171484-64-3

Upstream product

• 100-42-5 styrene 
• 591-50-4 iodobenzene 
• 164071-99-2 [Pd(PPh₃)3(CH₃COO)]^(1-) 
• 106354-46-5 [PdPh(μ-O₂CMe)(PPh₃)]₂ 
• 603-35-0 triphenylphosphine 
• 18494-74-1 2-methyl-2,5'-bithiophene 
• 1826-11-5 2-phenylthiazole 
• 363-72-4 Pentafluorobenzene 
• 872-55-9 2-ethylthiophene 
• 554-14-3 2-Methylthiophene 
• 10577-68-1 2-deuterio-5-methylthiophene 
• 20637-27-8 2-deuteriobenzothiazole 
• 95-16-9 1,3-Benzothiazole 
• 95-15-8 Benzo[b]thiophene 

Downstream Products

• 352454-64-9 trans-Ph(p-MeC₆H₄O)Pd(PPh₃)2 

Relevant academic research and scientific papers

Factors controlling the reactivity of heteroarenes in direct arylation with arylpalladium acetate complexes

The palladium-catalyzed direct arylation of heteroarenes with aryl halides has emerged as a viable alternative to conventional cross-coupling reactions. This paper reports a detailed mechanistic study on factors controlling the reactivity of heteroarenes in direct arylation with well-defined models of the presumed intermediate [PdAr(O2CMe-κ2O)L] (1). Although recent theoretical studies have provided a reasonable description of the mechanism of C-H bond cleavage by 1, its model compounds so far tested have been evidently less reactive than that expected. We found that [PdPh(O 2CMe-κ2O)(PPh3)] (1a) and [Pd(2,6-Me 2C6H3)(O2CMe-κ2O) (PPh3)] (1c), generated in situ from isolated [PdPh(μ-O 2CMe)(PPh3)]2 (4a) and [Pd(2,6-Me 2C6H3)(μ-O2CMe)(PPh 3)]4 (4c), respectively, react with a variety of heteroarenes in almost quantitative yields. The reactivity order of heteroarenes was evaluated by competitive reactions, showing that benzothiazole (8) is significantly less reactive than 2-methylthiophene (6), despite the acidity of 8 (pKa = 27) being much higher than that of 6 (pKa = 42). This reason was examined by kinetic experiments using 1c as well as DFT calculations using the model compound [PdPh(O2CMe- κ2O)(PH3)] (1d). Both heteroarenes reacted with 1 via a sequence of three elementary processes (i.e., substrate coordination, C-H bond cleavage, and C-C reductive elimination), but their energy profiles were significantly different from each other. The reaction of 6 obeyed simple second-order kinetics, and the deuterium-labeling experiments and DFT calculations indicated the occurrence of rate-determining reductive elimination. On the other hand, the reaction of 8 displayed saturation kinetics due to the occurrence of relatively stable coordination of 8 prior to C-H bond cleavage. This coordination stability enhances the activation barrier for C-H bond cleavage, thereby causing the modest reactivity of 8. Thus, although the previous mechanistic studies on direct arylation have been focused largely on the C-H bond cleavage process, not only the C-H bond cleavage but also the substrate coordination and C-C reductive elimination must be considered.

Direct arylation of 2-methylthiophene with isolated [PdAr(μ-O 2CR)(PPh3)]n complexes: Kinetics and mechanism

The palladium-catalyzed direct arylation of aromatic compounds with aryl halides has been proposed to involve an arylpalladium carboxylate intermediate. However, isolated arylpalladium complexes, which undergo C-H bond cleavage of aromatic substrates without the aid of additional activators or promoters, have been scarcely documented. This paper reports that [PdAr(μ-O 2CR)(PPh3)]n complexes (1: Ar = Ph, 2-MeC 6H4, 2,6-Me2C6H3; R = Me, tBu) successfully react with 2-methylthiophene (2) in the absence of additives to afford 5-aryl-2-methylthiophenes (3) in high yields. The reactivity increases with increasing bulkiness of the Ar group, whereas the bulky pivalate ligand (R = tBu) reduces the reactivity as compared with the acetate ligand (R = Me). Complex 1 is in equilibrium with the monomeric species [PdAr(O2CR-κ2O)(PPh3)] (5) in solution, as confirmed by IR spectroscopy. Kinetic examinations have suggested that the direct arylation proceeds via 5, which undergoes C-H bond cleavage of 2. Complex 1 serves as a good catalyst for direct arylation of 2 with aryl bromides.

Decelerating effect of alkenes in the oxidative addition of phenyl iodide to palladium(0) complexes in heck reactions

In DMF, the oxidative addition of PhI to Pd0(PPh3)4 or to the anionic Pd0(PPh3)3(OAc)- is slower in the presence of an alkene (styrene, methyl acrylate). Indeed, the concentration of the reactive Pd0(PPh3)2 or Pd0(PPh3)2(OAc)- complex decreases because of its coordination to the alkene to form the unreactive (η2-CH2=CHR)Pd0(PPh3)2 (R = Ph, CO2Me) or (η2-CH2= CHPh)Pd0(PPh3)2(OAc)-, respectively. As already evidenced in palladium-catalyzed Stille reactions, this work establishes that, in palladium-catalyzed Heck reactions as well, the nucleophile plays a role in the kinetics of the oxidative addition (decelerating effect), as soon as it may coordinate Pd0 complexes. This is an essential observation, in view of the general belief that the nucleophile enters the catalytic cycle only at the stage of the attack on the aryl-PdII complex formed in the oxidative addition. Whenever the oxidative addition is not rate determining, the decelerating effect of the alkene on this reaction is in favor of a higher efficiency of the catalytic cycle.

Palladium-catalyzed coupling reactions of biphenylene with olefins, arylboronic acids, and ketones involving C-C bond cleavage

The reaction of biphenylene with olefins in the presence of Pd(PPh3)4 leads to the catalytic formation of products arising from addition of the vinylic C-H bond across the carbon - carbon bond of biphenylene. Weak acids are found to

The first isolable organopalladium formato complexes: Synthesis, characterization, and x-ray structure. Facile and convenient thermal generation of coordinatively unsaturated palladium(0) species

[L2Pd2(RM1(μ-OH)2] complexes (L = PPh3, R = Ph, Me) react with formic acid in benzene to give the first stable organopalladium formates, [L2Pd2(R)2(μ-HCOO)2

Evidence for the ligation of palladium(0) complexes by acetate ions: Consequences on the mechanism of their oxidative addition with phenyl iodide and PhPd(OAc) (PPh3)2 as intermediate in the heck reaction

Addition of acetate anions to solutions of Pd0(PPh3)4 results in the formation of anionic species in which the acetate ion coordinates the palladium(0) center, Pd0(PPh3)3(OAc)-, which is in equilibrium with the less ligated complex, Pd0(PPh3)2(OAc)-. The latter undergoes oxidative addition with phenyl iodide to afford a mixture of PhPdI(PPh3)2 and PhPd(OAc)-(PPh3)2. Acetate ions react with PhPdI(PPh3)2 to afford PhPd(OAc)(PPh3)2. Mixtures of Pd-(OAc)2 and nPPh3 (n ≥ 4), commonly used as catalysts in Heck reactions, afford a palladium(0) complex that is ligated by one acetate ion, yielding the anionic species Pd0(PPh3)3(OAc)- and Pd0(PPh3)2(OAc)-. The latter reacts with phenyl iodide. However, this reaction does not afford the expected PhPdI(PPh3)2 complex but instead affords PhPd(OAc)(PPh3)2. Reaction of PhPd(OAc)(PPh3)2 with styrene results in the formation of stilbene, demonstrating that PhPd(OAc)(PPh3)2 is an intermediate in the Heck reaction.