Copper macrocyclic complex with trans-di[benzo]-porphyrazine and two oxo ligands: DFT quantum-chemical design

Based on the results of a quantum chemical calculation using the DFT method in the OPBE/TZVP and B3PW91/TZVP, the possibility of the existence of a copper heteroligand complex with trans-di[benzo]derivative of 3,7,11,15-tetraazaporphine (trans-di[benzo]porphyrazine) and two oxygen (O[Formula: see text] ions that is still unknown for this element was shown. In addition, the data on the structural parameters, the multiplicity of the ground state, NBO analysis and standard thermodynamic parameters of formation (standard enthalpy [Formula: see text], entropy [Formula: see text] and Gibbs’s energy [Formula: see text] for this complex are presented.

On Pyridopyrazinol Chemistry: Synthesis of Chemiluminescent Substances

Our work on new chemiluminescent substances related to the marine luciferin coelenterazine (λmax = 465 nm) led us to attempt the synthesis of four nitrogen-rich pyridopyrazine-bearing analogues. Accordingly, the preparation of the corresponding benzyl-bearing pyridopyrazinols is studied. By varying the conditions for the condensation of phenylpyruvic acid with 1,2-diaminopyridine or 3,4-diaminopyridine, all the possible pyridopyrazin-2-ol regioisomers are isolated and properly characterized, including by means of crystallographic studies. The ensuing syntheses of the halogenated pyridopyrazines are fraught with difficulties ranging from extensive decomposition to an unexpected ring contraction. In one instance, the inherently reductive mixture of phosphorus oxychloride and phosphorus trichloride provides 2-benzyl-3-chloropyrido[2,3-b]pyrazine. This precursor is then transformed into the target O-acetylated luciferin (6,8-dibenzylimidazo[1,2-a]pyrido[3,2-e]pyrazin-9-yl acetate). The ‘benzo’ derivative of this analogue (i.e., 2,12-dibenzylimidazo[1′,2′:1,6]pyrazino[2,3-c]isoquinolin-3-yl acetate) is also prepared and the chemiluminescence emission spectra of these compounds are determined in a phosphate buffer (λmax = 546 and 462 nm).

5-Aminofuro[3,2-c]pyridinium Tosylates and Substituted Furo[3,2-c]pyridine N-Oxides: Synthesis and Reactions

5-Aminofuro[3,2-c]pyridinium tosylates 2a-2c were synthesized by direct N-amination of furo[3,2-c]pyridines 1a-1c with O-(4-methylbenzenesulfonyl)hydroxylamine in dichloromethane. Zwitterionic furo[3,2-c]pyridinium N-imides 3a-3c generated from 2a-2c and anhydrous potassium carbonate in N,N-dimethylformamide afforded by 1,3-dipolar cycloaddition reactions with dimethyl butynedioate or ethyl propiolate the corresponding furo[3,2-c]pyrazolo[1,5-a]pyridinecarboxylic esters 4a-4c and 5a-5c. Furo[3,2-c]pyridine N-oxides 6a-6c and their benzo derivative 6d were synthesized by reaction of 1 with 3-chloroperbenzoic acid in dichloromethane. Treatment of N-oxides 6 with benzoyl chloride and cyanide anion (Reissert-Henze reaction) was shown to produce the corresponding furo[3,2-c]pyridine-4-carbonitriles 7. In further transformations (acid and alkaline hydrolysis), the cyano group was converted successively to amide and carboxylic acid.

Struktur und Magnetismus stabiler Radikalkation-Salze: Ν,N′-Diethylchinoxalinium Tetraphenylborat im Vergleich mit Pyrazinium- und Phenazinium-Analogen / Structure and Magnetism of Stable Cation Radical Salts: N,N′-Diethylquinoxalinium Tetraphenylborate as Compared with Pyrazinium and Phenazinium Analogues

Crystal and molecular structure analysis of N,N′-diethylquinoxalinium tetraphenylborate shows a virtually planar quinoxaline ring with 11 conjugated π electrons and approximately antiperiplanar ethyl groups. In comparison with the benzo-analogous phenazinium systems and the de-benzo derivative N,N′-diethylpyrazinium cation, the quinoxalinium species adopts an intermediate position in terms of intra- and intermolecular structural features. In particular, increasing benzanellation seems to favour a cation/anion approach for electrostatic reasons whereas the N—C bonds to the hyperconjugatively charge delocalizing alkyl groups increase due to peri interactions. Solid state magnetic and ESR measurements are compatible with the crystallographically determined structure.