Amides as Weak Coordinating Groups in Proximal C–H Bond Activation

Abstract

Site selectivity is an inherent challenge in C–H functionalization reactions. The most intensively sought‐after approaches have involved the employment of Lewis‐basic coordinating groups to direct a metal to a proximal site, in the process generating a metallacycle capable of further organometallic reactivity. In the recent years considerable effort has been directed towards the development of new transformations involving transition‐metal‐mediated C–H functionalization directed by weakly coordinating groups. This microreview focuses on the role and utility of amides and anilides in directed, proximal C–H bond functionalization reactions.

Esterification of Tertiary Amides: Remarkable Additive Effects of Potassium Alkoxides for Generating Hetero Manganese–Potassium Dinuclear Active Species

“…Amides are ubiquitous and abundant, and are often found in natural compounds such as proteins as well as in synthetic organic compounds such as poly(amides) and pharmaceuticals. [1][2][3][4][5] Cleavage of stable amide bonds under mild conditions has attracted the ongoing attention of organic chemists, [6] and rational strategies, such as diminishing the resonance structure of the CÀN bond by complexing N,N-(2-pyridylmethyl)amides with Cu II sources [7,8] and the construction of a twisted structure around the nitrogen atom have been investigated. [9,10] Cleavage of the common amide bond without these complex strat-egies requires harsh reaction conditions using stoichiometric amounts of strong acids or bases at high temperatures, and produces the corresponding acids via hydrolysis and esters via alcoholysis.…”

“…[25,26] In this context, we focused our attention on developing effective catalysts for the esterification of simple tertiary N,N-dialkyl amides. We previously found that an alkoxide-bridged manganese dinuclear complex, [(acac)(Me 2 N-Phen)Mn(m-OnBu)] 2 (2 a) (Me 2 N-Phen = 4,7-bis(dimethylamino)-1,10-phenanthroline), derived by treating an alkoxide-bridged manganese tetranuclear cubic complex [Mn(acac)(OEt)(EtOH)] 4 (1) with Me 2 N-Phen in nBuOH, was an excellent catalyst for the esterification of various N,N-dialkyl arylamides via a cooperative mechanism in which one manganese center functioned as a Lewis acid for coordinating to the amide carbonyl moiety and the second manganese center activated an alcohol to provide more nucleophilic alkoxide species (Scheme 1 d). [28] Herein, we report another manganese catalyst system, Mn(acac) 2 (Me 2 N-Phen) (3), and the remarkable additive effects of potassium alkoxides that improved the catalytic activity of 3 for the esterification of not only N,N-dialkyl benzamides but also N,N-dialkyl aliphatic amides.…”

Recent Advances in C–H Bond Functionalization with Ruthenium-Based Catalysts

“…Generally, the cationic ruthenium species, [RuCl 2 (p-cymene)] 2 /AgSbF 6 or [RuCl 2 (p-cymene)] 2 /KPF 6 have been used for C-H bond functionalization, directed by a weakly coordinatedoxygen and π-bond donor group. The C-H bond functionalization of weakly coordinated directing groups has been extensively studied by the research groups of Jeganmohan [21,22], Ackermann [23] and others [24]. Recently, the benefits of the carboxylic acid ligand in C-H bond functionalization reaction have been explored.…”

Mechanistic DFT Study on Rhodium(III)‐Catalyzed Double C−H Activation for Oxidative Annulations of 2‐Substituted Imidazoles and Alkynes

“…Transition-metal-catalyzed CÀHb ond activation has received great attentiono ver the past decades. [1][2][3][4][5] Due to the inherent problemsa ssociated with the reactivity and selectivity of CÀH bonds, the traditional strategy of directing-group (DG) assistance has been widely used for efficient CÀHb ond functionalization. [6] In this context, for transition-metal-catalyzed proximal C(sp 2 )ÀHb ond activation, the heteroatom-containing DG is generally required in precursor A,a nd s complex B should be formed prior to the CÀHb ond activation to form metallacyclic intermediate C (Scheme 1a).…”

“…[6] In this context, for transition-metal-catalyzed proximal C(sp 2 )ÀHb ond activation, the heteroatom-containing DG is generally required in precursor A,a nd s complex B should be formed prior to the CÀHb ond activation to form metallacyclic intermediate C (Scheme 1a). Numerous novel transformations have been developed with this strategy over recent decades, [1][2][3][4][5][6][7] and recently the activation of remote meta-CÀH bonds has been realized by elegant design of the DG in combination with as uitable metal catalyst. [8,9] In studies on the possible new roles of DGs, CÀHa ctivations with tracelessD Gs [10,11] ando xidizing DGs have been disclosed in recent years.…”