Novel approach to the synthesis and optical absorption properties of 2-(2-oxo-1,2-dihydro-3H-pyrrole-3-ylidene)malononitriles

Abstract

Two approaches to the synthesis of 2-(2-oxo-5-aryl-1,2-dihydro-3H-pyrrol-3-ylidene)malononitriles (DCAA-pyrroles 1) were implemented. The first one was based on the transformation of 4-oxobutane-1,1,2,2-tetracarbonitriles 2 by the action of morpholine. The second approach was based on the reaction between protected form of 4-oxobutane-1,1,2,2-tetracarbonitriles 2 namely 2,7-dioxabicyclo[3.2.1]octane-4,4,5-tricarbonitriles 3 and morpholine. This approach involving sequential furan and pyran ring-opening of the 2,7-dioxabicyclo[3.2.1]octane moiety with further pyrrole ring-closure, resulted in a smoother formation of DCAA-pyrroles 1. The optical absorption properties of DCAA-pyrroles 1 were studied for the first time. The absorption maxima were observed in the range of 506–545 nm showing positive solvatochromism and dependence on the substituent in aryl moiety.

Graphical Abstract

Keywords:

• Cyano-substitued pyrroles
• dicyanoacrylamide fragment (DCAA)
• 4-oxobutane-1,1,2,2-tetracarbonitriles
• 2,7-dioxabicyclo[3.2.1]octanes
• solvatochromism

Additional information

Funding

The reported study was funded by RFBR according to the research project № 18-33-20268 mol_a_ved. X-Ray studies were carried out in M.V. Lomonosov Moscow State in part of University Program of Development.