94. Stereo and Face Selectivity in Cycloadditions of 1,2,3-Trichloro-3-fluorocyclopropenes to Acyclic Dienes and Furans

Article abstract of DOI:10.1002/hlca.19910740510

The stereo and face selectivities of the cycloaddition of 1,2,3-trichloro-3-fluorocyclopropene (1a) with acyclic dienes and furans has been re-investigated by X-ray determination and correlation of 19F-NMR data.The isolated adducts of dienes exclusively have exo-configuration, and exo-configuration predominates with furans.The Cl substituents of the resulting cyclopropane ring are cis-oriented.The face selectivity of the reaction with both types of substrates is attributed to electrostatic interactions between the F and the bridgehead Cl substituents, which destabilize the F-cis-transition state (13 (F-cis)) over 13 (F-trans).