Variations in the Blaise Reaction: Conceptually New Synthesis of 3‐Amino Enones and 1,3‐Diketones

Organic compounds with 3‐amino enone or 1,3‐diketone functional groups are extremely important, as they can be converted into a plethora of heterocyclic or carbocyclic compounds, or can be used as ligands in metal complexes. We have achieved a new, easy, straightforward and convenient synthesis of 3‐amino enones and 1,3‐diketones starting from aryl/heteroaryl/alkyl nitriles and 1‐aryl/alkyl 2‐bromoethanones. The reaction is a variation of the classical Blaise reaction, and it works with zinc and trimethylsilyl chloride as an activator. By running the hydrolysis of the reaction intermediate with HCl (3 n aq.) at 0–30 °C or at 100 °C, it is possible to form either 3‐amino enones or 1,3‐diketones, respectively. The newly developed method was used for the synthesis of avobenzone, an ingredient of sun‐screen lotions. Furthermore, an easy synthesis of ( Z )‐3‐amino‐1‐[4‐( tert ‐butyl)phenyl]‐3‐(4‐methoxyphenyl)prop‐2‐en‐1‐one, with UV/Vis absorption characteristics similar to those of avobenzone, was also achieved.