2-Pyrazinyl

Indolylboronic acid (21), easily obtained from commercially available 5-bromoindole, was coupled with 2-chloropyrazine (13) to efficiently furnish 5-(2-pyrazinyl)indole (22) [18]. 

Many papers deal with both analytical determination and cathodic transformations of thiones (21). Thus, a four-electron reduction of OLTIPRAZ [4-methyl-5-(2-pyrazinyl)-l,2-dithiole-3-thione] produces several species that could account for the schistosomicidal activity of metabolites of the starting compound. The first two-electron reduction (in aqueous media) affords the scission of the S —S linkage and the thus formed dianion can be readily [197] alkylated by common alkyl halides. Let us note that the cathodic behavior of structure (21) was shown to be strongly influenced by the nature of substituents and particularly [198] by the electron-donating ability of Rh... 

In contrast, when a twofold excess of the dialkoxydihydropyrazine is used, then 2 1 adducts are obtained. This has been demonstrated18 by reacting A,7V-bis(2-iodoethyl)-4-methylben-zenesulfonamide with two equivalents of the lithiated D-valine/alanine-based dialkoxydihydropyrazine 8 to give 7V.fV-bis 2-[(2S,57 )-2,5-dihydro-5-isopropyl-3,6-dimethoxy-2-mcthyl-2-pyrazinyl]ethyl -4-methylbenzenesulfonamide (9) in high yield and >95% de. The adduct can be hydrolyzed in high yield to the corresponding amino acid methyl ester 10. 

Beim kurzen Erhitzcn in waBriger Natronlauge dehydratisiert 3-Amino-2-(amino-benzoyloxi-mino-methyl)-pyrazin in guter Ausbeute zu 3-(3-Amino-2-pyrazinyl)-2-phenyl-l,2,4-oxadi-azol (77% Schmp, 220-2230)211 ... 

Ebenfalls regioselektiv in 2-Stellung verlauft die Methylierung von 3-Amino-5-(2-pyrazinyl)-1,2,4-oxadiazolen zum Onium-Salz171 ... 

Depending on the /V-substituent. indole was arylated selectively in the 2-or 3-position. Starting from A -mcthylindolc Ohta and co-workers obtained the 2-pyrazinyl-indole derivative in good yield (6.88.).119 Increase of the steric bulk of the A -substitucnt diverts the incoming aryl moiety into the 3-position. 

Keywords ethyl 4-[2-(2-pyrazinyl)ethenyl]cinnamate, photopolymerization, cyclobutane... 

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