Preparation of 1,4-Naphthoquinones and 9,10-Anthraquinones through Brønsted Acid-Catalyzed [4+2] Cycloaddition

High Resolution Image Download MS PowerPoint Slide We report the synthesis of substituted 1,4-naphthoquinones (1,4-NQs) and 9,10-anthraquinones (9,10-AQs) via Brønsted acid-catalyzed [4+2] cycloaddition of simple butadienes and p -benzoquinones to give 5,8-dihydro-1,4-NQs under ambient conditions in up to 90% yield. Subsequent dehydrogenation gives the corresponding 1,4-NQs (62–98%), while a second Brønsted acid-catalyzed [4+2] cycloaddition (that can be performed in one pot) generates 1,4,5,8-tetrahydro-9,10-AQs (71–88%). This enables the synthesis of a variety of highly substituted quinones and acenes.