Intramolecular radical allylation with allylic sulfones— A synthesis of (±)-botryodiplodin

✍ Scribed by Robert Nouguier; Ste´phane Gastaldi; Didier Stien; Miche`le Bertrand; Philippe Renaud

• Publisher: Elsevier Science
• Year: 1999
• Tongue: French
• Weight: 233 KB
• Volume: 40
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(99)00486-4

✦ Synopsis

lsopropenyl-5-membered-ring acetal or lactone are potential precursors of (_+)-botryodiplodin (1).

Several pathways, involving 5-exo-trig ring closure onto allylic sulfones, have been in,.estigated. The iodine atom transfer methodology allowed the preparation of the desired skeleton through intramolecular addition of an ot-alkoxyearbonyl radical to the double bond of the appropriate allylic ethyl sulfone. Subsequent deprotonation and kinetic reprotonation led to the key precursor 14 with a high stereoselectivity, ',

-.2so2,ol

ToISO2"

Sulfone 2 was prepared in two steps, according to scheme 3, starting from 3, which is easily available from acetoxychlorination of isoprene. 6 The reaction of 3 with acrolein diethylacetal led to 4 which was then oxidized by meta-chloroperbenzoic acid.