DIARYL ETHYLENES AS ORGANIC LUMINOPHORES: SIMPLY SYNTHESIS VIA WITTIG REACTION

Abstract

Organic luminophores are widely applied in various fields of technology, industry, medicine, scientific research, etc. Therefore, the search for new compounds with appropriate properties, as well as the development or improvement of methods for synthesising already known classes of substances with luminescent properties remains relevant. Diarylethylenes are one of the important groups of organic luminophores. However, their synthesis often requires the application of complex, multi-stage methods and expensive reagents, which negatively affects the economic feasibility of their application. Therefore, developing simple and affordable methods for obtaining this class of compounds is an important task for chemists and technologists. Among the relatively simple methods for obtaining 1,2-diaryl-substituted ethene derivatives with the formation of a С——С double bond, the Wittig reaction – an interaction between alkylidenephosphoranes (phosphorus ylides) and aldehydes – can be specifically mentioned. The disadvantage of this method, however, is the instability of many alkylidenephosphoranes, some of which cannot be isolated in the pure state at all. The aim of this work is to develop the simplest possible method for the synthesis of diarylethylenes by the Wittig reaction based on phosphonium salts, which does not involve the isolation of intermediate products – phosphorus ylides in the pure state. An interaction between benzylic phosphonium salts and aromatic aldehydes in a single-phase or two-phase system using triethylamine or aqueous NaOH as a base has been investigated. The method eliminates the necessity for isolating and purifying the intermediate product – phosphorylide – which significantly simplifies the synthesis procedure. The application of the developed method allowed the synthesis of a number of new 1,2-diarylethylenes, particularly those containing a benzophenone fragment, as well as compounds containing condensed aromatic systems such as naphthalene and anthracene. Solutions of all obtained substances demonstrate strong blue fluorescence when irradiated with UV light, confirming the potential for their further investigation in this direction.