A lactam is a cyclic amide. The term is a portmanteau of the words lactone + amide.
Greek prefixes in alphabetical order indicate ring size:α-Lactam (3 ring atoms)
β-Lactam (4 ring atoms)
γ-Lactam (5 ring atoms)
δ-Lactam (6 ring atoms)
ε-Lactam (7 ring atoms)
This ring-size nomenclature stems from the fact that a hydrolyzed α-Lactam leads to an α-amino acid and a β-Lactam to a β-amino acid, etc.
General synthetic methods exist for the organic synthesis of lactams.Lactams form by the acid-catalyzed rearrangement of oximes in the Beckmann rearrangement.
Lactams form from cyclic ketones and hydrazoic acid in the Schmidt reaction.
Lactams form from cyclisation of amino acids.
Lactams form from intramolecular attack of linear acyl derivatives from the nucleophilic abstraction reaction.
In iodolactamization an iminium ion reacts with an halonium ion formed in situ by reaction of an alkene with iodine.
Lactams form by copper-catalyzed 1,3-dipolar cycloaddition of alkynes and nitrones in the Kinugasa reaction
Diels-Alder reaction between cyclopentadiene and chlorosulfonyl isocyanate (CSI) can be utilized to obtain both β- as well as γ-lactam. At lower temp (−78°C), β-lactam is the preferred product. At optimum temperatures, a highly useful γ-lactam known as Vince Lactam is obtained.
Lactim is a cyclic carboximidic acid compound characterized by an endocyclic carbon-nitrogen double bond. It is formed when lactam undergoes tautomerization.Lactams can polymerize to polyamides.