Polyfunctionalized cage compounds by pericyclic domino processes of 4,5-dicyanopyridazine with dienes: applications and limits

The title compound 1 was found to behave as an attractive masked bis-diene to give 4-oxatricyclo4.3.1.0(3,7)]dec-8-ene, 5-aza- and 5-silatricyclo5.3.1.0(3,8)]undec-9-ene, tricyclo3.2.1.0(2, 7)]oct-3-ene, and tricyclo5.3.1.0(3,8)]undec-9-ene derivatives through purely pericyclic, three-step homodomino processes with diverse bis-dienophiles; whereas the reaction with myrcene (21) was characterized by a complete sitoselectivity affording compound 25, treatment of 1 with (R)-(-)-beta-citronellene (26a) gave a 3:1 mixture of the homochiral diastereomers 30a and 31a. Some limits of this methodology, mainly arising from competitive side reactions upon the key cyclohexa-1,3-diene intermediates, are emphasized. The structures of the new compounds were established on the basis of spectral data.