Palladacycles Based on 8-Aminoquinoline Carboxamides of Cobalt and Iron Sandwich Compounds and a New Method to α-Alkylate Cp Rings of Metal Sandwich Carboxamides

Abstract

Reactions of {η 5 -C 5 H 4 [C(O)Cl]}Co(η 4 -C 4 Ph 4 ) and {η 5 -C 5 H 4 [C(O)Cl]}Fe(η 5 -Cp) with 8-aminoquinoline resulted in cobalt and iron sandwich derived carboxamides.The reaction of these carboxamides with Pd(OAc) 2 in acetonitrile resulted in αC−H activation of the Cp rings of the sandwich compounds and formation of novel palladacycles 3 and 4, having both N−H and one α-C−H hydrogen atom of the Cp ring displaced and palladium forming a square planar complex with acetonitrile as the fourth ligand. These air-stable palladacycles reacted with MeI and EtI in acetic acid, resulting in monoand 2,5-di-α-alkylated sandwich carboxamides, thereby providing a new method to realize Cp-multisubstituted sandwich compounds. Selectivity in α-substitution was observed in the presence of NaHCO 3 . The cobalt sandwich carboxamide 1, the new palladacycles 3 and 4, and the 2,5-dimethylated cobalt sandwich carboxamide 5 have also been structurally characterized using single-crystal X-ray structural studies.

Cobalt‐Catalyzed ortho‐Methylation of Ferrocenes Bearing ortho‐Directing Groups by Catalytic Directed C–H Bond Activation

“…Remarkably, in contrast to the reaction of 8, no dimethylation product was observed. [69] This behavior could be confirmed, as the 2,5-dimethylated compound 14 [69] was isolated as the main product in 28 % yield (Scheme 4). The 8-aminoquinolinylcarbonyl moiety is an efficient ODG and furthermore removable.…”

“…of the alkylating agent. [69] This behavior could be confirmed, as the 2,5-dimethylated compound 14 [69] was isolated as the main product in 28 % yield (Scheme 4). In addition, a trace amount of a yellow product was isolated by column chromatography, which presumably is the monomethylated product.…”

“…Addition of (-)-spartein did not improve the yield of the reaction. [69] Scheme 4. [66,67] 8-Aminoquinolinecarboxamide 13 [68] was recently applied in a Pd-catalyzed ortho-alkylation by C-H activation, showing a preference for undergoing a second C-H activation with formation of dialkylated products when using 4 equiv.…”

8‐Aminoquinoline‐Assisted Synthesis and Crystal Structure Studies of Ferrocenyl Aryl Sulfones

“…[6] Recently,t he directing group assisted CÀHb ond functionalization of ferrocene becamea na ttractive tool for the CÀCa nd C-hetero atom bond formation reactions. [7][8][9][10] Selective CÀH functionalization in ferrocenes has been accomplished using directingl igandsn amely methylene diamine, oxazoline, pyridine, quinolone, and thioketone by Youa nd co-workers. [8] However, most of the CÀHf unctionalization strategies rely on palladium or late row transition metal catalysis (Scheme 1).…”

“…[7] The same time Elias and Wu groups also developedt he 8-aminoquinoline directed arylation and alkylation under palladium catalysis. [9,10] The first-row transition metal catalyzed ferrocene CÀHb ond functionalization reactioni sh ighly desirable nowadays. [11] Recently,B utenschçn's group demonstrated the coupling between CÀHb ond of ferrocenea nd phenylu nder iron catalysis.…”