Pure Appl. Chem., 2008, Vol. 80, No. 5, pp. 1135-1140
doi:10.1351/pac200880051135
γ-Methylidene-δ-valerolactones as a coupling partner for cycloaddition: Palladium-catalyzed [4+3] cycloaddition with nitrones*
Ryo Shintani, Masataka Murakami, and Tamio Hayashi
Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8502, Japan
Abstract:
A new type of reagent, γ-methylidene-δ-valerolactones, has been devised, which acts as a four-carbon unit in a Pd-catalyzed cycloaddition reaction through the formation of a 1,4-zwitterionic species. The utility has been demonstrated in the context of stereoselective [4+3] cycloaddition with nitrones to provide highly functionalized 1,2-oxazepines, including the asymmetric variant with high enantioselectivity.
Keywords: asymmetric catalysis; cycloaddition; nitrones; palladium catalyst.
*Paper based on a presentation at the 14th International Symposium on Organometallic Chemistry Directed Towards Organic Synthesis (OMCOS-14), 2-6 August 2007, Nara, Japan. Other presentations are published in this issue, pp. 807-1194.