A short and efficient construction of the dibenzo[c,h]chromen-6-one skeleton

We hereby report a major revision of the synthetic methodology for construction of the dibenzochromenone skeleton. Homophthalic acid derivatives were reacted with thionylchloride/DMF in the presence of NaN3. As the main product, dibenzochromenone derivatives were obtained. When the reaction was performed in the absence of NaN3, only isochromenones were formed. The mechanism of the formation of these products is discussed.