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The α‐arylated tetrahydrofurans, commonly found in biologically active molecules, exhibit diverse biological activities and pharmacological effects. The functionalization of 2,3‐dihydrofuran offers a potential route for the synthesis of substituted tetrahydrofurans. Nevertheless, the development of earth‐abundant metal‐catalyzed regioselective hydrofunctionalization of 2,3‐dihydrofuran for the synthesis of substituted tetrahydrofurans remains to be pursued. Herein, we report a cobalt‐catalyzed hydroarylation of 2,3‐dihydrofuran, which serves as the first example of cobalt hydride‐catalyzed alkene hydroarylation. This reaction provides an efficient method for the synthesis of α‐arylated tetrahydrofurans with high reaction efficiency, exclusive α‐arylation selectivity, and remarkable functional group compatibility. [ABSTRACT FROM AUTHOR]

Tetrasubstituted 2,3‐trans‐dihydrofuran and furan are important heterocyclic scaffolds in natural product, bioorganic and medicinal chemistry as well as in material science. The synthesis of both of these heterocycles starting from common and readily available starting materials are challenging. We found that in situ generated deoxybenzoin‐chalcone Michael adducts underwent oxidative annulation upon heating with molecular iodine in DMSO to provide selectively 2,3‐trans‐dihydrofurans at 80 °C and furans at 120 °C. [ABSTRACT FROM AUTHOR]

2,3‐Dihydrofuran (DHF) has recently been gaining significant attention as a comonomer in metathesis polymerization, thanks to its ability to provide the resultant polymer backbones with stimuli‐responsive degradability. In this report, we present living alternating copolymerization of DHF with less reactive endo‐tricyclo[4.2.2.02,5]deca‐3,9‐dienes (TDs) and endo‐oxonorbornenes (oxoNBs). By carefully controlling the reactivity of both the Ru initiators and the monomers, we have achieved outstanding A, B‐alternation (up to 98 %) under near stoichiometric DHF loading conditions. Notably, we have also found that the use of a more sterically hindered Ru initiator helps to attain polymer backbones with higher DHF incorporation and superior A, B‐alternation. While preserving the living characteristics of DHF copolymerization, as evidenced by controlled molecular weights (up to 73.9 kDa), narrow dispersities (down to 1.05), and block copolymer formation, our DHF copolymers could be broken down to a single repeat unit level under acidic conditions. 1H NMR analysis of the model copolymer revealed that after 24 hours of degradation, up to 80 % of the initial polymer was transformed into a single small molecule product, and after purification, up to 66 % of the degradation product was retrieved. This study provides a versatile approach to improve the alternation and degradability of DHF copolymers. [ABSTRACT FROM AUTHOR]

A simple and beneficial strategy for the construction of 2,3‐dihydrofurans from α‐bromochalcones and α‐substituted cyanoketones via Michael addition‐alkylation reaction has been realized. This transformation was well compatible with various α‐bromochalcones and α‐substituted cyanoketones, and the corresponding multifunctionalized 2,3‐dihydrofurans were obtained in up to 98 % yield. A highly diastereoselective variant of the reaction was also developed. Moreover, the reaction could be performed on gram‐scale. [ABSTRACT FROM AUTHOR]

Palladium catalysed C−H activation has been carried out on furanoid glycals to afford highly substituted and conjugated 2,3‐dihydrofuran trienes and then its conversion into highly substituted 2,3‐dihydrobenzofuran was achieved starting from commercially available, inexpensive sugar precursor diacetone‐D‐glucose. Claisen‐Schmidt condensation reaction, Fujiwara‐Moritani cross coupling reaction and 6π electro‐cyclisation reaction were utilized as the key steps in this synthetic route. Diacetone‐D‐glucose was converted into dihydrofuran moiety via Claisen Schmidt condensation which was submitted to Fujiwara‐Moritani C−C coupling reaction to afford 2,3‐O‐isopropylidine‐4,5‐disubstituted 2,3‐dihydrofurans. Excellent yields (up to 97 %) were obtained during C−C coupling step which indeed is an accomplishment. Next, two step chemical route was established for conversion of these substituted and conjugated 2,3‐dihydrofuran triene moieties into corresponding substituted 2,3‐dihydrobenzofuran moiety. [ABSTRACT FROM AUTHOR]

2,3-dihydrofurans were synthesized from carbonyl-ylides via 1,5-electrocyclization reactions with high yields. Dimethyl diazomalonate was reacted with several β-alkoxy and/or β-phenoxy α,β-unsaturated compounds in the presence of Cu(acac)2 as a catalyst. From the reaction of β-methoxy enone with diazo compound, dioxole, and Cα-H insertion products were also obtained as side products along with 2,3-dihydrofuran derivative. When the unsaturated compound has an ester and a ketone group, only one dihydrofuran derivative was formed, which occurred by the 1,5-ring closure of keto-carbonyl ylide. Dihydrofuran derivative from the formation of ester carbonyl ylide in the reactions was not obtained. [ABSTRACT FROM AUTHOR]

The low to intermediate temperature (850–1050 K) auto-ignition characteristics of furan, 2,3-dihydrofurn and tetrahydrofuran have been investigated both experimentally and kinetically. The pressure (18 and 33 bar) and equivalence ratio (0.5, 1.0 and 2.0) effects on the auto-ignition of furan were experimentally examined using a rapid compression machine. Compared with alkylated furans, the ignition delay times of furan show notably insensitivity to equivalence ratio. Comparison on the low to intermediate temperature reactivity of furan, alkylated furans, 2, 3-dihydrofuran, and tetrahydrofuran indicates that saturation degree plays a more dominant role in enhancing reactivity than alkyl substitution. Literature mechanisms were validated against present data. Kinetic analyses revealed the major fuel consuming routes and the causes for the deviation between simulation and experimental results. Furthermore, a modified model of furan, 2, 3-dihydrofuran, and tetrahydrofuran was proposed and validated against the ignition delay times in this study as well as experimental data in literatures. [ABSTRACT FROM AUTHOR]

Dimers of furan, 2,3-dihydrofuran, 2,5-dihydrofuran and tetrahydrofuran were investigated with the use of theoretical methods to determine the interactions that keep the molecules together. The QTAIM and NCI methods confirmed that for furan dimers the C-H⋯O hydrogen bond and stacking interactions can form the dimers with similar energy. For 2,3-dihydrofuran, 2,5-dihydrofuran and tetrahydrofuran, the decisive mechanism of dimer formation is the stacking interaction between the furan rings. [ABSTRACT FROM AUTHOR]

A highly regio-, diastereo- and enantioselective Michael addition-alkylation reaction between α-substituted cyano ketones and ( Z)-bromonitrostyrenes has been realized by using a chiral N, N′-dioxide as organocatalyst. A variety of substrates performed well in this reaction, and the corresponding multifunctionalized chiral 2,3-dihydrofurans were obtained in up to 95 % yield with 95:5 dr and 93 % ee. [ABSTRACT FROM AUTHOR]

A sequential one-pot, two-step reaction for an efficient preparation of 2-(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-carbonyl)-6,6-dimethyl-3-phenyl-3,5,6,7-tetrahydro-2H-benzofuran-4-one derivatives has been described. One-pot reaction of in situ–formed benzopyran-substituted pyridinium ylides with aromatic aldehydes and dimedone gives corresponding 2,3-dihydrofurans in good yields. The structures of all the newly synthesized compounds were confirmed from their analytical and spectral data. [ABSTRACT FROM AUTHOR]

A theoretical study was performed on the 1,3-dipolar cycloaddition between 2,3-dihydrofuran and substituted phenyl azide using Density Functional Theory (DFT) in combination with a 6-311++G(d,p) basis set. The optimum geometries for reactant, transition state and product, as well as the kinetic data, rate constants and reaction constant ( ρ) were investigated to rationalise the substitution effects and reaction rates of the 1,3-dipolar cycloaddition process in various solvents. The DFT calculation and Frontier Molecular Orbital (FMO) theory as well as the atomic Fukui indices show that the electron-withdrawing substituents enhance the reaction constant ( ρ > 0), especially in polar aprotic solvents. Consequently, small changes in the rate constant of the reaction in various solvents and geometric similarity between reactants and transition state structures were suggested as the early transition state mechanism for electron-withdrawing substituents. In addition, the slope of the Hammett plot and susceptibility of the reaction to electron-withdrawing substituents in various solvents confirmed the mechanism. [ABSTRACT FROM AUTHOR]

One pot reaction of various 2-amino-thiadiazoles or thiazoles and 2,3-dihydrofuran under mild condition in presence of CeCl3.7H2O as catalyst transformed the amino group of 2-amino-thiadiazoles or thiazoles into a medicinally important 2-hydroxy pyrrolidine ring system in good to excellent yields. The generality of the reaction was sufficiently investigated and demonstrated. The new reaction path way for this conversion was established by spectroscopic and analytical methods. [ABSTRACT FROM AUTHOR]

Radical cyclizations of conjugated esters and amides with 3-oxopropanenitriles in presence of manganese(III) acetate produced ethyl 4-cyano-2,3-dihydrofuran-3-carboxylates and 4-cyano- 2,3-dihydrofuran-3-carboxamides in good yields. The radical cyclizations of conjugated amides gave 2,3-dihydrofurans in better yields than that of conjugated esters. Moreover, the reactions of thienyl substituted amides and esters with 3-oxopropanenitriles afforded 2,3-dihydrofurans more efficiently than phenyl substituted ones. [ABSTRACT FROM AUTHOR]

Abstract: The conversion of 1,4-butanediol to 2,3-dihydrofuran and tetrahydrofuran over Co–SiO2 and Co,Pd–SiO2 catalysts with 0.09, 0.46, 0.90 and 1.90wt.% Pd have been investigated in a liquid phase. The Co loading was 40wt.%. The catalysts were prepared by mechanochemical techniques and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and temperature-programmed reduction (TPR) methods. The catalysts with 0.46 and 0.90% Pd were the best for the 1,4-butanediol cyclization. Palladium decreases the reduction temperature of cobalt phase by 165–185°C down to 240–260°C optimum concerning the yield of 2,3-dihydrofuran. It was found by XPS method that an optimum in the degree of cobalt reduction for the reaction of 1,4-butanediol cyclization exists in the region 7–12%. The comparison of nominal catalysts composition and XPS data suggests surface enrichment with palladium after reduction. [Copyright &y& Elsevier]

Abstract: A new method for the synthesis of 2,3-dihydrofurans from readily available starting enones and α-nitro carbonyl compounds has been developed. This protocol can provide a novel and effective methodology for the preparation of 2,3-dihydrofurans in a stereoselective fashion. With 1,4-dien-3-ones, 2,3-dihydrofurans and cyclohexenecarboxylates were produced and high chemoselectivity was observed in different solvents. [Copyright &y& Elsevier]

Abstract: 4-Cyano-2,3-dihydrofuran-3-carboxamides were obtained from the oxidative cyclization of 3-oxopropanenitriles with unsaturated amides using manganese(III) acetate. Treatment of 3-oxopropanenitriles with (2E)-3-(5-methyl-2-furyl)acrylamide and (2E)-3-(2-thienyl)acrylamide gave 2-(5-methyl-2-furyl) and 2-(2-thienyl) substituted 4-cyano-2,3-dihydrofuran-3-carboxamides in moderate yields, respectively. However, (2E)-3-(2-furyl)acrylamide and (2E)-3-phenylacrylamide did not produce any product under the same conditions. On the other hand, reaction of a dienamide such as (2E,4E)-5-phenylpenta-2,4-dienamide with 3-oxopropanenitriles gave diastereomeric mixtures of 2-(2-vinylphenyl)-4-cyano-2,3-dihydrofuran-3-carboxamides. Mechanisms are proposed for the formation of all of these compounds. [Copyright &y& Elsevier]

Abstract: The conversion of 1,4-butanediol to 2,3-dihydrofuran in the liquid phase has been studied over novel kaolin-supported Co–Cu catalysts, prepared by means of a simple mechanochemical method. The improvement of the catalytic properties and decrease in the optimum reduction temperature of Co–kaolin catalysts, promoted by copper, has been observed. It was established that a Co:Cu ratio 5:1 is optimum for the specific activity and for the yield in the conversion of 1,4-butanediol to 2,3-dihydrofuran. In the present study, the highest 2,3-dihydrofuran yield (81%) was obtained with the ultrasonically treated catalyst and after reduction pretreatment at 320–350°C. The existence of an optimum reduction temperature for the catalyst pretreatment was established. In agreement with the results, obtained in our previous studies, the high 2,3-dihydrofuran yield is favoured by the coexistance of cobalt both in the metallic and oxidic state. The increased specific activity of copper-containing catalysts could be related to the lowering of the reduction temperature, which leads to a hexagonal metallic cobalt phase formation. The latter is favourable for 2,3-dihydrofuran synthesis. The advantage of mechanochemical preparation of Co–Cu (5:1) catalyst is that the method prevents penetrating of cobalt ions into the support, thus the whole amount of cobalt loaded is available for the catalyst performance. This is one of the probable reasons for higher specific activity of the 2,3-DHF formation over these catalysts. [Copyright &y& Elsevier]

Anhydrous zirconium tetrachloride is found to be an efficient catalyst for the Imino Diels–Alder reactions of N-benzylideneanilines with 3,4-dihydro-2H-pyran and 2,3-dihydrofuran to afford pyrano and furo[3,2-c] quinolines in good yields. [ABSTRACT FROM AUTHOR]

The promoting effect of gold and the influence of the thermal pretreatment of the cobalt/kaolin catalysts on the reducibility, catalytic activity and selectivity has been studied. The catalytic properties were tested in the cyclodehydration of 1,4-butanediol. The gold-promoted catalysts are more selective than their non-promoted analogues. The modification by gold leads to the formation of new cobalt species, being reducible at significantly lower temperatures in comparison to those of the non-promoted catalysts. This effect of gold results not only on the dispersion, but also on the structure of the metallic cobalt phases. [Copyright &y& Elsevier]

The relative stability of 2-hydroxytetrahydrofuran and the tautomeric 4-hydroxybutanal was determined by the semi-empirical AM1 method. It was concluded that the cyclic tautomer predominates in the gas phase at 25°C. Vapor-phase dehydration of 2-hydroxytetrahydrofuran in the presence of porcelain and silica gel L leads to a quantitative yield of 2,3-dihydrofuran. [ABSTRACT FROM AUTHOR]

Abstract: An efficient method was developed for the synthesis of fused dihydroindeno[1,2-b]furans. One-pot three-component reaction of 1,3-indanedione, aromatic aldehyde and pyridinium ylide in the presence of triethylamine under microwave-irradiation in solvent-free conditions afforded dihydroindeno[1,2-b]furans in a diastereoselective manner in excellent yields. [Copyright &y& Elsevier]

The effect of the solvent nature on the process of hydroformylation of 2,3-dihydrofuran in the presence of the phosphine-containing, complex Rh catalyst HRh(CO)(PPh) has been studied. The influence of solvent polarity and basicity on the conversion of 2,3-dihydrofuran has been revealed, and the composition of tetrahydrofuran aldehydes and the selectivity of their formation have been determined. [ABSTRACT FROM AUTHOR]

Abstract: Antimony trichloride efficiently catalyses diastereoselective three-component reaction of urea, aromatic aldehydes and 2,3-dihydrofuran or 3,4-dihydro-2H-pyran leading to 4-arylhexahydrofuro[2,3-d]pyrimidin-2(3H)-ones and 4-arylhexahydro-1H-pyrano[2,3-d]pyrimidin-2(8aH)-ones, respectively in good yield. [ABSTRACT FROM AUTHOR]