Amides transition metal catalysts

Recent studies in our laboratory have demonstrated that formylation of P-H bonds can be achieved without the aid of transition metal catalysts under mild reaction conditions [47]. For example, amide and thioether functionalized primary phosphines, 5 and 9 respectively, upon treatment with 37% formaldehyde produced the corresponding amide/thioether functionaUzed water soluble phosphines 21 and 22 respectively in near quantitative yield (Scheme 10) [47]. 

Addition of HCN to acetone to form the cyanohydrin is still the main route to methyl methacrylate. Hydrocyanins can be converted to amino acids as well. The nitrile group can be easily converted to amines, carboxylic acids, amides, etc. Addition to aldehydes and activated alkenes can be done with simple base, but addition to unactivated alkenes requires a transition metal catalyst. The methods of HCN addition have been discussed by Brown [2],... 

Transition metal catalysts and biocatalysts can be combined in tandem in very effective ways as shown by the following example (Scheme 2.21). An immobilized rhodium complex-catalyzed hydrogenahon of 46 was followed by enzymatic hydrolysis of the amide and ester groups of 47 to afford alanine (S)-9 in high conversion and enanhomeric excess. Removal of the hydrogenation catalyst by filtration prior to addition of enzyme led to improved yields when porcine kidney acylase 1 was used, although the acylase from Aspergillus melleus was unaffected by residual catalyst [23]. 

Except for the metallic impurities present on the walls of poorly washed glassware, no other transition metal catalyst may be assumed to be present in this experiment. Consequently, the transfer of the dimethylamino group from the ortho amide II to I must be taking place under less energy demanding conditions, where protic acid catalysis suffices to activate the triple carbon to carbon bond. ... 

The use of transition-metal catalysts allows aryl halides to react with the nitrogen of amides or carbamates, as well as amines, to give the corresponding Al-aryl amide or Waryl carbamate. Amides react with aryl halides in the presence of a pal-ladium catalyst or a copper catalyst. WAryl lactams are prepared by the reaction of a lactam with an aryl halide in the presence of a palladium catalyst. 

Recently, transition-metal-catalyzed reaction of iminoiodinanes 731 has been focused as a method of nitrogen transferring (Scheme 226). The iminoiodinanes 731 are readily synthesized from sulfor-amides or carbamates 730 by treatment with Phl-(OAc)2. The reaction of 731 with a transition-metal catalyst M produces the metal nitrenoid 732. The... 

In reductive amination the alkylation is performed under hydrogen in the presence of a transition metal catalyst and an aldehyde or ketone as the alkylating agent. Reductive alkylation is a general reaction which can be extended to several other nucleophiles. We have developed this method for anilines in particular [8] and extended it [9] to amide N-alkylation [10] and ether synthesis [11]. We have shown that nitro derivatives can be used as aniline precursors in a one-pot reduction of the nitro group and subsequent reductive alkylation of the resulting aniline (Figure 1). 

The decomposition of suitably crafted diazoimides 181, in the presence of a transition metal catalyst, affords the metallo-carbenoids 182 that undergo intramolecular cycUzation onto the neighboring amide carbonyl oxygen to form the five-membered ring carbonyl yUdes (isomiinchnones) 183 (Scheme 58). Early examples of inter- and intramolecular 1,3-dipolar cycloaddition of the mesoionic ylides 183 have mainly emanated from the research groups of Ibata [149], Maier [150] and Padwa [151]. These reactive species (isomimchnones) can be trapped by various electron-rich and electron-deficient dipolarophiles [152] to furnish the cycloadducts in high yield. Much work has been reported in this area and for clarity of presentation is described here under various subheadings. 

In Scheme 1.2, all of the types of carbonylations that are discussed in the book are depicted. Alcohols, amines, ethers, carboxylic acids and halides can be converted to acids, amides, esters, ketones, alkynones, alkenones, anhydrides and acid halides with the assistance of transition metal catalysts in the presence of a CO source. The CO sources used can be carbon monoxide gas, Mo(CO)6, Co(CO>6, formic acid, aldehyde, etc. If the starting material is alcohols or amines, some additives for activation are needed, such as BuONO, TsCl, AcCl. If the substrate is (Hetero)ArH, additional oxidants will be necessary this is a so-caUed oxidative carbonylation. If an unsaturated compound is to be carbonylated, a nucleophile NuH that carries an acidic hydrogen has to be present. In the case of insertion reactions, this is not necessary. 

The coupling reaction with phenyl isocyanate was also examined. The aryl-manganese bromide reagents underwent a coupling reaction with phenyl isocyanate without any transition metal catalyst to yield the corresponding amides in moderate yields (Table 8.6). 

Over the last few years, great advances have been made on the a-arylation of carbonyl compounds catalyzed by transition-metal catalysts. A large number of carbonyl compounds, such as ketones, aldehydes, esters, and amides, can be coupled with electron-neutral, electron-rich, electron-poor. 

Transition Metal Catalysts for the Amidation of Carboxylic Acids... 

The last method for the preparation of 2-quinolones described in this chapter relies on a intramolecular Heck cyclization starting from heteroaryl-amides (Table 2) [57]. These are synthesized either from commercially available pyrrole- and thiophene-2-carboxylic acids (a, Table 2) or thiophene-and furan-3-carboxylic acids (b, Table 2) in three steps. The Heck cyclization is conventionally performed with W,Ar-dimethylacetamide (DMA) as solvent, KOAc as base and Pd(PPh3)4 as catalyst for 24 h at 120 °C resulting in the coupled products in 56-89% yields. As discussed in Sect. 3.4, transition metal-catalyzed reactions often benefit from microwave irradiation [58-61], and so is the case also for this intramolecular reaction. In fact, derivatives with an aryl iodide were successfully coupled by conventional methods, whereas the heteroarylbromides 18 and 19, shown in Table 2, could only be coupled in satisfying yields by using MAOS (Table 2). 

In order to incorporate polar-functionalized olefins, the catalyst system must exhibit tolerance to the functionality as described above. Therefore, polar monomer incorporation by the Ni(II) catalysts is generally not observed. Traces of methyl acrylate can be incorporated by the Ni(II) catalyst only under low loadings of that monomer [85], Acrylamide has been incorporated after prior treatment with tri-isobutylaluminum to block the amide donor sites, although polymerization activities are still relatively low [86], A similar protection of Lewis-basic functionalities by the coactivator has been cited to explain the copolymerization of certain monomers by early transition metal systems as well [40],... 

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