No abstract

Pyrazine derivatives R 0550New Method for the Anellation of the Pyridine Fragment to Azines. -An intramolecular reaction is used as key step for the anellation of a pyridine ring to quinoxalines leading to compounds of type (III) which are fragments of many highly active antibacterial drugs. -(CHARUSHIN*, V. N.; BOGUSLAVSKY, A. M.; PONIZOVSKY, M. G.; KODESS, M. I.; CHEKHLOV, A. N.; MKOYAN, S. G.; ALDOSHIN, S. M.; Russ.

The 'H and uC NMR spectra of tetrahydroquinoxalines condensed with pyridazme, pyrazine, oxazine, oxadiazine, thiadiazine or triazine rings have been measured in DMSO-d, solution. The effects of six-membered heterocycles on 'H and uC chemical shifts and the values of one-bond 'J(CH) and vicinal 3J(HH) coupling constants for the ring junction fragment are considered. The differences between the 'H and =C spectral parameters of tetrahydroquinoxalines aunelated with five-or six-membered heterocycles with the same set of heteroatoms attached to the ring junction carbons are also discussed.

No abstract

Synthesis of Fused Quinoxalines. -A new methodology for the synthesis of pyrazoloquinoxalines [cf. (VI), (VII)] based on the intramolecular cyclization of N-alkyl and NH quaternary salts of quinoxaline-2-carboxaldehyde hydrazones is developed. Scope and limitations of the promising methodology are established. -(PONIZOVSKY, MICHAIL G.; BOGUSLAVSKY, ARTEM M.; KODESS, MIKHAIL I.; CHARUSHIN, VALERY N.; CHUPAKHIN, OLEG N.; Mendeleev Commun. (