チオフェン誘導体の合成化学的研究(第3報) : 2-Bromo-3-(5-nitro-2-thienyl)acrylic Acidおよびその関連化合物の合成

抄録

The Perkin reaction of 5-nitro-2-thiophenecarboxyaldehyde (XII) and monobromoacetic acid afforded 2-bromo-3-(5-nitro-2-thienyl) acrylic acid (X), which was also obtained by oxidation of XI. Dehydrobromination of 2, 3-dibromo-3-(5-nitro-2-thienyl)-propionic acid (IV) afforded 2-bromo-3-(5-nitro-2-thienyl) acrylic acid (IX) (α-form) as yellow crystals of m.p. 95.5∼97°, and its β-form as yellow needles, m.p. 255∼256° (decomp.). Heating of IX in dioxan with hydrochloric acid gave αβ-form 2-bromo-3-(5-nitro-2-thienyl) acrylic acid. (X). Infrared and ultraviolet spectra of VIII and IX suggested that they are stereoisomers. Dehydrobromination of ethyl 2, 3-dibromo-3-(5-nitro-2-thienyl) propionate afforded the α-form (yellow prisms, m.p. 94∼95°) (VI) and β-form (yellow needles, m.p. 127∼128°) (VII) of ethyl 2-bromo-3-(5-nitro-2-thienyl) acrylate. VII was obtained on heating VI and they were found to be stereoisomers from their infrared and ultraviolet spectra. Hydrolysis of VI and VII gave the same VIII, and therefore, the bromine atom liberated by the dehydrobromination of III and IV was found to have been in the 2-position.