Solvent-Controlled Pd(II)-Catalyzed Aerobic Chemoselective Intermolecular 1,2-Aminooxygenation and 1,2-Oxyamination of Conjugated Dienes for the Synthesis of Functionalized 1,4-Benzoxazines

Pd(II)-catalyzed intermolecular 1,2-aminooxygenation and 1,2-oxyamination of conjugated dienes have been developed. The chemoselective preparation of a variety of 2-functionalized and 3-functionalized 1,4-benzoxazine derivatives was accomplished via the adjustment of a coordinating solvent. Oxygen was successfully used in this oxidative difunctionalization of alkenes. Good yields and selectivities were obtained for most products. A product bearing a spiro structure was also obtained from a 2,3-disubstituted-1,3-diene.

Dual catalysis for enantioselective convergent synthesis of enantiopure vicinal amino alcohols

Enantiopure vicinal amino alcohols and derivatives are essential structural motifs in natural products and pharmaceutically active molecules, and serve as main chiral sources in asymmetric synthesis. Currently known asymmetric catalytic protocols for this class of compounds are still rare and often suffer from limited scope of substrates, relatively low regio- or stereoselectivities, thus prompting the development of more effective methodologies. Herein we report a dual catalytic strategy for the convergent enantioselective synthesis of vicinal amino alcohols. The method features a radical-type Zimmerman–Traxler transition state formed from a rare earth metal with a nitrone and an aromatic ketyl radical in the presence of chiral N,N′-dioxide ligands. In addition to high level of enantio- and diastereoselectivities, our synthetic protocol affords advantages of simple operation, mild conditions, high-yielding, and a broad scope of substrates. Furthermore, this protocol has been successfully applied to the concise synthesis of pharmaceutically valuable compounds (e.g., ephedrine and selegiline).

Chiral vicinal amino alcohols are found in many bioactive compounds and may serve as chiral ligands. Here, the authors report a photocatalytic enantioselective cross-coupling of nitrones with aromatic aldehydes with a chiral ligand-coordinated rare earth ion synergistically producing enantiopure vicinal amino alcohols.

Biocatalytic approaches towards the stereoselective synthesis of vicinal amino alcohols

The global need for clean manufacturing technologies and the management of hazardous chemicals and waste present new research challenges to both chemistry and biotechnology.

Lewis acid catalyst-steered divergent synthesis of functionalized vicinal amino alcohols and pyrroles from tertiary enamides

We report herein two Lewis acid catalyst-steered distinct reaction pathways of N-formylmethyl tertiary enamides.

Radical-mediated intramolecular β-C(sp3)–H amidation of alkylimidates: facile synthesis of 1,2-amino alcohols

A new radical-mediated intramolecular β-C(sp³)–H amidation reaction of O-alkyl trichloro- or arylimidates is reported.

I2-Catalyzed intramolecular dehydrogenative aminooxygenation of alkynes to acylated imidazo[1,2-a]pyridines and indolizines

An efficient and green protocol for the construction of acylated imidazo[1,2-a]pyridines and indolizines via intramolecular dehydrogenative aminooxygenation of alkynes has been developed.

An Easy-to-Machine Electrochemical Flow Microreactor: Efficient Synthesis of Isoindolinone and Flow Functionalization

Flow electrochemistry is an efficient methodology to generate radical intermediates. An electrochemical flow microreactor has been designed and manufactured to improve the efficiency of electrochemical flow reactions. With this device only little or no supporting electrolytes are needed, making processes less costly and enabling easier purification. This is demonstrated by the facile synthesis of amidyl radicals used in intramolecular hydroaminations to produce isoindolinones. The combination with inline mass spectrometry facilitates a much easier combination of chemical steps in a single flow process.

Umpolung Synthesis of 1,3-Amino Alcohols: Stereoselective Addition of 2-Azaallyl Anions to Epoxides

We report the direct preparation of 1,3-amino alcohols that contain up to three contiguous stereogenic centers by the umpolung coupling of imines and epoxides. Nucleophilic 2-azaallyl anions, generated from imines, are stereoselectively added to epoxides to furnish 1,3-amino alcohols after hydrolysis of the product imine. Transformations afford amino alcohols with >98% site selectivity with respect to both reaction partners and in up to >98% yield and >20:1 dr.

Cu-catalyzed intermolecular oxyalkylation of styrenes under air: access to diverse iminolactones

A practical, simple, and efficient copper-catalyzed oxyalkylation of styrenes with α-bromoacetamides for the synthesis of iminolactones was developed under air.

Intramolecular aminocyanation of alkenes promoted by hypervalent iodine

Hypervalent iodine-promoted aminocyanation of unactivated alkenes has been developed and the orientation of cyanation on the double bond can be controlled.

Visible-Light Promoted Distereodivergent Intramolecular Oxyamidation of Alkenes

The visible-light-promoted diastereodivergent intramolecular oxyamination of alkenes is described to construct oxazolindinones, pyrrolidinones and imidazolidones via mild generation of primary amidyl radicals from functionalized hydroxylamines. A unique phenomenon of highly diastereoselective ring-opening of aziridines controlled by electron sacrifices was observed. Highly diastereoselective amino alcohols derivatives were obtained efficiently through this protocol in gram scales. The mechanistic studies suggested the isolatable anti-aziridine intermediates were generated quickly from primary amidyl radicals and the diastereoselectivities were controlled by pK_a values of the electron sacrifices.

Biosynthetic and synthetic access to amino sugars

Amino sugars are important constituents of a number of biomacromolecules and products of microbial secondary metabolism, including antibiotics. For most of them, the amino group is located at the positions C1, C2 or C3 of the hexose or pentose ring. In biological systems, amino sugars are formed due to the catalytic activity of specific aminotransferases or amidotransferases by introducing an amino functionality derived from L-glutamate or L-glutamine to the keto forms of sugar phosphates or sugar nucleotides. The synthetic introduction of amino functionalities in a regio- and stereoselective manner onto sugar scaffolds represents a substantial challenge. Most of the modern methods of for the preparation of 1-, 2- and 3-amino sugars are those starting from "an active ester" of carbohydrate derivatives, glycals, alcohols, carbonyl compounds and amino acids. A substantial progress in the development of region- and stereoselective methods of amino sugar synthesis has been made in the recent years, due to the application of metal-based catalysts and tethered approaches. A comprehensive review on the current state of knowledge on biosynthesis and chemical synthesis of amino sugars is presented.

Highly regio- and enantioselective multiple oxy- and amino-functionalizations of alkenes by modular cascade biocatalysis

New types of asymmetric functionalizations of alkenes are highly desirable for chemical synthesis. Here, we develop three novel types of regio- and enantioselective multiple oxy- and amino-functionalizations of terminal alkenes via cascade biocatalysis to produce chiral α-hydroxy acids, 1,2-amino alcohols and α-amino acids, respectively. Basic enzyme modules 1–4 are developed to convert alkenes to (S)-1,2-diols, (S)-1,2-diols to (S)-α-hydroxyacids, (S)-1,2-diols to (S)-aminoalcohols and (S)-α-hydroxyacids to (S)-α-aminoacids, respectively. Engineering of enzyme modules 1 & 2, 1 & 3 and 1, 2 & 4 in Escherichia coli affords three biocatalysts over-expressing 4–8 enzymes for one-pot conversion of styrenes to the corresponding (S)-α-hydroxyacids, (S)-aminoalcohols and (S)-α-aminoacids in high e.e. and high yields, respectively. The new types of asymmetric alkene functionalizations provide green, safe and useful alternatives to the chemical syntheses of these compounds. The modular approach for engineering multi-step cascade biocatalysis is useful for developing other new types of one-pot biotransformations for chemical synthesis.

Biocatalysis can perform highly selective multi-step synthesis in one pot, but with a limited range of non-natural reactions and products. Here, the authors report regio- and enantioselective bio-cascades, able to convert styrenes into a number of nitrogen and oxygen containing chiral molecules.

Azidation in the Difunctionalization of Olefins

Organic azides are key motifs in compounds of relevance to chemical biology, medicinal chemistry and materials science. In addition, they also serve as useful building blocks due to their remarkable reactivity. Therefore, the development of efficient protocols to synthesize these compounds is of great significance. This paper reviews the major applications and development of azidation in difunctionalization of olefins using azide reagents.

Copper-catalyzed aminooxygenation of styrenes with N-fluorobenzenesulfonimide and N-hydroxyphthalimide derivatives

A copper-catalyzed aminooxygenation reaction of styrenes with N-fluorobenzenesulfonimide and N-hydroxyphthalimide derivatives has been developed. The aminooxygenation product could be converted into the corresponding alcohol or free amine through the cleavage of the N–O or C–N bond of the N-hydroxyphthalimide moiety.

Copper-catalyzed intermolecular oxyamination of olefins using carboxylic acids and O-benzoylhydroxylamines

This paper reports a novel approach for the direct and facile synthesis of 1,2-oxyamino moieties via an intermolecular copper-catalyzed oxyamination of olefins. This strategy utilizes O-benzoylhydroxylamines as an electrophilic amine source and carboxylic acids as a nucleophilic oxygen source to achieve a modular difunctionalization of olefins. The reaction proceeded in a regioselective manner with moderate to good yields, exhibiting a broad scope of carboxylic acid, amine, and olefin substrates.

Copper-catalyzed oxyamination of electron-deficient alkenes with N-acyloxyamines

An intermolecular version of copper-catalyzed oxyamination of electron-deficient alkenes by making use of N-acyloxyamines as both amino and oxygen donors was developed.

Manganese-Mediated Coupling Reaction of Vinylarenes and Aliphatic Alcohols

Alcohols and alkenes are the most abundant and commonly used organic building blocks in the large-scale chemical synthesis. Herein, this is the first time to report a novel and operationally simple coupling reaction of vinylarenes and aliphatic alcohols catalyzed by manganese in the presence of TBHP (tert-butyl hydroperoxide). This coupling reaction provides the oxyalkylated products of vinylarenes with good regioselectivity and accomplishes with the principles of step-economies. A possible reaction mechanism has also been proposed.

anti-Selective aminofluorination of alkenes with amidines mediated by hypervalent iodine(iii) reagents

anti-Selective aminofluorination of alkenes with amidines was enabled by hypervalent iodine(iii) reagents, affording 4-fluoroalkyl-2-imidazolines. Further reductive ring-opening of the 2-imidazoline moiety could deliver highly functionalized 3-fluoropropane-1,2-diamine derivatives.