Enantioselective carbenoid insertion into C(sp<sup>3</sup>)–H bonds

Santiago, João V.; Machado, Angelo H. L.

doi:10.3762/bjoc.12.87

Cited by 39 publications

(12 citation statements)

References 73 publications

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“… 3 However, due to the high reactivity of the metal carbenoid species, occasionally lower selectivity is observed in stereoselective reactions. 4 In recent years, borane mediated activation of nitrogen containing compounds has become a popular area of research following the groundbreaking work from Braunschweig which demonstrated that borylene species can effectively bind and activate dinitrogen. 5 In particular, research groups have explored the activation of diazo compounds using triarylboranes.…”

Section: Introductionmentioning

confidence: 99%

“…In general, the metal-carbenoid intermediates are reactive and therefore readily can undergo a range of organic reactions . However, due to the high reactivity of the metal carbenoid species, occasionally lower selectivity is observed in stereoselective reactions . In recent years, borane mediated activation of nitrogen containing compounds has become a popular area of research following the groundbreaking work from Braunschweig which demonstrated that borylene species can effectively bind and activate dinitrogen .…”

Section: Introductionmentioning

confidence: 99%

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Triarylborane Catalyzed Carbene Transfer Reactions Using Diazo Precursors

2021

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Reactive carbenes generated from diazo compounds are key intermediates for a range of organic reactions to afford synthetically useful organic compounds. The majority of these reactions have been carried out using transition metal catalysts. However, the formation of carbene intermediates using main group elements has not been widely investigated for synthetic purposes. Recent studies have demonstrated that triarylboranes can be used for the in situ generation of reactive carbene intermediates in both stoichiometric and catalytic reactions. These new reactivities of triarylboranes have gained significant attention in synthetic chemistry particularly in catalytic studies. The range of organic compounds that have been synthesized through these reactions are important as pharmaceuticals or agrochemicals. In this perspective, we highlight the recent progress and ongoing challenges of carbene transfer reactions generated from their corresponding diazo precursors using triarylboranes as catalysts. We also highlight the stoichiometric use of triarylboranes in which the boranes not only activate the diazo functionality to afford a carbene intermediate but also actively participate in the reactions as a reagent. The different mechanisms for activation and carbene transfer are described along with the mechanistic and computational studies that have aided the elucidation of these reaction pathways. Potential opportunities for the use of boranes as a catalyst toward different carbene transfer reactions and their future prospects are discussed.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Triarylborane Catalyzed Carbene Transfer Reactions Using Diazo Precursors

2021

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“…Undoubtedly, compounds 2a and 3a originated from cis and trans isomers of dilithiated 1 H -2,3-dihydroisoindole-1,3-diols, A cis/trans , formed by treatment of the parent (unsubstituted) hydroxylactams 1a with 2.3 equiv of the s -BuLi/TMEDA system (Figure ). One could suppose that with the elongation of rt reaction time these lithium alkoxides can undergo five-membered ring opening via tautomerization of their hemiketal moieties, proven by Tomooka et al, to form N,O -dilithiated γ-keto species B as classical carbenoids . The opposite reversible conversion, from open-chain ketones to cyclic alkoxy lithium salts, was reported by Epsztajn et al .…”

Section: Resultsmentioning

confidence: 99%

Unexpected Rearrangement of Dilithiated Isoindoline-1,3-diols into 3-Aminoindan-1-ones viaN-Lithioaminoarylcarbenes: A Combined Synthetic and Computational Study

et al. 2019

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The reaction of 2-aryl-3-hydroxyisoindolin-1ones with the s-BuLi•TMEDA system in THF at −78 °C, affording a series of diastereomeric 3-aminoindan-1-ones via a novel rearrangement of the isoindolinone scaffold, is reported. It is proposed that α-elimination of LiOH from the transient N,O-dilithiated hemiaminal carbenoids leads to the formation of singlet carbenes followed by their trapping via an intramolecular C−H insertion. An alternative explanation based on an intramolecular Mannich reaction seem much less probable. A mechanistic-type study that combines spectroscopic data of the products and calculation results, with a special focus on the diverse lithiated intermediates that are most likely to engage in the title process (particularly those with internal Li bonds), is presented. The MP2 approach, including the NPA and QTAIM data, provided insight into structures and properties of all these species. Two reaction routes A and B appeared to be possible for the postulated carbene mechanism. An unusual metamorphosis of the CCN atom triad, from a near sp 1-azaallene-type in more stable noncarbene Li enolates to a roughly sp 2 type in their carbene keto tautomers, is recognized in one of these pathways (route B). Dominant forms of resonance structures for the aforementioned tautomeric systems that have seven-membered quasi rings stabilized by Li + ions bridging the N and carbonyl O atoms are indicated. Large computational difficulties arising from a huge impact of internal Li + complexation on conformational preferences and electronic properties of carbonyl group-bearing lithium derivatives are also discussed. The new γ-keto carbene species under study belong to a subclass of acyclic aminoarylcarbenes.

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“…Enantioselective metal carbenoid C–H insertions are largely dominated by rhodium and copper catalysis; , however, over the last ten years, iridium chemistry has also brought an important contribution to this area. In 2009, Katsuki and co-workers introduced the first example of a catalytic enantioselective iridium carbenoid C–H insertion (Scheme ).…”

Section: Outer-sphere C–h Functionalizationmentioning

confidence: 99%

Catalytic Enantioselective Functionalizations of C–H Bonds by Chiral Iridium Complexes

et al. 2020

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The development of catalytic enantioselective transformations, enabling the construction of complex molecular scaffolds from simple precursors, has been a long-standing challenge in organic synthesis. Recent achievements in transition-metal catalyzed enantioselective functionalizations of carbon–hydrogen (C–H) bonds represent a promising pathway toward this goal. Over the last two decades, iridium catalysis has evolved as a valuable tool enabling the stereocontrolled synthesis of chiral molecules via C–H activation. The development of iridium-based systems with various chiral ligand classes, as well as studies of their reaction mechanisms, has resulted in dynamic progress in this area. This review aims to present a comprehensive picture of the enantioselective functionalizations of C–H bonds by chiral iridium complexes with emphasis on the mechanisms of the C–H activation step.

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Enantioselective carbenoid insertion into C(sp³)–H bonds

Cited by 39 publications

References 73 publications

Triarylborane Catalyzed Carbene Transfer Reactions Using Diazo Precursors

Triarylborane Catalyzed Carbene Transfer Reactions Using Diazo Precursors

Unexpected Rearrangement of Dilithiated Isoindoline-1,3-diols into 3-Aminoindan-1-ones viaN-Lithioaminoarylcarbenes: A Combined Synthetic and Computational Study

Catalytic Enantioselective Functionalizations of C–H Bonds by Chiral Iridium Complexes

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Enantioselective carbenoid insertion into C(sp3)–H bonds

Cited by 39 publications

References 73 publications

Triarylborane Catalyzed Carbene Transfer Reactions Using Diazo Precursors

Triarylborane Catalyzed Carbene Transfer Reactions Using Diazo Precursors

Unexpected Rearrangement of Dilithiated Isoindoline-1,3-diols into 3-Aminoindan-1-ones viaN-Lithioaminoarylcarbenes: A Combined Synthetic and Computational Study

Catalytic Enantioselective Functionalizations of C–H Bonds by Chiral Iridium Complexes

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Enantioselective carbenoid insertion into C(sp³)–H bonds