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

• Published in: European journal of organic chemistry Vol. 2015; no. 7; pp. 1525 - 1532
• Main Authors: Rao, H. Surya Prakash, Muthanna, Nandurka
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01.03.2015; WILEY‐VCH Verlag; Wiley; Wiley Subscription Services, Inc
• Subjects: Chemistry; Chemistry, Organic; Condensation reactions; Cyanides; Halides; Ketones; Physical Sciences; Science & Technology; Zinc; Condensation reactions; Ketones; TANDEM; ENAMINONES; Halides; ONE-POT SYNTHESIS; NITRILES; EFFICIENT SYNTHESIS; CHEMISTRY; Cyanides; DERIVATIVES; Zinc
• ISSN: 1434-193X; 1099-0690
• DOI: 10.1002/ejoc.201403402

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. A variety of aryl/heteroaryl/alkyl nitriles were converted into 3‐amino enones or 1,3‐diketones by reaction with 2‐bromoethanones in the presence of zinc under Blaise reaction conditions. The commercially important product avobenzone was synthesized.