Condensation of 2-naphthol and naphthalenediols with o-dichlorobenzene in the presence of aluminum halides.
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.
Boreskov Institute of Catalysis, Novosibirsk, Russia.
Konstantin Yuryevich
KY
Koltunov
Aleksey Nikolaevich
AN
Chernov
Gubbi Krishnamurthy
GK
Surya Prakash
George Andrew
GA
Olah
D000077410:Aluminum Chloride; D017607:Aluminum Compounds / Q000737:chemistry*; D002712:Chlorides / Q000737:chemistry*; D002722:Chlorobenzenes / Q000737:chemistry*; D015394:Molecular Structure; D009284:Naphthols / Q000737:chemistry*; D013237:Stereoisomerism; D044024:Tetralones / Q000138:chemical synthesis* / Q000737:chemistry
C569805:2,3-naphthalenediol; D017607:Aluminum Compounds; D002712:Chlorides; D002722:Chlorobenzenes; D009284:Naphthols; D044024:Tetralones; D000077410:Aluminum Chloride; C004726:2-dichlorobenzene; C028405:2-naphthol