Strain-induced reactivity effects in the reaction of 2,5-dihydroxy-[1,4]-benzoquinone with diamines

Hubert Hettegger, Andreas Hofinger, Thomas Rosenau*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

2 Citations (Scopus)
3 Downloads (Pure)


The regioselectivity of the reaction of 2,5-dihydroxy-[1,4]-benzoquinone (DHBQ) with diamines could not be explained satisfactorily so far. In general, the reaction products can be derived from the tautomeric ortho-quinoid structure of a hypothetical 4,5-dihydroxy-[1,2]-benzoquinone. However, both aromatic and aliphatic 1,2-diamines form phenazines, in some cases, formally by diimine formation on the quinoid carbonyl groups, and in other cases, the corresponding 1,2-diamino-[1,2]-benzoquinones by nucleophilic substitution of the OH groups; the regioselectivity apparently does not follow any discernible pattern. The reactivity was now explained by an adapted theory of strain-induced bond localization (SIBL). Here, the preservation of the "natural" geometry of the two quinoid C–C double bonds (C3=C4 and C5=C6) as well as the N–N distance of the co-reacting diamine are crucial. A decrease of the annulation angle sum (N–C4–C5 + C4–C5–N) is tolerated well and the 4,5-diamino-ortho-quinones, having relatively short N–N spacings, are formed. An increase in the angular sum is energetically unfavorable, so that diamines with a larger N–N distance afford the corresponding ortho-quinone imines. Thus, for the reaction of DHBQ with diamines, exact predictions of the regioselectivity and the resulting product structure can be made on the basis of simple computations of bond spacings and product geometries.

Original languageEnglish
Pages (from-to)529-538
Number of pages10
JournalCurrent Organic Chemistry
Issue number4
Publication statusPublished - 2021
MoE publication typeA1 Journal article-refereed


  • Amines
  • Benzoquinones
  • DHBQ
  • Diamines
  • Regioselectivity
  • SIBL theory


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