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

Abstract

A new efficient approach to the synthesis of intensely colored 2‐(2‐oxo‐3H‐pyrrol‐3‐ylidene)malononitrile (OP) was developed. Using the reaction of OP with amines, a series of previously unknown colorless organic salts – dicyano(2‐oxo‐2,5‐dihydro‐1H‐pyrrol‐3‐yl)methanides were synthesized, bearing in the structure two fragments of same or diverse amines of different nature (covalent and ionic). TGA‐DTA study of the synthesized salts showed a thermal reversibility of their formation. The introduction of violet OP into paper followed by treatment with amine vapors revealed prospects of using such a system for naked‐eye detection of volatile amines. It was also shown that OP‐based rewritable paper can be created, to which a data can be applied by local heating and erased by the action of amine or temperature.

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

“…It should be noted that, in contrast to our previous work, 38 the isolation of the forms 2a-C5 and 2a-Q for compound 2a turned out to be impossible. We associate this with the presence of an electron-donating OH group in the structure of 2a , which slightly deactivates the C5 atom of the pyrrole ring for nucleophilic addition compared to an analogue of 2a without an OH group.…”

“…Moreover, structures F were successfully isolated as salts and could be thermally converted into analogues of pyrroles 2 without the OH moiety. 38 We also experimentally confirmed that the process of iminofuran C rearrangement into lactam 2 did not occur without an intermediate nucleophilic addition. For this, OTC 1a was treated with N -methylmorpholine under the same reaction conditions, but the formation of compound 2a was not observed.…”

“…1, structure 2 , directions I and II for nucleophile attack). In this regard, it should be noted that for an analogue of compound 2a without an OH group in the structure, 38 the ability for binary (two-color) molecular switching as a result of an amine addition to the C5 atom of the pyrrole (direction II, Fig. 1) was reported.…”

“…One of the well-known DOS platforms is tetracyanoethylene adducts with ketones, namely 4-oxoalkane-1,1,2,2-tetracarbonitriles (OTCs) 24–40 (Fig. 1).…”

“…In total, more than twenty directions of OTC transformations have been described in the literature. Moreover, among the products of their transformations, compounds with antitumor activity, 26 molecular switches, 25,27,38 efficient fluorophores 30 (including solid-state ones 31 ), fluorescent sensors 32 and coordination polymers 39,40 have been found.…”