Condensation of 2-Naphthol and Naphthalenediols with <i>o</i>-Dichlorobenzene in the Presence of Aluminum Halides
作者:Konstantin Yuryevich Koltunov、Aleksey Nikolaevich Chernov、Gubbi Krishnamurthy Surya Prakash、George Andrew Olah
DOI:10.1248/cpb.60.722
日期:——
It is known that 1-naphthol, as a result of superelectrophilic (dicationic) activation in superacid media, is able to react with such deactivated aromatic compound as o-dichlorobenzene to give 4-(3,4-dichlorophenyl)-1-tetralone (2), which is a highly valuable intermediate in the synthesis of the antidepressant, sertraline (1) and other useful derivatives. However, the analogous reactivity of 2-naphthol and a variety of naphthalenediols towards o-dichlorobenzene has not been investigated thus far, although the corresponding tetralones, bearing dichlorophenyl moiety, could be of great pharmacochemical interest. In present work, we disclose that 1,5-, 1,6-, and 1,7- naphthalenediols (6a–c) react smoothly with o-dichlorobenzene in the presence of an excess of aluminum chloride or aluminum bromide to give the pairs of isomeric 4-(3,4-dichlorophenyl)- and 4-(2,3-dichlorophenyl)- 5-, 6-, and 7-hydroxy-1-tetralones (10a–c and 11a–c) in high overall yields. 2-Naphthol and 2,7-naphthalenediol (6d) exhibited comparatively lower reactivity, which however was sufficient to obtain the corresponding dichlorophenyl-2-tetralones in moderate yields. The mechanism of these reactions involving superelectrophilic dicationic or even tricationic intermediates, is discussed.
已知,在超酸介质中的超电亲性(双阳离子)激活作用下,1-萘酚能够与去活化的芳香化合物邻二氯苯反应,生成4-(3,4-二氯苯基)-1-四氢萘酮(2),该化合物是抗抑郁药舍曲林(1)及其他有用衍生物合成中的重要中间体。然而,至今尚未研究2-萘酚及多种萘二醇对邻二氯苯的类似反应性,尽管相应的四氢萘酮,含有二氯苯基部分,对药物化学具有重要的兴趣。在本研究中,我们揭示了1,5-、1,6-和1,7-萘二醇(6a–c)在铝氯化物或铝溴化物过量存在下,能够顺利与邻二氯苯反应,生成成对的异构体4-(3,4-二氯苯基)-和4-(2,3-二氯苯基)-5-、6-和7-羟基-1-四氢萘酮(10a–c和11a–c),且总体产率较高。2-萘酚和2,7-萘二醇(6d)的反应性相对较低,但仍足以获得相应的二氯苯基-2-四氢萘酮,并且产率适中。本文讨论了这些反应的机制,包括超电亲性双阳离子或甚至三阳离子中间体的参与。