Abstract: The catalytic addition of an organic amine R2N H bond to alkenes or alkynes (hydroamination) to give nitrogen containing molecules is of great interest for academic and industrial research. Since today most amines are made in multistep syntheses, hydroamination would offer the most attractive alternative synthetic route. It was shown, that hydroamination can be catalyzed by transition metals (dand f-block) and alkali metals.[1] Depending on the catalytic system either an activation of the C C multiple bond or the N H bond takes place. Alkene or alkyne activation is usually accomplished with late-transition metals through coordination of the C C multiple bond to the metal center. In contrast, the amino function can be activated by alkali or early transition metals, which generate an amido species, or by N H oxidative addition to electron-rich transition metals. Depending on the nature of the catalysts and the substrates either Markovnikov or anti-Markovnikov products are obtained [Eq. (1)]. The scope of catalytic hydroamination has been reviewed recently.[1–6] Today, the vast number of enantioselective syntheses of molecules bearing an amine functionality use classical stoichiometric reactions with chiral auxiliaries or utilize enantiomerically pure starting materials.[7] As a result of the increasing interest in the hydroamination reaction some research groups have started to investigate the enantioselective R2N H addition to C C double bonds. In early transition-metal chemistry Marks et al. implemented C1-symmetric organolanthanide ansa-metallocene catalysts of the type [Me2Si(hC5Me4)(h-C5H3R*)LnE(SiMe3)2] (1)[8–10] (R*= ( )-menthyl, (þ)-neomenthyl, ( )-phenylmenthyl; Ln=La, Nd, Sm, Y, Lu; E=CH, N) and [Me2Si(hOHF)(h-C5H3R*)LnN(SiMe3)2] (2)[11] (OHF= octahydrofluorenyl; R*= ( )menthyl; Ln= Sm, Y, Lu) in the enan-

Abstract: The objective of this review is to survey the current state of the Wacker and related alkene oxidation reactions focusing on the reactions of higher alkenes and emphasizing the mechanistic pictures that have evolved, the current understanding regarding issues of selectivity, recent applications of the chemistry in synthesis, and the use of other transition metal catalysts to effect related oxidation reactions. The Wacker oxidation reaction has been extensively studied over the years. There are a number of excellent reviews published on various aspects of the reaction (1), with a series of reviews by Tsuji deserving particular note for their special insight into the development of this reaction (2-4).

Abstract: The direct addition of water and a variety of alcohols to activated olefins was observed in the presence of nucleophilic phosphine catalysts. Unlike existing methods, the reactions proceed at room temperature and in the absence of transition metals, or strong acids or bases. The use of simple commercially available catalysts makes this an attractive method for the preparation of β-hydroxy and β-alkoxy substrates, which are prevalent targets and intermediates in organic synthesis. The scope and mechanism of this reaction has been explored, and the compound that acts as the resting state of the catalyst was synthesized independently. Our mechanism also suggests the possibility of extending the scope of this reactivity to other classes of nucleophiles.

Abstract: Two gas-phase catalytic cycles for the two-electron oxidation of primary and secondary alcohols were detected by multistage mass spectrometry experiments. A binuclear dimolybdate center [Mo(2)O(6)(OCHR(2))](-) acts as the catalyst in both these cycles. The first cycle proceeds via three steps: (1) reaction of [Mo(2)O(6)(OH)](-) with alcohol R(2)HCOH and elimination of water to form [Mo(2)O(6)(OCHR(2))](-); (2) oxidation of the alkoxo ligand and its elimination as aldehyde or ketone in the rate-determining step; and (3) regeneration of the catalyst via oxidation by nitromethane. Step 2 does not occur at room temperature and requires the use of collisional activation to proceed. The second cycle is similar but differs in the order of reaction with alcohol and nitromethane. The nature of each of these reactions was probed by kinetic measurements and by variation of the substrate alcohols (structure and isotope labeling). The role of the binuclear molybdenum center was assessed by examination of the relative reactivities of the mononuclear [MO(3)(OH)](-) and binuclear [M(2)O(6)(OH)](-) ions (M = Cr, Mo, W). The molybdenum and tungsten binuclear centers [M(2)O(6)(OH)](-) (M = Mo, W) were reactive toward alcohol but the chromium center [Cr(2)O(6)(OH)](-) was not. This is consistent with the expected order of basicity of the hydroxo ligand in these species. The chromium and molybdenum centers [M(2)O(6)(OCHR(2))](-) (M = Cr, Mo) oxidized the alkoxo ligand to aldehyde, while the tungsten center [W(2)O(6)(OCHR(2))](-) did not, instead preferring the non-redox elimination of alkene. This is consistent with the expected order of oxidizing power of the anions. Each of the mononuclear anions [MO(3)(OH)](-) (M = Cr, Mo, W) was inert to reaction with methanol, highlighting the importance of the second MoO(3) unit in these catalytic cycles. Only the dimolybdate center has the mix of properties that allow it to participate in each of the three steps of the two catalytic cycles. The three reactions of these cycles are equivalent to the three essential steps proposed to occur in the industrial oxidation of gaseous methanol to formaldehyde at 300-400 degrees C over solid-state catalysts based upon molybdenum(VI)-trioxide. The new gas-phase catalytic data is compared with those for the heterogeneous process.

Abstract: Enantioselective catalytic reactions that operate directly on inexpensive unactivated alkenes are extraordinarily useful for the preparation of chiral organic building blocks and new materials. While a number of such processes have been developed, our ability to meet the intensifying demand for inexpensive stereochemically complex materials will require a significant expansion of practical catalytic asymmetric reaction methodology. In this regard, the rhodium-catalyzed enantioselective diboration reaction has been developed in order to address a number of extant problems in catalytic alkene transformation simultaneously. This process provides an enantiomerically enriched reactive dimetalated intermediate which can be converted to a variety of difunctional reaction products.

Abstract: A complete catalytic cycle for the cyclotrimerization of acetylene with the CpRuCl fragment has been proposed and discussed based on DFT/B3LYP calculations, which revealed a couple of uncommon intermediates. The first is a metallacyclopentatriene complex RuCp(Cl)(C(4)H(4)) (B), generated through oxidative coupling of two alkyne ligands. It adds another alkyne in eta(2) fashion to give an alkyne complex (C). No less than three successive intermediates could be located for the subsequent arene formation. The first, an unusual five- and four-membered bicyclic ring system (D), rearranges to a very unsymmetrical metallaheptatetraene complex (E), which in turn provides CpRuCl(eta(2)-C(6)H(6)) (F) via a reductive elimination step. The asymmetry of E, including Cp ring slippage, removes the symmetry-forbidden character from this final step. Completion of the cycle is achieved by an exothermic displacement (21.4 kcal mol(-)(1)) of the arene by two acetylene molecules regenerating A. In addition to acetylene, the reaction of B with ethylene and carbon disulfide, the latter taken as a model for a molecule lacking hydrogen atoms, has also been investigated, and several parallels noted. In the case of the coordinated alkene, facile C-C coupling to the alpha carbon of the metallacycle is feasible due to an agostic assistance, which tends to counterbalance the reduced degree of unsaturation. Carbon disulfide, on the other hand, does not coordinate to ruthenium, but a C=S bond adds instead directly to the Ru=C bond. The final products of the reactions of B with acetylene, ethylene, and carbon disulfide are, respectively, benzene, cyclohexadiene, and thiopyrane-2-thione, the activation energies being lower for acetylene.

Abstract: (E)-Alkene units are frequently found in macrocyclic natural products. Among the reactions that form the double bond during the cyclization, the classical Horner-Emmons coupling is still frequently used with success. During the last decade, ring-closing metathesis has emerged as a very powerful tool for the synthesis of large rings, but the E/Z selectivity, which is rarely predictable, depends on many factors which will be discussed in this review. The best solution might be a two-step procedure involving ring-closing alkyne metathesis (RCAM) followed by stereoselective reduction of the macrocyclic alkyne unit to the corresponding E double bond.

Abstract: The metal−oxygen bond plays a critical role in some of the most important biological and synthetic reactions. However, the majority of these processes result in the oxidation of the target organic substrate; applications of this class of metal complexes to other organic transformations are extremely rare. In this paper, we report a new type of catalytic process in which complexes with metal−oxygen multiple bonds are used as reductants rather than oxidants. The overall reaction provides a highly chemoselective reduction/protection of carbonyl groups. In addition to providing a new way of catalyzing organic reactions, these catalysts can be used in the presence of a wide range of other functional groups such as amino, cyano, nitro, aryl halo, ester, and alkene; unlike many of their late metal relatives, they are inexpensive as well as air and moisture tolerant.

Abstract: Bis(thiophosphinic amidate) complexes (i.e., 1) of representative group 3 and lanthanide metals have been quantiatively prepared in situ from the corresponding thiophosphinic amides and Ln[N(TMS)2]3. These unusual pentacoordinate complexes exhibit very high activity as catalysts for intramolecular alkene hydroamination.

Abstract: A concise, flexible, and high yielding entry into the family of amphidinolide T macrolides, a series of cytotoxic natural products of marine origin, has been developed. All individual members, except amphidinolide T3 (3), derive from compound 39 as a common synthetic intermediate which is formed from three building blocks of similar size and complexity. The fragment coupling steps involve a highly diastereoselective SnCl(4) mediated reaction of the furanosyl sulfone derivative 11 with the silyl enol ether 18 and a palladium-catalyzed Negishi type coupling reaction between the polyfunctional organozinc reagent derived from iodide 32a and the enantiopure acid chloride 24b. The 19-membered macrocyclic ring is then formed by a high yielding ring closing metathesis (RCM) reaction of diene 33 catalyzed by the "second generation" ruthenium carbene complex 34. The efficiency of the RCM transformation stems, to a large extent, from the conformational bias introduced by the syn-syn-configured stereotriad at C12-C14 of the substrate which constitutes a key design element of the synthesis plan. The use of Nysted's reagent 38 in combination with TiCl(4) was required for the olefination of the sterically hindered ketone group in 36, whereas more conventional alkene formations were unsuccessful for this elaboration. Finally, it is shown that the inversion of a single and seemingly remote stereocenter (C12) in one of the building blocks not only affects the efficiency and stereochemical outcome of the RCM step but also exerts a significant influence on the course of the acyl-Negishi reaction, allowing a radical manifold to compete with productive cross coupling.

Abstract: The objective of this review is to survey the current state of the Wacker and related alkene oxidation reactions focusing on the reactions of higher alkenes and emphasizing the mechanistic pictures that have evolved, the current understanding regarding issues of selectivity, recent applications of the chemistry in synthesis, and the use of other transition metal catalysts to effect related oxidation reactions. The Wacker oxidation reaction has been extensively studied over the years. There are a number of excellent reviews published on various aspects of the reaction (1), with a series of reviews by Tsuji deserving particular note for their special insight into the development of this reaction (2-4).

Abstract: The silver complex [HB(3,5-(CF3)2Pz)3]Ag(THF) featuring a highly fluorinated tris(pyrazolyl)borate ligand catalyzes the formation of aliphatic carbon−halogen bond activation products under remarkably mild conditions. For example, the reaction between CHCl3 and ethyl diazoacetate (EDA) at room temperature in the presence of the silver catalyst afforded HClC(CO2Et)CCl2H in 60% yield. The presence of β-hydrogens on the alkyl halide leads to net hydrogen halide addition to the carbene and an alkene.

Abstract: Nickel-catalyzed, intramolecular and intermolecular reductive coupling of alkynes and epoxides affords synthetically useful homoallylic alcohols of defined alkene geometry. Very high regioselectivity is generally observed, and cyclizations proceed with complete selectivity for endo epoxide opening. This catalytic reaction represents the first use of a non-π-based electrophile in a growing class of nickel-catalyzed, multicomponent coupling reactions, and is the first catalytic method of reductive coupling of alkynes and epoxides that is effective for both intermolecular and intramolecular cases, and mechanistically distinct from these, possibly involving a nickella(II)oxetane.

Abstract: Density functional theory studies of intramolecular ene-like (or the so-called 1,3-dipolar ene) reactions between nitrile oxides and alkenes (Ishikawa, T.; Urano, J.; Ikeda, S.; Kobayashi, Y.; Saito, S. Angew. Chem., Int. Ed. 2002, 41, 1586) show that this reaction is a three-step process involving a stepwise carbenoid addition of nitrile oxide to form a bicyclic nitroso compound, followed by a retro-ene reaction of the nitrosocyclopropane intermediate. The competitive reactions, either the intramolecular (3+2) reactions between nitrile oxides and alkenes or the intermolecular dimerizations of nitrile oxides to form furoxans, can overwhelm the intramolecular 1,3-dipolar ene reactions when the tether joining the nitrile oxide and alkene is elongated or some substituents such as trimethylsilyl are absent.

Abstract: A variety of Pd-catalyzed oxidative nucleophile/alkene cyclizations proceeds in excellent yield under simple aerobic conditions in nonpolar media (Pd catalyst, pyridine, and O_2 in toluene). Nucleophiles for these cyclizations include phenols, carboxylic acids, amides, and primary alcohols. Additionally, enantioselective catalysis is feasible with a Pd-sparteine system (see picture). Enantioselectivities of up to 90 % ee are observed for simple phenol/alkene cyclizations.

Abstract: Visible light irradiation of a reaction mixture of carbonyl-coordinated tetra(2,4,6-trimethyl)phenylporphyrinatoruthenium(II) (RuIITMP(CO)) as a photosensitizer, hexachloroplatinate(IV) as an electron acceptor, and an alkene in alkaline aqueous acetonitrile induces selective epoxidation of the alkene with high quantum yield (Φ = 0.6, selectivity = 94.4% for cyclohexene and Φ = 0.4, selectivity = 99.7% for norbornene) under degassed conditions. The oxygen atom of the epoxide was confirmed to come from a water molecule by an experiment with H218O. cis-Stilbene was converted into its epoxide, cis-stilbeneoxide, without forming trans-stilbeneoxide. trans-Stilbene, however, did not exhibit any reactivity. Under neutral conditions, an efficient buildup of the cation radical of RuIITMP(CO) was observed at the early stage of the photoreaction, while an addition of hydroxide ion caused a rapid reaction with the cation radical to promote the reaction with reversion to the starting RuIITMP(CO). A possible involvemen...

Abstract: Cleavage of a carbon−phosphorus bond is achieved under palladium catalysis in an oxidative Heck-type reaction which exploits arylphosphonic acids. The reaction of arylphosphonic acids with alkenes provides arylation products in good yields in the presence of TBAF with trimethylamine oxide as an oxidant.

Abstract: An examination of earlier reports of poor-to-modest results using Pd-catalyzed asymmetric allylic alkylations (AAA) to effect cyclization to form tetrasubstituted carbons reveals several novel factors that can influence this class of reactions. Thus, carboxylate has a major effect on such cyclizations wherein the ee increases from 14% ee favoring the S with no carboxylate to 84% ee favoring the R enantiomer in the presence of 1 equiv of carboxylate. Changing the double bond geometry from E to Z further increases the ee to 97%. Furthermore, the chiral catalyst that forms the R enantiomer with the E-alkene forms the S enantiomer with the Z alkene. In contrast to trisubstituted alkene substrates, disubstituted ones show a decrease in ee in going from the E to Z alkenes. The role of carboxylate appears to be a ligand to Pd during the catalytic cycle, a previously unsuspected phenomenon since such reactions are generally believed to involve π-allylpalladium cationic complexes. The dependence upon alkene geomet...

Abstract: The pi complexes first formed as essential intermediates from alkenes, alkynes, and allenes with bromine have been investigated in different solvents by UV-spectroscopy in combination with stopped-flow techniques allowing the determination of the equilibrium constants, K(f). Using alkenes with sterically protected double bonds, such as di-tert-butylstilbene and tetraneopentylethylene, the reaction stops at the stage of the 1:1 and 1:2 pi complex of the alkene with bromine as persistent species in 1,2-dichlorethane as solvent. Calculations by state-of-art ab initio and DFT methods reproduces the experimentally determined thermodynamic values quite well, and reveal the preferred structures and nature of both complexes for ethene, ethyne, and allene. Consideration of the entropy term reveals that complexes are stabilized in solution owing to reduction of the entropy loss by restricted translations and rotation. According to calculations these species are Mulliken-outer-type complexes with no or little charge transfer from bromine to the double or triple bond, respectively. The 1:2 complex has a close structural relationship to the bromonium- or bromirenium ion, which is the subsequent intermediate on the reaction coordinate. Steric influences show a strong effect on the K(f) value, which can be explained by the polarizibility of the parent system. Addition-elimination often occurs. In bromination of adamantylidenadamantane and its derivatives the reaction stops at the stage of the bromonium ion. The effect of various polar groups situated in equatorial homoallyl positions on the stability of corresponding pi complex and bromonium ion has been studied in this series.