The synthesis of aza-azulene derivatives

Abstract

Various synthetic routes to the pyrrolo[1,2-a]azepinium system were attempted.
Chapter Two describes the preparation of some 1-azido-3- phenylprop-1-enes. Thermal decomposition of these vinyl azides did not result in any pyrrolo[1,2-a]azepines.
Attempts at [2+2] additions of dichloroketene to 3H-pyrrolizine are described in Chapter Three. Electrophilic attack of dichloroacetyl chloride or trichloroacetyl chloride (precursors to dichloroketene) on 3H-pyrrolizine to give 5-dichloroacetyl-3H- pyrrolizine or 5 trichloroacetyl-3H-pyrrolizine was the predominant reaction. Only in one case was a [2+2] addition product found, 8- trichloroacetyl-3-dichloro’ -7 azatricyclo[5,3,0,0 2'5]deca-1(10) 3-dien-4-one. Attempted ring expansion of this tricyclic compound under basic conditions failed. Some reactions of 5-trichloroacetyl-3H -pyrrolizine are described, including the novel reaction with potassium carbonate and methanol to give 5-dichloromet.hyl-3- carbomethoxy-3H-pyrrolizine and a ring opened product, 2-carbomethoxy -5(4-chlorobut-1-en-3-on-1-yl)pyrrole. The synthesis of 5-acetyl-3H- pyrrolizine was achieved via two routes.
The synthesis of 5,6-dihydropyrrolo[1,2-a]azepin-7-one was carried out by an aldol condensation of 1(butan-3-on-1yl)-2-formyl- pyrrole. The syntheses of both pyrrolo[1,2-a]azepin-7-one and 5H- pyrrolo[1,2-a]azepine proceeded from 5,6-dihydropyrrolo[1,2-a]azepin- 7-one, the precursor in two separate routes.Protonation and ethylation of pyrrolof1,2-a]azbpin-7-one gave pyrrolo[1,2-a]azepinium salts but it was not possible to isolate these. Pyrrolo[1,2-a]azepin- 7-one underwent a Wittig reaction to give 7-methylene-7H-pyrrolo[1,2- a]azepine, protonation of this failed to yield any isolable salt.
The protonation reaction of pyrrolot1,2-a]azepin-7-one and of three indolo[1,2-a]azepinones were studied by NMR spectroscopy. The spectral data produced gave some information on theTT-bonding of the ketones in neutral solution, in acidic solution and in their ethylated forms.