Synthesis and reactions of 11H-benzo[b]pyrano[3,2-f]indolizines and pyrrolo[3,2,1-ij]pyrano[3,2-c]quinolines

2-Methyl-3H-indoles 1 cyclize with two equivalents of ethyl malonate 2 to form 4-hydroxy-11H-benzo[b]pyrano[3,2-f]indolizin-2,5-diones 3, whereas 2-methyl-2,3-dihydro-1H-indoles 9 give under similar conditions regioisomer 8-hydroxy-5-methyl-4,5-dihydro-pyrrolo[3,2,1-ij]pyrano[3,2-c]quinolin-7,10-diones -10. The pyrone rings of 3 and 9 can be cleaved either by alkaline hydrolysis to give 7-acetyl-8hydroxy-10H-pyrido[1,2-a]indol-6-ones 4 or 5-acetyl-6-hydroxy-2-methyl-1,2-dihydro-4H-pyrrolo[3,2,1-ij]quinolin-4-ones 11, respectively. Chlorination of 3 and 9 with sulfurylchloride gives under subsequent ring opening 7-dichloroacetyl-8-hydroxy-10H-pyrido[1,2-a]indol-6-ones 5 or 5-dichloracetyl-6-hydroxy-2-methyl-1,2-dihydro-4H-pyrrolo[3,2,1-ij]quinolin-4-ones 12. The dichloroacetyl group of 5 can be reduced with zinc to 7-acetyl-8-hydroxy-10H-pyrido[1,2-a]indol-6-ones 7. Treatment of the acetyl compounds 4, 7 and 11 with 90% sulfuric acid cleaves the acetyl group and yields 8-hydroxy-10H-pyrido[l,2-a]indol-6-ones 6 and 8, and 6-hydroxy-2-methyl-1,2-dihydro-4H-pyrrolo[3,2,1-ij]quinolin-4-ones 13. Reaction of dichloroacetyl compounds 12 with sodium azide yields 6-hydroxy-2-methyl-5-(1H-tetrazol-5-ylcarbonyl)-1,2-dihydro-4H-pyrrolo[3,2,1-ij]quinolin-4-ones 14 via intermediate germinal diazides.