Synthesis of naphthothiophene derivatives through polar Diels-Alder reactions employing 5-nitrobenzothiophene as electrophile. Microwave irradiation vs classical thermal conditions

Herein we report a simple, economical and efficient one-step procedure to synthesize the naphtho[2,1-b]thiophene ring system in good to excellent yield through the polar Diels-Alder reactions of 5-nitro-3-acetylbenzothiophene and dienes of different nucleophilicity. In thermal conditions the reactions were developed in molecular solvents; moreover the reaction system was exposed to microwave irradiation as a complement of reaction conditions.