Activation of Thioglycosides with Ferric Chloride: Scope and Mechanism.

Previously, we disclosed a new method for the activation of armed and superarmed ethylthio glycosides using an inexpensive and abundant iron-(III) chloride. Reported herein are the next steps toward refining the reaction conditions, broadening the scope of this method to glycosidation of less-reactive glycosyl donors, and investigating the reaction mechanism. This reaction is swift and generally high-yielding. The completion of the reaction can be monitored by eye, and typically, the color change (start of the reaction) can be detected right after the addition of the glycosyl donor to the premixed mixture of the acceptor and ferric chloride.