ChemInform Abstract: Regio- and Stereoselective Ring Openings of Unsymmetrical Oxatricyclo Adducts.

✍ Scribed by S. WOO; M. PARVEZ; B. A. KEAY

• Publisher: John Wiley and Sons
• Year: 2010
• Weight: 32 KB
• Volume: 28
• Category: Article
• ISSN: 0931-7597
• DOI: 10.1002/chin.199752117

✦ Synopsis

Regio-and Stereoselective Ring Openings of Unsymmetrical Oxatricyclo Adducts.

-The cycloadducts (I), (IV), (VII), and (X) are amenable to SN2' ring opening by organolithium reagents. Primary, secondary, and tertiary organolithium reagents effect the ring-opening reaction, while methyllithium requires activation by DME before any ring opening occurs. Less reactive organometallic reagents provide no ring opened products, but react stereoselectively with the ketone carbonyl group. The reaction shows high facial selectivity for attack syn to the bridging oxygen atom and is highly regioselective for attack at C9 providing that the bridgehead position is not substituted. A combination of steric and electronic effects are responsible for the high degree of selectivity. Substituents at other positions of the cycloadducts are tolerated and have no effect on the regio-or stereoselectivity of the reaction. -(WOO, S.;