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

2‐Methyl‐3 H ‐indoles 1 cyclize with two equivalents of ethyl malonate 2 to form 4‐hydroxy‐11 H ‐benzo[ b ]pyrano[3,2‐ f ]indolizin‐2,5‐diones 3, whereas 2‐mefhyl‐2,3‐dihydro‐1 H ‐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‐8‐hydroxy‐10 H ‐pyrido[1,2‐ a ]indol‐6‐ones 4 or 5‐acetyl‐6‐hydroxy‐2‐methyl‐1,2‐dihydro‐4 H ‐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‐10 H ‐pyrido[1,2‐ a ]indol‐6‐ones 5 or 5‐dichloracetyl‐6‐hydroxy‐2‐methyl‐1,2‐dihydro‐4 H ‐pyrrolo[3,2,1‐ ij ]quinolin‐4‐ones 12 . The dichloroacetyl group of 5 can be reduced with zinc to 7‐acetyl‐8‐hydroxy‐10 H ‐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‐10 H ‐pyrido[1,2‐ a ]‐indol‐6‐ones 6 and 8 , and 6‐hydroxy‐2‐methyl‐1,2‐dihydro‐4 H ‐pyrrolo[3,2,1‐ ij ]quinolin‐4‐ones 13 . Reaction of dichloroacetyl compounds 12 with sodium azide yields 6‐hydroxy‐2‐methyl‐5‐(1 H ‐tetrazol‐5‐ylcarbonyl)‐1,2‐dihydro‐4 H ‐pyrrolo[3,2,1‐ ij ]quinolin‐4‐ones 14 via intermediate geminal diazides.