Naturally occurring sesquiterpene-coumarin ethers,VI. New sesquiterpene-isofraxidin ethers fromAchillea depressa

The roots ofAchillea depressa afforded in addition to known sesquiterpene-isofraxidine ethers three new derivatives: the bicyclic drimenol derived albartol and the monocyclic derivatives deparnol and acetyldeparnol. The compounds were characterized by¹H-NMR, MS, UV, IR, and CD data.Herrn Prof. Dr.U. Schmidt mit den besten Wünschen zum 60. Geburtstag gewidmet.     

Periphery-modified crown ethers. Synthesis of bis-5,8-dimethoxy-1,4-methanonaphthalene-fused crown ethers

The easily accessible and multi-functionalized 5,8-dimethoxy-6,7-dihydroxy methyl-1,4-dihydro-1,4-methanonaphthalene (1) has been utilized as the basic building material to synthesize the symmetric bis-methanonaphthalene-fused crown ethers 14a-d (BMN-16-crown-4, BMN-22-crown-6, BMN-28-crown-8, and BMN-34-crown-10), that are constructed based on the connection between the α,β-bis-benzylic carbon atoms of diol 1 and oligoethylene glycols (9a-d) via two synthetic routes keyed upon the method of Williamson ether synthesis.     

Phosphonyl radical addition to enol ethers. The stereoselective synthesis of cyclic ethers

Addition of diethyl phosphite or diethyl thiophosphite to enol ethers, in the presence of a radical initiator, results in the regioselective synthesis of organophosphonate or phosphonothioate derivatives, respectively, under mild conditions. This method can be applied to the stereoselective formation of substituted tetrahydrofurans and tetrahydropyrans, on cyclisation of vinyl ethers bearing unsaturated side chains.     

Methods for the interconversion of protective groups. Transformation of mem ethers into isopropylthiomethyl ethers or cyanomethyl ethers

This letter describes methods for the synthesis of isopropylthiomethyl and cyanomethyl ethers from the corresponding MEM ethers and also a process for the cleavage of MEM or MOM ethers of 1,2- and 1,3-diols which avoids cyclization to formals.     

Antiulcer agents. 2. Pyridyl oxime ethers

A large number of pyridinecarboxaldehyde (and ketone) O-substituted oximes were prepared by alkylating the oxime or by treating the parent aldehyde (or ketone) with an O-substituted hydroxylamine. Many of these were converted to the N-oxide. Screening revealed that many of these oxime ethers were active in preventing gastric ulcers in rats. Data on selected examples is given.     

Photoresponsive crown ethers. 10. Metal complexation by light-switched crown ethers immobilized in polymer matrices

The crosslinked polystyrene beads which immobilized two terminal azophenoxide groups of an azobenzene-crown(24-crown-8)-azobenzene unit were synthesized. The polymer beads adsorbed Cs⁺ in the dark while they rapidly released Cs⁺ into the solution under UV-light irradiation, and the photoresponsive complexation occurred reversibly. On the other hand, the crosslinked polystyrene beads which immobilized one terminal azophenoxide group of an azobenzene-crown (24-crown-8) unit scarcely (or only to a smaller extent) exhibited such a photoresponsive behavior. Similarly, the polymer beads which immobilized two terminal azophenoxide groups of an azobenzene-crown (18-crown-6) azobenzene unit reversibly adsorbed and desorbed K⁺ in response to UV-light irradiation. The novel photoresponsive behavior is ascribed to a conformational distortion of the crown rings which induced by the photoisomerization of the azobenzene moiety, although the photoinduced polarity change of the polymer beads is not completely ruled out. The results suggest that the polymer support is useful as a “fixed point” to enforce the conformational changes of immobilized functional molecules.     

Chemistry of crown ethers. Synthesis of new crown ethers containing a pyridazine ring

A method for preparation of crown ethers containing a pyridazine ring based on 1,2-dihydro-3,6-dioxopyridazine was developed.     

Macroheterocycles. 27. Amidomethylation of benzo-crown ethers

The synthesis of some novel benzo-crown ethers by -amidomethylation is described.For Communication 26, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1039–1042, August, 1987.     

Synthesis of macroheterocyclic analogs of dibenzocrown ethers. 5. 16- and 17-Membered oxaazacrown ethers

Macrocyclic diamides are synthesized by condensation of 1,5-bis(2-aminophenyl)-1,5-dioxapentane and 1,6-bis(2-aminophenyl)-1,6-dioxahexane with the dichlorides of glutaric, diglycolic, thiodiglycolic, and N-tosyliminodiacetic acids under high dilution conditions. Reduction with diborane gives the 16- and 17-membered dibenzodiazacrown ethers. The structure of the compounds synthesized is confirmed by IR,NMR (¹H and ¹³C), and mass spectral data.For Communication 4, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 691–696, May, 1990.     

Synthesis of novel crown ethers. Part 1. Coumestan and coumestan analog derivatives of crown ethers

The presented ethylenedioxy compounds5a,5d,6a and6c are examples of novel cyclic ethers, while macrocyclic polyethers represent new crown ether analogues. New coumestan-crowns5a-f, derivatives of 6,7-dihydroxy-3,4-dihydro-2H-dibenzofuran-1-one and 6,7-dihydroxy-3,3-dimethyl-3,4-dihydro-2H-dibenzofuran-1-one6a-e were synthesized from the correspondingo-dihydroxy compounds3a-b,4a-b and ditosylates or dichlorides of di- or triethylene glycol in the presence of K₂CO₃, in DMF/H₂O (15/1) solutions at 65–75 °C for 35 hours. The structure of the macrocyclic ethers obtained were confirmed by¹H-NMR,¹³C-NMR, IR spectra and elemental analyses.Presented at the Sixth International Seminar on Inclusion Compounds, Istanbul, Turkey, 27–31 August, 1995.     

Macroheterocycles. 32. Homolytic dehydrodimerization of crown ethers

The corresponding bis(crown ethers), as well as phenyl- and hydroxy-substituted crown ethers, were obtained by homolytic dehydrodimerization of 12-crown-4, 15-crown-5, and 18-crown-6 in benzene or water.See [1] for Communication 31.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1179–1182, September, 1987.     

Reaction of enol ethers with zinc carbenoid reagents. Cyclopropanation and subsequent isomerization to allylic ethers

The reactions of enol ethers (ROCC, R = alkyl, silyl) with zinc carbenoid reagents were found to give allylic ethers in several cases along with the expected cyclopropyl ethers. The ratio of these two products was highly dependent on the concentration of the reaction mixture. Thus, the selective formation of each product was conveniently attained by merely changing the amounts of the solvent used. Zinc iodide, a by-product of the reaction, plays a key role in the present cyclopropyl to allylic rearrangement. Ring-opened ionic intermediates are proposed.     

Haloacetylated enol ethers. 2. Synthesis of 5-trifluoromethylpyrazoles

1-Methyl-5-(trifluoromethyl)-1H-pyrazoles 2, 3 and 4,5-dihydro-1-phenyl-5-(trifluoromethyl)-1H-pyrazol-5-ol 4 were prepared by reaction of 4-alkoxy-1,1,1-trifluoro-3-alken-2-ones 1 and hydrazine, methylhydrazine, and phenylhydrazine, respectively, in good yields. Compound 1 proved to be a versatile building block for the regiospecific construction of pyrazole rings having an 5-trifluoromethyl substituent.     

Fluorinative ring-expansion of cyclic ethers using p-iodotoluene difluoride. Stereoselective synthesis of fluoro cyclic ethers

Fluorinated five- to seven-membered cyclic ethers were stereoselectively synthesized from four- to six-membered cyclic ethers having an iodoalkyl substituent by fluorinative ring-expansion reaction using p-iodotoluene difluoride.     

Pefluoroaralkyl ethers

Some perfluorinated ethers have been prepared containing both alkyl and aryl groups and either one or two oxygen atoms.Pentafluorophenylmagnesium bromide, with octafluoroadipoyl chloride, perfluoro-oxydiacetyl chloride and perfluoro-oxydipropionyl chloride, gave the corresponding diketones which, upon treatment with sulphur tetrafluoride, afforded perfluoro-1,6-diphenylhexane, perfluoro-bis(2-phenylethyl)ether and perfluoro-bis(3-phenylpropyl)ether, respectively.Pentafluorophenylmagnesium bromide with perfluoro-2-methyl-3-oxanonanedioyl fluoride (prepared from octafluoroadipoyl fluoride and hexafluoropropene oxide) gave a diketone which was treated with sulphur tetrafluoride to give perfluoro-2-methyl-1,9-diphenyl-3-oxanonane.Reactions between octafluoroadipoyl chloride and pentafluorophenol, nonafluoro-4-hydroxybiphenyl and perfluoro-3-hydroxy-4,4′-dimethylbiphenyl gave the corresponding diester which were then each treated with sulphur tetrafluoride and hydrogen fluoride. The first two diesters gave perfluoro-1,6-diphenoxyhexane and perfluoro-1,6-bis(4-phenylphenoxy)hexane, but the corresponding diether was not isolated from the third diester.The effect of structure upon the liquid ranges of the ethers is discussed.