Chemoselective Allylation Research Articles

Borane-catalysed C2-selective indole reductive functionalisation.

Indolines are common motifs within pharamceuticals and natural products. Boron catalysis enables the chemoselective allylation of indoles to give allylic indolines in excellent diastereoselectivity. Mechanistic studies revealed in situ formation of the allylic borane, allylation of the imine tautomer of the indole and B-N/B-H transborylation for catalytic turnover.

Synthesis of Linear Tetraquinanes by [3+2] Cycloaddition, Chemoselective Allylation of 7-Ketonorbornene, and Ring-Rearrangement Metathesis as Key Steps

AbstractA nine-step synthetic sequence to linear tetraquinanes involving [3+2] cycloaddition, chemoselective allylation, and ring-rearrangement metathesis as key steps is reported. A chemoselective allylation of 7-ketonorbornene was realized for the first time by using indium powder and allyl bromide. By this method, norbornene ketones can be selectively allylated in the presence of a cyclopentanone moiety to give good yields of monoallylated Barbier-type products.

Palladium-catalyzed base- and solvent-controlled chemoselective allylation of amino acids with allylic carbonates

The utilization of readily available amino acids, which is not only an oxygen nucleophile but also a nitrogen nucleophile, in palladium-catalyzed allylic substitution is realized under mild conditions. The chemoselectivity and multiple allylation are controlled by adjusting the reaction conditions. This represents the first example of this convenient access to valuable N,O-diallylated amino acids. Under the title conditions, a range of amino acids (α-, β-, γ-) and dipeptides can be readily converted in to the corresponding allylic products with excellent yields (67 examples, up to 99% yield) as well as good functional group tolerance.

Concurrent Formation of N-H Imines and Carbonyl Compounds by Ruthenium-Catalyzed C-C Bond Cleavage of β-Hydroxy Azides.

A commercial cyclopentadienylrutenium dicarbonyl dimer ([CpRu(CO)2]2) efficiently catalyzes the formation of N-H imines and carbonyl compounds simultaneously from β-hydroxy azides via C-C bond cleavage under visible light. Density functional theory calculations for the cleavage reaction support the mechanism involving chelation of alkoxy azide species and liberation of nitrogen as the driving force. The synthetic utility of the reaction was demonstrated by a new amine synthesis promoted by chemoselective allylation of imine and synthesis of isoquinoline.

Stereoselective Syntheses of γ,δ-Bifunctionalized Homoallylic Alcohols and Ethers via Chemoselective Allyl Addition to Aldehydes.

Stereoselective synthesis of γ,δ-bifunctionalized homoallylic alcohols and ethers via chemoselective allylation is reported. Pd-catalyzed 1,2-diboration of allenylsilane provided a novel 1,1,2-trifunctional allylation reagent. Allylboration of aldehydes with the reagent followed by in situ protection gave TES-protected homoallylic alcohols with excellent Z-selectivities. Chemoselective allylsilation with the same reagent delivered γ,δ-bifunctionalized homoallylic ethers with high E-selectivities. The bifunctionalized alkene group in the products underwent various transformations without erosion of the olefin geometry.

ChemInform Abstract: Chemoselective and Fast Decarboxylative Allylation by Photoredox Catalysis under Mild Conditions.

Here we report a visible-light-induced decarboxylative allylation to build C(sp3)–allyl bonds. This allylation reaction works for primary, secondary, tertiary, benzyl, and alpha-heteroatom-substituted alkyl N-acyloxyphthalimides and is compatible with many sensitive functional groups. The reaction is complete in minutes at room temperature and can be run in both organic solvents and neutral aqueous solutions. A series of mechanistic experiments have been implemented and a functional-group-rich oligosaccharide modification is demonstrated with the decarboxylative allylation.

ChemInform Abstract: Facile Chemoselective Carbonyl Allylation of Chalcones with Allyltributylstannane Catalyzed by CuI.

Abstract Chemoselective allylation of carbonyl functionality of chalcones with allyltributylstannane was accomplished in the presence of CuI as catalyst. This reaction works well in DMF at 70 °C with exclusive formation of 1,2-addition product. Interesting feature of this reaction is that no conjugate addition product was produced. Various types of chalcones undergo carbonyl allylation in excellent yield.

Facile chemoselective carbonyl allylation of chalcones with allyltributylstannane catalyzed by CuI

Chemoselective allylation of carbonyl functionality of chalcones with allyltributylstannane was accomplished in the presence of CuI as catalyst. This reaction works well in DMF at 70 °C with exclusive formation of 1,2-addition product. Interesting feature of this reaction is that no conjugate addition product was produced. Various types of chalcones undergo carbonyl allylation in excellent yield.

Efficient and Metal-Free Friedel-Crafts Alkylation of Indoles with Allyl Acetate Mediated by TFE

An efficient, metal-free and chemo-selective Friedel-Crafts allylation of indoles in 2,2,2-trifluoroethanol (TFE) is developed. A possible mechanism has also been discussed to explain the observed competitive pathways in this reaction system.

ChemInform Abstract: Gallium Chloride-Mediated Allylation of Dithioacetals with Allylstannanes.

In the presence of gallium chloride, dithioacetals reacted with allylstannanes to give the corresponding homoallyl sulfides in high yields. The present method could be applied to the chemoselective allylation of bis(dithioacetal) of keto aldehyde, and the dithioacetal arising from keto function reacted with allylstannane exclusively.

ChemInform Abstract: Chemoselective Allylation of Aldimine with Allyltriethylgermane by the Combined Use of BF3×OEt2 and AcOH.

Allyltriethylgermane reacts with aldimines in preference to aldehydes by means of BF3•OEt2 and AcOH to afford homoallylic amines in high yields; three component syntheses of homoallytic amines starting from aldehyde, aniline and allylgermane were successfully achieved.

Total Synthesis of (±)-Cephalosol via Silyl Enol Ether Acylation

An efficient total synthesis of (±)-cephalosol is reported. Key steps are the acylation of a silyl enol ether with monomethyl oxalyl chloride and the subsequent acid-mediated ring closure to the isocoumarin structure. A chemoselective allylation and the conversion of the olefin into a methyl acetate were applied to install the γ-lactone moiety.

Chemoselective Allylation of Ketones in Ionic Liquids Containing Sulfonate Anions

The chemoselective addition of tetraallyltin to dialkyl, alkenyl-alkyl, and alkynyl-alkyl ketones can be performed with high yields in N-methyl-N-butylpyrrolidinium trifuoromethansulfonate (MBP-Tf). Other room temperature ionic liquids (RTILs) can also be successfully employed if some sulfonic acid is added. The reaction is very sensitive to the electronic properties of the substrate. Aryl alkyl ketones bearing electron-withdrawing substituents behave like dialkyl ketones and react promptly; on the contrary, electron-rich aryl alkyl ketones react sluggishly, which allows selective competitive allylation of dialkyl substrates to occur. The ionic liquid solvent can be easily recycled, which meets the green chemistry principles of selectivity and reuse of chemicals. NMR spectroscopic data support the formation of tin-triflate catalysts in situ.

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

Air-stable Lewis acidic micro2-hydroxy bridged binuclear complex of zirconocene pentafluorophenylsulfonate was successfully synthesized and found to show high catalytic efficiency in chemoselective allylation of carbonyl compounds with tetraallyltin in aqueous methanol media.

ChemInform Abstract: Highly Efficient Indium‐Catalyzed Chemoselective Allylation—Etherification and Reductive Etherification of Aromatic Aldehydes with Functional Silanes.

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Highly efficient indium-catalyzed chemoselective allylation–etherification and reductive etherification of aromatic aldehydes with functional silanes

Indium(III) chloride is an effective Lewis acid catalyst for one-pot allylation–etherification and reductive etherification of aromatic aldehydes with functional silanes, allyltriethoxysilane, and triethoxysilane, at room temperature to afford corresponding ethers in excellent yields. Additionally, the InCl 3-catalyzed reactions in the presence of TMSCl offer significant advantages in its ease of working-up for the preparation of unsymmetrical ethers under mild conditions.

Synthesis of S-adenosyl-L-methionine analogs and their use for sequence-specific transalkylation of DNA by methyltransferases

Here we describe a one-step synthetic procedure for the preparation of S-adenosyl-L-methionine (AdoMet) analogs with extended carbon chains replacing the methyl group. These AdoMet analogs function as efficient cofactors for DNA methyltransferases (MTases), and we provide a protocol for sequence-specific transfer of extended side chains from these AdoMet analogs to DNA by DNA MTases. Direct chemoselective allylation or propargylation of S-adenosyl-L-homocysteine (AdoHcy) at sulfur is achieved under the acidic conditions needed to protect other nucleophilic positions in AdoHcy. The unsaturated bonds in beta position to the sulfonium center of the resulting AdoMet analogs are designed to stabilize the transition state formed upon DNA MTase-catalyzed nucleophilic attack at the carbon next to the sulfonium center and lead to efficient transfer of the extended side chains to DNA. Using these protocols, sequence-specific functionalized DNA can be obtained within one to two weeks.

Sulphamic acid: An efficient, cost-effective and recyclable solid acid catalyst for highly chemoselective allylation of aldehydes

Aldehydes undergo smooth nucleophilic addition with allyl- n-tributylstannane in the presence of sulphamic acid (5 mol%, SA) under extremely mild reaction conditions to afford the corresponding homoallylic alcohols in excellent yields with high chemoselectivity. The catalyst can be recovered by simple filtration and can be recycled in subsequent reactions. The method is simple, cost-effective and environmentally benign.

Zn Mediated Chemoselective Allylation of Keto Esters with Allylic Halides in Aqueous Medium

Zn Mediated Chemoselective Allylation of Keto Esters with Allylic Halides in Aqueous Medium

Chemoselective Allylation of Aldehydes Using Cerium(III) Chloride: Simple Synthesis of Homoallylic Alcohols.

AbstractFor Abstract see ChemInform Abstract in Full Text.