1.2- dicyano-1,2 ethylene, cycloaddition with

A synthetically useful pressure-induced increase of diastereoselectivity was also found for normal Diels-Alder reactions such as the cycloaddition of the phenyl butadienes (93a-c) with the dicyano ethylenes (94-97) to yield the ds-adducts 98a-d, lOOa-d and 102a-d as well as the trous-adducts 99a-d, lOla-d and 103a-d (Scheme 8.24) [54]. 

Allyltrimethylsilanes react with triplet excited 2,3-dicyano-5,6-dimethylpyra-zine to give diazatricyclooctenes (115), possibly via intermediate (114) formed from ring-opening of an initially-formed [2+2]adduct. Intramolecular [2+2]-cycloaddition yields the pentacyclic compound (116) on irradiation of the corresponding tethered enantiopure bis-2,3-dihydro-4-pyridone. Addition of ethylene to the corresponding a,P-unsaturated-y-lactams in acetone yields (117) and (118) as the major photoproducts. ... 

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