Steric hindrance prevented
formation of tetra-t-butylpyrazine either when pivaloin was heated with
ammonium acetate or when pivalil monooxime was reduced with zinc and alkali.
Diminution of the steric hindrance of the t-butyl groups by masking them by
incorporation into a seven-membered ring containing sulphur was of no avail.
2,5-Di-t- butylpyrazine resulted from the analogous reduction of t-butyl-glyoxal
dioxime and could be converted into its N-oxide and N,N?-dioxide. t- Butyl-lithium
reacted with the pyrazine and the mono-N-oxide to give a mixture of products
including 2,3,5-tri-t-butylpyrazine whose spectroscopic properties suggested a buckling
of the pyrazine ring. Benzonitrile and diphenylacetylene reacted independently
in the presence of iron pentacarbonyl and gave, inter alia, 2,4,6-triphenyl-
1,3,5-triazine and hexaphenylbenzene respectively. ��� The most prominent features of the low
resolution mass spectra of these pyrazines and some of their precursors are
discussed and rationalized.