Homophtalonitrile for Multicomponent Reactions: Syntheses and Optical Properties of o‐Cyanophenyl‐ or Indol‐3‐yl‐Substituted Chromeno[2,3‐c]isoquinolin‐5‐Amines

Malononitrile is a useful reagent for multicomponent reactions with hundreds of methods developed. In this paper, we suggest α‐(cyano)‐o‐tolunitrile (homophtalonitrile) to work as a vinylogous malononitrile. Thus, a organocatalytic pseudo‐three‐component reaction of homopthalonitrile (2 equiv) and o‐hydroxybenzaldehyde, leading to the diastereoselective formation of 5‐amino‐12H‐chromeno[2,3‐c]isoquinolin‐12‐yl)(cyano)methyl)benzonitriles, was discovered. The possibility to employ other nucleophiles was demonstrated for indoles, and a sequential three‐component reaction of homophtalonitrile, o‐hydroxybenzaldehyde, and (aza)indole, giving 12‐(1H‐Indol‐3‐yl)‐12H‐chromeno[2,3‐c]isoquinolin‐5‐amines, was developed. The photophysical properties of the synthesized compounds have been studied, revealing high fluorescence quantum yields (42–70 %) for indol‐3‐yl substituted 12H‐chromeno[2,3‐c]isoquinolin‐5‐amines and reversible fluorescence quenching under acidic conditions.