Catalyst and solvent switched divergent C-H functionalization: oxidative annulation of N-aryl substituted quinazolin-4-amine with alkynes.

The development of site-selective C-H functionalizations/annulations is one of the most challenging practices in synthetic organic chemistry particularly for substrates bearing several similarly reactive C-H bonds. Herein, we describe catalyst and solvent controlled ortho/peri site-selective oxidative annulation of C-H bonds of N-aryl substituted quinazolin-4-amines with internal alkynes. The ortho C-H selective annulation was observed using Pd-catalyst in DMF to give indole-quinazoline derivatives, while, Ru-catalyst in PEG-400 favoured the peri C-H bond annulation exclusively to furnish pyrido-quinazoline derivatives.

Bimetallic Cu/Pd-catalyzed three-component azide-alkyne cycloaddition/isocyanide insertion: synthesis of fully decorated tricyclic triazoles.

The construction of fully decorated 1,2,3-triazole-fused 5-, 6- and 7-membered rings has been disclosed via a bimetallic relay-catalyzed cascade process combining azide-alkyne cycloaddition, C(sp2)-H functionalization of intermediary 1,2,3-triazoles and isocyanide insertion. The salient features of this methodology include simple starting materials, reduced synthetic steps, good substrate scope and high efficiency.

Palladium-Catalyzed [2 + 2 + 2] Annulation via Transformations of Multiple C-H Bonds: One-Pot Synthesis of Diverse Indolo[3,2- a]carbazoles.

A Pd-catalyzed novel cascade reaction has been developed for the synthesis of indolo[3,2 a]carbazoles involving multiple C-H transformation-annulations between the indoles and alkynes. The method involves molecular oxygen as the sole oxidant and is an effective and step-economic process.