Reaction of cis ‐3‐bromo‐1,2‐dibenzoylpropene with amines

The reaction of cis ‐3‐bromo‐1,2‐dibenzoylpropene (1) with amines proceeds by means of a substitution‐rearrangement attack to give the 2‐(α‐aminoacetophenonyl)acrylophenones ( 2 ). Like similar structures, 2 undergoes further substitution‐rearrangement by amines to give 3‐benzoyl‐5‐phenylpyrroles ( 5 ) and an enaminoketone, α‐acetophenonyl‐β‐aminoacrylophenone ( 3 ). Competitive with substitution‐rearrangement, amine addition to 2 followed by loss of hydrogen and then water leads to formation of the 3‐benzoyl‐4‐amino‐5‐phenylpyrroles ( 4 ). The enaminoketones ( 3 ) by contrast with 2 are quite stable. Structure 2 when in polar solvents or in the presence of amines undergoes substitution‐rearrangement to give 3 , which can be induced to give the pyrroles ( 5 ) when exposed to acid conditions. When neat or in solvents of low polarity, 2 undergoes intermolecular substitution‐rearrangement‐dehydration to give 5 almost exclusively. A novel addition reaction of 3‐benzoyl‐5‐phenylfuran involving attack by isopropyl‐ or cyclohexylamine provides a quantitative method of synthesizing the appropriate N ‐substituted examples of 3 and an efficient method of deriving the corresponding pyrroles ( 5 ).