Decomposition of a tetrahydromethanophthalazine: retro-diene reaction versus nitrogen elimination, and electrocyclic transformation of a derived tricyclo[6,1,0,02,7]nonadiene

Abstract

exo-3,4,5,6-Tetrachloro-9,10-diazatricyclo[6,2,1,0^2,7]undeca-3,5,9-triene (tetrachlorotetrahydromethanophthalazine)(VIII) decomposes thermally by retrogressive Diels–Alder reaction: under u.v. irradiation elimination of nitrogen from (VIII) gives syn- and anti-3,4,5,6-tetrachlorotricyclo[6,1,0,0^2,7]nona-3,5-diene, (IX) and (X).