Stereochemical Course of the Base-Promoted Aldol Self-Coupling of Racemic 5-Norbornen-2-one and 2-Norbornanone

Article abstract of DOI:10.1021/jo00007a036

The enolate anions of 5-norbornen-2-one and 2-norbornanone enter into self-coupling with their conjugate acids in a manner that exhibits diastereomeric discrimination.The major products obtained from aldol reactions conducted at low temperature are those where bonding has occurred preferentially to the ketone of like absolute configuration.Structural assignments rest on X-ray crystallographic analyses and chemical interconversions.When the reactions are effected at higher temperatures, dehydration also occurs spontaneously.All indicators point to adherence by thesebicyclic systems to molecular recognition in these condensation reactions as well.The aldol products, which are stable to the conditions under which they are formed, have been evaluated for their inherent levels of total energy and strain energy by molecular mechanics methods.These data, when taken in conjunction with assumed reaction trajectories, suggest the possible causes that underlie this interesting selectivity.