Abstract
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.