BISINDOLES. 43. DIPYRROLOQUINOXALINES. 2. SYNTHESIS OF THE BIS-ANALOGS OF THE FISCHER ALDEHYDE UNDER VILSMEIER CONDITIONS

Abstract

The Vilsmeier formylation of bifunctional Fischer base analogs in the dipyrrolobenzoquinoxaline and indoloindole series was studied with various substrate–Vilsmeier complex ratios. The isomeric Fischer bases of the indoloindole series were formylated smoothly with the formation of the corresponding diformyl derivatives: 2,7-di(formylmethylidene)-1,3,3,6,8,8-hexamethylindolino[7,6-g]indoline and 2,9‑di(formylmethylidene)-1,1,3,8,10,10-hexamethylindolino[4,5-e]indoline. In the case of 1,4,5,8-tetrahydro-1,1,8,8-tetramethyl-2,7-dimethylidenebenzo[g]dipyrrolo[1,2,3-de:3,2,1-ij]quinoxaline reaction at 35°C with a large excess of the Vilsmeier complex (1:45), the diformyl derivative 2,7-di(formylmethylidene)-1,4,5,8-tetrahydro-1,1,8,8-tetramethylbenzo[g]dipyrrolo[1,2,3-de:3,2,1-ij]quinoxaline was obtained with a 67% yield. At 60°C and reagent molar ratio of 1:5, a cyanine dye of unknown structure was evidently formed.

Authors: Sh. A. Samsoniya, M. V. Trapaidze, and N. N. Nikoleishvili

English Translation in Chemistry of Heterocyclic Compounds, 2013, 49 (4), pp 540-544

http://link.springer.com/article/10.1007/s10593-013-1279-0