AlBr-Promoted stereoselective hydroarylation of the acetylene bond in 3-arylpropynenitriles by electron-rich arenes: synthesis of 3,3-diarylpropenenitriles.

Reactions of 3-arylpropynenitriles (ArC≡CCN) with electron-rich arenes (Ar'H, benzene and its polymethylated derivatives) under the action of aluminum bromide (AlBr, 6 equiv) at room temperature for 0.5-2 h result in the stereoselective formation of 3,3-diarylpropenenitriles (Ar(Ar')C=CHCN) in yields of 20-64%, as products of mainly hydroarylation of the acetylene bond. The obtained 3,3-diarylpropenenitriles in triflic acid CFSOH (TfOH) at room temperature for 1 h are cyclized into 3-arylindenones in yields of 55-70%.