Sciencemadness Discussion Board

1,2-benzoquinone

morsagh - 1-11-2016 at 03:50

I want to do some hetero diels-alder reaction with 1,2-benzoquinone acting as diene to produce substituted dioxane ring. Will this reaction work? What should be used as catalyst and solvent (I was thinking of ZnCl2 in xylene). Second, can be catechol oxidised by NaClO to 1,2-benzoquinone in good yelds or should be used some weaker oxidising agent.

Boffis - 1-11-2016 at 09:09

I am not sure about the Diels-Alder reaction but preparing un-substituted o-benzoquinone requires anhydrous condition to get a good yield, I am not sure of the exact conditions but silver oxide is the usual oxidant for laboratory isolation of o-benzoquinone from catechol. However, looking at this paper various other oxidants are mentioned:

Hypochlorite certainly does not give workable yields of quinone in aqueous conditions.

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[Edited on 1-11-2016 by Boffis]

CuReUS - 2-11-2016 at 02:54

Quote: Originally posted by morsagh  
I want to do some hetero diels-alder reaction with 1,2-benzoquinone acting as diene to produce substituted dioxane ring. Will this reaction work?

Firstly,I think you want to make a dioxin,not a dioxane.Secondly,whether the diels alder reaction will work or not depends on your alkene
Quote:
as a highly reactive 8π-electron system, o-quinones display two 4π components as potential sites for Diels–Alder reactions.The selectivity between sites results from the polarizability of the complementary 2π component. For example, polarized alkenes such as enamines add to the external dione to restore aromaticity and yield a dioxin,while less polarized alkenes such as styrene add to the cyclohexadiene portion to yield a [2.2.2]bicyclooctane

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1557836/
Quote:
1,2-Benzoquinone is produced on oxidation of catechol exposed to air in aqueous solution

https://en.wikipedia.org/wiki/1,2-Benzoquinone
wiki gives the above paper as a reference for the oxidation but I couldn't find it mentioned anywhere in that paper.

morsagh - 2-11-2016 at 05:40

I´ve got good dienophille, i am more worried about oxidation of catechol to o-benzoquinone, why shouldn´t NaClO catalysed by Fe3+ work?