Intramolecular homolytic substitution at selenium: synthesis of novel selenium-containing vitamin E analogues.
Treatment of 1-(benzylselenenyl)-5-butyl-5-nonanol (10) with oxalyl chloride followed by the sodium salt of N-hydroxypyridine-2-thione afforded the corresponding pyridine-2-thione-N-oxycarbonyl (PTOC) oxalate ester which was not isolated but immediately heated to provide 2,2-dibutylselenane (7). This transformation presumably involves a tertiary alkyl radical that undergoes intramolecular homolytic substitution at selenium with loss of the benzyl radical to provide the selenium-containing ring system (7). A similar protocol, when applied to 1-(2-benzylselenenyl-5-methoxyphenyl)-3-methyl-3-heptanol (18) and 1-(2-benzylselenenyl-5-methoxyphenyl)-3,7,11,15-tetramethyl-3-hexadecanol (19), followed by deprotection, afforded the selenium-containing alpha-tocopherol analogues 4 and 1f, respectively, in moderate yields. To the best of our knowledge, these transformations represent the first examples of tertiary radicals involved in homolytic substitution chemistry at selenium.
Al-Maharik
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Institute of Chemistry, Department of Organic Chemistry, Uppsala University, Box 531, S-751 21 Uppsala, Sweden.
Engman
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Malmström
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J
Schiesser
C H
CH
D006571:Heterocyclic Compounds / Q000737:chemistry*; D012643:Selenium / Q000737:chemistry*; D014810:Vitamin E / Q000031:analogs & derivatives* / Q000737:chemistry*
D006571:Heterocyclic Compounds; D014810:Vitamin E; D012643:Selenium