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Trans-2,3-bis-(diphenylphosphinomethyl)-norbornene-(5), trans-2,3-bis-(diphenylphosphinomethyl)-7-oxanorbornane, and (-)-/2((S)-1-dimethylaminoethyl)phenyl/-diphenylphosphine have been used as ligands for the nickel and palladium catalyzed asymmetric Grignard cross-coupling reaction giving the coupling product (E)-1,3-diphenyl-1-butene.Chemical yields from 60 to 95percent and optical yields up to 40percent were obtained, depending on the types of ligand coordinated.

The catalytic enantioselective synthesis of α-chiral olefins represents a valuable strategy for rapid generation of structural diversity in divergent syntheses of complex targets. Herein, we report a protocol for the dual CuH- and Pd-catalyzed asymmetric Markovnikov hydroalkenylation of vinyl arenes and the anti-Markovnikov hydroalkenylation of unactivated olefins, in which readily available enol triflates can be utilized as alkenyl coupling partners. This method allowed for the synthesis of diverse α-chiral olefins, including tri- and tetrasubstituted olefin products, which are challenging to prepare by existing approaches.

A nickel-catalyzed cross-coupling of allylic alkyl ethers with organoboron compounds through the cleavage of the inert C(sp3)-O(alkyl) bonds is described. Several types of allylic alkyl ethers can be coupled with various boronic acids or their derivatives to give the corresponding products in good to excellent yields with wide functional group tolerance and excellent regioselectivity. The gram-scale reaction and late-stage modification of biologically active compounds further prove the practicality of this synthetic method.

The invention discloses a synthesis method of a triphenylphosphine allyl palladium halide compound and a derivative thereof. The synthesis method comprises the step of carrying out one-step reaction on a mixture containing a palladium salt, a halogenated allyl compound and a trisubstituted phosphine compound to obtain the triphenylphosphine allyl palladium halide compound and the derivative thereof. The method is low in cost, high in efficiency, easy to operate and high in safety. The prepared triphenylphosphine allyl palladium halide compound and the derivative thereof can be widely applied as catalysts to catalytic cross coupling or homogeneous coupling reactions of various types of organic substrates so as to prepare various organic reaction intermediates.

A in situ ring-closing strategy was developed for the synthesis of N-heterocyclic carbene nickel complexes. The process was carried out in air, and did not require solvent purification. The resulting nickel complexes were investigated as catalysts for the coupling of allylic alcohols with aryl boronic acids. A wide range of allylic substrates and aryl acids proved to be applicable to this catalytic system. Control experiments suggest that the Ni(0) may be the true active species in the coupling reactions. (Figure presented.).

The nickel-catalyzed hydroarylation of 1,3-dienes with arylboronic acids using a secondary homoallyl carbonate as a surrogate for the 1,3-diene and hydride source has been developed. The synthetic strategy allowed an efficient access to a wide array of hydroarylation products in high yields with high functional group compatibility without the use of an external hydride source. Mechanistic experiments indicated that the alkene-directed oxidative addition and subsequent β-hydride elimination would be a critical process in this transformation.

Traditional cross-coupling reactions show some disadvantages like the use of organohalides or the production of stoichiometric amounts of waste. The dehydrative homo- or heterocoupling of alcohols therefore arises as an interesting approach for a highly atom-economical formation of carbon–carbon bonds, since water is produced as the only by-product. We herein report a simple and direct, metal-free protocol for the synthesis of olefins by applying catalytic amounts of a sulfonic acid and triphenylphosphane under air. A variety of olefins could be synthesized from benzylic alcohols under relatively mild conditions. Additionally, dehydrative hydroarylation of benzylic alcohols with electron-rich arenes was possible by using only Br?nsted acid under otherwise same reaction conditions. We could show that phosphane additives are essential to overcome oligomerization as main side reaction by the occupancy of the reactive carbocation intermediate.

The use of silver trifluoromethanesulfonate (silver triflate, AgOTf) as a halide abstraction reagent is pervasive in organometallic chemistry. However, recent reports suggest a “hidden” Br?nsted acid lurks within it that may catalyze purported metal-based catalysis. Presented herein are new reactions that are either catalyzed or promoted by the “hidden” acid, generated upon silver triflate degradation. 1-Phenylethanol dehydrates to styrene (1) upon reaction with AgOTf at 90 °C over 24 h, which slowly coverts to the vinyl hydrovinylation product (E)-1,3-diphenyl-1-butene, (2, 64%) over several days. While dehydration was observed with a number of benzylic alcohols to yield Zaitsev selective olefins, only 1-phenylethanol affords vinyl hydrovinylation products. Dehydration was not observed for primary and secondary alcohols, suggesting an acid catalyzed E1elimination reaction mechanism is at play. The degradation of silver triflate was found to be the source of the “hidden” Br?nsted acid, which demonstrated a dependence on the presence of light and oxygen. In the absence of light and oxygen, dehydration of 1-phenylethanol was severely stunted and 2 is not formed, but instead the ether product, oxy-bis(ethane-1,1-diyl)dibenzene (3), is afforded. The mesitylene internal standard also reacts with the in situ formed styrene to produce 2-(1-phenylethyl)mesitylene (4) through acid catalyzed electrophilic aromatic substitution. These reactions were monitored (products characterized) by GC-MS and/or 1H NMR spectroscopic methods. We present herein the details of these reactions and our characterization methods.

The direct coupling of allylic alcohols with arylboronic acids or their derivatives catalyzed by Ni(cod)2 in the presence of a catalytic amount of base has been developed. A wide variety of allylic substrates or arylboronic acids turned out to be applicable to this catalytic system. The present method does not require the use of ligands for stabilizing the nickel catalyst in most cases or additional activators for activation of allylic alcohols.

This perspective showcases our development of benzylic and allylic amine and alcohol derivatives as electrophiles for stereospecific, nickel-catalyzed cross-coupling reactions, as well as the prior art that inspired our efforts. The success of our effort

Cationic acetylacetonate bis(secondary amine) palladium (II) complexes were synthesized by nitrile substitution of [Pd(acac)(MeCN)2][BF4] with L (L?=?morpholine, diethylamine, dibutylamine, dioctylamine) which yielded [Pd(acac)(L)2][BF4] as a mononuclear species with chelating acac ligand. An X-ray diffraction, NMR, IR and DFT study of [Pd(acac){morpholine}2][BF4] establishes the presence of hydrogen bonding between the morpholine ligand and [BF4]? anion. Crystallographic defects in the crystal and presence of pseudocrystalline structure in solution of [Pd(acac){morpholine}2][BF4] were assumed to explain IR spectra features. Preliminary investigations into the polymerization of norbornene, dimerization of styrene, and telomerization of 1,3-butadiene with diethylamine were performed.

Using triphenylmethylium tetrakis(pentafluorophenyl)borate as a convenient Br?nsted acid precatalyst, β-(α,α-dimethylbenzyl)styrenes are shown to cyclize efficiently to afford a variety of new indanes that possess a benzylic quaternary center. The geminal dimethyl-containing quaternary center is proposed to be necessary to arm the substrate for cyclization through steric biasing.

A silver catalyzed decarboxylative C(sp2)-C(sp3) coupling of vinylic carboxylic acids with alcohols, alkylbenzenes, cycloalkanes and cyclic ethers was developed by using DTBP as an oxidant. This reaction tolerates a wide range of substrates, and products are obtained in good to excellent yields. The reaction also shows good stereoselectivity, and only trans-isomers are obtained. In addition, a radical pathway would be involved to facilitate this decarboxylative C(sp2)-C(sp3) coupling reaction.

A simple and operationally easy protocol for the regioselective synthesis of internal alkenes through a dehydrative cross-coupling and direct coupling procedure has been described using the environmentally benign Ca(II) catalyst. Several alkenes and alcohols underwent the coupling reaction under solvent-free conditions in a short time to produce the desired alkenes. This method is further extended to show the application in the synthesis of novel benzopyran molecules through a cascade strategy.

A convenient and efficient TfOH-catalyzed head-to-tail dimerization of vinylarenes has been realized under mild conditions. The present protocol provides an attractive approach to a diverse range of higher olefins in good to excellent yields.

Br?nsted acid Tf2NH alone catalyzed Friedel-Crafts-type hydroarylation and head-to-tail hydroalkenylation of vinylarenes under mild reaction conditions have been realized, providing a readily scalable, metal-free, and practical access to the 1,1-diarylalkane scaffolds and trans-1,3-diaryl-1-butenes in high yields and excellent regioselectivities.

A convenient and efficient iodine-mediated head-to-tail dimerization of styrenes to produce the corresponding dimers in the presence of triethyl phosphite is reported. The advantages of the present protocol are metal-free conditions, short reaction time, simplicity, and high efficiency.

Combining high-throughput experimentation with conventional experiments expedited discovery of new first-row nickel catalysts for the dehydrative decarbonylation of the bioderived substrates hydrocinnamic acid and fatty acids to their corresponding alkenes. Conventional experiments using a continuous distillation process (180 °C) revealed that catalysts composed of NiII or Ni0 precursors (NiI2, Ni(PPh3)4) and simple aryl phosphine ligands were the most active. In the reactions with fatty acids, the nature of the added phosphine influenced the selectivity for α-alkene, which reached a maximum value of 94%. Mechanistic studies of the hydrocinnamic reaction using Ni(PPh3)4 as catalyst implicate a facile first turnover to produce styrene at room temperature, but deactivation of the Ni(0) catalyst by CO poisoning occurs subsequently, as evidenced by the formation of Ni(CO)(PPh3)3, which was isolated and structurally characterized. Styrene dimerization is a major side reaction. Analysis of the reaction mechanism using density functional theory supported catalyst regeneration along with alkene formation as the most energetically demanding reaction steps.

A simple and practical denitrated coupling reaction of nitroalkenes with various alkenes using a nickel catalyst and triethoxysilane [(EtO)3SiH] as reducing agent was achieved. Under mild reaction conditions, both aliphatic and aromatic alkenes could react with nitroalkenes to obtain a series of olefins with different functional groups in satisfactory yields under an air atmosphere, which were previously difficult or impossible to access. (Figure presented.).

We herein report a transition-metal-free cross-coupling between secondary alkyl halides/mesylates and aryl/alkenylboronic acid, providing expedited access to a series of nonchiral/chiral coupling products in moderate to good yields. Stereospecific SN2-type coupling is developed for the first time with alkenylboronic acids as pure nucleophiles, offering an attractive alternative to the stereospecific transition-metal-catalyzed C(sp2)-C(sp3) cross-coupling.

In the presence of Snβ zeolite, vinylarenes undergo the highly chemo- and regioselective head-to-tail heterodimerization with 1,1-diphenylethene to form the corresponding alkenes in good to excellent yields. The scope of the reaction was explored by various vinylarenes with 1,1-diphenylethene. However, the substrates with strong electron-withdrawing groups failed to react with 1,1-diphenylethene under the present catalytic conditions. Moreover, the Snβ zeolite is recyclable and can be reused without significant loss in its catalytic activity.

Allylic arylation of allylic acetates by sodium tetraarylborates in the presence of ppb to ppm (molar) loadings of a palladium NNC-pincer complex catalyst in methanol at 50°C gave the corresponding arylated products in excellent yields. Total turnover numbers of up to 500 000 000 and turnover frequencies of up to 11 250 000 h-1 were achieved.

[Pd(acac)(MeCN)2]BF4 has been observed to catalyze selective substituted styrene dimerization and addition norbornene polymerization. Theoretical calculations based on BP86 density functional theory have been carried out to clarify the precatalyst activation mechanism.

Iron-catalyzed Heck coupling of benzyl chlorides and styrenes proceeds under photochemical conditions using the well-known anionic complex, [FeCp(CO)2]- (Fp-), as a catalyst. The reaction likely proceeds through the established SN2 mechanism for Fp- alkylation, followed by styrene migratory insertion and β-hydride elimination steps that are enabled by photochemical CO dissociation.

A novel strategy has been identified for the regioselective synthesis of 3,4-disubstituted quinolines and 2,3,5-trisubstituted pyrroles from simple alkenes via anti-Markovnikov selectivity under palladium catalysis. The salient features are synthesis of two different heterocycles, readily available starting materials, broad substrate scope, moderate to good yields and use of molecular oxygen as a terminal oxidant.

A new method for the preparation of allylic alcohol derivatives has been developed via a radical mechanism using DTBP as the radical initiator promoted by copper salt. The C(sp3)-H bond in various alcohols, toluene derivatives, and alkanes were successfully converted into C-C bonds to yield the desired products in moderate to good yields.

An atom-economic and efficient non-precious metal-catalyzed esterification of benzyl C-H bonds has been developed. A variety of α-keto benzyl esters have been accessed in good yields through the reactions between benzyl derivatives and benzoylformic acids using iron trifluoride as a catalyst in the presence of di-tert-butyl peroxide under an inert atmosphere. This strategy provides a straightforward access to linearly expanded α-keto benzyl esters. A plausible reaction mechanism is proposed.

Visible-light-controlled polymerization was achieved by a bichromophoric organopalladium catalyst which possesses a naphthyl-substituted cyclometallated Ir(iii) light-absorbing moiety. The complex was highly active toward styrene polymerization upon visible-light irradiation, and its photoactivity toward polymerization and dimerization was switchable. On the basis of the switching activity, controlled copolymerization of styrene and vinyl ether was achieved upon photo-irradiation to give the corresponding copolymers. This journal is

A practical and greener process for the allyl-aryl coupling of allylic carbonates with arylboronic acids catalyzed by in situ generated palladium nanoparticles (PdNPs) in ionic liquid (IL) has been described. The PdNPs showed high catalytic activity for the coupling reaction in the IL to afford allyl-aryl coupling products in good to high yields with complete regio- and E/Z selectivities. The PdNPs were readily immobilized in the IL phase and the catalyst can be reused several times without significant loss of catalytic activity and stereospecificity.

A direct synthesis of polysubstituted olefins via construction of C-C bonds, which involves the direct dehydrative coupling of alcohols or alkenes with alcohols, was realized using a series of alkanesulfonic acid group-functionalized ionic liquids (SO3H-functionlization ILs) without additives. The metal-free and recyclable catalyst system avoided the disposal and neutralization of acidic catalysts after reaction and tolerated a broad range of substrates, including benzylic, allyl, propargylic, aliphatic and aromatic or aliphatic olefins. Additionally, the catalytic system was suitable for a gram-scale preparation. Preliminary mechanistic studies indicated that the C-H bond cleavage in this reaction might be involved in the rate-determining step.

Iron-catalyzed alkylation of internal olefins, that is, α-oxo ketene dithioacetals, was successfully realized by using styrenes as the alkylating reagents. Highly functionalized tetrasubstituted olefins were prepared in moderate to high yields. the Partner Organisations 2014.

A highly efficient head-to-tail dimerization of a styrene was developed using a cationic palladium(II)-catalyzed selective C-C bond forming reaction. The complex [AllylPd(PPh3)]+OTf-, which is believed to generate 'palladium hydride' (Pd-H), catalyzed the dimerization of various styrenes in excellent yields as single isomers. This Pd(II)-catalyzed reaction provides a new economical C-C bond forming method. Copyright

The high catalytic activity and selectivity of zeolites HBeta and HZSM-12 were found in the synthesis of (E)-4-phenyl-3-buten-2-one by the reaction of styrene with acetic anhydride.

An original syn: The first enantioselective Suzuki-Miyaura cross-coupling of chiral, enantioenriched secondary allylic boronic esters is described (see scheme; DME=dimethoxyethane, Bpin = pinacolboryl, dba = dibenzylideneacetone). Mechanistic studies show that the reactions proceed via γ-selective transmetalation followed by reductive elimination. The reaction provides the first independent confirmation that the transmetalation of boronic esters proceeds via a syn pathway. Copyright

Metalloenzymes are essential proteins with vital activity that promote high-efficiency enzymatic reactions. To ensure catalytic activity, stability, and reusability for safe, nontoxic, sustainable chemistry, and green organic synthesis, it is important to develop metalloenzyme-inspired polymer-supported metal catalysts. Here, we present a highly active, reusable, self-assembled catalyst of poly(imidazole-acrylamide) and palladium species inspired by metalloenzymes and apply our convolution methodology to the preparation of polymeric metal catalysts. Thus, a metalloenzyme-inspired polymeric imidazole Pd catalyst (MEPI-Pd) was readily prepared by the coordinative convolution of (NH4)2PdCl4 and poly[(N-vinylimidazole)-co-(N- isopropylacrylamide)5] in a methanol-water solution at 80 °C for 30 min. SEM observation revealed that MEPI-Pd has a globular-aggregated, self-assembled structure. TEM observation and XPS and EDX analyses indicated that PdCl2 and Pd(0) nanoparticles were uniformly dispersed in MEPI-Pd. MEPI-Pd was utilized for the allylic arylation/alkenylation/vinylation of allylic esters and carbonates with aryl/alkenylboronic acids, vinylboronic acid esters, and tetraaryl borates. Even 0.8-40 mol ppm Pd of MEPI-Pd efficiently promoted allylic arylation/alkenylation/vinylation in alcohol and/or water with a catalytic turnover number (TON) of 20 000-1 250 000. Furthermore, MEPI-Pd efficiently promoted the Suzuki-Miyaura reaction of a variety of inactivated aryl chlorides as well as aryl bromides and iodides in water with a TON of up to 3 570 000. MEPI-Pd was reused for the allylic arylation and Suzuki-Miyaura reaction of an aryl chloride without loss of catalytic activity.

A novel rhodium-catalyzed allylic substitution reaction using indium organometallics is reported. Aryl- and heteroarylindium reagents reacted in THF at 80 °C with primary and secondary allyl halides and their derivatives under rhodium(I) catalysis to afford the α-substituted products in good yields and with high regio- and stereoselectivity. The reaction takes place with substoichiometric amounts of the triorganoindium reagents, which demonstrates the efficiency of the indium-rhodium transmetallation process in carbon-carbon bond-forming reactions. Copyright

A general protocol for the coupling of haloarenes with a variety of allylic acetates is presented. Strengths of the method are a tolerance for electrophilic (ketone, aldehyde) and acidic (sulfonamide, trifluoroacetamide) substrates and the ability to couple with a variety of substituted allylic acetates. Secondary alkyl bromides can also be allylated under slightly modified conditions, demonstrating the generality of the approach. Finally, the coupling of a reactive vinyl halide could be achieved by the use of a very hindered ligand and more reactive, branched allylic acetates.

An efficient cross-coupling reaction of N-allylic sulfonimides with organozinc reagents has been developed. In the presence of 1 mol-% of Pd 2(dba)3, a range of N-allylic sulfonimides smoothly couple with various organozinc reagents at room temperature to give the corresponding (E)-alkene products in moderate to excellent yields and with good to exclusive α-selectivity. It is noteworthy that allyl ether, benzyl ether, and ester are tolerated under the reaction conditions. A range of N-allylic sulfonimides smoothly couple with various organozinc reagents in the presence of 1 mol-% of Pd2(dba)3 at room temperature to give the corresponding (E)-alkene products in moderate to excellent yields and with good to exclusive α-selectivity.

The Pd(0)-catalyzed allylic cross-coupling of homoallylic tosylate substrates using boronic acids and pinacol esters is reported. The reaction uses 2-(4,5-dihydro-2-oxazolyl)quinoline (quinox) as a ligand and is performed at ambient temperature. The scope of the reaction is broad in terms of both the boronate transmetalating reagent and the substrate and includes secondary tosylates. Mechanistic studies support an alkene-mediated SN2-type stereoinvertive oxidative addition of unactivated primary and secondary alkyl tosylates.

The NH2 group serves as an effective leaving group in the palladium-catalyzed regioselective and stereospecific title reaction (see scheme). The reaction works well with aryl- and alkenylboronic acids and aryl-, alkenyl-, allyl-, and benzylboronates, and complete transfer of chirality has been achieved when using α-chiral primary allylic amines as the allylic electrophiles. Copyright

The Pd-catalyzed Suzuki-Miyaura coupling reaction of unsymmetric 1,3-disubstituted secondary allylic carbonates with arylboronic acids has been developed in a wet solvent under a base-free system to afford allyl-aryl coupling products in a high level of isolated yields with complete regio- and E/Z-selectivities with good to excellent chemoselectivities. The coupling reaction of optically active allyl carbonates gave allyl-aryl coupling products with excellent enantioselectivities with inversion of the stereochemistry. This coupling method was successfully applied to the synthesis of (S)-naproxen.

Gobs of globules: A polymeric imidazole/acrylamide palladium catalyst, MPPI-Pd (M=PdIICl and Pd0), was utilized for the allylic arylation/alkenylation of allylic esters with aryl/alkenylboronic acids and tetraaryl borates. Low catalyst loadings efficiently promoted the reaction with a catalytic turnover number of 20000-1250000. The catalyst can be reused without loss of catalytic activity.

Pd(acac)2 catalyzed dimerization of vinylarenes to form dimers under mild condition with excellent yields and stereoselectivities. In particular, the use of TFA highly promoted the activity and selectivity of the dimerization. The studies on mechanism for the reaction displayed clearly that the dimerization of styrenes is 100% atom economic reaction.

Cross combination: The olefinic C-H bond in 1,1-diarylethenes selectively adds to the C=C double bond of substituted styrenes in a head-to-tail fashion under In(OTf)3 (OTf=triflate) catalysis (see scheme) while homo- and cyclodimerization reactions are suppressed. The high chemo- and regioselectivity of this intermolecular hydroalkenylation originates from the high stability and steric bulk of the diaryl-substituted tertiary carbocation intermediate. Copyright

Two new chiral, enantiomerically pure, hybrid P-N ligands, namely (2R,5S)-2- phenyl-3-(2-pyridyl)-1,3-diaza-2-phosphanicyclo[3,3,0]octan-4-one (1) and (2R,5S)-2-phenyl-3-(2-pyridyl)-1,3-diaza-2-phosphanicyclo[3,3,0]octane (2), have been synthesized starting from L-proline. The two ligands differ in the presence or not of a carbonyl group in the diazaphosphane ring. Their coordination chemistry towards Pd(II) was studied by reacting them with [Pd(CH3)Cl(cod)]. A different behaviour was observed: ligand 2 shows the expected bidentate chelating behaviour leading to the mononuclear Pd-complex, while ligand 1 acts as a terdentate ligand giving a dinuclear species. The corresponding cationic derivatives were obtained from the palladium neutral complexes, both as mono- and dinuclear derivatives, and tested as precatalysts for styrene dimerization, yielding E-1,3- diphenyl-1-butene regio- and stereoselectively as the sole product. A detailed analysis of the catalytic behaviour is reported.

Selective dimerization of styrene to 1,3-diphenylbutene-1 in the presence of [(acac)Pd(PAr3)2]BF4 + BF 3OEt2 catalytic systems, where R = C6H 5, o-CH3C6H4, p-CH3C 6H4, or o-CH3OC6H4, has been studied. Under the optimal conditions (B/Pd = 8, T = 75°C, R = C 6H5), the conversion of styrene to the products exceeds the conversion for the known analogs and reaches 1.5 tons of styrene/g-atom of palladium with amounts of dimers and trimers of 91 and 9%, respectively. The dimers consist of up to 100% 1,3-diphenylbutene-1 with a trans/cis isomer ratio of 95/5.

Chemical equations presented. An efficient Fe(III)-catalyzed direct coupling of alkenes with alcohols and cross-coupling of alcohols with alcohols to give the corresponding substituted (E)-alkenes stereospecifically is demonstrated. Additionally, this reaction could be scaled up. The kinetic isotope effect (KIE) experiments indicated a typical secondary isotope effect in this process. Although benzylic alcohols were effective substrates, mild conditions, atom efficiency, environmental soundness, and stereospecificity are features that make this procedure very attractive.

A novel and efficient trifluoromethanesulfonic acid-catalyzed sp 3-sp2 Ci￡C bond formation reaction through the direct coupling of alcohols with alkenes has been realized under mild conditions. The present protocol provides an attractive approach to a diverse range of polysubstituted olefins in good to excellent yields with high stereo- and regioselectivities. Copyright

Regiocontrol of allylic alkylation reactions involving hard nucleophiles remains a significant challenge and continues to be an active area of research. The lack of general methods in which α-alkylation is favored underscores the need for the development of new processes for achieving this type of selectivity. We report that Cu(I) catalyzes the allylic substitution of phosphorothioate esters with excellent α-regioselectivity, regardless of the nature of the Grignard reagent that is used. To the best of our knowledge, the Cu-catalyzed allylic alkylation of phosphorothioate esters has never been described. We have also developed a simple protocol for inducing high α selectivity starting from secondary allylic halides. This is accomplished by using sodium phosphorothioates as an additive.

Ruthenium complexes catalyze the decomposition of vinyl acetate releasing the acetic acid and its subsequent addition to linear and cyclic olefins.

Organic-solvent-free cross-couplings between benzylic and alkenyl halides have been developed. Various alkenyl halides can be efficiently benzylated by combining the precursor halides in the presence of Zn dust and a Pd catalyst at room temperature, in water as the only medium.