Chem. Sci., 2026, Accepted Manuscript DOI: 10.1039/D6SC01123C, Edge Article Sampurna Das, Milan Pramanik, Johannes Westphäling, Abhishek Kumar Gupta, Niklaas Jan Buurma, Thomas Wirth, Eli Zysman-Colman, Mu-Hyun Baik, Rebecca Melen Herein, we disclose a B(C₆F₅)₃-catalysed intramolecular cyclisation reaction of N-protected alkynyl amines and phenols to generate 5-membered heterocycles, including 3-sulfenyl indoles (16 examples, up to 90% yield) and benzo[b]furans (10...