Reactions of 5,6,7,8-tetrahalogeno-1,4-dihydronaphthalen-1,4-imines with dimethyl acetylenedicarboxylate

Isomeric 1 : 1 adducts obtained from tetrachlorobenzyne and N-t-butylpyrrole are a naphthalen-1,4-imine and a benzo[3,4]cyclobuta[1,2-b]pyrrole derivative. The former (5) decomposes thermally by a retro-Diels–Alder reaction to give an isoindole (17), which forms another naphthalen-1,4-imine (6) by addition of dimethyl acetylenedicarboxylate. 5,6,7,8-Tetrafluoro-1,4-dihydro-1,4-methyliminonaphthalene (1) reacts with the acetylene ester to give two simple naphthalene derivatives, a benz[g]indole (18) and a benzo[de]quinoline (26). Adducts are obtained from 5,6,7,8-tetrachloro-1,4-dihydro-1,4-methyliminonaphthalene (2) with benzyne, dibenzoylacetylene, and dimethyl acetylenedicarboxylate. Unusually large long-range H–F and C–F nuclear spin interactions are observed for two fluorinated benz[g]indole derivatives (18) and (22).