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The mechanisms for the deamination reactions of 6-thioguanine (6-TG) with H2O, OH−, and OH−/H2O and for protonated 6-thioguanine (6-TGH+) with H2O have been studied by theoretical calculations. Six pathways, paths A–F, have been explored and relative energies, enthalpies, and Gibbs energies were calculated for each reaction path. Compared with the deamination reaction of 6-TG with H2O or 6-TGH+ with H2O, the deamination reaction of 6-TG with OH− shows a lower overall Gibbs energy of activation, indicating that the 6-TG deamination reaction is favorably to occur for the deprotonated form 6-TG− with H2O. With the assistance of an additional water molecule, the deamination reaction of 6-TG with OH−/H2O (path F) is found to be the most feasible pathway in gas phase and also in aqueous solution. The overall Gibbs energy of activation for path F in gas phase and in aqueous solution is 169.8 and 140.6 kJ mol−1 (SMD model), respectively, at the B3LYP/6–311++G(d,p) level of theory. [ABSTRACT FROM AUTHOR]

The title compound, C27H24N2O5, is a product of the deamination reaction from aza-14-crown-4 ether containing the γ-piperidone subunit. The title molecule contains a 16-membered macrocycle with the conformation of the C—O—C—C—O—C—C—O—C polyether chain being t–g(-)–t–t–g(+)–t (t = trans, 180°; g = gauche, ±60°). The dihedral angle between the planes of the benzene rings fused to the aza-14-crown-4-ether moiety is 31.11 (14)°. The cavity size inside the macrocycle is 4.72 Å. The macrocycle is significantly flattened as a result of the extended conjugated system. Steric repulsion between the pyridylcarboxamide fragment and the benzene ring results in a slight deviation of macrocycle from planarity. The structure also features intramolecular hydrogen bonding, which results in a deviation of the angle between the planes of amide and pyridyl groups from planarity: this angle is 16.32 (18)°. In the crystal, the molecules are linked into infinite zigzag chains via intermolecular C—H...π contacts. The chains are bound into layers parallel to (100) by weak intermolecular C—H...O hydrogen bonds.

The title compound, C27H24N2O5, is a product of the deamination reaction from aza-14-crown-4 ether containing the γ-piperidone subunit. The title mol­ecule contains a 16-membered macrocycle with the conformation of the C—O—C—C—O—C—C—O—C polyether chain being t–g(-)–t–t–g(+)–t (t = trans, 180°; g = gauche, ±60°). The dihedral angle between the planes of the benzene rings fused to the aza-14-crown-4-ether moiety is 31.11 (14)°. The cavity size inside the macrocycle is 4.72 Å. The macrocycle is significantly flattened as a result of the extended conjugated system. Steric repulsion between the pyridyl­carboxamide fragment and the benzene ring results in a slight deviation of macrocycle from planarity. The structure also features intra­molecular hydrogen bonding, which results in a deviation of the angle between the planes of amide and pyridyl groups from planarity: this angle is 16.32 (18)°. In the crystal, the mol­ecules are linked into infinite zigzag chains via inter­molecular C—Hπ contacts. The chains are bound into layers parallel to (100) by weak inter­molecular C—HO hydrogen bonds. [ABSTRACT FROM AUTHOR]

A green metal-free synthesis of spiro-fused 3,4′-pyrazolo[4′,3′:5,6]pyrido[2,3-d]pyrimidine derivatives via deamination cyclization reactions of isatins, substituted 1H-pyrazol-5-amine, and 6-aminopyrimidine-2,4(1H,3H)-dione or 6-amino-1,3-dimethylpyrimidine-2,4(1H,3H)-dione in aqueous medium is reported. This is an efficient route for synthesis of the target products by deamination cyclization reaction. The other advantages of this process are high yield, easy separation, wide substrate range, and environmental friendliness. [ABSTRACT FROM AUTHOR]

Efficient and green reactions of different aromatic aldehydes, 3-amino-1-phenyl-1H-pyrazol-5(4H)-one, and substituted 3-aminopyrazoles for the synthesis of pyrazolo[3,4-b:4′,3′-e]pyridin-3(2H)-one derivatives have been reported through deamination cyclization reactions. This is a new route for the generation of pyrazolo[3,4-b:4′,3′-e]pyridin-3(2H)-one compounds. According to the reported literature, these kinds of compounds have important optical properties, and have potential application prospects. Other advantages of this process are simple operation, easy separation, and a wide range of substrates. Best of all, this method possesses an environmentally benign procedure. [ABSTRACT FROM AUTHOR]

Reinvestigation of an old experimental finding - the formation of linearly fused tetrazoloisoquinolines from 2,3-diamino-isoquinolinium salts, by using 15N-labeling and 15N-NMR spectroscopy, revealed that the ring closure pathway - unlike a recently observed cyclization of the same diamino salt - does not proceed via a rearrangement route. By comparison of this reaction with the entirely different reactivities of other related 1,2-diamino-azinium salts, a general mechanism is suggested, revealing an ambident reactivity of these diamino compounds. [ABSTRACT FROM AUTHOR]