Unprecedented palladium-catalyzed cross-coupling reaction of alpha-bromo sulfoxides with boronic acids

[reaction: see text] A new Suzuki-type palladium-catalyzed reaction of boronic acids with alpha-bromo sulfoxides has been developed using a protocol similar to the well-documented reaction of boronic acids with aryl halides. Both cross-coupling and homocoupling processes were observed. The best yields in cross-coupling products were obtained when the presence of oxygen was carefully excluded using degassed solvents. The oxidative addition palladium complex intermediate could be isolated and characterized by X-ray single-crystal diffraction.     

The palladium-catalyzed cross-coupling reaction of carboxylic anhydrides with arylboronic acids: a DFT study

The mechanism of the cross-coupling of phenylboronic acid with acetic anhydride, a viable model of the widely used Suzuki reaction, has been studied by DFT calculations at the BP86/6-31G level of theory. Two alternative catalytic cycles have been investigated, one starting from a neutral Pd(0)L(2) complex, the other from an anionic "Jutand-type" [Pd(0)L(2)X](-) species. The reaction profiles are in good agreement with the experimental findings, as both pathways require only moderate activation energies. Both pathways are dominated by cis-configured square-planar palladium(II)diphosphine intermediates. Despite careful investigations, we did not find in this model reaction any evidence for five-coordinate palladium(II) intermediates, which are commonly believed to cause the profound effects of counterions in palladium-catalyzed transformations. Instead, our calculations suggest that the higher catalytic activity of anionic complexes, such as [Pd(PMe(3))(2)OAc](-), may arise from their stronger ability to coordinate to carbon electrophiles. The transmetalation sequence is the same for both catalytic cycles, involving the dissociation of one phosphine ligand from the palladium. In the decisive transition state, in which the phenyl group is transferred from boron to palladium, the acetate base is found to be in a bridging coordination between these two atoms.     

Water works: an efficient palladium-catalyzed cross-coupling reaction between boronic acids and bromoacetate with aminophosphine ligand

Water greatly restrained the formation of self-coupling of boronic acids in a palladium-catalyzed cross-coupling reaction between boronic acids and ethyl bromoacetate with an aminophosphine ligand; good to excellent yields of cross-coupling product were obtained.     

Triarylantimony dicarboxylates as pseudo-halides for palladium-catalyzed cross-coupling reaction with arylboronic acids and triarylbismuthanes without any base

The reaction of triarylantimony diacetates (6) with organoboron reagents (9) in the presence of Pd(PPh₃)₄ led to the formation of cross-coupling products, biaryls (10, 12 and 14-17), in moderate to excellent yields under mild conditions without any base. Similar reaction of 6 with triarylbismuthanes (18) also gave the corresponding cross-coupling products. Single crystal X-ray analysis of tri(p-tolyl)antimony diacetate (6b) and tris(p-trifluoromethylphenyl)antimony diacetate (6e) revealed the geometry of both central antimony atoms being intermediate between trigonal bipyramidal and pentagonal bipyramidal arrangement with intramolecular coordination between the antimony and two carbonyl oxygen atoms with cis orientation.     

Boron trifluoride promoted reaction of benzenesulphenanilides with alkenes-arylaminosulphenylation of alkenes.

The addition of benzenesulphenanilides to alkenes in the presence of boron trifluoride provides a practicable synthetic procedure for the arylaminosulphenylation of alkenes.     

One-pot palladium-catalyzed cross-coupling reaction of aryl iodides with stannylarsanes and stannylstibanes

[reaction: see text] The reaction of Ph(3)As and Ph(3)Sb with Na metal in liquid ammonia gives Ph(2)M(-) ions (M = As, Sb) that react with n-Bu(3)SnCl to afford n-Bu(3)Sn-MPh(2) (1). The ammonia was allowed to evaporate, and toluene was added. The Pd-catalyzed cross-coupling reactions of these stannanes with aryl iodides afford functionalized triaryl-arsanes and triaryl-stibanes in high yields in a one-pot procedure (80-99%). The use of the commercially available, air-stable, and inexpensive Ph(3)M as the initial reagent and the one-pot process make this method a useful approach. This is the first report on the synthesis of 1 and the exploration of its chemistry.     

A new stereospecific cross-coupling by the palladium-catalyzed reaction of 1-alkenylboranes with 1-alkenyl or 1-alkynyl halides

The representative (E)-1-alkenyldisiamylboranes and (E)-1-alkenyl-1,3,2-benzodioxaboroles readily obtainable $\text{via}$ hydroboration of 1-alkynes react with 1-alkenyl halides or 1-alkynyl halides in the presence of a catalytic amount of tetrakis(triphenylphosphine)palladium and base to give corresponding conjugated (E)-dienes or (E)-enynes with high regio- and stereospecificity in good yields, respectively.     

Selective mono-arylation in palladium-catalyzed cross-coupling reaction of dichlorotriazines with phenylboronate ester derivatives

Palladium-catalyzed cross-coupling reaction between dichlorotriazines and phenylboronate esters produced the mono-arylated triazines selectively and thus,the corresponding phenyltriazine derivatives could be assembled efficiently in moderate to good overall yields(50-80%).     

Synthesis of the kappa-agonist CJ-15,161 via a palladium-catalyzed cross-coupling reaction

Syntheses of CJ-15,161 (1) involving intermolecular N-arylation of an appropriately functionalized diamine, obtained from the precursor alpha-amino acids or, more conveniently, from the corresponding 1,2-amino alcohols via 1,2,3-oxathiazolidine-2,2-dioxide 22, are reported.     

Efficient palladium-catalyzed homocoupling reaction and Sonogashira cross-coupling reaction of terminal alkynes under aerobic conditions

An efficient method for palladium-catalyzed homocoupling reaction of terminal alkynes in the synthesis of symmetric diynes is presented. The results showed that both Pd(OAc)(2) and CuI played crucial roles in the reaction. In the presence of 2 mol % Pd(OAc)(2), 2 mol % CuI, 3 equiv of Dabco, and air, homocoupling of various terminal alkynes afforded the corresponding symmetrical diynes in moderate to excellent yields, whereas low yields were obtained without either Pd(OAc)(2) or CuI. Moreover, high TONs (turnover numbers; up to 940 000 for the reaction of phenylacetylene) for the homocoupling reaction were observed. Under similar reaction conditions, cross-coupling of 1-iodo-4-nitrobenzene with phenylacetylene was also carried out smoothly in quantitative yield. However, the presence of CuI disfavored the palladium-catalyzed Sonogashira cross-coupling reactions of the less active aryl iodides and bromides. In the presence of 0.01-2 mol % Pd(OAc)(2), a number of aryl iodides and bromides were coupled with terminal alkynes in good to excellent yields. It is noteworthy that this protocol employs mild, efficient, aerobic, copper-free, and ligand-free conditions.     

Anti-Markovnikov hydroalkylation of allylic amine derivatives via a palladium-catalyzed reductive cross-coupling reaction

Palladium-catalyzed hydroalkylation of allylic amine derivatives by alkylzinc reagents is reported. This reductive cross-coupling reaction yields anti-Markovnikov products using a variety of allylic amine protecting groups. Preliminary mechanistic studies suggest that a reversible β-hydride elimination/hydride insertion process furnishes the primary Pd-alkyl intermediate, which then undergoes transmetalation followed by reductive elimination to form a new sp(3)-sp(3) carbon-carbon bond.     

Cationic palladium-catalyzed hydrosilylative cross-coupling of alkynes with alkenes

A cationic palladium complex-catalyzed cross-coupling of alkynes with alkenes is presented, which occurs selectively under the hydrosilylation conditions using trichlorosilane. The unique reaction might be well understood in terms of an initial hydropalladation of a given 1-alkyne to form regioselectively a 1-alkenylpalladium species, which, in turn, undergoes easily and specifically an alkene insertion. The resulting homoallylic organopalladium species terminates one catalytic cycle by substituting the palladium center with a trichlorosilyl group to give product(s).     

Simultaneous reduction of nitro- to amino-group in the palladium-catalyzed Suzuki cross-coupling reaction

An efficient method for palladium-catalyzed Suzuki cross-coupling reaction with simultaneous reduction of nitro- to amino-group has been developed. This method allows nitro-substituted aryl halides to readily react with arylboronic acids, to afford aryl substituted aniline in low to excellent yields. The reaction was catalyzed by Pd(OAc)₂ (3 mol %) at 150 °C under atmospheric pressure in the presence of K₂CO₃ (3 equiv) in DMF/H₂O (5/1).     

Boron trifluoride promoted reactions of n-haloelectrophiles with alkenes

N-Haloelectrophiles react with alkenes in the presence of boron rifluoride etherate to give halofluorides and N-halo adducts.     

A palladium-catalyzed three-component cross-coupling of conjugated dienes or terminal alkenes with vinyl triflates and boronic acids

A three-component coupling of vinyl triflates and boronic acids to alkenes catalyzed by palladium is reported. Using 1,3-dienes, selective 1,2-alkene difunction-alization is observed, whereas the use of terminal alkenes results in 1,1-alkene difunctionalization. The reaction outcome is attributed to the formation of stabilized, cationic Pd-π-allyl intermediates to regulate β-hydride elimination.     

Boron trifluoride facilitated transesterification of dioxaborolanes

The direct transesterification of dioxaborolanes (alkane-1,2-diol based boronate esters) was explored. Using BF₃·OEt₂, alkane-1,2-diol based mono- and bis-boronate esters (i.e., pinacol and ethylene glycol) have been converted quantitatively to either benzene-1,2-diol or alkane-1,3-diol based boronate esters. In the case of pinacol esters, esterification is facilitated by the accompanying pinacol rearrangement, thus shifting the reaction equilibrium.     

Regioselective palladium-catalyzed direct cross-coupling of coumarins with simple arenes

An efficient method for the C4-regiocontrolled C-H functionalization of coumarins to enable facile oxidative cross-couplings with simple arene components is disclosed.