Reactions of 3-arylpropenenitriles with arenes under superelectrophilic activation conditions: Hydroarylation of the carbon-carbon double bond followed by cyclization into 3-arylindanones

Reactions of 3-arylpropenenitriles [ArCH[dbnd]CHCN] with arenes [Ar'H] under the superelectrophilic activation conditions with Brønsted superacid TfOH (CF₃SO₃H) or strong Lewis acid AlBr₃ result, first, in the formation of products of hydroarylation of the carbon-carbon double bond, 3,3-diarylpropanenitriles [Ar(Ar’)CHCH₂CN]. Reactions may go further in TfOH leading to 3-arylindanones, as products of intramolecular aromatic acylation by the electrophilically activated nitrile group. Intermediate cationic species, derived at the protonation of the starting 3-arylpropenenitriles onto the carbon of C[dbnd]C bond and the nitrile nitrogen, have been studied by DFT calculation. A plausible reaction mechanism including the formation of highly reactive dications [(Ar)HC⁺–CH₂C⁺ = NH] has been proposed. The obtained 3,3-diarylpropanenitriles have been transformed into pharmaceutically valuable 5-(2,2-diarylethyl)-1H-tetrazoles [Ar(Ar’)CHCH₂Tetr] and 3-diarylpropylamines [Ar(Ar’)CH(CH₂)₂NH₂] by the reactions with NaN₃ and LiAlH₄ correspondingly.