Radical cyclization in heterocycle synthesis 15. Relationship between a Radical species and radical acceptors of three different types of double bond in radical addition-cyclization.
Relationship between a radical species and radical acceptors of three different types of double bond in radical addition-cyclization was systematically investigated. Substrates carrying alpha,beta-unsaturated amide, isolated olefin, and oxime ether moieties underwent radical addition-cyclization to give differently substituted lactams depending upon the radicals used. The sulfanyl radical addition-cyclization of the substrate proceeded smoothly to give the 5-membered lactam having an alkoxyamino group as a result of preferable addition of an intermediary alpha-carbonyl radical to the oxime ether. On the other hand, the triethylborane-mediated radical addition-cyclization gave the lactam bearing an iodomethyl group as a result of addition to an intermediary alpha-carbonyl radical to isolated olefin. The different regioselectivity was explained by the stability of the intermediary radical and the interaction between SOMO and HOMO.
Miyata
Okiko
O
Kobe Pharmaceutical University, Motoyamakita, Higashinada, Kobe 658-8558, Japan.
Kajisa
Seiko
S
Ueda
Masafumi
M
Yamauchi
Masashige
M
Naito
Takeaki
T
D005609:Free Radicals / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D021241:Spectrometry, Mass, Electrospray Ionization
D005609:Free Radicals