Functionalization of arenes is a topic of central importance in diverse fields ranging from medicinal chemistry to materials science. Metal-catalyzed cross-coupling and nucleophilic aromatic substitution are among the most reliable methods to access functionalized arenes. In these reactions, haloarenes are often used as a versatile synthetic platform to introduce various functional groups. However, haloarenes are typically prepared from the corresponding nitroarenes through the classic sequence of reduction, diazotization, and halogenation. Thus, haloarene cross-coupling can become a multistep transformation overall. To avoid this lengthy sequence, the direct utilization of nitroarenes has the potential to significantly streamline synthetic processes and, therefore, has attracted attention in the chemistry community from the vantage points of atom- and step-economy. In this Review, we comprehensively cover advances in transition-metal-catalyzed denitrative reactions of nitroarenes.

A Ni-catalyzed decarbonylative methylation of aromatic esters was achieved using methylaluminums as methylating agents. Dimethylaluminum chlorides uniquely worked as the methyl source. Because of the Lewis acidity of aluminum reagents, less reactive alkyl esters could also undergo the present methylation. By controlling the Lewis acidity of aluminum reagents, a chemoselective decarbonylative cross-coupling between alkyl esters and phenyl esters was successful.

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A Pd-catalyzed intramolecular C−H arylation of nitroarenes has been developed. Nitroarenes bearing tethered aryl groups at the ortho-position can be readily prepared in one step from 2-halonitroarenes by a nucleophilic aromatic substitution (S N Ar). Under Pd/BrettPhos catalysis, activations of the C−NO 2 bond as well as the C−H bond on arenes generated the corresponding biaryl linkage in moderate to excellent yields.

Iron carbonyl promoted reaction of , , ', 'tetrabromoacetone and cyclic 1,3-dienes followed by Zn-Cu couple reduction formally corresponds to a [3 + 4 -7] cycloaddition of unsubstituted oxyallyl and dienes; synthesis of a-and Rthujaplicins using the cyclocoupling reaction as key step has been achieved.Sir: Reaction of , '-dibromo ketones 1 with Fe2(CO)2 generates the oxyallyl-Fe(II) species 2 (L = Br, CO, solvent, etc.) as reactive intermediate.2 Its use in the synthesis of various cyclic systems has been demonstrated recently.3The limits were defined clearly by the type of the starting dibromides employable for the reaction. Secondary and tertiary dibromo ketones react with 1,3-dienes in a [3 + 4 -> 7] manner to produce 4-cycloheptenones in good yields.3a,d However, attempted reactions with , '-dibromoacetone (1, R = H) were totally unsuccessful;4 dibromides de-