Synthesis of New 4-(3,4,5-Trimethoxyphenyl)-3H-Furo[3,4-b]Carbazole-3-Ones Derivatives

New 1,5-Dihydro-4-(3,4,5-trimethoxyphenyl)-3H-furo[3,4-b]carbazol-3-ones were synthesized via a key Diels-Alder reaction under microwave irradiation. Two routes were investigated to generate the dienoic precursors. Both started from 3-formylindole, which was used in a six steps synthesis to obtain the complex heterocycle. The use and removal of indolic protective groups such as t-Boc and benzenesulfonyl have been studied. The Diels- Alder reaction generating the carbazole ring was optimised under either thermal conditions or microwave irradiation.