Copper-Catalyzed Diboration of Ketones: Facile Synthesis of Tertiary α-Hydroxyboronate Esters

McIntosh, Melissa L.; Moore, Cameron M.; Clark, Timothy

doi:10.1021/ol100468f

Cited by 75 publications

(62 citation statements)

References 38 publications

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“…The protocol for the previously reported diboration of aldehydes 17 and ketones 18 did not involve the addition of methanol. In the absence of methanol, intermediate 3c (Scheme 2) undergoes transmetalation with a molecule of bis(pinacolato)diboron in the rate determining step to generate the desired dibora compound 3d and regenerate the active catalyst 3a .…”

Section: Resultsmentioning

confidence: 99%

Stereospecific Cross-Coupling of Secondary Organotrifluoroborates: Potassium 1-(Benzyloxy)alkyltrifluoroborates

2012

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Potassium 1-(alkoxy/acyloxy)alkyltrifluoroborates have been synthesized through a copper-catalyzed diboration of aldehydes and subsequent conversion of the resulting potassium 1-(hydroxy)alkyltrifluoroborates. The palladium-catalyzed Suzuki-Miyaura reaction employing the potassium 1-(benzyloxy)alkyltrifluoroborates with aryl and heteroaryl chlorides provides access to protected secondary alcohols in high yields. The β-hydride elimination pathway is avoided through use of the benzyl protecting group, which is proposed to stabilize the diorganopalladium intermediate by coordination of the arene to the metal center. This cross-coupling is stereospecific with complete retention of stereochemistry.

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Section: Resultsmentioning

confidence: 99%

Stereospecific Cross-Coupling of Secondary Organotrifluoroborates: Potassium 1-(Benzyloxy)alkyltrifluoroborates

2012

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“…Forall cases we observed high yields and nearly perfect diastereo-and enantioselectivities.R emarkably,t he conditions are compatible with the presence of an unprotected ketone (compound 2i)t hat could also react under copper-catalyzed borylation conditions. [13] Diastereomeric cyclobutenes 1j and 1k afforded the desired boronic esters 2j and 2k with similar levels of stereocontrol. Additionally,t he presence of at ertiary stereocenter (compound 2l)a ffected neither the diastereo-nor enantioselectivity.I n these last three examples (2j-2l), enantiomerically enriched compounds with four stereocenters were obtained in asingle step starting from meso precursors (1j-1l).…”

Section: Angewandte Chemiementioning

confidence: 97%

Enantioselective Synthesis of Cyclobutylboronates via a Copper‐Catalyzed Desymmetrization Approach

et al. 2016

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“…[6,7] This reaction is widely applicable to substrates such as alkynes [8,9] arynes, [10] alkenes, [11][12][13] carbenoids, [14,15] as well as diazo [16] and carbonyl compounds. [17][18][19][20] Although bis(catecholato)diborane(4) and bis(pinacolato)diborane(4) represent by far the most commonly employed diborane(4) species, the reaction is not restricted to their use. For instance, several diboranes(4) with interesting properties are derived from [2]borametalloarenophanes.…”

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confidence: 99%

Unexpected Generation of Diastereomers by Double Diboration of a Dialkyne

Bauer

Braunschweig

Gruß

et al. 2011

Chemistry A European J

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During the last two decades, boron compounds have become established as versatile reagents in organic synthesis, and different methods have been developed for their preparation. Along with hydroboration, [1][2][3][4] transition-metalcatalyzed diboration [5] has become useful for the functionalization of unsaturated organic compounds. [6,7] This reaction is widely applicable to substrates such as alkynes [8,9] arynes, [10] alkenes, [11][12][13] carbenoids, [14,15] as well as diazo [16] and carbonyl compounds. [17][18][19][20] Although bis(catecholato)diborane(4) and bis(pinacolato)diborane(4) represent by far the most commonly employed diborane(4) species, the reaction is not restricted to their use. For instance, several diboranes(4) with interesting properties are derived from [2]borametalloarenophanes. The first example of this class of organometallic compound, the [2]boraferrocenophane 1, was prepared by Herberhold, Wrackmeyer and co-worker, [21] while the molecular structure along with an alternative synthesis was published by our group.[22] Subsequently, a series of [2]borametalloarenophanes has appeared. [23-28b] These ansa complexes show tilted molecular structures, thus featuring significant molecular strain. In 2006, we successfully exploited this ring strain in oxidative addition reactions of [2]borametalloarenophanes to low-valent platinum centers, affording[3]diboraplatinametalloarenophanes. In addition, we demonstrated the suitability of [2]borametalloarenophanes as diboranes(4) in the platinum-mediated diboration of alkynes to form [4]diboradicarbametalloarenophanes.[29] By expansion of this strategy, we also achieved the diboration of diazo compounds [16] and isocyanides.[30]Herein, we report on the two diastereomeric [4]diboradicarbaferrocenophanes 4 and 5, which were obtained by double diboration of the conjugated dialkyne 3 either by a platinum-mediated route employing the [2]boraferrocenophane 1 in the presence of [PtA C H T U N G T R E N N U N G (PEt 3 ) 3 ], or stoichiometrically by using the [3]diboraplatinaferrocenophane 2, directly (Scheme 1). In contrast to related transformations of monoalkynes, [29] monitoring the reaction progress by multinuclear NMR spectroscopy revealed the gradual disappearance of the starting materials, and the formation of two distinct compounds in benzene solution at elevated temperatures. Both species feature similar resonances in the 1 H, 11 B, and 13 C NMR spectra, which we rationalized by the generation of diastereomeric species. Complexes 4 and 5 were eventually isolated after workup as orange, moderately moisture-sensitive powders. The NMR spectroscopic data of both diastereomers are fully consistent with the presence of doubly bis(borylated), conjugated triene systems bearing two ferro-

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Copper-Catalyzed Diboration of Ketones: Facile Synthesis of Tertiary α-Hydroxyboronate Esters

Cited by 75 publications

References 38 publications

Stereospecific Cross-Coupling of Secondary Organotrifluoroborates: Potassium 1-(Benzyloxy)alkyltrifluoroborates

Stereospecific Cross-Coupling of Secondary Organotrifluoroborates: Potassium 1-(Benzyloxy)alkyltrifluoroborates

Enantioselective Synthesis of Cyclobutylboronates via a Copper‐Catalyzed Desymmetrization Approach

Unexpected Generation of Diastereomers by Double Diboration of a Dialkyne

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