Catalytic Enantioselective Synthesis of β-Allenyl Boronic Esters by Conjunctive Cross-Coupling with Propargylic Carbonates

Aparece, Mark D.; Hu, Weipeng; Morken, James P.

doi:10.1021/acscatal.9b04453

Cited by 28 publications

(8 citation statements)

References 48 publications

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“…Again, boron functionalization was effectively used as hydroxyl precursors by treatment with NaBO 3 . ( S , S )-MandyPhos ligand ( 119 ) was employed to induce central chirality, providing β-allenols 118 with good yields and enantioselectivities up to 98% (Scheme , reaction a) . A related approach reacted vinyl arenes 121 and bis(pinacolato)diboron B 2 (pin) 2 with propargylic phosphates 120 under Cu catalysis and ( R,S )-Josiphos ( 124 ) as chirality transfer agent.…”

Section: Synthesis Of Allenolsmentioning

confidence: 99%

Deciphering the Chameleonic Chemistry of Allenols: Breaking the Taboo of a Onetime Esoteric Functionality

2021

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The allene functionality has participated in one of the most exciting voyages in organic chemistry, from chemical curiosities to a recurring building block in modern organic chemistry. In the last decades, a special kind of allene, namely, allenol, has emerged. Allenols, formed by an allene moiety and a hydroxyl functional group with diverse connectivity, have become common building blocks for the synthesis of a wide range of structures and frequent motif in naturally occurring systems. The synergistic effect of the allene and hydroxyl functional groups enables allenols to be considered as a unique and sole functionality exhibiting a special reactivity. This Review summarizes the most significant contributions to the chemistry of allenols that appeared during the past decade, with emphasis on their synthesis, reactivity, and occurrence in natural products.

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Section: Synthesis Of Allenolsmentioning

confidence: 99%

Deciphering the Chameleonic Chemistry of Allenols: Breaking the Taboo of a Onetime Esoteric Functionality

2021

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“…133 Using this strategy, Morken has described the enantioselective synthesis of allenols by Pd-catalyzed conjunctive crosscoupling using propargyl carbonates as electrophiles (Scheme 53). 134 The reaction was proposed to start with a first oxidative addition of the propargyl carbonate to a Pd 0 complex via an S N 2′ process. The resulting intermediate reacts with the nucleophilic boronate reagent to deliver the enantioenriched borylated allene.…”

Section: (Scheme 38)mentioning

confidence: 99%

Transition-Metal-Catalyzed Functionalization of Alkynes with Organoboron Reagents: New Trends, Mechanistic Insights, and Applications

et al. 2021

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Catalytic functionalization of alkynes with organoboron reagents provides a straightforward access to stereochemically defined multisubstituted alkenes, which are structural motifs commonly found in bioactive compounds and organic materials. Recent progress has substantially broadened the scope of this field on several fronts. Strategies for regioselectivity control in the 1,2-migratory insertion across unsymmetrical internal alkynes, as well as for the direct access to products with anti-insertion stereochemistry, have been devised. The alkenyl-to-aryl 1,4-metal migration upon metal insertion has been recently exploited in powerful cascade sequences leading to complex polycyclic scaffolds, including the development of enantioselective processes. Elegant enantiospecific and dynamic kinetic resolution methods have been developed for accessing chiral allenes from propargylic alcohol derivatives. Mechanistic manifolds have emerged based on single-electron transfer (SET) that have provided a fresh impetus for alkyne 1,2-difunctionalization with complementary stereoselectivity to processes relying on 1,2-insertion of R–M species. Herein, we discuss the most recent advances in transition-metal-catalyzed functionalization of alkynes using organoboron reagents, categorized according to the type of mechanistic outcome. Emphasis is placed on mechanistic aspects, synthetic utility, limitations, and challenges for future research.

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“…[34] Finally,u sing propargylic carbonates 72 in place of aryl triflates furnished fully substituted b-boryl allenes with high enantioselectivity (Scheme 13 e). [35] It was found that amethanol additive resulted in formation of ad imethoxyboronate intermediate through boron ligand exchange,w hich significantly enhanced both the yield and enantioselectivity of the reaction.…”

Section: Transition Metal-catalyzed Conjunctive Cross-couplingsmentioning

confidence: 99%

Stereospecific 1,2‐Migrations of Boronate Complexes Induced by Electrophiles

et al. 2020

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The stereospecific 1,2‐migration of boronate complexes is one of the most representative reactions in boron chemistry. This process has been used extensively to develop powerful methods for asymmetric synthesis, with applications spanning from pharmaceuticals to natural products. Typically, 1,2‐migration of boronate complexes is driven by displacement of an α‐leaving group, oxidation of an α‐boryl radical, or electrophilic activation of an alkenyl boronate complex. The aim of this article is to summarize the recent advances in the rapidly expanding field of electrophile‐induced stereospecific 1,2‐migration of groups from boron to sp2 and sp3 carbon centers. It will be shown that three different conceptual approaches can be utilized to enable the 1,2‐migration of boronate complexes: stereospecific Zweifel‐type reactions, catalytic conjunctive coupling reactions, and transition metal‐free sp2–sp3 couplings. A discussion of the reaction scope, mechanistic insights, and synthetic applications of the work described is also presented.

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Catalytic Enantioselective Synthesis of β-Allenyl Boronic Esters by Conjunctive Cross-Coupling with Propargylic Carbonates

Abstract: Enantioselective conjunctive cross-coupling with propargylic carbonates affords β-boryl allenes as the reaction product. The reaction is found to proceed through the intermediacy of dimethoxyboronate complexes that are generated in situ by a strain-induced ligand exchange reaction.

Cited by 28 publications

References 48 publications

Deciphering the Chameleonic Chemistry of Allenols: Breaking the Taboo of a Onetime Esoteric Functionality

Deciphering the Chameleonic Chemistry of Allenols: Breaking the Taboo of a Onetime Esoteric Functionality

Transition-Metal-Catalyzed Functionalization of Alkynes with Organoboron Reagents: New Trends, Mechanistic Insights, and Applications

Stereospecific 1,2‐Migrations of Boronate Complexes Induced by Electrophiles

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