Ru(II)-Catalyzed β-Carboline Directed C–H Arylation and Isolation of Its Cycloruthenated Intermediates

Abstract

A Ru(II)-catalyzed C-H arylation approach has been developed utilizing β-carboline alkaloids as the directing group. Selective formations of diarylated products from moderate to excellent yields were accomplished. Broad substrate scope with excellent functional group tolerance for C1-phenyl/thienyl/PAHs-β-carbolines was demonstrated. X-ray crystal structure of cycloruthenated complex 2cr and no arylation reaction with model substrate 13 strongly suggests that N2 is the directing group than N9 in C1-aryl-β-carbolines. Catalytic properties and stability of the cycloruthenated complexes have been explored. Library of biologically relevant new β-carboline derivatives and isolation of its cycloruthenated intermediates are the highlights of this work.

Biological and catalytic evaluation of Ru(II)‐p‐cymene complexes of Schiff base ligands: Impact of ligand appended moiety on photo‐induced DNA and protein cleavage, cytotoxicity and C‐H activation

“…Literature review shows that β‐carboline directed C–H arylation was achieved using a commercially available catalyst, dichloro( p ‐cymene) ruthenium(II) dimer complex, wherein various aryl rings were introduced . Hence, the present Ru(II)‐ p ‐cymene complexes, which are structurally different from the commercially available Ru(II) catalyst, were employed for the β‐carboline directed C–H arylation as shown in scheme .…”

“…In the regard of catalytic applications, [Ru( η 6 ‐ p‐ cymene)(κ 2 ‐ N , N ‐dmbpy)Cl] + , where dmbpy is 4,4′‐dimethyl‐2,2′‐bipyridine is reported for its catalytic transfer hydrogenation of different ketones to the corresponding alcohols . Dichloro( p ‐cymene) ruthenium(II) dimer complex is employed as a catalyst for β‐carboline directed C–H arylation wherein various aryl ring was introduced through C‐H activation …”

“…[20] Dichloro(p-cymene) ruthenium(II) dimer complex is employed as a catalyst for β-carboline directed C-H arylation wherein various aryl ring was introduced through C-H activation. [21] Schiff bases are well-known pharmacophore for broad spectrum of biological activities by interfering with normal cellular processes, which is effected by formation of intramolecular hydrogen bonding between imine group and active center of cell constituents. [22] The incorporation of these bioactive Schiff base ligands with Ru-pcymene moiety would enhance the synergetic effect, which could be used to develop effective drugs for cancer therapy.…”

β-Carboline-directed decarboxylative acylation of ortho-C(sp2)–H of the aryl ring of aryl(β-carbolin-1-yl)methanones with α-ketoacids under palladium catalysis

“…β-Carboline, a privileged scaffold, is core unit of several natural alkaloids and bioactive compounds endowed with diverse pharmacological properties. 18 The first example of β-carbolinedirected ruthenium-catalyzed arylation was reported by Gandhi et al 19 Subsequently we reported Pd(OAc) 2 -catalysed regioselective alkoxylation (C-O bond formation) of aryl (βcarbolin-1-yl) methanones employing β-carboline directed ortho-C(sp2)-H activation of an aryl ring under oxidative conditions. 20 Continuing with our efforts to study the scope of β-carboline directed C(sp2)-H activation for installing various functional groups, we now disclose a Pd-catalysed β-carboline directed decarboxylative acylation using α-oxocarboxylic acid as the acyl ion source to form (2-aroylaryl) (β-carbolin-2yl)methanones.…”

Pd(OAc)2-catalysed regioselective alkoxylation of aryl (β-carbolin-1-yl)methanones via β-carboline directed ortho-C(sp2)–H activation of an aryl ring

“…In principle, the alkoxy unit could be readily installed via palladium-catalysed ligand assisted activation of orthoaromatic C(sp2)-H in aryl (9H-pyrido[3,4-b]indol-1yl)methanone which are readily accessible using literature procedure. 25 They demonstrated that the pyridine nitrogen of the β-carboline is responsible for the chelation with Ru leading to ortho-Caryl-H functionalization. Only very recently Gandhi et al reported Ru(II)-catalyzed C−H arylaƟon for arylating (hetero)aryl and polyaromatic hydrocarbons attached to the β-carboline scaffold utilizing β-carboline as the directing group.…”