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I have been asked to suggest a synthesis for the following compound (tetralin) from benzene:

Structure of tetralin

I am unsure how to do this. It surely can't be Friedel–Crafts alkylation because of carbocation rearrangement and polyalkylation, right? Possibly a double acylation followed by a double reduction? Is there an issue with this; maybe a competing aldol type reaction in the double acyl chloride reagent that would be required.

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  • $\begingroup$ Your idea with acylation is good imo $\endgroup$ – Mithoron Nov 26 '15 at 18:10
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    $\begingroup$ So many catalysts have been derived for selective hydrogenation of naphthalene to form that; why should one bother starting from benzene? ;) $\endgroup$ – Jan Nov 26 '15 at 20:23
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You've got it right, double acylation and double reduction - but the first reduction occurs after the first acylation. FWIW, the name of the reaction is the Haworth reaction and is commonly used to synthesize substituted tetralins, naphthalenes and higher aromatic polycyclics.

In your particular case, here is a diagram of the first 3 steps in the reaction

enter image description here

  • Friedel-Crafts acylation of benzene with succinic anhydride
  • reduction of the ketone using a Wolff-Kishner or Clemmensen reduction
  • a second Friedel-Crafts acylation using strong acid; it is an internal cyclization and forms the needed ring
  • and finally (not shown in the above diagram) a second Wolff-Kishner or Clemmensen reduction of the resultant tetralone to produce the desired tetralin
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  • $\begingroup$ Why cant both Friedel-Craft additions be done before the reduction? $\endgroup$ – RobChem Jan 9 '16 at 17:29
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    $\begingroup$ Friedel-Crafts alkylation and acylation reactions do not take place (at least not in good yield) with a deactivated aromatic ring. Once the first acylation occurs, the ring becomes deactivated by the attached ketonic carbonyl. In fact, this is one of the advantages of the F-C acylation reaction over the alkylation reaction. In the acylation case, only one acyl group can attach before deactivation stops the reaction. In the alkylation case, the ring becomes more activated and undesired polyalkylation often results. $\endgroup$ – ron Jan 9 '16 at 18:08

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