Regiospecific hetero Diels-Alder synthesis of furo[2,3-g] and furo[3,2- g]quinoline-4,9-diones

Article abstract of DOI:10.1016/0040-4020(96)00484-X

Diels-Alder reactions of 5- or 6-bromobenzofuran-4,7-diones 7 or 10 towards azadienes 1 afford regiospecifically furo[2,3] or furo[3,2- g]quinoline-4,9-diones 3 or 4. Assignment of the regioisomers, made by 2D NMR ¹H-¹³C HMBC experiments, showed that the regiochemistry of the cycloadditions is under control of the bromine atom position. Calculations by the semiempirical method PM3 of the HOMO and LUMO orbital coefficients of azadienes 1 and quinones 2 indicated that the larger ones are situated at C- 4 for 1 and C 5 for 2.