＂IPSO＂ Photosubstitution of Sterically Hindered Phenols

具有立體阻礙的酚類化合物其照光同位取代反應

林隆清(Lung-Ching Lin) ； 胡紀如(Jih-Ru Hwu)

《中央研究院化學研究所集刊》 28期 (1981/03) Pp. 43-48

https://doi.org/10.6522/BICAS.1981.28.5

摘要

具有立體阻礙的酚類化合物（如2,4,6-tri-t-butylphenol）的二氯甲烷溶液，加入溴，以Hanovia中壓水銀燈照射後可得同位取代的產物（2,6-dibromo-4-t-butylphenol）而2,6-di-t-butylphenol照光反應，所得產物為2,4-dibromo-6-t-butylph.nol，可是4-hydroxy-3,5-di-t-butylbenzoic acid在同樣條件下照光反應，卻生成3-bromo-5-t-bytyl-4-hydroxybenzoic acid。 同樣步驟，已具有立體阻礙的4-substituted-2,6-di-2-butylphenol（如methyl 3,5-di-t-butyl-4-hydrozybenzoate）行照光溴化反應，所得產物為4-Substituted-2-bromo-6-t-butylphenol（methyl 3-bromo-5-t-butyl- 4-hydroxybenzoate）。

並列摘要

When a dichloromethane solution of a sterically hindered phenol (e. g. 2, 4. 6-tri-t-butylphenol) with bromine was irradiated with a Hanovia medium pressure mercury lamp, the ipso substitution product (2.6-dibromo-4- t-butylphenol) was obtained. When 2,6-di-t-butylphenol was irradiated. 2. 4- dibromo-6-t-butylphenol was obtained. However, irradiation of 4-hydroxY-3. 5. di-t-butylbenzoic acid under the same conditions produced 3-bromo-5-t-butyl- 4-hydroxybenzoic acid. By the same procedure. photobromination of a sterically crowded 4- substituted-2. 6-di-t-butylphenol (e. g. methyl 3. 5-di-t-butyl-4-hydroxybenzoate) gave a 4-substituted-2-bromo-6-t-butylphenol (methyl 3-bromo-5-t-butyl-4-hydroxybenzoate)