2024-03-29T00:05:30Zhttps://eprints.lib.hokudai.ac.jp/dspace-oai/requestoai:eprints.lib.hokudai.ac.jp:2115/527932022-11-17T02:08:08Zhdl_2115_20039hdl_2115_116Stereocontrolled synthesis of carbocyclic compounds with a quaternary carbon atom based on SN2 ' alkylation of γ,δ-epoxy-α,β-unsaturated ketonesYoshimura, FumihikoKowata, AyanoTanino, Keiji464We developed a new method for stereoselective construction of an all-carbon quaternary stereogenic center on a carbocyclic ring based on regio- and stereoselective SN2' alkylation reactions of γ,δ-epoxy-α,β-unsaturated cyclic ketones. Treatment of the ketones, which were readily prepared in enantiomerically pure form by means of aldol condensations between 3-ethoxy-2-cycloalkenones and α,β-epoxy aldehydes, with a R2Zn-CuCN reagent afforded anti-SN2' products stereoselectively. Conversely, the corresponding syn-SN2' products were stereoselectively obtained through two-step transformations of the same γ,δ-epoxy-α,β-unsaturated cyclic ketones: (1) conversion of the epoxide moiety to a chlorohydrin by treatment with MgCl2 and (2) subsequent SN2' substitution of the chlorohydrin with a R2Zn-CuCN reagent. These substitution products with their chiral trans-allylic alcohol moieties are promising precursors for complex molecules. For example, Eschenmoser-Claisen rearrangement of one of the substitution products resulted in stereoselective formation of a keto amide having contiguous quaternary and tertiary stereogenic centers.Royal Society of ChemistryJournal Articleapplication/pdfhttp://hdl.handle.net/2115/52793https://eprints.lib.hokudai.ac.jp/dspace/bitstream/2115/52793/1/OBC10-28_5431-5442.pdf1477-0520Organic & Biomolecular Chemistry1028543154422012-07-28enginfo:pmid/22706976info:doi/10.1039/c2ob25719jOrg. Biomol. Chem., 2012,10, 5431-5442 - Reproduced by permission of The Royal Society of Chemistry (RSC)author