Synthesis and hydroamination catalysis with 3-aryl substituted pyrrolyl and dipyrrolylmethane titanium(iv) complexes

Abstract

Using an iridium-catalyzed borylation/Suzuki–Miyaura coupling sequence several 3-aryl-pyrroles were accessed; in addition, dipyrrolylmethanes incorporating these 3-arylpyrroles were synthesized. Using the monodentate pyrrolyls, Ti(NMe₂)₂(HNMe₂)(pyr^3,5-CF3)₂ (1) and a 2,4-diarylpyrrolyl complex Ti(NMe₂)₃(pyr^Ar/Ar′) (2) were prepared and structurally characterized. Titanium species bearing the new dipyrrolylmethane ligands Ti(NMe₂)₂(NHMe₂)(dpm^3,5-CF3) (3) and Ti(NMe₂)₂(NHMe₂)(dpm^F3) (4) were also generated. Kinetics under pseudo-first order conditions with 3 and 4 showed them to be measurably more active than the parent derivative without the electron-withdrawing aryl groups.