[2.2](2,6)PYRAZINOPHANES 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. Copyright © 1990 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim