Borane Catalysed Annulative Sulfenylation of Internal Alkynes: Towards the Synthesis and Study of Highly Unsaturated Heterocycles

This dataset relates to our research into B(C₆F₅)₃-catalysed intramolecular cyclisation reactions of <i>N</i>-protected alkynyl amines and phenols to generate 5-membered heterocycles, including 3-sulfenyl indoles (16 examples, up to 90% yield) and benzo[<i>b</i>]furans (10 examples, up to 90% yield), in good yields with broad functional group tolerance. This protocol was adapted into an annulative π-extension (APEX) reaction when using diyne derivatives of aniline and phenol, which effectively led to sulfenylated polyaromatic heterocycles, such as benzo[<i>a</i>]carbazole or naphtho[1,2-<i>b</i>]benzofurans. These products exhibit fluorescence from locally excited states, consistent with their large singlet-triplet energy gaps. Additionally, the cyclisation of propargyl ethers affords sulfenylated 6-membered 2<i>H</i>-chromenes (7 examples, up to 55% yield). Extensive density functional theory (DFT) calculations were conducted and support a mechanism in which thiirenium ions were identified as key intermediates for the formation of the observed products. The dataset includes raw and processed characterisation and computational data for the compounds synthesised.