Chemoselective Activation of Diethyl Phosphonates: Modular Synthesis of Biologically Relevant Phosphonylated Scaffolds

Phosphonates have garnered considerable attention for years owing to both their singular biological properties and their synthetic potential. State-of-the-art methods for the preparation of mixed phosphonates, phosphonamidates, phosphonothioates, and phosphinates rely on harsh and poorly selective reaction conditions. We report herein a mild method for the modular preparation of phosphonylated derivatives, several of which exhibit interesting biological activities, that is based on chemoselective activation with triflic anhydride. This procedure enables flexible and even iterative substitution with a broad range of O, S, N, and C nucleophiles.

Intramolecular Nucleophilic Substitution of ω-Haloalkylphosphine Derivatives

ω-Haloalkylphosphine derivatives undergo the intramolecular nucleophilic substitution reaction upon treatment with a strong base, yielding either cycloalkylphosphine derivatives or heterocyclic phosphine derivatives. The selectivity of the cyclization of (ω-haloalkyl)alkylarylphosphine derivatives depends strongly on the distance between the electrophilic and nucleophilic carbon atoms and the structure of the phosphorus moiety. The desymmetrization of dimethylphenylphosphine sulfide followed by haloalkylation and cyclization led to the enantiomerically enriched tertiary phosphine sulfide, possessing a cyclohexyl fragment at the phosphorus.