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How do you add a benzene group to cyclic compounds like piperidine, piperazine and phenyl derivatives?

Piperidine

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Piperazine

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You could try halogenation on it (to create partial positive on some carbon ($\large\ce{\delta}$ $^+$)) and then add $\ce{Phenyl\ Magnesium\ Halide\ (Ph-Mg-X)}$(Grignard's reagent) to subtitute halide group on ring nucleophilically with Benzene, although that would be difficult/not feasible to carry out in phenyl derivatives. –  Aditya Sriram Jan 25 '13 at 7:48
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I'd just like to point out that benzylpiperazine is a schedule 9 (banned) substance in Australia and whilst good faith is assumed (nothing wrong with academic interest), people might be loath to address such a specific reaction. –  Richard Terrett Jan 25 '13 at 11:37
    
Your good faith is right I have no intention in synthesising such a compound. This is such a simple curiousity –  Brenton Horne Jan 26 '13 at 1:33
    
Do you mean a compound like this, or this or this ot this, out of piperidine. –  Aditya Sriram Jan 26 '13 at 3:36
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Well, (4) is pretty easy to make, you take Benzyl-halide along with a Lewis Acid(like $\ce{AlCl3}$ or $\ce{FeCl3}$) and since Nitogen is a nucleophile it will easily attack on piperidine on the generated carbocation. By the way (4) is also a benzyl derivative not phenyl derivative –  Aditya Sriram Jan 26 '13 at 5:57
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1 Answer

up vote 3 down vote accepted

Brenton, the term "benzene group" is a bit misleading; it seems that you'd like to add a benzyl group, i.e. $\ce{C6H5-CH2}$.

Typically, these reaction are carried out using freshly distilled benzyl halides. In the case of the diamines, monoalkylation is usually achieved using the bis-hydrochloride of the amine and a stochiometric amount of base, thus keeping one nitrogen atom protected.

Note however, that the Australian regulations, kindly mentioned by Richard Terrett, are likewise true in the EC: 1-benzylpiperazine, an infamous psychoactive party drug, is a controlled substance!

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