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.     

Fragmentation of trimethylsilyl derivatives of 2-alkoxyphenols: A further violation of the ‘even-electron rule’

The mass spectra of trimethylsilyl (TMS) ethers of 2-methoxyphenols show abundant [M–30]⁺˙ ions originating from consecutive loss of two methyl radicals. This is illustrated by comparison of the accurate mass-measured and linked-scan spectra of the TMS derivatives of 2-methoxyphenol (guaiacol), 4-hydroxy-3-methoxybenzaldehyde (vanillin) and 3-(4-hydroxy-3-methoxyphenyl)-2-propenoic acid methyl ester (ferulic acid methyl ester) with those of the TMS derivatives of phenol, 4-hydroxybenzaldehyde, 3-(4-hydroxyphenyl)-2-propenoic acid methyl ester (p-coumaric acid methyl ester), 3-methoxyphenol and 4-methoxyphenol. This distinctive ortho effect is valuable in the identification of isomeric phenolic compounds. In the spectra of the TMS derivatives of 2-ethoxyphenol and 2-propoxyphenol the sequential loss of two radicals is less pronounced, because elimination of the side-chain and a methyl group with rearrangement and hydrogen migration is competitive.     

Synthesis of α,ω‐Bis(oxazolidinone)polyoxyethylene via a Lithium Bromide–Catalyzed Reaction of Oligoethylene Glycol Diglycidyl Ethers with Isocyanates

The synthesis of bis(oxazolidinone)polyoxyethylene derivatives 2a–h from oligoethylene glycols diglycidyl ethers 1a–e and isocyanates is reported. The reaction was achieved by lithium bromide and tributylphosphine oxide. These bis‐oxazolidinones may have important antibacterial activity.     

Synthesis and complex-forming properties of crown ethers incorporating glucuronic acid moieties

Crown ethers1 and4 of the 18-crown-6 type containing two glucose units have been oxidised by KMnO₄ into mono- and dicarboxylic acid derivatives (5 and11), and derivatives with different lipophilicities of the above crown ethers, namely the acetyl, benzyl and butyl derivatives (8–10, 13, 14) and methyl esters (6 and12) have been synthesizedThe association constants (K _a) with Li, Na, K and NH₄ cations measured in CHCl₃ indicate that complexing ability increases on introduction of carboxy groups, and selectivity changes in favour of the Na cation. These compounds were able to transport alkyl-ammonium salts through a CHCl₃ liquid membrane, displaying, however, no chiral recognition ability.     

Chemical Ionization Mass Spectrometry of Steroids

Abstract

The chemical ionization mass spectra of a group of commonly occuring steroids are discussed. Intense signals (base peak) are observed in the molecular ion region for hydrocarbons and ketones. Functional group elimination is observed with sterols and especially their methyl and TMSi ethers, with the result that base peaks for these compounds are found at m/e values well below the expected molecular ion region. These observations are compared with those from the corresponding electron impact spectra.     

Use of Dimethylsilyl Ethers for Characterizing Primary Aliphatic Alcohols: A comparison of mass spectrometric fragmentation of di- and trimethylsilyl derivatives

Mass spectral fragmentation patterns of dimethylsilyl (DMS) ethers of primary unbranched, branched, and secondary unbranched aliphatic alcohols in the C₅ to C₁₀ range are compared with those of the corresponding trimethylsilyl (TMS) derivatives. Unlike their TMS analogues, DMS ethers of primary alcohols exhibit pronounced rupture of the C? C bond adjacent to the oxygen atom within the alkyl moiety (loss of an alkyl radical R) in marked preference to cleavage within the silyl substituent (loss of CH₃). Within this class of compounds, complementary preparation of DMS derivatives can therefore be used to establish or to confirm the site, and thus the primary nature of the hydroxyl group, whereas preparation of TMS ethers may be of advantage in deducing molecular size. For the derivatives of secondary alcohols this diagnostically useful difference in fragmentation behaviour is not observed.     

Rapid and efficient protection of alcohols and phenols,and deprotection of trimethylsilyl ethers catalyzed by a cerium‐containing polyoxometalate

Herein, we want to report a simple and convenient way for protection‐deprotection of alcohols in the presence of ammonium decatungstocerate(IV) {(NH₄)₈[CeW₁₀O₃₆]·20H₂O} as catalyst under ambient temperature in CH₃CN. Using 0.002 mmol of the catalyst, various alcohols and phenols were transformed easily to the corresponding TMS ethers in excellent yields. In the second part, various TMS ethers were successfully converted to the parent hydroxyl compounds in the presence of the ammonium decatungstocerate(IV) catalyst. Copyright © 2010 John Wiley & Sons, Ltd.     

Bi(III) SALTS AS NEW CATALYSTS FOR THE SELECTIVE CONVERSION OF TRIMETHYLSILYL AND TETRAHYDROPYRANYL ETHERS TO THEIR CORRESPONDING ACETATES AND FORMATES

ABSTRACT

Bi(III) salts such as BiCl₃, Bi(TFA)₃ and Bi(OTf)₃ were found to be efficient catalysts for the transformation of trimethylsilyl (TMS) and tetrahydropyranyl (THP) ethers to their corresponding acetates and formates with acetic acid and ethyl formate. Selective acetylation and formylation of TMS and THP ethers of alcohols in the presence of phenolic TMS and THP ethers make this method a useful and practical procedure in organic synthesis.     

Comparative photophysical behaviour of naphthalene-linked crown ethers and aza crown ethers of varying cavity dimensions

A comparative time-resolved emission studies of several naphtho-crown ethers I–V, where metal ions can be complexed in a predetermined orientation with respect to the naphthalene (Naph) π-plane and naphthalene-linked aza crown ethers (L1 and L2) have been presented. In both the systems, crown ethers and aza crown ethers, naphthalene fluorescence gets quenched. In the systems I to V, the quenching is mainly due to efficient spin-orbit coupling (SOC) leading to greater population of the lowest triplet state of naphthalene. This SOC depends on the orientation of the crown ring with respect to the Naph-π-plane. However, in the systems L1 and L2, the quenching is due to photoinduced electron transfer (PET) from nitrogen lone pair of the aza crown ring to naphthalene moiety and consequent exciplex formation. The results have been interpreted using the time-resolved emission studies of all the compounds in various solvents, their alkali metal ion complexes, and protonated ligands.     

Direct cross-dehydrogenative coupling reactions of imidazopyridines and 1-naphthylamines with ethers under metal-free conditions

Abstract

Convenient, efficient metal-free direct cross-dehydrogenative coupling reactions of imidazopyridines and 1-naphthylamines with ethers were developed. This procedure provided a wide range of valuable, structurally diverse 3-alkyl-imidazopyridine and 4-alkyl-1-naphthylamine derivatives in moderate-to-good yields and with good functional group tolerance.     

Mass spectrometry of the trimethylsilyl derivatives of some cardiac aglycones and monoglycosides

Mass spectra of the trimethylsilyl (TMS) ethers of digitoxigenin, digoxigenin, digitoxigenin monodigitoxoside, digoxigenin monodigitoxoside and peruvoside were obtained. Ions appearing at m/e 170 and m/e 183 are proposed to be indicative of the enol TMS ether moiety as confirmed by appropriate shifts in the mass spectrum of digitoxigenin derivatized with perdeuterotrimethylsilylating reagent. The TMS ether derivatives of the monoglycosides produced abundant molecular ions and the base peaks in the spectra represent fragments of the sugar portion of the molecule.     

New methodology for the synthesis of benzoazacrown ethers by transformation of the macrocycle of benzocrown ethers

The review summarizes the results of studies aimed at constructing new promising macrocyclic ligands that bind metal and ammonium ions. A new approach to the synthesis of formyl and nitro derivatives of 1-aza-2,3-benzocrown ethers possessing considerable synthetic potential is described. The review presents a radically new methodology for the synthesis of such benzoazacrown ethers based on stepwise transformations of the macrocycle of readily accessible benzocrown ethers. The main structural factors and necessary conditions enabling stepwise transformations of the macrocycle of crown ethers into azacrown ethers were revealed. For the first time, the ability of N-methylbenzoazacrown ethers to form complexes was found, which is much superior to that of widely used N-phenylazacrown ethers and benzocrown ethers with the same size of the macrocycle.     

Mass spectrometry in structural and stereochemical problems—CXCIX Contrasting fragmentations of singly- and doubly-charged o-, m- and p-hydroxyalkylphenones and their trimethylsilyl ethers

High resolution mass spectrometry, metastable defocusing and deuterium labeling of trimethylsilyl (TMS) ethers have been used to study the electron-impact induced fragmentations of o-, m- and p-hydroxyalkylphenones and their TMS ether derivatives. These derivatives have proven useful in contrasting the fragmentation patterns of singly- and doubly-charged ions because of the competing fragmentations: α-cleavage and a McLafferty rearrangement from the ketone moiety and methyl cleavage from the TMS group. A proximity effect was responsible for a markedly increased methyl radical loss from the o-TMS ether. This fragmentation was minor with the m- and p-isomers. Significantly intense doubly-charged ions were formed from ketonic cleavage and by the loss of a TMS methyl radical. The sequence of fragmentation depended on the size of the alkyl group attached to the ketone carbonyl. There was no evidence found for a McLafferty rearrangement occurring from the doubly-charged molecular ion of the TMS ethers of the hydroxyalkylphenones but the rearrangement occurred from the doubly-charge molecular ion of bis-3-(1-oxopentyl)-4-hydroxy-phenyl-methane and, of course, from the singly charged [M]^+. The bis-p-hydroxyphenylmethane derivatives were studied in an effort to increase the intensity of the doubly-charged ions as it was expected that the charges would be separated by a longer distance.     

Synthesis of furan-fused 1,4-dihydrocarbazoles via an unusual Garratt-Braverman Cyclization of indolyl propargyl ethers and their antifungal activity

The reactivity of indole based bis-propargyl ethers 4a-4g under Garratt-Braverman condition (KOBu^t in refluxing toluene) has been studied. Interestingly, these propargyl systems with one arm attached with substituted 3-indolyl derivatives leaving the other arm unsubstituted produced the 3,4-furan fused dihydrocarbazole derivatives 6a-6g (and not the expected carbazole derivatives) as the predominant product (70–82%) making this methodology to access such derivatives an attractive route. The results are supported by computational studies and some of the carbazole derivatives showed good antifungal activities.     

Cyclic Boronate Derivatives in Combined Gas Chromatography - Chemical Ionisation Mass Spectrometry

Abstract

The utility of cyclic boronate derivatives for the combined gas chromatography-mass spectrometry of 1,2- and 1,3- diols has been further extended by the application of chemical ionisation techniques. Abundant quasi-molecular ions (M+1) in the isobutane chemical ionisation spectra of the examples studied (which include the methaneboronates of monoglycerides, monoalkyl glyceryl ethers, a steroid, dihydrosphingosine and a ceramide) are frequently accompanied by intense and informative fragment ions.     

Novel monoaza- and diazacrown ethers incorporating sugar units and their extraction ability towards picrate salts

A number of new 15- and 1 8-membered ring aza-crown (4, 5, 8–13, 17, 18) and lariat ethers (6, 7) incorporating glucose or galactose units have been synthesized in good yields by a simple route. Their extracting abilities were measured with Li⁺, Na⁺, K⁺ and NH ₄ ⁺ cations. The substituents at the nitrogen atom and the type of monosaccharide affected this property significantly.     

Oxidative Deprotection Of Trimethylsilyl and Tetrahydropyranyl Ethers and Ethylene Acetals With Benzyltriphenylphosphonium Peroxomonosulfate in the Presence of Bismuth Chloride Under Non-Aqueous Conditions

Abstract

Benzyltriphenylphosphonium peroxomonosulfate (BnPh₃P⁺HSO₅ ^?) (1) is used as a new reagent for oxidative deprotection of trimethylsilyl and tetrahydropyranyl ethers and ethylene acetals to afford carbonyl compounds in refluxing acetonitrile in the presence of bismuth chloride.     

Synthesis of Fulvene Vinyl Ethers by Gold Catalysis

Gold-catalyzed cyclization of 1,5-diynes with ketones as reagents and solvent provides diversely substituted vinyl ethers under mild conditions. The regioselectivity of such gold-catalyzed cyclizations is usually controlled by the scaffold of the diyne. Herein, we report the first solvent-controlled switching of regioselectivity from a 6-endo-dig- to 5-endo-dig-cyclization in these transformations, providing fulvene derivatives. With respect to the functional-group tolerance, aryl fluorides, chlorides, bromides, and ethers are tolerated. Furthermore, the mechanism and selectivity are put to scrutiny by experimental studies and a thermodynamic analysis of the product. Additionally, 6-(vinyloxy)fulvenes are a hitherto unknown class of compounds. Their reactivity is briefly evaluated, to give insights into their potential applications.     

Studies on the synthesis and properties of open-chain and macrocyclic crown compounds

Eight new open-chain crown compounds (1–8) and two new macrocyclic crown ethers (9 and10) were synthesized from 1,5-bis(2-aminophenoxy)-3-oxapentane (15) and 1,8-bis(2-aminophenoxy)-3,6-dioxaoctane (16) which were prepared by the catalytic hydrogenation of the corresponding bis(2-nitrophenoxy) derivatives13 and14. The fluorescent property investigation of two open-chain crown ethers (7 and8) indicated that they exhibit complexing effects on Ag⁺ and Mn²⁺ cations and can be used as fluorescent reagents for the microanalysis of the metal cations. The pyrolysis kinetics measurement for compounds5 and6 in nitrogen and air was carried out, and their reaction orders and activation energy were obtained. They are one-step and two-step pyrolysis reactions in nitrogen and air, respectively.     

Mass spectrometry of the triethylsilyl,tri-n-propylsilyl and tri-n-butylsilyl derivatives of some alcohols,steroids and cannabinoids

The 25 _eV mass spectra of the trialkylsilyl (R = Et, Pr, Bu) derivatives of several alcohols, steroids and cannabinoids are compared with those of the corresponding trimethylsilyl (TMS) derivatives. Abundant ions produced by elimination of one of the alkyl groups characterize most of the spectra. Although the presence of such ions is advantageous in certain cases, such as for single ion monitoring studies, the spectra usually contain fewer ions of diagnostic use than the spectra of corresponding TMS derivatives. Successive elimination of C_nH_2n fragments is also a feature of these spectra.