Convenient Synthesis of 2-Allyl-3-bromo-1,4-dimethoxynaphthalene: Key Intermediate as Building Block for Bioactive Pyranonaphthoquinones

Abstract

Synthesis of a key precursor 2-allyl-3-bromo-1,4-dimethoxynaphthalene (1) used in constructing various naturally occurring biologically active pyranonaphthoquinones is carried out utilizing easily available 1-methoxynaphthalene as a starting material. The synthesis was accomplished with Dakin's oxidation and Claisen rearrangement, thereby providing another easy approach toward (1) without involving highly lachrymatric 2-bromonaphthoquinone.

GRAPHICAL ABSTRACT

Keywords:

• 2-Allyl-3-bromo-1,4-dimethoxynaphthalene
• Claisen rearrangement
• Dakin's oxidation
• pyranonaphthoquinones

ACKNOWLEDGMENTS

We are grateful to S. G. Gupta for making the laboratory facilities available and to the Department of Science and Technology–Funding for Structure in Science and Technology (DST-FIST) for instrumentation support. R. A. L. thanks the University Grants Commission for providing a junior research fellowship and the Department of Chemistry, University of Pune, for spectral analysis. Thanks are also due to R. C. Chikate and V. B. Kumbhar for helpful discussions.