A comparison of two effective chiral auxiliaries - (2R)-bornane-10,2-sultam and (2R)-bornane-10,2-cyclohydrazide - using the [4+2] cycloaddition of cyclopentadiene to their N,N '-fumaroyl derivatives

A correlation between the solvent polarity and the logarithm of the diaster eoisomer ratio (dr) was found for the uncatalyzed [4+2] cycloaddition of cy clopentadiene to N,N'-fumaroyldi[(2R)-bornane-10,2-(2'-phenyl-pyrazol-3'-on e)]. Using the Abboud-Abraham-Kamlet-Taft parameters, predictive values for this method resulted in an optimum diastereoisomeric excess (de) of more t han 97% in hexane. Implications for the stereochemical course of the reacti on as well as a comparison with the analogous (2R)-bornane-10,2-sultam auxi liary are discussed. (C) 2000 Elsevier Science Ltd. All rights reserved.