Zirconium‐Mediated Conversion of Amides to Nitriles: A Surprising Additive Effect

Ruck, Rebecca T.; Bergman, Robert G.

doi:10.1002/anie.200461064

Cited by 43 publications

(21 citation statements)

References 8 publications

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“…Adducts 1k, 1o, and 1p exhibit a short Ti-N imido distance of 1.6955(18) Å for 1k, 1.7028(11) Å for 1o, and 1.700(2) Å for 1p. The imido linkage is almost linear [Ti-N imido -C ipso angle = 178.21 (15), 178.86(10), and 169.4(2)°, respectively, in 1k, 1o, and 1p], and is consistent with the donation of the lone pair on nitrogen to an acceptor orbital on titanium (the imido Ti-N bond can be considered as a triple bond). The crystal structure determinations also unambiguously show noninteracting functional -NEt 2 (1k), -C(Me)=CH 2 (1o), and -CϵCH (1p) groups, with normal metric parameters that are listed in Table 1.…”

Section: General Synthesis Of the Imido Complexes [Ti(=nr)-cl 2 (Nhmementioning

confidence: 63%

“…in alkene metathesis [3] or olefin polymerization [1c,4-6] ), (2) reactions in which the M = NR linkage itself is involved in stoichiometric or catalytic transformations such as metathesis reactions (with imines, [7] nitro-and nitrosoarenes, [8] or oxo-imido exchange [9] ), C-H activation, [10] reactions with unsaturated C-C [11] or C-X bonds, [12] alkyne hydroaminations, [13,14] carboamination reactions, [15] and ring-opening reactions of strained heterocycles.…”

Section: Introductionmentioning

confidence: 99%

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A General and Facile One‐Step Synthesis of Imido–Titanium(IV) Complexes: Application to the Synthesis of Compounds Containing Functionalized or Chiral Imido Ligands and Bimetallic Diimido Architectures

2006

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One‐pot reactions of Ti(NMe2)4 with a wide range of primary alkyl, aryl, and silylamines RNH2 in the presence of excess chlorotrimethylsilane produced the corresponding imido–titanium(IV) complexes [Ti(=NR)Cl2(NHMe2)2] (1a–j), in which R = tBu, 1‐adamantane, Ph3C, Ph3Si, Ph, 2,6‐iPr2–C6H3, 2,6‐Cl2–C6H3, 2,6‐Br2–4‐Me–C6H2, C6F5, and 3,5‐(F3C)2–C6H3. This general synthesis, which starts from commercially available reagents, represents a simple and direct route to imido complexes. Reaction of complexes 1 with pyridine afforded the six‐coordinate tris‐pyridine adducts [Ti(=NR)Cl2(Py)3] (2). Another advantage of this method is its tolerance to other functional groups; complexes that contain halides, ether, dialkylamino, cyano, ethynyl, olefin, and nitro substituents on the imido moiety have been prepared. The use of enantiomerically pure primary amines affords the first group of titanium complexes that contain chiral imido groups, and the use of diamines produces diimido complexes. Alternatively, CH3I has been used as an alkylating agent to generate titanium–imido complexes of the type [Ti(NR)I2(THF)2]2. All compounds were fully characterized by spectroscopic methods (IR, 1H NMR, 13C NMR) and elemental analysis. Some of the compounds were also analyzed by single‐crystal X‐ray diffraction studies. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

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Section: General Synthesis Of the Imido Complexes [Ti(=nr)-cl 2 (Nhmementioning

confidence: 63%

Section: Introductionmentioning

confidence: 99%

A General and Facile One‐Step Synthesis of Imido–Titanium(IV) Complexes: Application to the Synthesis of Compounds Containing Functionalized or Chiral Imido Ligands and Bimetallic Diimido Architectures

2006

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“…Another four structures report complexes with chemically similar amides, viz. three with benzamide (Ruck & Bergman, 2004;Buil et al, 2012;Kim et al, 1993) and one with 2,2-diphenylacetamide (Becker et al, 2014). None of the reported acetamide complexes have an easily accessible acetate counterpart for comparison.…”

Section: Introductionmentioning

confidence: 99%

Acetate and acetamide complexes of [Ni(Me₄[12]aneN₄)]PF₆: a tale of two ligands

2014

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Although there are many examples of acetate complexes, acetamide complexes are virtually unknown. A side-by-side comparison in (acetato-κ(2)O,O')(1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane-κ(4)N)nickel(II) hexafluoridophosphate, [Ni(C2H3O2)(C12H28N4)]PF6, (1), and (acetamidato-κ(2)O,O')(1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane-κ(4)N)nickel(II) hexafluoridophosphate, [Ni(C2H4NO)(C12H28N4)]PF6, (2), shows the steric equivalence between these two ligands, suggesting that acetamide could be considered as a viable acetate replacement for electronic tuning.

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“…Use of the PMP group as a substituent on the nitrogen atom is particularly attractive, since nucleophilic addition to or reduction of the product PMP-imine provides a p-methoxyphenyl-protected primary amine, which may be liberated under mild oxidative conditions. [16] We have employed methylzirconocene (p-methoxyphenyl)amide (18) as the catalyst in the carboamination reaction between imine 15e and alkyne 16a to generate α,β-unsaturated imine product 17e in 75% yield (Scheme 4). [17] This yield is comparable to that obtained with azazirconacyclobutene 14c as catalyst (Table 1, entry 5).…”

mentioning

confidence: 99%

“…A related paper that reports the insertion of Nacylamines into azazirconacyclobutenes also appears in this issue. [18] Scheme 1. …”

mentioning

confidence: 99%

Carboamination: Additions of Imine CN Bonds Across Alkynes Catalyzed by Imidozirconium Complexes

Ruck

Zuckerman²,

Krska

et al. 2004

Angewandte Chemie

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The development of new reactions employing imidozirconium complexes or their derivatives as catalysts is an elusive goal in organometallic chemistry. To date, the imidozirconocenecatalyzed hydroamination of alkynes and allenes to yield new enamines (and, on tautomerization, imines) is the lone example of such a process. [1,2] We recently reported that aldehydes and electron-deficient imines insert into the carbon-zirconium bond of azazirconacyclobutene 1 to afford new six-membered ring metallacycles 2 and 3 (see Scheme 1). On heating, these expanded zirconacycles undergo a retro-[4+2] cycloaddition to afford α,β-unsaturated imine 4 and oxozirconium complex 5 or electron-poor imidozirconocene dimer 6, both of which are unreactive (Scheme 1; EWG =electron-withdrawing group, Cp = C 5 H 5 ). [3,4] We reasoned that insertion of an aldimine 7 with N-substitution identical to that of the nitrogen group in the metallacyclobutene, followed by subsequent retro-cycloaddition, would not only afford α,β-unsaturated imine 4 but would also generate imidozirconocene complex 8 previously used to prepare the starting azazirconacyclobutene (see Scheme 2).[5] Carrying out the reaction in the presence of the necessary alkyne would regenerate the starting metallacycle and close the catalytic cycle (Scheme 2).[6] This reaction is deemed a carboamination, because it results in the overall cleavage of an imine C=N bond and addition of the resulting C and N fragments across an alkyne, forming a new carbon-carbon double bond and a new ketimine carbon-nitrogen double bond. [7][8][9] Herein, we present the development of a novel, high-yielding imidozirconocene-catalyzed carboamination reaction that also represents the best method for preparing the highly arylated α,β-unsaturated imine co-products.The most frequently studied imidozirconium complexes bear sterically bulky groups on the nitrogen atom to prevent competitive dimerization of the imido compound.[5] As such, N-2,6-dimethylphenyl-and N-tert-butyl-substituted azazirconacyclobutenes 1 and 9 (see Scheme 3) were explored in the desired insertion chemistry. Unfortunately, even at high concentrations of substrate and temperatures up to 165°C, neither of these zirconium compounds was an effective catalyst as no imine insertion products were observed. In the case of metallacycle 1 and imine 10, it appears that the combined steric bulk of the zirconacycle and imine Nsubstituents prohibits insertion; with metallacycle 9 and N-tert-butyl imine 11, we began to observe C-D bond activation of the [D 6 ]benzene solvent. Presumably, this pathway arises from

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Zirconium‐Mediated Conversion of Amides to Nitriles: A Surprising Additive Effect

Cited by 43 publications

References 8 publications

A General and Facile One‐Step Synthesis of Imido–Titanium(IV) Complexes: Application to the Synthesis of Compounds Containing Functionalized or Chiral Imido Ligands and Bimetallic Diimido Architectures

A General and Facile One‐Step Synthesis of Imido–Titanium(IV) Complexes: Application to the Synthesis of Compounds Containing Functionalized or Chiral Imido Ligands and Bimetallic Diimido Architectures

Acetate and acetamide complexes of [Ni(Me₄[12]aneN₄)]PF₆: a tale of two ligands

Carboamination: Additions of Imine CN Bonds Across Alkynes Catalyzed by Imidozirconium Complexes

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Zirconium‐Mediated Conversion of Amides to Nitriles: A Surprising Additive Effect

Cited by 43 publications

References 8 publications

A General and Facile One‐Step Synthesis of Imido–Titanium(IV) Complexes: Application to the Synthesis of Compounds Containing Functionalized or Chiral Imido Ligands and Bimetallic Diimido Architectures

A General and Facile One‐Step Synthesis of Imido–Titanium(IV) Complexes: Application to the Synthesis of Compounds Containing Functionalized or Chiral Imido Ligands and Bimetallic Diimido Architectures

Acetate and acetamide complexes of [Ni(Me4[12]aneN4)]PF6: a tale of two ligands

Carboamination: Additions of Imine CN Bonds Across Alkynes Catalyzed by Imidozirconium Complexes

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Acetate and acetamide complexes of [Ni(Me₄[12]aneN₄)]PF₆: a tale of two ligands