De Novo Construction of Benzene Ring: Synthesis of 2,4,6‐Trisubstituted Benzophenones Using NaH Promoted Cascade Reaction of Arylmethyl Ketone and Aromatic Aldehyde

Abstract Benzannulation is one of the most important methods to construct the simplest aromatic ring, i.e., benzene ring. Various efforts to synthesize benzene derivatives were already made, but they generally require some transition metal species in stoichiometric or catalytic amounts to carry out this transformation which contaminates with metal‐based impurity. On the other hand, the reactant, i.e., alkyne used for these transformations is also quite expensive in nature. Keeping these facts in mind, a series of 2,4,6‐trisubstituted benzophenones (vis‐à‐vis 1,2,4,6‐tetrasubstituted benzenes) were synthesized under transition metal and solvent free conditions using simple chemicals arylmethyl ketones, aromatic aldehydes, and sodium hydride. The beauty of this methodology is that 4 out of 6 σ and all 3 π bonds of benzene ring were generated within one reaction vessel. Using this methodology, 2,4,6‐trisubstituted benzophenones bearing aromatic and heterocyclic groups can be readily accessed.