Metal-catalysed synthesis

Hartwig, J.F., Transition metal catalysed synthesis of arylamines and aryl ethers from aryl halides and triflates scope and mechanism, Angew. Chem., Int. Ed. Engl, 1998, 37, 2047-2067. 

SCHEME 31. Transition metal-catalysed synthesis of a polycarbostannane... 

Scheme 6.1 Metal-catalysed synthesis of P-stereogenic phosphines and derivatives via phosphido complexes.

A homogeneous metal-catalysed synthesis of anilines by amination of benzoic acids, and the oxidative amination of 1,2,4,5-tetrazines have been described. 

Chiral amines and diamines are readily available substrates for the synthesis of ligands for transition metal-catalysed reactions since they can easily be transformed into chiral ureas and thioureas. Therefore, several groups have prepared chiral symmetrical ureas and thioureas, dissymmetrical ureas and thioureas, amino-urea and thiourea derivatives. Finally polyureas and non-soluble polythioureas were also prepared and tested as ligands for asymmetric catalysis. 

Substituted thioureas have been used as ligands for transition-metal catalysed reactions and as organocatalysts for organic synthesis. These points will be discussed in Sects. 4 and 5. We first present some aspects of the coordination modes of ureas and thioureas. 

A central focus in modem organic synthesis has been the development of highly efficient catalytic processes for the syntheses of natural and unnatural compounds of medicinal interest or intermediates useful for functional materials. A particularly attractive approach is to apply transition metal catalysed cyclisation reactions for the transformation of simple starting materials into monocyclic, bicyclic and polycyclic scaffolds that can be further elaborated into specific targets. 

Synthesis of optically pure compounds via transition metal mediated chiral catalysis is very useful from an industrial point of view. We can produce large amounts of chiral compounds with the use of very small quantities of a chiral source. The advantage of transition metal catalysed asymmetric transformation is that there is a possibility of improving the catalyst by modification of the ligands. Recently, olefinic compounds have been transformed into the corresponding optically active alcohols (ee 94-97%) by a catalytic hydroxylation-oxidation procedure. 

Sulfoximines bearing a chiral sulfur atom have recently emerged as valuable ligands for metal-catalysed asymmetric synthesis.In particular, C2-symmetric bis(sulfoximines), such as those depicted in Scheme 1.51, were applied to the test reaction, achieving enantioselectivities of up to 93% ee. The most selective ligand (R = c-Pent, R = Ph) of the series was also applied to the nucleophilic substitution reaction of l,3-diphenyl-2-propenyl acetate with substituted malonates, such as acetamido-derived diethylmalonate, which provided the corresponding product in 89% yield and 98% ee. 

We must give first an outline of the non-metal pathways which we observe in all cells. We start here because we know nothing about their abiotic chemistry but assume that cellular life arose from it. We shall assume that the basic requirement of all metabolism is the energised and catalysed synthesis of polysaccharides, lipids, proteins and nucleic acids. These are polymers (see Table 4.5), formed from monomers, all of which could have always arisen when energy was applied to the... 

Transition metal catalysed precipitation polymerization utilizes the advances in the development of suitable catalysts for homogeneous reactions in SCCO2. For example, the synthesis of poly(phenyl acetylene) may been achieved using a... 

The transition metal catalysed addition of HCN to alkenes is potentially a very useful reaction in organic synthesis and it certainly would have been more widely applied in the laboratory if its attraction were not largely offset by the toxicity of HCN. Industrially the difficulties can be minimised to an acceptable level and we are not aware of major accidents. DuPont has commercialised the addition of HCN to butadiene for the production of adiponitrile [ADN, NC(CH2)4CN], a precursor to 1,6-hexanediamine, one of the components of 6,6-nylon and polyurethanes (after reaction with diisocyanates). The details of the hydrocyanation process have not been released, but a substantial amount of related basic chemistry has been published. The development of the ligand parameters % and 0 by Tolman formed part of the basic studies carried out in the Du Pont labs related to the ADN process [1],... 

Scheme 36 Hydroazulene synthesis by transition metal catalysed C/C-bond forming reactions...

These reactions involve metallate rearrangements , migratory insertion and transition metal-catalysed vinylic substitution reactions. They also perform well in applications in natural product synthesis . Many useful synthetic possibilities arise from application of ring-closing olefin metathesis (RCM) to unsaturated homoaldol products and their derivatives by means of the Grubbs catalyst 3942 4-286 Equation 105 presents some examples. ... 

The formation of the chromene caibamate 21 from resorcinol dicarbamate involves directed ortho metallation and an intramolecular 0- 0 carbamoyl transfer. Further manipulation utilising directed metallation and transition metal catalysed reactions allows the synthesis of plicadin, a naturally occurring coumestan <99AG(E)1435>. 

Roberts, S. M., Xiao, J., Whittall, J. and Pickett, T. E. (Eds) in Catalysts for Fine Chemical Synthesis 3 Metal Catalysed Carbon-Carbon Bond-Forming Reactions. John Wiley Sons, Ltd Chichester, 2004, 230-237. 

The transition metal catalyzed synthesis of five membered heterocycles, particularly of condensed ring systems, has attracted considerable attention. The ease of the formation of five membered rings has been utilised both in intramolecular ring closure processes, and in the combination of two (three) fragments through the formation of a carbon-carbon and a carbon-heteroatom bond. This chapter is dedicated to examples, where the construction of the five membered heterocycle is achieved in a transition metal catalysed step. 

Another very important aspect of these transition metal-catalysed cross-coupling reactions stems from the high selectivity observed with stereo-defined vinyl sulfides. Applications to the stereoselective syntheses of pheromones were straightforward (see [321] and references therein), as shown in the two-step synthesis of muscalure from (Z)-l-bromo-2-phenylthioethylene [322] involving its sequential coupling through the bromo and phenylthio substituents with the appropriate derivatives. 

Thioesters have been used for carbon-carbon bond formation in transition metal-catalysed Grignard reactions. In the accompanying scheme two sequential cross-coupling reactions with 5-phenvl carbonochloridothioate and Grignard reagents led to a general and efficient ketone synthesis [377,378]. 

Dithioacetals (see also dithianes and dithiolanes) alkylation of 98 as acyl anion equivalents 75 carbanions of 87,97-102 cleavage of 14-18,98,102 desulfurization of 78 metal-catalysed coupling 127 reaction with Grignard reagents 127 reductive lithiation of 89 synthesis of 12-19,97-102 Dithioacids synthesis of 40... 

Although a metal catalysed decomposition of ethyl diazoacetate was originally described by Silberrad and Roy in 19061, it was to be many years before the value of this type of process for cyclopropanation of alkenes using transition metal catalysts was widely appreciated and reliable, efficient methods were developed. By the early 1960s, the reaction had become important in organic synthesis. Various transition metal compounds have been screened for catalytic cyclopropanation. Copper, rhodium and palladium compounds have... 

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