Stereocontrolled synthesis of kelsoene by the homo-favorskii rearrangement.
[reaction: see text] (+/-)-Kelsoene (4) has been synthesized from 2,5-dihydroanisole in 16 steps in 12.5% overall yield. The key step involves a base-catalyzed reaction of gamma-keto tosylate (5), which effects a homo-Favorskii rearrangement to 16 as well as the corresponding intramolecular S(N)2 product 15 from the enolate of 5. Ketone 15 can efficiently be isomerized to cyclobutanone 17 having the kelsoene carbon skeleton upon acid treatment.
Zhang
Liming
L
Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109-1055, USA.
Koreeda
Masato
M