A New Method for the Synthesis of Substituted 8,9,10,11-Tetrahydroindolo[1,2-a]Quinoxalin-6(5H)-Ones

Recent Advances in the Synthesis of Indoles with Partially Hydrogenated Benzene Ring (Tetrahydroindoles)

“…The reactions of enamines 127a,b, 134a,b, and 138 with ethyl bromopyruvate (141) were carried out in a similar way with the previous studies 75, 78 in a boiling solution of 1,4-dioxane. 80 The reactions are fully complete in 4 hours of boiling. It should be noted that in the case of the reaction of 1-(1-morpholino)cyclohexene ( 138) with ethyl 3-bromopy-ruvate (141), as well as in case of the reactions of enamines 127a,b and 134a,b, with arylchloropyruvates 128, which occur with the formation of substituted 4,5,6,7-tetrahydroindoles as the main products, salts of pyrrolidinium chloride, piperidinium and morpholinium bromide 140b are formed with up to 10% yield along with the main product of the reaction -4,5,6,7-tetrahydroindole derivative 142e (82% yield) (Scheme 41).…”

“…Boiling the latter with chloranyl in xylene for 50 hours leads to 7-phenylindolo[1,2-a]quinoxalin-6(5H)-one (149) as a result of oxidative dehydrogenation (Scheme 45). 80 Thus, a new simple one-reactor method for the synthesis of tetrahydroindolo[1,2-a]quinoxalin-6(5H)-ones and the conditions for their aromatization has been developed. The method is based on a two-stage process involving the alkylation reaction of 3-(-chlorobenzyl)quinoxalin-2(1H)ones 146 and 3-(cyclohexen-1-yl)pyrrolidines 127 by Stork and subsequent annulation of the tetrahydroindole cycle in the intermediate chlorides of 1-{2-[aryl(3-oxo-3,4-dihydroquinoxalin-2-yl)methyl]cyclohexylidene}pyrrolidinium, accompanied by the release of pyrrolidinium chloride.…”

“…Mamedov et al 80 also reported the reaction of 3-(α-chlorobenzyl)quinoxalin-2(1 H )-ones 146 with 1-(cyclohexen-1-yl)pyrrolidines 127 to produce 8,9,10,11-tetrahydroindolo[1,2- a ]quinoxalin-6(5 H )-ones 148 via a tandem sequence of Stork enamine alkylation and intramolecular annulation (Scheme 44 ). Replacing the aryl groups in the parent quinoxalin-2(1 H )-ones with hexyl one allows to synthesize the corresponding 8,9,10,11-tetrahydroindolo[1,2- a ]quinoxalin-6(5 H )-one, but in a relatively low yield.…”

“…The reaction of 3-(1-chloroheptyl)quinoxalin-2(1 H )-one ( 146 ; R 1 = n -Hex, R 2 = R 3 = H) with 1-cyclohexenylpyrrolidine ( 127a ) in 1,4-dioxane and DMF under different temperature conditions leads to a mixture of products, and in boiling acetonitrile proceeds to form the mainly desired product 148 (R 1 = n -Hex, R 2 = R 3 = R 4 = H) in 54% yield. 80 The formation of 8,9,10,11-tetrahydroindolo[1,2- a ]quinoxalin-6(5 H )-ones 148 is explained by the nucleophilic attack of the N-4 atom at the electrophilic carbon atom of the imminium group of the Stork alkylation product 147 , accompanied by the closure of the pyrroline cycle, which leads to the intermediate A , which under the reaction conditions through the intermediate B is aromatized by eliminating pyrrolidinium chloride (Scheme 44 ).…”

Environmentally friendly and efficient method for the synthesis of the new α,α′‐diimine ligands with benzimidazole moiety

“…There are few papers in the literature on molecules that combine the phenanthroline or bipyridine moieties with the phenazine, quinoxaline, and tetraazanaphthacene units, but none with the benzimidazole moiety. In connection with our interest in the synthesis of fused and biheterocyclic systems, we present here the synthesis and complete characterization of the new polyheterocyclic compounds, namely the first examples of oxa(thia)diazolo[3,4‐ f ]‐ and pyrazino[2,3‐ f ]quinoxalines with the benzimidazole moiety and two new heterocyclic systems—benzo[4′,5′]imidazo[1′,2′:1,2]quinolino[3,4‐ b and 4,3‐ b ][1,2,5]oxadiazolo[3,4‐ f ]quinoxalines.…”