AlEt3-promoted eliminative ring-opening of β-hydroxy epoxides: highly stereoselective synthesis of terminal α-hydroxy olefins

AlEt₃-promoted eliminative ring-opening of β-epoxy alcohols leading to α-hydroxy olefins is reported. This eliminative ring-opening reaction is shown to be highly stereoselective, thus providing an alternative asymmetric synthesis for α-hydroxy olefins.     

Osmium tetroxide-promoted catalytic oxidative cleavage of olefins: an organometallic ozonolysis

A mild, organometallic alternative to ozonolysis utilizing oxone and OsO(4) is presented. This is a direct oxidation of olefins via the carbon-carbon cleavage of an osmate ester by the action of oxone. Twenty-four different olefins were converted to their corresponding ketones or carboxylic acids in high yields (>80%). Free alcohols, acetate- and benzyl-protected alcohols, and 1,2-diols were stable under these conditions. This method should be applicable for traditional organic synthesis.     

Syntheses of Carboxylic Acids from 1, 1-Dichloroehylene

Many β-alkyl- and β-arylpropionic acids are readily obtainable by the reaction of secondary or tertiary alcohols, esters of these, or olefins with the inexpensive 1, 1-dichloroethylene in sulfuric acid. The success of the synthesis depends on the bulk and energy of the carbonium ion intermediate formed from the alcohols or olefins. With carbonium ions having one H atom attached to the carbonium C atom, electrophilic substitution of the 1,1-dichloroethylene takes place to a small extent. Dicarboxylic acids and carboxylic acids with higher molecular weights are sometimes formed as a result of side reactions.     

Regioselective hydroformylation of allylic alcohols

A highly regioselective hydroformylation of allylic alcohols is reported toward the synthesis of β-hydroxy-acid and aldehyde products. The selectivity is achieved through the use of a ligand that reversibly binds to alcohols in situ, allowing for a directed hydroformylation to occur. The application to trisubstituted olefins was also demonstrated, which yields a single diastereomer product consistent with a stereospecific addition of CO and hydrogen.     

弱碱作用下从叔醇简便地合成烯烃

用甲磺酸酐和三乙胺作为脱水剂, 发展了一种从叔醇合成烯烃的简便方法, 反应时间短, 温和的条件和高产率使该方法可以快速地从叔醇合成烯烃.     

Synthesis of trifluoro- or difluoromethylated olefins by regio- and stereocontrolled S(N)2' reactions of gem-difluorinated vinyloxiranes

This paper presents a highly stereoselective synthesis of trifluoro- or difluoromethylated olefins via an S(N)2' type fluorination or reductions of gem-difluorinated vinyloxiranes. Their fluorination with HF-Py furnished trifluoromethylated allylic alcohols with exclusive E selectivity. On the other hand, their reduction with DIBAL-H afforded difluoromethylated E-allylic alcohols predominantly, whereas the corresponding Z isomers were formed exclusively by treatment with BH3.THF.     

Consecutive addition esterification and hydrolysis of cyclic olefins catalyzed by multi-SO3H functionalized multi heteropolyanion-based ionic hybrids undersolvent-free conditions

An efficient protocol for the synthesis of cycloalkyl carboxylates and alcohols from cyclic olefins is described. The cyclic olefins were converted to corresponding target molecules under solvent-free conditions catalyzed by two novel multi-SO₃H functionalized multi heteropolyanion-based ionic hybrids through one-pot consecutive addition esterification and hydrolysis reactions. This approach has several advantages, including high yield, simple workup and simple purification.     

Selective hydroformylation–acetalization of various olefins using simple and efficient Rh-phosphinite complex catalyst

A simple and efficient Rh-phosphinite complex catalyst was studied for the selective hydroformylation of various olefins. The influence of various reaction parameters including the effect of temperature, pressure, catalyst loading, time, and solvents was studied. The protocol was also applied for the synthesis of various acetals via tandem hydroformylation–acetalization of olefins in alcohols as solvents. High activity and selectivity for acetal formation was achieved in the absence of co-catalysts with admirable substrate to catalyst mole ratio (TON 2500). The developed protocol works for a wide range of olefins to synthesize corresponding aldehydes and acetals under optimized reaction conditions.     

Synthesis and transformations of metallacycles. 30. Aluminacyclopentanes in the synthesis of secondary and tertiary alcohols

A method for the synthesis of secondary and tertiary alcohols was developed. The method is based on cycloalumination of olefins with trialkylalanes in the presence of Zr-containing catalysts followed by the CuCl-catalyzed in situ reaction of the corresponding aluminacyclopentanes with aldehydes or ketones.     

Efficient synthesis of allylic azides and one-pot regioselective synthesis of 1,4-disubstituted 1,2,3-triazoles from homoallyl alcohols

This protocol is for an expedient and operationally simple synthesis of allylic azides and one-pot synthesis of 1,4-disubstituted 1,2,3-triazoles from homoallyl alcohols. Synthesis of allylic azides involves the palladium-catalyzed hydroazidation of unactivated olefins with migration of double bond. This hydroazidation can be coupled to Cu(I) promoted 1,3-dipolar cycloaddition to afford the corresponding 1,4-disubstituted 1,2,3-triazoles.     

Photoredox-Catalyzed Isomerization of Highly Substituted Allylic Alcohols by C−H Bond Activation

Photoredox-catalyzed isomerization of γ-carbonyl-substituted allylic alcohols to their corresponding carbonyl compounds was achieved for the first time by C−H bond activation. This catalytic redox-neutral process resulted in the synthesis of 1,4-dicarbonyl compounds. Notably, allylic alcohols bearing tetrasubstituted olefins can also be transformed into their corresponding carbonyl compounds. Density functional theory calculations show that the carbonyl group at the γ-position of allylic alcohols are beneficial to the formation of their corresponding allylic alcohol radicals with high vertical electron affinity, which contributes to the completion of the photoredox catalytic cycle.     

Halogen-free processes for organic carbonate synthesis from CO2

Recent progress on the synthesis of organic carbonates by halogen-free processes has been reviewed. With CO₂ as a cheap and non-toxic feedstock, alcohols, epoxides and olefins can convert to abundant organic carbonates, e.g. dialkyl carbonates, five- or six-membered cyclic carbonates and polycarbonates. To avoid environmental pollution and equipment corrosion, new synthesis routes which exclude traditional halogen-containing catalysts and solvents have caused much attention. Effective alternatives mainly include the organic/inorganic bases and metal-complexes catalysts. In addition, novel carriers for the catalysts are being applied in these processes to improve the activity and facilitate the recovery.     

Photoredox‐Catalyzed Isomerization of Highly Substituted Allylic Alcohols by C−H Bond Activation

Photoredox‐catalyzed isomerization of γ‐carbonyl‐substituted allylic alcohols to their corresponding carbonyl compounds was achieved for the first time by C?H bond activation. This catalytic redox‐neutral process resulted in the synthesis of 1,4‐dicarbonyl compounds. Notably, allylic alcohols bearing tetrasubstituted olefins can also be transformed into their corresponding carbonyl compounds. Density functional theory calculations show that the carbonyl group at the γ‐position of allylic alcohols are beneficial to the formation of their corresponding allylic alcohol radicals with high vertical electron affinity, which contributes to the completion of the photoredox catalytic cycle.     

Advances in direct production of value-added chemicals via syngas conversion

Syngas conversion to fuels and chemicals is one of the most challenging subjects in the field of C1 chemistry. It is considered as an attractive alternative non-petroleum-based production route. The direct synthesis of olefins and alcohols as high value-added chemicals from syngas has drawn particular attention due to its process simplicity, low energy consumption and clean utilization of carbon resource, which conforms to the principles of green carbon science. This review describes the recent advances for the direct production of lower olefins and higher alcohols via syngas conversion. Recent progress in the development of new catalyst systems for enhanced catalytic performance is highlighted. We also give recommendations regarding major challenges for further research in syngas conversion to various chemicals.     

F-T合成校正综合动力学模型

考虑了烯烃、醇与酸的再吸附及其非本征效应(烯烃、醇与酸在催化剂孔道中的扩散作用、物理吸附及溶解度效应)对产物分布的影响,推导了基于详细反应机理的亚甲基插入的烷基机理F-T合成校正综合动力学模型.利用文献数据对动力学模型进行了回归,获得了与文献报道结果相一致的动力学参数.由校正动力学模型计算的烷烃、烯烃、醇与酸产物分布及烯烃比、醇烃比及酸烃比与实验数据较好地吻合.动力学计算结果表明,在铁锰催化剂上,烷烃、烯烃、醇与酸生成的反应是平行竞争反应,烯烃、醇与酸在催化剂表面的再吸附及二次反应导致产物分布偏离了ASF分布.动力学研究还表明,相同碳数的醇与酸产物在催化剂表面上再吸附及二次反应的机会比相同碳数的烯烃大.通过比较相同碳数的烯烃、醇与酸的分子体积及沸点,指出了在铁锰催化剂上,低碳数的烯烃、醇与酸的再吸附及二次反应对产物分布影响的非本征效应中,烯烃、醇与酸的扩散阻力不是主导效应.     

Enantioselective Allylic Hydroxylation of ω‐Alkenoic Acids and Esters by P450 BM3 Monooxygenase

Chiral allylic alcohols of ω‐alkenoic acids and derivatives thereof are highly important building blocks for the synthesis of biologically active compounds. The direct enantioselective C? H oxidation of linear terminal olefins offers the shortest route toward these compounds, but known synthetic methods are limited and suffer from low selectivities. Described herein is an enzymatic approach using the P450 BM3 monooxygenase mutant A74G/L188Q, which catalyzes allylic hydroxylation with high to excellent chemo‐ and enantioselectivities providing the desirable secondary alcohols.     

A donor–acceptor complex enables the synthesis of E-olefins from alcohols,amines and carboxylic acids

Olefins are prevalent substrates and functionalities. The synthesis of olefins from readily available starting materials such as alcohols, amines and carboxylic acids is of great significance to address the sustainability concerns in organic synthesis. Metallaphotoredox-catalyzed defunctionalizations were reported to achieve such transformations under mild conditions. However, all these valuable strategies require a transition metal catalyst, a ligand or an expensive photocatalyst, with the challenges of controlling the region- and stereoselectivities remaining. Herein, we present a fundamentally distinct strategy enabled by electron donor–acceptor (EDA) complexes, for the selective synthesis of olefins from these simple and easily available starting materials. The conversions took place via photoactivation of the EDA complexes of the activated substrates with alkali salts, followed by hydrogen atom elimination from in situ generated alkyl radicals. This method is operationally simple and straightforward and free of photocatalysts and transition-metals, and shows high regio- and stereoselectivities.

A visible-light-induced defunctionalization strategy for the synthesis of olefins by using easily available alcohols, amines and carboxylic acids as starting materials is demonstrated.     

Direct Catalytic Olefination of Alcohols with Sulfones

The synthesis of terminal, as well as internal, olefins was achieved by the one‐step olefination of alcohols with sulfones catalyzed by a ruthenium pincer complex. Furthermore, performing the reaction with dimethyl sulfone under mild hydrogen pressure provides a direct route for the replacement of alcohol hydroxy groups by methyl groups in one step.     

Highly enantio- and diastereoselective one-pot synthesis of acyclic epoxy alcohols and allylic epoxy alcohols

In this report, we outline a highly enantio- and diastereoselective one-pot method for the efficient synthesis of synthetically useful acyclic epoxy alcohols and allylic epoxy alcohols. Our method takes advantage of a highly enantioselective C-C bond-forming reaction to set the initial chirality. The resulting allylic zinc alkoxide intermediate is then epoxidized in situ using either dioxygen or TBHP in the presence of a titanium tetraalkoxide. Epoxy alcohols with up to three contiguous stereocenters are formed in one pot with excellent enantio- and diastereoselectivity. In cases where the zinc alkoxide intermediates contain two different allylic olefins, the more electron-rich double bond is chemoselectively epoxidized to afford an allylic epoxy alcohol. This method represents a highly efficient, stereoselective, and chemoselective approach to the synthesis of a wide range of useful epoxy alcohol and allylic epoxy alcohol products that were previously difficult to access.     

Vanadium-catalyzed asymmetric oxidation of alpha-hydroxy esters using molecular oxygen as stoichiometric oxidant

A vanadium-catalyzed method for the oxidative kinetic resolution of alpha-hydroxyesters, using oxygen as the terminal oxidant, is described. The catalyst is generated in situ from vanadium(V) tri-iso-propoxyoxide in combination with a tridentate ligand derived from 3,5-di-tert-butylsalicylaldehyde and (S)-tert-leucinol. The reaction allows for the enantioselective synthesis of both aromatic and aliphatic secondary alcohols, including those containing olefins and alkynes.