Thermal and photochemical additions of azo esters to unsaturated systems-II: additions to olefins and dienes

Abstract

Thermal and photochemical additions of diethyl azodicarboxylate to cycloheptene and cyclooctene gave 3-(diethylbicarbamyl)-1-cyclobeptene and 3-(diethylbicarbamyl)-1-cyclooctene, respectively. A free-radical mechanism has been suggested for these additions. 1-Methylcyclohexene, on treatment with diethyl azodicarboxylate both under thermal and photochemical conditions, gave a mixture of products consisting of 2-(diethylbicarbamyl)-1-methylenecyclohexane and 3-(diethylbicarbamyl)-1-methylcyclohexane. The reaction of trans-1,2-dicarbethoxycyclohexa-3,5-diene gave a poor yield of the Diels-Alder adduct under thermal conditions; the same product was obtained in much better yields under photochemical conditions. The reaction of cyclohexa-1,4-diene with diethyl azodicarboxylate under irradiation conditions gave 3-(diethylbicarbamyl)-cyclohexa-1,4-diene and diethyl hydrazodicarboxylate. Cycloocta-1,5-diene reacts with diethyl azodicarboxylate, both under thermal and photochemical conditions to give 3-(diethylbicarbamyl)-cycloocta-1,5-diene, a radical substitution product. An attempted reaction of anthracene with diethyl azodicarboxylate, under irradiation conditions, gave none of the expected addition product, but only a photodimer of anthracene.