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Metal-halogen exchange of either (Z)-enynyl bromides or (Z)-dienyl bromides by sec-BuLi produces vinyllithiums that are configurationally stable only at temperatures below -120 deg C and -78 deg C, respectively.Allylation of (Z)-enynylalanates with allyl bromide or methylation of (Z)-enynyl bromides with CH3MgI and Fe(acac)3 catalyst furnishes the corresponding 2-alkyl-1-en-3-ynes.

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A series of Rh(κ2-BHetA)(η2-coe)(IPr) complexes bearing 1,3-bis-hetereoatomic acidato ligands (BHetA) including carboxylato (O,O), thioacetato (O,S), amidato (O,N), thioamidato (N,S), and amidinato (N,N), have been prepared by reacti

The reactions of the rhodium(I) and iridium(I) complexes [M(PhBP3)(C2H4)(NCMe)] (PhBP3=PhB(CH2PPh2)3?) with alkynes have resulted in the synthesis of a new family of p

Copper (I) or copper (II) salts and oxides promote regioselective head-to-head additive dimerization of aromatic and aliphatic terminal alkynes in the presence a catalytic amount of diethylphosphite. The reaction proceeds under ambient conditions without

A series of pincer complexes of Rh has been prepared and tested as catalysts for the dimerization of terminal alkynes. The pincers included aryl/bis(phosphinite) POCOP, aryl/bis(phosphine) PCP, and diarylamido/bis(phosphine) PNP ligands. RhI co

A general regioselective rhodium-catalyzed head-to-tail dimerization of terminal alkynes is presented. The presence of a pyridine ligand (py) in a Rh-N-heterocyclic-carbene (NHC) catalytic system not only dramatically switches the chemoselectivity from alkyne cyclotrimerization to dimerization but also enhances the catalytic activity. Several intermediates have been detected in the catalytic process, including the π-alkyne-coordinated RhI species [RhCl(NHC)(η2-HC ≡CCH2Ph)(py)] (3) and [RhCl(NHC){η2-C(tBu) ≡C(E)CH=CHtBu}(py)] (4) and the RhIII-hydride-alkynyl species [RhClH{-C ≡CSi(Me) 3}(IPr)(py)2] (5). Computational DFT studies reveal an operational mechanism consisting of sequential alkyne Ci￡ H oxidative addition, alkyne insertion, and reductive elimination. A 2,1-hydrometalation of the alkyne is the more favorable pathway in accordance with a head-to-tail selectivity. Control plan: Addition of pyridine to rhodium-N-heterocyclic- carbene catalysts not only switches the chemoselectivity from alkyne cyclotrimerization to dimerization, but also enhances the catalytic activity for the formation of 1,3-enynes (see figure). A 2,1-hydrometalation of the alkyne is the more favorable pathway calculated by DFT.

(Chemical Equation Presented) Silaboration of 1,3-enynes catalyzed by group 10 metal complexes affords 1,3-dienes with vinylborane and vinylsilane functions or 1,2-dienes with allylborane and vinylsilane functions. The type of product formed is determined

A Rh complex of a bulky diarylamino-based PNP pincer ligand is a robust catalyst for the dimerization of terminal alkynes and highly selective for the trans-enyne product. The Royal Society of Chemistry 2006.

A Palladium/imidazolium chloride system has been used to mediate the dimerization of terminal alkynes to enynes. The combination of 1 mol % Pd(OAc)2 and 2 mol % IMes·HCl in the presence of Cs2CO3 as base shows high activit

A novel strategy has been developed for the catalytic synthesis of short oligomers, dimers and/or trimers, of terminal alkynes. The method allows control of the extent of and, in some cases, the regiospecificity in the catalyzed oligomerization of terminal alkynes promoted by bis(pentamethylcyclopentadienyl)actinide dimethyl complexes (Cp*2AnMe2; Cp* = C5Me5, An = Th, U). These metallocene precursors are known to promote the simultaneous production of a large number of differently sized oligomers in the presence of terminal alkynes. However, the addition of specific amines ensures the selective synthesis of short oligomers. Catalytic 'tailoring' to dimers or a mixture of dimers and trimers can be achieved by using nonbulky or bulky amines, respectively. The kinetics in the catalytic oligomerization of 1-hexyne, in the presence of i-BuNH2, mediated by Cp*2ThMe2 are first order in [alkyne], first order in [Th], and inverse first order in [amine]. Kinetic, spectroscopic, and mechanistic data argue that the turnover-limiting step involves the formation of the mono(amido)thorium acetylide complex with rapid insertion of the alkyne and protonolysis by the amine.

The copper(II) - mediated coupling reaction of alkenyl-dialkyl- or trialkyl-boranes with alkynylcopper compounds (generated in situ), in the presence of appropriate solvents and a small amount of water, gives (E)-1,3-enynes (or disubstituted alkynes) with various functional groups in reasonable yields.

Several complexes of the type RuTp(L)(L′)Cl (L, L′ = P, N, O donors) were tested with respect to their ability of promoting catalytic C-C-coupling reactions of terminal acetylenes. When L = tertiary phosphine, predominantly dimerization occurs, RuTp(PPhs

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The complexes L4RuH(C6H5) with L4 = P(CH2CH2CH2PMe2)3, N(CH2CH2PPh2)3, and MeSi(CH2PMe2)3/PMe3 all serve as catalysts for the dimerization of 1-alkynes, RCCH (R = C6H5, n-C4H9, t-C4H9).The reaction proceeds to yield 1,4-disubstituted 1-en-3-ynes.RCH=CH

A highly selective and potentially general methodology for the synthesis of conjugated E,E- and E,Z-dienes, E-enynes, and E-1,2,3-butatrienes via hydroboration of alkynes is reported.The observed stereoselectivity was >98-99percent.

The dimerization of 1-alkynes catalyzed by RhCl(PMe3)3 yields conjugated enynes I and II (I/II = 1.4 - 2.4), with a selectivity of 95 - 98 percent.The data indicate that the reaction proceeds by alkyne insertion into the metal-hydride bond of the intermediate (alkynyl)(hydride)RhIII complexes VII, VIII to give the (alkynyl)(vinyl)RhIII species cis- (IX) and cis- (X) which were isolated.The thermal decomposition of IX and X in solution gives the enynes I and II correspondingly.

Various types of organometals containing lithium and copper react with E and Z epoxysilanes to produce adducts which, either under the reaction conditions or upon treatment with a base, e.g., KH, can be stereospecifically converted to the corresponding E and Z alkenes, respectively.

Treatment of thexylalkenylalkynylboranes with iodine in the presence of potassium methoxide produces (E)-1,3-enynes in good yield (58-82percent) and excellent stereochemical purities (>=95percent).The methodology was successfully applied to the synthesis of (5Z,7E)-5,7-dodecadien-1-ol, the sex pheromone of the forest tent caterpillar (Malacosoma disstria).

Internal conjugated (E)-enynyldialkylboranes were synthesized by successive reactions of 1-iodo-1-alkynes with dialkylboranes and 1-alkynyllithiums in 31-79percent yields. (E)-Enynyldialkylboranes, thus obtained, gave regio- and/or stereospecifically defined corresponding conjugated alkynones by alkaline hydrogen peroxide oxidation, conjugated (E)-enynes by protonolysis with acetic acid, and conjugated enynes bearing an unsaturated group on the internal alkenyl carbon atom by bis(acetylacetonato)copper-catalyzed cross-coupling reaction with allyl bromide or 1-bromo-1-hexyne respectively.

Bis(acetylacetonato)copper is capable of catalyzing cross-coupling reaction of alkenyldicyclohexylborane with 1-bromo-1-alkyne or 3-bromo-1-propene to give conjugated (E)-enzyme or (E)-1,4-diene in a highly stereoselective manner, respectively.

Alkenylcopper intermediates, readily generated from alkenylboron derivates of 9-borabicyclononane (9-BBN), undergo coupling with 1-halo-1-alkynes to provide stereodefined conjugated enynes of high isomeric purity and in yields approaching quantitative.