Synthetic protocols on 6H-benzo[c]chromen-6-ones: A review

6H-Benzo[c]chromen-6-ones serve as core structures of secondary metabolites and are of considerable pharmacological importance. Natural sources produce limited quantities, hence the need for synthetic procedures for 6H-benzo[c]chromen-6-ones, which are herein reviewed. The literature describes protocols such as the Suzuki coupling reactions for the synthesis of biaryl, which then undergoes lactonization, reactions of 3-formylcoumarin (chromenones) with 1,3-bis(silylenol ethers), radical mediated cyclization of arylbenzoates, metal or base catalyzed cyclization of phenyl-2-halobenzoates and 2-halobenzyloxyphenols, and benzoic acid coupling with benzoquinone using electrophilic metal- based catalyst. The efficient and simple procedures are those involving the reactions of Michael acceptor (chromenones and chalcones) with 1,3- and 1,5-dicarbonyl compounds.