posted on 2001-08-24, 00:00authored byNawaf Al-Maharik, Lars Engman, Jonas Malmström, Carl H. Schiesser
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 α-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.