Ruthenium(II)-Catalyzed Oxidative Double C–H Activation and Annulation Reaction: Synthesis of Indolo[2,1-a]isoquinolines

Abstract

The first metal-catalyzed double aryl C­(sp2)–H bond activation of antipyrine and alkyne annulation reaction is reported. This Ru­(II)-catalyzed reaction was accomplished in the presence of 20 mol % phosphine ligand tricyclohexylphosphine tetrafluoroborate to afford indolo­[2,1-a]­isoquinolines that are very important compounds because of their bioactivity and interesting optical properties.

Metal‐Free Direct C–H Thiolation and Thiocyanation of Pyrazolones

“…Other solvents and oxidants including Na 2 S 2 O 8 , (NH 4 ) 2 S 2 O 8 or peroxide (i.e. H 2 O 2 , TBHP, DTBP) were less effective for this transformation (entries [7][8][9][10][11][12]. [15] Carrying out the reaction at room temperature resulted in much lower conversion (entry 13).…”

Recent advances in the synthesis of indoles via C–H activation aided by N–N and N–S cleavage in the directing group

“…The same group disclosed a cationic Ru(II)‐catalysed unprecedented route to generate indolo[2,1‐ a ]isoquinolines ( 127 ) via dual C–H activation‐alkyne annulation involving antipyrine ( 125 ) (Scheme 38). [ 47 ] 2,3‐Diphenylindole is formed in the midst of the reaction which undergoes a second annulation to generate the product. The N–N bond similar to the earlier protocol is used in the oxidation of Ru(II) to Ru(IV) in an intermediate step of the catalytic cycle.…”

Ruthenium-Catalyzed C–H Activations for the Synthesis of Indole Derivatives

“…In 2019, the first ruthenium-catalyzed double aryl C(sp 2 )-H bond activation of antipyrine and alkyne annulation reaction was reported by Sanjib Gogoi [17] and his co-workers. Two equivalents of anilines participated in the reaction to afford indolo [2,1-a]isoquinolines (Scheme 5).…”