O-benzoyl Hydroxylamines Research Articles

Synthesis of α-ketoamides via oxidative amidation of diazo compounds with O-benzoyl hydroxylamines as nitrogen source and the oxidant.

A simple, efficient method has been described for the construction of an array of α-ketoamides from readily available O-benzoyl hydroxylamines and diazo compounds as starting materials. There was a combined use of CuI as a catalyst and H2O as the oxygen source. The investigation reveals that the O-benzoyl hydroxylamines serve a dual role as both an amine source and the oxidant in this mechanism, thereby obviating the need for additional oxidants in the transformation process. This methodology could give a wider range of products in good to excellent yields for most substrates, and thus, we provide a new idea for the synthesis of α-ketoamides.

Copper-Catalyzed Photoredox Reaction of Aldehydes with O-Benzoyl Hydroxylamines for the Formation of Amides

Amides are one of the most important functional groups since they are the backbones of essential biomolecules such as peptides, proteins, and nucleic acids and are also found in pharmaceuticals,...

Cu-Catalyzed Cross-Electrophilic Coupling of α-Diazoesters with O-Benzoyl Hydroxylamines for the Synthesis of Unnatural N-Alkyl α-Amino Acid Derivatives

We describe a Cu-catalyzed cross-electrophilic coupling reaction for synthesizing α-amino acid derivatives from α-diazoesters with O-benzoyl hydroxylamines with Cu(OAc)2 as the catalyst and polymethylhydrosilane (PMHS) as the hydride reagent. Excellent functional group compatibilities were demonstrated. With ethyl 2-diazo-3-oxobutanoate as the precursor, a Cu-acetoacetate complex has been characterized by ESI-MS analysis. Results from the radical trap experiments are consistent with the intermediacy of nitrogen-centered radicals. This strategy offers a simple and inexpensive synthesis of α-amino acid derivatives.

Urea Synthesis from Isocyanides and O-Benzoyl Hydroxylamines Catalyzed by a Copper Salt

In the presence of CuOAc, a series of unsymmetric ureas can be generated in moderate to good yields under mild reaction conditions (10 mol% of CuOAc, 2 equiv t-BuONa or PhONa, 30 °C), using aryl isocyanides and O-benzoyl hydroxylamines as the readily accessible starting materials. The reactions might undergo a cascade process involving isocyanide insertion into the N-O bond and Mumm-type rearrangement. This work represents a rare example of isocyanide insertion into N-O bonds, which would extend isocyanide insertion chemistry.

Catalytic Lewis Base Additive Enables Selective Copper-Catalyzed Borylative α-C-H Allylation of Alicyclic Amines.

Functionalized alicyclic amines are important building blocks for the synthesis of bioactive natural compounds and drugs. Existing methods of functionalization are typically limited to the synthesis of protected amines or the use of highly basic organometallic reagents that can compromise functional group tolerance. Here, we report a novel approach that enables the transformation of O-benzoyl hydroxylamines into α-functionalized cyclic secondary amines by means of a copper-catalyzed regio-, stereo-, and chemoselective coupling with allenes and bis(pinacolato)diboron. A key feature of the present transformation is the use of a catalytic Lewis base additive which inhibits the competing C–N bond forming reaction between the catalytically generated boron-substituted allylcopper intermediate with the O-benzoyl hydroxylamine, thus enabling in situ transformation of the latter into an alicyclic imine which undergoes selective C–C bond formation with the allylcopper species.

Copper(I)-Catalyzed Asymmetric Synthesis of P-Chiral Aminophosphinites.

Herein, a copper(I)-catalyzed reaction of diarylphosphines and O-benzoyl hydroxylamines is developed. In the cases of symmetrical diarylphosphines, a series of aminophosphinites is prepared in high yields. In the cases of unsymmetrical diarylphosphines, an array of P-chiral aminophosphinites is synthesized in high yields with high enantioselectivity by using a copper(I)-(R,RP )-Ph-FOXAP complex as a chiral catalyst. Based on several control experiments and 31 P NMR studies, a two-electron redox mechanism involving the dynamic kinetic asymmetric transformation of unsymmetrical diarylphosphines is proposed for the copper(I)-catalyzed asymmetric reaction. Finally, one representative P-chiral phosphoric amide generated through the oxidation with H2 O2 is transformed to a chiral diarylphosphinate in high yield with retained enantioselectivity, which allows further transformations towards various P-chiral tertiary phosphines.

Copper-Catalyzed Intermolecular C(sp2)-H Amination with Electrophilic O-Benzoyl Hydroxylamines.

A copper-catalyzed intermolecular electrophilic amination of benzamides with O-benzoyl hydroxylamines was achieved with the assistance of an 8-aminoquinolyl group. With this protocol, good compatibility was observed for a variety of aryl amides and heteroaryl amides, and excellent tolerance with various functional groups was achieved. Significantly, the monoaminated product was overwhelmingly delivered under the simple reaction conditions. Preliminary mechanistic investigations suggested that a radical pathway should be excluded and C-H activation be potentially the rate-determining step.

Rare-Earth-Catalyzed Transsulfinamidation of Sulfinamides with Amines.

A rare-earth-catalyzed transsulfinamidation of primary sulfinamides with alkyl, aryl, and heterocyclic amines for the synthesis of diverse secondary and tertiary sulfinamides has been realized. Unlike transition metal-catalyzed cross-coupling approaches restricted to non-commercially available disubstituted O-benzoyl hydroxylamines, this newly developed protocol is suitable for diverse readily available primary and secondary amines without any modifications. Excellent catalytic activity and selectivity are achieved with Eu(OTf)3 under mild reaction conditions, which extends the applicability of rare-earth catalysis.

Triethyl Phosphite/Benzoyl Peroxide Mediated Reductive Dealkylation of O‐Benzoylhydroxylamines: A Cascade Synthesis of Secondary Amides

A new triethyl phosphite/benzoyl peroxide (BPO) mediated system has been developed for the synthesis of secondary amides with good to excellent yields in a single step. This unprecedented cascade process involves sequential reduction of N–O bond and benzoylation followed by dealkylation of N–C bond of O‐benzoylhydroxylamines (O‐BHA). The methodology is versatile as it tolerates a variety of aromatic and aliphatic O‐BHA as substrates to access secondary amides.

Copper-Catalyzed Three-Component Redox-Neutral Ring Opening of Benzothiazoles to 1-Amino-N-(2-(phenylthio)phenyl)methanimine.

Copper-catalyzed three-component redox-neutral ring opening of benzothiazoles with aryl iodides and O-benzoyl hydroxylamines for the synthesis of 1-amino-N-(2-(phenylthio)phenyl)methanimine has been developed. This one-pot reaction undergoes C-S and N-O bond cleavage and new C-S and C-N bond construction. Several control experiments excluded a free radical procedure and also demonstrated the secondary amine as a possible intermediate, which was vital to the catalytic reaction. Meanwhile, the deuteration experiment got rid of the C-H activation dehydroisomerization of the benzothiazole mechanism.

Redox-Neutral ortho Functionalization of Aryl Boroxines via Palladium/Norbornene Cooperative Catalysis

Palladium/norbornene (Pd/NBE) cooperative catalysis, also known as the Catellani reaction, has become an increasingly useful method for site-selective arene functionalization; however, certain constraints still exist due to its intrinsic mechanistic pathway. Herein we report a redox-neutral ortho functionalization of aryl boroxines via Pd/NBE catalysis. An electrophile, such as carboxylic acid anhydrides or O-benzoyl hydroxylamines, is coupled at the boroxine ortho position, and a proton as the second electrophile is introduced at the ipso position. This reaction does not require extra oxidants or reductants, and avoids stoichiometric bases or acids, thereby tolerating a wide range of functional groups. In particular, orthogonal chemoselectivity between aryl iodide and boroxine moieties is demonstrated, which could be used to control reaction sequences. Finally, a deuterium labelling study supports the ipso-protonation pathway. This unique mechanistic feature could inspire the development of a new class of Pd/NBE-catalyzed transformations.

Copper-Catalyzed Dihydroquinolinone Synthesis from Isocyanides and O-Benzoyl Hydroxylamines

A copper-catalyzed protocol has been realized for the rapid assembly of dihydroquinolinones from readily accessible isocyanides and O-benzoyl hydroxylamines. The reactions (10 mol % of CuOAc, 10 mol % of dppe, 3 equiv of PhONa, 30 °C) deliver various structurally interesting dihydroquinolinones in moderate to good yields (up to 76%). The reactions may proceed in a cascade manner involving isocyanide insertion into the N-O bond, Mumm-type rearrangement, and intramolecular nucleophilic substitution.

Copper-Catalyzed Transsulfinamidation of Sulfinamides as a Key Step in the Preparation of Sulfonamides and Sulfonimidamides.

Secondary or tertiary sulfinamides are prepared by copper-catalyzed transsulfinamidation of primary sulfinamides with O-benzoyl hydroxylamines. Subsequent oxidations of the resulting products lead to the corresponding sulfonamides. Treatment of N-aryl sulfinamides with O-benzoyl hydroxylamines under copper catalysis provides N-aryl sulfonimidamides.

Copper-catalysed dehydrogenative α-C(sp3)–H amination of tetrahydroquinolines with O-benzoyl hydroxylamines

A copper-catalysed dehydrogenative α-C(sp3)–H amination of tetrahydroquinolines with O-benzoyl hydroxylamines has been demonstrated, which enables direct access to 2-alkylaminoquinolines in efficient manner.

One-Pot Bimetallic Pd/Cu-Catalyzed Synthesis of Sulfonamides from Boronic Acids, DABSO and O-Benzoyl Hydroxylamines.

A practical and straightforward bimetallic Pd/Cu catalytic system has been developed. This system affords various sulfonamides in one pot from easy-to-handle and readily available boronic acids, sulfur dioxide surrogate DABSO and O-benzoyl hydroxylamines in high yields. Without additional ligands, the newly developed catalytic system revealed a broad substrate scope for both partners and tolerated a wide array of functional groups even at low catalyst loadings. Furthermore, based on control experiments, a plausible mechanism has been proposed, in which sodium sulfinate has been isolated and identified as the crucial intermediate for this transformation.

Cu-Catalyzed electrophilic amination of internal alkynes via hydroalumination.

A straightforward and efficient method for the synthesis of 1,2-diaryl-substituted enamines through the Cu-catalyzed electrophilic amination reaction of O-benzoyl hydroxylamines with vinylaluminum reagents generated in situ from the Ni-catalyzed hydroalumination of readily accessible internal aryl acetylenes is described. The amination is catalyzed by 1 mol% CuCl without any additive at ambient temperature to afford new versatile enamines in good yield (61-91%) with high selectivity (>98% E-enamine).

Transition Metal Catalyzed Direct Amination of the Cage B(4)-H Bond in o-Carboranes: Synthesis of Tertiary, Secondary, and Primary o-Carboranyl Amines.

Transition metal catalyzed regioselective amination of the cage B(4)-H bond in o-carboranes has been achieved for the first time using O-benzoyl hydroxylamines or organic azides as the amination reagents, leading to the preparation of a series of tertiary and secondary carboranyl amines. Both amination reactions proceeded under mild conditions without the addition of any external oxidants. Hydrogenolysis of the resultant product 4-N(CH2Ph)2-o-carborane afforded the primary carboranyl amine, 4-amino-o-carborane, in quantitative yield.

DFT Study of Pd(0)-Promoted Intermolecular C-H Amination with O-Benzoyl Hydroxylamines.

Computational studies were carried out to explore the mechanism of Pd-catalyzed intermolecular C-H amination with O-benzoyl hydroxylamines in which both Pd(0) and Pd(II) catalysts are effective. For the Pd(0)-catalyzed reaction, the generally assumed Pd(0)/Pd(II) catalytic cycle might not be feasible. Instead, Pd(0), being essentially a catalyst precursor, could be oxidized to Pd(II), and the C-H amination proceeds through the Pd(II)/Pd(IV) catalytic cycle.

Room temperature copper-catalyzed oxidative amidation of terminal alkynes for the synthesis of α-ketoamides using O-benzoyl hydroxylamines as aminating reagent and oxidant

A novel and convenient copper-catalyzed oxidative amidation for the synthesis of α-ketoamides has been successfully developed, which uses easily available O-benzoyl hydroxylamines as aminating reagent and oxidant.

Copper-Catalyzed Electrophilic Amination of Heteroarenes via C-H Alumination.

A highly efficient Cu-catalyzed electrophilic amination reaction of readily available heteroarenes with O-benzoyl hydroxylamines via a one-pot C-H alumination is reported. The reactions were catalyzed using 1 mol % of CuCl to afford various heteroaryl amines in good to excellent yields. The direct C-H lithiation/transalumination of heteroarenes and catalytic amination sequence can be performed in a single vessel on gram scales.