Synthesis of cyclopropyl silyl ethers and their facile ring opening by photoinduced electron transfer as key step in radical/radical cationic cascade reactions
作者:Prashant A. Waske、Jochen Mattay
DOI:10.1016/j.tet.2005.08.034
日期:2005.10
Various ring-fused cyclopropyl silyl ethers with an benzylic, olefinic or acetylenic side chain have been synthesized. Upon oxidative photoinducedelectrontransfer (PET) the cyclopropane ring opens and forms a reactive β-keto radical, which undergoes intramolecular cyclization. In some cases we observed only formation of ring opened non-cyclized products. With olefinic side chain 5-exo-trig mode of
Conjugate addition of a variety of Grignard reagents to 2-cyclopentenone followed by cyclopropanation of the resulting enol ethers gave a range of substituted cyclopropyl silyl ethers in good yield. Treatment of these cyclopropyl silyl ethers with ferric chloride in DMF gave the one carbon ring expanded beta-chloro ketones which were eliminated to the corresponding 4- substituted-2-cyclohexenones.