Metal-catalyzed Markovnikov-type selective hydrofunctionalization of terminal alkynes.

Metal-catalyzed highly Markovnikov-type selective hydrofunctionalization of terminal alkynes provides a straightforward and atom-economical route to access 1,1-disubstituted alkenes, which have a wide range of applications in organic synthesis. However, the highly Markovnikov-type selective transformations are challenging due to the electronic and steric effects during the addition process. With the development of metal-catalyzed organic synthesis, different metal catalysts have been developed to solve this challenge, especially for platinum group metal catalysts. In this perspective, we review homogeneous metal-catalyzed Markovnikov-type selective hydrofunctionalization of terminal alkynes according to the classified element types as well as reaction mechanisms. Future avenues for investigation are also presented to help expand this exciting field.

Recent advancements in metal-catalyst-free multicomponent radical sulfonylation of alkynes.

Vinyl sulfones are crucial building blocks in synthetic chemistry and core structural units of pharmaceutically active molecules, thus extensive investigations have been conducted on the construction of these skeletons. In contrast to the classical synthetic approaches, the radical sulfonylation of alkynes for producing vinyl sulfones has garnered considerable interest because of its mild conditions and high efficiency. Radical sulfonation of alkynes typically begins with the sulfonyl radical attacking the alkynes, followed by further functionalization. Moreover, the association of metal-catalyst-free systems with multicomponent reactions (MCRs) offers an environmentally friendly pathway for efficiently constructing complex scaffolds from readily available partners. However, there is no comprehensive review summarizing the advancements in metal-catalyst-free multicomponent radical sulfonylation of alkynes. Hence, we provide a categorical overview based on the objects of sulfonylation of alkynes (hydrosulfonylation, carbosulfonylation, aminosulfonylation, oxysulfonylation, sulfosulfonylation, selenosulfonylation, and iodosulfonylation), along with interpretations of the reaction mechanisms.

Chemodivergent Tandem Radical Cyclization of Alkene-Substituted Quinazolinones: Rapid Access to Mono- and Di-Alkylated Ring-Fused Quinazolinones.

Chemodivergent tandem radical cyclization offers exciting possibilities for the synthesis of structurally diverse cyclic compounds. Herein, we revealed a chemodivergent tandem cyclization of alkene-substituted quinazolinones under metal- and base-free conditions, this transformation is initiated by alkyl radicals produced from oxidant-induced α-C(sp3 )-H functionalization of alkyl nitriles or esters. The reaction resulted in the selective synthesis of a series of mono- and di-alkylated ring-fused quinazolinones by modulating the loading of oxidant, reaction temperature, and reaction time. Mechanistic investigations show that the mono-alkylated ring-fused quinazolinones is constructed by the key process of 1,2-hydrogen shift, whereas the di-alkylated ring-fused quinazolinones is mainly achieved through crucial steps of resonance and proton transfer. This protocol is the first example of remote second alkylation on the aromatic ring via α-C(sp3 )-H functionalization and difunctionalization achieved by association of two unsaturated bonds in radical cyclization.

Applications of sulfonyl hydrazides in radical cyclization of alkenes.

Radical cyclization is regarded as a powerful and promising strategy for the assembly of diverse important cyclic structures because of its high atom- and step-economy. As excellent radical acceptors, alkenes offer two potential directions, pushing the research domain of radical cyclization. In this context, as a radical precursor, sulfonyl hydrazide plays an important role in accomplishing radical cyclization of alkenes in a facile and efficient way. This review focuses on the applications of sulfonyl hydrazides in radical cyclization of alkenes, which generally has two radical conversion modes, sulfonyl radicals and sulfoxide radicals. In particular, the section of sulfonyl radicals consists of eight parts containing aromatic rings, alkenes, alkynes, cyanides, aldehydes, carboxylic acids, amides, and small ring compounds, according to the objects of cyclization after addition with alkenes. Within each category, representative instances are presented and discussed in terms of their general mechanistic perspectives when needed.

Recent advances in radical-mediated intermolecular (4 + 2) cycloaddition.

(4 + 2) Cycloaddition plays an important role in the synthesis of versatile carbocyclic/heterocyclic compounds with its high atom- and step-economy. Additionally, with mild conditions and indispensable functional group compatibility, the radical reaction has been recognized as a useful tool in organic chemistry. Given the enormous impact of radical-mediated (4 + 2) cycloaddition processes and their promising applications, we summarize and highlight the recent works in this attractive area. On the basis of the types of radicals that initiate different (4 + 2) cycloaddition processes, we classify them into processes involving alkenyl cations or alkenyl radicals, aryl radicals, acyl radicals, alkyl radicals, and heteroatom radicals, and this review places special emphasis on the reaction design and mechanisms, which will stimulate future developments in radical-mediated intermolecular (4 + 2) cycloaddition.

Cyclization/hydrolysis of 1,5-enenitriles initiated by sulfonyl radicals in the aqueous phase in the presence of the I2/TBHP system.

A novel cyclization/hydrolysis of 1,5-enenitriles for the synthesis of valuable pyrrolidine-2,4-diones in the aqueous phase using I2 as the catalyst and tert-butyl hydroperoxide (TBHP) as the oxidant is reported. In the presence of the I2/TBHP system, sulfonyl hydrazides produce sulfonyl radicals, which undergo radical addition, intramolecular cyclization, hydrogen abstraction, and hydrolysis to give the final products. The use of the inexpensive and environmentally friendly I2/TBHP catalytic oxidation system in the aqueous phase makes it a benign and sustainable strategy.

The polychloromethylation/acyloxylation of 1,6-enynes with chloroalkanes and diacyl peroxides through dual-role designs.

The novel polychloromethylation/acyloxylation of 1,6-enynes with chloroalkanes and diacyl peroxides through dual-role designs has been developed to prepare 2-pyrrolidinone derivatives with polychloromethyl units with the use of an inexpensive copper salt under mild conditions. This strategy includes two dual-role designs, not only improving atomic utilization but also allowing a cleaner process. The wide substrate scope and simple reaction conditions demonstrate the practicability of this protocol.

The construction of benzimidazo[2,1-a]isoquinolin-6(5H)-ones from N-methacryloyl-2-phenylbenzoimidazoles through radical strategies.

Benzimidazo[2,1-a]isoquinolin-6(5H)-one constitutes a structurally unique class of tetracyclic N-heterocycles that are found throughout a myriad of biologically active natural products, pharmaceutical compounds, and functional materials. Various synthetic routes for the preparation of benzimidazo[2,1-a]isoquinolin-6(5H)-ones have been reported. In particular, the use of N-methacryloyl-2-phenylbenzoimidazoles to construct benzimidazo[2,1-a]isoquinolin-6(5H)-ones through various radical strategies have attracted widespread attention due to the versatility and simple preparation of raw materials, as well as the step-economy and mild reaction conditions. Using representative examples, we highlight significant progress in the synthesis of benzimidazo[2,1-a]isoquinolin-6(5H)-ones, including the selection of the catalytic system, substrate scope, mechanistic understanding, and applications. The contents of this review focus on the development of C-, S-, P-, and Si-centered radical addition-intramolecular cyclization strategies.

Recent progress in the radical α-C(sp3)-H functionalization of ketones.

The direct use structurally simple ketones as α-ketone radical sources for α-C(sp3)-H functionalization is a sustainable and powerful approach for constructing complex and multifunctional chemical scaffolds with diverse applications. The reactions of α-ketone radicals with alkenes, alkynes, enynes, imides, and imidazo[1,2-a]pyridines have broadened the structural diversity and complexity of ketones. Through chosen illustrative examples, we outline the recent progress in the development of methods that enable the radical α-C(sp3)-H functionalization of ketones, with an emphasis on radical initiation systems and possible mechanisms of the transformations. The application of these strategies is illustrated by the synthesis of several biologically active molecules and drug molecules. Further subdivision is based on substrate type and reaction type.

Selective divergent radical cyclization of 1,6-dienes with alkyl nitriles.

An efficient, selective, and step economical radical cyclization of 1,6-dienes with alkyl nitriles initiated by α-C(sp3)-H functionalization under the Sc(OTf)3 and Ag2CO3 system is described here. The selective divergent cyclization relies on the substitution effect at the α-position of the acrylamide moiety and nitriles, which is terminated by hydrogen abstraction, direct cyclization with the aryl ring, or further cyclization with the CN bond and hydrolysis, respectively.

The Assessment of Sleep Quality in Patients Following Valve Repair and Valve Replacement for Infective Endocarditis: A Retrospective Study at a Single Center.

BACKGROUND The aim of this study was to measure sleep quality among patients who underwent infective endocarditis (IE) surgery and identify the risk factors involved in sleep disorders. MATERIAL AND METHODS In this study, we used actigraphy, the Pittsburgh Sleep Quality Index (PSQI), and Epworth Sleep Scale (ESS) to determine the clinical characteristics of sleep disorders in 116 patients with IE who were in rehabilitation after surgery. RESULTS Our results showed that 46 (39.7%) patients had sleep efficiency over 85%, while 70 (60.3%) patients had sleep efficiency below 85%. The correlation analysis showed that sleep efficiency was related to the duration of the disease, with a longer duration leading to lower sleep efficiency (P=0.031). The sleep efficiency of patients with IE following surgery was also affected by alcohol consumption; however, surprisingly, patients with "heavy" alcohol consumption had higher sleep efficiency (P=0.030). We found a significant correlation between sleep efficiency and postoperative interleukin-6 (IL) levels, C-reactive protein (CRP) levels, and preoperative erythrocyte sedimentation rate (P<0.05). No significant correlation was found between brain natriuretic peptide levels and sleep efficiency, PSQI score, or ESS score. Postoperative hemoglobin (Hb) level was associated with sleep efficiency (R=0.194, P=0.036), but there was no statistically significant correlation between the PSQI and ESS scores. Postoperative alanine transaminase (ALT) showed a significant negative correlation with sleep efficiency (R=-0.27, P=0.003). CONCLUSIONS We found a high prevalence of sleep disorders in patients with IE along with an increase in inflammatory factors, including postoperative IL-6, CRP, ALT, and Hb levels.

Radical cyclizations of enynes/dienes with alcohols in water using a green oxidant.

A simple, eco-friendly, and efficient methodology for performing radical cyclizations of enynes/dienes with alcohols in water has been established. This methodology showed ease of scale up, and it was designed to use mild reaction conditions and no catalyst. It was also designed to employ K2S2O8 as a green oxidant and water as the solvent, conditions making this process clean and easy to operate, hence achieving the criteria of green chemistry.

Base-promoted domino radical cyclization of 1,6-enynes.

A good regioselective, high atom-economical and transition-metal-free method for the synthesis of α-functionalized ether derivatives via the domino radical cyclization of 1,6-enynes is described. A series of α-functionalized ether derivatives could be easily obtained in good yields with wide functional group tolerance by using less toxic and inexpensive Cs2CO3 as the base. The control experiment results show that the reaction involves a radical process. This strategy provides a regioselective way toward the formation of dual C-C bonds in one step.

Metal-Free C(sp3)-H Azidation in a Radical Strategy for the Synthesis of 3-Azido-2-oxindoles at Room Temperature.

A novel and environmentally attractive C(sp3)-H azidation of 2-oxindoles involving the formation of a C-N bond was developed. This methodology achieved for the first time 3-azido-2-oxindole construction under metal-free conditions at room temperature via a radical strategy. PhI(OAc)2 was used as the oxidant and Et3N was used as the additive in this transformation. Furthermore, the mechanistic study indicated that this azidation involved a radical process.

miR-422a inhibits cell proliferation in colorectal cancer by targeting AKT1 and MAPK1.

BACKGROUND: miRNAs are regarded as molecular biomarkers and therapeutic targets for colorectal cancer (CRC), a series of miRNAs have been proven to involve into CRC carcinogenesis, invasion and metastasis. Aberrant miR-422a expression and its roles have been reported in some cancers. However, the function and underlying mechanism of miR-422a in the progression of CRC remain largely unknown. METHODS: Real-time PCR were used to quantify miR-422a expression in CRC tissues. Both vivo and vitro functional assays showed miR-422a inhibits CRC cell proliferation. Target prediction program (miRBase) and luciferase reporter assays were conducted to confirm the target genes AKT1 and MAPK1 of miR-422a. Specimens from 50 patients with CRC were analyzed for the correlation between the expression of miR-422a and the expression of the target genes AKT1 and MAPK1 by real-time PCR. RESULTS: MiR-422a was down­regulated in CRC tissues and cell lines. Ectopic expression of miR-422a inhibited cell proliferation and tumor growth ability; inhibition of endogenous miR-422a, by contrast, promoted cell proliferation and tumor growth ability of CRC cells. MiR-422a directly targets 3'-UTR of the AKT1 and MAPK1, down-regulation of miR-422a led to the activation of Raf/MEK/ERK and PI3K/AKT signaling pathways to promote cell proliferation in CRC. In addition, miR-422a expression was negatively correlated with the expressions of AKT1 and MAPK1 in CRC tissues. CONCLUSION: miR-422a inhibits cell proliferation in colorectal cancer by targeting AKT1 and MAPK1.

Metal-free synthesis of isatin oximes via radical coupling reactions of oxindoles with t-BuONO in water.

A metal-free method for the synthesis of isatin oximes was developed through the radical coupling reactions of oxindoles with t-BuONO. This protocol provides a practical and environmentally benign method for the construction of C-N bonds in water at room temperature without using any other reagents. The advantages of this strategy are its mild reaction conditions and clean procedure.

Palladium-catalyzed oxidative difunctionalization of alkenes with α-carbonyl alkyl bromides initiated through a Heck-type insertion: a route to indolin-2-ones.

The oxidative interception of various σ-alkyl palladium(II) intermediates with additional reagents for the difunctionalization of alkenes is an important research area. A new palladium-catalyzed oxidative difunctionalization reaction of alkenes with α-carbonyl alkyl bromides is described, in which the σ-alkyl palladium(II) intermediate is generated through a Heck insertion and trapped using an aryl C(sp(2))-H bond. This method can be applied to various α-carbonyl alkyl bromides, including primary, secondary, and tertiary α-bromoalkyl esters, ketones, and amides.

Copper-Catalyzed Radical Relay 1,3-Carbocarbonylation across Two Distinct C═C Bonds.

The radical relay provides an effective paradigm for intermolecular assembly to achieve functionalization across remote chemical bonds. Herein, we report the first radical relay 1,3-carbocarbonylation of α-carbonyl alkyl bromides across two separate C═C bonds. The reaction is highly chemo- and regioselective, with two C(sp3)-C(sp3) bonds and one C═O bond formed in a single orchestrated operation. In addition, the synthesis method under mild conditions and using inexpensive copper as the catalyst allows facile access to structurally diverse 1,3-carbocarbonylation products. The plausible mechanism is investigated through a series of control experiments, including radical trapping, radical clock experiments, critical intermediate trapping, and 18O labeling experiment.

Dual Nickel/Photoredox-Catalyzed Arylsulfonylation of Allenes.

The nickel/photoredox dual catalysis system is an efficient conversion platform for the difunctionalization of unsaturated hydrocarbons. Herein, we disclose the first dual nickel/photoredox-catalyzed intramolecular 1,2-arylsulfonylation of allenes, which can accurately construct a C(sp2)-C(sp2) bond and a C(sp3)-S bond. The reaction exhibits excellent chemoselectivity and regioselectivity, allowing modular conformations of a diverse series of 3-sulfonylmethylbenzofuran derivatives. Control experiments showed that the bipyridine ligand is crucial for the formation of a stable σ-alkyl nickel intermediate, providing the possibility for sulfonyl radical insertion. Meanwhile, the electrophilic sulfonyl radical facilitates further oxidative addition of the σ-alkyl nickel intermediate and inhibits addition with allenes. In addition, control experiments, cyclic voltammetry tests, Stern-Volmer experiments, and density functional theory calculations afford evidence for the Ni(0)/Ni(I)/Ni(II)/Ni(III) pathway in this 1,2-arylsulfonylation.

Four-Component Radical 1,2-Selenosulfonylation of Allenes.

Selenosulfones, as pivotal pharmaceutical molecule frameworks, have become a research hotspot in modern organic synthesis due to their vital need for efficient preparation. Herein, we have developed an iron-catalyzed four-component controllable radical tandem reaction of allenes involving cycloketone oxime esters, 1,4-diazabicyclo[2.2.2]octane bis(sulfur dioxide) adduct (DABSO), and diphenyl diselenides for the synthesis of complex selenosulfones. This is the first case of achieving the 1,2-selenosulfonylation of allenes via a radical process, wherein precise control of radical rates and polarity matching enhance high regioselective conversion. The reaction conditions are ecofriendly and mild with step-efficiency by forming two new C-S bonds and one C-Se bond in one pot. Moreover, the 1,2-selenosulfonylation of allenes can be achieved by replacing cycloketone oxime esters with aryldiazonium tetrafluoroborates in this system.