One pot synthesis of α,α-bis(N-arylamido) lactams via iodide-catalyzed rearrangement of β,β-bis(N-arylamido) cyclic ketene-N,O-acetals

Five and six-membered cyclic ketene-N,O-acetals, generated in situ from 2,3-dimethyl-2-oxazolinium iodide or 2,3-dimethyl-2-oxazinium iodide and triethylamine, reacted with aryl isocyanates in refluxing THF producing α,α-bis(N-arylamido) lactams via the iodide-catalyzed rearrangement of β,β-bis(N-arylamido) cyclic ketene-N,O-acetal intermediates. The cyclic ketene-N,O-acetal generated in situ from 2,3,4,4-tetramethyl-2-oxazolinium iodide reacted with isocyanates to give β,β-bis(N-arylamido) cyclic ketene-N,O-acetals, which do not readily rearrange. The two methyls at C-4 hindered the nucleophilic attack of iodide on C-5, which is required for rearrangement.