I 2 /DMSO mediated Cascade cyclization reaction of amino coumarins with aryl methyl ketones: Access to Dicoumarino‐fused [1,5]‐diazocine and pyrrolo‐coumarin scaffolds

Abstract An easy metal‐free cascade cyclization of 4‐amino coumarin with aryl methyl ketone has been developed as a straightforward method for constructing coumarino‐fused [1,5]‐diazocines. This chemical transformation affords linearly fused structure of coumarin and 1,5‐diazocine with significant yield. Such complex hybrid diazocine skeletons can propose various bioactivities in drug design. The technique is highly appealing, sustainable, and economic since it is operationally simple and uses a catalytic quantity of iodine in presence of DMSO. In this protocol, DMSO functions both as a solvent and an oxidant. Again, the sustainability of this protocol is enhanced as it is devoid of any exogenous oxidant. Further functionalization of these diazocine moieties using metal catalyzed cross coupling techniques lead to several interesting scaffolds. Furthermore, these diazocine compounds can undergo a base‐controlled regioselective metal‐free Chan‐Lam type coupling reaction, yielding novel N‐arylated and O‐arylated products. Additionally, the formation of densely functionlized coumarin fused pyrrole scaffolds from 3‐aminocoumarin and aryl methyl ketone widens the practical applicabilty of this protocol. This pyrrolo‐coumarin frameworks are present in the bio‐active marine alkaloid, lamellarins.