Novel rearrangement in the reaction of 5-methyl-5Hiso-indolo [2,1-a]benzimidazole with maleimide derivatives. Stereochemical and X-ray structural study

Abstract

In the reaction of 5-methyl-5H-isoindolo[2,1-a]benzimidazole 2 with N-arylmaleimides 3a-f a novel unexpected rearrangement led to the 3-A three-step mechanism including Michael addition, Diels-Alder reaction and skeletal rearrangement of tricyclic 7-azanorbornene derivatives 5a-f is proposed to explain the formation of the final products. An X-ray structure analysis of compound 6a shows the presence of a twisted double bond with a torsion angle of 6.42°. In the 1 H NMR spectra the presence of a chirality center and axis in the adducts 6a-f implies the presence of atropodiastereomers.

Synthesis and Fluorescence Properties of 4-aminobenzo[f]Isoindole Derivatives

“…Diels-Alder adducts derived from fused azino-and azoloisoindoles with maleimides undergo further rearrangements and form compounds with addends in both a 1:1 and 1:2 ratio, that possess intriguing properties. [9][10][11][12] Reaction of 2,4-dimethylpyrimido[2,1-a]isoindole with a variety of maleimides gives derivatives of 4-aminobenzo[f] isoindole which exhibit notably strong fluorescence. 12 In the current research, we developed a new synthetic route to the latter compounds, giving better yields and easier to implement than the existing one.…”