Amido olefins

A furmer demonstration of me synmetic utihty of the aminotellurinylation reaction is illustrated by the elimination of phenylteUurinic acid from me tellmmyl carbamates, giving amido olefins as shown in the accompanying example. 

The ansa-Xmk d macrocycle imido titanium complexes have been described. They are isolobal analogs of ansa-Xmkcd bis-Gp complexes and relatives of Cp-amido olefin polymerization catalysts.1685... 

Zuccaccia, C., Macchioni, A., Busico, V. et al. (2008) Intra- and intermolecular NMR studies on the activation of arylcyclometallated hafnium pyridyl-amido olefin polymerization precatalysts. Journal of the American Chemical Society, 130,10354-10368. 

The proposed reaction mechanism involves intermolecular nucleophilic addition of the amido ligand to the olefin to produce a zwitterionic intermediate, followed by proton transfer to form a new copper amido complex. Reaction with additional amine (presnmably via coordination to Cn) yields the hydroamination prodnct and regenerates the original copper catalyst (Scheme 2.15). In addition to the NHC complexes 94 and 95, copper amido complexes with the chelating diphosphine l,2-bis-(di-tert-bntylphosphino)-ethane also catalyse the reaction [81, 82]. 

Once the N—H bond has been oxidatively added to the Ir(I) complex (in the context of the CCM cycle, vide supra), the resultant Ir(III) intermediate is a Lewis acid that is thought to coordinate the olefin. A synergistic effect between the coordinated electrophilically activated olefin and the highly nucleophilic nature of the amido function is believed to facilitate the C—N bond formation within the coordination sphere of the Ir center (see 56). Alkyl-amino-Ir(III) complexes, such as the key intermediate 24 of the CCM system (as described in Section 6.2.1) are of paramount importance to better understand Ir-catalyzed hydroaminations. Complex... 

Derivatives of the steroids androstene and pregnene have been transformed directly into A-acyl amino acids by an orthogonal catalysis procedure, utilizing [RhCl(nbd)]2 and Co2(CO)8 (Scheme 11). The rhodium phosphine catalyst (generated in situ in the presence of syn-gas and phosphine) affects hydroformylation of the internal olefin to generate aldehyde. In the presence of Co2(CO)8, A-acyl amino acids are obtained as the major products. An unstable amido alcohol intermediate, formed by reaction of the amide with aldehyde, is proposed to undergo cobalt-catalyzed GO insertion to yield the desired A-acyl amino acid. 

Cationic transition metal amide complexes have been investigated in part because of their potential in catalysis p irticularly for olefin polymerization. Much of this work has concerned polydentate amido, linked cyclopentadienyl-amido or delocalized nitrogen centred bidentate ligands (see later). However, the structures of a small number of cationic complexes containing monodentate amido ligands have been determined. These include... 

Density functional theory studies arene chromium tricarbonyls, 5, 255 beryllium monocyclopentadienyls, 2, 75 chromium carbonyls, 5, 228 in computational chemistry, 1, 663 Cp-amido titanium complexes, 4, 464—465 diiron carbonyl complexes, 6, 222 manganese carbonyls, 5, 763 molybdenum hexacarbonyl, 5, 392 and multiconfiguration techniques, 1, 649 neutral, cationic, anionic chromium carbonyls, 5, 203-204 nickel rj2-alkene complexes, 8, 134—135 palladium NHC complexes, 8, 234 Deoxygenative coupling, carbonyls to olefins, 11, 40 (+)-4,5-Deoxyneodolabelline, via ring-closing diene metathesis, 11, 219... 

In the early 1990s supported metallocenes were introduced to enable gas phase polymerisation. Also ethene/a-olefin copolymers with high comonomer content, cycloolefin copolymers and ethene-styrene interpolymers became available. In 1990 Stevens at Dow [22] discovered that titanium cy-clopentadienyl amido compounds (constrained geometry catalysts) are very beneficial for the copolymerisation of ethene and long-chain a-olefins. 

McKnight AL, Waymouth RM, Group 4 ansa-Cyclopentadienyl-Amido Catalysts for Olefin Polymerization, Chem Rev 98, 2587-2598 (1998), and refs therein... 

Abstract The synthesis and X-ray structure of various octahedral zirconium complexes and their catalytic properties in the polymerization of a-olefins are described. Benzamidinate, amido, allylic, and phosphinoamide moieties comprise the study ligations. For the benzamidinate complexes, a comparison study between homogeneous and heterogeneous complexes is presented. For the phosphinoamide complex, we show that the dynamic symmetry change of the complex from C2 to C2v allows the formation of elastomeric polymers. By controlling the reaction conditions of the polymerization process, highly stereoregular, elastomeric, or atactic polypropylenes can be produced. The formation of the elastomeric polymers was found to be the result of the epimerization of the last inserted monomer to the polymer chain. 

Thus, we have shown that, in addition to the known methyl and chloride ancillary ligands in zirconocenes, amido ligands can also be activated by strong Lewis acids such as MAO, producing cationic complexes active in the polymerization of tt-olefins. 

Gribkov, D.V., Hultzsch, K.C., and Hampel, F. (2003) Synthesis and characterization of new biphenolate and binaphtholate rare-earth-metal amido complexes catalysts for asymmetric olefin hydroamination/cyclization. Chemistry - A European Journal, 9, 4796. 

The stereospecific conversion of cyclohexene into the corresponding amido selenide 54 is illustrated in Scheme 8. These amidoselenenylation reactions are commonly employed for the preparation of allylic and saturated amides by oxidative or reductive deselenenylation. Propionitrile, butyronitrile, benzonitrile and ethyl cyanoacetate may be used in place of acetonitrile. Styrene gave poor results and other electron-rich olefins such as 1-methylcyclohexene or 2,3-di-methylbut-2-ene did not give the amidoselenenylation products. The reaction can also be effected starting from the hydroxy- or methoxyselenenylation products of alkenes, in the presence of water and trifluoromethanesulfonic acid in this case the nitriles are used in stoichiometric amounts [48c]. This methodology was employed to prepare the amidoselenenylation products of styrene, 55, and of electron-rich olefins. It was necessary, however, to replace the phenyl-... 

Mariano and coworkers have shown that DCN sensitized photoreaction of 268b in non-deoxygenated solutions leads to the efficient formation (75 %) of the corresponding pyrrolidone and not the azabicyclic product [315]. Earlier studies by Padwa et al. have shown that a-aminoalkyl radicals, unlike their a-amido analogs, do not add efficiently to unactivated olefins (Scheme 65) [316]. The a-silyl amines 277 connected to electron deficient olefins on the other hand, were found to undergo efficient DCN photosensitized cyclization in deaerated solutions to yield 278 and... 

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