:
1459
28d
Tighineanu E.
Rãileanu D.
Rev. Roum. Chim.
1992,
37:
1307
28e
Tighineanu E.
Rãileanu D.
Simonov Yu.
Bouroº P.
Tetrahedron
1996,
52:
12475
28f
Cavdar H.
Saracoglu N.
J. Org. Chem.
2006,
71:
7793
28g
Jones RA.
Sepulveda Arques J.
Tetrahedron
1981,
37:
1597
29a
Vogeli U.
von Philipsborn W.
Org. Magn. Reson.
1975,
7:
617
29b
Barillier D.
Strobel MP.
Morin L.
Paquer D.
Tetrahedron
1983,
39:
767
29c
Gregory B.
Hinz W.
Jones RA.
Sepulveda Arques J.
J. Chem. Res., Synop.
1984,
311
30a
Vasilescu M.
Dumitraºcu F.
Lemmetyinen H.
Tkachenko N.
J. Fluoresc.
2004,
14:
443
30b
Vasilescu M.
Dumitraºcu F.
Bandula R.
Drãghici C.
Lemmetyinen H.
Rev. Roum. Chim.
2004,
49:
905
31
General Procedure for the Synthesis of Compounds 9
Esters 5 or 6 (2 mmol) were dissolved in AcOH (10 mL) and under reflux was added Zn powder (3 mmol) over a period of 3 h. The reaction was monitored by 1H NMR or TLC. In the case when the reaction was found to be incomplete, Zn (1 mmol) was added and refluxing was continued for ca. 2 h. The hot reaction mixture was filtered and the precipitate was washed with AcOH. The AcOH was removed and the residue was purified by column chromatography.
Dimethyl 2-Phenyl-3,4-dihydropyrrolo[1,2-
b
]pyri-dazine-5,6-dicarboxylate (9b)
Colorless crystals from EtOH with mp 145-147 °C; yield 77%. Anal. Calcd for C17H16N2O4: C, 65.38; H, 5.16; N, 8.97. Found: C, 65.72; H, 5.33; N, 9.21. 1H NMR (300 MHz, CDCl3): δ = 2.92 (t, 2 H, J = 8.1, 8.0 Hz, 3-CH2), 3.26 (t, 2 H, J = 8.1, 8.0 Hz, 4-CH2), 3.84, 3.87 (2 s, 6 H, 2 MeO), 7.46-7.48 (m, 3 H, H-3′, H-4′, H-5′), 7.54 (s, 1 H, H-7), 7.85-7.88 (m, 2 H, H-2′, H-6′). 13C NMR (75 MHz, CDCl3): δ = 17.5 (4-CH2), 21.2 (3-CH2), 51.4, 51.5 (2 MeO), 109.7, 113.9, 127.2 (C-4a, C-5, C-6), 125.5 (C-7), 126.4, 128.7 (C-2′, C-3′, C-5′, C-6′), 131.0 (C-4′), 135.2 (C-1′), 160.0 (C-2), 164.0, 165.5 (2 COO).
32 Crystal data for 9b (R1 = Ph, R2 = H): C17H16N2O4; colorless plate; M = 312.32, orthorhombic, Pbca, a = 8.1844(2) Å, b = 13.4925(3) Å, c = 27.0683(6) Å, V = 2989.1(1) Å3, Z = 8, T = 113(2) K, F
000 = 1312, R1 = 0.0440, wR2 = 0.1089. The CCDC deposition number is 651836.
33
Caira MR.
Dumitraºcu F.
Drãghici C.
Dumitrescu D.
Cristea M.
Molecules
2005,
10:
360