Diamino-2,3-dimethylbutane

Diamino-2,3-dimethylbutane (200) and diethyl a-oxomalonate (201) gave ethyl 5,5,6,6-tetramethyl-3-oxo-3,4,5,6-tetrahydro-2-pyrazinecarboxylate (202) (EtOH, 20°C, 45 h then reflux, 7.5 h 83%).455 Also other examples.956,1269,1752... 

The preparation of some 2,3-dihydropyrazines from a, -dicarbonyl compounds with a,0-diamino compounds has been recorded in Section 11.2 (330, 330a, 331, 333, 334, 338-344, 349, 356, 357), with further data given in references 6, 337, 345, and 1547-1549. In addition hexamethyl-2,3-dihydropyrazine (16) has been prepared from 2,3-diamino-2,3-dimethylbutane and butane-2,3-dione (1550). Condensation of oxalyl chloride with diiminosuccinonitrile (10) in ether has been shown to give 2,3-dichloro-2,3-dicyano-5,6-dihydroxy-2,3-dihydropyrazine (17) (383). 

Recently Keana and co-workers (1978) suggested a new method of synthesizing imidazolidine nitroxides. According to this method, condensation of 2,3-diamino-2,3-dimethylbutane with a ketone in the presence p-toluenesulfonic acid leads to imidazolidine 16. Oxidation of the latter with m-chloroperbenzoic acid gives the corresponding nitroxide 17, with a... 

Hydrolysis and racemization of [Co(tmen)3] (tmen = 2,3-diamino-2,3-dimethylbutane) follow the rate law, rate = fc[Co(tmen)3+][OH ] in the pH range 4.8 to 13.8. For base hydrolysis, fcoH = 2.5 0.8dm mol" s at 25 °C, with = 132kJmol- , A5+= 144 J mol-, and AF+= 57.6 cm mol". A conjugate base mechanism Dcb is assigned to the hydrolysis reaction which occurs from the singly deprotonated complex via a five-coordinate intermediate, followed by rapid dissociation of the tran -Ugand and cis-trans isomerization to the final product trans-[Co(tmen)2(H20)2] . Rate constants and activation parameters have also been obtained for the racemization reaction. The racemization reaction has k = TTi dm mol" s" at 25 °C and is faster than base hydrolysis. For the faster racemization, deprotonation is followed by the inversion process without Co—N bond... 

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