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The Journal of Organic Chemistry Aug 2022Here, we present a visible light-catalyzed hydroalkylation of aryl-alkenes affording C-C bonds using aryl-alkenes and alkyl iodides. We demonstrate the formation of...
Here, we present a visible light-catalyzed hydroalkylation of aryl-alkenes affording C-C bonds using aryl-alkenes and alkyl iodides. We demonstrate the formation of various hydroalkylation products in excellent yields, with primary, secondary, and tertiary alkyl iodides being tolerated in the reaction. Mechanistic experiments reveal a pathway consisting of halogen atom transfer followed by a radical-polar crossover mechanism delivering the desired hydroalkylation products.
Topics: Alkenes; Alkylation; Halogens; Iodides
PubMed: 35914236
DOI: 10.1021/acs.joc.2c01304 -
Molecules (Basel, Switzerland) Apr 2020The interest of organoboron chemistry in organic synthesis is growing, together with the development of new and versatile polyborated reagents. Here, the preparation of... (Review)
Review
The interest of organoboron chemistry in organic synthesis is growing, together with the development of new and versatile polyborated reagents. Here, the preparation of 1,1,1-tri(boryl)alkanes, 1,2,3-tri(boryl)alkanes, 1,1,2-tri(boryl)alkanes, as well as 1,1,2-tri(boryl)alkenes as suitable and accessible polyborated systems is demonstrated as being easily applied in the construction of new carbon-carbon and carbon-heteroatom bonds. Synthetic procedures and limitations have been collected to demonstrate the powerful strategies to construct selective molecules, taking advantages of the easy transformation of carbon-boron bond in multiple functionalities, under the total control of chemo- and stereoselectivity.
Topics: Alkenes; Chemistry Techniques, Synthetic; Models, Chemical; Stereoisomerism
PubMed: 32290330
DOI: 10.3390/molecules25071758 -
Journal of the American Chemical Society Sep 2022Photochemical dearomative cycloaddition has emerged as a useful strategy to rapidly generate molecular complexity. Within this context, stereo- and regiocontrolled...
Photochemical dearomative cycloaddition has emerged as a useful strategy to rapidly generate molecular complexity. Within this context, stereo- and regiocontrolled intermolecular -cycloadditions are rare. Herein, a method to achieve photochemical cycloaddition of quinolines and alkenes is shown. Emphasis is placed on generating sterically congested products and reaction of highly substituted alkenes and allenes. In addition, the mechanistic details of the process are studied, which revealed a reversible radical addition and a selectivity-determining radical recombination. The regio- and stereochemical outcome of the reaction is also rationalized.
Topics: Alkenes; Catalysis; Cycloaddition Reaction; Molecular Structure; Quinolines
PubMed: 36106902
DOI: 10.1021/jacs.2c07726 -
Angewandte Chemie (International Ed. in... Dec 2015Although recent years have witnessed significant advances in the development of catalytic, enantioselective halofunctionalizations of alkenes, the related dihalogenation... (Review)
Review
Although recent years have witnessed significant advances in the development of catalytic, enantioselective halofunctionalizations of alkenes, the related dihalogenation of olefins to afford enantioenriched vicinal dihalide products remains comparatively underdeveloped. However, the growing number of complex natural products bearing halogen atoms at stereogenic centers has underscored this critical gap in the synthetic chemist's arsenal. This Review highlights the selectivity challenges inherent in the design of enantioselective dihalogenation processes, and formulates a mechanism-based classification of alkene dihalogenations, including those that may circumvent the "classical" haliranium (or alkene-dihalogen π-complex) intermediates. A variety of metal and main group halide reagents that have been used for the dichlorination or dibromination of alkenes are discussed, and the proposed mechanisms of these transformations are critically evaluated.
Topics: Alkenes; Catalysis; Halogens; Stereoisomerism
PubMed: 26630449
DOI: 10.1002/anie.201507152 -
Molecules (Basel, Switzerland) Feb 2023Carbonyl olefinations are among the most important organic syntheses that form C=C bonds, as they usually have high yields and in addition offer excellent... (Review)
Review
Carbonyl olefinations are among the most important organic syntheses that form C=C bonds, as they usually have high yields and in addition offer excellent stereoselectivity. Due to these advantages, carbonyl olefinations have important pharmaceutical and industrial applications. These reactions contain an additional step of an α-functionalized carbanion to an aldehyde or ketone to produce alkenes, but syntheses performed using metal carbene complexes are also known. The Wittig reaction is an example of carbonyl olefination, one of the best ways to synthesize alkenes. This involves the chemical reaction between an aldehyde or ketone with a so-called Wittig reagent, for instance phosphonium ylide. Triphenylphosphine-derived ylides and trialkylphosphine-derived ylides are the most common phosphorous compounds used as Wittig reagents. The Wittig reaction is commonly involved in the synthesis of novel anti-cancer and anti-viral compounds. In recent decades, the use of ultrasound on the Wittig reaction (and on different modified Wittig syntheses, such as the Wittig-Horner reaction or the aza-Wittig method) has been studied as a green synthesis. In addition to the advantage of green synthesis, the use of ultrasounds in general also improved the yield and reduced the reaction time. All of these chemical syntheses conducted under ultrasound will be described further in the present review.
Topics: Molecular Structure; Sonication; Alkenes; Aldehydes
PubMed: 36838946
DOI: 10.3390/molecules28041958 -
Molecules (Basel, Switzerland) Oct 2016Results of research into four-membered 2-halo-1,2λ⁵-oxaphosphetane phosphorus(V)-heterocycles are presented. The preparation of 2-halo-1,2λ⁵-oxaphosphetanes by... (Review)
Review
Results of research into four-membered 2-halo-1,2λ⁵-oxaphosphetane phosphorus(V)-heterocycles are presented. The preparation of 2-halo-1,2λ⁵-oxaphosphetanes by reaction of haloylides with carbonyl compounds is described. The mechanism of asynchronous [2+2]-сycloaddition of ylides to aldehydes was proposed on the base of low-temperature NMR investigations. 2-Halo-1,2λ⁵-oxaphosphetanes were isolated as individual compounds and their structures were confirmed by ¹Н-, C-, F- and Р-NMR spectra. These compounds are convenient reagents for preparing of various organic and organophosphorus compounds hardly available by other methods. Chemical and physical properties of the 2-halo-1,2λ⁵-oxaphosphetanes are reviewed. The 2-chloro-1,2λ⁵-oxaphosphetanes, rearrange with formation of 2-chloroalkyl-phosphonates or convert into -phosphorylated alkenes depending on the substituents at the α-carbon atom. Prospective synthetic applications of 2-halo-1,2λ⁵-oxaphosphetanes are analyzed. The 2-halo-1,2λ⁵-oxaphosphetanes may be easily converted to various alkenylphosphonates: allyl- or vinylphosphonates, phosphorus ketenes, thioketenes, ketenimines.
Topics: Aldehydes; Alkenes; Carbon; Cycloaddition Reaction; Heterocyclic Compounds; Magnetic Resonance Spectroscopy; Molecular Structure; Organophosphorus Compounds; Stereoisomerism
PubMed: 27763512
DOI: 10.3390/molecules21101371 -
Journal of the American Chemical Society Jan 2023Intermolecular cyclopropanation of mono-, di-, and trisubstituted olefins with α-bromo-β-ketoesters and α-bromomalonates under organophotocatalysis is reported. The...
Intermolecular cyclopropanation of mono-, di-, and trisubstituted olefins with α-bromo-β-ketoesters and α-bromomalonates under organophotocatalysis is reported. The reaction displays broad functional group tolerance, including substrates bearing acids, alcohols, halides, ethers, ketones, nitriles, esters, amides, carbamates, silanes, stannanes, boronic esters, as well as arenes, and furnishes highly substituted cyclopropanes. The transformation may be performed in the presence of air and moisture with 0.5 mol % of a benzothiazinoquinoxaline as organophotocatalyst. Mechanistic investigations, involving Stern-Volmer quenching, quantum yield determination, and deuteration experiments, are carried out, and a catalytic cycle for the transformation is discussed.
Topics: Molecular Structure; Alkenes; Stereoisomerism; Cyclization; Amides; Catalysis
PubMed: 36607827
DOI: 10.1021/jacs.2c11680 -
Environmental Science and Pollution... Sep 2022Chemical signature of airborne particulates and deposition dusts is subject of study since decades. Usually, three complementary composition markers are investigated,... (Review)
Review
Chemical signature of airborne particulates and deposition dusts is subject of study since decades. Usually, three complementary composition markers are investigated, namely, (i) specific organic compounds; (ii) concentration ratios between congeners, and (iii) percent distributions of homologs. Due to its intrinsic limits (e.g., variability depending on decomposition and gas/particle equilibrium), the identification of pollution sources based on molecular signatures results overall restricted to qualitative purposes. Nevertheless, chemical fingerprints allow drawing preliminary information, suitable for successfully approaching multivariate analysis and valuing the relative importance of sources. Here, the state-of-the-art is presented about the molecular fingerprints of non-polar aliphatic, polyaromatic (PAHs, nitro-PAHs), and polar (fatty acids, organic halides, polysaccharides) compounds in emissions. Special concern was addressed to alkenes and alkanes with carbon numbers ranging from 12 to 23 and ≥ 24, which displayed distinct relative abundances in petrol-derived spills and exhausts, emissions from microorganisms, high vegetation, and sediments. Long-chain alkanes associated with tobacco smoke were characterized by a peculiar iso/anteiso/normal homolog fingerprint and by n-hentriacontane percentages higher than elsewhere. Several concentration ratios of PAHs were identified as diagnostic of the type of emission, and the sources of uncertainty were elucidated. Despite extensive investigations conducted so far, the origin of uncommon molecular fingerprints, e.g., alkane/alkene relationships in deposition dusts and airborne particles, remains quite unclear. Polar organics resulted scarcely investigated for pollution apportioning purposes, though they looked as indicative of the nature of sources. Finally, the role of humans and living organisms as actual emitters of chemicals seems to need concern in the future.
Topics: Air Pollutants; Alkanes; Alkenes; Carbon; Dust; Environmental Monitoring; Fatty Acids; Humans; Particulate Matter; Polycyclic Aromatic Hydrocarbons; Tobacco Smoke Pollution
PubMed: 35876994
DOI: 10.1007/s11356-022-21531-0 -
Chemistry (Weinheim An Der Bergstrasse,... Nov 2022The "metathesis reaction" is a straightforward and often metal-catalyzed chemical reaction that transforms two hydrocarbon molecules to two new hydrocarbons by exchange... (Review)
Review
The "metathesis reaction" is a straightforward and often metal-catalyzed chemical reaction that transforms two hydrocarbon molecules to two new hydrocarbons by exchange of molecular fragments. Alkane, alkene and alkyne metathesis have become an important tool in synthetic chemistry and have provided access to complex organic structures. Since the discovery of industrial olefin metathesis in the 1960s, many modifications have been reported; thus, increasing scope and improving reaction selectivity. Olefin metathesis catalysts based on high-valent group six elements or Ru(IV) have been developed and improved through ligand modifications. In addition, significant effort was invested to realize olefin metathesis with a non-toxic, bio-compatible and one of the most abundant elements in the earth's crust; namely, iron. First evidences suggest that low-valent Fe(II) complexes are active in olefin metathesis. Although the latter has not been unambiguously established, this review summarizes the key advances in the field and aims to guide through the challenges.
Topics: Alkenes; Iron; Catalysis; Hydrocarbons; Ligands
PubMed: 35770829
DOI: 10.1002/chem.202201414 -
Molecules (Basel, Switzerland) Feb 2023In this review, the latest achievements in the field of multiply bonded organogermanium derivatives, mostly reported within the last two decades, are presented. The... (Review)
Review
In this review, the latest achievements in the field of multiply bonded organogermanium derivatives, mostly reported within the last two decades, are presented. The isolable Ge-containing analogues of alkenes, alkynes, 1,3-dienes, allenes, and vinylidenes are discussed, and for each class of unsaturated organogermanium compounds, the most representative examples are given. The synthetic approaches toward homonuclear multiply bonded combinations solely consisting of germanium atoms, and their heteronuclear variants containing germanium and other group 14 elements, both acyclic and cyclic, are discussed. The peculiar structural features and nonclassical bonding nature of the abovementioned compounds are discussed based on their spectroscopic and structural characteristics, in particular their crystallographic parameters (double bond length, -bending at the doubly bonded centers, and twisting about the double bond). The prospects for the practical use of the title compounds in synthetic and catalytic fields are also briefly discussed.
Topics: Alkenes; Alkynes; Germanium; Alkadienes
PubMed: 36838546
DOI: 10.3390/molecules28041558