Hydroacylation Of Alkenes Research Articles

Radical Hydroalkylation and Hydroacylation of Alkenes by the Use of Benzothiazoline under Thermal Conditions.

The hydroalkylation and hydroacylation of electron-deficient alkenes proceeded smoothly by using benzothiazoline derivatives as radical-transfer reagents under thermal conditions without light irradiation or any additive. Both benzyl and benzoyl moieties were transferred efficiently.

Photocatalytic Hydroacylation of Alkenes by Directly Using Acyl Oximes

Acyl oximes are directly used as the acyl radical precursors in the hydroacylation reactions for the first time. In this work, acyl radicals can be effectively generated via β-scission of a phosphoranyl radical under photocatalytic conditions. As a result, the hydroacylation of alkenes triggered by the resulting acyl radicals leads to facile syntheses of a range of valuable ketones.

Visible-Light-Promoted Photocatalyst-Free Hydroacylation and Diacylation of Alkenes Tuned by NiCl2·DME.

Herein, we describe a visible light-promoted hydroacylation strategy that facilitates the preparation of ketones from alkenes and 4-acyl-1,4-dihydropyridines via an acyl radical addition and hydrogen atom transfer pathway under photocatalyst-free conditions. The efficiency was highlighted by wide substrate scope, good to high yields, successful scale-up experiments, and expedient preparation of highly functionalized ketone derivatives. In addition, this protocol allows for the synthesis of 1,4-dicarbonyl compounds through alkene diacylation in the presence of NiCl2·DME.

Green Metal‐Free Photochemical Hydroacylation of Unactivated Olefins

AbstractDirect alkylation of C(sp2)−H bonds to convert an aldehyde into a ketone is a notorious transformation, due to the laborious challenge of the formation of ketyl or acyl radicals. Herein, we report a green, cheap, metal‐free and efficient method for the hydroacylation of olefins in water. This photochemical protocol utilizes phenylglyoxylic acid, a commercially available small organic molecule, as the photoinitiator, water as the solvent and household fluorescent lamps as the irradiation source, leading to a broad substrate scope of products in moderate to good yields. A wide range of aromatic and aliphatic aldehydes, terminal and non‐terminal alkenes and pharmaceutically relevant molecules can be employed, without the need of directing groups and additives or metal catalysts.

Green Metal‐Free Photochemical Hydroacylation of Unactivated Olefins

Direct alkylation of C(sp2 )-H bonds to convert an aldehyde into a ketone is a notorious transformation, due to the laborious challenge of the formation of ketyl or acyl radicals. Herein, we report a green, cheap, metal-free and efficient method for the hydroacylation of olefins in water. This photochemical protocol utilizes phenylglyoxylic acid, a commercially available small organic molecule, as the photoinitiator, water as the solvent and household fluorescent lamps as the irradiation source, leading to a broad substrate scope of products in moderate to good yields. A wide range of aromatic and aliphatic aldehydes, terminal and non-terminal alkenes and pharmaceutically relevant molecules can be employed, without the need of directing groups and additives or metal catalysts.

Ketone Synthesis by Direct, Orthogonal Chemoselective Hydroacylation of Alkenes with Amides: Use of Alkenes as Surrogates of Alkyl Carbanions

Summary of main observation and conclusionDirect functionalization of alkenes and direct transformation of carboxamides are two exciting areas that have attracted considerable attention in recent years. We report herein that secondary amides, the least reactive derivatives of carbonyl compounds, upon activated with triflic anhydride, can serve as effective hydroacylating reagents in partner with alkenes to yield ketones at ambient temperature. The method was applied to the one‐step synthesis of racemic dihydro‐ar‐turmerone. In this method, alkenes serve as surrogates of organometallic reagents, which allows the orthogonal chemoselective reactions. The ready availability of many olefins such as camphene and norbornene permits one‐step ketone synthesis that would require several steps by conventional methods.

A redox-neutral synthesis of ketones by coupling of alkenes and amides

The direct synthesis of ketones via carbon–carbon bond formation represents one of the most important challenges in organic synthesis. Hydroacylation of alkenes offers perhaps the most efficient and atom-economical approach for the preparation of ketones employing carbonyl compounds and alkenes as feedstocks. State-of-the-art hydroacylation is typically achieved by a transition metal-catalysed coupling of an aldehyde and an alkene but is plagued by competing decarbonylation, requiring the installation of directing groups in the aldehyde reactant. Herein, we present a method for the hydroacylation of alkenes employing amides in a metal-free regime, proceeding by a new mechanism and offering orthogonal reactivity to the conventional, metal-catalysed alternatives.

Dynamic Kinetic Resolution of Aldehydes by Hydroacylation.

We report a dynamic kinetic resolution (DKR) of chiral 4-pentenals by olefin hydroacylation. A primary amine racemizes the aldehyde substrate via enamine formation and hydrolysis. Then, a cationic rhodium catalyst promotes hydroacylation to generate α,γ-disubstituted cyclopentanones with high enantio- and diastereoselectivities.

Photocatalytic hydroacylation of trifluoromethyl alkenes.

Hydrofunctionalization of trifluoromethyl alkenes is highly challenging, because the nucleophilic addition is oftentimes followed by β-F elimination in this case. By the use of tetrabutylammonium decatungstate (TBADT) as a hydrogen-atom-transfer (HAT) photocatalyst for acyl C-H activation, we successfully avoid the β-F elimination in the hydroacylation of trifluoromethyl alkenes with aldehydes. This light (390 nm) promoted reaction provides a facile and efficient access to various β-CF3 ketones in complete regiocontrol with high functionality tolerance and 100% atom economy.

Benzothiazolines as radical transfer reagents: hydroalkylation and hydroacylation of alkenes by radical generation under photoirradiation conditions.

Novel radical transfer reagents under photoirradiation conditions were developed by the use of benzothiazoline derivatives. These reagents enabled both hydroalkylation and hydroacylation of alkenes under neutral conditions at ambient temperature without any toxic reagents or an excess amount of metals. A mechanistic study was carried out to elucidate the radical process.

Visible-Light-Driven Epoxyacylation and Hydroacylation of Olefins Using Methylene Blue/Persulfate System in Water.

A visible-light-driven strategy for hydroacylation and epoxyacylation of olefins in water using methylene blue as photoredox catalyst and persulfate as oxidant is reported. In this unprecedented unified approach, two different transformations are accomplished using only one set of reagents. The method has a broad scope spanning a range of aromatic and aliphatic aldehydes as well as conjugated and nonconjugated olefins to deliver ketones and epoxyketones from abundant and inexpensive chemical feedstocks.

Recent Advances in Intermolecular Hydroacylation of Alkenes with Aldehydes through Rhodium Catalysis

The rhodium-catalyzed intermolecular hydroacylation of alkenes with aldehydes is an atom-economical method for the synthesis of ketones. Here, we give a brief review on its development and we highlight recent advances in chelating strategies for the stabilization of acyl rhodium species by coordinative saturation.

Green Photo-Organocatalytic C-H Activation of Aldehydes: Selective Hydroacylation of Electron-Deficient Alkenes.

Selective C-H activation is an area of growing importance. Metal-free C-H activation of branched aldehydes mediating the hydroacylation of electron-deficient alkenes is an attractive transformation, but is limited by selectivity issues, especially in the case of α,α-disubstituted aldehydes. Herein, we report a green, cheap, versatile, and easily reproducible selective hydroacylation of alkenes utilizing phenylglyoxylic acid as the photocatalyst and common household bulbs for irradiation, leading to products in excellent yields and selectivities. The reaction mechanism was also studied to account for the high selectivity.

Total Synthesis of Propolisbenzofuran B.

An efficient synthesis of propolisbenzofuran B, which possesses promising anticancer activity, is reported. The key cyclohexanone framework of this tricyclic natural product has been constructed employing a Rh-catalyzed intramolecular olefin hydroacylation. The requisite key olefin intermediate was synthesized by using gold-catalyzed allenyl ether [1,3] O → C rearrangement.

Catalytic, Enantioselective Synthesis of Polycyclic Nitrogen, Oxygen, and Sulfur Heterocycles via Rh-Catalyzed Alkene Hydroacylation.

Enantioselective synthesis of polycyclic nitrogen, oxygen, and sulfur heterocycles by rhodium-catalyzed intramolecular alkene hydroacylation is reported. The intramolecular hydroacylation reactions generate 1,4-dihydrocyclopenta[b]indol-3(2H)-ones and 3,4-dihydrocyclopenta[b]indol-1(2H)-one in moderate-to-high yields (65-99%) with good-to-excellent enantioselectivities (84-99% ee). The catalyst system also promotes alkene hydroacylation of 3-vinylfuran-, 3-vinylbenzothiophene-, and 3-vinylthiophene-2-carboxaldehydes to generate the corresponding ketone products in moderate-to-high yields (71-91% yield) with excellent enantioselectivities (97-99% ee).

Photoredox-Catalyzed Hydroacylation of Olefins Employing Carboxylic Acids and Hydrosilanes.

A hydroacylation reaction of alkenes has been achieved employing readily available carboxylic acids as the acyl source and hydrosilanes as a hydrogen source via photoredox catalysis. The combination of both single electron transfer and hydrogen atom transfer steps has dramatically expanded new applications of carboxylic acids in organic synthesis. The protocol also features extremely mild conditions, broad substrate scope, and good functional group tolerance, affording a novel and convenient approach to hydroacylation of alkenes.

Cobalt‐Catalyzed Enantio‐ and Diastereoselective Intramolecular Hydroacylation of Trisubstituted Alkenes

AbstractEnantio‐ and diastereoselective synthesis of trans‐2,3‐disubstituted indanones is achieved by intramolecular hydroacylation of 2‐alkenylbenzaldehydes bearing trisubstituted alkenyl groups under cobalt‐chiral diphosphine catalysis. Notably, a high level of enantioselectivity is induced regardless of the stereochemistry (E/Z ratio) of the alkenyl group of the starting material. Deuterium‐labeling experiments shed light on the productive reaction pathways of the E‐ and Z‐isomers.

Cobalt-Catalyzed Enantio- and Diastereoselective Intramolecular Hydroacylation of Trisubstituted Alkenes.

Enantio- and diastereoselective synthesis of trans-2,3-disubstituted indanones is achieved by intramolecular hydroacylation of 2-alkenylbenzaldehydes bearing trisubstituted alkenyl groups under cobalt-chiral diphosphine catalysis. Notably, a high level of enantioselectivity is induced regardless of the stereochemistry (E/Z ratio) of the alkenyl group of the starting material. Deuterium-labeling experiments shed light on the productive reaction pathways of the E- and Z-isomers.

Rhodium-Catalyzed Asymmetric Hydroacylation of Trisubstituted Alkenes

Rhodium-Catalyzed Asymmetric Hydroacylation of Trisubstituted Alkenes

Lewis Acid-assisted Dirhodium(II)-catalyzed Ketone Hydroacylation

The combination of a Rh(II) salt and a Lewis acid, Sc(OTf)3, as a highly active and robust cooperative catalyst system for ketone hydroacylation was developed. The catalyst system showed high turnover numbers (up to ca. 400) even under air, whereas the corresponding Rh(I)/Sc(OTf)3 system did not work well. The application of the Rh(II)/Sc system was also extended to hydroacylation of olefins and an enantioselective reaction.