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.

A simple and scalable method for stereoselective synthesis of thioethers directly from alcohols using isothiouronium salts is presented. The utility of this thiol-free reaction was exemplified by late-stage modification of complex molecules.

A Brønsted acid-catalyzed selective arene-ynamide cyclization is described. This reaction proceeds via a keteniminium intermediate and enables the preparation of seven-membered ring enamide products. Mechanistic studies uncover an unusual product inhibition behavior.Graphical abstract Electronic supplementary materialThe online version of this article (10.1007/s00706-018-2320-x) contains supplementary material, which is available to authorized users.

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We report the development of an isothiouronium salt as a reagent for the operationally simple synthesis of cyanomethyl thioesters with high functional group tolerance and avoiding the use of thiols. Additionally, we show that the products can be engaged in amide synthesis in either a two-step or one-pot fashion.