Enzymatic cyclizations using laccases: Multiple bond formation between dihydroxybenzoic acid derivatives and aromatic amines was written by Hahn, Veronika;Davids, Timo;Lalk, Michael;Schauer, Frieder;Mikolasch, Annett. And the article was included in Green Chemistry in 2010.Formula: C6H7N3O This article mentions the following:
Oxidative C-N bond formation followed by cyclization of dihydroxybenzoic acid derivatives with aromatic and heteroaromatic amines was catalyzed in the presence of oxygen by laccases [E.C. 1.10.3.2] from the white rot fungi Pycnoporus cinnabarinus and Myceliophthora thermophila. The laccase-catalyzed formation of cycloheptenes, cyclooctenes, diazaspiro cyclohexenes, and phenazines was investigated for the first time with regard to the ring size and substituents of the aromatic amines as well as to the substitution patterns of the substrates. Differences to C-N bond formation without cyclization are discussed. In the experiment, the researchers used many compounds, for example, 3-Aminopicolinamide (cas: 50608-99-6Formula: C6H7N3O).
3-Aminopicolinamide (cas: 50608-99-6) belongs to amides. Because of the greater electronegativity of oxygen, the carbonyl (C=O) is a stronger dipole than the N–C dipole. The presence of a C=O dipole and, to a lesser extent a N–C dipole, allows amides to act as H-bond acceptors. Amides are not in general accessible by the direct condensation of amines with carboxylic acids for two reasons: first, both components are readily deactivated by a transfer of a proton from the acid to the amine and second, the hydroxy unit on the carbonyl of the acid is a relatively poor leaving group. Nevertheless, the formation of five- and six-membered rings is often surprisingly simple provided that other factors can be brought into play to assist in the condensation.Formula: C6H7N3O
Referemce:
Amide – Wikipedia,
Amide – an overview | ScienceDirect Topics