Highly diastereoselective N-acyliminium ion cyclization reactions of a tethered furan

• Published in: Tetrahedron 2012-12, Vol.68 (50), p.10280-10285
• Main Authors: Shengule, Sudhir R., Ryder, Gregory, Willis, Anthony C., Pyne, Stephen G.
• Format: Article
• Language: English
• Subjects: Catalysis; Catalysts: preparations and properties; Chemistry; Exact sciences and technology; General and physical chemistry; Heterocyclic compounds; Heterocyclic compounds with n hetero atom and also o and/or s, se, te hetero atoms; Heterocyclic compounds with o, s, se, te hetero atom and condensed derivatives; Heterocyclic compounds with only one n hetero atom and condensed derivatives; Organic chemistry; Preparations and properties; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry
• ISSN: 0040-4020; 1464-5416
• DOI: 10.1016/j.tet.2012.10.014

The acid catalysed cyclization reactions of tethered furan−4,5-dihydroxypyrrolid-2-ones and furan–4,5-diacetoxypyrrolid-2-ones, via their corresponding N-acyliminium ion intermediates, have been studied. In the case of the tethered furan–3,4-dihydroxypyrrolid-2-one 16, having a two carbon tether, the linearly fused tricyclic compound 18 was formed with high cis selectivity (cis/trans=84:16) when BF3·OEt2 was used as a catalyst. However, when the cyclization reaction was carried out on the related tethered furan–4,5-diacetoxypyrrolid-2-one 17, the linearly fused tricyclic compound 20 was formed as a single diastereoisomer with trans selectivity. In contrast, the attempted cyclization of the tethered furan–4,5-dihydroxypyrrolid-2-one 26, having a one carbon tether, did not result in formation of the corresponding linearly fused tricyclic system, instead it formed the dimer 29 as a single diastereoisomer. Cyclization reactions of the related tethered furan–4,5-diacetoxypyrrolid-2-one 27 also failed to give the corresponding linearly fused tricyclic system or macrocycle. [Display omitted]