Redox neutral [4+2] benzannulation of dienals and tertiary enaminones for benzaldehyde synthesis

By employing the featured amine elimination of tertiary enaminones as a key transformation, cascade reactions of dienals and tertiary enaminones involving [4+2] annulation, Hofmann-like amine elimination and aromatization are devised for benzaldehyde synthesis. This method is of particular interest in providing benzaldehydes containing an electron withdrawing group at the C3 position which are hard to access by previous methods for benzaldehyde synthesis.