Selective Preparation of Fluorescent 1,8-Naphthalimides using Acidic Alumina under Microwave Irradiation

Abstract

7H-benzimidazo[2,1-a]benz [de]isoquinolin-7-one compounds were prepared in a selective manner by reaction between o-phenylenediamines and appropriate 1,8-naphthalenedicarboxylic anhydrides using acidic alumina under microwave irradiation.diamine (1 mmol) and acidic alumina (3g-Merck, 1078) were mixed with grinding. The mixture was irradiated in a 50 ml beaker in a microwave oven for the times indicated in Table 1. At the end of the irradiation, the reaction mixture was cooled to room temperature and extracted with dichloromethane. The extracts were evaporated to dryness and purified by thick layer plate chromatography on silica gel using hexane/ethylacetate (4/1) as eluent.

Solvent‐dependent fluorescence emission in heterocyclic compounds having isoquinoline backbone

“…The 1 H‐NMR chemical shift and the integration values of the mixture of isomers suggest formation of almost an equimolar mixture of the two isomers. In an earlier report, it was suggested that similar reaction under microwave irradiation in the presence of alumina resulted only one isomer [12], but in our case we have failed to obtain pure isomer through the reaction condition described herein, and the isomeric product separation of 3 was not successful. However, the condensation reaction of 3‐nitro‐1,8‐naphthalic anhydride with 1,2‐diaminobenzene under solvothermal condition in acetic acid at 150°C in an autoclave gave only one isomer.…”

“…The compounds 2 and 4 are derived from a planar aromatic ring system, which is derived from 1,8‐naphthalic anhydride [6]. The imides derived from naphthalic anhydride are useful as fluorescence probes, and their applications are decided by the presence of tether connecting two similar or dissimilar molecules [12]. The compounds 2 and 4 have reasonable fluorescence emission properties on excitation at appropriate wavelengths.…”