Pure enantiomers from simple, symmetric dienophiles
摘要:
Starting from p-benzoquinone or 2-cyclopentene-1, 4-dione as dienophiles and the enantiomerically pure dienes 1a and 1b, high pressure cycloadditions led to chiral adducts. These were transformed in a regioselective manner to generate well defined stereogenic centres. A remarkably efficient electron density directed regioselectivity was discovered with 18c and 18d.
Efficient syntheses of enantiomerically pure cyclopentadienes which undergo stereoselective and regioselective high pressure cycloadditions with nonsymmetric dienophiles are reported. As these compounds show a quite high chemical as well as thermal stability they are useful as templates in the generation of pure enantiomers by diastereoselective adduct transformation and subsequent retro-Diels-Alder reaction.
Dienes as chiral templates: easy access to pure (2S,3S,4R)-4-hydroxy-2,3-epoxycyclohex-5-en-1-one
作者:Antony Mauvais、Ekkehard Winterfeldt
DOI:10.1016/s0040-4020(01)87948-5
日期:1993.6
The title compound 6 was obtained stereospecifically through a concise sequence including a Diels-Alder reaction with the chiral diene 2 and the retro reaction. The Favorskiirearrangement starting from the intermediate epoxide 4 was found to be regioselective.
Examples of highly efficient kinetic resolutions with the bicyclic chiral cyclopentadiene 1 and several selected cyclic dienophiles are reported. In combination with a thermal retro-Diels-Alder process this procedure provides easy access to both enantiomers of these dienophiles.