Recent Advances in the Preparation of Allylboronates and Their Use in Tandem Reactions with Carbonyl Compounds

Kennedy, Jason W. J.; Hall, Dennis G.

doi:10.1002/3527606548.ch6

Cited by 25 publications

(5 citation statements)

References 122 publications

(175 reference statements)

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“…Among methods for making C–C bonds, asymmetric allylboration of aldehydes is one of the most reliable and important in synthesis . Since Hoffmann’s realization that relative stereochemistry could be controlled by the double-bond geometry of crotylboronates and Brown’s discovery of highly enantioselective allylborations using pinane-derived reagents, this reaction has established strong roots in synthesis.…”

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confidence: 99%

Highly Diastereo- and Enantioselective Allylboration of Aldehydes using α-Substituted Allyl/Crotyl Pinacol Boronic Esters via in Situ Generated Borinic Esters

et al. 2013

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Readily available, α-substituted allyl/crotyl pinacol boronic esters often give low E/Z selectivity (with Z favored) in reactions with aldehydes. We found that addition of nBuLi to the pinacol boronic ester followed by trapping of the alkoxide with TFAA leads to an intermediate allyl borinic ester which undergoes allylboration with very high E selectivity. The substrate scope includes primary to tertiary alkyl α-substituents, crotyl substrates, and the previously unreported β-methallyl pinacol boronic esters. The latter give very high Z selectivity under standard conditions which is completely reversed to high E selectivity under the new conditions. Monitoring the reaction by 11 B NMR confirmed that the reaction proceeds through a borinic ester intermediate.

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confidence: 99%

Highly Diastereo- and Enantioselective Allylboration of Aldehydes using α-Substituted Allyl/Crotyl Pinacol Boronic Esters via in Situ Generated Borinic Esters

et al. 2013

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“…Allylic boronic acids or their esters hold a position of utmost importance in the field of organoboron chemistry, as their extensive applications in organic synthesis are widely recognized. − The unique combination of an adjacent double bond and a boryl moiety imparts them with distinct and valuable reactivities, setting them apart from conventional organoborons. This is exemplified by their key role in allylboration reactions that enable the efficient transformation of carbonyl and imine functionalities. , Remarkably, these reactions often proceed through a highly organized “closed” Zimmerman–Traxler (ZT) transition state, leading to a high degree of diastereoselectivity and the synthesis of complex 3D architectures from simple 2D fragments in a stereocontrolled manner. − The diastereospecific nature of these reactions also emphasizes the significance of employing stereodefined allylborons, as the E and Z isomers produce distinct diastereoisomeric products (Scheme A). − …”

Section: Introductionmentioning

confidence: 99%

“…a Yield determined by analysis of the crude 1 H NMR spectra using CH 2 Br 2 as an external standard. b Geometric ratio determined by1 H NMR spectroscopy from the crude product. PMP: 1,2,2,6,6pentamethylpiperidine, PC1: 4CzIPN (2,4,5,6-tetra(9H-carbazol-9yl)-1,3-dicyanobenzene), CyH: cyclohexane, PC2: Ir(ppy) 3 , PC3: entry 10), while the absence of light prevented product formation, emphasizing its fundamental role (Table1, entry 11).…”

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confidence: 99%

Catalyst-Enabled Stereodivergence in Photochemical Atom Transfer Radical Addition (ATRA) of α-Iodoboronic Esters to Alkynes

Fan,

Huang,

Lin

et al. 2023

ACS Catal.

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The atom transfer radical addition (ATRA) to alkynes is a valuable strategy for the synthesis of allylic substituted molecules, yet it has not been applied to the synthesis of allylic boronic acids or their esters, which are important building blocks in organic synthesis. The inherent challenge for ATRA reactions is control of the geometric selectivity. By employing different alkene geometric isomerization techniques, namely, photochemical uphill catalysis and manganese-catalyzed halogen-abstraction/radical rebound processes, we are able to synthesize both isomers of iodinated allylic boronic esters in a stereoselective manner. Mechanistic investigations reveal the dual functionalities of both catalysts, acting as catalysts for both ATRA and geometric isomerization processes. The protocols feature a broad substrate scope and good functional group tolerance. Importantly, the iodo and boryl moieties within the products provide orthogonal handles for further synthetic manipulations. The strategy employed here should inspire more efforts toward stereoselective ATRA reactions of alkynes.

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“…Consequently, stereoselective coupling reactions constructing chiral 1,2-diol motifs with concurrent C–C bond formation between two functionalized synthetic fragments can be powerful tools for the efficient convergent synthesis of the complex polyols containing multiple stereocenters . Addition reactions of enantioenriched γ-alkoxyallyl organometallic reagents to a carbonyl compound have been employed for the construction of the stereodefined 3-ene-1,2-diol structure with a concomitant C–C bond formation, and the double bond in the product can be further utilized through a number of selective functionalization reactions. ,,, Among the γ-alkoxyallyl organometallic reagents, (γ-alkoxyallyl)boron compounds are commonly used as versatile reagents for asymmetric synthesis because they react both reliably and predictably, exhibiting high levels of stability under atmospheric conditions and low toxicity . Following from the initial studies of Hoffmann and Wuts, the stereoselective allylation of aldehydes with (γ-alkoxyallyl)boron compounds has been used for the synthesis of polyoxygenated natural products and pharmaceuticals .…”

Section: Introductionmentioning

confidence: 99%

Copper(I)-Catalyzed Enantioselective Synthesis of α-Chiral Linear or Carbocyclic (E)-(γ-Alkoxyallyl)boronates

et al. 2014

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A new method has been developed for the catalytic asymmetric synthesis of α-chiral linear or carbocyclic (γ-alkoxyallyl)boronates via the copper(I)-catalyzed γ-boryl substitution of allyl acetals. This reaction afforded the products in high yields with excellent E:Z selectivities and enantioselectivities [only (E)-product, 91-98% ee] and also exhibited high functional group compatibility. Subsequent allylation of aldehydes with the α-chiral (γ-alkoxyallyl)boronates provided the anti-1,2-diol derivatives in a highly stereospecific manner, and the utility of the α-chiral (γ-alkoxyallyl)boronates was further demonstrated by a convergent coupling of a complex polyol derivative using a (γ-alkoxyallyl)boronate and a chiral α-oxyaldehyde. The stereoselective modular construction of a complex 3,3-disubstituted cyclopentene containing three consecutive stereocenters including a quaternary chiral carbon was also reported. Useful transformations of the α-chiral linear (γ-alkoxyallyl)boronates were also demonstrated.

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Recent Advances in the Preparation of Allylboronates and Their Use in Tandem Reactions with Carbonyl Compounds

Cited by 25 publications

References 122 publications

Highly Diastereo- and Enantioselective Allylboration of Aldehydes using α-Substituted Allyl/Crotyl Pinacol Boronic Esters via in Situ Generated Borinic Esters

Highly Diastereo- and Enantioselective Allylboration of Aldehydes using α-Substituted Allyl/Crotyl Pinacol Boronic Esters via in Situ Generated Borinic Esters

Catalyst-Enabled Stereodivergence in Photochemical Atom Transfer Radical Addition (ATRA) of α-Iodoboronic Esters to Alkynes

Copper(I)-Catalyzed Enantioselective Synthesis of α-Chiral Linear or Carbocyclic (E)-(γ-Alkoxyallyl)boronates

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