Steric Considerations on Improving the Diastereomeric Ratio of (+)‐ and (−)‐Neomenthyl Phenyl Sulfoxides Using Bulky‐Headed Oxidant Hexadecyltrimethylammonium Periodate and Assignment of Their Configuration

The bulky‐headed oxidant hexadecyltrimethylammonium periodate affords the diastereomeric pairs, ( Ss )‐(+)/( Rs )‐(+) and ( Ss )‐(−)/( Rs )‐(−)‐neomenthyl phenyl sulfoxides in stereochemically pure states with improved diastereomeric excess (48% diastereomeric excess [de]) as compared to its nonbulky counterpart, sodium metaperiodate (28% de) from respective (+)/(−)‐neomenthyl phenyl sulfides. Steric effects involving the head group volume of hexadecyltrimethylammonium periodate is found to play a role in improving the diastereomeric ratio of the products. The two diastereomers can be readily separated by column chromatography. Absolute configuration at the sulfur center in (+)‐neomenthyl phenyl sulfoxide was determined by single‐crystal X‐ray crystallography and found to be Ss . Relative configurations of other sulfoxides were assigned based on the configuration of (+)‐neomenthyl phenyl sulfoxide. Chirality 27:370–374, 2015 . © 2015 Wiley Periodicals, Inc.