Electronically and sterically varied tungsten carbonyls applied to the selective dearomatization of N-heteroarenes

Abstract

We report the first tungsten-catalyzed regioselective 1,2-hydroboration of N-heteroarenes using tunable W(0) carbonyl complexes. Catalyst W-1 enables solvent-free reactions with HBpin, delivering N-boryl-1,2-dihydropyridines in up to 99% yield with complete regioselectivity. The method tolerates diverse 4- and meta-substituents but is blocked by ortho-substitution, highlighting steric control. Structural and IR data confirm ligand-dependent electronic tuning of tungsten. Kinetics show near-zero-order in the catalyst and substrate but near-second-order in [HBpin], suggesting a borane-multistep mechanism. Stoichiometric studies support initial substrate coordination to tungsten. This work establishes earth-abundant tungsten as a sustainable alternative to late-transition metals for selective dearomatization under mild conditions.