Diels‐Alder‐Reaktionen bissilylierter 1,3‐Diketone mit Azodienophilen

Diels‐Alder Reactions of Bissilylated 1,3‐Diketones with Azo Dienophiles The 1,3‐bis(tert‐butyldimethylsilyloxy)‐1,3‐butadienes 2a and 2b are obtained by double silylation of the 1,3‐diketones 1a and 1b. The dienes 2a and 2b react with various azo dienophiles to yield the Diels‐Alder adducts 3a–f. Hydrolysis of these compounds leads to the new heterocycles 4a–f. Of these 4b and 4d are silylated to form the cyclic dienes 5 and 7, respectively. Compound 5 reacts with 3,5‐dihydro‐4‐phenyl‐4H‐1,2,4‐triazole‐3,5‐dione to give, after hydrolysis, the adduct 6. Photolysis of 7 followed by desilylation yields the pyrrolinone derivative 11.