Studies directed toward total synthesis of rhodocomatulins: A regioselective synthesis of brominated hydroxyanthraquinones by anionic annulations

ABSTRACT

In this work, brominated hydroxyanthraquinones, which are the core structural motif of naturally occurring bromorhodocomatulins, were successfully synthesized using Hauser annulation reaction as the key step. When brominated Michael acceptors (brominated p-quinone monoketals) and cyanophthalides or bromocyanophthalides (Hauser donors) were reacted under the annulation conditions, brominated anthraquinones were obtained with 81–87% yields for four examples. On acidic quenching, products were obtained as solid which were separated by filtration and purified by recrystallization in acetone. No chromatography was required.

GRAPHICAL ABSTRACT

KEYWORDS:

• Brominated hydroxyanthraquinones
• Hauser annulation
• rhodocomatulins

Additional information

Funding

We gratefully acknowledge the Council of Scientific and Industrial Research (CSIR) for financial support (02(0183)/14/EMRII), and The Department of Science and Technology (DST) for instrumental facilities. Md Raja Sk is thankful to IIT Kharagpur and Soumen Chakraborty is thankful to CSIR for his research fellowship.