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.

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.

FeCl catalysed 7-membered ring formation in a single pot: a new route to indole-fused oxepines/azepines and their cytotoxic activity.

Various oxepine and azepine fused N-heterocyclic derivatives were synthesized using a new and one-pot reaction of 2,3-dichloro quinoxaline/pyrazine with 2-(1H-indol-2-yl)phenol/aniline in the presence of 25 mol% FeCl. The reaction proceeded via C-C bond followed by C-X (X = O or N) bond formation to construct the central 7-membered ring, affording the desired products in good yields. The structure assignment was confirmed by the single crystal X-ray analysis of a synthesized oxepine fused N-heterocycle derivative.