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-12 H -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-(1 H -Indol-3-yl)-12 H -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 12 H -chromeno[2,3- c ]isoquinolin-5-amines and reversible fluorescence quenching under acidic conditions.