Direct preparation of thiazoles, imidazoles, imidazopyridines and thiazolidines from alkenes

A range of heterocycles, namely thiazoles, imidazoles, imidazopyridines, thiazolidines and dimethoxyindoles, have been synthesised directly from alkenes via a two-step ketoidoination/cyclisation protocol. The alkene starting materials are themselves readily accessible using many different and well-established approaches, and allow access to a variety of heterocycles with excellent yields and regioselectivity.     

Direct preparation of allylic indium(III) reagents from allylic alcohols via a reductive transmetalation of pi-allylnickel(II) with indium(I) iodide

InI-mediated direct allylation of carbonyl compounds with allylic alcohols proceeded smoothly with catalytic amounts of Ni(acac)(2) and PPh(3) to give the corresponding homoallylic alcohols in high yields. Allylindium compounds were shown to be the real allylating agents in the present system. Substituted allylic alcohols gave branched homoallylic alcohols with syn-selectivity irrespective of the geometry of the starting allylic alcohols, whereas high anti-selectivity was observed when a bulky substituent is present in the allylic alcohols. The outcome of the diastereoselectivity is discussed on the basis of the reaction mechanism, comparing with the corresponding Pd-catalyzed version. Another distinct behavior between the Ni- and Pd-catalyzed allylation was demonstrated in the reaction of hex-1,5-diene-3,4-diol derivatives: the Pd catalyst did not give any coupling product, whereas the Ni-catalyzed InI-mediated reaction with benzaldehyde afforded the 1:1 and 1:2 adduct diols selectively depending on the reaction conditions.     

Efficient preparation of allylic grignard reagents using slurries of precondensed magnesium

Using a simple apparatus addition of 2-alkenyl halides to precondensed active Mg in THF gave clean solutions of 2-alkenylmagnesium halides which on carbonation furnished β,γ-unsaturated carboxylic acids in high yields.     

The preparation of some trifluoroacetato complexes of zirconium

The preparation of a trifluoroacetato complex of zirconium from trifluoroacetic acid and zirconium oxide dichloride is described - Zr₂(CF₃COO)₅(OH)₃(H₂O)₃. From spectroscopic, and thermal gravimetric analysis, a dimeric structure is proposed. A monomeric zirconium trifluoroacetato complex containing 1,10-phenanthroline is also described - Zr(CF₃COO)₂(C₁₂H₈N₂)(OH)₂.     

电化学合成镍配合物的研究

采用金属镍为“牺牲”阳极，首次在无隔膜电解槽中，电化学溶解金属镍一步 制备了纳米NiO前驱体Ni(Oet)2,Ni(Obu)2,Ni(Oet)2(acac)2，Ni(Obu)2(acac)2 [acac为乙酰丙酮基].产物通过红外光谱（FT-IR）、拉曼光谱（Raman spectrum） 进行表征。同时讨论了影响电合成镍醇盐及其配合物的关键因素。实验表明，防止 阳极钝化，温度控制在30-40℃，采用有机胺溴化物为导电盐，可以提高电合成效 率。     

Polymerization of isoprene initiated by the reaction products of zirconium allylic complexes and titanium chlorides

Reaction of (all)₄Zr with TiCl₄ involves the migration of the allyl ligands to titanium which is accompanied by the reduction of titanium to a tri- and divalent state and the formation of diallyl. The reaction products are found to initiate polymerization and oligomerization of isoprene. The course of the isoprene reactions and the properties of the resulting polymers are determined by the nature of the complexes formed. The reaction products of TiCl₄ or TiCl₃ with (all)₂ZrCl₂ initiate cationic polymerization of isoprene. Complexes resulting from the reaction of TiCl₃ with (all)₄Zr or (all)₃ZrCl lead to cis-1,4-polyisoprene.     

Pentadienyl transfer reagents based on zirconium: preparation and reactions with carbonyl compounds

A variety of 2,4-pentadienylzirconiums were generated by reacting pentadienyl ethers with zirconocene ‘Cp₂Zr’. These complexes underwent a highly γ-regioselective and anti-stereoselective in situ addition with carbonyl compounds to afford bis(homoallylic) alcohols in good yields. The reversal of anti vs syn selectivity was simply achieved with BF₃, thus expanding the synthetic potential of the reaction.     

Asymmetric allylic alkylation of acyclic allylic ethers with organolithium reagents

A highly efficient, regio- and enantioselective Cu(I) /phosphoramidite-catalyzed asymmetric allylic alkylation of allyl ethers with organolithium reagents is reported. The use of organolithium reagents is essential for this catalytic C?C bond formation due to their compatibility with different Lewis acids. The versatility of allylic ethers under the copper-catalyzed reaction conditions with organolithium reagents is demonstrated in the shortest synthesis of (S)-Arundic acid.     

Cross-coupling of alkenyl,aryl or allylic selenides and grignard reagents catalyzed by nickel-phosphine complexes

Alkenyl, aryl or allylic selenides smoothly couple with Grignard reagents in the presence of Ni(II)-phosphine complexes as catalysts to afford the corresponding unsaturated compounds in good yields. The reactivity order of coupling reaction with BuMgBr catalyzed by NiCl₂ [Ph₂PCH₂CH₂CH₂PPh₂] was found to be PhSeMe « PhCl > PhSMe by the competitive reactions.     

Transformation of zirconocene-olefin complexes into zirconocene allyl hydride and their use as dual nucleophilic reagents: reactions with acid chloride and 1,4-diketone

Zirconocene-olefin complexes Cp(2)Zr(H(2)C=CHR), prepared in benzene-THF at 0 degrees C, react with acid chlorides to provide homoallylic alcohols. The key is an equilibrium between the zirconocene-olefin complexes and the corresponding zirconocene allyl hydride complexes via allylic C-H bond cleavage of the coordinating alkenes. Furthermore, the zirconocene-olefin complexes are also available for the reaction with 1,4-diketone to afford anti-1,4-diols with excellent diastereoselectivity. Thus, Cp(2)Zr(H(2)C=CHR) serves as a donor of both hydride and an allylic group. These reactions also proceed efficiently by using zirconocene-olefin complexes, derived from Cp(2)ZrCl(2), Mg metal, and 1-alkenes.     

Copper-catalyzed allylic hydroxyamination and amination of alkenes with Boc-hydroxylamine

Olefins react regioselectively with Boc-NHOH in the presence of Cu(I,II) salts to produce allyl-N(OH)(Boc) derivatives, apparently via the intermediacy of Boc-NO; yields and rates are dramatically improved by the addition of H₂O₂. The corresponding allylamine derivatives, allyl-NH(Boc), are formed selectively from Boc-NHOH/olefin with CuBr/P(OEt)₃.     

Stereoselective intermolecular allylic C-H trifluoroacetoxylation of functionalized alkenes

Pd-catalyzed allylic C-H trifluoroacetoxylation of substituted alkenes was performed using PhI(OCOCF(3))(2) as the oxidant and acyloxy source. Trifluoroacetoxylation of monosubstituted cyclopentenes and cyclohexenes proceeds with excellent regio- and diastereoselectivity. Studies with one of the possible (η(3)-allyl)Pd(II) intermediates suggest that the reaction proceeds via stereoselective formation of Pd(IV) intermediates and subsequent stereo- and regioselective reductive elimination of the product.     

Allylation of epoxides with allylic indium reagents

Allylindium sesquihalide reacts with epoxide to give homoallyl alcohol via a 1,2-shift reaction. In contrast, allylindate gives the ring-opening product without rearrangement.     

Highly regioselective palladium-catalysed oxidative allylic C-H carbonylation of alkenes

Pd-catalysed direct oxidative carbonylation of allylic C-H bonds with carbon monoxide was first described. This new procedure shows that the inherent requirement for a leaving group in the Tsuji-Trost palladium-catalysed allylic carbonylation can be lifted, which provides a new route for accessing more synthetically useful β-enoic acid esters with high regioselectivity.     

Synthesis of enantiomerically pure 1,4-dioxanes from alkenes promoted by organoselenium reagents

An alkene can be converted into two enantiomerically pure diastereomeric selenoethers through a regio- and stereospecific anti addition reaction mediated by N-(phenylseleno)phthalimide in the presence of an enantiomerically pure 1,2-diol. This alkoxyselenylation reaction can be employed as the key step to allow the synthesis of several isomeric tetrasubstituted 1,4-dioxanes in enantiomerically pure form.