Pt-catalyzed cyclization/1,2-migration for the synthesis of indolizines, pyrrolones, and indolizinones

Indolizine, pyrrolone, and indolizinone heterocycles are easily accessed via the Pt(II)-catalyzed cycloisomerization or a tandem cyclization/1,2-migration of pyridine propargylic alcohols and derivatives. This method provides an efficient synthesis of highly functionalized heterocycles from readily available substrates. [reaction: see text]     

Highly efficient synthesis of functionalized indolizines and indolizinones by copper-catalyzed cycloisomerizations of propargylic pyridines

The copper-catalyzed cycloisomerizations of 2-pyridyl-substituted propargylic acetates and its derivatives are described, which offer an efficient route to C-1 oxygenated indolizines with a wide range of substituents under mild reaction conditions. The presented method could be readily applied to the synthesis of indolizinones through a cyclization/1,2-migration of tertiary propargylic alcohols.     

Synthesis of 2(3H)-furanones via electrophilic cyclization

A variety of highly substituted 2(3H)-furanones are readily prepared from 3-alkynoate esters and the corresponding acids via electrophilic cyclization. Successful electrophiles in this process include I2, ICl, and PhSeCl. This highly efficient process proceeds under mild conditions, tolerates various functional groups, and generally provides substituted 2(3H)-furanones in good to excellent yields.     

Carbon dioxide-mediated synthesis of 3(2H)-furanones from diyne alcohols

A novel type of carbon dioxide-mediated reaction of diyne alcohols without any metal catalysts was reported. Carbon dioxide held the key to the success of this reaction, in which 3(2H)-furanones were selectively obtained in moderate to high yields.     

A new convinient synthesis of 3(2H)-furanones

A selective oxidative fission of the heterocyclic nucleus of 5-methyl-2-(acylmethyl)furans or 2-(5-methyl-2-furyl)-1,3-dicarbonyl compounds by m-chloroperbenzoic acid allows the easy synthesis of the 3(2H)-furanone system.     

Carbon dioxide triggered and copper-catalyzed domino reaction: efficient construction of highly substituted 3(2H)-furanones from nitriles and propargylic alcohols

A novel carbon dioxide triggered and copper-catalyzed domino reaction for the efficient synthesis of highly substituted 3(2H)-furanones from readily available nitriles and propargylic alcohols has been developed. Carbon dioxide is a prerequisite for achieving the present catalytic transformation, and one of the oxygen atoms of carbon dioxide is incorporated into the 3(2H)-furanones. Nitriles not only act as the reaction solvent but also as the reactant; copper salts play dual roles of activating both the propargylic alcohols and nitriles.     

A convenient synthesis of 2,2-disubstituted 3(2H)-furanones

2,2-Disubstituted 3(2H)-furanones can be prepared readily by 1,2-addition of organometallic compounds to γ,γ-disubstituted β-bromo-α,β-butenolides followed by treatment of the adducts with acid.     

Reactions of 2(3H)-furanones

This review article presents a systematic overview of approaches and reactivity data for 2(3H)-furanones, published from 1999 until 2018.     

A catalytic asymmetric protocol for the enantioselective synthesis of 3(2H)-furanones

3(2H)-Furanones can be prepared by a catalytic asymmetric protocol from enynones, which, if electron-rich, require only one reagent and involve two reactions in a single operation--a domino process.     

Cycloisomerization of bifunctionalized allenes: synthesis of 3(2H)-furanones in water

A simple protocol for the efficient synthesis of 3(2H)-furanones by cycloisomerization of allenic hydroxyketones is described. This transformation is achieved in water and in the absence of any expensive metal catalysts.     

Direct and stereospecific synthesis of allenes via reduction of propargylic alcohols with Cp2Zr(H)Cl

Allenes can be synthesized via the direct SN2' addition of hydride to propargylic alcohols. Previous examples of this approach, however, have involved harsh reaction conditions and have suffered from incomplete transfer of central chirality to axial chirality. Here we show that Cp2Zr(H)Cl can react with the zinc or magnesium alkoxides of propargylic alcohols to generate allenes in good yield and in high optical purity. Dialkyl-, alkyl-aryl-, and diaryl-allenes are accessible by this method. Furthermore, the reaction can provide silyl-substituted allenes, trisubstituted allenes, and terminal allenes.     

丙炔醇类和丙二烯醇类化合物对映体的气相色谱拆分

使用全甲基-β-环糊精柱(Rt-βDex^TM~cst柱),对5种丙炔醇类和4种丙二烯醇类化合物对映体的气相色谱分离方法进行了研究,结果4种丙炔醇类和4种丙二烯醇类对映体得到分离,分离因子α为1.01～1.04,分离度R一般大于1.5。方法已用于实际不对称合成样品ee值的测定。探讨了对映体在该柱上的拆分机理,认为烷基取代基适当的疏水性和大小是降低非特异性相互作用、形成相对稳定的不对称环糊精包合物,从而成功拆分光学活性异构体的关键。     

A new synthesis of 3(2H)-furanones from acetylenic β-diketones

Thermal cyclization of 1,5-diarylpent-1-yne-3,5-diones led to the formation of 2-benzyliden-5-aryl-3(2H) furanones as well as 2,6-diaryl-4H-pyran-4-ones as minor products. The structure of the furanones was established from their ir, ¹H nmr and mass spectral data. Their reaction with hydrazine hydrate gave pyrazole derivatives.     

A new and facile synthesis of 3(2H)-furanones via carboxylation- decarboxylation sequence

One-pot synthesis of 3(2H)-furanones from α-ethynyl tertiary alcohols and acyl halides has been achieved in the presence of a palladium complex under CO₂ pressure.     

Efficient synthesis of di- and trisubstituted 2-aryloxazoles via ytterbium(III) triflate catalyzed cyclization of tertiary propargylic alcohols with aryl amides

An efficient synthetic method to prepare di- and trisubstituted 2-aryloxazoles based on Yb(OTf)₃ catalyzed cyclization of trisubstituted propargylic alcohols with aryl amides is described. The reaction was accomplished in moderate to excellent product yields and with complete regioselective control. The mechanism is suggested to involve activation of the starting alcohol by the metal catalyst that results in its ionization. Subsequent cyclization of this newly generated carbocationic species with the aryl amide then affords the oxazole. In view of the mild conditions along with the low cost, commercially availability of Yb(OTf)₃ and its high tolerance to air and moisture, the present synthetic approach offers an operationally simplistic and convenient route to this important aromatic heterocycle.     

Novel tunable CuX(2)-mediated cyclization reaction of cyclopropylideneacetic acids and esters for the facile synthesis of 4-halomethyl-2(5H)-furanones and 4-halo-5,6-dihydro-2H-pyran-2-ones

[reaction: see text] A mixture of cyclopropylideneacetic acids (or esters) and CuBr(2) (or CuI/I(2)) in aqueous acetonitrile afforded 4-substituted 2(5H)-furanones or 3,4-substituted 5,6-dihydro-2H-pyran-2-ones in moderate to good yields. The selectivity of the reaction greatly depended on the reaction temperature.     

A highly enantioselective synthesis of 5-(l-menthyloxy )-4-substituted-3-chloro-2(5H )-furanones

In this paper, stereocontrolled tandem Michael addition-elimination reaction of the novel chiral source, 5-(l-menthyloxy)-3,4-dichloro-2(5H)-furanone, with various thiols and amines has been investigated. A series of new enantiomerically pure compounds, 5–(l-menthyloxy)-4-substituted-3-chloro-2(5H)-furanones, were obtained in good yields with d. e. ? 98% under mild conditions.