Alkynyl Esters Research Articles

Stereoselective Retentive Domino Transmetalations of Secondary Alkyllithium Compounds to Functionalized Secondary Alkylcopper Reagents.

Functionalized secondary alkyllithium reagents obtained by I/Li exchange from the corresponding secondary alkyl iodides undergo two successive transmetalations with Me3 SiCH2 ZnBr⋅LiBr and CuBr⋅2 LiCl⋅Me2 S to provide functionalized secondary alkylcopper compounds with high retention of configuration. These alkylcopper derivatives react further with electrophiles such as alkynyl esters, acid chlorides, allylic chlorides, ketals, ethylene oxide, and 3-iodocyclopentanone with high retention of configuration. A related sequence of transmetalations with MeMgI and LaCl3 ⋅2 LiCl allows a retentive addition of secondary alkyllithium reagents to acetone. The influence of the solvent on the configurational stability of secondary alkylzinc reagents is described.

ChemInform Abstract: Iridium‐Catalyzed [2 + 2 + 2] Cycloaddition of α,ω‐Diynes with Alkynyl Ketones and Alkynyl Esters.

Abstract We found that the combination of [Ir(cod)Cl] 2 and rac -BINAP served as an efficient catalyst for the [2+2+2] cycloaddition of 2,7-nonadiyne derivatives and related compounds with alkynyl ketones and alkynyl esters. The corresponding products were obtained in high yields under mild reaction conditions.

ChemInform Abstract: Gold(I)‐Catalyzed Synthesis of Optically Active 1,4‐Oxazepan‐7‐ones.

AbstractA novel one‐step synthesis of enantioenriched 1,4‐oxazepan‐7‐ones is achieved by cyclization of optically active alkynyl esters in the presence of Ph3PAuCl and Cu(OTf)2 as the catalysts.

Synthesis of alkynes from vinyl triflates using tetrabutylammonium fluoride.

A convenient method for the preparation of alkynes and alkynyl esters from ketones and β-keto esters is described which involves the formation of vinyl triflates, followed by elimination with tetrabutylammonium fluoride trihydrate, to give alkynes. Unlike established elimination methods, the method requires neither a strong base nor anhydrous conditions.

Iridium-catalyzed [2+2+2] cycloaddition of α,ω-diynes with alkynyl ketones and alkynyl esters

We found that the combination of [Ir(cod)Cl]2 and rac-BINAP served as an efficient catalyst for the [2+2+2] cycloaddition of 2,7-nonadiyne derivatives and related compounds with alkynyl ketones and alkynyl esters. The corresponding products were obtained in high yields under mild reaction conditions.

Oxidative Annulation of Anilides with Internal Alkynes Using an (Electron‐Deficient η5‐Cyclopentadienyl)Rhodium(III) Catalyst Under Ambient Conditions

AbstractA dinuclear (electron‐deficient η5‐cyclopentadienyl)rhodium(III) complex was synthesized on a preparative scale via the rhodium‐catalyzed cross [2+2+1] cyclotrimerization of silylacetylenes and two alkynyl esters, leading to substituted silylfulvenes, followed by reductive complexation with rhodium(III) chloride in ethanol. The thus obtained dinuclear (electron‐deficient η5‐cyclopentadienyl)rhodium(III) complex is a highly active precatalyst for the oxidative annulation of anilides with internal alkynes under ambient conditions (at room temperature under air). A preference for annulation across electron‐rich substrates over electron‐deficient substrates was observed using this electron‐deficient rhodium(III) complex.magnified image

Gold-catalyzed reaction of oxabicyclic alkenes with electron-deficient terminal alkynes to produce acrylate derivatives

Oxabicyclic alkenes can react with electron-deficient terminal alkynes in the presence of a gold catalyst under mild conditions, affording the corresponding addition products in moderate yields. When using alkynyl esters as substrates, the (Z)-acrylate derivatives are obtained. Using but-3-yn-2-one (ethynyl ketone) as a substrate, the corresponding addition product is obtained with (E)-configuration. The proposed mechanism of these reactions is also discussed.

Phosphazene-catalyzed intramolecular cyclization of nitrogen-tethered alkynyl esters

Intramolecular cyclization of nitrogen-tethered alkynyl esters catalyzed by phosphazene organosuperbases P2-tBu and P4-tBu was investigated. Both acyclic and cyclic substrates underwent 5-exo-dig and 5-endo-dig cyclization. This reaction is a rare example of the intramolecular addition of enolates of simple esters to alkynes.

A Facile One-Pot Stereoselective Synthesis of (Z)-α-Acyl-α,α-Unsaturated Esters from Alkynyl Esters and Aryl Acyl Chlorides

( Z)-α-Acyl-α,β-unsaturated esters can be stereoselectively synthesised in one pot under mild conditions and in good yields by the palladium-catalysed hydrostannylation of alkynyl esters in benzene, followed by the Stille cross-coupling with aryl acyl chlorides using CuI as co-catalyst.

Conformational behavior of symmetrical and unsymmetrical mono(alkynylpeptide)-tungsten complexes

A series of N-protected amino acid alkynylesters were prepared by reaction of the amino acid carboxylate group with either propargyl alcohol (to yield the asymmetric esters 2a–c) or with 1, 4-but-2-yne diol (to yield the symmetric esters 3a–d). The alkynylesters were reacted with W(CO)3(dmtc)2 to yield monoalkyne complexes having the general formula W(CO)(dmtc)2(alkynyl ester). The monoalkyne complexes 6a–f were unstable in the presence of oxygen and had to be kept under an inert atmosphere. Analysis of the NMR spectra of the monoalkyne complexes showed that two diastereomers were formed in the synthesis, and that there was rapid rotation of the alkyne about the tungsten center at 23 °C and above with both diastereomers. At lower temperatures alkyne rotation is significantly slowed. Symmetric alkynylesters of a dipeptide (4) and tripeptide (5) were also prepared and reacted with W(CO)3(dmtc)2 to yield monoalkyne complexes. The resulting complexes (6g and 6h) also formed two diastereomers and displayed rapid rotation of the alkyne about the tungsten center at 23 °C and above, and slow rotation at lower temperatures. The amide NH protons in 6g and 6h were probed by DMSO titration to see if they were involved in intramolecular hydrogen bonds; they were not, which indicates that the peptide portions of 6g and 6h adopt an extended conformation in solution.

ChemInform Abstract: Novel Stereoselective Synthesis of (Z)‐α,β‐Unsaturated Esters by Hydrostannylation‐Stille Tandem Reaction of Alkynyl Esters with Aryl Iodides.

(Z)-α,β-Unsaturated esters can be stereoselectively synthesised in one pot under mild conditions and in good yields, by the hydrostannylation of alkynyl esters followed by Stille cross-coupling wit...

Novel Stereoselective Synthesis of (Z)-α,β-Unsaturated Esters by Hydrostannylation-Stille Tandem Reaction of Alkynyl Esters with Aryl Iodides

( Z)-α,β-Unsaturated esters can be stereoselectively synthesised in one pot under mild conditions and in good yields, by the hydrostannylation of alkynyl esters followed by Stille cross-coupling with aryl iodides.

Catalytic Asymmetric Synthesis of (+)-Anthecotulide Using Enyne and Meyer–Schuster Rearrangements

The bioactive sesquiterpene lactone (+)-anthecotulide (1) is synthesized for the first time, in a six-step sequence devoid of protecting groups. The key transformations are a novel Rh(I)-catalyzed asymmetric enyne rearrangement of a terminal alkynyl ester (4), to form the α-methylene-γ-butyrolactone core, and a final-step mild Au(I)-catalyzed Meyer-Schuster rearrangement.

Catalytic [2+2+1] Cross‐Cyclotrimerization of Silylacetylenes and Two Alkynyl Esters To Produce Substituted Silylfulvenes

Three become one: The cationic rhodium(I) complex [Rh(cod)2]BF4 catalyzes the [2+2+1] cross-cyclotrimerization of silylacetylenes and two alkynyl esters, leading to substituted silylfulvenes (see scheme; cod=1,5-cyclooctadiene). The reductive complexation of the silylfulvene product with RhCl3 in EtOH furnished the corresponding dinuclear electron-deficient cyclopentadienyl rhodium(III) complex.

The Catalytic Addition of Alkyl Boranes to Alkynyl Esters Affording Single-Isomer Trisubstituted Olefins

The generation of a series of trisubstituted olefins bearing alkyl substituents is described using a stereoselective and regio­selective addition to alkynyl esters. The method produces trisubstituted olefins as single isomers using a convenient and mild transformation in which alkyl boranes are cross-coupled with alkynyl esters and amides using palladium catalysis.

ChemInform Abstract: Synthesis of Highly Substituted Symmetrical 1,3‐Dienes via Tandem Carbocupration and Organocuprate Oxidation.

AbstractA one‐pot tandem carbocupration/oxidation of alkynyl esters provides rapid access to highly substituted symmetrical 1,3‐dienes [cf.

Anionic Cascade Reaction Followed by Silylative Dieckmann Cyclization: A Straightforward Route to Tricyclic Fused Ring Systems Starting from Alkynyl Esters Tethered to Bicyclo[n.2.0]alkanones

AbstractThe successive addition of sodium ethoxide and TBSOTf (or TMSOTf) to alkynyl esters tethered to bicyclo[n.2.0]alkanones (n = 3–5) promoted a domino anionic reaction and a Dieckmann condensation, respectively, which led to 5‐6‐5, 6‐6‐5, and 7‐6‐5 tricyclic fused ring systems. These systems represent relevant substructures of numerous bioactive compounds.

Synthesis of Highly Substituted Symmetrical 1,3-Dienes via Tandem Carbocupration and Organocuprate Oxidation

A ‘one-pot’ tandem carbocupration/organocuprate oxidation allows the formation of highly substituted symmetrical 1,3-dienes from alkynyl esters and alkyl organolithium or Grignard reagents with three C-C bonds being formed in one step.

Manganese η2-Complexes as Auxiliaries for Stereoselective Aldol Synthesis of Allenyl Carbinols

A convenient and robust manganese auxiliary was linked via an η(2)-bond to alkynyl esters and ketones using a mild complexation reaction with methylcyclopentadienyl manganese tricarbonyl. This complex readily underwent aldol reactions with exclusive α-substitution and in good diastereoselectivities especially with aryl ketone substrates. This selectivity has been rationalized using a cyclic transition state model in which the manganese auxiliary plays a critical role in promoting E(O)-geometry of the cumulenolate intermediate.

A facile approach to substituted acrylates by regioselective and stereoselective addition of thiols and amines to an alkynyl ester in water

Water-promoted hydrothiolation and hydroamination of ethyl propiolate leading to highly regioselective and stereoselective formation of thioacrylates and β-enamino esters in excellent yields, by a simple, efficient, and environmentally friendly reaction procedure without employing any hazardous reagent or solvent is reported.