2-Imidazolines in Annulation Studies.

Dimopoulos, Paschalis A. (2000). 2-Imidazolines in Annulation Studies. PhD thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.0000ff76

Abstract

This thesis will describe attempts to use suitably substituted 2-imidazolines in Diels-Alder reactions. In order to synthesise these target 2-imidazolines a new and reliable method for the synthesis of 2-alkyl and 2-alkenyl-2-imidazolines has been developed. Metallation at C(2a) of l-ferf-butyloxycarbonyl-2-methyl-2-imidazoline, followed by reaction with a range of electrophiles and deprotection with TFA reliably afforded N(l)- unsubstituted 2-substituted 2-imidazolines; P- or Se-electrophiles led to 2-alkenyl-2- imidazolines via Wadsworth-Emmons reaction or selenoxide elimination.

In an attempt to prepare N-butadienyl-2-imidazolines via the reaction of 2-alkyl-2-imidazolines and ɑ,ß-unsaturated aldehydes or ketones, tetrahydroimidazo[1,2-a]pyridines have been synthesised via conjugate addition of the heterocycle N(l) nitrogen atom followed by enamine-aldol condensation at C(2ɑ).

2-Imidazolines reacted with ß-ketoesters to give tetrahydroimidazo[1,2-a]pyridin- 5-ones.

Whilst examining the reactions of 2-alkyl-2-imidazolines with alkyne diesters, a new annulation was uncovered that is based on N(l) conjugate addition followed by C(2ɑ) The reaction of 2-imidazolines with dialkyl acetylenedicafboxylate afforded tetrahydropyrrolo[1,2-a]imidazole-5,6-diones.

None of the 2-imidazolines synthesised that contained diene functionalities underwent either intra or intermolecular Diels-Alder reactions.