# Mechanism for the chlorination of Fluorene with NCS?

From literature, it was described that fluorene can react with NCS and conc. HCl to produce the 2,7-diCl derivative. Please help me understand the mechanism.

• I'd always suggest checking the original paper, rather than relying on the one-liner summary from SciFinder / Reaxys. Since you're on SciFinder, it shouldn't be too many extra clicks. – orthocresol Jul 6 '20 at 11:52
• The source of the reaction conditions presented by the OP is: thieme-connect.de/products/ejournals/abstract/10.1055/…, which predates the link provided by Waylander. – user55119 Dec 3 '20 at 17:01

it has been described recently that at very low pH ($$\mathrm{pH < 3}$$) $$\ce{Cl2}$$ functions as an active chlorinating agent
In the authors' view the system works by $$\ce{NCS}$$ oxidising chloride to chlorine which then provides $$\ce{Cl+}$$ as the chlorinating agent.