Multicomponent reaction comprising one-pot installation of bidentate directing group and Pd(II)-catalyzed direct β-arylation of C(sp3) H bond of aliphatic and alicyclic carboxamides (original) (raw)
The Journal of Organic Chemistry, 2016
In this paper, we report our successful attempt on the Pd(II)-catalyzed, bidentate directing group-aided, chemoselective acetoxylation/substitution of remote ε-C(sp 2)-H bonds using heteroaryl-aryl-based biaryl systems. While the bidentate directing group (BDG)-aided, C-H activation and functionalization/acetoxylation of the β-, γand δ-C-H bonds of appropriate carboxamide systems were well documented, there exist only rare reports dealing on the C-H activation and functionalization of remote ε-C-H bonds of appropriate substrates. Especially, the BDG-aided chemoselective acetoxylation of remote ε-C(sp 2)-H bond over cyclization has not been explored well. Accordingly, in this work the treatment of various picolinamides / oxalylamides / pyrazine-2-carboxamides 4/7/9/11, which were derived from the corresponding C-3 arylated furfurylamines or thiophen-2-ylmethanamines with PhI(OAc) 2 in the presence of the Pd(OAc) 2 catalyst successfully afforded the corresponding ε-C-H acetoxylated products. The
Ligand‐Enabled PdII‐Catalyzed Iterative γ‐C(sp3)−H Arylation of Free Aliphatic Acid
Angewandte Chemie International Edition, 2019
C−H functionalization of aliphatic carboxylic acids without attaching exogenous auxiliary has been so far limited at the proximal β‐position. In this work, we demonstrate a ligand enabled palladium catalyzed first regioselective distal γ‐C(sp3)−H functionalization of aliphatic carboxylic acids without incorporating an exogenous directing group. Aryl iodides containing versatile functional groups including complex organic molecules are well tolerated with good to excellent yields during the γ‐C(sp3)−H arylation reaction. Interestingly, weak coordination of carboxylate group can be further extended for sequential hetero di‐arylation. Application of the protocol has been showcased by synthesizing substituted α‐tetralone. Mechanistic investigations have been carried out to shed light on the reaction pathway.
Chemistry - A European Journal, 2012
Optimization of reaction conditions and substrate structures: To confirm that the expected first cyclization proceeds from (halocinnamyl)aniline derivatives, we initially tested the reaction of monobromide 13 under typical palladiumcatalyzed reaction conditions (Scheme 5). As expected, treatment of 13 with [PdA C H T U N G T R E N N U N G (PPh 3) 4 ] (5 mol %) and Cs 2 CO 3 in MeCN gave the desired monocyclization product 14 in 94 % yield. The resulting benzylideneindoline derivative 14 was quantitatively isomerized to the corresponding indole 15 in CDCl 3 within 24 h at room temperature. Next, we tested the palladium-catalyzed double C À H functionalization of dibromides 7 (Table 1). Unfortunately, the reaction of dibromopivalamide 7 a with [PdA C H T U N G T R E N N U N G (PPh 3) 4 ] (5 mol %) and Cs 2 CO 3 in MeCN only gave the monocyclization product 17 a in low yield (28 %; Table 1, entry 1). In contrast, conducting the reaction with an increased amount of [PdA C H T U N G T R E N N U N G (PPh 3) 4 ] (10 mol %) in dioxane partially promoted the double C À H functionalization to afford the desired product 16 a, albeit in low yield (11 %). Investigations using other solvents (N,N-dimethylformamide (DMF), dimethylacetamide (DMA), tetrahydrofuran (THF), toluene, and o-Scheme 2. Preparation of dibromopivalamide 7 a. Scheme 3. Preparation of dihalosulfonamides 7 and 9. Scheme 4. Preparation of substituted dibromosulfonamides 12. Scheme 5. Monocyclization of bromopivalamide 13.
Organic Letters, 2013
Palladium-catalyzed primary and secondary sp 3 CÀH bond arylation is reported. The method using diarylhyperiodonium salts as arylation reagents shows good functional group tolerance and proceeds under mild reaction conditions. The KIE experiments show that the CÀH bond activation is the rate-determining step. Transition-metal-catalyzed direct CÀH arylation has emerged as an attractive alternative to traditional synthetic methods. 1 In comparison, most achievements in this field to carry out the formation of CÀC bonds or CÀN bonds are being focused on the activation of sp 2 CÀH bonds of (hetero)arenes. 2 The unreactive sp 3 CÀH activation remains challenging, facing problems that approach both efficiency and selectivity. 3 Some achievements have been made to functionalize the relatively active benzylic and allylic CÀH bonds directly. 4 More recently, many efforts have also been made to perform direct functionalization of the "unreactive" sp 3 CÀH bonds via Pd catalysis. For example, work to achieve Pd-catalzyed "unreactive" sp 3 CÀH arylation was accomplished by using the Nor S-contained directing groups with either aryl halides or organometallic reagents as arylation reagents. 5 Daugulis
ChemInform, 2014
Palladium-Catalyzed C-H Acetoxylation of 2-Methoxyimino-2-aryl-acetates and Acetamides.-The direct C-H acetoxylation of the title compounds affords the oxidative coupling products in moderate to good yields. A number of alkyl and alkoxy substituents can be incorporated into the benzene ring at ortho-, meta-, and para positions without significant loss in reaction efficiency. Accordingly, the structural variation of the ester and amide moieties in the acetoxylation reaction is carried out, cf. (VIII). Interestingly, changing the solvent to tBu-COOH results in a pivaloyloxylation product. Furthermore, the resulting α-imino esters can be easily converted into naturally unprecedented α-amino acids in almost quantitative yields.-(WANG, L.;
Palladium-carbene catalyzed direct arylation of five-membered heteroaromatics
Journal of Molecular Structure, 2020
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