Selective Reduction of Amides to Amines by Boronic Acid Catalyzed Hydrosilylation

Li, Yuehui; Torre, Jesús A. Molina de la; Grabow, Kathleen; Bentrup, Ursula; Junge, Kathrin; Zhou, Shaolin; Brückner, Angelika; Beller, Matthias

doi:10.1002/ange.201304495

Cited by 29 publications

(5 citation statements)

References 49 publications

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“…InI 3 has astronger Lewis acidity than In(OAc) 3 ,and thus results in an over-reduction of the lactam to give N-substituted pyrrolidines and piperidines. [6] Initially,w ec onducted the reaction of levulinic acid (1) with 1equivalent of 4-methylaniline (2a)i nt he presence of an indium catalyst and ahydrosilane.After several screenings of the reaction conditions, [7] 1mol %o fI n(OAc) 3 with 1equivalent of PhSiH 3 in toluene at 120 8 8Cw as found to be the best catalytic system, thus giving the desired g-lactam 3a in a9 8% yield upon isolation [Eq. (1)].…”

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confidence: 99%

Reductive Amination/Cyclization of Keto Acids Using a Hydrosilane for Selective Production of Lactams versus Cyclic Amines by Switching of the Indium Catalyst

2015

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Described herein is that the catalytic construction of N-substituted five- and six-membered lactams from keto acids with primary amines by reductive amination, using an indium/silane combination. This relatively benign and safe catalyst/reductant system tolerates the use of a variety of functional groups, especially ones that are reduction-sensitive. A direct switch from synthesizing lactams to synthesizing cyclic amines is achieved by changing the catalyst from In(OAc)3 to InI3. This conversion occurs by further reduction of the lactam using the indium/silane pair.

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confidence: 99%

Reductive Amination/Cyclization of Keto Acids Using a Hydrosilane for Selective Production of Lactams versus Cyclic Amines by Switching of the Indium Catalyst

2015

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“…Owing to their oxidative stability and ease of handling under ambient conditions relative to their borane counterparts, boronic acids have received considerable attention as catalysts for transformations and functionalizations of hydroxy-containing compounds. 35 Although examples of boronic acid-catalyzed carbonyl deoxygenation reactions remain limited, 36 the cationic hemiboronic acid 1 was recently reported to catalyze the deoxygenation of benzophenone and acetophenone derivatives in 1,1,1,3,3,3-hexafluoropropan-2-ol (HFIP) with 1,1,3,3-tetramethyldisiloxane (TMDSO) as a terminal reductant, demonstrating that hydrosilylation reactions typically performed using borane catalysts can also be conducted using a suitable boronic acid derivative (Scheme 1b ). 37 Herein, we report the application of this catalyst to the chemoselective reduction of α,β-unsaturated ketones with reagent-controlled chemoselectivity in which both conjugate reduction and global reduction products are accessible with proper choice of the silane under comparable catalytic conditions (Scheme 1c ).…”

Section: Table 1 Optimization Of the Conjugate And Glob...mentioning

confidence: 99%

Hemiboronic Acid-Catalyzed Reduction of α,β-Unsaturated Ketones with Reagent-Controlled Chemoselectivity

Hall,

Rygus,

Boateng

2023

Synlett

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The use of an air-stable cationic hemiboronic acid catalyst for the chemoselective reduction of enones is described. By changing the identity and stoichiometry of the silane reducing agent, either the conjugate reduction products or the fully reduced products can be obtained in high selectivity. In contrast to analogous reactions catalyzed by air- and moisture-sensitive borane catalysts, the hemiboronic acid catalyzed protocol can be performed under ambient conditions. Profiling studies revealed that global reduction proceeds via a rapid initial 1,4-addition, followed by ketone deoxygenation with a rate that is highly silane-dependent.

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“…Like other amides, pyrrolidones and caprolactams can be reductively deoxygenated to the corresponding pyrrolidines and azepans by lithium aluminum hydride (391)(392)(393)(394), sodium bis(2-methoxyethoxy)aluminum hydride (Red-Al ® ) (395,396), borane (397-400) and diisobutylaluminum hydride (DIBAL) (396). The same reduction can be accomplished by silanes and siloxanes (401)(402)(403)(404), by sodium borohydride in the presence of a Lewis acid, such as aluminum trichloride (405), or a Brønsted acid, such as methanesulfonic acid (406), and by catalytic hydrogenation (407)(408)(409)(410)(411). Selective reductive deoxygenation of the lactam carbonyl without reducing accompanying esters is accomplished by a two-step process involving low-temperature reduction with lithium triethylborohydride (Super-Hydride®), followed by work-up and further reduction of the lactamol intermediate with triethylsilane (Scheme 19) (412)(413)(414).…”

Section: Reduction Of Pyrrolidones and Caprolactamsmentioning

confidence: 99%

Introduction to Pyrrolidone and Caprolactam Chemistry

Chenault

2021

Handbook of Pyrrolidone and Caprolactam Based Materials

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Pyrrolidones and caprolactams are important structural components of solvents, surfactants, polymers, natural products, and pharmaceuticals. This chapter provides an introduction to the structure, conformation, physical properties and reactivity of pyrrolidones and caprolactams. It begins with an overview of the nomenclature of lactams since there are several systems of nomenclature in practice, plus common names and various syncretisms. Next, the structures of pyrrolidone and caprolactam are discussed, starting with the X-ray crystal structures of pyrrolidone, N-methylpyrrolidone (NMP) and caprolactam. The conformational flexibility and ring strain of the two ring systems are also covered.Physical properties, such as dipole moments, the enthalpies of formation, vaporization and fusion, boiling points and melting points, are described. An attempt is made to put the properties of pyrrolidones and caprolactams into context with those of other lactams, amides and even lactones and cyclic ketones. Brønsted and Lewis basicity, acidity, hydrogen bonding and solubility are covered.Finally, a brief description of the basic reactivity of pyrrolidones and caprolactams is given. Topics covered are N-, O-, and α-C-alkylation, hydrolysis, reactions with organometallics, reduction, oxidation, and ring-opening polymerization. The intent is to give a concise physical organic perspective on reactivity (and stability) more than an extended treatise on synthetic elaborations. Definition and Nomenclature of LactamsLactams are cyclic amides in which both the carbonyl carbon and nitrogen atom of the amide group are part of a ring. The name, lactam, is a portmanteau of lactone (cyclic ester) and amide.Nomenclature of lactams follows a variety of conventions (Figure 1 and Table 1). The International Union of Pure and Applied Chemistry (IUPAC) recommends naming lactams as heterocyclic pseudoketones (IUPAC method 1) or by substituting lactam for the

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Selective Reduction of Amides to Amines by Boronic Acid Catalyzed Hydrosilylation

Abstract: Vielseitig und metallfrei: Benzothiophen‐Boronsäuren katalysieren die Reduktion tertiärer, sekundärer und primärer Amide durch ein Hydrosilan. In der Reaktion wird eine Vielzahl von funktionellen Gruppen toleriert.

Cited by 29 publications

References 49 publications

Reductive Amination/Cyclization of Keto Acids Using a Hydrosilane for Selective Production of Lactams versus Cyclic Amines by Switching of the Indium Catalyst

Reductive Amination/Cyclization of Keto Acids Using a Hydrosilane for Selective Production of Lactams versus Cyclic Amines by Switching of the Indium Catalyst

Hemiboronic Acid-Catalyzed Reduction of α,β-Unsaturated Ketones with Reagent-Controlled Chemoselectivity

Introduction to Pyrrolidone and Caprolactam Chemistry

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