Substitution des halogéno-1 alcynes-1 par les dérivés organométalliques du cuivre. accès à une nouvelle classe de synthons: application à

1-Bromo- and 1-iodo-1-alkynes are alkylated by organocopper(I) compounds. Alkenylcopper(I) derivatives undergo substitution with retention of configuration leading to conjugated and functional enynes, from which conjugated dienes can be obtained.     

Intramolecular [4 + 2] cycloadditions of benzynes with conjugated enynes, arenynes, and dienes

Benzynes generated by the reaction of o-(trimethylsilyl)aryl triflates with TBAT participate in intramolecular [4 + 2] cycloadditions with conjugated enynes, arenynes, and dienes to furnish highly condensed polycyclic aromatic compounds. [reaction: see text]     

Reactions of Sulfenyl,Sulfinyl, and Sulfonyl Halides with Conjugated Dienes and Enynes. Synthesis of Unsaturated Sulfides,Sulfoxides, and Sulfones

The reactivities of sulfenyl, sulfinyl, sulfonyl halides in additions to conjugated dienes'enynes, and their derivatives are compared. Despite the fact that all these reactions involve cleavage offormally similar S-Cl bonds, the addition direction and rate depend on the structure of the reactants (dienes and enynes; organosulfur acid chlorides).     

Versatile palladium(II)-catalyzed Negishi coupling reactions with functionalized conjugated alkenyl chlorides

Under palladium catalysis, we found that organozincate reagents, generated in situ, by reaction of Grignard compounds with less than molar amounts of zinc chloride, in the presence of conjugated alkenyl chlorides, give rapidly and cleanly the corresponding coupling product in high yields. In this way, aryl as well as primary and secondary alkyl substituents have been introduced successfully. The selectivity of the reaction allows to prepare various functionalized conjugated enynes and dienes from chloroenyne and chlorodiene derivatives bearing a functional group.     

Highly selective synthesis of (E)-3-methyl-1-trialkylsilyl-3-en-1-ynes via trans-selective alkynylation catalyzed by Cl2Pd(DPEphos) and stereospecific methylation with methylzincs catalyzed by Pd(tBu3P)2

[reaction: see text] trans-Selective (>or=98%) monoalkynylation of 1,1-dibromo-1-alkenes and 1,1-dichloro-1-alkenes catalyzed by Cl(2)Pd(DPEphos) followed by stereospecific methylation with Me(2)Zn or MeZnX (X= Cl or Br) catalyzed by Pd((t)()Bu(3)P)(2) provides an efficient and stereoselective (>or=98%) route to 5, convertible to a wide variety of enynes and conjugated dienes. In the cases of 1,1-dibromo-1-alkenes, the Sonogashira alkynylation may also be satisfactory, but it is distinctly less satisfactory than the alkynylzinc reaction in cases where 1,1-dichloro-1-alkenes are used.     

Regio- and stereoselective hydrohalogenation of ynamide components in 1,3-butadiynes with in situ generated HX

A simple protocol for regio-, and stereoselective hydrohalogenation of ynamide moieties in 1,3-butadiyne structures is described. The facile approach enables exact syn-addition of HX to the diyne components, giving just single isomer of the corresponding dienes and enynes.     

Air-assisted addition of grignard reagents to olefins. A simple protocol for a three-component coupling process yielding alcohols

Silylmethyl, tertiary-alkyl, alkenyl, and aryl Grignard reagents underwent intermolecular addition to olefins, such as styrenes, conjugated dienes, and enynes under an air atmosphere to give homologated alcohols. For example, (trimethylsilyl)methylmagnesium chloride and alpha-methylstyrene in ether at room temperature under dry air directly furnished 2-phenyl-4-(trimethylsilyl)-2-butanol in good yield. As the Grignard addition to olefins under argon with rigorous exclusion of O2 did not proceed at all, the above reaction should involve a radical mechanism: an alkyl radical generated by the aerial oxidation of the Grignard reagent adds to olefin, which is followed by oxygenation. Representative examples of this transformation, where products were obtained in good to excellent diastereo- or regioselectivity, are also disclosed.     

Functionalised butanediacetal-protected 1,2-diols as suitable partners for Pd-catalysed cross-coupling reactions

A new method for the synthesis of dienes and enynes containing chiral 1,2-diols is described. The strategy is based on the Pd-catalysed cross-coupling reactions of a series of vinyl and alkynyl asymmetric butanediacetal-protected building blocks. After the coupling, removal of the protecting group leads to the desired functionalised dienes and enynes.     

ArS-Mediated Ad E Reaction of the Cobaltcarbonyl-Complexed Conjugated Enynes

Abstract

A novel approach to the synthesis of functionalized enynes is elaborated based on the protocol of the three-component coupling of arenesulfenyl chlorides, dicobalthexacarbonyl complexes of the conjugated enynes, and nucleophiles of the π-donor type and a possibility to employ the 1,6-enyne derivatives thus prepared as the substrates for the intramolecular Pauson–Khand cyclization is demonstrated.     

A novel approach towards the preparation of functionalized alkyne derivatives via ArS-mediated AdE reaction of cobaltcarbonyl complexed conjugated enynes

A unified protocol of three-component coupling of arenesulfenyl chloride, dicobalthexacarbonyl complexed conjugated enynes, and nucleophiles of π-donor type is applied for the synthesis of functionalized alkynes.     

Addition du di-t-butyl-zinc a la triple liaison des enynes conjugues,simples et fonctionnels

Di-t-butylzinc adds easily to conjugated enynes

. Only the acetylenic bond is involved in this reaction which proceeds via trans-addition. This regioselective and stereoselective addition leads to conjugated dienes

.     

Synthesis and cycloaddition reactions of sulfur-substituted quinolizidine dienes

Synthesis of sulfur-substituted quinolizidine dienes via ring-closing enyne metathesis (RCEYM) of the corresponding enynes has been achieved. The cycloaddition reactions of these dienes with electron-deficient dienophiles give tricyclic and tetracyclic nitrogen-containing products.     

1,2,3-triazole: unique ligand in promoting iron-catalyzed propargyl alcohol dehydration

A 1,2,3-traizole-promoted iron(III)-catalyzed propargyl alcohol dehydration was developed for the synthesis of conjugated enynes. The desired conjugated enynes were prepared in good to excellent yields (up to 95%) with a large substrate scope and excellent stereoselectivity (only Z-isomers).     

Conjugated enynes as a new type of substrates for olefin metathesis

[reaction: see text] It has been demonstrated for the first time that conjugated enynes can be employed as a facile substrate in olefin metathesis with the use of a bispyridine-substituted ruthenium benzylidene catalyst. Cross-metathesis of the enynes with alkenes turns out to proceed with preferential formation of (Z)-isomers over (E)-isomers up to >25:1 in moderate to good yields. The intramolecular version of conjugated enynes affords novel butadienyl cycloalkenes, which are a highly useful synthetic building blocks, in acceptable yields.     

Synthesis of conjugated enynes by assembly of three components, ketones, chloromethyl p-tolyl sulfoxide, and acetylenes, with the magnesium carbenoid 1,2-CC insertion as the key reaction

The reaction of 1-chlorovinyl p-tolyl sulfoxides, which were derived from ketones and chloromethyl p-tolyl sulfoxide, with lithium acetylides gave adducts in moderate to good yields. Treatment of the adducts with Grignard reagents resulted in the formation of magnesium carbenoids by the sulfoxide-magnesium exchange reaction. 1,2-Carbon-carbon insertion (1,2-CC insertion) reaction of the generated magnesium carbenoids took place to afford conjugated enynes in good to high yields. This procedure provides a good method for the synthesis of multi-substituted conjugated enynes.     

Highly regio- and stereoselective synthesis of 1,3-enynes from unactivated ethylenes via palladium-catalyzed cross-coupling

An efficient procedure for regio- and stereoselective synthesis of a series of conjugated enynes by a simple Pd-catalyzed cross-coupling reaction of unactivated ethylenes and ethynyl bromide has been developed. The reaction proceeds smoothly in DMF to give the corresponding products in good to excellent yields. The protocol can tolerate a broad range of functional groups on the substrates.     

Acyclic ketene aminal phosphates derived from N,N-diprotected acetamides: stability and cross-couplings

The synthesis of a stable ketene aminal phosphate (α-phosphoryloxy enecarbamate) derived from N,N-diprotected acetamide, bearing two different removable protecting groups, is disclosed. This synthetic intermediate underwent successful palladium-catalyzed cross-coupling reactions to afford functionalized enynes and dienes.     

Polyunsaturated alkyl amides from Echinacea: synthesis of diynes, enynes, and dienes

The synthesis of 20 alkyl amides, including 15 naturally occurring polyunsaturated alkyl amides previously identified from Echinacea spp. (1-13 and 62) or from Achilla sp. (55) and five previously unknown geometric isomers (23, 28, 67, 73, and 80), is described. Importantly, these amides include all of the major alkyl amides present in commercially used Echinacea extracts. The syntheses demonstrate methodology used for constructing alkyl amides containing conjugated diyne and isomerically pure enyne and diene moieties and may be adapted easily for the preparation of other alkyl amides present in Echinacea spp. Terminal-conjugated diynes were prepared by a Cadiot-Chodkiewitz coupling/deprotection sequence utilizing a protected bromoacetylene, and methyl-substituted diynes were made via a base-catalyzed rearrangement of terminal-skipped diynes. Conjugated dienes were prepared conveniently and with high stereoselectivity by the reduction of enynes or diynes with Rieke zinc. With the exception of 1-2 and 11-12, the alkyl amides are synthesized here for the first time, and their NMR data are consistent with that of the reported isolated natural compounds.     

Synthesis of bromoallenyl pyrrolidines via 1,4-addition to 1,3-enynes

The discovery of the novel reactivity of conjugated enynes,mediated by readily available halogenation reagents,opens a broad range of mechanistically unique pathways for the synthesis of highly functionalized chiral allene derivatives.Bromoallenyl pyrrolidines can be synthesized via 1,4-addition of sulfonamide nitrogen nucleophiles and halogens to conjugated enynes.This process can lead to simultaneous formation of a highly functionalized axially chiral allene and a stereogenic center under economical and e...     

Enhanced reactivity of electron-deficient enynes in the palladium-catalyzed homo-benzannulation of conjugated enynes

We report the high reactivity of electron-deficient enynes in the homo-benzannulation of conjugated enynes in the presence of Pd(PPh3)4. The introduction of electron-withdrawing groups enabled us to carry out the benzannulation of 1-substituted enynes as well as 1,2- and 2,4-disubstituted enynes. Polysubstituted benzenes were prepared in a highly regioselective manner in good to excellent yields.