Ic
lla-c la,b I, II a R'=H, R2=CN; b RI=H, R2=COOC2I-I~; c R l=Br, R2=4"BrCf;ILCO Compounds I cannot have the isomeric 6-aryl-4-hydroxypyridazine structure because the long-wavelength maximum (280-284 rim) corresponds to that of 3-carboxy-6-methyl-4-oxo-1-phenyl-1H-pyridazin-3-carboxylic acid (277 nm) [21 and not to that of 4-hydroxy-(or 4-methoxy)-pyridazines (254-260 rim) [2, 3].
Evidently the reaction occurs via formation of intermediate products of nucleophilic addition of hydrazine at atom C5 of the furanones II (5-substituted 1-aryl-hydrazino-3,4-dioxo-l-pentenes) which subsequently undergo heterocyclization to 6-aryl-1 H-pyridazin-4-ones.
Aqueous hydrazine solution (70%, 0.65 ml) was added with stirring to a suspension of IIa, b (0.01 mole) [4] or IIc [5] in ethanol (100 ml). In the case of IIa, b the precipitate was filtered off after 1 h and crystallized from acetone. For furanone IIc the mixture was refluxed for 2 h, the precipitate filtered off, and crystallized from a mixture of DMF-ethanol (1:1) to give Ic. Refluxing a mixture of IIb with excess 70% hydrazine solution in ethanol gives 7-phenyl-l,2,3,4-tetrahydropyridazino[4,3c]pyridazin-3-one [6]. Compound Ia. Yield 79%, mp 273-274~ (decomp.). UV spectrum (0.01 molar in ethanol): >'m,~ (loge): 2t0 (4.10), 255 (4.30), 280 nm (4.20). IR spectrum (KBr): 3240-3220 (NH), 3110-3085 (C-H), 2270 (C~N), 1625-1595 cm -I (4-C=O, C=C, C=N). PMR spectrum (DMSO-D6): 4.06 (2H, s, CH2), 6.72 (1H, s, 5-H), 7.60-7.85 (5H, m, C6Hs), 13.70 ppm (1H, br, NH). Compound Ib. Yield 75%, mp 200-201~ (decomp.). Mass spectrum, m/z (I,~1, %): 258 (81) [M] +, 213 (57) [M -C2H50] +, 212 (94) [M -C2HsO-H] +, 186 (100) [M -C2H4-CO2] +, 157 (15) [M -C2H5OCO-CO] +, 145 (78) [C6Hs-C(=NH)CH=C=O] +, 103 (12) [Cc, I-I5--C,.N] +, 102 (13) [C6HsCaCH] + 68 (11) [N,,C--CH2--C,,O] +. Compound Ie. Yield 67%, mp 280-2810C (decomp.). IR spectrum (KBr): 3450-3320 (NH), 1637 (Co)=O), 1590-1580, 1560 cm -1 (C=O chelate, C=C, C=N). PMR spectrum (DMSO-D6): 6.70 (1H, s, 5-1-I); 7.70-8.05 (9H, m, CH~ 2C6tG), 13.42-13.72 ppm (2H, br, 2NH). Mass spectrum, m/z (I,,a. %): 450 (18), 448 (32), 446 (20) [M] ยง 422 (15), 420 (28), 418 (14) [M -CO] +, 225 (6), 223 (5) [4-BrC6I-hCOCHz-CmN] +, 185 (93), 183 (100) [4-BrCd-la-C-O] +, 184 (17), 182 (12) [4-BrC6HaC-NH] ยง 157 (22), 155 (27) [4-BrC6H4] +.