Use of Enamines as Light Protection Agents

Habeck etal, US Patent 6,603,014 (August 5, 2003) Assignee BASF Aktiengesellschaft Utility UV-A Absorbers in Cosmetic Preparations 

Methyl 2,2-bismethylmercapto-l-cyanoacrylate (0.1 mol) and 2- mercaptoaniline (0.1 mol) were stirred overnight in 100 ml ethyl alcohol at ambient temperature. The precipitate that formed was filtered, dried, and the product isolated in 87% yield as a white powder. 

The product from Step 1 (250 mmol) was dissolved in 50 ml DMF, mixed with K2CO3 (250 mmol) and 1-bromhexane (250 mmol) then refluxed 1 hour. Thereafter 50 ml water was added and the precipitate isolated by filtration in 63% yield. 

In a subsequent investigation by the author Step 2 analogues (1), UV-A enamine sulfonic acid derivatives, (I), and (II), were prepared and are described (I). 

Alkyl-j8,j8-diphenyl acrylates and a-cyano-j8,j8-diphenyl acrylates, (III), have also been effective as UV-A absorbers and their preparation is provided (2). 

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