Allylation Of Carbonyl Compounds Research Articles

Synthesis of Aryl‐ and Alkyl‐Containing 3‐Methylene‐5‐hydroxy Esters via a Barbier Allylation Reaction

AbstractThe formation of C−C bonds via the allylation of carbonyl compounds has been widely applied in total syntheses. Amongst the many possible strategies, the Barbier‐type allylation in aqueous media has received only moderate attention over the last decades despite its mild reaction conditions. In this study, we investigated the indium (In0) and zinc (Zn0) mediated Barbier allylation reaction to efficiently synthesize base‐labile 3‐methylene‐5‐hydroxy containing building blocks for natural product total synthesis. As model study we selected the allylation of lipidic undecanal with ethyl 3‐(bromomethyl)but‐3‐enoate in the presence of either Zn0 or In0 and investigated the effects of additives on yields and selectivities. We then applied the optimized reaction conditions to sterically demanding allyl bromides and functionalized aromatic aldehydes yielding eleven new homoallylic alcohols, one of which was further transformed via oxidation and reduction sequences.

Indium‐mediated allylation of carbonyl compounds in deep eutectic solvents

This study describes, for the first time, the in situ generation of indium organometallic reagents in environmentally friendly deep eutectic solvents (DESs). The allylation process of different carbonyl compounds is achieved mediated by indium metal and using cheap allyl chloride derivatives. The unique DES properties allow to perform the reaction at room temperature and under air, obtaining yields ranging from 45% to 99%. It is possible to recycle the reaction medium for at least four consecutive cycles without much decrease of the observed results. Also, a linear correlation between the yield of the reaction and the density of the DESs is observed.

Ion-paired Ligands for Palladium-catalyzed Allylic Alkylation under Base-free Conditions

The effectiveness of a catalytic amount of bromide ions for significantly accelerating the palladium-catalyzed allylation of carbonyl compounds with allylic carbonates is reported. In particular, t...

Mild bottom-up synthesis of indium(0) nanoparticles: characterization and application in the allylation of carbonyl compounds

A mild bottom-up synthesis of indium(0) nanoparticles (4.0 ± 0.5 nm) was developed and efficiently applied in the allylation of carbonyl compounds.

Primary‐Tertiary Diamine/Br⊘nsted Acid Catalyzed α‐Allylation of Carbonyl Compounds with Allylic Alcohols

AbstractA simple and direct α‐allylic alkylation of unmodified aldehydes with allylic alcohols catalyzed by primary amine/Br⊘nsted acid has been developed. The N,N‐dimethylethylenediamine/TfOH was identified as the optimal catalyst to promote this transformation via an enamine process in high yields (up to 88%) and with good diastereoselectivities (up to 9:1).

An efficient route for the allylation of arylaldehydes to give enantiopure homoallylic alcohols

An efficient asymmetric synthesis of homoallylic alcohols is described by the allylation of carbonyl compounds using organocatalysts as chiral directors in the presence of tin metal. The effect of chiral environment is also studied on the allylation reactions. This method allows us to obtain two different enantiomers of homoallylic alcohol in the presence of the corresponding chiral compound. The protocol is applied to various aldehydes to obtain high yields and excellent enantioselectivities for the corresponding homoallylic alcohols.

ChemInform Abstract: Europium Triflate: An Efficient, Cost‐Effective and Recyclable Solid Acid Catalyst for Highly Chemoselective Allylation of Aldehydes.

Eu (III) compounds are highly efficient catalysts for several important C–C bond forming reactions such as Mukaiyama reaction 1,2 , Michael addition 3-5 , Barbiertype reaction 6 , hetero-Diels-Alder cycloaddition 7 , Friedel-Crafts reaction 8 , Claisen rearrangement 9 , multi component synthesis of imidazoles 10 , oxidation of alkanes 11,12 and epoxidation of alkenes 13–15 . Herein is reported novel application of Eu(III) triflate as an efficient catalyst promoting allylation of aldehydes with allyl trialkylstannane under ambient conditions. Allylation of carbonyl compounds using allyltrialkyland allyl triarylstannanes under Lewis acid catalysis is an important reaction 16,17 . Study of this reaction using rare earth metal salts has received high importance in recent years. However, studies on this reaction using Eu (III) as a catalyst remained dormant in literature. As a part of the continued research interest in development of new synthetic methods using lanthanides as catalysts 18 , the scope of activation of the addition reaction of allylstannane to carbonyls under Eu triflate catalysis has been studied and these results are the subject of this paper (Scheme I).

ChemInform Abstract: Formation of C—C Bonds via Iridium‐Catalyzed Hydrogenation and Transfer Hydrogenation

AbstractReview: 310 refs.

Mild and efficient barbier allylation reaction mediated by magnesium powder under solvent-free conditions

A novel and highly efficient synthesis of homoallylic alcohols is achieved by the allylation of carbonyl compounds using magnesium powder as mediator under solvent-free conditions. A series of aldehydes and ketones are converted to the corresponding homoallylic alcohols, the yields of the reaction is considerably high (85–98%). The procedure is environment benign, operationally simple and easy to scale up at room temperature.

Formation of C-C Bonds via Iridium-Catalyzed Hydrogenation and Transfer Hydrogenation.

The formation of C-C bonds via catalytic hydrogenation and transfer hydrogenation enables carbonyl and imine addition in the absence of stoichiometric organometallic reagents. In this review, iridium-catalyzed C-C bond-forming hydrogenations and transfer hydrogenations are surveyed. These processes encompass selective, atom-economic methods for the vinylation and allylation of carbonyl compounds and imines. Notably, under transfer hydrogenation conditions, alcohol dehydrogenation drives reductive generation of organoiridium nucleophiles, enabling carbonyl addition from the aldehyde or alcohol oxidation level. In the latter case, hydrogen exchange between alcohols and π-unsaturated reactants generates electrophile-nucleophile pairs en route to products of hydro-hydroxyalkylation, representing a direct method for the functionalization of carbinol C-H bonds.

ChemInform Abstract: Indium-Catalyzed Allylation of Carbonyl Compounds with the Mn/TMSCl System.

Abstract Allylation of aldehydes and ketones with allyl bromide was performed with a catalytic amount of indium powder (from 0.01 to 0.1 equiv.) in THF in the presence of manganese and trimethylsilyl chloride as the reducing and oxophilic agent, respectively.

Allylation of Carbonyl Compounds Mediated by Aluminum/Fluoride Salts in Water

AbstractA novel mediator (Al/KF) has been developed and employed in the Barbier‐type alkylations of various aldehydes and ketones with alkyl halide in water. The carbonyl compounds could be effectively converted into corresponding homoallylic alcohol in good yields only when allyl bromides or substituted allyl bromides were used as halides. Aromatic aldehydes could afford homoallylic alcohols in high yields, unfortunately, the allylation of aromatic aldehyde substituted by nitro‐ or amino‐group could not proceed smoothly, and the allylation yields of ketones and aliphatic carbonyl compounds were lower under the same condition. The diastereoselectivity and regioseletivity of the reaction have also been studied, the predominant products preferred the erythro‐ or anti‐isomer in dominant γ‐adduct by using Al/KF mediated allylation of benzaldehydes with cinnamyl bromide and ethyl 4‐bromo‐2‐butenoate in water.

Synthetic Organometallic Radical Chemistry in Water

Several organic radical transformations in aqueous media using organometallic chemistry are presented. Group XIV-elements, such as Si and Ge, and Sn-centered radicals make use of novel methodologies in water which employ both hydrophilic and lipophilic substrates without the requirements of surfactants. Different radical initiation techniques that account for effective initiation of the radical chain reactions in aqueous media are also described, such as the thermal decomposition of azo compounds, the direct photolysis (in the absence of an organic peroxide or other photolytic radical promoter) of silanes, dioxygen initiation techniques, and radical initiation in the absence of solvent, and in the presence of adventitious oxygen. Hydrometallation of multiple bonds with (Me3Si)3SiH and germane analogs in water are also described with the above mentioned initiating techniques, under solvent-free conditions, and performed in continuous flow microreactors. The use of other metal-centered radicals that promote synthetically useful organic transformations in water, such as Mg, Mn, and Zn, is presented. These transformations encompass simple organohalide reductions, and several types of carbon-carbon bond forming reactions, demonstrating the wide scope of organometallic radical chemistry in water for accomplishing organic transformations. Group XIII- centered radicals are also shown to be excellent mediators for organic radical reactions in water, such as Barbier-type alkylations and allylations of carbonyl compounds.

ChemInform Abstract: Synthesis and Structure of Air‐Stable Lewis Acidic Binuclear Complex of Zirconocene Pentafluorophenylsulfonate and Its Catalytic Application in the Allylation of Carbonyl Compounds with Tetraallyltin.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Sn/I2 Mediated allylation of carbonyl compounds with allyl (crotyl) halide in water

A novel mediator (Sn/I2) has been developed and employed in the allylation and crotylation of various aldehydes and ketones with allyl (crotyl) halide in water. With a catalytic amount of I2 and less than stoichiometric amounts of Sn, allyl (crotyl) bromide reacts with carbonyl compounds to produce the corresponding alcohols in quantitative yield. Even the inert allyl chloride and crotyl chloride can react with aldehydes to give the corresponding alcohols. The diastereoselectivity and regioseletivity of the reaction have also been studied. Sn/I2 mediated allylations of aldehydes with crotyl bromide produced dominant γ-adducts with minor α-isomers while Sn/I2 mediated allylations of aldehydes with crotyl chloride afforded dominant α-adducts with minor γ-isomers.

ChemInform Abstract: Petasis Borono‐Mannich Reaction and Allylation of Carbonyl Compounds via Transient Allyl Boronates Generated by Palladium‐Catalyzed Substitution of Allyl Alcohols. An Efficient One‐Pot Route to Stereodefined α‐Amino Acids and Homoallyl Alcohols.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Petasis Borono-Mannich Reaction and Allylation of Carbonyl Compounds via Transient Allyl Boronates Generated by Palladium-Catalyzed Substitution of Allyl Alcohols. An Efficient One-Pot Route to Stereodefined α-Amino Acids and Homoallyl Alcohols

An efficient one-pot procedure was designed by integration of the pincer-complex-catalyzed borylation of allyl alcohols in the Petasis borono-Mannich reaction and in allylation of aldehydes and ketones. These procedures are suitable for one-pot synthesis of alpha-amino acids and homoallyl alcohols from easily available allyl alcohol, amine, aldehyde, or ketone substrates. In the presented transformations, the active allylating agents are in situ generated allyl boronic acid derivatives. These transient intermediates are proved to be reasonably acid-, base-, alcohol-, water-, and air-stable species, which allows a high level of compatibility with the reaction conditions of the allylation of various aldehyde/ketone and imine electrophiles. The boronate source of the reaction is diboronic acid or in situ hydrolyzed diboronate ester ensuring that the waste product of the reaction is nontoxic boric acid. The regio- and stereoselectivity of the reaction is excellent, as almost all products form as single regio- and stereoisomers. The described procedure is suitable to create quaternary carbon centers in branched allylic products without formation of the corresponding linear allylic isomers. Furthermore, products comprising three stereocenters were formed as single products without formation of other diastereomers. Because of the highly disciplined consecutive processes, up to four-step, four-component transformations could be performed selectively as a one-pot sequence. For example, stereodefined pyroglutamic acid could be prepared from a simple allyl alcohol, a commercially available amine, and glyoxylic acid in a one-step procedure. The presented method also grants an easy access to stereodefined 1,7-dienes that are useful substrates for Grubbs ring-closing metathesis.

Cu-Catalyzed Stereoselective Reaction of Allylic Carbonates with Diboronate

Allylboron derivatives are important synthetic intermediates, for instance, for the ste­reoselective allylation of carbonyl compounds. This is a new and very attractive method for a dia­stereoselective preparation of allylboron pinacolates, starting from readily available chiral allylic carbonates. The reaction conditions are extremely mild, and this process offers an excellent tolerance of functional groups. In the presence of ­Xanthphos as a ligand, the reaction is completely γ-selective. As expected, (Z)- and (E)-allylic carbonates with the same configuration of the chiral center give the opposite enantiomers of the product.

Allylation Reactions in Aqueous Media: Development, Applications and Future Works

The use of allyltin, allylzinc and allylindium in the allylation of carbonyl compounds are facile methods for the syntheses of homoallylic alcohols. These water-stable complexes frequently allow for reaction conditions that are not only mild, but also permit the dispensing of organic solvents as reaction media. These synthesis methodologies are progressively being developed for stereoselective carbon-carbon bond formations for the purpose of assembling complex natural products.

Allylation of Carbonyl Compounds Mediated by Nanometer-Sized Bismuth in Water

It is found that nanometer-sized bismuth mediates the allylation of carbonyl compounds in water to afford the corresponding homoallylic alcohol in high yields. Nanometer-sized bismuth is much more effective than regular bismuth powder in this reaction.