Utilizing Native Directing Groups: Mechanistic Understanding of a Direct Arylation Leads to Formation of Tetracyclic Heterocycles via Tandem Intermolecular, Intramolecular C–H Activation

A mechanistic study on a direct arylation
using a native picolylamine
directing group is reported. Kinetic studies determined the concentration
dependence of substrates and catalysts, as well as catalyst degradation,
which led to the development of a new set of reaction conditions capable
of affording a robust kinetic profile. During reaction optimization,
a small impurity was observed, which was determined to be a dual C–H
activation product. A second set of conditions were found to flip
the selectivity of the C–H activation to form this tetracycle
in high yield. A catalytic cycle is proposed for the intermolecular/intramolecular
C–H activation pathway.