One-pot synthesis of N-substituted pantolactams from pantolactone

Rac-N-substituted pantolactams () are readily obtained in medium to good yields by reaction of rac-pantolactone () with primary amines under acid catalysis, whether at 250°C in a pressure reactor or under microwave irradiation. It appears that the amine can react with pantolactone at the carbonyl carbon atom to give a hydroxyamide () in a reversible way and at the methylene carbon atom to give a γ-amino acid (). The last one on dehydration would give the corresponding pantolactam ().