Brønsted Acid Mediated Annulation of α‐Hydroxy Amides with Cycloalkanones: Access to Double Spirocyclic Oxazolidin‐4‐ones

A Brønsted acid mediated annulation of cyclic α‐hydroxy amides with cycloalkanones provide access to unusual double spirocyclic oxazolidin‐4‐one derivatives. This spirocyclization occurs in one‐pot and the overall process is highly efficient. The annulation reaction does not need metal‐catalyst. No self‐condensation of cycloalkanone occurs under acidic conditions. The synthetic technique is operationally simple and chemoselective. The transformation exhibits broad scope constructing a large array of highly functionalized complex double spirocyclic oxazolidin‐4‐one derivatives in good yields. Notably, all the reactions have been carried out in gram scale. A direct Brønsted acid mediated one‐pot condensation of cyclic α‐hydroxy amides and cycloalkanones offered a reliable entry to accessing a library of double spirocyclic derivatives. This current methodology is applicable to direct synthesis of double spirocyclic oxazolidin‐4‐ones involving microcyclic ketones (synthesis of unusual 5/6/7‐5‐12 spirocyclic molecules). These novel scaffolds are useful to agrochemical and pharmaceutical relevance.