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

Abstract

A correlation between the solvent polarity and the logarithm of the diastereoisomer ratio (dr) was found for the uncatalyzed [4+2] cycloaddition of cyclopentadiene to N, N′-fumaroyldi[(2 R)-bornane-10,2-(2′-phenyl-pyrazol-3′-one)]. Using the Abboud–Abraham–Kamlet–Taft parameters, predictive values for this method resulted in an optimum diastereoisomeric excess (de) of more than 97% in hexane. Implications for the stereochemical course of the reaction as well as a comparison with the analogous (2 R)-bornane-10,2-sultam auxiliary are discussed.