BF 3 ·SMe 2 for Thiomethylation, Nitro Reduction and Tandem Reduction/SMe Insertion of Nitrogen Heterocycles

Herein, a general, solvent‐free and straightforward thiomethylation of electron deficient heterocycles using BF 3 · SMe 2 as a dual thiomethyl source and Lewis acidic activator is presented. A range of heterocycles including pyrimidine, pyrazine, pyridazine, thiazole and purine derivatives were successfully substituted using this method. An unexpected reductive property of BF 3 · SMe 2 towards nitropyridines was also discovered including an intriguing tandem reduction/SMe insertion process in certain substrates. Notable features of the present work include its convenience and use of a non‐malodorous reagent while the discovery of novel chemical transformations using BF 3 · SMe 2 provides fundamental new insights into the reactivity of this commonly employed reagent.