Deprotection of pinacolyl boronate esters via hydrolysis of intermediate potassium trifluoroborates

Yuen, Alexander K. L.; Hutton, Craig A.

doi:10.1016/j.tetlet.2005.09.101

Cited by 148 publications

(91 citation statements)

References 23 publications

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“…Although aryltrifluoroborate stability has been attributed to the B-F bond strength, solvolytic defluoridation of the aryltrifluoroborate has been invoked as a necessary first step in transition metal mediated cross-coupling. That said, the stability of aryltrifluoroborates has been only briefly studied with sparse evidence as to rate of solvolytic defluoridation, which must ultimately regenerate the arylboronic acid via partially fluorinated species thereof [5][6][7][8][9]. In light of the extensive use of boronic esters and aryltrifluoroborates in synthetic chemistry, arylboronic acids represent potential captors of aqueous [ 18 F]-fluoride that would conveniently provide [ 18 F]-labeled PET-imaging agents composed of a pendant aryl-[ 18 F]-trifluoroborate [10].…”

Section: Introductionmentioning

confidence: 99%

Capturing aqueous [18F]-fluoride with an arylboronic ester for PET: Synthesis and aqueous stability of a fluorescent [18F]-labeled aryltrifluoroborate

Ting

Adam

et al. 2008

Journal of Fluorine Chemistry

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Section: Introductionmentioning

confidence: 99%

Capturing aqueous [18F]-fluoride with an arylboronic ester for PET: Synthesis and aqueous stability of a fluorescent [18F]-labeled aryltrifluoroborate

Ting

Adam

et al. 2008

Journal of Fluorine Chemistry

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“…Results from our group and others [6,7] indicated that low-resolution LC-ESIMS operating in the negative ion mode allowed observation of the molecular anions of interest. However, this method does not provide the high degree of accuracy required for the determination of elemental composition.…”

mentioning

confidence: 81%

Accurate mass determination of organotrifluoroborates

Petrillo

Kohli

Molander

2007

J. Am. Soc. Mass Spectrom.

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Exact mass measurements were obtained for a variety of potassium-and tetra-n-butylammonium organotrifluoroborates using commercially available organic sulfate salts as internal reference standards. Accuracies were determined within 5 ppm using a sector ESI mass spectrometer operating in the negative ionization mode. (J Am Soc Mass Spectrom 2007, 18, 404 -405) © 2007 American Society for Mass Spectrometry P olar, nonvolatile compounds of low molecular weight can be difficult to characterize by highresolution mass spectrometry (HRMS), although they often ionize well using electrospray mass spectrometry (ESIMS) [1]. Specifically, the determination of accurate mass below 300 amu is hindered because of the lack of commercially available reference standards when using sector instruments. Common reference standards such as cesium iodide [2,3] and sodium trifluoroacetate [4] provide suitable negative ions, but the peaks often are spaced too far apart for accurate mass determination when using a sector analyzer. Therefore a need exists for a set of readily available reference standards that can be applied to the characterization of polar molecules of low molecular weight.As part of an ongoing research program in organoboron chemistry [5], we required HRMS data on several novel potassium-and tetra-n-butylammonium organotrifluoroborates (RBF 3 K and RBF 3 ONBu 4 ) for complete characterization. Results from our group and others [6,7] indicated that low-resolution LC-ESIMS operating in the negative ion mode allowed observation of the molecular anions of interest. However, this method does not provide the high degree of accuracy required for the determination of elemental composition. Although HRMS data have been obtained on similar compounds using fast atom bombardment (FAB) [8], such instrumentation was not readily available to us and thus we sought a method that could be implemented with the instrumentation on hand.We reasoned that other low molecular weight compounds that easily form negative ions would act as suitable standards. Polyethylene glycol sulfates have been used in the past as internal standards for HRMS, albeit for larger molecules [2]. Smaller sulfate salts such as sodium alkyl sulfates (RSO 4 Na) are readily available in the molecular weight range that we desired and differ by a methylene unit (14 Da), making it easy to bracket the molecular ion under examination. We chose to explore these compounds as potential internal reference standards. ExperimentalMass spectra were obtained on a Micromass Autospec with a double-focusing magnetic sector analyzer operating in the negative electrospray ionization mode. Opus MassLynx version 3.5 software was used for analysis. Analytes and reference standards were introduced by infusion as solutions in methanol. Sodium ethyl sulfate and sodium n-propyl sulfate were purchased from City Chemical (West Haven, CT). All other standards were purchased from Alfa Aesar (Ward Hill, MA). Potassium-and tetra-n-butylammonium trifluoroborates were synthesized by standard methods [5]....

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“…In addition, the facile interconversion [18,31,32] between boronic acids, boronic esters and trifluoroborates is extremely attractive since one can utilize whichever precursor is most effective when considering radiopharmaceutical preparations.…”

Section: Introductionmentioning

confidence: 99%

No-carrier-added radiohalogenations utilizing organoboranes: The synthesis of iodine-123 labeled curcumin

Kabalka¹,

Yao²

2009

Journal of Organometallic Chemistry

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Deprotection of pinacolyl boronate esters via hydrolysis of intermediate potassium trifluoroborates

Cited by 148 publications

References 23 publications

Capturing aqueous [18F]-fluoride with an arylboronic ester for PET: Synthesis and aqueous stability of a fluorescent [18F]-labeled aryltrifluoroborate

Capturing aqueous [18F]-fluoride with an arylboronic ester for PET: Synthesis and aqueous stability of a fluorescent [18F]-labeled aryltrifluoroborate

Accurate mass determination of organotrifluoroborates

No-carrier-added radiohalogenations utilizing organoboranes: The synthesis of iodine-123 labeled curcumin

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