Methylene Meldrum’s Acid Derivatives of Indoxyl and Their Cyclization Reactions under Flash Vacuum Pyrolysis Conditions

Abstract

Pure indoxyl can be obtained in 75% yield by flash vacuum pyrolysis (FVP) of 2¢-azidoacetophenone at 650 °C. Reaction of indoxyl with methoxymethylene Meldrum's acid takes place at the 1-position, and FVP of the resulting derivative provides 1-hydroxy-9H-pyrrolo[1,2-a]indol-9-one (54%). FVP of the isomeric 2methylene compound gives pyrano[3,2-b]indol-2(5H)-one (42%).