Metal‐Free and <i>syn</i> ‐Selective Hydrohalogenation of Alkynes through a Pseudo‐Intramolecular Process

A new metal-free hydrohalogenation method for alkynes has been developed, which proceeds through a pseudo-intramolecular process. In this reaction, ethynylaniline serves as substrate to quantitatively form an anilinium salt upon treatment with hydrochloric acid. The spatial proximity facilitates the efficient electrophilic addition of HCl ethynyl group in syn-mode, affording corresponding chloroalkene without overaddition. This protocol was applied HBr and HI, bromo- iodoalkenes were obtained, respectively. obtained converted tri-substituted alkenes possessing different aryl/alkynyl groups Pd-catalyzed cross-coupling reactions.