Diastereocontrol by a hydroxyl auxiliary in the synthesis of pyrrolidines via radical cyclization.
[reaction: see text] Organoselenium precursors of 3-aza-5-hexenyl radicals carrying a 1-hydroxyalkyl group in the 2-position were prepared by addition of organometallic reagents to N-allyl-2-aziridinecarbonitrile, reduction of the resulting aziridine ketone, and regioselective benzeneselenol ring opening of the aziridine. Reductive radical cyclization was highly selective, affording the corresponding trans-2,4-disubstituted pyrrolidine (cis/trans ca. 1/10) as the major diastereomer. Recrystallization afforded material that was substantially more enriched in the trans isomer (cis/trans < 1/25).
Uppsala University, Institute of Chemistry, Department of Organic Chemistry, Box 531, Sweden.
Magnus
M
Besev
Lars
L
Engman
D001388:Aziridines / Q000737:chemistry; D003500:Cyclization; D005609:Free Radicals / Q000737:chemistry; D009570:Nitriles / Q000737:chemistry; D011759:Pyrrolidines / Q000138:chemical synthesis*; D013237:Stereoisomerism
D001388:Aziridines; D005609:Free Radicals; D009570:Nitriles; D011759:Pyrrolidines