Pyrrolocoumarins. 1. Synthesis and Spectroscopic Investigation of 7-Oxo- and 1,2,7-Trioxo-1,2-dihydropyrano-[3,2-e]indole and Their Derivatives

A preparative route is proposed for the synthesis of the novel heterocyclic systems 7-oxo- and 1,2,7-trioxo-1,2-dihydropyrano[3,2-e]indole using classical Fischer and Sandmeyer methods respectively. We have studied various conditions for cyclization of the starting coumarin 6-isonitrosoacetamide and the methyl or ethyl pyruvate 6-coumarinylhydrazones. The syn- and anti-form ratio of the latter and the structure of all of the synthesized compounds were determined using spectroscopic data analysis.Dedicated to the memory of a dear teacher, the prominent Russian science professor Nikolai Nikolaevich Suvorov. Founder of indole chemistry in Georgia. In love with, and a warm favourite of, Georgia.__________Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 238–245, February, 2005.