One-pot Isomerization Research Articles

T-BuOK promoted stereoselective isomerization of allyl aryl ethers

The t-BuOK promoted stereoselective isomerization of allyl aryl ethers has been developed. The reactions proceeded well in methyl tert-butyl ether (MTBE), providing the corresponding products in good to excellent yields (83–96%). Most of the substrates were isomerized predominantly to the Z isomers with excellent stereoselectivities. Gram-scale synthesis was also achieved on a 10 mmol scale. Moreover, the cascade Cannizzaro and isomerization reactions, and the one-pot isomerization and styryl sulfide formation reactions, were also realized, affording a potential synthetic route to access interesting compounds.

Palladium-Catalyzed Oxidative Dehydrosilylation for Contra-Thermodynamic Olefin Isomerization

We report a newly developed, palladium-catalyzed dehydrosilylation of terminal alkylsilanes that combines with chain-walking hydrosilylation to create a one-pot isomerization of internal olefins to terminal olefins. This catalytic dehydrosilylation is one of the few examples of thermal catalytic functionalizations of unactivated alkylsilanes. The reaction involves transmetalation of an alkylsilane, β-hydride elimination, release of the terminal olefin, and reoxidation of the palladium catalyst. A variety of linear internal olefins underwent the overall isomerization to terminal olefins in good yields and in good regioselectivities. Particularly noteworthy, isomerizations occurring over seven carbon units proceeded in yields that are comparable to those of isomerizations occurring over one carbon unit.

Synthesis of 1,6-Hexandiol, Polyurethane Monomer Derivatives via Isomerization Metathesis of Methyl Linolenate

Cross metatheses of tung oil, a nonedible vegetable oil and α-eleostearic acid ((9Z,11E,13E)-octadeca-9,11,13-trienoic acid, ESA) methyl ester (1), obtained from tung oil containing the same highly unsaturated, conjugated double bonds, have been carried out with cis-1,4-diacetoxy-2-butene (2) using Hoveyda-Grubbs (3-HG2) or Grubbs second or third generation catalysts (3-G2 or 3-G3). The reactions followed by Pd/C-catalyzed hydrogenation give methyl 11-acetoxyundecanoate (4) as a polyester raw material, 1,6-diacetoxy-hexane (5) as a precursor of 1,6-hexanediol (6) polyurethane monomer, and heptyl acetate as a fragrance (7) in 53–99% yields after Pd/C-catalyzed hydrogenation. The one-pot isomerization metathesis of α-linolenic acid ((9Z,12Z,15Z)-9,12,15-octadecatrienoic acid, ALA) methyl ester (7) using 2 as cross coupling agent, RuHCl(CO)(PPh3)3 (9) as isomerization, and 3-G2 as a metathesis catalyst followed by Pd/C catalyzed hydrogenation leads also to the formation of 5 and the homologues of 4 and 7 in ...

Nano-Structured Superacidic Sulfated Zirconium Oxide Catalyst: Synthesis, Characterization and Application in One-Pot Isomerization of n-Alkanes Predicting Their Reaction-Kinetics

Nano-Structured Superacidic Sulfated Zirconium Oxide Catalyst: Synthesis, Characterization and Application in One-Pot Isomerization of <i>n</i>-Alkanes Predicting Their Reaction-Kinetics

One-Pot Isomerization of n-Alkanes by Super Acidic Solids: Sulfated Aluminum-Zirconium Binary Oxides

Abstract Super acidic nanostructured sulfated aluminum-zirconium binary oxides in mole ratios of Zr4+: Al3+ as 2:1 (SAZ-1), 1:1 (SAZ-2), 1:2(SAZ-3) and the reference catalyst super acidic sulfated zirconia (SZ) were synthesized by a precipitation method. Firstly, the catalytic performance of these four catalysts was evaluated during the isomerization of n-hexane to 2-methyl pentane and 3-methyl pentane, n-heptane and n-octane to their corresponding branched chain isomers at low temperature and pressure conditions (40°C and 1 atm). SAZ-1 performed the highest active and selective isomerization of n-hexane, n-heptane, and n-octane into their corresponding branched chain isomers. The catalytic activity of the reference catalyst SZ was the lowest among the four synthesized catalysts. TEM analysis applied to SAZ-1 and SZ indicated the presence of particle-bulks having average size of 20 nm; moreover, these materials presented an amorphous nature, having no particular surface morphology. XRD confirmed the amorphous structure of SAZ-1 and SZ as well as indicated their internal phase structure. FTIR generated ideas about different linkages and bond connectivities between atoms and groups in SAZ-1 and SZ. Ammonia-TPD of these two materials confirmed the higher super acidic nature of SAZ-1 and lower super acidic nature of SZ. Catalyst evaluation and characterization allowed to propose a reaction mechanism, elucidating a possible role of Brønsted and Lewis acid sites on the studied reaction-catalyst, being the former active sites the main factor leading to isomerization reaction. AFM and SEM pictures indicated the nature of the surface of the catalysts. Nevertheless, SEM analysis before and after the reaction displayed that catalyst morphology was modified and could influence the activity of the catalyst. The use of SAZ-1 is cost saving as well as energy saving.

One-pot isomerization-cross metathesis-reduction (ICMR) synthesis of lipophilic tetrapeptides.

An efficient, versatile and rapid method toward homologue series of lipophilic tetrapeptide derivatives (herein, the opioid peptides H-TIPP-OH and H-DIPP-OH) is reported. High atom economy and a minimal number of synthetic steps resulted from a one-pot tandem isomerization-cross metathesis-reduction sequence (ICMR), applicable both in solution and solid phase methodology. The broadly applicable synthesis proceeds with short reaction times and simple work-up, as illustrated in this work for alkylated opioid tetrapeptides.

ChemInform Abstract: Domino Alkene‐Isomerization—Claisen Rearrangement Strategy to Substituted Allylsilanes.

A one-pot isomerization–Claisen protocol has been developed for the synthesis of highly substituted allylsilanes. Monosilylated divinyl ethers can be isomerized using a cationic iridium(I) catalyst followed by a thermal Claisen rearrangement to provide the allylsilanes in excellent yields and diastereoselectivities.

Total synthesis of gelsemoxonine

The first total synthesis of gelsemoxonine has been accomplished. A divinylcyclopropane–cycloheptadiene rearrangement of the highly functionalized substrate successfully assembled the spiro-quaternary carbon center connected to the bicyclic seven-membered core structure. A one-pot isomerization reaction of the α,β-unsaturated aldehyde to the saturated ester via a trimethylsilyl cyanide–diazabicycloundecene (TMSCN–DBU) reagent combination allowed a facile and diastereoselective introduction of the latent nitrogen functionality in the unique azetidine moiety.

One-pot isomerization of aldo-disaccharides to keto-disaccharides in deep sea water under sub-critical conditions

A novel and facile one-pot isomerization of aldo-disaccharides to keto-disaccharides is achieved by making use of deep sea water in sub-critical conditions. The resulting keto-disaccharides having pharmaceutical and food applications were obtained in modest yields of about 30–32% at the optimum reaction conditions (temperature: 180°C, reaction time: 5min). Detailed investigation of all major ions in deep sea water revealed that bicarbonate ions play a key role as a catalyst in this isomerization reaction.

Facile isomerization of silyl enol ethers catalyzed by triflic imide and its application to one-pot isomerization–(2 + 2) cycloaddition

A triflic imide (Tf2NH) catalyzed isomerization of kinetically favourable silyl enol ethers into thermodynamically stable ones was developed. We also demonstrated a one-pot catalytic reaction consisting of (2 + 2) cycloaddition and isomerization. In the reaction sequence, Tf2NH catalyzes both of the reactions.

Domino Alkene-Isomerization–Claisen Rearrangement Strategy to Substituted Allylsilanes

A one-pot isomerization-Claisen protocol has been developed for the synthesis of highly substituted allylsilanes. Monosilylated divinyl ethers can be isomerized using a cationic iridium(I) catalyst followed by a thermal Claisen rearrangement to provide the allylsilanes in excellent yields and diastereoselectivities.

Total Synthesis of Gelsemoxonine

The first total synthesis of gelsemoxonine (1) has been accomplished. Divinylcyclopropane-cycloheptadiene rearrangement of the highly functionalized substrate was successfully applied to assemble the spiro-quaternary carbon center connected to the bicyclic seven-membered core structure. A one-pot isomerization reaction of the α,β-unsaturated aldehyde to the saturated ester via the TMSCN-DBU reagent combination allowed a facile diastereoselective introduction of the latent nitrogen functionality of the unique azetidine moiety.

Meerwein–Ponndorf–Verley reduction of aldehydes formed in situ from α- and β-pinene epoxides in a supercritical fluid in the presence of alumina

The use of a system consisting of flow-type reactor, supercritical fluid containing isopropanol/CO2 and alumina as a catalyst allows the one-pot isomerization of α- and β-pinene epoxides into campholenic aldehyde and myrtanal and Meerwein–Ponndorf–Verley reduction of these aldehydes to the corresponding alcohols.

Phosphine-catalyzed one-pot isomerization of 3-alkynoates and [2 + 3]-cycloaddition with imines: formal synthesis of Securinega alkaloid (±)-allosecurinine

Trimethylphosphine-induced isomerization and cycloaddition of 3-alkynoates with imines for the synthesis of 2,5-syn di-substituted pyrrolines were described. In addition, the utility of this protocol was demonstrated in the efficient formal synthesis of the Securinegaalkaloid ‘allosecurinine’.

Unusual regioselectivity in Pd(0)-catalyzed coupling of allylic monoacetates and nitroalkanes: one-pot isomerization–alkylation

A hitherto unknown palladium-catalyzed reaction of nitroalkanes with hydroxy allylic acetates is reported. The reaction led to the formation of γ-nitrocarbonyl compounds instead of the usual unsaturated nitroalcohol expected upon displacement of the allylic acetate group.

Highly enantio-, regio- and diastereo-selective one-pot [2 + 3]-cycloaddition reaction via isomerization of 3-butynoates to allenoates,

Phosphine-catalyzed one-pot isomerization and [2 + 3]-cycloaddition of 3-butynoates with electron-deficient olefins affords highly functionalized cyclopentenes with both good yields and excellent selectivities of up to 99%.

Silica Chloride-Catalyzed One-Pot Isomerization - Chlorination, Arylation, and Etherification of Baylis - Hillman Adducts

A convenient and efficient one-pot isomerization–chlorination, arylation, and etherification of several Baylis–Hillman adducts with silica chloride, an eco-friendly heterogeneous catalyst, silica chloride–arenes, and silica chloride–saturated and unsaturated alcohols as reagent systems are reported. These reactions furnished highly functionalized isomerized Baylis–Hillman derivatives in good yield. The efficiency and necessity of silica chloride catalyst was compared with thionyl chloride. A plausible mechanism of the reaction is proposed.

A One-Pot Isomerization−Arylation of 2,3-Epoxycyclohexanone under Controlled Microwave Heating

A fast one-pot method has been developed for the direct preparation of 3-aryl-1,2-cyclohexanediones from 2,3-epoxycyclohexanone via a microwave-assisted tandem epoxy ketone isomerization-Heck arylation reaction. The preparative microwave-assisted reactions were performed preferentially in 50% aqueous poly(ethylene glycol) utilizing sodium acetate as the base. Within 5-30 min of directed microwave heating, employing less than 0.05 mol % of palladium acetate and no phosphine ligand, up to 72% yield of C3-arylated diketones was isolated in an overall environmentally benign process. On the basis of the chemical reactivity of proposed intermediates, a reaction pathway is proposed where the acetate base promotes the rearrangement of the 2,3-epoxycyclohexanone into the active mono-enol form of 1,2-cyclohexanedione. An alternative classically heated procedure for isomerization-C3-arylation of 2,3-epoxycyclohexanone in DMF is also reported.