jo050603z_si_002.pdf (263.3 kB)
Diastereoselective Intermolecular Radical Addition to Nitrones
journal contribution
posted on 2005-08-19, 00:00 authored by Masafumi Ueda, Hideto Miyabe, Masako Teramachi, Okiko Miyata, Takeaki NaitoThe intermolecular radical addition to chiral nitrones 2, 4, 5, and 16 was studied. The isopropyl
radical addition to Oppolzer's camphorsultam derivative 2 of glyoxylic nitrone proceeded with
excellent diastereoselectivity to give the desired isopropylated product 3a accompanied by the
diisopropylated product 3b. A high degree of stereocontrol in the reaction of cyclic nitrone 4 was
achieved. The ethyl radical addition to nitrone 4 with triethylborane afforded the desired ethylated
product 9a accompanied by the diethylated product 10a and the ethylated nitrone 11a. To evaluate
the utility of cyclic nitrone 4, several alkyl radicals were employed in the addition reaction, which
afforded the alkylated products 9b−d with excellent diastereoselectivities. In the presence of
Mg(ClO4)2, the ethyl radical addition to BIGN 16 afforded selectively syn isomers. In contrast, the
alkyl radical addition to 16 took place even in the absence of Lewis acid to give anti isomers.