Carbonylative cross-coupling reaction of ethynylstibane with aryl iodides

Palladium-catalyzed carbonylative cross-coupling reaction of ethynylstibane (PhSbPh(2)) and aryl iodides (Ar-I) is described. The reaction of the stibanes and the halides under 1 atm of carbon monoxide in N,N-dimethylacetamide using a combination of 5 mol% Pd(OAc)(2) and 4 equivalents (20 mol%) of PPh(3) brought about carbonylative cross-coupling reaction to afford arylethynylketones [ArC(O)Ph] in good yields along with a small amount of directly coupled products, aryl acetylens (ArPh). Formation of the side product was completely suppressed by conducting the reaction under high CO pressure (20 atm) conditions. The present method provides a variety of carbonylated products in good yield even with electron-deficient aryl iodides which usually give inferior results due to their tendency to undergo decarbonylation in the cross-coupling reaction of ethynylstibanes and acyl halides.     

乙二醇中钯催化无配体的室温Suzuki反应

报道了一种在室温下醋酸钯催化乙二醇中无外加配体的Suzuki反应体系.以K3PO4·7H2O为碱,在该体系中可高效进行芳基溴代物和芳基硼酸的Suzuki交叉偶联反应,具有反应条件温和、无需惰性气体保护等特点.在n(ArBr)=0.5mmol,n(ArB(OH)2)=0.75mmol,x(Pd(OAc)2)=0.5mol%,n(K3PO4·7H2O)=1.0mmol,v(乙二醇)=2ml的优化条件下,4-溴苯甲醚和苯硼酸反应20min,分离收率即达95%.     

醋酸钯催化甲苯中无配体的 Suzuki 反应

 报道了一种甲苯中醋酸钯催化无配体的 Suzuki 反应体系. 以 K₃PO₄·7H₂O 为碱, 在该体系中可高效进行芳基溴代物和芳基硼酸的 Suzuki 反应, 且具有反应条件温和、无需惰性气体保护等特点. 在 n(ArBr) = 0.5 mmol, n(ArB(OH)₂) = 0.75 mmol, x(Pd(OAc)₂) = 1 mol%, n(K₃PO₄·7H₂O) = 1.0 mmol, v(甲苯) = 2 ml 的优化条件下, 4-溴硝基苯和苯硼酸在 75 °C 反应 5 min, 分离收率即达 99%, TOF 高达 1 188 h?1.     

Pd(OAc)2-catalyzed oxidative coupling reaction of benzenes with olefins in the presence of molybdovanadophosphoric acid under atmospheric dioxygen and air

The direct oxidative coupling reaction of benzenes with alkenes bearing an electron-withdrawing group was successfully achieved by the use of Pd(OAc)(2)/molybdovanadophosphoric acid (HPMoV) as the key catalyst under O(2) or air atmosphere. Thus, the reaction of benzene with ethyl acrylate under air (1 atm) assisted by Pd(OAc)(2)/HPMoV afforded ethyl cinnamate as a major product in satisfactory yield (74%). This catalytic system could be extended to the coupling reactions between various substituted benzenes and alkenes through the direct aromatic C-H bond activation. In the reaction of benzene with ethyl acrylate under O(2) (1 atm), the best turn-over number (TON) of Pd(OAc)(2) reached was 121. This reaction provides a green route to cinnamate derivatives, which are important precursors of a variety of pharmaceuticals.     

Palladium-catalyzed Suzuki cross-coupling of 2-haloselenophenes: synthesis of 2-arylselenophenes, 2,5-diarylselenophenes, and 2-arylselenophenyl ketones

We present herein our results on the Suzuki coupling reaction of 2-haloselenophenes with boronic acids catalyzed by palladium salt and describe a new route established to prepare 2-arylselenophenes and 2,5-diarylselenophenes in good yields. The reaction proceeded cleanly under mild conditions and was performed with aryl boronic acids bearing electron-withdrawing, electron-donating, and neutral substituents, in the presence of Pd(OAc)2, K2CO3/H2O in DME. In addition, by this protocol unsymmetrical aryl ketones were also obtained from 2-iodoselenophene and boronic acids via a carbonylative process.     

Phosphonation of arenes with dialkyl phosphites catalyzed by Mn(II)/Co(II)/O2 redox couple

[reaction: see text]. Arylphosphonates were first synthesized through a catalytic phosphonation of various arenes with dialkyl phosphites under the influence of an Mn(OAc)2/Co(OAc)2/O2 redox couple. For instance, the reaction of benzene with diethyl phosphite in the presence of Mn(OAc)2 (5 mol %) and Co(OAc)2 (1 mol %) under a mixed gas of O2 (0.5 atm) and N2 (0.5 atm) at 45 degrees C led to diethyl phenylphosphonate in 81% selectivity at 62% conversion. This is the first successful phosphonation of benzene with dialkyl phosphites through a catalytic radical process.     

Palladium-catalyzed carbonylative cyclization of unsaturated aryl iodides and dienyl triflates,iodides, and bromides to indanones and 2-cyclopentenones

Indanones and 2-cyclopentenones have been successfully prepared in good to excellent yields by the palladium-catalyzed carbonylative cyclization of unsaturated aryl iodides and dienyl triflates, iodides, and bromides, respectively. The best results are obtained by employing 10 mol % of Pd(OAc)(2), 2 equiv of pyridine, 1 equiv of n-Bu(4)NCl, 1 atm of CO, a reaction temperature of 100 degrees C, and DMF as the solvent. This carbonylative cyclization is particularly effective on substrates that contain a terminal olefin. The proposed mechanism for this annulation includes (1) Pd(OAc)(2) reduction to the active palladium(0) catalyst, (2) oxidative addition of the organic halide or triflate to Pd(0), (3) coordination and insertion of carbon monoxide to produce an acylpalladium intermediate, (4) acylpalladation of the neighboring carbon-carbon double bond, (5) reversible palladium beta-hydride elimination and re-addition to form a palladium enolate, and (6) protonation by H(2)O to produce the indanone or 2-cyclopentenone.     

Palladium-catalyzed mono-N-allylation of unprotected amino acids with 1,1-dimethylallyl alcohol in water

Palladium-catalyzed N-allylation of unprotected amino acids with 1,1-dimethylallyl alcohol were carried out. The reaction in the presence of Pd(OAc)(2) (5 mol%), sodium diphenylphosphinobenzene-3-sulfonate (TPPMS, 10 mol%), and AcONa (2 equiv) in water at 120 °C for 16 h in a sealed tube gave only mono-N-allylated amino acids in good yield.     

Oxidative coupling of benzenes with alpha,beta-unsaturated aldehydes by the Pd(OAc)2/molybdovanadophosphoric acid/O2 system

[reaction: see text] The oxidative coupling reaction of benzene with an alpha,beta-unsaturated aldehyde was examined by the combined catalytic system of Pd(OAc)2 with molybdovanadophosphoric acid (HPMoV) under atmospheric dioxygen. Thus, the reaction of benzene with acrolein under dioxygen (1 atm) by the use of catalytic amounts of Pd(OAc)2 and H4PMo11VO40 x 26H2O in the presence of dibenzoylmethane as a ligand in propionic acid at 90 degrees C for 1.5 h afforded cinnamaldehyde in 59% yield and beta-phenylcinnamaldehyde in 5% yield. This catalytic system was extended to the direct oxidative coupling through the C-H bond activation of various arenes with acrolein and methacrolein.     

Trisannelation of acrylates to 1,3,5-benzenetricarboxylates by a Pd(OAc)2/HPMoV/CeCl3/O2 system

A new type of trisannelation reaction of acrylates through acetal formation was developed by Pd(OAc)2 combined with molybdovanadophosphoric acid (HPMo8V4) and Lewis acid under atmospheric dioxygen. Thus, the reaction of isobutyl acrylate in the presence of Pd(OAc)2, HPMo8V4, and CeCl3 under O2 (1 atm) in MeOH/AcOH afforded isobutyl 1,3,5-benzenetricarboxylate in fair yield. The reaction was found to proceed through the palladium-catalyzed acetalization of acrylate with methanol followed by the trisannelation reaction of the resulting acetal promoted by CeCl3.     

Acetalization of alkenes catalyzed by Pd(OAc)2/NPMoV supported on activated carbon under a dioxygen atmosphere

[reaction: see text] The acetalization of terminal alkenes such as ethyl acrylate and acrylonitrile with alcohols under O2 was efficiently achieved by Pd(OAc)2 supported on activated carbon combined with molybdovanadophosphate (NPMoV). For example, ethyl acrylate was subjected to acetalization with EtOH acidified by CH3SO3H under O2 (1 atm) in the presence of [8 wt%Pd(OAc)2/C] and NPMoV to form ethyl 3,3-diethoxypropionate in quantitative yield.     

Cu(OAc)2·H2O/NH2OH·HCl/CH3COONa: A Facile and Efficient Catalyst System for Copper‐catalyzed Azide–Alkyne Click Reactions in Water

A facile and efficient protocol has been developed for synthesis of 1,4‐disubstituted 1,2,3‐triazoles in good to excellent yields using Cu(OAc)₂·H₂O (0.5 mol%)/NH₂OH·HCl (0.5 mol%)/CH₃COONa (1.0 mol%) as the catalyst system. The presence of CH₃COONa (2 equiv) could ensure the in situ generation of Cu₂O as the active catalyst instead of CuCl from Cu(OAc)₂·H₂O (1 equiv)/NH₂OH·HCl (1 equiv). This protocol could be carried out in water under mild conditions.     

Oxidative cross-coupling of acrylates with vinyl carboxylates catalyzed by a Pd(OAc)2/HPMoV/O2 system

Oxidative cross-coupling of acrylates with vinyl carboxylates was first successfully achieved by the use of a Pd(OAc)(2)/HPMoV/O(2) system in fair to good yields. For instance, the reaction of n-butyl acrylate with vinyl acetate in the presence of catalytic amounts of Pd(OAc)(2) and H(4)PMo(11)VO(40).nH(2)O under O(2) in acetic acid at 70 degrees C for 12 h afforded the corresponding cross-coupling product, n-butyl 5-(acetoxy)-2,4-pentadienoate, in 70% yield.     

Oxidation of nitrotoluenes with air using N-hydroxyphthalimide analogues as key catalysts

Nitrotoluenes are efficiently oxidized with air to the corresponding nitrobenzoic acids by the use of N-acetoxyphthalimide (NAPI) as a key catalyst. Thus, p- and m-nitrotoluenes under 10 atm of air in the presence of NAPI combined with Co(OAc)₂ (0.5 mol%) and Mn(OAc)₂ (0.05 mol%) at 130°C afforded p- and m-nitrobenzoic acids in 81 and 92% yields, respectively. o-Nitrotoluene was oxidized to o-nitrobenzoic acid in 51% yield by the aid of NO₂.     

无配体、在空气下Pd(OAc)_2催化的Heck反应研究

研究了无配体、空气下Pd(OAc)2催化的Heck反应.多种芳基碘化物、芳基溴化物可以与烯丙基醋酸酯、丙烯酸酯和苯乙烯等烯基化合物在Pd(OAc)2催化下发生Heck反应.该反应不需要配体的加入,在空气中就可以进行.讨论了碱、添加剂、溶剂、催化剂等因素对反应产率的影响.该反应的最优化条件是:Pd(OAc)2(5mol%)为催化剂,Ag2CO3(0.6equiv.)为添加剂,以苯或甲苯为溶剂空气中回流12h,芳基碘化物、芳基溴化物可以顺利地与烯丙基醋酸酯、丙烯酸酯、苯乙烯等烯基化合物发生Heck反应,以较高的产率得到目标产物.     

Pd(OAc)2-catalyzed carbonylation of amines

A phosphine-free catalytic system [Pd(OAc)2-Cu(OAc)2-air] induced a substrate-specific carbonylation of amines in boiling toluene under CO gas (1 atm). Symmetrical N,N'-dialkylureas were obtained by the carbonylation of primary amines. N,N,N'-Trialkylureas were selectively formed by addition of a secondary amine to the above reaction vessel. Secondary amines did not give tetraalkylureas. However, dialkylamines with a phenyl group on their alkyl chains, such as N-monoalkylated benzylic amine or phenethylamine derivatives, underwent a direct aromatic carbonylation to afford five- or six-membered benzolactams. In the carbonylation, the chelation effect or steric repulsion between Pd(II) and the meta-substituent in the ortho-palladation and the ring sizes of cyclopalladation products that were formed prior to carbonylation were found to generate good site selectivity and increase the reaction rate. In contrast, carbonylation of omega-arylalkylamines with a hydroxyl group gave neither ureas nor benzolactams but instead produced 1,3-oxazolidinones smoothly. Hydrochlorides of amines also underwent carbonylation to afford the corresponding amides under the conditions used. This procedure made it possible to prepare ureas of amino acid esters and N-alkylcarbamates in practical yields.     

The use of Cr (CO)6 as an alternative CO source in Pd‐catalyzed C‐N bond formation: Synthesis of benzamides

An efficient strategy for the synthesis of benzamides from acetamides and aryl iodides using 1 mol% Pd (OAc)₂ as catalyst and Cr (CO)₆ as CO‐precursor is described. This new synthetic methodology displays high functional group tolerance on both substrates and avoids the need for ligands, reducing agents, or other additives. The corresponding products were obtained in good to excellent yields at atmospheric pressure under mild reaction conditions.     

Mizoroki-Heck type reaction of organoboron reagents with alkenes and alkynes. A Pd(II)-catalyzed pathway with Cu(OAc)2 as an oxidant

[reaction: see text]. In contrast to the Pd(0)-catalyzed mechanism by Uemura, Mizoroki-Heck type reaction of boronic acids is found to proceed under a Pd(II)-mediated pathway using a catalytic amount of Pd(OAc)2 in the presence of Cu(OAc)2 as an oxidant. Treatment of a variety of alkenes with boronic acids, boronates, and sodium tetraphenylborate furnishes beta-arylated and alkenylated products in good to excellent yields. The reactions with norbornene, norbornadiene, and diphenylacetylene are also performed to give 1:2 or 2:1 coupling products.     

Allylic C-H acetoxylation with a 4,5-diazafluorenone-ligated palladium catalyst: a ligand-based strategy to achieve aerobic catalytic turnover

Pd-catalyzed C-H oxidation reactions often require the use of oxidants other than O(2). Here we demonstrate a ligand-based strategy to replace benzoquinone with O(2) as the stoichiometric oxidant in Pd-catalyzed allylic C-H acetoxylation. Use of 4,5-diazafluorenone (1) as an ancillary ligand for Pd(OAc)(2) enables terminal alkenes to be converted to linear allylic acetoxylation products in good yields and selectivity under 1 atm O(2). Mechanistic studies have revealed that 1 facilitates C-O reductive elimination from a π-allyl-Pd(II) intermediate, thereby eliminating the requirement for benzoquinone in this key catalytic step.     

无配体、在空气下Pd(OAc)2催化的Heck反应研究

研究了无配体、空气下Pd(OAc)₂催化的Heck反应. 多种芳基碘化物、芳基溴化物可以与烯丙基醋酸酯、丙烯酸酯和苯乙烯等烯基化合物在Pd(OAc)₂催化下发生Heck反应. 该反应不需要配体的加入, 在空气中就可以进行. 讨论了碱、添加剂、溶剂、催化剂等因素对反应产率的影响. 该反应的最优化条件是: Pd(OAc)₂ (5 mol%)为催化剂, Ag₂CO₃ (0.6 equiv.)为添加剂, 以苯或甲苯为溶剂空气中回流12 h, 芳基碘化物、芳基溴化物可以顺利地与烯丙基醋酸酯、丙烯酸酯、苯乙烯等烯基化合物发生Heck反应, 以较高的产率得到目标产物.