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A NiH-catalyzed migratory hydroalkenylation reaction of olefins with alkenyl bromides has been developed, affording benzylic alkenylation products with high yields and excellent chemoselectivity. The mild conditions of the reaction preclude olefinic products from undergoing further isomerization or subsequent alkenylation. Catalytic enantioselective hydroalkenylation of styrenes was achieved by using a chiral bisoxazoline ligand.

This work reports gold-catalyzed 1,4-oxofunctionalizations of 3-en-1-ynamides with nitrones, yielding two distinct E-configured products. We obtained 1,4-oxoarylation products from 3-en-1-ynamides bearing C(4)-electron-donating substituents and 1,4-oxoamination products from those analogues bearing C(4)-aryl substituents. We propose that if vinylgold carbenes are stable, imines undergo a para-arylation on these gold carbenes. If vinylgold carbenes are highly electron-deficient, this N-attack is irreversible to enable 1,4-oxoaminations.

One of the most oft-employed methods for C-C bond formation involving the coupling of vinyl-halides with aldehydes catalyzed by Ni and Cr (Nozaki-Hiyama-Kishi, NHK) has been rendered more practical using an electroreductive manifold. Although early studies pointed to the feasibility of such a process, those precedents were never applied by others due to cumbersome setups and limited scope. Here we show that a carefully optimized electroreductive procedure can enable a more sustainable approach to NHK, even in an asymmetric fashion on highly complex medicinally relevant systems. The e-NHK can even enable non-canonical substrate classes, such as redox-active esters, to participate with low loadings of Cr when conventional chemical techniques fail. A combination of detailed kinetics, cyclic voltammetry, and in situ UV-vis spectroelectrochemistry of these processes illuminates the subtle features of this mechanistically intricate process.

[Figure not available: see fulltext.] Under the action of an excess of trifluoromethanesulfonic acid, 1-aryl-5-phenylpent-4-en-2-yn-1-ones cyclize intramolecularly to 6-aryl-2-phenyl-2,3-dihydropyran-4-ones. The reaction proceeds at room temperature for 1

Various aryl Fischer carbenes reacted with alkynes having adjacent acyloxy or carbonate groups to regioselectively deliver 3-substituted 1-indanones. The acyloxy or carbonate group probably coordinates with the Cr metal to give a tetra-coordinated chromium complex forming a six-membered ring that retards CO insertion for ketene formation, which is required for benzannulation. Alternatively, the ortho position aryl ring attack results in pentannulation, providing regioselectively 3-substituted 1-indanones. The method is extended to the synthesis of the core structure of 3-epi-mutisianthol.

A unique concept for the intermolecular denitrogenative annulation of 1,2,3,4-tetrazoles and alkynes was discovered by using a catalytic amount of Fe(TPP)Cl and Zn dust. The reaction precludes the traditional, more favored click reaction between an organic azide and alkynes, and instead proceeds by an unprecedented metalloradical activation. The method is anticipated to advance access to the construction of important basic nitrogen heterocycles, which will in turn enable discoveries of new drug candidates.

A new and highly efficient vicinal thiosulfonylation of 1,1-dibromo-1-alkenes with thiosulfonates in the presence of cesium carbonate has been developed. The metal-free diheterofunctionalization is an operationally simple to access a wide range of (E)-1,2-thiosulfonylethenes (α-aryl-β-thioarylvinyl sulfones) in moderate to high yields with high levels of stereoselectivities. Further, scalable reactions have been demonstrated for this transformation, thus illustrating its efficiency and practicality. (Figure presented.).

The first highly enantioselective nucleophilic addition reaction of phosphites with 2H-azirines has been developed. The reaction was applied to various 3-substituted 2H-azirines using novel chiral bis(imidazoline)/ZnII catalysts to afford produ

The methods available for the synthesis of chalcogenophenes, in general, are associated with drawbacks of harsh conditions, use of costly metals, broad applicability, tedious purification process and low yield. To avoid these drawbacks a transition metal-free iodine-catalyzed reaction of aryl-susbstituted 1,3-dienyl bromides with potassium selenocyanate/potassium sulfide (KSeCN/K2S) leading to the corresponding selenophenes and thiophenes has been developed. Iodine is relatively benign, less expensive and readily available. Several diversely substituted selenophenes and thiophenes have been obtained by this procedure in high yields. Using this procedure 2-(4-chlorophenyl)thiophene, a key intermediate for the synthesis of a melanin concentrating hormone receptor ligand involved in the treatment of eating disorders, weight gain, obesity, depression and anxiety has been synthesized. Although the reaction is one-pot essentially it proceeds in two steps involving a selenocyanate/thiolate intermediate leading to the selenophene/thiophene. The simple operation, use of inexpensive reagents and a metal-free process make this procedure more attractive for an easy access to substituted selenophenes and thiophenes. (Figure presented.).

The use of pyridine as the sole ligand for the reductive vinylation of unactivated secondary alkyl halides under Ni-catalyzed conditions has been developed. Both alkyl- and aryl-substituted vinyl bromides are suitable, in which alkyl-decorated α-alkenyl bromides resulted in the α-products in good results.

The tricyclohexylphosphine-catalyzed [3 + 2] cycloaddition of (E)-alkyl 5-substituted phenylpent-4-en-2-ynoates with [60]fullerene was studied. This reaction undergoes an initial 1,3-addition of phosphines toward the α-carbons of enynoates. Subsequent cycloaddition of the generated 1,3-dipoles with [60]fullerene and elimination of tricyclohexylphosphines resulted in cyclopentenofullerenes in 20-43% yields. The isolated cyclopentenofullerenes were observed to serve as n-type materials in organic photovoltaics, providing a maximum average power conversion efficiency of 3.79 ± 0.29% upon embedding with P3HT in the active layer.

This work describes the vinylation of α-halo carbonyl compounds with vinyl bromides under Ni-catalyzed reductive coupling conditions. While aryl-conjugated vinyl bromides entail pyridine as the sole labile ligand, the alkyl-substituted vinyl bromides require both bipyridine and pyridine as the co-ligands.

A multicomponent multicatalyst reaction (MC)2R for constructing fully substituted 1,2,3-triazoles is reported. An application of chemoselectivity and latent catalysis in a sequence of multicatalytic reactions confers control over a number of undesired processes, where all of the reagents coexist in the same reaction vessel. The sequence of a chemoselective copper-catalyzed azide alkyne cycloaddition followed by a palladium/copper-catalyzed Sonogashira cross-coupling afforded 1,2,3-triazoles regioselectively with good to high yields and a broad scope.

A novel gold-catalyzed intermolecular ynamide amination-initiated aza-Nazarov cyclization has been developed, allowing the facile and efficient synthesis of various 2-aminopyrroles in moderate to good yields. Furthermore, a mechanistic rationale for this

This work emphasizes the synthesis of substituted vinyl arenes by reductive coupling of aryl halides with vinyl bromides under mild and easy-to-operate nickel-catalyzed reaction conditions. A broad range of aryl halides, including heteroaromatics, and vinyl bromides were employed to yielding products in moderate to excellent yields with high functional-group tolerance. The nickel-catalytic system displays good chemoselectivity between the two C(sp2)-halide coupling partners, thus demonstrating a mechanistic pathway distinct from other stepwise protocols.

Cascade Pd-catalyzed alkene carboamination/Diels-Alder reactions between bromodienes and amines bearing two pendant alkenes are described. These transformations generate 4 bonds, 3 rings, and 3-5 stereocenters to afford polycyclic nitrogen heterocycles wi

Pd-catalyzed coupling of 1,3-dienyldibromides with triarylbismuths was demonstrated for the synthesis of a diverse range of 1,3-enynes. This study provided easy access to a range of functionalized 1,3-enynes in high yields utilizing triarylbismuths in sub

The dual role of the bicyclic amidine base 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) was demonstrated in a synthesis of terminal aryl- and styryl-acetylenes. Mechanistically, a tandem process involving elimination/Umpolung/protonation occurs in a single step to generate terminal aryl- and styryl-acetylenes from geminal dibromoalkenes. The key to the success of this transformation lies in the organobase-mediated generation of the acetylide from the 1-bromoalkynes at room temperature. The unique characteristics of DBU as an inherently safer reagent make it an attractive alternative to previous systems wherein required pyrophoric reagents and nonambient temperatures remain unsolved issues. The procedure does not work for the synthesis of alkyl-acetylenes.

Palladium-catalyzed cross-coupling reactions of 1,1-diboronates with vinyl bromides and dibromoalkenes were found to afford 1,4-dienes and allenes, respectively. These reactions utilize the high reactivities of both 1,1-diboronates and allylboron intermediates generated in the initial coupling.

Regiocontrolled hydrations of 1-aryl-3-en-1-ynes have been accomplished with IPrAuOTf and PtCl2/CO to yield 3-en-1-ones and 2-en-1-ones efficiently; our experimental data indicates that the sizes of catalysts play an important role. This journa

N-Alkynylated sulfoximines have been obtained by copper-catalyzed cross-coupling reactions starting from NH-sulfoximines and bromoacetylenes in moderate to good yields. The reaction conditions are mild, and the substrate scope is wide.

An efficient protocol for the synthesis of selenophenes and selanyl selenophenes has been achieved by a simple one-pot reaction of 1,3-dienyl bromides and 1,3-dienyl-gem-dibromides respectively with KSeCN catalyzed by CuO nanoparticles. Several aryl, alke

A Ni-catalyzed asymmetric reductive cross-coupling between vinyl bromides and benzyl chlorides has been developed. This method provides direct access to enantioenriched products bearing aryl-substituted tertiary allylic stereogenic centers from simple, stable starting materials. A broad substrate scope is achieved under mild reaction conditions that preclude the pregeneration of organometallic reagents and the regioselectivity issues commonly associated with asymmetric allylic arylation.

A novel nickel(II)-magnesium-mediated cross-coupling of diphenylphosphine oxide with a variety of 1,1-dibromo-1-alkenes has been developed, which provides a powerful and general methodology for the stereoselective synthesis of various (E)-1-alkenylphosphine oxides or bisphosphine oxides, with operational simplicity of the procedure, good to high yields and broad substrate applicability. Mechanistic studies reveal that the reaction might involve a Hirao reduction, cross-coupling and Michael addition. Copyright

Alkenylaluminums undergo asymmetric copper-catalyzed conjugate addition (ACA) to β-substituted enones allowing the formation of stereogenic all-carbon quaternary centers. Phosphinamine-copper complexes proved to be particularly active and selective compared with phosphoramidite ligands. After extensive optimization, high enantioselectivities (up to 96 % ee) were obtained for the addition of alkenylalanes to β-substituted enones. Two strategies for the generation of the requisite alkenylaluminums were explored allowing for the introduction of aryl- and alkyl-substituted alkenyl nucleophiles. Moreover, alkyl-substituted phosphinamine (SimplePhos) ligands were identified for the first time as highly efficient ligands for the Cu-catalyzed ACA. Chiral synthesis made easy: The copper-catalyzed conjugate addition of alkenylaluminum reagents to 3-substituted cyclic enones allows for the formation of all-carbon chiral quaternary centers (see scheme; CuTC=copper(I) thiophene-2-carboxylate). Chiral phosphinamine (SimplePhos) ligands were found to be highly efficient for this transformation.

Cu-catalyzed decarboxylative alkynylation of quaternary α-cyano acetate salts with alkynyl bromides and alkynyl chlorides is described. This new reaction can be used for preparing functionalized butynenitrile derivatives.

Spectroscopic investigations and the results of calculations on the title bis-imidazolium salt, its mono-and bis-carbenes, and its interactions with palladium are presented. In addition, we report on the scope and limitations of metal-catalyzed cross-coupling reactions performed with the title bis-imidazolium salt. The salt proved to be an efficient ligand precursor in room-temperature Suzuki-Miyaura reactions, C-C couplings with sterically extremely hindered biaryls,selective thiophene arylations, and couplings with vinylic chlorides. Spectroscopic investigations and the results of calculations on the title bis-imidazolium salt, its mono-and bis-carbenes, and its interactions with palladium are presented. In addition, we report on the scope and limitations of metal-catalyzed cross-coupling reactions performed with the title bis-imidazolium salt. Copyright

The copper-catalyzed conjugate addition of various Grignard reagents to polyconjugated enones (dienone and enynone derivatives) is reported. The catalyst system, composed of copper triflate and an NHC ligand, led to the unusual selective formation of the 1,4-addition products. This reaction allows for the creation of all-carbon chiral quaternary centers with enantiomeric excesses up to 99 %. The remaining unsaturation on the 1,4 adducts give access to valuable synthetic transformations. Copyright

An acid-catalyzed Dieckmann-type reaction has been developed to access functionalized bicyclo[3.2.1]alkenediones. This methodology has been successfully extended to more substituted and larger ring homologues, providing a new and efficient route to the core of numerous attractive natural products and their analogues.

The copper-catalyzed direct alkynylation of azoles with 1,1-dibromo-1-alkenes as electrophiles is described. These easily accessible substrates are a useful addition to the field of direct alkynylations in an efficient and functional group tolerant reaction to provide a straightforward entry to diverse alkynyl heterocycles.

A cyclobutene-1,2-bis(imidazolium) salt proved to be an efficient catalyst precursor for one-pot tandem Suzuki-Miyaura/dehydrobromination reactions for the synthesis of alkynes starting from 1,1-dibromoalkenes and palladium(II) acetate, aryl boronic acids, and potassium tert-butoxide in toluene. Starting materials were prepared from aldehydes under Corey-Fuchs conditions. Georg Thieme Verlag Stuttgart New York.

A simple procedure for the use of triisopropylphosphite in the Ramirez olefination is described. This reagent is equally or more reactive than PPh 3 toward aldehydes and ketones in the gem-dibromoolefination of aldehydes and ketones. Under the

Stable silyl vinylketenes were prepared via the thermal reaction of Fischer carbene complexes with triisopropylsilyl- or tert-butyldimethylsilyl- substituted alkynes. The ability of these silyl vinylketenes to participate with carbenoid reagents in [4 + 1

Approaches to the preparation of C1-homologated dibromoalkenes and terminal alkynes from activated alcohols using one-pot tandem oxidation processes (TOPs) with manganese dioxide are outlined. The conversion of alcohols into dibromoalkenes is described using dibromomethyltriphenylphosphonium bromide and the formation of terminal alkynes was achieved via a sequential one-pot, two-step process utilising the Bestmann-Ohira reagent.

(Chemical Equation Presented) Various substituted conjugated dienes have been made by olefin cross-metathesis. Using either electronic or steric "protection," one of the olefins of the conjugated diene was deactivated relative to the other for cross-metathesis. The reactions proceed with very high chemoselectivity and, when steric deactivation is used, very high diastereoselectivity.

A practical and concise route to dibromoalkenes directly from activated alcohols in good to excellent yields using a new Tandem Oxidation Procedure (TOP) is reported. We also describe the use of these dibromoalkenes as intermediates in a one-pot route to 4,5-dihydro-1H-imidazoles and in the synthesis of bromoalkynes through MTBD-induced elimination.

Alkynes R-C≡CH were obtained in good yield through a one-pot procedure by a sequence of reactions starting from a Wittig-type condensation of the aldehydes RCHO with the ylide derived from dibromomethyltriphenylphosphonium bromide 5. The same reactions could also be used to prepare the intermediate dibromoalkenes RCH=CBr2, and in certain cases, the bromoalkynes R-C≡CBr.

A novel approach to the synthesis of retinoids and arotinoids (including heterocyclic analogs) is described which is based on the thallium-accelerated palladium-catalyzed cross-coupling of boronic acids with a variety of electrophiles (the Suzuki reaction).

Control of Reactions with Tribromomethyl Anions/Dibromocarbene by the Nature of the Phase Transfer Catalyst Conversion of (substituted) allyl bromides with bromoform/sodium hydroxide/phase transfer catalyst may be directed towards dibromocarbene addition or substitution by tribromomethyl anion by choice of the catalyst.The observed effects (addition: substitution in the primary step variable between maximally 92:1 and 1:91) are by far the largest reported for specific catalyst influences.Small, hard cations favor the carbene route, sterically shielded and highly delocalized ones favor the substitution process.

1,1-Dibromoolefins 4 are obtained in good yield from the reaction of aldehydes 1 with triphenylphosphane (2) and carbon tetrabromide (3).Reaction of 4 with three moles of methylene(triphenyl)phosphorane (8) leads to the propargylidene(triphenyl)phosphoranes 11 which react with aldehydes to give the enynes 13.The ylides 11 can also prepared via the reaction of bromoacetylenes 7, which can be obtained from 4, with two moles of 8.This reaction sequence allows the synthesis of new retinoids with enyne structures from retinal.