Studies on the syntheses of heterocyclic compounds. Part 676. Synthesis of 1-substituted 7-methoxymitosenes

Abstract

On treatment with lead tetra-acetate in acetic acid, the 2,3-dihydro-1H-pyrrolo[1,2-a]indoles (4)–(8) were selectively acetoxylated at C-1 to give the acetates (13)–(17). The acetates (16) and (17) and 1-acetoxy-2,3-dihydro-7-methoxy-6-methyl-5,8-dioxo-1H-pyrrolo[1,2-a]indole-9-carbaldehyde (27) were hydrolysed to the corresponding alcohols (20), (21), and (28). The alcohols (20) and (21) were oxidised to the 1-ketones (22) and (23), and (28) was chlorinated with methanesulphonyl chloride and lithium chloride in dimethylformamide to give 1-chloro-2,3-dihydro-7-methoxy-6-methyl-5,8-dioxo-1H-pyrrolo[1,2-a]indole-9-carbaldehyde(29). On heating the acetates (13), (14), and (17) in acetic acid, elimination of acetic acid occurred to yield the 3H-pyrrolo[1,2-a]indoles (24)–(26).