Simple Allylic Alcohols Research Articles

Synergistic Organoboron/Palladium Catalysis for Regioselective N-Allylations of Azoles with Allylic Alcohols.

A method for regioselective palladium-catalyzed allylic alkylation of ambident nitrogen heterocycles, employing simple allylic alcohols as electrophile precursors, is described. An organoboron co-catalyst serves both to activate the azole-type nucleophile toward selective N-functionalization and to accelerate the formation of a π-allylpalladium complex from the allylic alcohol. The method can be applied to various heterocycle types, including 1,2,3- and 1,2,4-triazoles, tetrazoles, pyrazoles, and purines, and can be extended to substituted allylic alcohol partners.

Synthesis of 1,4-diketones via palladium/photo-cocatalyzed dehydrogenative cross-coupling

Herein we report a palladium/TBADT-cocatalyzed dehydrogenative cross-coupling reaction, enabling the synthesis of a variety of 1,4-diketones starting from simple allylic alcohols and aldehydes as the precursors under mild reaction conditions.

Enantioselective Catalytic Aldehyde α-Alkylation/Semipinacol Rearrangement: Construction of α-Quaternary-δ-Carbonyl Cycloketones and Total Synthesis of (+)-Cerapicol.

An enantioselective aldehyde α-alkylation/semipinacol rearrangement was achieved through organo-SOMO catalysis. The catalytically generated enamine radical cation serves as a carbon radical electrophile that can stereoselectively add to the alkene of an allylic alcohol and initiate ensuing ring-expansion of cyclopropanol or cyclobutanol. This tandem reaction enables the production of a wide range of nonracemic functionalizable α-quaternary-δ-carbonyl cycloketones in high yields and excellent enantioselectivity from simple aldehydes and allylic alcohols. As a key step, the intramolecular reaction was also successfully applied in the asymmetric total synthesis of (+)-cerapicol.

Enantioselective Catalytic Aldehyde α‐Alkylation/Semipinacol Rearrangement: Construction of α‐Quaternary‐δ‐Carbonyl Cycloketones and Total Synthesis of (+)‐Cerapicol

AbstractAn enantioselective aldehyde α‐alkylation/semipinacol rearrangement was achieved through organo‐SOMO catalysis. The catalytically generated enamine radical cation serves as a carbon radical electrophile that can stereoselectively add to the alkene of an allylic alcohol and initiate ensuing ring‐expansion of cyclopropanol or cyclobutanol. This tandem reaction enables the production of a wide range of nonracemic functionalizable α‐quaternary‐δ‐carbonyl cycloketones in high yields and excellent enantioselectivity from simple aldehydes and allylic alcohols. As a key step, the intramolecular reaction was also successfully applied in the asymmetric total synthesis of (+)‐cerapicol.

π-Coordinating Chiral Primary Amine/Palladium Synergistic Catalysis for Asymmetric Allylic Alkylation.

We report an arene-containing chiral primary amine as a dual aminocatalyst and ligand: the π-coordinating aminocatalyst/palladium synergistic catalysis for asymmetric allylic alkylation of α-branched β-ketocarbonyls. The use of arene-containing chiral primary amine catalyst led to not only enhanced reaction rate but also reversed chiral induction compared with its sterically bulky derivative. Both enantiomers of the allylic adducts bearing acyclic all-carbon quaternary stereocenters could be obtained from the same configured chiral aminocatalysts with high efficiency and excellent regio-, stereo-, and enantioselectivity. Mechanistic studies revealed a distinctive Pd-arene π-coordination mode for effective catalysis. The π-coordinating chiral primary amine catalyst could be successfully applied in the asymmetric allylation reactions of vinylethylene carbonates, vinyl epoxides, or simple allylic alcohols.

Palladium-Catalyzed Cycloaromatization/Alkylation of o-(Alkynyl)styrenes.

A Pd(II)-catalyzed mild and highly regioselective 6-endo cyclization/alkylation reaction of o-(alkynyl)styrenes with simple allylic alcohols has been developed. Under mild reaction conditions, the vinyl palladium species generated in situ after cyclization could insert a C-C double bond of allylic alcohol through a cross-coupling reaction and led to the formation of (alkyl)naphthalenes. This cascade cross-coupling reaction represents a direct and atom economic method for the construction of functionalized naphthalene derivatives in moderate to good yields.

Palladium-Catalyzed Cascade Intramolecular Cyclization and Allylation of Enynoates with Allylic Alcohols.

A Pd(II)-catalyzed mild and highly regioselective 6- endo cyclization/allylation reaction of enynoates with simple allylic alcohols has been developed. Under mild reaction conditions, the vinyl palladium species generated in situ after cyclization could insert C-C double bond of allylic alcohol through cross-coupling reaction and lead to the formation of allyl pyrone via β-OH elimination. This cascade cross-coupling reaction represents a direct and atom economic methodology for the construction of novel allyl pyrones in moderate to good yields.

Nickel-Catalyzed Suzuki Cross Couplings with Unprotected Allylic Alcohols Enabled by Bidentate N-Heterocyclic Carbene (NHC)/Phosphine Ligands

Cross couplings between simple allylic alcohols and aryl and vinyl boronic acids are efficiently catalyzed by nickel(0) catalysts and bidentate N-heterocyclic carbene/phosphine ligands. The bidentate nature of the ligand is shown to extend catalyst lifetime and enable high yields of the corresponding cross coupling products. X-ray crystallography confirms the bidentate nature of the ligand scaffold. Multistep cross coupling-alkene/alkyne insertions reactions are also conducted and the bidentate nature of the substrate makes the pendant phosphine of the ligand unnecessary.

KOtBu‐Mediated Domino Isomerization and Functionalization of Aromatic Allylic Alcohols

Transition‐metal‐ as well as ligand‐free base‐mediated domino isomerization and alkylation of allylic alcohols is presented. This protocol features the conversion of simple allylic alcohols into the corresponding ketones through isomerization in the presence of a simple base. Significantly, these in situ generated ketones subsequently undergo alkylation with styrenes as electrophiles, in a domino one‐pot fashion, as an atom‐ and step‐economical chemical process.

Palladium-Catalyzed Cascade Wacker/Allylation Sequence with Allylic Alcohols Leading to Allylated Dihydropyrones.

We describe a cascade Wacker/allylation sequence of β-hydroxy ynones by directly using simple allylic alcohols. This palladium(II)-catalyzed reaction occurs under mild conditions (0 °C to room temperature) and provides a new and efficient synthetic method for the preparation of allylated dihydropyrones. The regiochemical outcomes are consistent with a reaction pathway that includes an insertion/β-OH elimination sequence to form the allylic moiety. A remarkable changeover from allyl to formylethyl products occurs under the simple action of LiBr.

ChemInform Abstract: Catalytic Enantioselective Dihalogenation and the Selective Synthesis of (‐)‐Deschloromytilipin A and (‐)‐Danicalipin A.

AbstractA titanium‐based catalytic enantioselective dichlorination of simple allylic alcohols is described.

Catalytic Enantioselective Dihalogenation and the Selective Synthesis of (-)-Deschloromytilipin A and (-)-Danicalipin A.

A titanium-based catalytic enantioselective dichlorination of simple allylic alcohols is described. This dichlorination reaction provides stereoselective access to all common dichloroalcohol building blocks used in syntheses of chlorosulfolipid natural products. An enantioselective synthesis of ent-(-)-deschloromytilipin A and a concise, eight-step synthesis of ent-(-)-danicalipin A are executed and employ the dichlorination reaction as the first step. Extension of this system to enantioselective dibromination and its use in the synthesis of pentabromide stereoarrays relevant to bromosulfolipids is reported. The described dichlorination and dibromination reactions are capable of exerting diastereocontrol in complex settings allowing X-ray crystal structure analysis of natural and unnatural diastereomers of polyhalogenated stereohexads.

Allylic borylation of tertiary allylic alcohols: a divergent and straightforward access to allylic boronates

A novel method for the preparation of diverse allylic boronates from simple allylic alcohols is reported.

ChemInform Abstract: Direct Use of Allylic Alcohols for Palladium‐Catalyzed Synthesis of 3‐Allylbenzo[b]thiophenes, Benzofurans and Indoles in Aqueous Media.

Allylative cyclization of (o-alkynylphenyl) (methoxymethyl) sulfides, o-alkynylanilines and o-alkynylphenols catalyzed by π-allyl palladium species generated from simple allylic alcohols is described. 3-Allylbenzo[b]thiophenes, 3-allylindoles and 3-allylbenzofurans were obtained in good yields using aqueous media under neutral conditions.

ChemInform Abstract: Highly Efficient Direct Allylation of Oxindoles with Simple Allylic Alcohols Enabled by Palladium/Broensted Acid Catalysis.

AbstractPreliminary experiments towards an asymmetric allylation of (Ia) with (II) using chiral mono or diphosphine ligands furnish (IIIa) with up to 17% enantiomeric excess only.

ChemInform Abstract: Palladium Catalyzed Direct Allylation of Azlactones with Simple Allylic Alcohols in the Absence of Any Activators.

AbstractThe first efficient example of the direct allylic alkylation of azlactones with simple allylic alcohols using only Pd(PPh3)4 as catalyst under neutral conditions by substrate self‐assisted activation strategy is reported.

Catalytic, stereospecific syn-dichlorination of alkenes.

As some of the oldest organic chemical reactions known, the ionic additions of elemental halogens such as bromine and chlorine to alkenes are prototypical examples of stereospecific reactions, typically delivering vicinal dihalides resulting from anti-addition. Although the invention of enantioselective variants is an ongoing challenge, the ability to overturn the intrinsic anti-diastereospecificity of these transformations is also a largely unsolved problem. Here, we describe the first catalytic, syn-stereospecific dichlorination of alkenes, employing a group transfer catalyst based on a redox-active main group element (selenium). With diphenyl diselenide (PhSeSePh) (5 mol%) as the pre-catalyst, benzyltriethylammonium chloride (BnEt3NCl) as the chloride source and an N-fluoropyridinium salt as the oxidant, a wide variety of functionalized cyclic and acyclic 1,2-disubstituted alkenes, including simple allylic alcohols, deliver syn-dichlorides with exquisite stereocontrol. This methodology is expected to find applications in streamlining the synthesis of polychlorinated natural products such as the chlorosulfolipids.

Direct use of allylic alcohols for palladium-catalyzed synthesis of 3-allylbenzo[b]thiophenes, benzofurans and indoles in aqueous media

Palladium-catalyzed allylative cyclization of 1, 2 and 3 using simple allylic alcohols in aqueous media afforded 3-allylbenzo[b]thiophenes 4, 3-allylindoles 5 and 3-allylbenzofurans 6 in good yields.

Brønsted acid accelerated Pd-catalyzed direct asymmetric allylic alkylation of azlactones with simple allylic alcohols: a practical access to quaternary allylic amino acid derivatives.

A Brønsted acid accelerated Pd-catalyzed asymmetric allylic alkylation of azlactones with simple allylic alcohols under mild reaction conditions has been realized, which provides a direct and readily scalable approach for the synthesis of all-carbon quaternary allylic amino acid derivatives in excellent yields and good enantioselectivities.

Highly Efficient Direct Allylation of Oxindoles with Simple Allylic Alcohols Enabled by Palladium/Brønsted Acid Catalysis

A highly efficient and practical direct allylic alkylation of oxindoles with simple allylic alcohols cocatalyzed by Pd(OAc)₂/Ph₃P and PhCO₂H under mild conditions has been developed, which streamlines the installation of an all-carbon quaternary allylic center at the oxindole 3-position. Enantioselective allylic alkylation has also been realized with the product in almost quantitative yield and 17% enantiomeric excess. Mechanistically, ESI analysis indicates that a palladium(0) species and π-allyl-Pd(PPh₃)₂ cation were involved.