Reactions of Ketene Acetals. III. A New Synthesis of α-Pyrones. II

1975 ◽  
Vol 53 (2) ◽  
pp. 195-200 ◽  
Author(s):  
Alain Bélanger ◽  
Paul Brassard
Keyword(s):  
Reaction Conditions ◽  
Unsaturated Aldehydes ◽  
New Synthesis ◽  
Aldehydes And Ketones ◽  
Ketene Acetals ◽  
By Products

The cycloaddition of chloroketene acetals to α, β-unsaturated aldehydes and ketones gives the corresponding 2,2-dialkoxy-3-chloro-3,4-dihydro-1,2-pyrans. Treatment of these compounds with alkoxides in dimethylsulfoxide or dimethylformamide yields α-pyrones directly. Some intermediates and by-products have been identified and the reaction conditions have been studied.

scholarly journals Tandem Triphosgene-Assisted Metal-Free One-pot Preparation of Nitriles and Amides from Aldehydes and Ketones

2021 ◽  
Author(s):  
Jianguo liu ◽  
Xiu-Zhi Wei ◽  
Longlong Ma
Keyword(s):  
Metal Catalysts ◽  
Organic Base ◽  
Reaction Conditions ◽  
One Pot ◽  
Metal Free ◽  
Aldehydes And Ketones ◽  
Ester Linkage ◽  
Hydrolysis Of ◽  
By Products

Here we report a facile and efficient triphosgene-assisted one-pot conversion of aldehydes/ketones into nitriles/amides. The triphosgene, a kind of phosgene alternative, containing both ester linkage and chloromethyl units, easily reacts with oximes for the preparation of nitriles/amides. However, the reaction of oximes with triphosgene can’t fully convert corresponding nitriles/amides due to hydrolysis of oximes to aldehydes or ketones. Our protocol tandem proceeds smoothly without the use of organic base and metal catalysts. Diverse functionalized aromatic, aliphatic, and allylic aldehydes/ketones incorporating biomass-derived platform compounds were successfully converted to nitriles and amides in excellent yields. Compared to step-by-step reaction, this tandem strategy is characterized by multi-step reaction in one pot, mild reaction conditions, and fewer by-products.

New Zinc Catalyst for Hydrosilylation of Carbonyl Compounds

Synthesis ◽  
2019 ◽  
Vol 51 (17) ◽  
pp. 3305-3312 ◽  
Author(s):  
Iryna D. Alshakova ◽  
Georgii I. Nikonov
Keyword(s):  
Carbonyl Compounds ◽  
Zinc Complex ◽  
Allylic Alcohols ◽  
Reaction Conditions ◽  
Unsaturated Aldehydes ◽  
Substoichiometric Amount ◽  
Aldehydes And Ketones ◽  
Catalytic Hydrosilylation ◽  
Catalyst Load

A new zinc complex was synthesized and applied in the catalytic hydrosilylation of carbonyl compounds. Optimization of the reaction conditions showed that the presence a substoichiometric amount of methanol accelerates the process significantly. The reaction can proceed at very low catalyst load (down to 0.1 mol%) under mild reaction conditions. The reaction tolerates the presence of C=C bonds, and thus can be useful for the synthesis of allylic alcohols from α,β-unsaturated aldehydes and ketones.

scholarly journals Theoretical Insight into the Reversal of Chemoselectivity in Diels-Alder Reactions of α,β-Unsaturated Aldehydes and Ketones Catalyzed by Brønsted and Lewis Acids

Organics ◽  
2021 ◽  
Vol 2 (1) ◽  
pp. 38-49
Author(s):  
Lakhdar Benhamed ◽  
Sidi Mohamed Mekelleche ◽  
Wafaa Benchouk
Keyword(s):  
Lewis Acids ◽  
Major Product ◽  
Diels Alder ◽  
Unsaturated Ketone ◽  
Unsaturated Aldehydes ◽  
Aldehydes And Ketones ◽  
Theoretical Insight ◽  
Insight Into ◽  
Good Agreement

Experimentally, a reversal of chemoselectivity has been observed in catalyzed Diels–Alder reactions of α,β-unsaturated aldehydes (e.g., (2E)-but-2-enal) and ketones (e.g., 2-hexen-4-one) with cyclopentadiene. Indeed, using the triflimidic Brønsted acid Tf2NH as catalyst, the reaction gave a Diels–Alder adduct derived from α,β-unsaturated ketone as a major product. On the other hand, the use of tris(pentafluorophenyl)borane B(C6F5)3 bulky Lewis acid as catalyst gave mainly the cycloadduct of α,β-unsaturated aldehyde as a major product. Our aim in the present work is to put in evidence the role of the catalyst in the reversal of the chemoselectivity of the catalyzed Diels–Alder reactions of (2E)-but-2-enal and 2-Hexen-4-one with cyclopentadiene. The calculations were performed at the ωB97XD/6-311G(d,p) level of theory and the solvent effects of dichloromethane were taken into account using the PCM solvation model. The obtained results are in good agreement with experimental outcomes.

scholarly journals Green Synthesis of Copper Nanoparticles Using Cotton

Polymers ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 1906
Author(s):  
Marissa Pérez-Alvarez ◽  
Gregorio Cadenas-Pliego ◽  
Odilia Pérez-Camacho ◽  
Víctor E. Comparán-Padilla ◽  
Christian J. Cabello-Alvarado ◽  
...  
Keyword(s):  
Green Synthesis ◽  
Copper Nanoparticles ◽  
Uv Spectroscopy ◽  
Synthesis Method ◽  
Crystallinity Index ◽  
Reaction Conditions ◽  
New Synthesis ◽  
Water As Solvent ◽  
Characterization Studies ◽  
Xrd Patterns

Copper nanoparticles (CuNP) were obtained by a green synthesis method using cotton textile fibers and water as solvent, avoiding the use of toxic reducing agents. The new synthesis method is environmentally friendly, inexpensive, and can be implemented on a larger scale. This method showed the cellulose capacity as a reducing and stabilizing agent for synthetizing Cellulose–Copper nanoparticles (CCuNP). Nanocomposites based on CCuNP were characterized by XRD, TGA, FTIR and DSC. Functional groups present in the CCuNP were identified by FTIR analysis, and XRD patterns disclosed that nanoparticles correspond to pure metallic Cu°, and their sizes are at a range of 13–35 nm. Results demonstrated that CuNPs produced by the new method were homogeneously distributed on the entire surface of the textile fiber, obtaining CCuNP nanocomposites with different copper wt%. Thus, CuNPs obtained by this method are very stable to oxidation and can be stored for months. Characterization studies disclose that the cellulose crystallinity index (CI) is modified in relation to the reaction conditions, and its chemical structure is destroyed when nanocomposites with high copper contents are synthesized. The formation of CuO nanoparticles was confirmed as a by-product, through UV spectroscopy, in the absorbance range of 300–350 nm.

Bu4N+-Controlled Addition and Olefination with Ethyl 2-(Trimethylsilyl)acetate via Silicon Activation

Synlett ◽  
2017 ◽  
Vol 28 (18) ◽  
pp. 2401-2406 ◽  
Author(s):  
Donal O’Shea ◽  
Manas Das ◽  
Atul Manvar ◽  
Ian Fox ◽  
Dilwyn Roberts
Keyword(s):  
Room Temperature ◽  
Product Formation ◽  
Unsaturated Ester ◽  
Reaction Conditions ◽  
Diverse Range ◽  
Inorganic Cation ◽  
Tetrabutyl Ammonium ◽  
Aldehydes And Ketones ◽  
Subsequent Elimination ◽  
Hydroxy Esters

Catalytic Bu4NOAc as silicon activator of ethyl 2-(trimethylsilyl)acetate, in THF, was utilized for the synthesis of β-hydroxy esters, whereas employing catalytic Bu4NOTMS gave α,β-unsaturated esters. The established reaction conditions were applicable to a diverse range of aromatic, heteroaromatic, aliphatic aldehydes and ketones. Reactions were achieved at room temperature without taking any of the specialized precautions that are in place for other organometallics. A stepwise olefination pathway via silylated β-hydroxy esters with subsequent elimination to form the α,β-unsaturated ester has been demonstrated. The key to selective product formation lies in use of the weaker acetate activator which suppresses subsequent elimination whereas stronger TMSO– activator (and base) facilitates both addition and elimination steps. The use of tetrabutyl ammonium salts for both acetate and trimethylsilyloxide activators provide enhanced silicon activation when compared to their inorganic cation counterparts.

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