Water as a key ingredient in the synthesis of platinum H‐phosphonate complexes and catalytic cascade reactions involving the hydration of alkynes and hydrogen/deuterium exchange reaction

Abstract

Several platinum (II) complexes bearing heteroatom‐substituted phosphine oxides ligand H(O)P(OCMe2CMe2O) were obtained. The H‐phosphonate was synthesized in an alternative, one‐pot procedure with the use of water from hexamethylphosphorus triamide and pinacol. In the presence of H(O)P (OCMe2CMe2O) ligand, [PtCl2(cod)] was converted into three new complexes: [PtCl2{P(OH)(OCMe2CMe2O)}2] [Pt1], [PtCl{P(O)(OCMe2CMe2O)}{P(OH)(OCMe2CMe2O)}2] [Pt2], and [Pt{P(OH)(OCMe2CMe2O)}4]Cl2 [Pt3]. When [PtCl2(PPh3)2] was utilized as the substrate, [PtCl(PPh3)2{P(OH)(OCMe2CMe2O)}]Cl [Pt4] and [PtCl(PPh3)2{P(O)(OCMe2CMe2O)}] [Pt5] complexes were obtained, as the results of reaction with H(O)P(OCMe2CMe2O) and HP(OCMe2CMe2O)(OCH2CMe2NH) ligands. The structural features of all complexes were characterized by physicochemical and spectroscopic methods as well as single X‐ray diffraction studies. Complex [Pt1] was found to promote cascade reaction, the addition of water to triple bond, and hydrogen/deuterium exchange reaction. The hydration reaction of substituted terminal aryl alkynes gave exclusively Markovnikov products and tolerated different functional groups. Various aryl ketones were synthesized in good to excellent yield. H/D exchange reaction was exemplified by the model reaction of acetophenone in deuterium containing methanol. Factors influencing the effectiveness of the hydrogen/deuterium exchange reaction of the methyl group were determined. The cascade procedure bears the potential to overcome the limitations of conventional synthesis and unlocks practical use in the synthesis of deuterium‐labeled pharmaceuticals.