<jats:title>Abstract</jats:title><jats:p>The multimetallic iridium‐tritin (Ir‐Sn<jats:sub>3</jats:sub>) complex [Cp*Ir(SnCl<jats:sub>3</jats:sub>)<jats:sub>2</jats:sub>{SnCl<jats:sub>2</jats:sub>(H<jats:sub>2</jats:sub>O)<jats:sub>2</jats:sub>}] (<jats:bold>1</jats:bold>) proved to be a highly effective catalyst towards COH bond activation of γ‐hydroxylactams, leading to a nucleophilic substitution reaction known as the α‐amidoalkylation reaction. Catalyst <jats:bold>1</jats:bold> can be easily synthesized from the reaction of (pentamethylcyclocyclopentadienyl)iridium dichloride dimer {[Cp*IrCl<jats:sub>2</jats:sub>]<jats:sub>2</jats:sub>} and tin(II) dichloride (SnCl<jats:sub>2</jats:sub>). In terms of catalyst loading, reaction conditions and yields of the product formed, <jats:bold>1</jats:bold> is found to be superior compared to classical Lewis acid catalysts. Different carbon (arenes, heteroarenes, allyltrimethylsilane, 1,3‐dicarbonyls) and heteroatom (alcohols, thiols, amides and sulfonamides) nucleophiles have been successfully employed in the intramolecular and intermolecular alkylations, as well as in heterocyclization reactions. In the majority of cases good to excellent yields of 3‐substituted isoindolinones and 5‐substituted pyrrolidin‐2‐ones have been obtained. Besides, the reactions are also atom economical and salt free. It is proposed that the multimetallic Ir‐Sn<jats:sub>3</jats:sub> catalyst behaves as a mild and selective Lewis acid to activate the <jats:italic>γ</jats:italic>‐hydroxylactam towards the formation of the <jats:italic>N</jats:italic>‐acyliminium ion; the latter being trapped by potent nucleophiles leading to the desired products.</jats:p><jats:p><jats:boxed-text content-type="graphic" position="anchor"><jats:graphic xmlns:xlink="http://www.w3.org/1999/xlink" mimetype="image/gif" position="anchor" specific-use="enlarged-web-image" xlink:href="graphic/mcontent.gif"><jats:alt-text>magnified image</jats:alt-text></jats:graphic></jats:boxed-text></jats:p>