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Radical Cyclization Approaches to Pyrrolidines
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Kemiska institutionen, Avdelningen för organisk kemi.
2002 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

Five-membered rings are readily prepared by 5-exo-trig radical cyclization. This thesis is concerned with novel methodology for pyrrolidine synthesis. We have synthesised selenium containing radical precursors from aziridines and α-phenylseleno ketones, and cyclized them to 2,4- and 3,4-disubstituted pyrrolidines. A few examples of 5-exo-dig cyclization were also demonstrated. In another study we investigated the capacity of the nitrogen protecting group to direct diastereoselectivity in the formation of 2,4-disubstituted pyrrolidines. The diphenylphosphinoyl protecting group directed cyclization to occur in a highly cis-selective manner. When cyclizations were performed at 17 oC, cis/trans-ratios as high as 24/1 were obtained. In contrast, cyclization of the unprotected pyrrolidine precursor afforded the trans-diastereomer as the major product (cis/trans = 1/3.3 – 1/20). We also examined the use of a hydroxyl auxiliary for controlling diastereoselectivity in radical cyclization. The required selenium containing radical precursors were synthesised from 2-cyanoaziridines by addition of organometallic reagents, reduction of the resulting aziridine ketone, and benzeneselenol ring-opening of the aziridine. Cyclization at 17 oC produced 2,4-disubstituted pyrrolidines substantially enriched in the trans-isomer (cis/trans = 1/9 – 1/12). Novel radical cyclization approaches to thiazolines and pyrrolines were also tried.

The thesis also describes attempts to improve the Hassner aziridine synthesis by employing stannous chloride as a functional group tolerant reducing agent.

sted, utgiver, år, opplag, sider
Uppsala: Acta Universitatis Upsaliensis , 2002. , s. 59
Serie
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 702
Emneord [en]
Organic chemistry, Radical cyclization, diastereselectivity, pyrrolidine, pyrroline, thiazoline, aziridine
Emneord [sv]
Organisk kemi
HSV kategori
Forskningsprogram
organisk kemi
Identifikatorer
URN: urn:nbn:se:uu:diva-1954ISBN: 91-554-5287-6 (tryckt)OAI: oai:DiVA.org:uu-1954DiVA, id: diva2:161543
Disputas
2002-04-26, the The Svedberg Lecture Hall at the Institute of Chemistry, Uppsala, 10:15
Opponent
Tilgjengelig fra: 2002-04-05 Laget: 2002-04-05bibliografisk kontrollert

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