Carboxylate-assisted ruthenium(II)-catalyzed C-H arylations of 5-aryl tetrazoles: step-economical access to Valsartan

Carboxylate assistance was key to success for highly efficient ruthenium-catalyzed direct ortho-arylations of tetrazolyl-substituted arenes with aryl halides and triflates in the absence of phosphine ligands. Thus, ruthenium(II) biscarboxylates allowed for C-H bond functionalizations with excellent chemo- and site-selectivities, which set the stage for an atom- and step-economical access to key angiotensin-II-receptor blockers. Mechanistic studies revealed the C-H bond metalation to be reversible, and were suggestive of a rate-determining reductive elimination.