1. Ruthenium-Catalyzed Direct C-H Amidation of Arenes Including Weakly Coordinating Aromatic Ketones
The ruthenium-catalyzed direct $sp^2$ C-H amidation of arenes with using sulfonyl azides as the amino source is presented. Under mild conditions without external oxidants, molecular nitrogen is found to be a sole by-product generated from azide. Research on amidation of arenes with various directing groups was conducted to show that wide range of arene substrates bearing pyridyl and amide directing groups were readily amidated. In addition, weakly coordinating ketone directing groups were also applicable to our amidation reactions to provide ortho-amino aryl ketones. This ortho-amino aryl ketones can be useful synthetic unit for the synthesis of biologically active heterocycles.
2. Complete Switch of Selectivity in the C-H Alkenylation and Hydroarylation Catalyzed by Iridium : The Role of Directing Groups
$Cp^*$ Ir(III)-catalyzed C-H alkenylation and hydroarylation were studied to find the complete switch of the product-selectivity on the type of directing groups under the same reaction conditions. In our study, directing groups of N-chelator afforded hydroarylated products while directing groups containing carbonyl groups of O-chelator afforded alkenylated products. On the basis of mechanistic studies, we proposed that the origin of product distribution can be correlated to the efficiency of attaining syn-coplanarity of olefin inserted 7-membered iridacycles during the β-H elimination. Computational studies support that the degree of flexibility of this 7-membered key intermediate determines the efficiency of the β-H elimination, and this flexibility is closely related to bond characteristics between Ir center and heteroatom in directing group and the initial iridacycle geometry with each type of directing group.