Synthesis of the first 4-oxobutane-1,1,2,2-tetracarbonitriles containing a phenol fragment and their transformation into cyano-substituted pyrrol-2-ones showing three-position molecular switching.

The first example of the synthesis of 4-oxobutane-1,1,2,2-tetracarbonitriles (OTCs) containing a phenolic moiety has been described. The synthesis is based on the reaction between tetracyanoethylene and 4-hydroxyphenyl-substituted ketones under mild conditions. Due to the presence of a phenolic hydroxyl group, these compounds are more functionalized derivatives of the well-known OTC substrates used for diversity-oriented synthesis (DOS). The preserved synthetic potential of the OTCs for the preparation of phenol-containing derivatives with enhanced capabilities for tuning optical properties has been shown using the targeted synthesis of 2-(2-oxo-1,2-dihydro-3H-pyrrol-3-ylidene)malononitriles. Based on the obtained pyrroles and a model amine (pyrrolidine) a previously unknown type of thermosensitive three-position molecular switch is described. Reversible color changes of the dye are shown in both solution and on filter paper. The results reveal a new research branch of the OTC-based DOS strategy to access functionalized phenol-containing derivatives.