Jayachandran Jayakumar

Ru(II)-Catalyzed C–H Bond Activation for the Synthesis of Substituted Isoquinolinium Salts from Benzaldehydes, Amines, and Alkynes

An efficient method for the synthesis of substituted isoquinolinium salts from benzaldehydes, amines, and alkynes via ruthenium-catalyzed C-H bond activation and annulation in one pot is described.

One-Pot Synthesis of Highly Substituted Polyheteroaromatic Compounds by Rhodium(III)-Catalyzed Multiple CH Activation and Annulation**

A new method for the synthesis of highly substituted naphthyridine-based polyheteroaromatic compounds in high yields proceeds through rhodium(III)-catalyzed multiple C-H bond cleavage and C-C and C-N bond formation in a one-pot process. Such highly substituted polyheteroaromatic compounds have attracted much attention because of their unique π-conjugation, which make them suitable materials for organic semiconductors and luminescent materials. Furthermore, a possible mechanism, which involves multiple chelation-assisted ortho C-H activation, alkyne insertion, and reductive elimination, is proposed for this transformation.

Rhodium(III)-Catalyzed Vinylic C–H Activation: A Direct Route toward Pyridinium Salts

A synthetic method for highly substituted pyridinium salts from the multicomponent reaction of vinyl ketones/aldehydes, amines, and alkynes using a rhodium catalyst is demonstrated. The catalytic reaction proceeds via an in situ generated imine-assisted Rh(III)-catalyzed vinylic C-H activation.

One pot synthesis of bioactive benzopyranones through palladium-catalyzed C–H activation and CO insertion into 2-arylphenols

Palladium-catalyzed oxidative carbonylation of 2-arylphenols through C-H bond activation and C-C and C-O bond formation under acid-base free and mild conditions has been developed. The reaction tolerates a variety of substrates and provides biologically important benzopyranone derivatives in up to 87% isolated yield.

Direct Synthesis of Protoberberine Alkaloids by Rh-Catalyzed C-H Bond Activation as the Key Step.

A one-pot reaction of substituted benzaldehydes with alkyne-amines by a Rh-catalyzed C-H activation and annulation to afford various natural and unnatural protoberberine alkaloids is reported. This reaction provides a convenient route for the generation of a compound library of protoberberine salts, which recently have attracted great attention because of their diverse biological activities. In addition, pyridinium salt derivatives can also be formed in good yields from α,β-unsaturated aldehydes and amino-alkynes. This reaction proceeds with excellent regioselectivity and good functional group compatibility under mild reaction conditions by using O2 as the oxidant.

Impact of the Valence Charge of Transition Metals on the Cobalt- and Rhodium-Catalyzed Synthesis of Indenamines, Indenols, and Isoquinolinium Salts: A Catalytic Cycle Involving MIII/MV [M = Co, Rh] for [4+2] Annulation

Reaction mechanisms for the synthesis of indenamines, indenols, and isoquinolinium salts through cobalt- and rhodium-catalysis were investigated using density functional theory calculations. We found that the valence charge of transition metals dramatically influences the reaction pathways. Catalytic reactions involving lower-oxidation-state transition metals (MI/MIII, M = Co and Rh) generally favor a [3 + 2] cyclization pathway, whereas those involving higher oxidation states (MIII/MV) proceed through a [4 + 2] cyclization pathway. A catalytic cycle with novel MIII/MV as a crucial species was successfully revealed for isoquinolinium salts synthesis, in which highly valent MV was encountered not only in the [RhCp*]-catalysis but also in the [CoCp*]-catalysis.