The first example of unusual reversible nucleophilic addition to 2-(5-aryl-2-oxo-3H-pyrrol-3-ylidene)malononitriles – a new tool for the creation of thermosensitive molecular switches

Abstract

An unusual transformation of 2-(5-aryl-2-oxo-3H-pyrrol-3-ylidene)malononitriles occurring through a nucleophilic addition to the C5 atom of the heterocycle is described. The observed process is reversible and characterized by a contrasting color...

Thermoreversible Transformations of the Cyanosubstituted 2‐Oxopyrrole Derivative by the Action of Amines for the Creation of Novel High‐Contrast Coloration/Decoloration Systems

“… Reversible transformation of pyrroles A into salts B by the action of morpholine [31] and objects of the present study 1 .…”

“…The data obtained indicate that, depending on the amine nature, the transformation of salts 1 into OP can be either completely or partially thermoreversible. Compounds 1 based on branched aliphatic amines ( 1 f , g ) and cyclic amines with an additional heteroatom ( 1 h – j ) are prone to completely reversible transitions (the reversibility for the salt 1i formation was reported previously [31] ). In turn, salts 1 a – e , containing fragments of cyclic amines at the C5 atom of pyrrole, do not exhibit a complete thermal return to OP (Figures S1–S11 in ESI).…”

“…Recently, representatives of a novel group of molecular switches based on cyano‐substituted 2‐oxopyrroles A were reported in the scientific literature (Figure 1). [31] For compounds A , the ability to reversibly interact with morpholine was shown, as a result of which unusual ionic compounds of type B were synthesized. For the A ⇌ B system in solution, the possibility to shift the equilibrium by changing temperature was described, in particular, heating had increased the fraction of pyrrole A .…”

“…In all cases, according to spectral data, the structure of the final product contained two fragments of the same amine (Scheme 2). Also, the previously reported [31] morpholine salt 1i was synthesized for comparison of the properties of new compounds 1 .…”

“…From the data presented in the previous work [31] and Figure 1 it follows that a detailed study of more diverse variants of A⇌B transformations is of separate research interest. In particular, a series of fundamental issues are still unsolved for this system, namely:…”