POLYCYCLIC HYDROXYQUINONES. XXIV. DIELS-ALDER REACTONS OF 5-AMINO-8-HYDROXY-1,4-NAPHTOQUINONE. NOVEL TRANSCYCLOADDITION REACTIONS WITH DERIVATIVES OF 1,4-DIHYDRO-1,4-METHANOANTHRACENE-9,10-DIONE.

Article abstract of DOI:10.1016/S0040-4020(01)87657-2

Diels-Alder reactions of 5-amino-8-hydroxy-1,4-naphtoquinone (1a) and derivatives (1b-e) with cyclopentadiene and 2,3-dimethylbuta-1,3-diene afford the corresponding adducts 2a-e and 4a-e in good yields.Adducts 2a and 4a, by oxidation under alkaline conditions in the presence of air, are converted into quinones 3a and 5a, respectively.Quinone 3a undergoes a novel transcycloaddition reaction with 2,3-dimethylbuta-1,3-diene, which involves cycloaddition to give the angular adducts 7_n and 7_x, followed by cycloreversion to afford 5a and cyclopentadiene.Quinone 3a similarly undergoes a transcycloaddition with diazomethane to yield a single benzindazol 9.The reverse regiochemistry is observed starting from the O,N-diacyl derivative 3e.Similar transcycloadditions with 5,8-dimethoxy-1,4-dihydro-1,4-methanoanthracene-9,10-dione are reported.