318 T HE CHEMISTRY OF 3 - NITROCHROMENES DOI: http://dx.medra.org/ 10.17374/targets.2019.22.318 Robby Vroemans , Wim Dehaen* Molecular Design and Synthesis, Depa rtment of Chemistry, KU Leuven, Celestijnenlaan 200F, 3001 Leuven, Belgium (e - mail :
[email protected] ) Abstract. A large variety of natural products and medicinal drugs have chromene and chromane core s incorporated in their structures . Because of their high and versatile reactivity , and simple synthesis , 3 - nitrochromenes are regarded as an easily available and highly functional constituent for the preparation of chromene and chromane derivatives . In the present review , t he synthesis of the 3 - nitr ochromene scaffold is briefly discussed . The multifaceted reactivity of 3 - nitrochromenes is highlighted and divided in to different subject s in which emphasis is mainly placed on recent advances in literature from 2013 up until now . Contents 1. Introduction 2. Synthesis of 3 - nitrochromenes 3. Reactivity of 3 - n itrochromenes 3 .1. Oxidations 3 .2. Reductions 3 .3. Conjugate additions 3.4. Cycloaddition reactions 4. Conclusion s Acknowledgement References 1. Introduction Chromenes (2 H - benzo[ b ]pyrans) have been of considerable interest for a long period of time and remain omnipresent in various fields such as medicinal chemistry and natural products . 1 - 4 Characterization of natural products proved that chromenes are common patterns in many biological systems . 3 Some important examples of naturally occurring chromenes and chromanes are α - tocopherol (one out of eight compounds featuring vitamin E activity) , 5 - 8 tetrahydrocannabinol (THC) , 9 - 12 a rahypin - 5, 13,14 c alanone 15 and s eselin 16 (Figure 1).