[2.2](2,6)‐ and [2.2](2,5)Pyrazinophanes: Synthesis and Molecular Structure

The title compounds 1 – 3 and their methyl derivatives 4 – 7 were synthesized 2,11‐dithia[3.3]pyrazinophanes 24 – 26 or by Hofmann 1,6‐elimination of the appropriate [(5‐methyl‐2‐pyrazinyl)methyl]trimethylammonium hydroxides followed by dimerization of the generated 2,5‐dihydro‐2,5‐dimethylenepyrazines. α‐Chlorination of the methylpyrazines 8 – 10 with N ‐chlorosuccinimide gave the required precursors 11, 12, 14, 17 and 18 . The results of the X‐ray structure determinations for 1 – 4 and 7 which indicate an unequivocal isomer assignment are discussed with regard to steric strain in these molecules. The electronic spectra of the pyrazinophanes 7 – 7 are reported and compared with those of the parent methylpyrazines.