名称:
                                Diastereofacial selectivity in 1,3-dipolar cycloadditions. Reactions of diazomethane with endo,cis-5,6-disubstituted bicyclo[2.2.2]oct-2-enes.
                             
                            
                                摘要:
                                The reaction of diazomethane with endo,cis-5,6-diacetoxy, dimesyloxy, bis(methoxycarbonyl) and dihydroxybicyclo[2.2.2]oct-2-ene derivatives, respectively, afforded either only the anti adduct or a mixture of anti and syn adducts wherein the anti diasteroisomer was highly dominant (greater-than-or-equal-to 10:1).  The observed facial selectivity provides convincing evidence that direct through space interactions between the attacking 1,3-dipole and acetoxy, hydroxy etc.  substituents are, as a whole, repulsive.  Steric ''non-bonded'' repulsions and dipole-dipole interactions override possible stabilizing interactions, e.g. orbital interactions and hydrogen bonding effects.