title: A novel approach to isoindolo[2,1-a]indol-6-ones.
abstract: A convenient route to isoindolo[2,1-a]indol-6-ones has been developed starting from the appropriate 2-(N-phthaloyl)benzoic acids. Formation of the acid chlorides with thionyl chloride followed by heating with triethyl phosphite in a suitable solvent resulted in a multistep reaction giving tetracyclic β-ketophosphonates that on reduction with sodium borohydride gave the required indolones in good overall yields. Analogous β-ketophosphonates were also prepared starting with N,N-(1,8-naphthaloyl)-2-aminobenzoic acid and 2-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)benzoic acids although of these only the naphthaloyl product could be reduced with sodium borohydride without cleaving the amide bond in the ring system.
authors.affiliation: School of Biological and Chemical Sciences, Queen Mary University of London, London E1 4NS, UK.
authors.forename: Philip
authors.initials: P
authors.lastname: Duncanson
authors.forename: Yuen-Ki
authors.initials: YK
authors.lastname: Cheong
authors.forename: Majid
authors.initials: M
authors.lastname: Motevalli
authors.forename: D Vaughan
authors.initials: DV
authors.lastname: Griffiths