Reactions of N-Vinylpyrrolidone with Arenes under Superelectrophilic Activation Conditions

Reactions of N-vinylpyrrolidone (1-ethenylpyrrolidine-2-one) with arenes under the action of the Brønsted superacid CF3SO3H (triflic acid, TfOH) or strong Lewis acids AlX3 (X = Cl, Br) at room temperature for 1.5 h afford N-(1-arylethyl)pyrrolidones as products of hydroarylation of the N-vinyl group in 11–85% yields. The key intermediate of this transformation is O,C-diprotonated form of N-vinylpyrrolidone, which is a highly reactive electrophile, according to DFT calculations. In the absence of arenes in TfOH, N-vinylpyrrolidone underwent devinylation to form NH-pyrrolidone.