Intramolecular Hydroamination Of Unactivated Alkenes Research Articles

Intramolecular Hydroamination by a Primary Amine of an Unactivated Alkene on Gold Nanoclusters: A DFT Study

AbstractDensity functional theory calculations have been used to investigate the mechanism of intramolecular hydroamination of unactivated alkenes by using primary amines on gold nanoclusters (NCs) under aerobic conditions. By examining the activation modes in the cyclization process, the olefin activation mechanism was calculated to be the most energetically feasible of the three possible pathways. The amine activation pathway suffered from a high activation barrier, which means that this pathway is unlikely to take place on gold NCs. The catalytic cycle comprises five elementary steps: (1) adsorption of O2 on Au NCs results in superoxo‐like species and provides Lewis acidic sites that allow the nucleophilic substrate, 2,2‐diphenyl‐4‐penten‐1‐amine, to be adsorbed effectively; (2) intramolecular cyclization (C−N bond formation) takes place on the Au NCs through anti‐addition of the amino group; (3) hydroperoxy moiety formation by hydrogen transfer from the cyclic intermediate to superoxo‐like species; (4) the formation of hydrogen peroxide and (5) product involves hydrogen transfer from a hydrated formic acid. Natural bond orbital analysis of the transition states that arise during C−N bond formation reveals that anti‐addition of the substrate is preferred over the syn‐addition mechanism. A possible side reaction, the formation of 2‐methylene‐4,4‐diphenylpyrrolidine through β‐hydrogen elimination, is also discussed.

Brønsted acid-catalysed intramolecular hydroamination of unactivated alkenes: metal triflates as an in situ source of triflic acid

Hydroamination of alkenes or alkynes is one of the most straightforward methods to form C-N bonds and nitrogen-containing heterocycles. A simple Lewis acid Al(OTf)3 was found to be an effective precatalyst for the hydroamination of unactivated primary and secondary alkenylamines between 110 and 150 °C. Subsequent studies show that other metal triflates are also effective precatalysts for the hydroamination reactions. For metal triflate salts, mechanistic studies, including kinetics, are consistent with the in situ generation of triflic acid, which likely serves as the active catalyst.

ChemInform Abstract: Enantioselective Intramolecular Hydroamination of Unactivated Alkenes Catalyzed by Mono‐ and Bis(gold) Phosphine Complexes.

AbstractThe title process allows the cyclization of unactivated alkenes with carbamates and ureas to form pyrrolidine derivatives with enantioselectivities up to 85%.

Enantioselective Intramolecular Hydroamination of Unactivated Alkenes Catalyzed by Mono‐ and Bis(gold) Phosphine Complexes

AbstractA 1:2 mixture of (P1)(AuCl)2 [P1=(S)‐DTBM‐MeO‐BIPHEP] and silver tetrafluoroborate (AgBF4) in methanol catalyzes the intramolecular hydroamination of unactivated alkenes with carbamates and ureas to form pyrrolidine derivatives with up to 85% ee.magnified image

ChemInform Abstract: CCC—N‐Heterocyclic Carbene Pincer Complexes: Synthesis, Characterization and Hydroamination Activity of a Hafnium Complex.

AbstractThe hafnium compound HFC effectively promotes the intramolecular hydroamination of unactivated alkenes yielding pyrrolidine and piperidine derivatives.

ChemInform Abstract: Intramolecular Hydroamination of Unactivated Alkenes with Secondary Alkylamines Catalyzed by Iridium Phosphino—Phenolate Complexes.

AbstractA new iridium phosphino—phenolate complex is an effective precatalyst for the intramolecular hydroamination of unactivated alkenes with pendant secondary alkylamines, providing either pyrrolidine or piperidine heterocycles in high yields.

Inter‐ and Intramolecular Hydroamination of Unactivated Alkenes Catalysed by a Combination of Copper and Silver Salts: The Unveiling of a Brønstedt Acid Catalysis

AbstractThe combined use of a copper halide, a silver salt and a phosphane ligand was applied for the catalysis of inter‐ and intramolecular hydroamination of alkenes. The reactions of unactivated olefins with nitrogen substrates were investigated. Mechanistic investigations demonstrated that the catalytic system generated a Brønsted acid which appeared to be the prominent catalytic species.

Intramolecular hydroamination of unactivated alkenes with secondary alkylamines catalyzed by iridium phosphino–phenolate complexes

The phosphino–phenolate complex (κ2-{2-i-Pr2PC6H4}O)Ir(COD) (COD = η4-1,5-cyclooctadiene; 1) is shown to be an effective precatalyst for the intramolecular hydroamination of unactivated alkenes with pendant secondary alkylamines, providing either pyrrolidine or piperidine heterocycles in high isolated yields. While monitoring the progress of a selected test reaction of this type, a significant induction period (~3 h) was observed; variable-temperature 1H and 31P NMR studies (25–100 °C) under catalytically relevant conditions revealed no new metal-containing species. In an effort to develop an enantiopure variant of 1, a synthetic route to the chiral (κ2-P,O)Ir(COD) complex (7), which features a 1-aryl-2,5-dialkylphospholane structure derived from (2S,5S)-2,5-hexanediol cyclic sulfate, was developed. The structure of 7 was confirmed by use of single-crystal X-ray diffraction techniques. While 7 failed to provide enantioselectivity in the intramolecular hydroamination of unactivated alkenes with pendant secondary alkylamines, the activity of 7 was found to be comparable to that of 1.

ChemInform Abstract: [Ir(COD)Cl]2 as a Catalyst Precursor for the Intramolecular Hydroamination of Unactivated Alkenes with Primary Amines and Secondary Alkyl‐ or Arylamines: A Combined Catalytic, Mechanistic, and Computational Investigation.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Ir(COD)Cl]2 as a Catalyst Precursor for the Intramolecular Hydroamination of Unactivated Alkenes with Primary Amines and Secondary Alkyl- or Arylamines: A Combined Catalytic, Mechanistic, and Computational Investigation

The successful application of [Ir(COD)Cl](2) as a precatalyst for the intramolecular addition of primary as well as secondary alkyl- or arylamines to unactivated olefins at relatively low catalyst loading is reported (25 examples), along with a comprehensive experimental and computational investigation of the reaction mechanism. Catalyst optimization studies examining the cyclization of N-benzyl-2,2-diphenylpent-4-en-1-amine (1a) to the corresponding pyrrolidine (2a) revealed that for reactions conducted at 110 degrees C neither the addition of salts (N(n)Bu(4)Cl, LiOTf, AgBF(4), or LiB(C(6)F(5))(4) x 2.5 OEt(2)) nor phosphine coligands served to enhance the catalytic performance of [Ir(COD)Cl](2). In this regard, the rate of intramolecular hydroamination of 1a employing [Ir(COD)Cl](2)/L2 (L2 = 2-(di-t-butylphosphino)biphenyl) catalyst mixtures exhibited an inverse-order dependence on L2 at 65 degrees C, and a zero-order rate dependence on L2 at 110 degrees C. However, the use of 5 mol % HNEt(3)Cl as a cocatalyst was required to promote the cyclization of primary aminoalkene substrates. Kinetic analysis of the hydroamination of 1a revealed that the reaction rate displays first order dependence on the concentration of Ir and inverse order dependence with respect to both substrate (1a) and product (2a) concentrations; a primary kinetic isotope effect (k(H)/k(D) = 3.4(3)) was also observed. Eyring and Arrhenius analyses for the cyclization of 1a to 2a afforded DeltaH(double dagger) = 20.9(3) kcal mol(-1), DeltaS(double dagger) = -23.1(8) cal/K x mol, and E(a) = 21.6(3) kcal mol(-1), while a Hammett study of related arylaminoalkene substrates revealed that increased electron density at nitrogen encourages hydroamination (rho = -2.4). Plausible mechanisms involving either activation of the olefin or the amine functionality have been scrutinized computationally. An energetically demanding oxidative addition of the amine N-H bond to the Ir(I) center precludes the latter mechanism and instead activation of the olefin C=C bond prevails, with [Ir(COD)Cl(substrate)] M1 representing the catalytically competent compound. Notably, such an olefin activation mechanism had not previously been documented for Ir-catalyzed alkene hydroamination. The operative mechanistic scenario involves: (1) smooth and reversible nucleophilic attack of the amine unit on the metal-coordinated C=C double bond to afford a zwitterionic intermediate; (2) Ir-C bond protonolysis via stepwise proton transfer from the ammonium unit to the metal and ensuing reductive elimination; and (3) final irreversible regeneration of M1 through associative cycloamine expulsion by new substrate. DFT unveils that reductive elimination involving a highly reactive and thus difficult to observe Ir(III)-hydrido intermediate, and passing through a highly organized transition state structure, is turnover limiting. The assessed effective barrier for cyclohydroamination of a prototypical secondary alkylamine agrees well with empirically determined Eyring parameters.

ChemInform Abstract: Intramolecular Hydroamination of Unactivated Alkenes with Secondary Alkyl‐ and Arylamines Employing [Ir(COD)Cl]2 as a Catalyst Precursor.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Cu(I)-Catalyzed Intramolecular Hydroamination of Unactivated Alkenes Bearing a Primary or Secondary Amino Group in Alcoholic Solvents

The Cu-Xantphos system [Cu(O-t-Bu)-Xantphos, 10-15 mol %] catalyzes the intramolecular hydroamination of unactivated terminal alkenes bearing an unprotected aminoalkyl substituent in alcoholic solvents, giving pyrrolidine and piperidine derivatives in excellent yields. This system is applicable to both primary and secondary amines and tolerates a variety of functional groups.

Intramolecular Hydroamination of Unactivated Alkenes with Secondary Alkyl- and Arylamines Employing [Ir(COD)Cl]2 as a Catalyst Precursor

Commercially available [Ir(COD)Cl](2) is an effective precatalyst for the intramolecular hydroamination of a range of unactivated alkenes with pendant secondary alkyl- or arylamines, at relatively low loadings (typically 0.25-5.0 mol % Ir) and without the need for added ligands or other cocatalysts.

Gold(I)‐Catalyzed Intramolecular Hydroamination of Unactivated Alkenes with Carboxamides.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Room Temperature Palladium‐Catalyzed Intramolecular Hydroamination of Unactivated Alkenes.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Room Temperature Palladium-Catalyzed Intramolecular Hydroamination of Unactivated Alkenes

A mild and facile Pd-catalyzed intramolecular hydroamination of unactivated alkenes is described. This reaction takes place at room temperature and is tolerant of synthetically useful acid-sensitive functional groups. The formation of hydroamination products rather than oxidative amination products is due to the use of a tridentate ligand on Pd which effectively inhibits beta-hydride elimination.

Gold(i)-catalyzed intramolecular hydroamination of unactivated alkenes with carboxamides

N-Alkenyl carboxamides undergo gold-catalyzed intramolecular exo-hydroamination to form nitrogen heterocycles in excellent yield.

Efficient Intramolecular Hydroamination of Unactivated Alkenes Catalysed by Butyllithium

AbstractIn this communication, we wish to report some preliminary results demonstrating, for the first time, that intramolecular hydroamination of unactivated alkenes can be performed efficiently using small quantities of nBuLi as the pre‐catalyst. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003