Azodicarboxylic acid Diels-Alder reactions

In common with other azodicarboxylic acid derivatives, the uses of 4-phenyl-l,2,4-triazoline-3,5-dione are many. It undergoes a Diels-Alder reaction with most dienes11-14 and is, in fact, the most reactive dienophile so far reported.15 16 As with the formation of all Diels-Alder adducts the reaction is reversible, and in the case of the adduct with 3-j3-acetoxy-17-cyano-5,14,16-androstatriene, the reverse reaction can be made to proceed under especially mild conditions.14 An instance has also been reported of the dione photochemically catalyzing other retro Diels-Alder reactions.17 Along with the proven use of azodicarboxylic ester,18-18 the dione should be potentially important in the preparation of strained ring compounds. 

Alternatively, the 5,6-double bond in the initial adduct can be elaborated via Diels-Alder reactions with cyclopentadiene derivatives and this provides an entry to the tetracy-clo[5.2.1.0 0 ]decane series. Hence reaction of the diethyl azodicarboxylate adduct with hexachlorocyclopentadiene gave the adduct 13 which was elaborated to give endo,syn-l,7,8,9,10,10-hexachlorotetracyclo[5.2.1.0 0 ]dec-8-ene (14). Similar syntheses yield derivatives with a variety of substituents at CIO and in this series it was found that sulfuric acid hydrolysis of the carbamates gave a better yield than sodium hydroxide in methanol. The... 

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