By Replacement of Alkoxy, Cyano, Nitro, or Oxo Substituents

There have been few recent reports on the introdnction of an alkyl gronp into the pyrazine nuclens by displacement of a non-halogeno snbstituent. However, the following examples indicate that this possibility shonld not be ignored  

2-Methoxypyrazine (142) gave 2-(oi-cyanobenzyl)pyrazine (143) (PhCH2CN, NaH, THF, reflnx, 30 min then substrate J, reflux, N2, TLC monitored 46%). ° other carbanions seem to have been less successful.  

6-Diphenyl-2,3-pyrazinedicarbonitrile (145) gave 3-allyl-5,6-diphenyl-2-pyrazinecarbonitrile (144) (Me2SiCH2CH=CH2, MeCN, hv, A, 70 h 98% with a trace of phenanthrene as sensitizer, only 25 h was required) or 3-ben-zyl-5,6-diphenyl-2-pyrazinecarbonitrile (146) (Me3SiCH2Ph, trace phenanthrene, MeCN, hv. A, 25 h 98%).i  

2-Bromo-5-nitropyrazine (147) gave 2,5-bis(l,l-dicyanopent-4-ynyl)pyrazine (148) 11 1 ( II-CIKCN)-. NaH, THF, Nj, 20°C, 20 min substrate,  

6-Benzyl-2,3,5-piperazinetrione (149, X = 0) gave 3-benzyl-6-methoxycarbonyl-methylene-2,5-piperazinedione (149, X = CHCO2Me) ( Pti,l =CtlCO2Me, PhMe, reflux, 19 h 60%) also analogues.  

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