Photo-Catalyzed Acyl Azolium Promoted Selective α-C(sp3 )-H Acylation of Acetone via HAT: Access to Thermodynamically Less Favoured (Z)-α,ß-Unsaturated Ketones.

Mono α-acylation of acetone has been achieved for the first time by reacting with bench-stable acyl azolium salts under violet-LED light at room temperature. The intermolecular hydrogen atom transfer (HAT) from acetone to triplet state of azolium salts under violet LED irradiation resulted in thermodynamically less favourable (Z)-α,ß-unsaturated ketones with up to 99 : 1 selectivity via C-C bond formation. This compelling protocol access the desired α-C(sp3 )-H acylation product under metal-, ligand- and oxidant-free conditions on a wide range of substrates.

Facile Cleavage of Activated Ketones: An Access to Thioethers via In Situ Generation of Anhydrides by Pummerer-Type Rearrangement.

Herein, we report an oxygen insertion in activated ketones from simple inorganic carbonates for the synthesis of symmetric aromatic anhydrides. For the first time, Li2CO3 acts as an oxygen source and the in situ generated symmetric aromatic anhydrides undergo Pummerer-type rearrangement to access α-benzoyloxy-thioethers. Attractively, this protocol occurs under metal-, ligand-, and oxidant-free conditions and is compatible with a wide range of substrates. Control experiments reveal the reaction pathway.

Transition-metal-catalyzed C-H bond activation/functionalization and annulation of phthalazinones.

Phthalazinones and their higher congeners are commonly prevalent structural motifs that occur in natural products, bioactive molecules, and pharmaceuticals. In the past few decades, transition-metal-catalyzed reactions have received an overwhelming response from organic chemists as challenging organics and heterocycles could be built with ease. Currently, the synthesis of phthalazinones largely depends on transition-metal catalysis, especially by palladium-catalyzed carbonylation. Further, the dominance of transition-metal catalysts was realized from the phthalazinones viewpoint, as nitrogen and oxygen atoms endowed upon them act as directing groups to facilitate diverse C-H activation/functionalization/annulation reactions. This highlight describes the various synthetic methods used to access phthalazinones and functionalize them by reacting with various coupling partners via chelation assistance strategy involving C(sp2)-H/N-H bond activation in the presence of transition-metal (Rh, Ru, Pd, and Ir) catalysts. The mechanisms of sulfonylation, halogenation, acylmethylation, alkylation, and annulation reactions are discussed.

Solvent-controlled amidation of acid chlorides at room temperature: new route to access aromatic primary amides and imides amenable for late-stage functionalization.

Herein, we report a solvent-controlled highly selective amidation and imidation of aroyl chlorides using an alkali-metal silyl-amide reagent (LiHMDS), which serves as a nitrogen source at room temperature. A unique feature of this method lies in the sequential silyl amidation of aryol chlorides and nitrogen-silicon bond cleavage of the corresponding N,N-bis(trimethylsilyl)benzamide in a one-pot method in a very short reaction time. This effective strategy was extended to late-stage functionalization.

Stereoselective Addition of Alkynes to Ketenimines: Copper/Amine Catalyzed Sulfonyl Azide-Alkyne Cycloaddition Reactions for the Synthesis of (Z)-1,3-Enynes.

Herein, we report a copper/amine catalyzed stereoselective addition of alkynes to ketenimine intermediates generated in situ from the sulfonyl azide-alkyne cycloaddition cascade for the stereoselective synthesis of (Z)-1,3-enynes. Significantly, for the first-time, enamine intermediates generated in the copper-catalyzed sulfonyl azide-alkyne cycloaddition reactions have been successfully trapped and isolated as the products. Density functional theory computations have also been performed and found to be consistent with the observed experimental stereoselectivity.

Alternative and Uncommon Acylating Agents - An Alive and Kicking Methodology.

Functionalizing and derivatising organic molecules is a centerpiece in organic synthesis. Succinctly manipulating and installing acyl moieties in organic molecules spurred the interest of chemists owing to its occurrence in natural products, bioactive molecules, pharmaceuticals, and advanced materials. Traditionally, access to acylation reaction was achieved by Friedel-Crafts reaction, Schotten-Baumann, and Vilsmeier-Haack acylation, however, these protocols own pitfalls. Further to make the acylation process attractive and environmentally friendly, toluene, aldehydes, alcohols, α-keto acids, amines, amides, esters, ethers, nitriles, alkynes, alkenes, ketenes, N-acylbenzotriazoles, ketones, thioacids, oximes, thiazolium carbinols, PIDA, diacyl disulfides and acyl salts were used as an acyl surrogates/reagents. Amusingly, these acylating reagents are considered uncommon and alternative to carboxylic acids, acid chlorides and acetic anhydrides. This short review aims to encompass the usage of acylating agents in transition-metal, metal-free, light-driven and other demanding conditions, and thus reveals their practicality.

Synthesis and antioxidant activity of a novel class of 4,6-O-protected O-glycosides and their utility in disaccharide synthesis.

BF(3).Et(2)O-catalysed O-glycosylation of 1,2,3-tri-O-acetyl-4,6-O-butylidene- and ethylidene-beta-d-glucopyranose with different aliphatic and aromatic alcohols proceeds for the most part with complete retention of anomeric configuration. Antioxidant activity of O-glycosides shows significant inhibition (IC(50) approximately 77%). 1,3-Dipolar cycloaddition of terminal alkyne derivatives of O-glycosides with glycosyl azide results in disaccharides.