Switchable cyclopalladation of substrates containing two directing groups: on the way to non-symmetrical [2.2]-dipalladaparacyclophanes

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.