Palladium nanoparticles for the synthesis of phenanthridinones and benzo[]chromenes C-H activation reaction.

In the present work, derivatives of phenanthridine-6(5)-ones and benzo[]chromenes were efficiently prepared through an intramolecular C-H bond functionalization reaction catalyzed by photochemically synthesized Pd-PVP nanoparticles. The heterocycles were obtained intramolecular arylation of the corresponding -methyl--aryl-2-halobenzamide or aryl-(2-halo)benzyl ethers using KCO as base in a mixture of HO : DMA as solvent without additives or ligands. High yields of the heterocyclic compounds were achieved (up to 95%) using a moderately low catalyst loading (1-5 mol%) under an air atmosphere at 100 °C.

Visible light mediated synthesis of 6-benzo[]chromenes: transition-metal-free intramolecular direct C-H arylation.

A synthetic approach towards the 6-benzo[]chromene ring under visible light and transition-metal-free conditions has been developed. Benzochromenes are synthesized from the corresponding (2-halobenzyl) phenyl ethers or (2-halophenyl) benzyl ethers using KOBu in dimethyl sulfoxide (DMSO) at room temperature (rt) and blue light-emitting diodes (LEDs) as the light source. This methodology replaces the use of ligands or additives, high temperatures and toxic solvents.

Transition-Metal-Free and Visible-Light-Mediated Desulfonylation and Dehalogenation Reactions: Hantzsch Ester Anion as Electron and Hydrogen Atom Donor.

Novel approaches for N- and O-desulfonylation under room temperature (rt) and transition-metal-free conditions have been developed. The first methodology involves the transformation of a variety of -sulfonyl heterocycles and phenyl benzenesulfonates to the corresponding desulfonylated products in good to excellent yields using only KOBu in dimethyl sulfoxide (DMSO) at rt. Alternately, a visible light method has been used for deprotection of -methyl--arylsulfonamides with Hantzsch ester (HE) anion serving as the visible-light-absorbing reagent and electron and hydrogen atom donor to promote the desulfonylation reaction.