ChemInform Abstract: Stereocontrolled Synthesis of Spiro[n.2]alkenes by Ring Contraction of Fused-Cyclobutanols.

✍ Scribed by Kiyosei Takasu; Yuuki Nagamoto; Yoshiji Takemoto

• Publisher: John Wiley and Sons
• Year: 2010
• Weight: 38 KB
• Volume: 41
• Category: Article
• ISSN: 0931-7597
• DOI: 10.1002/chin.201052060

✦ Synopsis

Stereocontrolled Synthesis of Spiro[n.2]alkenes by Ring Contraction of Fused-Cyclobutanols. -The present newly developed unusual ring contraction rearrangement leads to spirocyclopropanes from fused cyclobutanols. In contrast to bicyclo[4.2.0]octanol derivatives (I) which are exclusively converted into endo-olefins (II), bicyclo[3.2.0]heptanol (IIIa) and bicyclo[5.2.0]nonanol (IIIb) give a mixture of endo-and exo-isomers whereby, the ratio depends on the ring size. Substrate (VI) bearing a carbonyl group is smoothly transformed to the desired spirocyclopropane (VII) but, for bicyclo[3.2.0]heptanol (VIII) only enol sulfonate chloride (X) is observed. Reaction of tricyclic substrate (XI) gives illudane (XII) as expected albeit, also the chloride is formed as a by-product. -(TAKASU*, K.;