Palladium‐Catalyzed CH Functionalization of Ferrocenecarboxylic Acid by using 8‐Aminoquinoline as a Removable Directing Group

Abstract

Am ild and efficientp alladium-catalyzed synthetic method for the C À Hf unctionalization of N-(quinolin-8-yl)ferrocenecarboxamide has been developed. Va rious aryl iodides containingI ,N O 2 ,C N, COMe,C O 2 Et, and NH functionalities and also alkyl iodidesu nderwent the Pd-catalyzed intermolecular carbon-carbon bond forming reactionw ith ferrocenecarboxamide successfully which led to ad iverse array of bis(aryl/alkyl)ferrocenecarboxamidesi n3 4-92% yields.C ross-coupling of the ferrocenylC À H bond with aryl iodidesc an also be achieved utilizing an economical Ni catalyst. Additionally,s elective monoalkylation of ferrocenecarboxamide was studied using sodium bicarbonatea sb ase and dibenzylphosphoric acid as additive under Pd-catalyzed reaction conditions.S ubsequently,r emoval of the directing group,8 -aminoquinoline,f rom bis(aryl)ferrocenecarboxamides led to bis(aryl)ferrocenesb earing versatilem ethyl ester andc arboxaldehyde functional groups.Scheme 2. Substrate scope with regard to aryl/heteroaryl iodides.U nlesso therwises tated, isolated yields using 10 mol% of Pd(OAc) 2 in toluene are given.

A comprehensive overview of directing groups applied in metal-catalysed C–H functionalisation chemistry

“…The arylation reaction was extended in 2016 to N -(quinolin-8-yl)ferrocenecarboxamide by Kumar. 393 This Pd-based catalytic system gave access to di-arylated and mono- or di-alkylated ferrocenecarboxamides ( Scheme 65E ) and demonstrated a good FG tolerance on the aryl iodide partners (alkyl, CF 3 , OMe, NMe 2 , Cl, I, acyl, NO 2 ). The efficiency of Ni(OTf) 2 was also evaluated, but lower yields were obtained.…”

“…Methylation and ethylation of two palladacycles derived from ferrocene and a Co sandwich compound were realised ( Scheme 67M ) with moderate yields (31–66%). 407 The Pd-catalysed system developed by Kumar for (hetero)arylation of ferrocenecarboxamides 393 was equally efficient for the mono- and di-alkylation with alkyl iodides ( Scheme 67N ). The key to control the selectivity was the nature of the base: NaHCO 3 promoted mono-alkylation while Cs 2 CO 3 yielded di-alkylated products.…”

Rhodium(III)‐Catalyzed Direct C−H Alkylation of Ferrocenes with Diazo Compounds under Weakly Coordinating Approach

“…Shibata and co‐workers reported the first ever Ir‐catalyzed directed alkylation of ferrocenes with alkenes using pyridine as a directing group . Kumar and co‐workers established a mild and efficient Pd‐catalyzed synthetic method for the C−H alkylation of ferrocenes using alkyl iodides . Recently, Moh.…”

“…There are various methods for CÀ H bond functionalization of ferrocenes reported till date. [5][6][7][8] However, the reports for transition metal-catalyzed CÀ H alkylation of ferrocenes by using alkenes, [9] alkyl iodides, [10] toluene derivatives [11] and Grignard reagents [12] as alkylation sources are still limited (Scheme 1a). Shiba-ta and co-workers reported the first ever Ir-catalyzed directed alkylation of ferrocenes with alkenes using pyridine as a directing group.…”

“…[9a] Kumar and co-workers established a mild and efficient Pd-catalyzed synthetic method for the CÀ H alkylation of ferrocenes using alkyl iodides. [10] Recently, Moh. Sattar and Sangit Kumar provided an elegant catalytic method to obtain functionalized ferrocenes, achieving the coupling of unreactive C(sp 2 )À H and C(sp 3 )À H bonds with toluene derivatives.…”