A practical route to arylated dihydroacridine derivatives via nickel boride mediated intramolecular reductive cyclization-concomitant dehydration

A facile and highly efficient route towards 3-aryl-1,2-dihydroacridine derivatives from an aldol adduct of o-nitrobenzaldehyde and cyclohexenone derivatives has been described. In situ generated nickel boride was found to be an excellent reagent to construct the acridine framework via an intramolecular reductive cyclization reaction at ambient temperature under acid-free conditions. The reaction is proved to be compatible from the milligram to multigram scale. Operational simplicity, good yields, a broad substrate scope, and scalability make this protocol a valuable addition to the existing methods for acridine derivatives.