2.2.5.5- Tetramethyl-2,5-dihydropyrazine

Bis(hydroxyamino)-2,3-dimethylbutane (160) and glyoxal gave 2,2,3,3-tetramethyl-2,3-dihydropyrazine 1,4-dioxide (161) (H20—EtOH, reflux, 10 min 83% naturally not subject to facile oxidation).702 Also other examples.1,86 237 414,466,483 588 988 1108... 

Tetramethyl-2,3-dihydropyrazine 1,4-dioxide (303) gave 2,2,3,3-tetram-ethyl-l,4-piperazinediol (304) (NaBH4, H20, 20°C, 24 h 81% homologues likewise).702 Also analogous reductions.702... 

Interatomic distances as calculated from the analysis of the rotational fine structure of the ultraviolet spectrum are C-C, 1.395 A C-N, 1.341A and C-H, 1.085 A.66 These are very similar to the bond lengths for pyridine which are C-2-C-3, 1.3945 A C-3-C-4, 1.3944 A and C-2-N, 1.3402 A. The C-N-C bond angle in pyrazine is 115° and the C-C-N bond angle 122.5°.56,67 A delocalization energy for pyrazine of ca. 18 kcal/mole is indicated from heats of combustion data.68 The C=N bond energy in 2,2,5,5-tetramethyl-2,5-dihydropyrazine has been calculated to be 130.3 kcal.58a... 

Methylated 1,4-dihydropyrazines (1,2,4-tri-, 1,2,4,5-tetra-, and 1,2,4,6-tetramethyl) as well as imidazolines have been isolated from the reaction of sucrose with methylamine at high temperatures (120°-260°), for prolonged reaction periods (18 hours) and in the presence of ammonium phosphate as catalyst. 1,4-Dihydropyrazines are also isolated from the reaction of sucrose and ethanolamine sucrose-ammonia interaction yields a wide range of pyrazines and imidazoles.369-372... 

Irradiation of 1,3,5,6-tetramethyl-2-oxo-l, 2-dihydropyrazine (88) in tetrahydro-furan produced an unstable photoisomer which can be trapped by hydrogenation to 1,2,4.6-tetramethyl-3-oxo-2,5-diazobicyclo[2,2,0lhexane (89) (1131). 

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