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On the origin of cis selectivity in the cyclization of N-protected 2-substituted 3-aza-5-hexenyl radicals: a density functional study
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Organic Chemistry.
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2004 (English)In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 69, no 5, 1487-1491 p.Article in journal (Refereed) Published
Abstract [en]

Cyclization of the N-dimethylphosphinoyl-2-methyl-3-aza-5-hexenyl radical has been studied at the UB3LYP/6-31+G(d)//UB3LYP/6-31G(d) hybrid density functional level. The corresponding radical precursor has been synthesized and found to give cis/trans ratios of up to 10/1 in reductive radical cyclizations. The relative energies of reactant and transition state conformers were determined. In discord with the Beckwith-Houk model, it has been found that chair-axial transition states, which lead to cis products, are lowest in energy, rationalizing the observed experimental diastereoselectivity.

Place, publisher, year, edition, pages
2004. Vol. 69, no 5, 1487-1491 p.
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:uu:diva-90422DOI: 10.1021/jo030294hPubMedID: 14987001OAI: oai:DiVA.org:uu-90422DiVA: diva2:162771
Available from: 2003-05-12 Created: 2003-05-12 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Construction of Five-Membered Heterocyclic Compounds via Radical Cyclization
Open this publication in new window or tab >>Construction of Five-Membered Heterocyclic Compounds via Radical Cyclization
2003 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis describes how radical cyclization chemistry can be applied for the construction of heterocyclic compounds.

In the first part, a series of electron deficient α-phenylselenenylalkenes were prepared via a PhSeCl-addition/HCl-elimination sequence. Allyl- and propargylamines readily underwent conjugate addition to these species to produce pyrrolidines or dihydropyrrol derivatives, after triethylborane initiated reductive radical cyclization in the presence of tris(trimethylsilyl)silane.

The second part describes a convergent synthesis of the pineal hormone melatonin. The indole nucleus is secured via a tris(trimethylsilyl)silane mediated 5-exo radical cyclization. The protocol provides convenient and simple access to compounds useful for studies of biological activity and structure activity relationships.

The third part describes construction of substituted tetrahydrofuran-3-ones and pyrrolidin-3-ones. Regioselective ring-opening of epoxides or aziridines with benzeneselenolate/tellurolate, followed by Michael addition to electron deficient alkynes afforded the corresponding O/N-vinylated compounds. The tetrahydrofuran-3-ones and pyrrolidin-3-ones were secured via radical carbonylation/reductive cyclization using pressurized carbon monoxide (80 atm).

The fourth part is concerned with the effect of an N-protecting group on the cyclization of 2-substituted-3-aza-5-hexenyl radicals. Relative energies for reactants and transition states were determined using density functional calculations. Reactant and transition state conformers leading to cis-product were lower in energy than those leading to trans-product. The results can be explained by the unfavorable 1,2-strain present in chair-equatorial and boat-equatorial conformers.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2003. 59 p.
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 845
Keyword
Organic chemistry, radical, cyclization, carbonylation, melatonin, pyrrolidine, pyrrolidin-3-one, tetrahydrofuran-3-one, Organisk kemi
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:uu:diva-3429 (URN)91-554-5648-0 (ISBN)
Public defence
2003-06-04, B42, BMC, Uppsala, 10:15
Opponent
Supervisors
Available from: 2003-05-12 Created: 2003-05-12Bibliographically approved

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Ottosson, HenrikEngman, Lars

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