Pd(II)-catalyzed enantioselective C(sp
3
)−H cross-coupling of free carboxylic acids with organoborons has been realized using either mono-protected amino acid (MPAA) ligands or mono-protected ...aminoethyl amine (MPAAM) ligands. A diverse range of aryl- and vinyl-boron reagents can be used as coupling partners to provide chiral carboxylic acids. This reaction provides an alternative approach to the enantioselective synthesis of cyclopropanecarboxylic acids and cyclobutanecarboxylic acids containing α-chiral tertiary and quaternary stereocenters. The utility of this reaction was further demonstrated by converting the carboxylic acid into cyclopropyl amine without loss of optical activity.
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A straightforward assisted tandem palladium(II)‐ and palladium(0)‐catalyzed direct C‐3 and N‐4 arylation of quinoxalin‐2(1 H)‐ones with boronic acids and aryl halides in water as safe and cheap ...solvent is reported. This environmentally friendly catalytic protocol is compatible with a wide range of functional groups and allows construction of various biologically important quinoxalin‐2(1 H)‐one backbones.
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A new approach for the fully chemoselective α‐arylation of amides is presented. By means of electrophilic amide activation, aryl groups can be regioselectively introduced α‐ to amides, even in the ...presence of esters and alkyl ketones. Mechanistic studies reveal key reaction intermediates and emphasize a remarkably subtle base effect in this transformation.
Arylating me softly: A new approach for the fully chemoselective α‐arylation of amides has been developed. When electrophilic amide activation is employed, aryl groups can be regioselectively introduced in the position α to the amide, and that even in the presence of esters or alkyl ketones. Mechanistic studies emphasize a remarkably subtle base effect in this transformation.
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•The synthesis of 2-halogenated 4-(isobutylamino)benzoic acids was reported.•Cyclic triamides of the 4-aminobenzoic acids were synthesized by condensation.•Pd-mediated CC bond ...formation of the cyclic triamide gave a coronene analogue.
A coronene analogue containing amide linkage was synthesized from a halogenated cyclic triamide by palladium-mediated intramolecular CC bond formation. The cyclic triamide was formed from the condensation of 2-chloro-4-(isobutylamino)benzoic acid in the presence of dichlorotriphenylphosphorane in 1,1,2,2-tetrachloroethane. By contrast, the condensation of 2-bromo counterpart required silicon tetrachloride in pyridine. The intramolecular CC bond formation, which yielded the target coronene analogue, occurred during the reaction of bromo-substituted cyclic triamide with palladium(II) acetate, triphenylphosphine, and potassium carbonate in N,N-dimethylformamide.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Two new palladium‐catalyzed reactions of aromatic sulfur compounds enabled the conversion of dibenzothiophenes into triphenylenes in four steps. This transformation of one aromatic framework into ...another consists of 1) 4‐chlorobutylation of the dibenzothiophene to form the corresponding sulfonium salt, 2) palladium‐catalyzed arylative ring opening of the sulfonium salt with a sodium tetraarylborate, 3) an intramolecular SN2 reaction to form a teraryl sulfonium salt, and 4) palladium‐catalyzed intramolecular CS/CH coupling through electrophilic palladation. Symmetrical as well as unsymmetrical triphenylenes of interest were synthesized in a tailor‐made fashion in satisfactory overall yields.
A change of heart: The invention of two palladium‐catalyzed arylation reactions of organosulfur compounds enabled the transformation of dibenzothiophenes into triphenylenes and thus a fundamental change in the core aromatic structure (see scheme). Both symmetrical and unsymmetrical triphenylenes were synthesized in a tailor‐made fashion in satisfactory overall yield.
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The front cover picture is a metaphor of mechanochemistry. A pair of robotic arms is playing dominoes with the mechanism of Ni‐catalyzed domino‐cyclisation‐arylation of o‐hydroxyarylenaminones, ...elucidated by the experimental and computational investigations in our group. Meanwhile, another set of mechanical contraptions working at 30 Hz is about to ground the domino tiles as they fall to obtain isoflavones under mechanochemical conditions. This is the first example where the mechanic energy is used in the synthesis of isoflavones following a domino cyclisation. Details can be found in the Research Article by Iaroshenko and co‐workers (S. Mkrtchyan, M. Jakubczyk, S. Lanka, M. Yar, T. Mahmood, K. Ayub, M. Sillanpää, C. M. Thomas, V. O. Iaroshenko, Adv. Synth. Catal. 2022, 364, 3512–3521; DOI: 10.1002/adsc.202200645).
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The utilization of chiral transient directing groups (TDGs) has recently emerged as a promising approach for developing Pd(II)-catalyzed enantioselective C(
sp
3
)−H activation reactions. However, ...this strategy is particularly challenging because the stereogenic center present on the TDG is often far from the C–H bond. Additionally, the TDG covalently attached to the substrate and the free TDG are both capable of coordinating to Pd(II) centers, which can result in a mixture of reactive complexes that may lead to opposite asymmetric induction. To date, the single example of TDG-enabled enantioselective C(
sp
3
)−H activation is limited to the functionalization of benzylic C–H bonds. Herein we report the first example of a Pd(II)-catalyzed enantioselective β-C(
sp
3
)−H arylation reaction of aliphatic ketones using a chiral transient directing group. A chiral trisubstituted cyclobutane is efficiently synthesized from a mono-substituted cyclobutane via sequential C–H arylation reactions, demonstrating the ability of this method to access structurally complex products from simple starting materials. The use of an electron-deficient pyridone ligand is also crucial for the observed high enantioselectivity. Interestingly, employing different silver salts can reverse the enantioselectivity in the C(
sp
3
)−H arylation reaction. These key mechanistic findings will provide insight for future development of Pd(II)-catalyzed enantioselective C(
sp
3
)−H activation reactions with chiral TDGs.
A Pd(II)-catalyzed enantioselective C(
sp
3
)−H arylation of ketones using an α-amino acid as a chiral transient directing group is reported. The 3-nitro-5-trifluoromethyl-2-pyridone was identified as an effective ligand, serving as an acetate surrogate to accelerate C–H bond cleavage in the transient directing group strategy. The combination of an electron-deficient 2-pyridone ligand with different silver salts offers an effective method for controlling the rate-limiting steps which enables the high enantioselectivity and yield of this reaction.
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A new class of bidentate ligand, 1‐(pyridine‐2‐yl)‐1H‐benzod1,2,3triazole has been designed and employed for the palladium‐catalyzed CC (Suzuki, Heck, Fujiwara–Moritani, and Sonogashira), CN and ...CS coupling reactions. The ligand was found to be inexpensive, thermally stable, easy to synthesize from easily accessible starting materials on a multigram scale, show simplicity in use, and robustness in application, making this ligand effective for different coupling reactions. Suitably, the donor ability of the NN bond of the benzotriazole ring and lone pair of electrons on the N of the pyridine ring enhance the bidentate ability of the ligand.
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Arylation of carbonyls, one of the most common approaches toward alcohols, has received tremendous attention, as alcohols are important feedstocks and building blocks in organic synthesis. Despite ...great progress, there is still a great gap to develop an ideal arylation method featuring mild conditions, good functional group tolerance, and readily available starting materials. We now show that electrochemical arylation can fill the gap. By taking advantage of synthetic electrochemistry, commercially available aldehydes (ketones) and benzylic alcohols can be readily arylated to provide a general and scalable access to structurally diverse alcohols (97 examples, >10 gram‐scale). More importantly, convergent paired electrolysis, the ideal but challenging electrochemical technology, was employed to transform low‐value alcohols into more useful alcohols. Detailed mechanism study suggests that two plausible pathways are involved in the redox neutral α‐arylation of benzylic alcohols.
Electrochemical approaches to the direct arylation of carbonyls and alcohols through less‐explored cathodic reduction and convergent paired electrolysis are presented. This protocol features: excellent functional group (including ester, amide, amine, thioether, borate) tolerance, mild conditions (metal catalyst‐ and external reductant‐free), good scalability (>10 gram‐scale), and site‐selectivity.
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•This article reports a mild system catalyzed by ligand free palladium, which promoted the ortho-aromatization of benzoic acid under mild conditions for 36 hours and achieved ...excellent results.•Under this reaction condition, not only is there no decarboxylation byproduct, but also the ortho substituted benzoic acid is obtained with good yield.•The catalytic system has simple operation and mild conditions.
It is particularly significant to develop mild and efficient methods to construct 2-aryl-substituted benzoic acids framwork due to their wide existence in many important natural organic compounds. Here, we report a concise and mild method to synthesize ortho-arylation of benzoic acids. In this mild catalytic system, decarboxylation byproducts were not observed. Meanwhile, the high yields could be obtained in the absence of ligands.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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