11
$\begingroup$

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.

Improve this question
$\endgroup$
2
  • $\begingroup$ Your idea with acylation is good imo $\endgroup$
    – Mithoron
    Nov 26, 2015 at 18:10
  • 1
    $\begingroup$ 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, 2015 at 20:23

1 Answer 1

Reset to default
10
$\begingroup$

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
Improve this answer
$\endgroup$
2
  • $\begingroup$ Why cant both Friedel-Craft additions be done before the reduction? $\endgroup$
    – RobChem
    Jan 9, 2016 at 17:29
  • 3
    $\begingroup$ 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, 2016 at 18:08

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.