Simple route to 3-(2-indolyl)-1-propanones via a furan recyclization reaction

A simple route to 1-R-3-(2-indolyl)-1-propanones has been elaborated based on recyclization of 2-(2-aminobenzyl)furan derivatives. Being a modification of the Reissert indole synthesis, our approach employs the furan ring as a source of carbonyl function. This approach is general and allows varying of substituents in aromatic ring as well as in 3-position of indole nucleus.     

Furan as a 1,3-diketone equivalent: the second type furan recyclization applied to indole synthesis

A new approach for the synthesis of indole derivatives based on protolytic recyclization of 2-alkyl-5-(2-tosylaminoaryl)-furans is described. The furan ring in this unusual transformation formally serves as a 1,3-diketone equivalent.     

Furan ring opening—indole ring closure: pseudooxidative furan ring opening in the synthesis of indoles

A new approach to the synthesis of 4-(2-indolyl)-3-buten-2-ones is described based on condensation of 2-tosylaminobenzyl alcohols with N-tosylfurfurylamine. Pseudooxidative furan ring opening occurred via protolytic elimination of tosylamide from the side chain of the 2-tosylaminoaryl(5-tosylaminomethylfur-2-yl)methanes formed in situ.     

Efficient and mild synthesis of highly substituted 2,5-dihydrofuran and furan derivatives via stepwise reaction

An efficient and mild synthesis of highly substituted 2,5-dihydrofuran and furan derivatives from a variety of alkylidene malonates and 1,4-butyne-diol via one-pot reaction was applied. With various conditions of base amount, temperature and time applied to the reaction, the 2,5-dihydrofuran and the furan derivatives could be selectively obtained. Moreover, the formation of furan derivatives with 2,5-dihydrofuran derivatives as intermediates was also investigated. Some of these 2,5-dihydrofuran derivatives showed potent in vitro anti-tumor activities against HeLa cells.     

The effect of an N-substituent on the recyclization of (2-aminoaryl)bis(5-tert-butyl-2-furyl)methanes: synthesis of 3-furylindoles and triketoindoles

The recyclization of (2-aminophenyl)bis(5-tert-butyl-2-furyl)methane derivatives has been studied. It was shown that the acid-catalyzed recyclization of N-tosylamides leads to the formation of 2-(3-oxoalkyl)-3-(2-furyl)indoles. In contrast, under the same reaction conditions, acetamides are transformed into indoles containing three keto groups. The acid-catalyzed removal of the acetyl group from these substrates facilitated protolytic furan ring opening. The same triketones can be directly obtained from (2-aminoaryl)bis(5-tert-butyl-2-furyl)methanes.     

Highly efficient synthesis of 4-trifluoromethylfuran derivatives via a sequential deprotection-annulation reaction

(E)-O-protected-2-trifluoromethyl-1-bromo-1-substituted allylic alcohol reacted with terminal alkynes under Sonogashira reaction condition to give the corresponding (E)-2-en-4-ynoic alcohol derivatives, which was further converted to the corresponding 4-trifluoromethylfuran derivatives via a sequential deprotection-annulation reaction in moderate to excellent yields.     

An efficient synthesis of 2-(guaiazulen-1-yl)furan derivatives via intramolecular Wittig reactions

An efficient and mild synthesis of 2-(guaiazulen-1-yl)furans,starting from easily accessible 1-(3-aryl-2-cyanopropenoyl) guaiazulenes,tributylphosphine and acyl chlorides,is described.The strategy employs the intramolecular Wittig protocol as a key step to append the crticial furan ring,leading to the highly functional furans in good yields.     

Arylation of furan derivatives via the Meerwein reaction

Meerwein arylation of 2-arylfurans and 2-furylnitroethylene gave 2,5-diarylfurans and 5-aryl-2-furylnitroethylenes. Meerwein arylation of 2-acylfurans gives 2,5-diarylfurans and substituted azobenzenes in addition to 2-acyl-5-arylfurans.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 452–456, April, 1975.The authors thank N. P. Solov'eva, O. S. Anisimova, and A. I. Ermakov for recording the PMR and mass spectra and for the interest they displayed with respect to the present research.     

Diastereoselectivity in the Paternò-Büchi reaction on furan derivatives

The reaction of benzoin, 4,4^′-dimethoxybenzoin and benzoin ethyl ether with furan gave the corresponding adduct with high diastereoselectivity (71-100%). The diastereoselectivity was explained considering the relative stability of the biradical intermediates. Benzofuran reacts with (S)-1-methylpropylbenzoylformate to give the corresponding adduct with de = 58%. The diastereoselectivity was explained considering the relative stability of the biradical intermediates.     

2-异丙基-1,3-二氢-4(1H)异喹啉酮及其衍生物的合成

异喹啉酮类化合物具有重要药理活性,本文在合成1,2,3,4-四氢-2-苄基异喹啉酮-4衍生物的基础上,参照Hinton方法制备2-异丙基-1,3-二氢-4(1H)异喹啉酮(1),用(1)进一步与芳醛、羟胺、酰氯及苯肼反应得到了相应的衍生物(3_a-6_e)。     

Enantiocontrolled construction of tricyclic furan derivatives via an asymmetric Diels-Alder reaction

[structure in text] The two enantiomers of trycyclic furan derivatives were prepared respectively from Diels-Alder reactions of oxycyclic dienes 3a and 3b, followed by degradation of the 2-(benzyloxy)ethyl group. Compounds 3a and 3b can be selectively synthesized by [3+2]-cycloaddition of vinylpropargyltungsten complex with (2S)-(benzyloxy)-propanal.     

Facile synthesis of 3-substituted thieno[3,2-b]furan derivatives

A facile synthesis of dimethyl 3-hydroxythieno[3,2-b]furan-2,5-dicarboxylate is reported from the available methyl thioglycolate and dimethyl acetylenedicarboxylate starting materials. This compound represents an efficient precursor for the synthesis of 3-substituted thieno[3,2-b]furan derivatives.     

Enantiomeric separation of furan derivatives and fused polycycles by cyclodextrin-modified micellar capillary electrophoresis

The enantiomeric separations of highly hydrophobic furan derivatives and polycycles were performed and optimized using CD-modified micellar CE. The most effective chiral selector for the enantiomeric separation of these analytes was hydroxypropyl-gamma-CD. The effects of CD and SDS concentration and organic modifier were examined in order to optimize the separation conditions. The ratio of CD to surfactant concentration affected the enantiomeric separation significantly, with increases in the derivatized CD concentration generally enhancing resolution. Addition of an organic solvent modifier to the run buffer served to increase the analytes' solubility and enhance the separation efficiency. A highly acidic pH was necessary to effectively suppress the EOF when operating in the reverse polarity mode.     

Base-controlled selective construction of polysubstituted dihydrofuran and furan derivatives through an I2-mediated cyclization

A base-controlled formal [3 + 2] cycloaddition of 1,3-dicarbonyl compounds to enones via an I₂-mediated cyclization was reported. Highly functionalized dihydrofurans and furans were selectively obtained under I₂/DMAP and I₂/DBU conditions in the cyclization step, respectively.     

Furan ring opening-isochromene ring closure: a new approach to isochromene ring synthesis

A new approach toward the synthesis of 1H-isochromenes based on the recyclization of the furan ring in the corresponding ortho-hydroxymethylbenzylfurans is described.     

Sodium borohydride or potassium carbonate-mediated intramolecular Michael addition: a general method for the synthesis of fused dihydrofuran and furan derivatives

A simple and convenient method for the synthesis of fused dihydrofuran derivatives using NaBH₄-mediated reductive cyclization and fused furan derivatives by K₂CO₃-mediated intramolecular Michael addition followed by acid-catalyzed methanol elimination has been developed.     

Ab Initio studies on the rotational equilibria of 2-substituted furan and thiophene carbonyl derivatives

Summary The relative stabilities of syn- and anti-isomers of 2-substituted furan and thiophene carbonyl derivatives are investigated by theab initio MO method. The energy differences between the rotamers are 1–3 kcal mol^–1 but the barriers to rotation are ca. 10 kcal mol^–1 so that free rotational mode is predicted to be a rather difficult process. Application of the self-consistent reaction field (SCRF) method to account for the solvent effect indicates that the isomer with a higher dipole moment (syn) is favored in solution. An electron withdrawing 2-substituent favors syn-isomers for furan carbonyls in contrast to thiophene carbonyls for which anti-isomers are favored. These trends are ascribable to a decrease in electrostatic repulsive and attractive interactions, respectively, in the syn forms of furan and thiophene carbonyls. Contribution of non-bonded repulsive interaction in the anti-isomer is important for the relative stability of the syn-isomer of furan carbonyl derivative. Solvent effects due to higher dielectric continuum are small on the absolute values of energy differences but can reverse the order of stability of the two isomers due to a greater stability acquired by an isomer (syn) with higher dipole moment in solution. The major factor determining stability, or instability, of syn-isomer is a repulsive electrostatic interaction between the two oxygen atoms for furan carbonyls and an attractive electrostatic interaction between the sulfur and oxygen atoms for thiophene carbonyls.     

Novel formation of a bridged bicyclic furan by rearrangement of a tetrahydroxydecalinone

In the course of a synthetic approach to the arisugacins, we prepared the tetrahydroxydecalinone 8a (which exists as the hydroxytetrahydrofuran 8b) by a straightforward route from hydroxy-β-ionone. On treatment with mesyl chloride and base, the desired mesylate 9 was not formed but rather 8ab underwent a novel rearrangement to produce the bridged bicyclic furan 10 in excellent yield. A reasonable mechanism for the rearrangement is presented involving a retro-aldol reaction, a base-catalyzed β-elimination, and final furan formation from a β-hydroxymethyl enone.