9‐Fluor‐9‐borabicyclo[3.3.1]nonan ‐ Charakterisierung in Lösung und im Kristall

Köster, Roland; Schüßler, Wilhelm; Boese, Roland

doi:10.1002/cber.19901231004

Cited by 18 publications

(8 citation statements)

References 30 publications

(3 reference statements)

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“…Reaction of 2 with Tr + BF 4 – gave a mixture of products by 11 B NMR, the major components being 9-fluoro-9-borabicyclo[3.3.1]nonane and PMAF-BF 3 . The former was identified as a doublet at 62 ppm ( 1 J BF = 126 Hz), in agreement with literature data . Other minor components were (C 8 H 14 B) 2 O (58 ppm) and C 8 H 15 BF 2 (29 ppm) both being known hydrolysis products of 9-fluoro-9-borabicyclo[3.3.1]nonane (9-BBNF) that we assume form due to presence of trace water .…”

Section: Resultssupporting

confidence: 87%

Formation, Stability, and Structures of Borenium and Boronium Cations Derived from Pentamethylazaferrocene–Boranes by Hydride or Chloride Abstraction Reactions

et al. 2014

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Hydride abstraction reactions from 1′,2′,3′,4′,5′-pentamethylazaferrocene−boranes (PMAF-boranes, where borane = BH 3 , 9-bora[3.3.1]bicyclononane) using trityl cation in CH 2 Cl 2 yielded the corresponding borenium cations, whose stability depends on the counteranion of the trityl salt. If the [BF 4 ] − salt was employed, then fluoride abstraction from the anion occurred immediately, yielding PMAF-BF 3 and other identifiable byproducts. If the [B(C 6 F 5 ) 4 ] − salt was employed, then the borenium ions were stable in solution at room temperature and could be characterized by 1 H, 13 C, and 11 B NMR spectroscopy. Double hydroboration of [PMAF-BH 2 ] + with 1,5-cycloooctadiene yields the borenium ion of PMAF-9-bora[3.3.1]-bicyclononane, [PMAF-9BBN] + . Reaction of [PMAF-BH 2 ] + with excess PMAF yields the boronium cation [(PMAF) 2 BH 2 ] + , which was isolated and crystallographically characterized as its [B(C 6 F 5 ) 4 ] − salt. Reaction of [PMAF-9BBN] + with 2 equiv of N-methylimidazole leads to the boronium cation [(N-methylimidazole) 2 (BBN)] + , which was also isolated and crystallographically characterized as its [B(C 6 F 5 ) 4 ] − salt. Chloride abstraction from PMAF-BCl 3 with AlCl 3 in CH 2 Cl 2 yielded the borenium cation [PMAF-BCl 2 ] + , which was characterized in solution by 1 H, 13 C, and 11 B NMR spectroscopy. A single-crystal X-ray structure was also obtained of [PMAF-BCl 2 ] + [AlCl 4 ] − , revealing structural changes upon borenium ion formation, including rehybridization of the B center and a bending of the BCl 2 moiety toward the Fe center. The Lewis acidity of all three borenium cations was assessed by the Gutmann−Beckett method, and [PMAF-BH 2 ] + was found to be more acidic than B(C 6 F 5 ) 3 . DFT calculations were performed on [PMAF-BH 2 ] + using the BP86 method with the LANL2DZ basis set for Fe and the TZVP basis set for C, H, N, and B. The optimized structure revealed substantial bending of the BH 2 moiety toward Fe with a dip angle of −23.7°. Inspection of the frontier MOs reveal that the electrophilic B center is stabilized through delocalized interactions that involve orbitals on Fe, the pyrrolyl ring, and the pentamethylcyclopentadienyl ring.

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Section: Resultssupporting

confidence: 87%

Formation, Stability, and Structures of Borenium and Boronium Cations Derived from Pentamethylazaferrocene–Boranes by Hydride or Chloride Abstraction Reactions

et al. 2014

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“…A thallium derivative (R = tetrafluorophenyl, W = Tl, Z = Cl with extra coordination on each Tl from one Ph 3 PO) shows a significantly unsymmetric Tl ؒ ؒ ؒ Cl ؒ ؒ ؒ Tl bridge (2.54, 2.94), 33 and the most unusual example of this asymmetry is revealed in a R 2 B-F system, where a single B ؒ ؒ ؒ F ؒ ؒ ؒ B bridging dimer is formed, with B-F bond lengths of 1.43 and 1.65 Å. 34 From the more extensive crystal data reported for the Group III elements, we can draw an inference that asymmetry in the dimeric bridges can be possible, and that using sterically large R groups can inhibit bridge formation.…”

Section: Structures Of the Reactants Rrјi-zmentioning

confidence: 99%

An ab initio and MNDO-d SCF-MO computational study of stereoelectronic control in extrusion reactions of R2I–F iodine(III) intermediates†

Carroll¹,

Martín‐Santamaría²,

Pike³

et al. 1999

J. Chem. Soc., Perkin Trans. 2

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“…The KHF 2 reagent in MeOH gave only 9 % conversion after 24 h (Table , entry 1). This was surprising, as this reagent is used to convert boronic acids into the corresponding potassium organotrifluoroborates SbF 3 was reported in the successful conversion of the 9‐BBN hydride‐bridged dimer into the monofluoride analogue in heptane . Owing to the insolubility of 2a in heptane, the reaction was instead performed in MeCN.…”

Section: Resultsmentioning

confidence: 99%

Tetrabutylammonium Fluoride as a Mild and Versatile Reagent for Cleaving Boroxazolidones to Their Corresponding Free α‐Amino Acids

Poulie

Bunch

2017

Eur J Org Chem

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Protection of α‐amino acids with 9‐borabicyclo[3.3.1]nonane (9‐BBN) to give their corresponding boroxazolidones is highly attractive, as it concurrently masks both the amino and the carboxylic acid functionalities. However, the harsh methods required for deprotection of these boroxazolidones have limited their use. Herein, we report that tetrabutylammonium fluoride serves as a mild and versatile reagent that can be used to cleave boroxazolidones to their corresponding free α‐amino acids. The reaction conditions were explored, including the use of various nucleophilic fluoride sources, solvents, and reaction temperatures. Nucleophilic fluoride sources comprising an ammonium cation proved superior to other countercations. The scope of the reaction was extended to the cleavage of B,B‐diphenyl‐ and B,B‐diethyl boroxazolidone complexes. Furthermore, a wide range of α‐amino acid side‐chain functionalities were shown to be compatible, including acids, esters, amides, thiols, thioethers, alkynes, phenols, basic heterocycles, and important biorelevant molecules such as glutathione, (S)‐adenosyl‐l‐homocysteine, and l‐biocytin.

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9‐Fluor‐9‐borabicyclo[3.3.1]nonan ‐ Charakterisierung in Lösung und im Kristall

Cited by 18 publications

References 30 publications

Formation, Stability, and Structures of Borenium and Boronium Cations Derived from Pentamethylazaferrocene–Boranes by Hydride or Chloride Abstraction Reactions

Formation, Stability, and Structures of Borenium and Boronium Cations Derived from Pentamethylazaferrocene–Boranes by Hydride or Chloride Abstraction Reactions

An ab initio and MNDO-d SCF-MO computational study of stereoelectronic control in extrusion reactions of R2I–F iodine(III) intermediates†

Tetrabutylammonium Fluoride as a Mild and Versatile Reagent for Cleaving Boroxazolidones to Their Corresponding Free α‐Amino Acids

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