Volume 80, Issue 5

The 14th IUPAC International Symposium on Organometallic Chemistry Directed Towards Organic Synthesis (OMCOS-14) was held in Nara, Japan, 2-6 August 2007, under the auspices of IUPAC, and with cosponsorship of the Science Council of Japan and the Chemical Society of Japan. OMCOS-14 was held at Nara Centennial Hall, surrounded by National Treasures including eight World Heritage assets. This symposium is a continuation of the successful series of OMCOS meetings, previously held at Geneva (2005), Toronto (2003), Taipei (2001), Versailles (1999), Göttingen (1997), Santa Barbara (1995), Kobe (1993), Utrecht (1991), Florence (1989), Vancouver (1987), Kyoto (1985), Dijon (1983), and Fort Collins (1981). The event once again brought together industrial and academic chemists from all over the world to discuss the latest advances in new metal-mediated and -catalyzed reactions, mechanistic insights into important reactions, new preparations and applications of organometallic reagents, as well as ingenious methods for the synthesis of pharmaceuticals, agrochemicals, and materials using metals. Almost 1000 participants attended from 34 countries, one-third of them from abroad. Particularly strong representation from Asian countries such as China, Taiwan, and Korea underscores the remarkable growth of interest and development in organometallic research in these countries. The scientific program of OMCOS-14 featured 6 plenary lectures, 20 invited lectures, 28 short oral presentations, and one OMCOS Award lecture. The lectures were uniformly outstanding and held the attention of an audience fascinated by the excellent chemistry. One sensed that the warmth of the weather was matched by the warm enthusiasm that prevailed at the venue throughout the meeting. Themes that attracted attention included metal-catalyzed direct functionalization of alkenes, alkynes, and arenes, environmentally benign processes and gold-catalyzed reactions. In a particular highlight, Prof. F. Dean Toste from the University of California, Berkeley received the OMCOS-14 Award (sponsored by the Yen Chuang Foundation and Springer Verlag) for his glorious research on gold-catalyzed reactions. The scientific program also presented well-supported poster sessions comprising 546 posters of remarkably high quality. On the basis of assessments by distinguished juries, 27 posters were selected for awards of OMCOS-14 Poster Prizes, two of which included free registration for students to participate in the 23rd International Conference on Organometallic Chemistry (ICOMC-2008, co-chaired by Profs. Dixneuf and Bruneau at Rennes, France, 13ñ18 July 2008). This issue of Pure and Applied Chemistry comprises a collection of 40 papers based upon lectures delivered at OMCOS-14. It therefore offers readers an enduring and representative record of the great achievements announced during the symposium. The series continues with OMCOS-15, which will be held in Glasgow, UK (<http://www.omcos15.com/>), 26-30 July 2009, under the chairmanship of Prof. Pavel Kočovský. Koichiro Oshima Conference Chairman

An enantioselective synthesis of cyclic and acyclic β-aryl ketone and aldehydes via Pd(II)-catalyzed 1,4-addition of Ar- m [ m = B(OH) 2 , BF 3 K, Si(OMe) 3 , SiF 3 , BiAr 2 ] to α,β-unsaturated ketones or aldehydes is described. The catalytic cycle involves transmetallation between Ar- m and Pd complexes as a key process, the mechanism of which is discussed on the basis of characterization of the transmetallation intermediate and electronic effect of the substituents. The enantioselection mechanism and efficiency of a chiraphos ligand for structurally planar α,β-unsaturated ketones are discussed on the basis of the X-ray structure of the catalyst and results of density functional theory (DFT) computational studies on the model of coordination of the substrates to the phenylpalladium(II)/( S , S )-chiraphos intermediate.

The first helical double-stranded polymer by ring-opening metathesis polymerization (ROMP) of a bisnorbornene derivative and the replication of a single-stranded polynorbornene leading to its complementary polynorbornene derivative are described. Base-promoted hydrolysis of this polymer affords the corresponding single-stranded polymer and the linker, ferrocene-1,1'-dicarboxylic acid, in excellent yield. Three forms (helical, supercoil, and ladder) of the polymer have been observed by scanning tunneling microscopy (STM) and simulated by molecular mechanical and dynamical calculations. The polymer thus obtained has a structural resemblance to DNA by having similar width, number of monomeric units per pitch, five-membered rings in the polymeric frame, perpendicular linkers to the backbones, and similar spacing between neighboring monomeric units. In the replication study, the single-stranded polynorbornene acts as a template for norbornene monomer adhesion via ester linkage. This polymer is treated with Grubbs-I catalyst to proceed the ROMP to afford the corresponding unsymmetric double-stranded polymer. After hydrolysis, a complementary polynorbornenecarboxylic acid is produced. This approach may provide a versatile entry for the design, synthesis, and physicochemical investigations of new types of polymers for simulation of biological systems as well as materials applications.

Water has attracted significant attention as an alternative solvent for transition-metal-catalyzed reactions. The use of water as solvent allows simplified procedures for separation of the catalyst from the products and recycling of the catalyst. Water is an inexpensive reagent for the formation of oxygen-containing products such as alcohols. The use of water as a medium for promoting organometallic and organic reactions is also of great potential. This chapter will focus on old and recent developments in the design and applications of some catalytic reactions using aqueous-phase Pd, Rh, Pt, and Au complexes.

An In(III)/Si catalyst system effects the direct allyl substitution of alcohols and silyl ethers under mild conditions. A deoxygenation of alcohols is also promoted by InCl 3 catalyst. This method requires no pretreatment or protection of hydroxy groups or deprotection of siloxy groups. The completion of the catalytic allylation depends on the low oxophilicity and high halophilicity of In(III) halide species, and other representative Lewis acids such as AlCl 3 and BF 3 have no catalytic activity for the allylations. The oxophilicity and halophilicity are also demonstrated by NMR studies.

Inspired by the principle of DNA base-pairing, a new concept for the self-assembly of molecular catalysts is described herein. Thus, employing A-T analogous complementary hydrogen-bonding templates, self-assembly of monodentate to bidentate ligands in the coordination sphere of a transition-metal salt occurs to give defined self-assembly catalysts. This approach is intrinsically combinatorial and allows the facile generation of defined catalyst libraries through simple component mixing. From the study of these ligand libraries, excellent catalysts for linear-selective hydroformylation, asymmetric hydrogenation, and anti -Markovnikov hydration of terminal alkynes have emerged.

Recent developments in the chemistry of η 3 -allylruthenium(IV) complexes are due to their straightforward synthesis resulting from oxidative addition of allylic substrates to a ruthenium(II) center. Subsequent reaction with a nucleophile is the basis of their involvement in the catalytic allylic substitution reaction. We focus here on ruthenium-catalyzed substitution of allylic substrates by C -, N -, and O -nucleophiles and show that selected ligands make regio- and enantioselective reactions possible.

The catalytic activity of a wide range of copper salts, including Cu(I) and Cu(II), has been examined in the Cu-catalyzed three-component coupling reactions of sulfonyl azides, terminal alkynes, and amines, alcohols, or water to afford N -sulfonyl amidines, imidates, and amides, respectively. Furthermore, the investigation on the ligand effect in our protocol has revealed that certain types of ligands such as tris(benzyltriazolylmethyl)amine (TBTA) exhibited notable acceleration effects on the coupling reaction. The facile and efficient methods for removing copper salts from reaction mixture were also examined.

Chiral bidentate hemi-labile bis(phosphine) monoxide ligands were shown to be quite effective in various copper-catalyzed transformations. Among them, the nucleophilic addition to imines, the conjugate addition to α,β-unsaturated nitro derivatives, and the conjugate reduction of α,β-unsaturated sulfones generally gave good to excellent yields and high enantiomeric excesses.

The Reformatsky reaction is a venerable named reaction that was introduced more than 120 years ago. Diastereoselective variants based on the use of chiral auxiliary and enantioselective protocols, based on the employment of stoichiometric amount of chiral ligands, have been successfully applied in organic synthesis during the years. However, a facile and general catalytic enantioselective variant was still a difficult task. Recently, we have established a new general and straightforward methodology for catalytic enantioselective Reformatsky reaction based on different concepts. In this paper, we present our general finding in catalytic enantioselective Reformatsky reaction of ketones, imines, and aldehydes. Our simple methodologies could become benchmark reactions for testing new synthesized chiral ligands for asymmetric transformations.

A study of the Pauson-Khand reaction (PKR) based on Co 2 (CO) 8 and binap has revealed that a key precatalyst is (binap)Co 2 (CO) 6 , and that alkynes add to this species to generate isomers that interconvert under typical PKR conditions. A 31 P NMR study of (binap)( N -(prop-2-enyl)- N -(prop-2-ynyl)- p -toluenesulfonamide)Co 2 (CO) 4 revealed that heating this species gives rise to an unexpected cobalt hydride species (binap)Co(CO) 2 H together with (binap)Co 2 (CO) 6 . Observation of a PKR reaction by 31 P NMR spectroscopy revealed that the hydride species is generated during the course of the reaction.

Stereocontrolled additions of allylic metal reagents to carbonyl compounds constitute one of the most useful classes of transformations in organic synthesis. The recent development of Lewis and Brønsted acid-catalyzed manifolds for the allylboration of carbonyl compounds has opened doors toward an ideal carbonyl allylation methodology using stable and nontoxic allylic boronates as reagents. This paper describes the development of acid-catalyzed allylborations, mechanistic investigations of these new processes, and ongoing efforts toward general catalytic enantioselective allylboration methodologies. The preparation of optically enriched α-substituted allylic boronate reagents is discussed, as well as their applications in Lewis acid-catalyzed additions to afford skeletally diverse products like propionate units, polysubstituted furans, vinylcyclopropanes, and larger ring systems.

Several reactions of simple, unactivated alkenes with electrophiles under Ni(0) catalysis are discussed. The coupling of olefins with aldehydes and silyl triflates provides allylic or homoallylic alcohol derivatives, depending on the supporting ligands and, to a lesser extent, the substrates employed. Reaction of alkenes with isocyanates yields N -alkyl acrylamides. In these methods, alkenes act as the functional equivalents of alkenyl- and allylmetal reagents.

This account reviews C-C bond formation reactions using alkyl fluorides mostly focusing on the transition-metal-catalyzed reactions. These reactions proceed efficiently under mild conditions by the combined use of Grignard reagents and transition-metal catalysts, such as Ni, Cu, and Zr. It is proposed that ate complex intermediates formed by the reaction of these transition metals with Grignard reagents play important roles as the active catalytic species. Organoaluminun reagents react directly with alkyl fluorides in nonpolar solvents at room temperature to form C-C bonds. These studies demonstrate the practical usefulness of alkyl fluorides in C-C bond formation reactions and provide a promising method for the construction of carbon frameworks employing alkyl fluorides. The scope and limitations, as well as reaction pathways, are discussed.

Umpolung in the allylation reaction is discussed with examples drawn from transition-metal-catalyzed allylic substitution (with the allylic unit acting as an electrophile) and Lewis base-catalyzed allylation of aldehydes with allyltrichlorosilane (with the allyl acting as a nucleophile). Iridium-catalyzed electrophilic allylation of O -nucleophiles has been employed in our new approach to C -nucleoside analogs, where the C-O bond (rather than C-C) was constructed stereospecifically. Variation of the absolute configuration in the starting segments allowed the synthesis of all four combinations of D/L-α/β-ribosides. In the nucleophilic allylation of aldehydes, chiral pyridine-type N -oxide catalysts are presented, in particular QUINOX and METHOX, and the intriguing behavior of QUINOX is discussed. Here, the π-π interactions between the substrate aldehyde and the catalyst are suggested to rationalize the experimental observations. Good correlation between the calculated energies for the transition states and the experimentally observed enantioselectivities has been obtained.

The addition of unstabilized carbonyl nucleophiles to allyl-metal fragments still represents a challenge for generating stereoselectively tertiary (and quaternary) stereogenic centers. In this context, the decarboxylative Carroll rearrangement of secondary and tertiary allyl β-ketoesters is particularly interesting since chiral γ,δ-unsaturated ketones are obtained. Herein, we show that CpRu half-sandwich complexes can, in the presence of selected enantiopure diimine ligands, catalyze this transformation and afford complete conversions and decent level of enantiomeric excess. Zwitterionic adducts of a hexacoordinated phosphorus anion and CpRu moieties were also associated and shown to generate air-, moisture-, and microwave-stable catalysts that can be readily purified and recycled. Carroll rearrangements of allylic β-ketoesters performed with these zwitterionic species occur with better regio- and enantioselectivity.

Pd-Et 3 B catalytic system promotes the generation of allyl cations, allyl anions, and zwitterionic trimethylenemethane species from the corresponding allylic alcohols. Allyl cations react with a wide variety of nucleophiles, e.g., amines, active methylene compounds, 1,3,5-trihydroxybenzene, indoles, aldehydes (at the α-position). The reaction is extended to dehydrative Grob fragmentation of 1,3-diols. Allyl anions react with aldimines to give homoallyl amines. Zwitterionic trimethylenemethane, generated from 2-methylene-1,3-propanediol, reacts with aldehydes and aldimines to provide 3-methylenecyclopentanols and 3-methylenepyrrolidines, respectively. Vinyl epoxide can be utilized as a synthetic equivalent of 3-butenyl 2-anion-1-cation.

Rhodium complexes are efficient catalysts for the synthesis of organosulfur compounds. They catalyze the addition reaction of organosulfur groups to unsaturated compounds, the substitution of C-H with organosulfur groups, and single-bond metathesis reactions. They cleave S-S bonds and transfer the organosulfur groups to various organic and inorganic molecules, including alkynes, allenes, disulfides, sulfur, isonitriles, imines, diphosphines, thiophosphinites, hydrogen, 1-alkylthio-1-alkynes, thioesters, and allyl sulfides.

Active transition metals, namely, nickel, copper and iron, have been prepared by the reduction of the corresponding chlorides with lithium and a catalytic amount of an arene. These metals, in the form of nanoparticles, have found application in the reduction of a wide variety of functional groups as well as in the alkylation of methyl ketones with primary alcohols.

Highly tuned, one-point binding chiral iron and ruthenium complexes selectively coordinate and activate α,β-unsaturated aldehydes and ketones toward asymmetric catalytic Diels-Alder cycloaddition reactions. Here we focus on the application of these transition-metal Lewis acids to asymmetric catalytic 1,3-dipolar cycloaddition reaction between enals and cyclic and acyclic nitrones as well as aryl nitrile oxides to give isoxazolidines and isoxazolines, respectively.

Kainic acid (KA), rigidified ( S )-glutamic acid, is a well-known kainite receptor agonist for excitatory transmission in the central nervous system (CNS). Our interest in highly selective kainite ligands prompted us to design a series of new kainic homologs, "homokainoids", i.e., conformationally rigidified ( S )-glutamic acids. For the syntheses of enantiopure novel homokainoids (pipecolino-glutamic acids), we successfully applied the cyclohydrocarbonylation (CHC) reaction, which has been developed in these laboratories. Efficient total syntheses of enantiopure novel homokainoids from ( R )-serine feature the highly diastereoselective conjugate addition and the regioselective CHC process in the key steps.

Asymmetric allylic alkylations (AAAs) are among the most powerful C-C bond-forming reactions. We present a brief overview of copper-catalyzed AAAs with organometallic reagents and discuss our own contributions to this field. Work with zinc reagents and phosphoramidite ligands provided a framework for later developments which employ Grignard reagents and ferrocenyl ligands. High yields and excellent regioselectivities and enantioselectivities are achieved. The AAAs may be more general than previously envisioned, in terms of using substrates functionalized with heteroatoms at various positions; heteroatom substituents at the γ-position provide densely functionalized building blocks. These h -AAA reactions rely on the design of appropriate substrates containing heteroatoms and have allowed us to demonstrate viable new approaches toward the synthesis of versatile organic building blocks. We illustrate that the chiral secondary allylic alcohols, primary homo-allylic alcohols and amines can readily be obtained in high enantiomeric purity in a catalytic asymmetric fashion by copper-catalyzed AAAs. Furthermore, we show that manipulation of the terminal olefin provides chiral building blocks where the ee of the starting materials is preserved.

Copper-catalyzed γ-selective substitution of allylic carbonates with diboron provides a new method for the efficient synthesis of allylboronates. Optically active α-chiral allylboronates were synthesized through the reaction of chiral allylic carbonates with bis(pinacolato)diboron in the presence of achiral Cu(I)-catalyst with highly efficient chirality transfer. Additionally, in the presence of a chiral Cu(I) catalyst, optically active α-chiral allylboronates were obtained with >90 % ee through the reaction of prochiral substrates with the diboron.

This account deals with an overview of our recent progress toward the development of molecular catalysts for the reduction in polar functionalities with molecular hydrogen (H 2 ). An emphasis is placed on the newly designed Cp*Ru(PN) complexes, which have been identified as efficient catalysts for the hydrogenation of imides. The structural modification of the complex enhances the catalytic performance and allows efficient access to various chiral synthetic intermediates.

Chiral CuF-catalyzed asymmetric allylation of ketones and ketimines is described. Nucleophile activation via transmetallation (allylboronate to allylcopper), which is facilitated by a cocatalyst [La(O i Pr) 3 or LiO i Pr], is key for these reactions. A CuOTf-3KO t Bu-DUPHOS complex is a comparably effective catalyst that reduces the required amount of chiral phosphines.

The gold-catalyzed endo -cycloisomerization of allenes bearing nucleophilic substituents in the α- or β-position opens up a versatile access to various five- and six-membered heterocycles. Key features of these transformations are the high reactivity of the allene in the presence of Lewis-acidic, carbophilic gold(I) or gold(III) catalysts, and the chirality transfer from the allenic axis of chirality to the new stereogenic center in the cyclization product. Recent contributions of our group include the optimization of chirality transfer by using σ-donor ligands to gold, and applications in the total synthesis of natural products, e.g., of the β-carboline alkaloids (-)-isocyclocapitelline and (-)-isochrysotricine.

Ti(salan) complexes were found to be efficient catalysts for asymmetric epoxidation with aqueous hydrogen peroxide as the oxidant. In the presence of pH 7.4 phosphate buffer, the reaction of various conjugate olefins proceeded smoothly to afford the corresponding epoxides in high yield with high enantioselectivity, even on a multigram scale. Ti(salan) complexes could be prepared from Ti(O i Pr) 4 and the corresponding salan ligand and directly used without isolation and purification.

A new protocol for CO gas-free carbonylation, in which aldehydes are used as a substitute for CO, is described. The protocol consists of two Rh-mediated processes; the Rh-mediated decarbonylation of aldehydes, which leads to the formation of Rh carbonyl, and subsequent Rh-catalyzed carbonylative cyclization utilizing the in situ formed Rh carbonyl species.

We recently reported the first catalytic diamination of alkenes. This protocol calls for the use of Pd(II) as catalyst in combination with PhI(OAc) 2 as terminal oxidant and furnishes the final diamines as cyclic ureas. It consists of an unprecedented two-step reaction of aminopalladation and C sp3 -N-bond formation involving a Pd(IV) species. Introduction of Ni(II) catalysts for homogeneous oxidation allows for an efficient diamination with sulfamides, which lead to convenient liberation of the free diamines. In related protocols, the substrate scope of the diamination has been broadened to the formation of cyclic guanidines.

Nickel-catalyzed carbocyanation reaction of alkynes is described. Alkynes undergo aryl- and allylcyanation reaction in the presence of nickel-phosphine catalysts to give a wide range of substituted acrylonitriles in highly stereo-, regio-, and chemoselective manners. Lewis acid cocatalysts, such as AlMe 3 , AlMe 2 Cl, and BPh 3 , are found to promote the arylcyanation significantly. The cooperative catalysis of nickel and Lewis acid also allows the carbocyanation reaction using alkenyl and alkyl cyanides.

Kinetic resolution of planar-chiral 1,1'-diallylferrocene derivatives was realized by Mo- or Ru-catalyzed asymmetric ring-closing metathesis (RCM). The Mo catalyst showed much better performance than the Ru catalyst in the present reactions, and nearly perfect resolution of the racemic ferrocenes was achieved. This is the first example of highly enantioselective metal-catalyzed methods of preparing optically active planar-chiral metallocenes.

The reaction of N -benzenesulfonylbenzaldimine with Ni(cod) 2 and PCy 3 gave the corresponding η 2 -iminenickel complex quantitatively. Diphenylacetylene reacted with the η 2 -iminenickel complex to generate five-membered aza-nickelacycle. Insertion of second alkynes into the five-membered aza-nickelacycle led to the formation of the corresponding seven-membered aza-nickelacycles. Heating the solution of the seven-membered aza-nickelacycles induced the reductive elimination to give 1,2-dihydropyridine. In the presence of 10 mol % of Ni(cod) 2 and PMe t Bu 2 at 100 °C, the intermolecular [2+2+2] cycloaddition of N -benzenesulfonylbenzaldimine and 2-butyne occurred to give the expected 1,2-dihydropyridine in 87 % yield. In the presence of PCy 3 , the reaction also proceeded catalytically, however, PMe t Bu 2 gave better results. Less bulky or less basic phosphine, P n Bu 3 or P( o -tol) 3 , was not efficient for the reaction. Although Ni(0)-NHC complex was a good catalyst for [2+2+2] cycloaddition of two alkynes and a ketone or an aldehyde, this reaction did not proceed in the presence of an NHC ligand, 1,3-bis-(2,4,6-trimethylphenyl)imidazol-2-ylidene.

The oxidative coupling of benzoic acids with alkynes and alkenes effectively proceeds in the presence of a Rh catalyst and an appropriate oxidant to produce the corresponding isocoumarin and phthalide derivatives, respectively. Interestingly, by using an Ir catalyst in place of Rh, the acids and alkynes undergo 1:2 coupling accompanied by decarboxylation to afford naphthalene derivatives exclusively.

A new type of reagent, γ-methylidene-δ-valerolactones, has been devised, which acts as a four-carbon unit in a Pd-catalyzed cycloaddition reaction through the formation of a 1,4-zwitterionic species. The utility has been demonstrated in the context of stereoselective [4+3] cycloaddition with nitrones to provide highly functionalized 1,2-oxazepines, including the asymmetric variant with high enantioselectivity.

Zr-mediated equilibrating cyclocarbonylation of a designed triene led with high diastereocontrol to the ABC 6-6-5 tricyclic core of ritterazine N. The 5-5 EF spiroketal side chain of ritterazine N was prepared by equilibrating cyclization of an acyclic keto diol. The two components were coupled, and the D ring was assembled by intramolecular aldol condensation.

Rhenium complex, [ReBr(CO) 3 (thf)] 2 -catalyzed reactions between aromatic imines and either acetylenes or α,β-unsaturated carbonyl compounds gave indene derivatives in good to excellent yields. These reactions proceed via C-H bond activation, insertion of acetylenes or α,β-unsaturated carbonyl compounds, intramolecular nucleophilic cyclization, and reductive elimination. Indene derivatives were also obtained from aromatic ketones and α,β-unsaturated carbonyl compounds in the presence of catalytic amounts of the rhenium complex and p -anisidine. Sequential ruthenium-catalyzed hydroamination of aromatic acetylenes with anilines, and rhenium-catalyzed reactions of the formed aromatic ketimines with α,β-unsaturated carbonyl compounds also provided indene derivatives.

A new type of catalytic hydrosilylation of arylalkynes was induced by a 16-electron ruthenium bis(silyl) phosphine complex, resulting in ortho -silylation of the aryl group as well as a hydrogenation of the alkyne CC bond to give an ( E )-form of alkene selectively. On the other hand, the same reaction using a related bis(silyl) complex having an η 6 -toluene ligand instead of the phosphine ligand as a catalyst led to a normal hydrosilylation reaction to afford silylalkene.

Selective cross-addition of triisopropylsilylacetylene (TIPSA) to unactivated alkynes is catalyzed by dinuclear and mononuclear palladium complexes supported by a multidentate ligand, N , N' -bis[2-(diphenylphosphino)phenyl]formamidine (dpfamH). While the addition reactions of TIPSA to dialkylacetylenes using palladium catalysts supported by monodentate and bidentate ligands gives dimers of TIPSA as major products, the reactions with the palladium complexes supported by dpfam affords cross-adducts selectively, in which the yields of TIPSA dimers are less than 5 %. The addition of TIPSA to monoalkylacetylenes also gives cross-adducts as major products, although the selectivity and yield are moderate.

New carbocyclizations that proceed via catalytic metal-vinylidenes are presented. Metal-vinylidene catalytic species, which are easily accessible from terminal alkynes and catalytic amounts of transition-metal complexes, can be involved either in pericyclic reactions or in tandem processes triggered by nucleophilic attack at the electrophilic position of the vinylidene. In both cases, a wide variety of valuable cyclic compounds are easily accessible. Some recent carbocyclizations will be described.

A new hydrosilylative cross-coupling reaction of a variety of alkynes with several alkenes, which is catalyzed by a cationic Pd complex [Pd(η 3 -C 3 H 5 )(cod)] + [PF 6 ] - (cod = 1,5-cyclooctadiene) was studied systematically. The reaction using HSiCl 3 as an addend afforded more or less two types of products consisting of four possible derivatives, R 1 CH=CR 2 -CHR 3 -CHR 4 -SiCl 3 , which always contained 4-trichlorosilyl-1-butene frameworks, in acceptable combined yields. The coupling pattern was markedly dependent both on the precatalyst in the absence or presence of PPh 3 ligand and on the combination of the alkyne and alkene partners employed. A possible catalytic cycle that involves an initial hydropalladation of an alkyne, followed by a facile and specific carbopalladation of an alkene, is proposed. At the same time, the lack of regioselectivity in the latter step is noted.

The first boryl anion, boryllithium, was synthesized by a reduction of bromoborane precursor using lithium naphthalenide in tetrahydrofuran (THF) solvent at -45 °C. Structural and spectroscopic study revealed an ionic character of B-Li bond. Boryllithium could be utilized as a source of boryl ligand in the transition-metal chemistry. Structural and spectroscopic features of the resulting boryl complexes confirmed the large trans influence of boryl ligand.