Diazabenzenes. I. Synthesis of some t-butylpyrazines and their N-oxides

Abstract

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.