Enantioseparation of P -Stereogenic 1-Adamantyl Arylthiophosphonates and Their Stereospecific Transformation to 1-Adamantyl Aryl- H -phosphinates.

A focused library of 1-adamantyl arylthiophosphonates was prepared in racemic form. An enantioseparation method was developed for P -stereogenic thiophosphonates using ( S )-1-phenylethylamine as the resolving agent. Under optimized conditions, three out of the five arylthiophosphonates were prepared in enantiopure form ( ee > 99%). The subsequent desulfurization of optically active arylthiophosphonates gave the corresponding H -phosphinates without significant erosion of enantiomeric purity ( ee = 95-98%). Hence, this reaction sequence can be considered an alternative method for the preparation of 1-adamantyl aryl- H -phopshinates. The absolute configuration of the ( S )-1-adamantyl phenylphosphonothioic acid was assigned using single-crystal XRD and it allowed the confirmation that the removal of the P = S group proceeds with retention of configuration. The organocatalytic applicability of ( S )-1-adamantyl phenylphosphonothioic acid was also evaluated as a P -stereogenic Brønsted acid.