Selenium Dioxide-Mediated Bromination of α,ß-Unsaturated Ketones Using N-Bromosuccinimide in the Presence of p-Toluenesulfonic Acid: A Versatile Route for the Synthesis of α'-Bromo-4-arylbut-3-en-2-one and α',α'-Dibromo-4-arylbut-3-en-2-one.

An efficient method for the synthesis of α,ß-unsaturated α'-bromoketones and α,ß-unsaturated α',α'-dibromoketones is described using N-bromosuccinimide (NBS) as the brominating agent mediated by selenium dioxide (SeO2) in the presence of p-toluenesulfonic acid (PTSA) monohydrate in toluene. The method is simple, employing easily available shelf reagents to afford a wide range of products in good yields. The method highlighted that simple fine-tuning of the reaction conditions and molar equivalents of the reactants easily affords either mono- or dibrominated products in excellent yields. A number of these products have not been reported in the literature. All of the reactions were carried out in gram-scale quantities.

Trifluoroacetic Acid-Mediated Oxidative Self-Condensation of Acetophenones in the Presence of SeO2: A Serendipitous Approach for the Synthesis of Fused [1,3]Dioxolo[4,5-d][1,3]dioxoles.

A method for the synthesis of fused 1,3-dioxolanes was developed by self-condensation of glyoxal generated in situ by oxidation of acetophenones with SeO2 in the presence of trifluoroacetic acid. Three molecules of the glyoxal generated by oxidation of ketone with SeO2 condensed to form architecturally novel oxygen-containing heterocycles (3a-aryldihydro-[1,3]dioxolo[4,5-d][1,3] dioxole-2,5-diyl)bis(phenylmethanones). This reaction provides a unique methodology for the construction of four C-O bonds in a concerted fashion, generating highly embedded oxygen heterocycles from readily available ketones using affordable shelf reagents and simple reaction conditions.

Selenocyanation of Aryl and Styryl Methyl Ketones in the Presence of Selenium Dioxide and Malononitrile: An Approach for the Synthesis of α-Carbonyl Selenocyanates.

A convenient method has been developed for the synthesis of α-carbonyl selenocyanates from aryl methyl ketones/styryl methyl ketones using selenium dioxide as the selenating agent under simple reaction conditions. This reaction has notable advantages over the traditional methods in terms of accessibility and affordability of the starting materials. The method features the interaction of aryl methyl ketones/styryl methyl ketones with selenium dioxide and malononitrile to afford a series of α-carbonyl selenocyanates in moderate to good yields.

Metal-Free Three-Component Coupling Reaction of Ketones with Electron-rich Arenes and Selenium Dioxide for the Synthesis of α-Arylselanyl Ketones.

A metal-free three-component coupling reaction of aryl alkyl/alkyl ketones, SeO2, and phenols/anisoles is described. This multicomponent reaction provides a straightforward and facile pathway for the synthesis of α-((4-hydroxy/methoxyphenyl)selanyl)-aryl alkyl/alkyl ketones in the presence of p-toluenesulfonic acid for the C-Se bond formation process. The method offers an attractive and simple procedure using commonly available shelf reagents to deliver organoselenides that, to our knowledge, are being reported here for the first time.

PTSA-Catalyzed Reaction of Alkyl/Aryl Methyl Ketones with Aliphatic Alcohols in the Presence of Selenium Dioxide: A Protocol for the Generation of an α-Ketoacetals Library.

A novel approach has been developed for the synthesis of a wide range of α-ketoacetals by the reaction of alkyl/aryl methyl ketones and aliphatic alcohols in the presence of selenium dioxide catalyzed by p-toluenesufonic acid. This method represents a general route to obtain a wide variety of α-ketoacetals in a simple, rapid, and practical manner. This approach is particularly attractive because of the easy availability of the starting materials, mild reaction temperature, and good yields of the products. The resulting α-ketoacetals are of much synthetic value as organic intermediates.

Selenium Dioxide As an Alternative Reagent for the Direct α-Selenoamidation of Aryl Methyl Ketones.

A general strategy for the preparation of N, N-dialkyl-2-oxo-2-arylethaneselenoamides is described. The single step method involves direct coupling of aryl methyl ketones with secondary amines and selenium dioxide in DMSO. The reactions proceeded smoothly at room temperature to provide a number of the α-oxo-selenoamides in good to excellent yields.