Benzene from cyclopropane-1,2,3-triyltrimethanol in acidic medium

Question

What is the mechanism of the conversion of cyclopropane-1,2,3-triyltrimethanol to benzene in in acidic medium?

After performing E1 thrice I was expecting 1,2,3-trimethylidenecyclopropane to form instead:

I know it's highly strained, but I couldn't adopt any other pathway to reach any other product. Is the triene product not formed at all? If cyclopropane-1,2,3-trione can exist, I think even the triene product can.

This reaction is from my exercise book, couldn't find it on OrgSyn.

This reaction does not show up in Scifinder. The triol is known though: Org Lett, 2007, 9, 2617 DOI:10.1021/ol070707r — Dennis Cao, Jul 10 '18 at 17:01

score 13 · Answer 1 · answered Jul 10 '18 at 07:40

13

I have not written the steps for carbocation formation, simple dehydration. enter image description here

answered Jul 10 '18 at 07:40

Avyansh Katiyar

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The mechanism is plausible, but I think it is still important to emphasise that this reaction is not known. There are zero reports of anybody getting benzene by treating the starting material with acid. Probably somebody made it up. – orthocresol Aug 01 '18 at 06:21
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@ortho With a little foresight into this whole JEE business, you'll know that it's almost definitely made up ;-) – paracetamol Aug 01 '18 at 07:20
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It looks nice on the paper. – mykhal Aug 01 '18 at 12:07
Hey primary cations are too unstable. – Tech kidda Aug 12 '22 at 10:14
@Tech kidda: They may be unstable but that doesn't mean they don't form. I also checked Chem. Absts. NADA! – user55119 Aug 12 '22 at 23:21
The diene could very well lose hydrogen and become aromatic; that would be favourable to ring cation I think. – Shimura Variety Sep 28 '22 at 12:59

score 0 · Answer 2 · answered Aug 17 '23 at 18:58

As per my knowledge, in the second step there should be migration of Hydrogen to form a 3° carbocation and then the double bond will form between the two methanol branches.This will entirely change the product but as per rule the 1° cation has to be further stabilized by shifting of hydrogen.

Benzene from cyclopropane-1,2,3-triyltrimethanol in acidic medium

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