Well-Defined Mn(II)-complex Catalyzed Switchable De(hydrogenative) Csp -H Functionalization of Methyl Heteroarenes: A Sustainable Approach for Diversification of Heterocyclic Motifs.

Catalytic activities of Mn(I) complexes derived from expensive MnBr(CO) salt have been explored in various dehydrogenative transformations. However, the reactivity and selectivity of inexpensive high spin Mn(II) complexes are uncommon. Herein, we have synthesized four new Mn(II) complexes and explored switchable alkenylation and alkylation of methyl heteroarenes employing a single Mn(II)catalyst. The developed protocol selectively furnishes a series of functionalized E-heteroarenes and C-alkylated heteroarenes with good to excellent yields. Various medicinally and synthetically useful compounds are successfully synthesized using our developed protocol. Various controls and kinetics experiments were executed to shed light on the mechaism,which reveals that α-C-H bond breaking of alcohol is the slowest step.