alpha-Hetero-substituted Furans as Dienes in [4+3] Cycloadditions with 1,3-Dimethyloxyallyl Cation for the Preparation of New Versatile Cycloheptane Synthons: A Study of the Factors Controlling the Diastereoselectivity.
作者:Angel M. Montaña、Sandra Ribes、Pedro M. Grima、Francisca Garcia、Louisa Barré、Ole Hammerich、Inger Søtofte、Bengt Långström
DOI:10.3891/acta.chem.scand.52-0453
日期:——
[4+3] Cycloaddition reactions of 2-functionalized furans with 1,3-dimethyloxyallyl cation, afford versatile polyfunctionalized cycloheptane synthons. Increasing electron-donating properties and/or decreasing size of the substituent at C-2 of furan improves yield but decreases stereoselectivity. The opposite effect is also observed, so, by designing a bulky enough alpha-substituent it is possible to obtain endo stereospecificity. cis Stereospecificity is observed in all studied cases and it is probably determined by the type of reaction mechanism.