Synthesis of indolylquinoline and acridone alkalaids- A green approach

We have described the total syntheses of quinoline alkaloids, which include indoloquinoline, naphthyridine alkaloids like perlolidine and acridone alkaloids. Synthesis of 1-oxo-1,2,3,4-tetrahydrocarbazole was achieved with good yield using conventional and microwave procedure (unconventional energy). The utility of indole-3-butanoic acid and ethyl 4-(1H-indol-3-yl)butanoate were studied by adopting various catalysts and solvents. As our major synthetic targets were the indoloquinoline alkaloids, we have used Vilsmeier Haack reaction to synthesis and Fischer-indole synthesis to synthesize 3-(2-(1H- indol-3-yl)ethyl)-2- chloroquinoline and 2,4-dihydroxy-3-(indol-2-)-yl-quinoline from ethyl 4-(1H-indol-3-yl)butanoate and 3-acyl-2,4-dihydroxy quinoline respectively. Our investigations on the Vilsmeier Haack reaction (conventional and microwave procedure) of 3-acyl-2,4-dihydroxy quinoline ended up with an intermediate 3-(3-chloroprop-2-ene-1-al)-2,4-dichloroquinoline. The synthetic utility 3-(3-chloroprop-2-ene-1-al)-2,4-dichloroquinoline towards the construction of acridone by using Wittig mechanism with ethyl 2- (triphenylphosphoranylidene was documented.