Palladium-Catalyzed Decarboxylative <i>ortho</i>-Amidation of Indole-3-carboxylic Acids with Isothiocyanates Using Carboxyl as a Deciduous Directing Group

Palladium-catalyzed <i>ortho</i>-amidation of indole-3-carboxylic acids with isothiocyanates by using the deciduous directing group nature of carboxyl functionality to afford indole-2-amides is demonstrated. Both C–H functionalization and decarboxylation took place in one pot, and hence, this carboxyl group served as a unique, deciduous (or traceless) directing group. This reaction offers a broad substrate scope as demonstrated for several other heterocyclic carboxylic acids like chromene-3-carboxylic acid, imidazo­[1,2-<i>a</i>]­pyridine-2-carboxylic acid, benzofuran-2-carboxylic acid, pyrrole-2-carboxylic acid, and thiophene-2-carboxylic acid. In the reaction using 2-naphthoic acid, of the two possible isomers, only one isomer of the amide was exclusively formed. The indole-2-amide product underwent palladium-catalyzed C–H functionalization to afford the diindole-fused 2-pyridones by combining two molecules of the indole moiety, with the elimination of an amide group from one of them, attached at the C3-position for the C–C/C–N bond formation. The structures of key products are confirmed by X-ray crystallography

Palladium-Catalyzed Decarboxylative <i>ortho</i>-Amidation of Indole-3-carboxylic Acids with Isothiocyanates Using Carboxyl as a Deciduous Directing Group

Palladium-catalyzed <i>ortho</i>-amidation of indole-3-carboxylic acids with isothiocyanates by using the deciduous directing group nature of carboxyl functionality to afford indole-2-amides is demonstrated. Both C–H functionalization and decarboxylation took place in one pot, and hence, this carboxyl group served as a unique, deciduous (or traceless) directing group. This reaction offers a broad substrate scope as demonstrated for several other heterocyclic carboxylic acids like chromene-3-carboxylic acid, imidazo­[1,2-<i>a</i>]­pyridine-2-carboxylic acid, benzofuran-2-carboxylic acid, pyrrole-2-carboxylic acid, and thiophene-2-carboxylic acid. In the reaction using 2-naphthoic acid, of the two possible isomers, only one isomer of the amide was exclusively formed. The indole-2-amide product underwent palladium-catalyzed C–H functionalization to afford the diindole-fused 2-pyridones by combining two molecules of the indole moiety, with the elimination of an amide group from one of them, attached at the C3-position for the C–C/C–N bond formation. The structures of key products are confirmed by X-ray crystallography

Ruthenium-Catalyzed Oxidative Annulation and Hydroarylation of Chromene-3-carboxamides with Alkynes via Double C–H Functionalization

Ruthenium-catalyzed oxidative annulation of 2<i>H</i>-chromene-3-carboxamides with alkynes has been achieved by using the directing group nature of amide in the presence of Cu­(OAc)₂·H₂O as an oxidant and AgNTf₂ as an additive. This reaction offers a broad substrate scope, and both symmetrical and unsymmetrical alkynes can be harnessed. High regioselectivity was achieved in the case of unsymmetrical alkynes. In addition, we have also accomplished double C–H activation by employing an excess of alkyne, where both annulation and hydroarylation took place regio- and stereoselectively in one pot, with the catalyst playing a dual role. While the first C–H functionalization could involve Ru–N covalent bond, the second C–H functionalization most likely involves Ru–O coordinate bond. The structures of key products are confirmed by X-ray crystallography