Cycloaddition of dialkylgermoles: synthesis and structures of 2,2,3,3-tetracyano-1,4,5,6-tetraphenyl-7-germanorborn-5-enes

Cycloaddition reactions of 1,1-dicyclopropyl-2,3,4,5-tetraphenyl-1-germacyc lopentadiene (3) with dehydrobenzene, tetracyanoethylene, cyclooctyne, or d imethyl acetylenedicarboxylate as well as of 1,1-dimethyl-2,3,4,5-tetraphen yl-1-germacyclopentadiene (4) and 2,3,4,5-tetraphenyl-1-germacyclopentadien e (5) with tetracyanoethylene or cyclooctyne were studied. Diels-Alder addu cts of germoles 3, 4, and 5 with tetracyanoethylene were prepared. The stru ctures of these adducts were established by X-ray diffraction analysis and their thermal and photochemical stabilities were examined.