On-Water Cp*Ir(III)-Catalyzed C-H Functionalization for the Synthesis of Chromones through Annulation of Salicylaldehydes with Diazo-Ketones.

A high-valent Ir(III)-catalyzed C-H bond functionalization is carried out for the first time on water for the synthesis of a biologically relevant chromone moiety. The C-H activation and annulation of salicylaldehydes with diazo-compounds provided the desired chromones. The synthesis of C3-substitution-free chromones has also been demonstrated by a one-pot decarboxylation by employing tert-butyl diazoester. C3 and C5 C-H activations of the product chromone are also carried out under different conditions for further diversification.

Harnessing Stereospecific Z-Enamides through Silver-Free Cp*Rh(III) Catalysis by Using Isoxazoles as Masked Electrophiles.

The stereospecific synthesis of Z-enamides is described in this paper. For the first time, isoxazoles have been employed as electrophiles in C-H functionalization to afford thermodynamically less stable Z-enamides utilizing salicylaldehydes in an atom- and step-economic fashion. The stereochemistry of enamides might originate from the relative disposition of atoms present in isoxazole and the intramolecular hydrogen bonding. The reaction showed excellent scope as several structurally and electronically diverse salicylaldehydes and isoxazoles reacted efficiently.

Cp*CoIII-Catalyzed syn-Selective C-H Hydroarylation of Alkynes Using Benzamides: An Approach Toward Highly Conjugated Organic Frameworks.

Hydroarylation of internal alkynes by cost-effective CoIII-catalysis, directed by N-tert-butyl amides, is achieved to avail mono- or dihydroarylated amide products selectively in an atom and step economic way. Several important functional groups were tolerated under the reaction conditions, and syn-hydroarylation products were exclusively isolated. Notably, a 4-fold C-H hydroarylation provided a highly conjugated organic framework in one step. Kinetic study with extensive deuterium labeling experiments were performed to support the proposed mechanism.

Cp*Rh(III)-Catalyzed Low Temperature C-H Allylation of N-Aryl-trichloro Acetimidamide.

The readily synthesized trichloro acetimidamide was found to be an excellent directing group for the directed C-H-allylation reactions. Depending on the allylating agent used, selectively either mono- or diallylated products were readily synthesized. Moreover, the trichloro acetimidamide directing group was found to be highly efficient even at lower temperature for the C-H-allylation reaction. Due to mildness of the reaction conditions, double bond isomerization or cyclization to indole side product was not observed.