Abstract
Reaction of 2-acetyl-5, 5-diphenyl-2, 4-pentadienoic acid (Ia) and its methyl ester (Ib) with diazomethane gave rise to 3-acetyl-3-methoxycarbonyl-4-(β-phenylstyryl)-1-pyrazoline (IIb), which by elimination of nitrogen afforded methyl 2-acetyl-6, 6-diphenyl-3, 5-hexadienoate (IIIb). Similar reaction of 3-(γ-phenylcinnamylidene)-2, 4-pentanedione (Ic) and dimethyl γ-phenylcinnamylidenemalonate (Id) with diazomethane gave the adduct corresponding to 1-pyrazoline derivatives (IIc, IId), respectively. Heating of these compounds afforded denitrogenated products. Similarly, methyl 2-acetyl-5-phenyl-2, 4-pentadienoate (Ie) and 3-cinnamylidene-2, 4-pentanedione (If) reacted with diazomethane, followed by elimination of nitrogen, to afford methyl 2-acetyl-6-phenyl-3, 5-hexadienoate (IIIe) and 3-(4-phenyl-1, 3-butadienyl)-2, 4-pentadione (IIIf), respectively. The reaction of the pyrazoline (II) to give compound (III) involves the novel ring-cleavage of the cyclopropane intermediate, such as methyl 1-acetyl-2-(β-phenylstyryl)-cyclopropane-1-carboxylate (IX, where R1=phenyl, R2=methyl, R3=methoxy).
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