In the first step of the synthesis of Sertraline, aluminium chloride catalyst was used in a Friedel-Craft's reaction to give the following product. My question is how does the exact mechanism work? 1-napthol does not seem look like an electrophile to me, and I do not understand how AlCl3 is able to turn 1-napthol into an electrophile. The best guess I have is that the phenol tautomerise to give a ketone, and AlCl3 forms a complex with it. Yet again, I do not understand how the γ carbon is made electrophilic using AlCl3. Any help would be appreciated.
The alleged original RSC source for this reaction was not accessible online.1. However, Olah et al. have reported2 that α-naphthol 1 in superacid medium forms a dication species 4. The use of excess AlCl3 provides a mechanism for the formation of superacid 3. Benzylic dication 4 undergoes substitution of o-dichlorobenzene 5 which ultimately forms the sertraline precursor, tetralone 8. For reaction conditions, see ref. 3. No reducing agent is required.
1) Kavitha, C. V.; Mantelingu, K.; Sarala, G.; Naveen, S.;
Anandalwar, S. M.; Prasad, J. S.; Rangappa, K. S. J. Chem. Res. 2006,
2) Koltunov, K. Y.; Chernov, A. N.; Prakash, G. K. S.; Olah, G. A. Chem. Pharm. Bull. 2012, 60, 722.
3) Lee, S. H.; Kim, I. S.; Qing, R. L.; Dong, G. R.; Jeong, L. K.; Jung, Y. H. J. Org. Chem., 2011, 76, 10011.