Transformation of barakol into cassiarins A, B, and their derivatives

Three semi-syntheses of cassiarins A and B from barakol are described. The route involving use of anhydrobarakol chloride as a key precursor showed most versatility because it does not require an expensive catalyst, protection of functional groups, or chromatographic purification, allowing the facile preparation of eight cassiarin derivatives. The photophysical properties of these compounds were characterized by UV–vis absorption, fluorescence emission, and quantum yield.