Synthesis and properties of 5-(5-nitro-2-furyl)thiazolines

The reactions of 2-amino-4-methyl-5-(5-nitro-2-furyl)thiazole with excess methyl iodide leads to 3,4-dimethyl-2-methylamino-5-(5-nitro-2-furyl)thiazolium iodide, which is converted to 2-imino-3,4-dimethyl-5-(5-nitro-2-furyl)thiazoline under the influence of bases. The iminothiazoline structure was proved by comparison of the spectral characteristics of its acetyl derivative and the isomeric 2-(N-acetyl-N-methyl) amino-4-methyl-5-(5-nitro-2-furyl)thiazole. The pKa values of 2-amino-4-methyl-5-(5-nitro-2-furyl)thiazole and 3,4-dimethyl-2-imino-5-(5-nitro-2-furyl)-thiazoline were determined, and the constant of the aminothiazole-iminothiazoline tautomeric equilibrium was calculated.Translated from Khimiya Geterosiklicheskikh Soedinenii, No. 10, pp. 1337–1340, October, 1985.     

Mannich bases and methiodides of 6-(2-furyl)imidazo[2,1-b]thiazole and its substituted derivatives

The Mannich reaction in a number of 6-(2-furyl)-substituted imidazo[2,1-b]thiazoles is realized initially in the 5 position of the imidazothiazole system, whereas it is also realized in the 5 position of the furan ring in the presence of excess reagents if the latter position is not substituted. Iodomethylation occurs at the N₇ atom of imidazothiazole. The Mannich bases of 6-(5-nitro-2-furyl)imidazo[2,1-b]thiazole are iodomethylated only at the aminomethyl group. The pK_a values of the series of compounds were measured.     

Aminomethylation of 2-(2-furyl)imidazo-[1,2-a]pyridine

The aminomethylation (morpholino- and piperidinomethylation) of 2-(2-furyl)imidazo[1,2-a]-pyridine proceeds primarily at the 3 position of the imidazopyridine system at equimolecular ratios of the reagents, but also proceeds at the 5 position of the furan ring when there is a slight excess of formaldehyde and amine. The structure of the product of monomorpholinomethylation was proved by nitration to give a mononitro derivative that was identical to the 3-morpholinomethyl-2-(5-nitro-2-furyl)imidazo[1,2-a]pyridine prepared by the morpholinomethylation of 2-(5-nitro-2-furyl)imidazo[1,2-a]pyridine. Thin-layer chromatography and IR and UV spectroscopy were used to prove the structures.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 818–821, June, 1971.     

Different specificities in the bromination of 6-(2-furyl)imidazo[2,1-b]thiazole and its derivatives with 1 mole of bromine

The action of 1 mole of bromine on 6-(2′-furyl)imidazo[2,1-b]thiazole, its 2-methyl-, 3-methyl-, and 2,3-dimethyl-substituted derivatives, and their hydrobromides in chloroform and glacial acetic acid was studied. The bromination of bases containing a methyl group in the 3 position leads primarily to the 5′-derivatives with respect to the furan ring in chloroform, whereas in the remaining cases 5-bromo derivatives with respect to the imidazothiazole system are formed. Compounds of the latter type are formed by the action of bromine in glacial acetic acid or of sodium hypobromite in alkaline media on the bases. The hydrobromides are brominated in both acetic acid and chloroform, regardless of the substituents in the thiazole ring, primarily in the 5′ position of the furan ring. The structures of the bromination products were proved by means of alternative syntheses, thin-layer chromatography, and the PMR spectra.     

Synthesis and transformations of 2-(2-furyl)- and 2-[β-(2-furyl)vinyl]imidazo[4,5-f]quinolines

The corresponding 2-(2-furyl)- and 2-[-(2-furyl)vinyl]imida zo[4,5-f]quinolines were obtained by condensation of 5,6-diaminoquinoline and 5-amino-6-rnethylaminoquinoline with furfural, furylacrolein, and their 5-bromo and 5-nitro derivatives and also with the hydrochlorides of imino esters of furancarboxylic and furylacrylic acids. Alkylation, acetylation, nitration, and substitution of the halogen in the furan ring by a nitro group were studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 440–442, April, 1973.     

Synthesis and transformations of 2-(2-furyl)-and 2-[β-(2-furyl)vinyl]imidazo[4,5-b]phenazines

The corresponding 2-(2-furyl)- and 2-[-(2-furyl)vinyl]imidazo[4,5-b]phenazines were obtained by the condensation of 2,3-diaminophenazine with furfural and 2-furylacrolein and with their 5-bromo and 5-nitro derivatives. The phenazines were also synthesized by the reaction of 2-methylimidazo[4,5-b]phenazine with furfural and 5-bromo- and 5-nitrofurfural. The alkylation, acetylation, and nitration of the compounds obtained, as well as replacement of the halogen in the furan ring by a nitro group, were studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1425–1428, October, 1971.     

Synthesis of chiral 2-furyl and 3-nitro-7-oxabicyclo[2.2.1]heptane derivatives from sugars

Asymmetric Diels–Alder reactions between 2-methylfuran and chiral (E)-1,2-dideoxy-1-nitroalkenes derived from d-mannose and d-galactose were carried out at room temperature, under 13 kbar pressure. The processes were completely regioselective, and only the four adducts with penta-O-acetyl-1′-C-(4-methyl-3-nitro-7-oxabicyclo[2.2.1]hept-5-en-2-yl)pentitols structures were formed in each case. These adducts, as well as those arising from cycloadditions of the same nitroalkenes and furan, have been converted into chiral derivatives, such as 2-furyl substituted 1-nitrosugars, 2-glyco-4-methyl-3-nitro-7-oxabicyclo[2.2.1]heptanes, and 5,6-exo-epoxy-2-glyco-3-nitro-7-oxabicyclo[2.2.1]hept-5-enes.     

Synthesis and properties of <Emphasis Type="Italic">trans</Emphasis>-2-[2-(2-hetaryl)vinyl]benzothiazoles

Electrophilic substitution reactions (formylation and acylation) in the series of 2-[2-(2-furyl)vinyl]- and 2-[2-(2-thienyl)vinyl]benzothiazoles leads to the corresponding derivatives at the α-position of the furan or thiophene ring. The presence of a vinylene bridge weakens deshielding effect of the benzothiazole fragment on π-excessive heterocycles, so that such compounds react at a higher rate and under milder conditions as compared to hetarylbenzothiazoles having no vinylene bridge.     

The bromination of 2-amino- and 2-acetylamino-4-(2-furyl)-thiazoles

The bromination of 2-amino-and 2-acetylamino-4-(2-furyl)thiazoles has been studied, and it has been shown that bromination takes place first in the furan ring and then, with an excess of bromine, also in the thiazole ring in position 5.     

Synthesis of 1H-thieno[3,4-c]pyrazoles,thieno[3,4-b]furans,selenolo[3,4-b]furans and pyrrolo[3,4-d]thiazoles

Starting from the readily available aryl 2-methyl-5-phenyl-3-furyl ketones, 5-methyl-1H-1-phenylpyrazole-4-yl ketones and 4-methyl-2-phenyl-5-thiazolylcarboxaldehyde, a series of 2-phenyl-4-arylthieno[3,4-b]-furan, 2-phenyl-4-(p-methoxyphenyl)selenolo[3,4-b]furan, 4-aryl-1H-1-phenylthieno[3,4-c]pyrazole and 5-benzyl-2-phenylpyrrolo[3,4-d]thiazole were prepared in high yield.     

Synthesis and some transformations of 2-(2-furyl)naphtho[1,2-<Emphasis Type="Italic">d</Emphasis>]oxazole

By condensation of 1-amino-2-hydroxynaphthalene with furoyl chloride in 1-methyl-2-pyrrolidone 2-(2-furyl)naphtho[1,2-d]oxazole was synthesized and brought into electrophylic substitution reactions: nitration, bromination, sulfonation, formylation, and acylation. The substituent commonly was introduced into the position 5 of the furan ring, but at the nitration and bromination electrophilic attack was directed both at the furan ring and the naphthalene fragment.     

Thiocyanation, Halogenation, Dehalogenation, Transhalogenation, and Nitration of 2-Substituted 4-(2-Furyl)thiazoles

Bromination and thiocyanation of 2-amino- and 2-acetylamino-4-(2-furyl)thiazoles when 1 mol of reagent is used at 10°C are directed to the 5 position. Formation of 5'-bromo-substituted derivatives when the reaction temperature is raised is the result of a secondary, thermodynamically controlled process. Monohalogenation and mononitration of 4-(2-furyl)-2-methylthiazole are directed to the 5' position. Nitration of 2-acetylamino-4-(5-nitro-2-furyl)thiazole by a nitrating mixture is accompanied by oxidative cleavage of the 5-nitrofuran moiety and leads to formation of 5,5'- and 3',5'-dinitro derivatives.     

Synthesis and transformations of 2-(2-furyl)-and 2-[β;-(2-furyl)vinyl]naphth[1,2-d]imidazoles

The corresponding 2-(2-furyl)naphth[1,2-d]imidazoles were obtained by heating Schiff bases, prepared from 1,2-naphthalenediamine and furfural and 5-bromo- and 5-nitrofurfurals, in nitrobenzene. 2-[-(2-Furyl)vinyl]naphth[1,2-d]imidazoles were synthesized by condensation of 2-methylnaphth[1,2-d]imidazole with furfural and 5-bromo- and 5-nitrofurfural. The methylation, nitration, and acetylation of the compounds obtained were studied, and the replacement of the bromine atom in the furan ring by a nitro group was also investigated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1555–1557, November, 1972.     

4-Acetyl-1-(R-benzylidene)-3-(5-nitro-2-furfuryl)thiosemicarbazides — Carriers of synthones for obtaining thiazole and triazole rings

The corresponding thiosemicarbazonium salts, which form 4-acetyl- and 2,4-di-acetyl-1-benzylidene-3-(5-nitro-2-furfuryl)thiosemicarbazides with acetic anhydride, were obtained by the reaction of 5-nitrofurfuryl bromide with 1-benzyl-idenethiosemicarbazides. Under the influence of bases the monoacetylated derivatives undergo cyclization to the corresponding 2-benzylidenehydrazino-5-(5-nitro-2-furyl)thiazoles. Intramolecular cyclization of the monoacetylated products to 3-methyl-5-[(5-nitro-2-furfuryl)thio]-1,2,4-triazole, which is accompanied by the elimination of the corresponding benzaldehyde, occurs in the presence of hydrochloric acid.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 699–704, May, 1988.     

Synthesis and some transformations of new 9-furylnaphtho[2,3-b]furan derivatives

The synthesis of a number of naphtho[2,3-b]furan derivatives, containing a furyl substituent in position 9 by intramolecular cyclization of 2-carboxy and 2-formylbis(5-alkylfur-2-yl)methanes is described. The reactivity of the title compounds in formylation, acetylation, nitration, and oxidation reactions has been investigated. It was shown that nitration of 2-methyl-9-(5-methyl-2-furyl)naphtho[2,3-b]furan-4-yl acetate leads to oxidative furan ring opening rather than to electrophilic substitution.     

2-(2-Furyl)-1(3)H-imidazo[4,5-f]quinoline. Synthesis and electrophilic substitution reactions

2-(2-Furyl)-1(3)H-imidazo[4,5-f]quinoline was synthesized by the Weidenhagen reaction of quinoline-5,6-diamine with furfural. Its alkylation with methyl iodide in the system KOH-DMSO gave two isomeric N-methyl derivatives, 2-(2-furyl)-1-methyl-1H- and 2-(2-furyl)-3-methyl-3H-imidazo[4,5-f]quinolines, the latter prevailing. 2-(2-Furyl)-3-methyl-3H-imidazo[4,5-f]quinoline was brought into electrophilic substitution reactions: bromination, nitration, formylation, acylation, sulfonation. Depending on the reaction conditions, electrophilic attack could be directed at both furan ring and quinoline fragment.     

New Furano-sesquiterpenoids from Mediterranean Sponges

A mixture of sponges of the East Pyrenean Mediterranean is shown to contain the known sponge products longifolin ( 1 ), avarol ((+)- 3 ), and avarone ( 4 ) and the terrestrial-plant product sesquirosefuran ( 2 ), besides to the new furano-sesquiterpenoids tavacfuran (= 3-methyl-2-[(3′Z)-3′-methyl-4″-methyl-2″-furyl-3′-butenyl]furan; ( 5 ) and tavacpallescensin (= 5,10-dihydro-6,9-dimethyl-4H-benzo[5,6]cyclohepta[1,2-b]furan; 6 ) and the new furano-butenolide sesquiterpenoids tavacbutenolide-1 (= (±-4-ethoxy-2-methyl-4-)[(2′E)-2′-methyl-4′-(3″-methyl-2″-furyl)-2′-butenyl]-2-buten-4-olide; (±)- 7 ) and tavacbutenolide-2 (= (±)-4-ethoxy-3-methyl-4-[2′E)-3′-methyl-4′-(4″-methyl-2″-furyl)-2′-butenyl]-2-buten-4-olide; (±)- 8 ). Structural assignments are based on NMR data and on the synthesis of the (E)-isomer of 5 . The sponge Dysidea tupha of the same area is also shown to contain the two sesquiterpenoids ent-furodysinin ((?)- 14 ), which is enantiomeric to a product of a Dysidea sp. of Australian waters, and tuphabutenolide ((+)- 15 ).     

Novel synthesis of benzalacetone analogues of naphth[a]azulenes by intramolecular tropylium ion-mediated furan ring-opening reaction and X-ray investigation of a naphth[1,2-a]azulene derivative

[reaction: see text] Benzalacetone analogues of naphth[1,2-a]azulene (8), naphth[2,1-a]azulene (13), and naphth[2,3-a]azulene (18) were synthesized from 2-(5-methyl-2-furyl)-1-tropylionaphthalene (7), 1-(5-methyl-2-furyl)-2-tropylionaphthalene (12), and 2-(5-methy-2-furyl)-3-tropylionaphthalene (17), respectively. The synthetic method is based on furan ring-opening reaction by the intramolecular electrophilic attack of a tropylium ion. Single-crystal X-ray work on the naphth[1,2-a]azulene derivative (8) revealed that its tetracyclic system exhibited deformation from planarity similar to that of benzo[c]phenanthrene (tetrahelicene). A centrosymmetric associated dimer structure, just like the molecules of carboxylic acids but via C=O...H-C hydrogen bonds, was found in the crystal. Reduction of bond-length alternation in the seven-membered ring was also found.     

Furan compounds

By reductive amination, starting from furfural, 5-methylfurfural, β-(2-furyl)acrolein, and monoethanolamine, we have obtained N-furfurylaminoethanol, N-(5-methyl-2-furfuryl)aminoethanol, and N-[1-(α-furyl)-3-propyl]aminoethanol. By reductive amination combined with the subsequent hydrogenation of the furan ring we have obtained N-tetrahydrofurfurylaminoethanol and N-(5-methyltetrahydro-2-furfuryl)aminoethanol.     

Synthesis and properties of 2-(2-furyl)-1-methyl-1H-acenaphtho[9,10-d]imidazole

2-(2-Furyl)-1-methyl-1H-acenaphtho[9,10-d]imidazole was obtained by the condensation of 9,1-acenaphthenequinone with furfural in the presence of ammonium acetate followed by N-methylation of the obtained 2-(2-furyl)-1H-acenaphtho[9,10-d]imidazole with methyl iodide in N-methylpyrrolid-2-one in the presence of potassium hydroxide. It was established that its electrophilic substitution in an acidic medium only takes place at position 2 of the furan ring while in a neutral medium both position 2 and position 7 of the aromatic part of the molecule undergo electrophilic attack. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 191–196, February, 2006.