Convergent Synthesis of Tetradentate Aminopyridine C–H Oxidation Catalysts

Controlling the oxidation of unactivated C(sp3)–H bonds through supramolecular catalyst–substrate interactions has recently enabled site-selective transformations previously considered inaccessible. However, progress has been hampered by lengthy linear syntheses of supramolecular catalysts. Here we present a convergent strategy that directly cross-couples preformed tetradentate aminopyridine ligands with recognition motifs, streamlining access to functional catalysts. Using this approach, we prepared four catalysts, two featuring resorcin4arene (RS) and two bearing calix4arene (CX) units, for substrate recognition using the solvophobic effect in 2,2,2-trifluoroethanol. This convergent synthesis reduces the longest linear sequence from 5 steps to 2 steps (starting from the recognition motif) by shifting from a linear, catalyst-specific synthesis to a modular platform that allows rapid assembly of catalyst libraries using premade, interchangeable building blocks.