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Keywords = aza-ylide

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58 pages, 24396 KiB  
Review
Density Functional Theory Calculations: A Useful Tool to Investigate Mechanisms of 1,3-Dipolar Cycloaddition Reactions
by Maria Assunta Chiacchio and Laura Legnani
Int. J. Mol. Sci. 2024, 25(2), 1298; https://doi.org/10.3390/ijms25021298 - 20 Jan 2024
Cited by 13 | Viewed by 5355
Abstract
The present review contains a representative sampling of mechanistic studies, which have appeared in the literature in the last 5 years, on 1,3-dipolar cycloaddition reactions, using DFT calculations. Attention is focused on the mechanistic insights into 1,3-dipoles of propargyl/allenyl type and allyl type [...] Read more.
The present review contains a representative sampling of mechanistic studies, which have appeared in the literature in the last 5 years, on 1,3-dipolar cycloaddition reactions, using DFT calculations. Attention is focused on the mechanistic insights into 1,3-dipoles of propargyl/allenyl type and allyl type such as aza-ylides, nitrile oxides and azomethyne ylides and nitrones, respectively. The important role played by various metal–chiral–ligand complexes and the use of chiral eductors in promoting the site-, regio-, diastereo- and enatioselectivity of the reaction are also outlined. Full article
(This article belongs to the Special Issue Molecular Simulation and Modeling)
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20 pages, 7680 KiB  
Review
Wittig and Wittig–Horner Reactions under Sonication Conditions
by Gheorghe Ilia, Vasile Simulescu, Nicoleta Plesu, Vlad Chiriac and Petru Merghes
Molecules 2023, 28(4), 1958; https://doi.org/10.3390/molecules28041958 - 18 Feb 2023
Cited by 4 | Viewed by 7377
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Advances in Ultrasound Chemistry)
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11 pages, 1131 KiB  
Communication
Ortho-Phosphinoarenesulfonamide-Mediated Staudinger Reduction of Aryl and Alkyl Azides
by Xingzhuo Li, Zhenguo Wang, Wenjun Luo, Zixu Wang, Keshu Yin and Le Li
Molecules 2022, 27(17), 5707; https://doi.org/10.3390/molecules27175707 - 5 Sep 2022
Cited by 4 | Viewed by 3490
Abstract
Conventional Staudinger reductions of organic azides are sluggish with aryl or bulky aliphatic azides. In addition, Staudinger reduction usually requires a large excess of water to promote the decomposition of the aza-ylide intermediate into phosphine oxide and amine products. To overcome the [...] Read more.
Conventional Staudinger reductions of organic azides are sluggish with aryl or bulky aliphatic azides. In addition, Staudinger reduction usually requires a large excess of water to promote the decomposition of the aza-ylide intermediate into phosphine oxide and amine products. To overcome the challenges above, we designed a novel triaryl phosphine reagent 2c with an ortho-SO2NH2 substituent. Herein, we report that such phosphine reagents are able to mediate the Staudinger reduction of both aryl and alkyl azides in either anhydrous or wet solvents. Good to excellent yields were obtained in all cases (even at a diluted concentration of 0.01 M). The formation of B-TAP, a cyclic aza-ylide, instead of phosphine oxide, eliminates the requirement of water in the Staudinger reduction. In addition, computational studies disclose that the intramolecular protonation of the aza-ylide by the ortho-SO2NH2 group is kinetically favorable and responsible for the acceleration of Staudinger reduction of the aryl azides. Full article
(This article belongs to the Special Issue Modern Organophosphorus Chemistry)
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18 pages, 4136 KiB  
Review
Recent Advances in C–C and C–N Bond Forming Reactions Catalysed by Polystyrene-Supported Copper Complexes
by Pavel Drabina, Jan Svoboda and Miloš Sedlák
Molecules 2017, 22(6), 865; https://doi.org/10.3390/molecules22060865 - 24 May 2017
Cited by 27 | Viewed by 7147
Abstract
This present mini-review covers recently published results on Cu(I) and Cu(II) complexes immobilized on polystyrene carriers, which are used as heterogeneous, eco-friendly reusable catalysts applied for carbon–carbon and carbon–nitrogen forming reactions. Recent advances and trends in this area are demonstrated in the examples [...] Read more.
This present mini-review covers recently published results on Cu(I) and Cu(II) complexes immobilized on polystyrene carriers, which are used as heterogeneous, eco-friendly reusable catalysts applied for carbon–carbon and carbon–nitrogen forming reactions. Recent advances and trends in this area are demonstrated in the examples of oxidative homocoupling of terminal alkynes, the synthesis of propargylamines, nitroaldolization reactions, azide alkyne cycloaddition, N-arylation of nitrogen containing compounds, aza-Michael additions, asymmetric Friedel–Crafts reactions, asymmetric Mukaiyama aldol reactions, and asymmetric 1,3-dipolar cycloaddition of azomethine ylides. The type of polystyrene matrix used for the immobilization of complexes is discussed in this paper, and particularly, the efficiency of the catalysts from the point of view of the overall reaction yield, and possible enantioselectivity and potential reusing, is reviewed. Full article
(This article belongs to the Section Organic Chemistry)
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