An alternative approach to 3-(diphenylphosphino)hexahelicene

3-(Diphenylphosphino)hexahelicene is synthesised in good yield and purity, via a three-step sequence involving a palladium-catalysed Mizoroki-Heck coupling reaction and classical oxidative photocyclisation. Mononuclear ruthenium and palladium complexes of 3-(diphenylphosphino)hexahelicene are prepared and characterised.     

A new access to 3-substituted-1(2H)-isoquinolone by tandem palladium-catalyzed intramolecular aminocarbonylation annulation

An original tribromide derivative based, palladium-catalyzed synthesis of 3-substituted-1(2H)-isoquinolone is described based on a regioselective Suzuki-Miyaura C-C coupling on o-halo-(2,2-dihalovinyl)-benzene followed by a palladium catalyzed amination-carbonylation-cyclization reaction. This sequence efficiently proceeds to build up isoquinolone in fair to good yields over a one-pot 3-bond synthesis reaction.     

Palladium‐Catalyzed Intramolecular Carbene Insertion into C(sp3)−H Bonds

A palladium‐catalyzed carbene insertion into C(sp³)?H bonds leading to pyrrolidines was developed. The coupling reaction can be catalyzed by both Pd⁰ and Pd^II, is regioselective, and shows a broad functional group tolerance. This reaction is the first example of palladium‐catalyzed C(sp³)?C(sp³) bond assembly starting from diazocarbonyl compounds. DFT calculations revealed that this direct C(sp³)?H bond functionalization reaction involves an unprecedented concerted metalation–deprotonation step.     

Coordination of Lewis acid to eta(2)-enonepalladium(0) leading to continuous structure variation from eta(2)-olefin type to eta(3)-allyl type.

The reaction of alpha,beta-unsaturated carbonyl compounds, a palladium(0) complex, and Lewis acids led to the formation of a new class of complexes showing a wide variety of structures with eta(2)-type and eta(3)-type coordination of the carbonyl compounds. The reaction of Pd(PhCH=CHCOCH(3))(PPh(3))(2) with BF(3).OEt(2) or B(C(6)F(5))(3) quantitatively gave palladium complexes 1a,b having BX(3)-coordinated eta(2)-enonepalladium structure, as revealed by X-ray structure analysis of the B(C(6)F(5))(3) adduct 1b. On the other hand, the reaction of Pd(PhCH=CHCHO)(PPh(3))(2) with BF(3).OEt(2) or B(C(6)F(5))(3) gave distorted zwitterionic eta(3)-allylpalladium complexes 3a,b, where the Pd-carbonyl carbon distance in 3a (2.413(4) A) is much shorter than that (2.96(1) A) in 1b. The values of the P-P coupling constant and (13)C chemical shift for carbonyl carbon are useful criteria for predicting how the eta(3)-coordination mode contributes to the structure of the enone-palladium-Lewis acid system. Molecular orbital calculations on the series of model complexes suggest that orbital overlap in the highest occupied molecular orbital between the palladium and carbonyl carbon is enlarged by coordination of the Lewis acid to the carbonyl group. Palladium-catalyzed conjugate addition of R-M (R-M = AlMe(3), AlEt(3), ZnEt(2)) and its plausible reaction path are also reported.     

Palladium‐Catalyzed [3+3] Annulation of Vinyl Chromium(0) Carbene Complexes through Carbene Migratory Insertion/Tsuji–Trost Reaction

Vinyl chromium(0) Fischer carbene complexes were employed as the source of π‐allylic palladium species for catalytic [3+3] annulation under palladium catalysis. Mechanistically, this transformation is proposed to involve carbene migratory insertion and intramolecular Tsuji–Trost reaction as the key steps. Substituted six‐membered heterocyclic flavonones and quinolines are obtained, depending on the nucleophilic functional group on the coupling partners.     

Stereospecific Pd‐Catalyzed Intermolecular C(sp3)–C(sp) Cross‐Coupling of Diarylmethyl Carbonates and Terminal Alkynes Under Base‐Free Conditions

A palladium‐catalyzed intermolecular decarboxylative C(sp³)–C(sp) coupling of diarylmethyl carbonates and terminal alkynes has been developed. The reaction proceeds smoothly under external base‐free conditions to deliver the corresponding alkynylated diarylmethanes with the liberation of CO₂ and MeOH as the sole byproducts. Moreover, enantioenriched diarylmethyl carbonates are stereospecifically converted to optically active cross‐coupling products with inversion of configuration. Thus, the stereospecific palladium catalysis can provide new and unique access to the alkynylated chiral tertiary stereocenters, which are relatively difficult to construct by conventional methods.     

Nano palladium catalyzed C(sp3)-H bonds arylation by a transient directing strategy

Reported herein is the first example of heterogeneous palladium catalyzed C(sp³)-H bonds arylation by a transient-ligand-directed strategy.Using supported palladium(metallic state) na nopariticles as catalyst,a wide range of aryl iodides undergo the coupling with various o-methylbenzaldehyde derivatives to assemble a library of highly selective and functionalized o-benzylbenzaldehydes.The stability of the catalyst was easily recovered four runs without significant loss of activity.The XPS analysis of the catalyst before and after reaction indicated that the reaction might be carried out by a catalytic cycle starting with Pd~0.     

Bis(imino)pyridine palladium(II) complexes: Synthesis, structure and catalytic activity

Bis(imino)pyridine palladium(II) complexes 3-6 were synthesized by two different methods. The structure of complexes 3 and 4 has been confirmed by X-ray structure analysis. The catalytic studies show that bis(imino)pyridine palladium(II) complexes are highly efficient catalysts in the Suzuki-Miyaura reaction and the complex 4 was used to catalyze the synthesis of fluorinated liquid crystalline compounds via Suzuki coupling reaction.     

A novel MCM-41-supported sulfur palladium(0) complex catalyst for Sonogashira coupling reaction

A novel MCM-41-supported sulfur palladium(0) complex was conveniently prepared from commercially available and cheap γ-mercaptopropyltriethoxysilane via immobilization on MCM-41, followed by reacting with palladium chloride and then the reduction with hydrazine hydrate. This complex exhibited excellent performance in Sonogashira coupling reaction.     

A synthetic approach for (S)-(3-benzyl-3-methyl-2,3-dihydro-benzofuran-6-yl)-piperidin-1-yl-methanone,a selective CB2 receptor agonist

(S)-(3-Benzyl-3-methyl-2,3-dihydro-benzofuran-6-yl)-piperidin-1-yl-methanone, a selective CB2 receptor agonist, was obtained from 3-hydroxy-4-iodo benzoic acid in nine steps with 97.4% ee and 3.4% total yield, which involved palladium catalyzed tandem intramolecular Heck/Suzuki cross coupling reaction, chemical resolution with (+)-norephedrine and Wolf–Kishner reaction as the key steps. (S)-(3-Benzyl-3-methyl-2,3-dihydro-benzofuran-6-yl)-piperidin-1-yl-methanone will be evaluated in vivo studies and this approach will be applied in the optimization process of CB2 receptor agonist.     

Synthesis and structure of preorganized,C(3)-symmetric trilactam scaffolds with convergently oriented (S)-acetylthiomethyl appendages

[reaction: see text] Efficient modular synthesis of conformationally preorganized, C(3)-symmetric trilactams is reported. The allyl acetate cyclization substrate was synthesized in five steps from Garner's L-serine-derived aldehyde. After chiral ligand-mediated palladium cyclization, the resulting vinyl hydropyran was transformed into the orthogonally protected amino acids for iterative coupling. The final macrolactamization was accomplished using EDCI/HOBt or HATU/HOAt under high dilution conditions.     

Synthesis and reactivity of 1,2-bis(chlorodimethylgermyl)carborane and 1,2-bis(bromodimethylstannyl)carborane

The 1,2-bis(chlorogermyl)- (1) and 1,2-bis(bromostannyl)carborane (2) have been prepared by the reaction of dilithio-o-carborane with Me(2)GeCl(2) and Me(2)SnBr(2), respectively. Compounds 1 and 2 are found to be good precursors for the synthesis of a variety of cyclization compounds. The Wurtz-type coupling reaction of 1 and 2 using sodium metal afforded the four-membered digerma compound 3 and five-membered tristanna compound 4, respectively. The salt elimination reactions of 1 and 2 using Li(2)N(t)Bu and Li(2)PC(6)H(5) afforded the cyclic products [structure: see text]. The 1,2-bis(dimethylgermyl)carborane 9 and 1,2-bis(dimethylstannyl)carborane 10 were prepared by the reaction of 1 and 2 with sodium cyanoborohydride. The reactions of 9 and 10 with Pd(PPh(3))(4) afforded the bis(germyl)palladium 12 and bis(stannyl)palladium 13 complexes, respectively.     

Palladium-catalyzed tetrakis(dimethylamino)ethylene-promoted reductive coupling of aryl halides

Tetrakis(dimethylamino)ethylene (TDAE)/cat. PdCl(2)(PhCN)(2)-promoted reductive coupling of aryl bromides having either electron-donating or electron-withdrawing groups on their para- and/or meta-position proceeded smoothly to afford the corresponding biaryls in good to excellent yields. Notably, TDAE is such a mild reductant that easily reducible groups, such as carbonyl and nitro groups, are tolerate. A similar reductive coupling of ortho-substituted aryl bromides did not occur at all. The proper choice of palladium catalysts is essential for the reductive coupling; thus, PdCl(2)(PhCN)(2), PdCl(2)(MeCN)(2), Pd(hfacac)(2), Pd(2)(dba)(3), PdCl(2), and Pd(OAc)(2) were used successively for this reaction, but phosphine-ligated palladium catalysts such as Pd(PPh(3))(4), PdCl(2)(PPh(3))(2), and Pd(dppp) did not promote the reaction. The reductive coupling did not occur with nickel catalysts such as NiBr(2), NiCl(2)(bpy), and Ni(acac)(2). The TDAE/cat. palladium-promoted reductive coupling of aryl halides having electron-withdrawing groups took place more efficiently than that of aryl halides substituted with electron-donating groups. A plausible mechanism of TDAE/cat. palladium-promoted reaction is discussed.     

(t-Bu)2PN=P(i-BuNCH2CH2)3N: new efficient ligand for palladium-catalyzed C-N couplings of aryl and heteroaryl bromides and chlorides and for vinyl bromides at room temperature

By employing Pd(OAc)2, Cs2CO3, or NaOH, and the new ligand (t-Bu)2PN=P(i-BuNCH2CH2)3N (3a), an electronically diverse array of aryl bromides and chlorides possessing base-sensitive substituents (nitro, ester, and keto) provide coupling products with bulky aryl amines in good to excellent yields. Aryl halides possessing other functional groups including cyano, amino, trifluoromethyl, and phenol, coupled with equal ease, producing highly functionalized amines in good to excellent yields. Moreover, an aryl chloro group can be preserved in the presence of a bromo substituent under our reaction conditions. BOC-protected amines also participated efficiently. Heterocyclic bromides and chlorides underwent clean couplings with amines in excellent yields. An important strength of our protocol is the use of lower palladium loadings than those reported earlier, without compromising yields. The air-stable palladium complex (eta3-cinnamyl)PdCl.(3a) (5) was also employed successfully in C-N coupling reactions while the crotyl analogue was less efficacious. The 3a/Pd(OAc)2 catalyst system promotes, for the first time, efficient coupling of vinyl bromides with a variety of amines to produce imines and enamines at room temperature.     

Rapid access to 3-(N-substituted)-aminoquinolin-2(1H)-ones using palladium-catalyzed C-N bond coupling reaction

A series of 3-(N-substituted)-aminoquinolin-2(1H)-ones have been synthesized by the palladium-catalyzed C-N coupling reaction starting from 3-bromoquinolin-2-(1H)-ones. Various nucleophiles including amines, amides, sulfonamides, carbamates and ureas have been used successfully. In all the cases, the reactions take place rapidly in 1,4-dioxane and proceed in good to excellent yield using palladium acetate as a catalyst, Xantphos as a ligand and Cs₂CO₃ as a base.     

A versatile palladium-mediated three-component reaction for the one-pot synthesis of stereodefined 3-arylidene-(or 3-alkenylidene-)tetrahydrofurans.

A one-pot reaction between equimolecular amounts of various propargyl alcohols, Michael acceptors, and unsaturated halides (or triflates) in the presence of a palladium(0) catalyst provides a simple and flexible entry into highly substituted 3-arylidene-(or 3-alkenylidene-)tetrahydrofurans. The efficiency of this palladium-mediated three-component reaction has been shown to be strongly influenced by the nature of the catalyst system, and in this regard, a palladium(0) catalyst generated in situ by reduction of PdCl2(PPh3)2 with n-butyllithium has been found particularly effective.     

Four-component coupling reactions of silylacetylenes, allyl carbonates, and trimethylsilyl azide catalyzed by a Pd(0)-Cu(I) bimetallic catalyst. Fully substituted triazole synthesis from seemingly internal alkynes

Fully substituted triazoles were synthesized via the four-component coupling reaction of unactivated silylacetylenes, two equivalents of allyl carbonates, and trimethylsilyl azide in the presence of a Pd(0)-Cu(I) bimetallic catalyst. Various trisubstituted 1,2,3-triazoles were obtained in good yields. The reaction most probably proceeds through the [3+2] cycloaddition reaction between the alkynylcopper species and azide followed by the cross-coupling reaction between the vinylcopper intermediate and π-allylpalladium complex.     

Oxidative addition of N-halosuccinimides to palladium(0): the discovery of neutral palladium(II) imidate complexes, which enhance Stille coupling of allylic and benzylic halides

The Stille coupling of organostannanes and organohalides, mediated by air and moisture stable palladium(II) phosphine complexes containing succinimide or phthalimide (imidate) ligands, has been investigated. An efficient synthetic route to several palladium(II) complexes containing succinimide and phthalimide ligands, has been developed. cis-Bromobis(triphenylphosphine)(N-succinimide)palladium(II) [(Ph₃P)₂Pd(N-Succ)Br] is shown to mediate the Stille coupling of allylic and benzylic halides with alkenyl, aryl and allyl stannanes. In competition experiments between 4-nitrobromobenzene and benzyl bromide with a cis-stannylvinyl ester, (Ph₃P)₂Pd(N-Succ)Br preferentially cross-couples benzyl bromide, whereas with other commonly employed precatalysts 4-nitrobromobenzene undergoes preferential cross-coupling. Furthermore, preferential reaction of deactivated benzyl bromides over activated benzyl bromides is observed for the first time. The type of halide and presence of a succinimide ligand are essential for effective Stille coupling. The type of phosphine ligand is also shown to alter the catalytic activity of palladium(II) succinimide complexes.     

Magnetically‐recoverable Schiff Base Complex of Pd (II) Immobilized on Fe3O4@SiO2 Nanoparticles: An Efficient Catalyst for Mizoroki‐Heck and Suzuki‐Miyaura Coupling Reactions

The activity of Pd(II)‐Schiff base complex molecules grafted on the surface of Fe₃O₄@SiO₂ particles were investigated in the palladium‐catalyzed coupling reactions of aryl halides with alkenes (Mizoroki‐Heck reaction) and phenylboronic acids (Suzuki‐Miyaura reaction) in the absence of phosphorous ligands. This method shows notable advantages such as heterogeneous nature of the catalyst, excellent yields, short reaction times, easy preparation, simplicity of operation, and cleaner reaction profiles. The catalyst can be separated from the reaction mixture by applying a permanent magnet externally and can be reused for several times without significant loss of activity. Also, the amount of palladium leaching has been determined by ICP analysis.     

2-Trialkylstannyl-5-tert-butoxyfurans: Convenient 5-Substituted-2(3H)-Furanone Synthons

A versatile and mild route to 5-substituted-2(3H)-furanones (butenolides) from the palladium catalyzed coupling of aryl halides and 2-trialkylstannyl-5-tert-butoxyfurans is described.