Ipso Nitration of Aryl Boronic Acids Using Fuming Nitric Acid.

The ipso nitration of aryl boronic acid derivatives has been developed using fuming nitric acid as the nitrating agent. This facile procedure provides efficient and chemoselective access to a variety of aromatic nitro compounds. While several activating agents and nitro sources have been reported in the literature for this synthetically useful transformation, this report demonstrates that these processes likely generate a common active reagent, anhydrous HNO3. Kinetic and mechanistic studies have revealed that the reaction order in HNO3 is >2 and indicate that the •NO2 radical is the active species.

A highly efficient palladium/copper cocatalytic system for direct arylation of heteroarenes: an unexpected effect of Cu(Xantphos)I.

Heteroarenes are important structural moieties in many chemical industry fields. A highly efficient Pd/Cu-catalyzed C-H arylation method for a range of heterocycles has been discovered. It was found that the key to the success of this transformation is a combination of a palladium catalyst and a well-defined copper cocatalyst. The efficiency and low loadings of catalyst (0.25 mol %) and cocatalyst (1 mol %) together with the mild reaction conditions demonstrate this method to be practically useful and mechanistically interesting.

1,1'-Carbonyldiimidazole (CDI) Mediated Coupling and Cyclization To Generate [1,2,4]Triazolo[4,3-a]pyridines.

An operationally efficient CDI mediated tandem coupling and cyclization reaction to generate [1,2,4]triazolo[4,3-a]pyridines has been reported. The reaction conditions and scope were investigated, and the methodology was demonstrated in batch mode as well as in a continuous process.