Stereochemistry of Sulfur Compounds. II. New Reactions at Chiral Sulfur That Complete the First Monoligostatic Stereochemical Reaction Cycle

This paper describes several new stereospecific reactions at chiral sulfur, and completion of the first known stereochemical reaction cycle in which only a single ligand is common to all compounds of the reaction cycle (monoligostatic). Additional diligostatic and triligostatic stereochemical reaction cycles are described that involve sulfoxides, sulfimides, sulfoximides, sulfinamides, sulfinamidines, sulfinate, and sulfinimidate esters (compounds A–K). The reactions were of 90–100% stereospecificity, and the stereochemical courses of all reactions were assigned. The monoligostatic podal cycle, A → B → C → D → E → F → A (four retentions and two inversions), involved two new reaction types. Reaction D → E went (90%) with formaldehyde–formic acid as reagent. Reaction E → F went (35 %) with 94% retention of configuration when E was treated with pyridine and tosyl chloride. The diligostatic podal cycle, A → D → E → F → A, involved a ligand metathesis and one inversion. A new method for reaction D → A (99% yield, 99% retention) involved nitrous acid as reagent. Cycles A → G → H → A and B → J → K → B were completed and are each triligostatic, antipodal and involve three inversions of configuration.