New dehydration in the pyrrolo[1,2–6‐b]isoquinoline series. Preparation and structural identification of 3,5‐dihydrobenz[f]indolizin‐3‐one

Abstract

3,5‐Dihydrobenz[f]indolizin‐3‐one was prepared by a novel dehydration reaction involving the heating of 1,2,3,5,10,10a‐hexahydro[f]indolizine‐3,10‐dione with polyphosphoric acid. The structure of this new compound was established by X‐ray crystallography, by nmr spectroscopy and by reduction to the known products 1,2,3,5‐tetrahydrobenz[f]indolizin‐3‐one and 1,2,3,5,10,10a‐hexahydrobenz[f]indolizin‐3‐one.

8,8′-Dichloro-1,1′,5,5′-tetrahydro-10,10′-bipyrrolo[1,2-b]isoquinoline-3,3′(2H,2′H)-dione

“…During attempts to repeat this reaction with ketone (III) and concentrated hydrochloric acid, acid (IV) (19%), acid (V) (31%), dimer (VI) (25%) and diethylenic lactam (VII) (3%) were obtained. NMR spectroscopic measurements easily lead to the structures of (IV), (V) and (VII), and show that compound (VI) seems to be a dimer of the known (Rigo & Kolocouris, 1983) general structure (VIII). The identity of (VI) was con®rmed as 8,8 H -dichloro-1,1 H ,5,5 Htetrahydro-10,10 H -bipyrrolo[1,2-b]isoquinoline-3,3 H (2H,2 H H)dione, (VI), by an X-ray analysis of the yellow crystals obtained by slow evaporation of a DMF/benzene solution at room temperature.…”

“…Cyclized keto lactams of general structure (I) (Rigo et al, 1990) have proved to be of great interest due to the large diversity of rearrangements observed in this family of compounds (Rigo et al, 1991(Rigo et al, , 1994. In particular, treatment of ketone (I) with polyphosphoric acid led to a dehydration, yielding lactam (II).…”

“…Crystal packing, showing the %±% stacking interactions [symmetry code: ORTEPIII (Burnett & Johnson, 1996) representation of compound (VI), with displacement ellipsoids drawn at the 50% probability level. Cyclized keto lactams of general structure (I) (Rigo et al, 1990) proved to be of great interest due to the large diversity of rearrangements observed in this family of compounds (Rigo et al, 1991(Rigo et al, , 1994. Particularly, treatment of ketone (I) with polyphosphoric acid led to a dehydration, yielding lactam (II).…”

Studies on pyrrolidinones. On the application of copper-catalyzed arylation of methyl pyroglutamate to obtain a new benzo[de]quinoline scaffold

“…4,10 To the best of our knowledge, this type of dehydration reaction was not described in the literature with an N-naphthyl ketolactam scaffold like 2. To our delight, stirring 2 in PPA at 120 C for 6 h gave 32% of heterocycle 4 and the replacing of the dehydrating reagent by Eaton's reagent (P 2 O 5 /MeSO 3 H) 34 improved the yield to 51%.…”

Antioxidant Activity of New Benzo[de]quinolines and Lactams: 2DQuantitative Structure-Activity Relationships

“…Naphthyl derivatives 2 and 4 were synthesized as described recently [18], while dienyl lactams 3 were obtained by dehydration of ketones 1 as previously reported [19,20]. General chemical structures of compounds are presented in Fig.…”