open access

https://hdl.handle.net/2115/52793

Stereocontrolled synthesis of carbocyclic compounds with a quaternary carbon atom based on SN2 ' alkylation of γ,δ-epoxy-α,β-unsaturated ketones

英語

2012-07-28

Royal Society of Chemistry

Organic & Biomolecular Chemistry

10(28)

5431-5442

We 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.

学術雑誌論文

Accepted Manuscript

Org. Biomol. Chem., 2012,10, 5431-5442 - Reproduced by permission of The Royal Society of Chemistry (RSC)

1477-0520