Rhodium(i) complexes bearing N-donor ligands: catalytic activity towards intramolecular cyclization of alkynoic acids and ligand lability

Man, Bradley Yat‐Wah; Bhadbhade, Mohan; Messerle, Barbara A.

doi:10.1039/c1nj20094a

Cited by 18 publications

(14 citation statements)

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“…As far as we are aware, L1 represents only the second example of a bis(pyrazolyl)methyl that decorates an aniline; the first was Manzano's (2‐NH 2 C 6 H 4 )CHpz* 2 . The related compounds (2‐ or 4‐NH 2 C 6 H 4 )Cpz 3 and (4‐NH 2 C 6 H 4 )CH 2 pz are also known.…”

Section: Resultsmentioning

confidence: 99%

Supramolecular Assembly of Metal‐Organic Tubes Constructed from the Ditopic Heteroscorpionate Ligand (4‐NH2C6H4)CHpz2 (pz = Pyrazol‐1‐yl) and Silver(I)

et al. 2015

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The possibility of constructing tubular metal-organic structures with aid of weak hydrogen-bonding interactions between suitably designed metallacycles was explored. For this purpose, the new heteroditopic ligand (4-NH 2 C 6 H 4 )CHpz 2 (L1) was prepared in good (75 %) yield by a one-pot procedure starting from commercial 4-acetamidobenzaldehyde. The equimolar reactions between L1 and various silver(I) salts gave the intended 1:1 complexes in which the metallacycles were assembled into tubes. However, the exact nature of the assem- [a] Scheme 1. Some heteroditopic heteroscorpionate ligands (top) and a sampling of supramolecular isomers formed after metal coordination (bottom). Results and Discussion SynthesisThe new ligand (4-H 2 NC 6 H 4 )CHpz 2 (L1) was prepared by two different routes, as summarized in Scheme 2. Of the two pathways, Method A (Scheme 2, top) is preferred, because a 75 % yield can be obtained after a one-pot, two-step reaction sequence starting from commercial and inexpensive reagents. The yield of the CoCl 2 -catalyzed Peterson rearrangement [16] between the aldehyde and S(O)pz 2 was improved by 10-20 % by using an excess of S(O)pz 2 (relative to cases in which a 1:1 stoichiometric ratio of reagents was used). It is also noted that the rate of hydrolysis of the intermediate, {4-[CH 3 C(O)NH]C 6 H 4 }-CHpz 2 , is greatly enhanced in aqueous solution with respect to in solvent mixtures (THF/water or methanol/water). That is, after monitoring of the amide deprotection reaction by TLC, the rate of hydrolysis was observed to increase with water content of the solvent mixture. The deprotection reaction did not proceed to any appreciable extent when mixtures of NaOH (or KOH) and the intermediate were heated at reflux in dry MeOH over the course of a day, but the reaction was complete within hours when only water was used as a solvent. The ligand has significant solubility in water and in basic solution; this slightly complicates its extraction into organic solvents. That is, yields can be artificially low if care is not taken to ensure complete extraction by using numerous aliquots of organic solvent (ethyl acetate was particularly effective) and by checking the aqueous layer for product by TLC.

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Section: Resultsmentioning

confidence: 99%

Supramolecular Assembly of Metal‐Organic Tubes Constructed from the Ditopic Heteroscorpionate Ligand (4‐NH2C6H4)CHpz2 (pz = Pyrazol‐1‐yl) and Silver(I)

et al. 2015

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“…Messerle and co‐workers first reported the cyclization of alkynoic acids in 2011 . In this initial report, neutral tris(pyrazol‐1‐yl)toluidine (tpt) and tris( N ‐methylimidazol‐2‐yl)methanol (tim) ligands were examined (Figure ).…”

Section: Hydroalkoxylation Of Alkynesmentioning

confidence: 99%

“…A series of six cationic complexes, [Rh( p ‐tpt)(L 2 )](B Ar F ) and [Rh( o ‐tpt)(L 2 )](B Ar F ) {B Ar F = tetrakis[3,5‐bis(trifluoromethyl)phenyl]borate, L = 1,5‐cyclooctadiene (COD), norbornadiene (NBD), CO}, were synthesized from the corresponding [Rh(L 2 )](B Ar F ) complexes in yields ranging from 58–98 %. [Rh(tim)(L 2 )](B Ar F ) complexes (L 2 = COD, CO) were also synthesized in the same manner in 70 % and 57 % yield respectively …”

Section: Hydroalkoxylation Of Alkynesmentioning

confidence: 99%

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Hydroelementation of Unsaturated C–C Bonds Catalyzed by Metal Scorpionate Complexes

Wathier

Love

2016

Eur J Inorg Chem

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Tridentate scorpionate ligands have a rich history in coordination chemistry. In the past two decades, metal complexes bearing scorpionate ligands have found increasing utility as catalysts for a variety of useful transformations. This microreview focuses on the utility of scorpionate ligands in hydro- [a] 2396 Scheme 13. Proposed mechanism for To M Mg-mediated aminoalkene hydroamination (see ref. [54] ).

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“…A step forward in the synthesis of camphor derived Cu(I) coordination polymers was to build copper polymers with two, rather than one CuCl strings, linked by the convenient camphor derivatives aiming at studying their properties as catalysts, a field where coordination polymers are high promising . Cyclization processes seemed promising since Pd(II) and Pt(II) camphor complexes were found to be high active in the cyclization of alkynes or alkynols and there is a current interest on efficient catalysts that promote the cyclization of functionalized alkynes alkynols or alkyne carboxylic acids within cyclization processes that encompass purely organic or metal mediated methodologies. Catalysts developed up to now are based on expensive transition metals (Pd, Pt, Au, or Ag) and require strong basic conditions.…”

Section: Introductionmentioning

confidence: 99%

Cu(I) camphor coordination polymers: Synthesis and study of the catalytic activity for cyclization of 4‐pentyn‐1‐oic acid

Fernandes

Galvão

Rego

et al. 2014

J. Polym. Sci. Part A: Polym. Chem.

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The number of CuCl units per camphor ligand in [{CuCl} 2 L] n was extended to three or four in [{CuCl} 3 L] n (2) or [{CuCl} 4 L] n (1). The Hartree-Fock ab initio calculations support the polymeric structure of 1 and 2 that catalyze the cyclization of 4-pentyn-1-oic acid (A) forming 5-methylenedihydrofuran-2(3H)-one (B) and/or 2-methyl-5-oxotetrahydrofuran-2-ylpent-4-ynoate (C). The catalytic activity of 1, 2 and other polynuclear Cu(I) complexes (3-5) was evaluated under solvent free conditions and/or solution. In the absence of solvent, catalyst 2 displays the highest activity and selectivity (75.8/23.1, C to B ratio, at 5.4% loading) while 4 reaches the highest level of A ! B conversion (97.5 %) in solution. Selected reactions were followed by NMR and the kinetic constants calculated. A mechanism is proposed based on the equations used for the calculations.

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Rhodium(i) complexes bearing N-donor ligands: catalytic activity towards intramolecular cyclization of alkynoic acids and ligand lability

Cited by 18 publications

References 49 publications

Supramolecular Assembly of Metal‐Organic Tubes Constructed from the Ditopic Heteroscorpionate Ligand (4‐NH2C6H4)CHpz2 (pz = Pyrazol‐1‐yl) and Silver(I)

Supramolecular Assembly of Metal‐Organic Tubes Constructed from the Ditopic Heteroscorpionate Ligand (4‐NH2C6H4)CHpz2 (pz = Pyrazol‐1‐yl) and Silver(I)

Hydroelementation of Unsaturated C–C Bonds Catalyzed by Metal Scorpionate Complexes

Cu(I) camphor coordination polymers: Synthesis and study of the catalytic activity for cyclization of 4‐pentyn‐1‐oic acid

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