A useful synthesis of α,β-bis(methylseleno)alkanes and α,δ-bis(methylseleno)alk-2-enes by the reactions of alkenes and 1,3-dienes with B(SeMe)3-Lewis acid

Reactions of tris(methylsenleno)borane-SnCl₄ with alkenes 1a–g gave α,β-bis(methylseleno)alkanes 2a –g, stereospecifically, and reactions with 1,3-dienes 1i–k afforded α,β-bis(methylseleno)alk-2-enes 2i–k , regioselectively.     

Regioselective cyclotrimerization of phenylacetylenes to 1,2,4-triarylbenzenes catalyzed by iridium-diphosphine complexes

The organoiridium derivatives HIr(cod)(P-P) (cod=1,5-cyclooctadiene; P-P=dppm (bis(diphenylphosphino)methane), dppe (1,2-bis(diphenylphosphino)ethane), dppp (1,3-bis(diphenylphosphino)propane), dppb (1,4-bis(diphenylphosphino)butane)) catalyze the regioselective cyclotrimerization of phenylacetylene as well as of its derivatives p-CH₃OC₆H₄CCH and p-CF₃C₆H₄CCH. The catalytic activity of the precursors as well as the selectivity towards formation of the 1,2,4-triarylbenzenes (up to 100%) are influenced by the diphosphine, and both increase by decreasing the size of the phosphine-iridium chelate ring.     

Synthesis of functionalized triarylmethanes by combination of FeCl3-catalyzed benzylations of acetylacetone with [3+3] cyclocondensations

Functionalized triarylmethanes are prepared in two steps by FeCl₃-catalyzed benzylation of acetylacetone to give 3-(diarylmethyl)pentane-2,4-diones and subsequent formal [3+3] cyclization of the latter with 1,3-bis(trimethylsilyloxy)-1,3-dienes.     

Cross-coupling of E,E-1,4-diiodobuta-1,3-diene with nucleophiles catalyzed by Pd or Ni complexes: a new route to functionalized dienes

E,E-1,4-Diiodobuta-1,3-diene can enter into cross-coupling reactions with carbon- or other element-centered nucleophiles in the presence of Pd or Ni complexes as catalysts. Convenient procedures were developed for the stereoselective synthesis of E,E-1,4-dialkenylbuta-1,3-dienes, dienyl-1,4-bisphosphonates, E,E-1,4-bis(diphenylphosphino)buta-1,3-diene, E,E-1,4-diphenylbuta-1,3-diene, and E,E-1,4-bis(thiophenyl)buta-1,3-diene.     

Planar Ni(II) 1,2-dithiolenes involving bidentate P-donor ligands

A series of planar Ni(II) dithiolenes derived of maleonitriledithiol (mnt), benzene-1,2-dithiol (bdt) and toluene-3,4-dithiol (tdt) with bidentate P,P-ligands (dppe = 1,2-bis(diphenylphosphino)ethane, dppp = 1,3-bis(diphenylphosphino)propane, dppb = 1,4-bis(diphenylphosphino)butane, dpppn = 1,5-bis(diphenylphosphino)pentane) of the [Ni(P,P)(dithiol)] type have been synthesized. The compounds have been characterized by elemental analysis, IR and electronic spectroscopies, magnetochemical, conductivity measurements and thermal analysis. Single crystal X-ray analysis of [Ni(dpppn)(mnt)] confirmed a planar geometry of NiP₂S₂ chromophore. Possible practical applications such as use of these compounds for vulcanization accelerators and their anticholinesterase activity were evaluated.     

Three-component reactions leading to 2D and 3D metal-organic frameworks assembled on dinickel-carboxylate secondary building units

Three-component reactions involving Ni(II) ions and dicarboxylate and bipyridyl ligands under hydrothermal conditions produce two novel metal-organic coordination polymers formulated empirically as [Ni(PDA)(BPE)] (1) and [Ni₂(PDA)₂(BPP)(H₂O)]·2.5H₂O (2), where PDA = 1,4-phenylenediacetate, BPE = 1,2-bis(4-pyridyl)ethane, and BPP = 1,3-bis(4-pyridyl)propane. Both compounds possess 2D or 3D metal-organic frameworks (MOFs) that are assembled on dinickel-carboxylate secondary building units. Compound 1 has a condensed 3D MOF, whereas 2 contains void between 2D MOFs where guest water molecules reside. Both compounds demonstrate antiferromagnetic coupling between Ni(II) ions.     

Dimerization of vinylcyclopropane and its codimerization with 1,3-dienes catalyzed by cobalt complexes

Conclusions The dimerization of vinylcyclopropane to 2-cyclopropyl-1,5(Z)-heptadiene and the codimerization of vinylcyclopropane with 1,3-dienes (butadiene, isoprene, and 2-cyclopropylbutadiene) with the formation of 2-cyclopropyl-1,4-hexadienes were carried out in the presence of the catalytic systems Co(acac)₃-1,2-bis(diphenylphosphino)ethane [1,2-bis(diphenylphosphino)methane]-AlEt₂Cl.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1356–1360, June, 1988.     

Bis(alkoxycarbonyl) complexes of platinum: preparation,reactivity and their role in carbonylation reactions

bis(alkoxycarbonyl) complexes of platinum of the type [Pt(COOR)₂L] [L = 1,2-bis(diphenylphosphino)ethane (dppe), 1,3-bis(diphenylphosphino)propane (dppp), l,4-bis(diphenylphosphino)butane (dppb), 1,1'-bis(diphenylphosphino)ferrocene (dppf) or 1,2-bis-(diphenylphosphino)benzene (dpb); R = CH₃, C₆H₅ or C₂H₅] were obtained by reaction of [PtCl₂L] with carbon monoxide and alkoxides. Palladium and nickel complexes gave only carbonyl complexes of the type [M(CO)L] or [M(CO)₂L]. The new complexes were characterized by chemical and spectroscopic means. The X-ray structure of [Pt(COOCH₃)₂(dppf] · CH₃OH is also reported. The reactivity of some alkoxycarbonyl complexes was also investigated.     

Cobalt-catalysed asymmetric hydrovinylation of 1,3-dienes

In the presence of bidentate 1,n-bis-diphenylphosphinoalkane-CoCl₂ complexes {Cl₂Co[P ∼ P]} and Me₃Al or methylaluminoxane, acyclic (E)-1,3-dienes react with ethylene (1 atmosphere) to give excellent yields of hydrovinylation products. The regioselectivity (1,4- or 1,2-addition) and the alkene configuration (E- or Z-) of the resulting product depend on the nature of the ligand and temperature at which the reaction is carried out. Cobalt(ii)-complexes of 1,1-diphenylphosphinomethane and similar ligands with narrow bite angles give mostly 1,2-addition, retaining the E-geometry of the original diene. Complexes of most other ligands at low temperature (–40 °C) give almost exclusively a single branched product, (Z)-3-alkylhexa-1,4-diene, which arises from a 1,4-hydrovinylation reaction. A minor product is the linear adduct, a 6-alkyl-hexa-1,4-diene, also arising from a 1,4-addition of ethylene. As the temperature is increased, a higher proportion of the major branched-1,4-adduct appears as the (E)-isomer. The unexpectedly high selectivity seen in the Co-catalysed reaction as compared to the corresponding Ni-catalysed reaction can be rationalized by invoking the intermediacy of an η⁴-[(diene)[P ∼ P]CoH]⁺-complex and its subsequent reactions. The enhanced reactivity of terminal E-1,3-dienes over the corresponding Z-dienes can also be explained on the basis of the ease of formation of this η⁴-complex in the former case. The lack of reactivity of the X₂Co(dppb) (X = Cl, Br) complexes in the presence of Zn/ZnI₂ makes the Me₃Al-mediated reaction different from the previously reported hydroalkenylation of dienes. Electron-rich phospholanes, bis-oxazolines and N-heterocyclic carbenes appear to be poor ligands for the Co(ii)-catalysed hydrovinylation of 1,3-dienes. An extensive survey of chiral ligands reveals that complexes of DIOP, BDPP and Josiphos ligands are quite effective for these reactions even at –45 °C and enantioselectivities in the range of 90–99% ee can be realized for a variety of 1,3-dienes. Cobalt(ii)-complex of an electron-deficient Josiphos ligand is especially active, requiring only <1 mol% catalyst to effect the reactions.     

α, ω-Disäureamide aus 1,2-alkadienen und isocyanaten an nickel(O)-komplexen

The 5-membered nickelacyclic compounds formed by 1,2-dienes and phenylisocyanates on nickel(O) complexes react with oxidizing agents such as FeCl₃, iodine or Ce⁴⁺ salts by CC coupling to α, ω-diamides.     

Alkynylcyanation of alkynes and dienes catalyzed by nickel

Alkynyl cyanides are found to add across alkynes and 1,2-dienes in the presence of a catalyst prepared in situ from Ni(cod)₂, xantphos, and BPh₃. A range of functionalized conjugated cis-enynes are obtained with high regioselectivity. The addition reaction across norbornadiene proceeds in the absence of BPh₃ to give exo-cis adduct exclusively. A stoichiometric reaction of an alkynyl cyanide, Ni(cod)₂, xantphos, and BPh₃ gives trans-(xantphos)Ni(CNBPh₃)(CCSiMe₂t-Bu), which is suggested to be a plausible reaction intermediate of the alkynylcyanation reaction.     

Nickel(0)-catalyzed asymmetric hydrocyanation of 1,3-dienes

1,2-Bis-diarylphosphinites are excellent ligands for the Ni(0)-catalyzed hydrocyanation of certain types of 1,3-dienes. 1-Phenyl-1,3-butadiene, 1-vinyl-3,4-dihydronaphthalene, and 1-vinylindene undergo highly regioselective hydrocyanation under ambient conditions to give exclusively the 1,2-adducts in good to excellent yields. Using bis-1,2-diarylphosphinites derived from d-glucose, the highest enantioselectivities to-date for asymmetric hydrocyanation of 1,3-dienes (70-83% ee's) have been obtained.     

N‐(2‐Hydroxyethyl)‐N‐methyldithiocarbamato Complexes of Nickel(II) with Phosphorus Donor Ligands

Planar nickel(II) complexes involving N‐(2‐Hydroxyethyl)‐N‐methyldithiocarbamate, such as [NiX(nmedtc)(PPh₃)] (X = Cl, NCS; PPh₃ = triphenylphosphine), and [Ni(nmedtc)(P‐P)]ClO₄(P‐P = 1,1‐bis(diphenylphosphino)methane(dppm); 1,3‐bis(diphenylphosphino)propane (1,3‐dppp); 1,4‐bis(diphenylphosphino)butane(1,4‐dppb) have been synthesized. The complexes have been characterized by elemental analyses, IR and electronic spectroscopies. The increased νC–N value in all the complexes is due to the mesomeric drift of electrons from the dithiocarbamate ligands to the metal atom. Single crystal X‐ray structure of [Ni(nmedtc)(1,3‐dppp)]ClO₄·H₂O is reported. In the present 1,3‐dppp chelate, the P–Ni–P angle is higher than that found in 1,2‐bis(diphenylphosphino)ethane‐nickel chelates and lower than 1,4‐bis(diphenylphosphino)butane‐nickel chelates, as a result of presence of the flexible propyl back bone connecting the two phosphorus atoms of the complex.     

Trinuclear copper(I) complex of 1,3-bis(2-pyridinylmethyl)imidazolylidene as a carbene-transfer reagent for the preparation of catalytically active nickel(II) and palladium(II) complexes

Reactions of 1,3-bis(pyridin-2-ylmethyl)-1H-imidazol-3-ium hexafluorophosphate, ([HL1](PF₆), L1 = 1,3-bis(pyridin-2-ylmethyl)imidazolylidene) and 1,3-bis(pyridin-2-ylmethyl)-1H-benzimidazol-3-ium hexafluorophosphate ([HL2](PF₆), L2 = 1,3-bis(pyridin-2-ylmethyl)benzoimidazolylidene) with cuprous oxide in acetonitrile readily yielded trinuclear complexes [Cu₃(L1)₃(PF₆)₃] (1) and [Cu₃(L2)₃(PF₆)₃] (2). Treatment of 1 with Ni(PPh₃)₂Cl₂ and Pd(cod)Cl₂ gave [Ni(L1)Cl](PF₆) (3) and [Pd(L1)Cl](PF₆) (4), respectively, due to transmetalation. [Ni(L1)₂](PF₆)₂ (5) was obtained from the reaction of [Cu₃(L1)₃(PF₆)₃] and Raney nickel in acetonitrile. All these complexes have been fully characterized. Both 1 and 2 consist of a triangular Cu₃ core with each Cu–Cu bond capped by an imidazolylidene group. Each imidazolylidene acts as a bridging ligand in a μ₂ mode and is bonded equally to two Cu(I) ions. The pincer nickel and palladium complexes are square-planar and contain a tridentate NCN ligand. Complexes 3 and 4 are efficient catalyst precursors for Kumada–Corriu and Suzuki–Miyaura coupling reactions of aryl halides with organometallic reagents.     

Trinuclear copper(I) complex of 1,3-bis(2-pyridinylmethyl)imidazolylidene as a carbene-transfer reagent for the preparation of catalytically active nickel(II) and palladium(II) complexes

Reactions of 1,3-bis(pyridin-2-ylmethyl)-1H-imidazol-3-ium hexafluorophosphate, ([HL1](PF₆), L1 = 1,3-bis(pyridin-2-ylmethyl)imidazolylidene) and 1,3-bis(pyridin-2-ylmethyl)-1H-benzimidazol-3-ium hexafluorophosphate ([HL2](PF₆), L2 = 1,3-bis(pyridin-2-ylmethyl)benzoimidazolylidene) with cuprous oxide in acetonitrile readily yielded trinuclear complexes [Cu₃(L1)₃(PF₆)₃] (1) and [Cu₃(L2)₃(PF₆)₃] (2). Treatment of 1 with Ni(PPh₃)₂Cl₂ and Pd(cod)Cl₂ gave [Ni(L1)Cl](PF₆) (3) and [Pd(L1)Cl](PF₆) (4), respectively, due to transmetalation. [Ni(L1)₂](PF₆)₂ (5) was obtained from the reaction of [Cu₃(L1)₃(PF₆)₃] and Raney nickel in acetonitrile. All these complexes have been fully characterized. Both 1 and 2 consist of a triangular Cu₃ core with each Cu–Cu bond capped by an imidazolylidene group. Each imidazolylidene acts as a bridging ligand in a μ₂ mode and is bonded equally to two Cu(I) ions. The pincer nickel and palladium complexes are square-planar and contain a tridentate NCN ligand. Complexes 3 and 4 are efficient catalyst precursors for Kumada–Corriu and Suzuki–Miyaura coupling reactions of aryl halides with organometallic reagents.     

Synthesis of trifluoromethyl-substituted salicylates by cyclocondensation of 1,3-bis(silyloxy)-1,3-butadienes with 4,4-dimethylthio-1,1,1-trifluorobut-3-en-2-one

A formal [3+3] cyclocondensation of 1,3-bis(silyl enol ethers) with the little-known 4,4-dimethylthio-1,1,1-trifluorobut-3-en-2-one was studied. In contrast to 4,4-dimethoxy-1,1,1-trifluorobut-3-en-2-one, this α-oxoketene dithioacetal reacts with 1,3-bis(trimethylsilyloxy)-1,3-butadienes in the presence of TiCl₄ to give mainly 6-methylthio-4-(trifluoromethyl)salicylates via 1,2-addition. The scope and limitations of the reaction are discussed.     

New silicon-containing heterocyclic rings derived from 1, 3-bis(methyldichlorosilyl)propane

Reaction of 1,3-bis(methyldichlorosilyl)propane with alcohols gives (methylalkoxychlorosilyl)propanes. Hydrolysis of the latter with the calculated amount of water in the presence of a HCl acceptor gives 2, 6-dimethyl-2,6-dialkoxy-1-oxa-2,6-disilacyclohexanes. Hydrolysis of 1,3-bis(methyl-dichlorosilyl)propane and 1,3-bis(methylalkoxy-chlorosilyl)propane gives a tricyclic carbocyclosiloxane. A study is made of the reactions of 2, 6-dimethyl-2, 6-dialkoxy-1-oxa-2, 6-disilacyclohexane with alcohols, triethylsilanol, triethylchlorosilane, and C₆H₅MgBr.     

Transformations of phosphazane ligands in the coordination sphere of transition metals. Reactions of phosphinotriazene Ph<Subscript>2</Subscript>P-N(Ph)-N=NPh with Ni<Superscript>0</Superscript> and Ni<Superscript>I</Superscript> complexes

3-(Diphenylphosphino)-1,3-diphenyltriazene Ph₂P-NPh-N=NPh was synthesized. The reactions of this compound with bis(cycloocta-1,5-diene)nickel, (cod)₂Ni, and nickel(I) bis(triphenylphosphino)bis(trimethylsilyl)amide, (Ph₃P)₂Ni-N(SiMe₃)₂, afforded the anionic nickel complex [Ph₄P]⁺[Ni(PhNNNPh)₃]⁻ in 15 and 78% yields, respectively. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1585–1589, July, 2005.     

Recoverable chiral palladium–sulfonated diphosphine catalysts for the asymmetric hydrocarboxylation of vinyl arenes

Water-soluble palladium complexes with sulfonated diphosphines dpppts (1,3-bis[di(m-sodiumsulfonatophenyl)phosphino]propane), dppbts (1,4-bis[di(m-sodiumsulfonatophenyl) phosphino]butane), (S,S)-BDPPTS (2,4-bis[di(m-sodiumsulfonatophenyl)phosphino]butane) and (R,R)-CBDTS (1,2-bis[di(m-sodiumsulfonatophenyl)phosphinomethyl]cyclobutane) are active in the hydrocarboxylation of vinyl arenes without addition of acid. The stability of the catalyst systems increases when the reaction is performed in an acidic medium and the catalysts could be recycled twice with no loss in activity or enantioselectivity in the case of the [Pd(OAc)₂]/BDPPTS system. Enantioselectivities up to 43% are obtained.     

Nickel-catalyzed [4+3] cycloaddition of ethyl cyclopropylideneacetate and 1,3-dienes

The [4+3] cycloaddition of ethyl cyclopropylideneacetate (1) with 1,3-dienes proceeded in the presence of Ni(cod)₂-TOPP (tri-o-biphenylyl phosphite). The reaction provided a new method for the synthesis of cycloheptene derivatives. The mechanism of the reaction was proposed.