Korábková T, Bartáček J, Marek L, Hanusek J, Růžička A, Váňa J. Switchable cyclopalladation of substrates containing two directing groups: on the way to non-symmetrical [2.2]-dipalladaparacyclophanes.
Dalton Trans 2023;
52:11113-11119. [PMID:
37493412 DOI:
10.1039/d3dt02019c]
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Abstract
Simple switching of the site-selectivity of C-H activation reactions of substrates containing multiple directing groups is particularly important for the so-called late stage functionalization synthetic approach. In this work, we verified the possibility of achieving this by adding acids of different strengths. Using a substrate containing two differently strong (and basic) directing groups, the influence of the addition of acids on the regioselectivity of the C-H activation step of the reaction with palladium acetate was thoroughly studied. The addition of no or weak acids results in cyclopalladation being controlled by a stronger directing group. However, the addition of a strong acid causes protonation of this group and the reaction is then controlled by a weaker directing group. Finally, this approach enables double C-H activation leading to a unique class of compounds: "non-symmetrical" [2.2]-dipalladaparacyclophanes.
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