Synthesis of Highly-Substituted Enantiomerically Pure Allylboronic Esters and Investigation of Their Stereoselective Addition to Aldehydes

Vahabi, Roza; Frey, Wolfgang; Pietruszka, Jörg

doi:10.1021/jo402130u

Cited by 16 publications

(1 citation statement)

References 92 publications

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“…A similar efficient chirality transfer experiment was reported in a Tsuji–Trost allylic alkylation. , However, these results show that leaving groups affect the chirality transfer in boryl-substituted η 3 -allylpalladium-mediated transformations. In addition, alkenylboronate 1m that introduced stereogenic centers onto the boronic ester moiety also enables a chirality transfer reaction . Consequently, chirality transfer into the product was observed in 45% ee .…”

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confidence: 99%

Pd-Catalyzed Three-Component Reaction of 3-(Pinacolatoboryl)ally Acetates, Aldehydes, and Organoboranes: A New Entry to Stereoselective Synthesis of (Z)-anti-Homoallylic Alcohols

2015

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The Pd-catalyzed three-component reaction of 3-(pinacolatoboryl)allyl acetates, aldehydes, and organoboranes is described. The reaction is initiated by the formation of an allylic gem-palladium/boryl intermediate, which then undergoes allylation of aldehydes by allylboronates followed by a coupling reaction of in situ generated (Z)-vinylpalladium acetates with organoboranes to provide the (Z)-anti-homoallylic alcohols with high levels of diastereoselectivity and alkene stereocontrol.

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confidence: 99%

Pd-Catalyzed Three-Component Reaction of 3-(Pinacolatoboryl)ally Acetates, Aldehydes, and Organoboranes: A New Entry to Stereoselective Synthesis of (Z)-anti-Homoallylic Alcohols

2015

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Reactions of Aldehydes and Ketones and Their Derivatives

Murray¹

2016

Organic Reaction Mechanisms · 2013

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[3,3]‐Sigmatropic Rearrangement/Allylboration/Cyclization Sequence: Enantioenriched Seven‐Membered‐Ring Carbamates and Ring Contraction to Pyrrolidines

et al. 2015

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The combination of in situ generated a-isocyanato allylboronic esters and aldehydes afforded seven-memberedring enecarbamates with high levels of diastereo-and enantiocontrol. They were easily converted into diversely substituted 1,3-oxazepan-2-ones.A nu nprecedented rearrangement of 5-acetoxy-7-aryl or styryl derivatives led to tetrasubstituted pyrrolidines.Acomputational study provides evidence on the feasibility of the proposed mechanism of this unusual ring contraction.Nitrogen heterocycles are widespread in ap lethora of molecules of interest, either in materials science,e lectronics, optics,o rb iology.[1] Among these,s even-membered-ring carbamates are relatively under-represented despite their interesting biological activities.[2] Several approaches are available for their synthesis,a nd the most common ones are based on intramolecular cyclization of 1,4-aminoalcohols or derivatives.[3] Others are restricted to isolated examples or very particular structures.[4] Our interest in the use of boronic esters in cascade reactions [5] led us to consider their utility for the synthesis of enantioenriched 4,5-dihydro-1,3-oxazepin-2-ones.T hese versatile intermediates led, through an unprecedented ring contraction reaction, to tetrasubstituted pyrrolidines,another family of major biological significance.Access to the key carbamates 1 was first achieved from optically active 1-alkyn-3-ols. [6,7] Dehydration with phosphine and carbon tetrabromide in the presence of triethylamine, [5d] followed by direct addition of aldehydes to the crude reaction mixture,a nd then aqueous NaHCO 3 15 hours later, afforded the cyclic ene carbamates 5 in good to moderate yields (threestep process;T able 1). Thestructure of 5 was assigned on the basis of NMR data and X-ray crystallographic analysis of 5a.[8]Thef ollowing mechanism can be proposed. After dehydration of 1,t he resulting allylcyanate 2 undergoes a[ 3,3]-sigmatropic rearrangement which affords the a-isocyanato allylboronate 3 (Scheme 1).[5d, 9, 10] Ac hairlike transition state [a][a] The reactions were carried out by addition of asolution of CBr 4 (0.56 mmol, 2.8 equiv) in CH 2 Cl 2 (0.5 mL) to amixture of 1 (0.2 mmol), polymer-supported phosphine (2.5 equiv),and Et 3 N(0.4 mmol, 2equiv) in dry CH 2 Cl 2 (2 mL). The aldehyde (0.24 mmol, 1.2 equiv) was added after 6hat 0 8 8C. The mixture was maintained at RT for 15 hbefore quenching with aqueousN aHCO 3 .[ b] Yield of product isolated after silica gel chromatography.

show abstract

Synthesis of Highly-Substituted Enantiomerically Pure Allylboronic Esters and Investigation of Their Stereoselective Addition to Aldehydes

Cited by 16 publications

References 92 publications

Pd-Catalyzed Three-Component Reaction of 3-(Pinacolatoboryl)ally Acetates, Aldehydes, and Organoboranes: A New Entry to Stereoselective Synthesis of (Z)-anti-Homoallylic Alcohols

Pd-Catalyzed Three-Component Reaction of 3-(Pinacolatoboryl)ally Acetates, Aldehydes, and Organoboranes: A New Entry to Stereoselective Synthesis of (Z)-anti-Homoallylic Alcohols

Reactions of Aldehydes and Ketones and Their Derivatives

[3,3]‐Sigmatropic Rearrangement/Allylboration/Cyclization Sequence: Enantioenriched Seven‐Membered‐Ring Carbamates and Ring Contraction to Pyrrolidines

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