Nickel-catalyzed addition of benzenethiol to alkynes: Formation of carbon-sulfur and carbon-carbon bonds

Nickel-catalyzed addition of benzenethiol to alkynes leads to alkenyl and dienyl sulfides; the direction of the process can be controlled by varying the PhSH/alkyne ratio. An advanced procedure, which ensures higher yields of 2-phenylsulfanylalkenes, includes gradual addition of alkyne to the other reactants. The structures of conjugated dienyl sulfides formed in the reaction were determined by 2D NMR spectroscopy. Dedicated to Academician O. M. Nefedov on the occasion of his 75th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2030–2034, November, 2006.     

Nickel-catalyzed addition of alkynylboranes to alkynes

Alkynylboration has been achieved in the reaction of alkynyl(pinacol)boranes with alkynes in the presence of nickel catalysts, giving cis-1-borylbut-1-en-3-yne derivatives. 1-Aryl-1-alkynes underwent the alkynylboration regioselectively with the selective introduction of the alkynyl groups at their 1-positions, where the aryl groups were attached. The boryl-substituted enynes were reacted with sp2 halides under the Suzuki-Miyaura coupling conditions, giving highly conjugated enynes in high yields.     

Nickel-catalyzed indium(I)-mediated double addition of aldehydes to 1,3-dienes

In the presence of InI, Ni(acac)2 and PPh3, several 1,3-dienes were reacted with two molecules of aldehyde to give the corresponding 1,4- and 1,6-diols. The regioselectivity of the 1,4-/1,6-diol was efficiently regulated by the addition of water; the 1,6-diol was obtained selectively in dry THF, whereas the 1,4-diol was obtained predominantly in DMI containing a small amount of water.     

Nickel-catalyzed decarbonylative addition of phthalimides to alkynes

An intermolecular nickel-catalyzed addition reaction has been developed where N-arylphthalimides react with alkynes to afford substituted isoquinolones. A mechanistic rationale is proposed, implying nucleophilic attack of Ni(0) to an amide as the primary step of the catalytic cycle.     

RuCl3-catalyzed alkenylation of aromatic C-H bonds with terminal alkynes

RuCl3-catalyzed regio- and/or stereoselective alkenylation reactions of a variety of arylpyridines proceeded efficiently with terminal alkynes or allylic compounds in the presence of benzoyl peroxide or benzoic acid.     

Rhodium-catalyzed isomerization of unactivated alkynes to 1,3-dienes

A rhodium/binap complex has been found to effectively catalyze the isomerization of unactivated internal alkynes to the corresponding 1,3-dienes in the presence of an azomethine imine as the reaction promoter.     

Nickel-catalyzed addition of dimethylzinc to aldehydes across alkynes and 1,3-butadiene: an efficient four-component connection reaction

In the presence of 10 mol % of Ni(acac)(2), four components comprising Me(2)Zn, alkynes, 1,3-butadiene, and carbonyl compounds combine in this order in 1:1:1:1 ratio to furnish (3E,6Z)-octadien-1-ols 1 in good yields. Similarly, the coupling reaction of Me(2)Zn, 1,omega-dienynes 5, and carbonyls furnishes 1-alkylidene-2-(4'-hydroxy-(1'E)-alkenyl)cyclopentanes and -cyclohexanes 6 and their oxygen and nitrogen heterocycle derivatives in good yield and an excellent level of 1,5-diastereoselectivity with respect to the cycloalkane methine carbon and the OH-bearing carbon of the C2 side chain. The reaction is completed in most cases within 1 h at room temperature under nitrogen, tolerates an ester, a hydroxy, an allyl and propargyl ethers, an allylamino, and a pyridyl functionalities, and accommodates a variety of aromatic and aliphatic alkynes and carbonyls (aldehydes and ketones).     

Nickel-catalysed addition of organoboronates to 1,3-dienes

Aryl- and alkenylboronates were found to add to 1,3-dienes in the presence of a catalytic amount of bis(1,5-cyclooctadiene)nickel, where a proton source in combination with a solvent considerably controls the regioselectivity.     

A direct synthesis of functionalized styrenes and terminal 1,3-dienes via aqueous Wittig chemistry with formalin

A direct synthesis of functionalized styrenes including synthetically valuable styryl halides and terminal 1,3-dienes is reported directly from benzylic and allylic alcohols and aqueous formalin involving microwave assisted phosphonium salt formation and Wittig olefination under mildly basic conditions.     

Acetoxypalladation of unactivated alkynes and capture with alkenes to give 1-acetoxy-1,3-dienes taking dioxygen as terminal oxidant

A new and general protocol for the synthesis of 1-acetoxy-1,3-dienes by an acetoxypalladation/Heck cross-coupling/β-H elimination tandem process is described in which dioxygen is the terminal oxidant. Electron-rich and electron-deficient alkynes are both effective substrates in this system. It is the first example of acetoxypalladation of diarylalkynes.     

Palladium-catalyzed conjugate addition of terminal alkynes to enones

A practical protocol for the hydroalkynylation of enones using Pd catalysis is reported. The reaction proceeds efficiently with a variety of alkynes as well as with several cyclic and acyclic enones, providing synthetically relevant β-alkynyl ketones in good to excellent yields.     

Rhenium-catalyzed regiodivergent addition of indoles to terminal alkynes

An efficient rhenium-catalyzed site-switchable addition of indoles to terminal alkynes is described. A variety of bisindolylalkane derivatives are expeditiously synthesized in high yields with excellent regioselectivity. Preliminary mechanistic study sheds light on the observed regiodivergent addition.     

Nickel-catalyzed amination of 1,3-dienes Evidence for a π-allyl intermediate

syn-π-Crotylbis(triethyl phosphite) nickel hexafluorophosphate reacts with morpholine to give 1-(N-morpholino)-2-butene. This π-crotylnickel complex, without added acid, catalyzes the reaction of butadiene with morpholine. From these observations, π-allyl intermediates are proposed as intermediates in the amination of 1,3-dienes. trans-1,3-Pentadiene reacts with amines more easily than the cis-isomer. The different reactivities are discussed on the basis of the stability of π-allyl complexes which are assumed to be key intermediates.     

Free radical telluroacylative addition of telluroesters to terminal alkynes

Vinyl selenides and tellurides are important precursors of many kinds of organic compounds, particular the substituted alkenes that occurred in many biologically active compounds as skeleton structures. Thus the study of vinyl selenides and tellurides has attracted considerable attention in recent years. The bifunctional addition reactions involving selenium and tellurium moieties are the latest methods for preparation of vinyl selenides with various functional groups. Recently we have reported the selenocarbonylation of alkynes with selenoesters catalyzed by cuprous halides. Nevertheless the similar bifunctional addition involving tellurium atoms has not been reported. Considering the C-Te bonds are easier to be broken than corresponding C-Se bonds, the vinyl tellurides containing electron-withdrawing groups may have particular reactivity and application in the preparation of substituted alkenes. Herein we describe the synthesis of β-aryltelluro-α,β-unsaturated ketones via bifunctional addition.     

Intermolecular radical addition of alkylthio- and arylthiodiphenylphosphines to terminal alkynes

Intermolecular radical thiophosphination of terminal alkynes with alkylthio- and arylthiophosphines affords 1-thio-2-phosphino-1-alkenes in good yields. The addition reaction proceeds predominantly in an anti fashion to yield E isomers.     

Enantioselective addition of terminal alkynes to isolated isoquinoline iminiums

[reaction: see text] The asymmetric, catalytic addition of terminal alkynes to discrete alkyliminium species in the presence of copper bromide, QUINAP ligand, and triethylamine is reported. The reaction proceeds in high yield and high enantiomeric excess with a variety of substrates in solution and is also amenable to solid-phase synthesis.     

Transition metal-free addition of ketones or nitriles to 1,3-dienes

The simpler the better (or going green): The first examples of the catalytic addition of 1,3-dienes to simple ketones or nitriles are described. These reactions can be effected on a kilogram scale, representing the shortest access featuring a perfect atom economy to molecules of interest in the perfume industry.