Bicyclo octa-2,4,7-triene Diels-Alder reactions

Norbornadiene adds typical dienophiles in a homo-Diels-Alder reaction whereby, for example, the adduct 86 is obtained with tetra-cyanoethylene. Dimethyl acetylenedicarboxylate and dicyanoacetyl-ene add to barrelene (bicyclo[2.2.2]octa-2,5,7-triene) in a similar way. °... 

A later study revealed that cis,trans,cis-, 3,S-cycloocidXntwQ generated by a retro Diels-Alder reaction of its furan adduct gave only bicyclo[4.2.0]octa-2,7-diene at 180°C which underwent subsequent ring opening to the all cis-cyc ic triene (Scheme 9.38)7 ... 

Deuterium isotope effects have been studied for the Diels-Alder reactions between hexadeuterio-monosubstituted cyclo-octatetraenes (283) and several reactive dieno-philes leading to adducts (284). With dicyanomaleimide, isomerization of the cyclo-octatetraene to the bicyclo[4,2,0]octa-2,4,7-triene is the rate-determining step, but with the less reactive dienophiles (maleic anhydride and tetracyanoethylene) larger... 

COT undergoes an electrocyclization to bicyclo[4.2.0]octa-2,4,7-triene (BOT) as evidenced by the structure of the Diels-Alder adduct when COT is treated with dieneophiles. That the dieneophile does not induce this reaction was demonstrated by Huisgen who found that the rate of formation of the adduct with high concentrations of very reactive dieneophiles is independent of dieneophile concentration (Scheme 9.7). ... 

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