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1.
Nature ; 604(7907): 677-683, 2022 04.
Artículo en Inglés | MEDLINE | ID: mdl-35478236

RESUMEN

The development of catalytic chemical processes that enable the revalorization of nitrous oxide (N2O) is an attractive strategy to alleviate the environmental threat posed by its emissions1-6. Traditionally, N2O has been considered an inert molecule, intractable for organic chemists as an oxidant or O-atom transfer reagent, owing to the harsh conditions required for its activation (>150 °C, 50‒200 bar)7-11. Here we report an insertion of N2O into a Ni‒C bond under mild conditions (room temperature, 1.5-2 bar N2O), thus delivering valuable phenols and releasing benign N2. This fundamentally distinct organometallic C‒O bond-forming step differs from the current strategies based on reductive elimination and enables an alternative catalytic approach for the conversion of aryl halides to phenols. The process was rendered catalytic by means of a bipyridine-based ligands for the Ni centre. The method is robust, mild and highly selective, able to accommodate base-sensitive functionalities as well as permitting phenol synthesis from densely functionalized aryl halides. Although this protocol does not provide a solution to the mitigation of N2O emissions, it represents a reactivity blueprint for the mild revalorization of abundant N2O as an O source.

2.
J Am Chem Soc ; 146(32): 22140-22144, 2024 Aug 14.
Artículo en Inglés | MEDLINE | ID: mdl-39102564

RESUMEN

We present here a catalytic method based on a low-valent Bi complex capable of cyclopropanation of double bonds under blue LED irradiation. The catalysis features various unusual Bi-based organometallic steps, namely, (1) two-electron inner sphere oxidative addition of Bi(I) complex to CH2I2, (2) light-induced homolysis of the Bi(III)-CH2I bond, (3) subsequent iodine abstraction-ring-closing, and (4) reduction of Bi(III) to Bi(I) with an external reducing agent to close the cycle. Stoichiometric organometallic experiments support the proposed mechanism. This protocol represents a unique example of a reductive photocatalytic process based on low-valent bismuth radical catalysis.

3.
J Am Chem Soc ; 145(18): 9988-9993, 2023 May 10.
Artículo en Inglés | MEDLINE | ID: mdl-37126771

RESUMEN

Herein, a regioselective, late-stage two-step arene halogenation method is reported. We propose how unusual Ni(I)/(III) catalysis is enabled by a combination of aryl thianthrenium and Ni redox properties that is hitherto unachieved with other (pseudo)halides. The catalyst is accessed in situ from inexpensive NiCl2·6(H2O) and zinc without the need of supporting ligands.

5.
J Am Chem Soc ; 144(40): 18223-18228, 2022 10 12.
Artículo en Inglés | MEDLINE | ID: mdl-36162124

RESUMEN

Herein we disclose a catalytic synthesis of cycloalkanols that harnesses the potential of N2O as an oxygen transfer agent onto sp3-hybridized carbons. The protocol is distinguished by its mild conditions and wide substrate scope, thus offering an opportunity to access carbocyclic compounds from simple precursors even in an enantioselective manner. Preliminary mechanistic studies suggest that the oxygen insertion event occurs at an alkylnickel species and that N2O is the O transfer reagent.


Asunto(s)
Carbono , Oxígeno , Catálisis
6.
Proc Natl Acad Sci U S A ; 116(18): 8721-8727, 2019 04 30.
Artículo en Inglés | MEDLINE | ID: mdl-30996125

RESUMEN

The union of two powerful transformations, directed C-H activation and decarboxylative cross-coupling, for the enantioselective synthesis of vicinally functionalized alkyl, carbocyclic, and heterocyclic compounds is described. Starting from simple carboxylic acid building blocks, this modular sequence exploits the residual directing group to access more than 50 scaffolds that would be otherwise extremely difficult to prepare. The tactical use of these two transformations accomplishes a formal vicinal difunctionalization of carbon centers in a way that is modular and thus, amenable to rapid diversity incorporation. A simplification of routes to known preclinical drug candidates is presented along with the rapid diversification of an antimalarial compound series.

7.
Angew Chem Int Ed Engl ; 61(23): e202200904, 2022 06 07.
Artículo en Inglés | MEDLINE | ID: mdl-35303387

RESUMEN

(Hetero)arylsulfur compounds where the S atom is in the oxidation state VI represent a large percentage of the molecular functionalities present in organic chemistry. More specifically, (hetero)aryl-SVI fluorides have recently received enormous attention because of their potential as chemical biology probes, as a result of their reactivity in a simple, modular, and efficient manner. Whereas the synthesis and application of the level 1 fluorination at SVI atoms (sulfonyl and sulfonimidoyl fluorides) have been widely studied and reviewed, the synthetic strategies towards higher levels of fluorination (levels 2 to 5) are somewhat more limited. This Minireview evaluates and summarizes the progress in the synthesis of highly fluorinated aryl-SVI compounds at all levels, discussing synthetic strategies, reactivity, the advantages and disadvantages of the synthetic procedures, the proposed mechanisms, and the potential upcoming opportunities.


Asunto(s)
Fluoruros , Halogenación , Fluoruros/química , Oxidación-Reducción
8.
Angew Chem Int Ed Engl ; 61(48): e202211892, 2022 Nov 25.
Artículo en Inglés | MEDLINE | ID: mdl-36137228

RESUMEN

We leveraged the recent increase in synthetic accessibility of SF5 Cl and Ar-SF4 Cl compounds to combine chemistry of the SF5 and SF4 Ar groups with strain-release functionalization. By effectively adding SF5 and SF4 Ar radicals across [1.1.1]propellane, we accessed structurally unique bicyclopentanes, bearing two distinct elements of bioisosterism. Upon evaluating these "hybrid isostere" motifs in the solid state, we measured exceptionally short transannular distances; in one case, the distance rivals the shortest nonbonding C⋅⋅⋅C contact reported to date. This prompted SC-XRD and DFT analyses that support the notion that a donor-acceptor interaction involving the "wing" C-C bonds is playing an important role in stabilization. Thus, these heretofore unknown structures expand the palette for highly coveted three-dimensional fluorinated building blocks and provide insight to a more general effect observed in bicyclopentanes.

9.
Angew Chem Int Ed Engl ; 59(49): 21875-21879, 2020 Dec 01.
Artículo en Inglés | MEDLINE | ID: mdl-32840957

RESUMEN

Redox-active esters (RAEs) as active radical precursors have been extensively studied for C-B bond formations. However, the analogous transformations of stabilized radicals from the corresponding acid precursors remain challenging owing to the strong preference towards single-electron oxidation to the stable carbocations. This work describes a general strategy for rapid access to various aliphatic and aromatic boronic esters by mild photoinduced decarboxylative borylation. Both aryl and alkyl radicals could be generated from the leaving group-assisted N-hydroxybenzimidoyl chloride esters, even α-CF3 substituted substrates could be activated for further elaboration.

10.
J Am Chem Soc ; 141(16): 6726-6739, 2019 04 24.
Artículo en Inglés | MEDLINE | ID: mdl-30943023

RESUMEN

Historically accessed through two-electron, anionic chemistry, ketones, alcohols, and amines are of foundational importance to the practice of organic synthesis. After placing this work in proper historical context, this Article reports the development, full scope, and a mechanistic picture for a strikingly different way of forging such functional groups. Thus, carboxylic acids, once converted to redox-active esters (RAEs), can be utilized as formally nucleophilic coupling partners with other carboxylic derivatives (to produce ketones), imines (to produce benzylic amines), or aldehydes (to produce alcohols). The reactions are uniformly mild, operationally simple, and, in the case of ketone synthesis, broad in scope (including several applications to the simplification of synthetic problems and to parallel synthesis). Finally, an extensive mechanistic study of the ketone synthesis is performed to trace the elementary steps of the catalytic cycle and provide the end-user with a clear and understandable rationale for the selectivity, role of additives, and underlying driving forces involved.


Asunto(s)
Alcoholes/química , Alcoholes/síntesis química , Aminas/química , Aminas/síntesis química , Cetonas/química , Cetonas/síntesis química , Técnicas de Química Sintética , Radicales Libres/química
11.
Angew Chem Int Ed Engl ; 57(44): 14560-14565, 2018 10 26.
Artículo en Inglés | MEDLINE | ID: mdl-30212610

RESUMEN

The direct union of primary, secondary, and tertiary carboxylic acids with a chiral glyoxylate-derived sulfinimine provides rapid access into a variety of enantiomerically pure α-amino acids (>85 examples). Characterized by operational simplicity, this radical-based reaction enables the modular assembly of exotic α-amino acids, including both unprecedented structures and those of established industrial value. The described method performs well in high-throughput library synthesis, and has already been implemented in three distinct medicinal chemistry campaigns.


Asunto(s)
Aminoácidos/síntesis química , Radicales Libres/química , Estereoisomerismo
12.
J Org Chem ; 82(18): 9824-9831, 2017 09 15.
Artículo en Inglés | MEDLINE | ID: mdl-28845667

RESUMEN

A cascade visible-light photocatalytic difluoroalkylation and intramolecular cyclization reaction has been developed for the synthesis of difluoroalkylated oxygen heterocycles. The reaction was carried out under very mild conditions, affording fluorinated isobenzofuran-1-ones, lactone, and cyclic ethers with up to 97% chemical yields. Furthermore, several types of bromofluoroalkane precursors bearing ester, keto, amido, and phosphate groups could all work very well in this reaction, which provides an easy method for the preparation of functionalized difluoroalkylated oxygen heterocycles.

13.
J Org Chem ; 81(19): 9470-9475, 2016 10 07.
Artículo en Inglés | MEDLINE | ID: mdl-27640935

RESUMEN

A thiolation initiated cascade reaction of aryl alkynoates has been developed with thiol as a coupling partner. This radical process has been demonstrated to proceed through S-H bond cleavage, thiolation of alkynoate, aryl migration, and decarboxylation. This reaction tolerates a wide scope of substrates resulting in good chemical yields, which provides an easy and practical strategy for preparation of trisubstituted vinyl sulfides.

14.
J Org Chem ; 80(6): 3151-8, 2015 Mar 20.
Artículo en Inglés | MEDLINE | ID: mdl-25742029

RESUMEN

A metal-free cyclization reaction of 2-isocyanobiphenyls with amide derivatives by using tert-butyl peroxybenzoate (TBPB) as oxidant was developed, which provided an access to pharmacologically interesting 6-amidophenanthridine compounds. The reactions proceeded through a sequence of functionalization of the C(sp(3))-H bond adjacent to the nitrogen atom and intramolecular radical aromatic cyclization with good chemistry yields.

15.
Org Lett ; 2024 Aug 23.
Artículo en Inglés | MEDLINE | ID: mdl-39177147

RESUMEN

α-Amino-CF3 compounds are widely employed in bio- and pharmaceutical chemistry for improved stability and bioactivities. Traditional methods often face challenges with functional group tolerance and lack a general approach for late-stage functionalization. Herein, we report a new type of redox-active α-amino-CF3 reagents, easily prepared from trifluoro acetaldehyde hydrates. These α-amino-CF3 reagents can serve as versatile building blocks for coupling with alkynyl bromides, aryl bromides, and enol triflates under nickel catalysis.

16.
Nat Commun ; 15(1): 6116, 2024 Jul 20.
Artículo en Inglés | MEDLINE | ID: mdl-39033147

RESUMEN

Alkylamine structures represent one of the most functional and widely used in organic synthesis and drug design. However, the general methods for the functionalization of the shielded and deshielded alkyl radicals remain elusive. Here, we report a general deoxygenative amination protocol using alcohol-derived carbazates and nitrobenzene under electrochemical conditions. A range of primary, secondary, and tertiary alkylamines are obtained. This practical procedure can be scaled up through electrochemical continuous flow technique.

17.
Org Lett ; 25(31): 5822-5826, 2023 Aug 11.
Artículo en Inglés | MEDLINE | ID: mdl-37523267

RESUMEN

Bimolecular nucleophilic substitution SN2 is the earliest and most important means of amination of alkyl electrophiles; its practical utilization is largely limited to primary or activated substrates. Furthermore, a persistent challenge lies in establishing C(sp3)-N bonds from alkyl substrates in cross-coupling chemistry using palladium and nickel catalysts. Therefore, the methods of constructing C(sp3)-N bonds remain rare from alkyl electrophiles. The existing routes are limited to copper catalysis and photoredox catalysis. Here, we demonstrate an alternative amination strategy for rapid construction of C(sp3)-N bonds from accessible alkyl electrophiles, which were used as radical precursors under nickel catalysis by Ni (III) species reductive eliminations in high efficiency.

18.
Org Lett ; 25(51): 9225-9230, 2023 Dec 29.
Artículo en Inglés | MEDLINE | ID: mdl-38113061

RESUMEN

Due to the presence of carbon-carbon double bonds, 1,3-dienes exhibit great reactivity. A protocol for the site-selective diarylation of terminal 1,3-dienes is reported here. The transformation is facilitated by the Ni catalyst without the need for additional ligands, utilizing an electrochemical setup. Preliminary results indicate that by introducing chiral ligands moderate enantioselective diarylation products can be obtained. This method affords diversely substituted diarylated products that occur as structural motifs in various natural products.

19.
Org Lett ; 24(20): 3647-3651, 2022 May 27.
Artículo en Inglés | MEDLINE | ID: mdl-35579336

RESUMEN

Compared with conventional reductive coupling, reductive coupling under electrochemical conditions without external reductants is greener, milder, and more efficient and is of increasing interest to organic chemists. In this work, we report the sacrificial anode, nickel-catalyzed electrochemical allylation reaction of aryl and alkyl halides. The reaction can be applied to a range of allylation reagents such as trifluoroalkenes, oxalates, and acetates.

20.
Chem Sci ; 13(7): 1946-1950, 2022 Feb 16.
Artículo en Inglés | MEDLINE | ID: mdl-35308850

RESUMEN

A photocatalyzed 1,3-boron shift of allylboronic esters is reported. The boron atom migration through the allylic carbon skeleton proceeds via consecutive 1,2-boron migrations and Smiles-type rearrangement to furnish a variety of terminally functionalized alkyl boronates. Several types of migrating variations of heteronuclei radicals and dearomatization processes are also tolerated, allowing for further elaboration of highly functionalized boron-containing frameworks.

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