Isoindolo[2,1-a]indol-6-one—a new pyrolytic synthesis and some unexpected chemical properties

Abstract

Isoindolo[2,1-a]indol-6-one 1 is formed by a sigmatropic shift-elimination-cyclisation cascade by flash vacuum pyrolysis (FVP) of methyl 2-(indol-1-yl)benzoate 7 at 950 degrees C. The dihydro compound 16 is easily obtained by catalytic reduction of 1, but the reaction is very sensitive to steric effects at the 11-position. Attempted ring-opening of 1 in basic methanol provides an equilibrium of isoindolo[2,1-a]indol-6-one 1 and the ester 19. Lithium aluminium hydride reduction of 1 provides the alcohol 22 which can be dehydrated to a mixture of 23 and 24 by FVP at 800-950 degrees C.

A novel approach to isoindolo[2,1-a]indol-6-ones

“…A further crop of this product (160 mg, 11%) was isolated from the filtrate by chromatography on silica gel (r f = 0.9, DCM) using DCM-EtOAc mixtures as the eluent. 6H-Isoindolo[2,1-a]indol-6-one 23a (1.02 g, 69%) was isolated as a yellow solid, mp 153-154 °C (lit., 15 153-154 °C);…”

Synthesis of 6H‐Isoindolo[2,1‐a]indol‐6‐ones Through Wittig Reaction and Tandem Reductive Cyclization–Lactamization

“…6H-Isoindolo[2,1-a]indol-6-one (1) is also used as a precursor for the synthesis of NorA efflux pump inhibitors. Boussard [ [7] developed a cascade approach involving sigmatropic shift-elimination-cyclization reaction of methyl 2-(indol-1-yl)benzoate by flash vacuum pyrolysis (FVP). Pd(OAc) 2 promoted oxidative intramolecular cyclization, reported by Itahara, [4] was extensively used as a simple procedure giving reasonable yields.…”

Isoindoloindolones - biological activities and syntheses

“…Griffiths's method. Flash vacuum pyrolysis of methyl-2-(indol-1-yl)-benzoate 37 to isoindoindolone was developed by McNab et al 27,28 (Scheme 12). Here high temperature cascade reaction involving sigmatropic shift-elimination-cyclisation provided isoindoloindolone.…”