Benzyl Methyl Ether Research Articles

Intramolecular CH⋯π and CH⋯O interactions in the conformational stability of benzyl methyl ether studied by matrix-isolation infrared spectroscopy and theoretical calculations

Contributions of the intramolecular CH⋯π and CH⋯O interactions to the molecular conformation of benzyl methyl ether (BME) have been investigated by matrix-isolation infrared (IR) spectroscopy combined with quantum chemical calculations. Comparative investigations have been carried out for propylbenzene. Quantum chemical calculations predict that there are two conformers for BME; for the ET conformer the methyl ether and the phenyl groups lie in the plane of the benzene ring, while for the AG conformer they are out of the plane. Comparison between the observed and calculated spectra for BME reveals that the ET and AG conformers coexist in an Ar matrix. By measuring matrix-isolation IR spectra of BME deposited at different gas temperatures, the enthalpy difference (Δ H (AG − ET)) between ET and AG conformers was determined to be −1.03 ± 0.06 kJ mol −1. The experimental and calculation results indicate that the AG conformer of BME is stabilized by the intramolecular CH⋯π and CH⋯O interactions.

Synthesis of Nucleoside Analogues Bearing the Five Naturally Occurring Nucleic Acid Bases Built on a 2-Oxabicylo[3.1.0]hexane Scaffold

Hitherto unknown nucleoside analogues incorporating the five naturally occurring nucleic acid bases built on a 2-oxabicyclo[3.1.0]hexane template were synthesized. The synthesis of these new conformationally restricted nucleoside analogues involved the preparation of a suitable sugar precursor bearing the 2-oxabicyclo[3.1.0]hexane scaffold. This sugar was readily obtained from [(3aS,6aS)-2,2-dimethyl-3a,6a-dihydrofuro[2,3-d][1,3]dioxol-5-yl]methyl benzyl ether (4) following a Simons-Smith-type cyclopropanation reaction. Finally, glycosylation reactions and deprotection provided the nucleoside analogues. Using nucleoside 14 bearing thymine base as a model, we found that the conformation of such nucleoside analogue was restricted toward a (0)T(1) conformation.

Mechanistic Studies on the Cyclization of (Z)-1,2,4-Heptatrien-6-yne in Methanol: A Possible Nonadiabatic Thermal Reaction

Myers et al. pyrolyzed (Z)-1,2,4-heptatrien-6-yne (1) in methanol at 100 degrees C and observed benzylmethyl ether (2) as a major product and 2-phenylethanol (3) as a minor product. If a biradical intermediate, such as the open-shell singlet state of alpha,3-didehydrotoluene (4), was the only intermediate generated by the cyclization, then reaction with methanol might be expected to afford 2-phenylethanol as the principal product. The question that has been of interest since its first discovery is the origin of the principal product of the title reaction, benzylmethyl ether. This report considers three mechanisms for formation of the benzylmethyl ether: direct methanol participation in the cyclization of the reactant, partial ether formation from the biradical 4, or involvement of the closed-shell zwitterionic state of alpha,3-didehydrotoluene (5). A fourth mechanism, involving a cyclic allene intermediate, has been ruled out by earlier studies. In the present work, the first two mechanisms are ruled out by experiment and/or calculation. The remaining one, involving the zwitterion, is shown to be consistent with experimental and computational data only if a component of the reaction follows a nonadiabatic course.

Synthesis of Enantiomerically Enriched β‐Amino Alcohol Derivatives via Chiral Base Mediated‐Asymmetric Deprotonation of (Benzyl Methyl Ether) Tricarbonylchromium(0) Complex and Electrophilic Trapping with Imines.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis of enatiomerically enriched β-amino alcohol derivatives via chiral base mediated-asymmetric deprotonation of (benzyl methyl ether) tricarbonylchromium(0) complex and electrophilic trapping with imines

Deprotonation of (benzyl methyl ether)tricarbonylchromium(0) complex 1 by chiral base 2 followed by quenching reaction with imines 3 and subsequent decomplexation give β-amino alcohol derivatives 5 in good yields and high enantioselectivities (up to 96% e.e.).

Dibenzyl bromophenols with diverse dimerization patterns from the brown alga Leathesia nana.

Six novel dibenzyl bromophenols (1-6) with different dimerization patterns and two propyl bromophenol derivatives (7 and 8), together with 11 known bromophenol derivatives, were isolated from the ethanolic extract of the brown alga Leathesia nana. On the basis of spectroscopic methods the structures of the new compounds were determined as 5,6'-diethyloxymethyl-3,4,2'-tribromo-2,3',4'-trihydroxydiphenyl ether (1), 2-(2,3-dibromo-4,5-dihydroxybenzyl)-3,5-dihydroxy-4-methoxybenzyl alcohol (2), 6-(2,3-dibromo-4,5-dihydroxybenzyl)-2,3-dibromo-4,5-dihydroxy benzyl methyl ether (3), 9,10-dihydro-9,10-dimethoxy-3,4,7,8-tetrabromo-1,2,5,6-tetrahydroxyanthracene (4), (+)-3-(2,3-dibromo-4,5-dihydroxyphenyl)-4-bromo-5,6-dihydroxy-1,3-dihydroisobenzofuran (5), rel-(4aS,10aR)-(+/-)-6,7-dibromo-4a-hydroxy-3,8-dihydroxymethyl-10a-methoxy-1,4,4a,10a-tetrahydrodibenzo[b,e][1,4]dioxin-1-one (6), (E)-2-methyl-3-(2,3-dibromo-4,5-dihydroxyphenyl)propenal (7), and 2-methyl-3-(2,3-dibromo-4,5-dihydroxyphenyl)-1-propanol (8). Some compounds including 3 showed in vitro selective cytotoxicity against several human cancer cell lines. This is the first brown alga to be reported containing bromophenols.

Reductive lithiation of alkoxy-substituted benzyl methyl ethers and connection with cross-coupling reactions

2-and 4-Ethoxymethoxybenzyl methyl ethers were employied as useful starting materials for the synthesis of 1,2- or 1,4-dicarbo-substituted benzenes. The proposed reaction sequence involves connection between the reductive lithiation of benzyl alkyl ethers and the metal-catalyzed cross-coupling reaction of aromatic triflates.

A ring walk of methylene groups in toluene radical cations. An extension of the toluene-cycloheptatriene rearrangement of aromatic radical cations. Theory and experiment.

The minimum energy reaction pathway (MERP) of the toluene-cycloheptatriene radical cation rearrangement (TOL/CHT-rearrangement) has been calculated by the UHF and DFT model at the level UHF/6-311+G(3df,2p)//UHF/6-31G(d) and B3LYP/6-311+G(3df,2p)//B3LYp/6-31G(d), respectively, including the ring walk of the substituent by a 1,2-shift around the aromatic ring. This ring walk corresponds to interconversion of distonic ions and norcaradiene radical cations (the two intermediates of the TOL/CHT-rearrangement) by making and breaking of the external C-C bonds of the cyclopropane moiety of the intermediate norcaradiene structure. For toluene radical cation 1, UHF calculations adequately reproduce earlier results(4) and show, that the ring walk of the CH(3)-substituents requires slightly more energy than formation of the cycloheptatriene radical cation. By the DFT model, the distonic ion, which is formed initially by a 1,2-H shift from CH(3) to the benzene ring, is not stable but the transition state of an interconversion of norcaradiene radical cations along a ring walk of the CH(3) substituent. The activation energy for this ring walk exceeds that for formation of the cycloheptatriene radical cation by c. 30 kJ mol(-1). Thus, isomerization of 1 by a ring walk of the CH(3)-substituent competes with the TOL/CHT-rearrangement likely only for excited 1. The calculation was repeated for the MERPs of a TOL/CHT-rearrangement of para-xylene radical cation 5 and ethylbenzene radical cation 2, yielding basically the same results as for 1. According to the calculation, polar substituents alter significantly the relative energies of the competing routes of isomerization. For benzylcyanide 3 (X = CN), the activation energy for a ring walk of the NC-CH(2)-substituent is distinctly below that of a ring enlargement. For benzyl methyl ether 4 (X = OCH(3)), the distonic intermediate along the UHF-MERP is unusually stable. Further, the 7-methoxy-norcaradiene radical ion is unstable and corresponds to a transition state between isomeric distonic intermediates differing by a 1,2-shift of the side chain. In contrast, the 7-methoxy-norcaradiene radical ion is the only intermediate of the DFT-MERP, and the distonic ion is the transition state for a 1,2-shift of the cyclopropane ring. A ring walk of the CH(3)OCH(2)-substituent is much more favorable than formation of a 7-methoxy-cycloheptatriene radical cation in both MERPs. The findings of the theoretical calculation are substantiated by the mass spectrometric fragmentations of meta- and para-methoxymethylated 1-phenylethanols 8 and 9 and of para-methoxymethyl substituted benzyl ethyl ether 10 and benzyl n-propyl ether 11. Important fragmentation routes of metastable molecular ions of these compounds correspond to elimination of alcohols. Use of deuterated derivatives shows that the elimination occurs by a "false" ortho-effect which requires migration of a ROCH(2)-substituent around the benzene ring. Results of particular interest are obtained for the asymmetric bis-ethers 10 and 11. Here, the MIKE spectra of the molecular ions of deuterated analogs reveal a selective ring walk of the C(2)H(5)OCH(2)- and n-C(3)H(7)OCH(2)-side chain, respectively.

Evaluation of biodegradation behavior of poly(ε-caprolactone) with controlled terminal structure by pyrolysis-gas chromatography and matrix-assisted laser desorption/ionization mass spectrometry

The enzymatic degradation behavior of poly(ε-caprolactone) (PCL) with an α-benzyloxy terminal during an enzymatic degradation test using cholesterol esterase was evaluated complementarily by pyrolysis-gas chromatography (Py-GC) in the presence of tetramethylammonium hydroxide (TMAH) and matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS). On the pyrograms of PCL samples, dimethyl derivative of ε-caprolactone and some related products originating from ε-caprolactone (ε-CL) units were observed together with those from benzyloxy terminal units such as benzyl methyl ether. The relative content of the benzyloxy terminal unit in the residual PCL sample after the degradation test, which was estimated from the relative intensities of the specific pyrolysis, considerably fell down especially in the initial stage of the degradation test. On the other hand, in the MALDI mass spectra, the observed molecular weight distribution of the PCL molecules having a benzyloxy terminal was substantially unchanged during the enzymatic degradation, while PCL molecules without benzyloxy terminal appeared at the lower mass region after the degradation test. These results suggested that the enzymatic degradation of the PCL might proceed mainly in the exo-cleavage mode from α-benzyloxy terminal side under a given condition.

Reaction Cascade in the Anodic Oxidation of Benzyl Silanes in Methanol

Controlled-potential anodic oxidation at carbon of a series of benzyl trialkylsilanes in methanol affords benzyl methyl ether irrespective of the nature of the alkyl groups on silicon. Constant-current oxidation of the same silanes produces the same ether, which is then converted successively to benzaldehyde dimethyl acetal and then to a mixture of methyl orthobenzoate and methyl benzoate. © 2003 The Electrochemical Society. All rights reserved.

Involvement of adsorption effects in the TiO2‐sensitized photooxidation rate of benzylic derivatives in CH3CN

AbstractCompetitive kinetic experiments in the TiO2‐sensitized photooxidation of some series of differently ring‐substituted benzylic derivatives (ArCHROR′) in aerated and/or deaerated CH3CN and in the presence of Ag2SO4 were carried out. From logkrel vs Ep plots it was hypothesized that a changeover of the electron abstraction site occurs on going from electron‐donating to electron‐withdrawing groups on the ring, from the aromatic moiety to the OCH3 group of benzyl methyl ethers, probably owing to the preferential adsorption of this group on TiO2 with respect to the aromatic ring. This phenomenon is not observed with benzyltrimethylsilanes because the orbital resulting from the overlap between the C— Si bond and the aromatic π system is the only adsorption site. The steric hindrance of an α‐methyl group (in benzylic alcohols) or a tert‐butyl group (in benzyl tert‐butyl ethers) reduces the degree of adsorption but does not influence the shape of the plot because OR′ should still be the preferential adsorption group. This also provides useful information about the surface structure of TiO2 suspended in CH3CN. Copyright © 2003 John Wiley & Sons, Ltd.

Mild catalytic multiphase hydrogenolysis of benzyl ethers

A preliminary study was conducted on the multiphase (aqueous KOH–isooctane–Aliquat® 336) hydrogenolysis of benzyl methyl ether using Pd/C, Pt/C and Raney-Ni as catalysts, under mild conditions (T = 50 °C, pH2 = 1 atm). Using ethanol as solvent, the Pd/C system is very efficient, while the same catalyst under multiphase conditions is almost inactive. With Pt/C, the reaction is always sluggish, and ring hydrogenation kicks in under multiphase conditions. The Raney-Ni system has an opposite behavior, while debenzylation is slow in ethanol, under multiphase conditions the reaction is quite fast. Other O-benzyl protected substrates undergo debenzylation with Raney-Ni as well, with varying chemoselectivity.

Enhanced Leaving Ability of Methoxy Group and Retarded Deprotonation on the Carbon Atom Linked to the 1-Position of 8-Phosphino- or 8-Amino-naphthalene

Abstract In an attempt to lithiate a benzylic carbon, a benzyl methyl ether bearing an 8-phosphino-1-naphthyl group at the benzylic carbon is treated with t-butyllithium to result in the formation of a quite unexpected compound, arising not from deprotonation but from the removal of the methoxy group accompanied by the introduction of two t-butyl groups into the naphthalene ring.

Electron energy loss and dissociative electron attachment spectroscopy of methyl vinyl ether and related compounds

The triplet and singlet excited states of methyl vinyl ether have been characterized by electron energy loss spectroscopy and multireference density functional theory with configuration interaction (DFT/MRCI). The electron attachment energy was determined from the excitation functions for vibrational excitation to be 2.3 eV. Dissociative electron attachment spectra have been measured with a mass spectrometer having a trochoidal monochromator in the incident electron beam. Fragment anion bands peaking at 3 eV, 6.5 eV and 9.5 eV have been found in methyl vinyl ether. The first band is assigned to the 2(π∗) shape resonance, the second band to a resonance where an electron is loosely bound by dipole and polarization forces to the target molecule in its valence excited 1(π, π∗) state, and the third band to Feshbach resonances with occupation of Rydberg orbitals. CH 3O − and H 2CC − are formed at 3 eV, CH 3O − and HCC − at 6.5 and 9.5 eV. The fragmentation pattern of ethyl vinyl ether at 3 eV is similar, yielding ethanolate and vinylidene anions, but with the unexpected addition of the deprotonated acetaldehyde anion CH 2CHO −. The fragmentation patterns of methyl allyl ether and benzyl methyl ether are dominated by the methanolate anions with high intensity, indicating that dissociation of C–O bond in unsaturated ethers is much faster if this bond does not lie in the plane of the π system.

Mechanism of the oxidation of benzylic ethers photosensitized by a 2,4,6-triphenylpyrylium salt

The photooxidation of various benzyl methyl ether derivatives (XPhCH2OMe, with X = H, 4-MeO, 4-Me, 3-Cl, 4-CF3 and 3-CF3) sensitized by 2,4,6-triphenylpyrylium tetrafluoroborate in MeCN, in the presence of oxygen, was investigated by product analysis, fluorescence quenching and quantum yield determinations. The reaction is suggested to proceed through a benzylic radical cation intermediate, formed by electron transfer from the ether to the sensitizer. Besides the back electron transfer reaction, which gives the reactant again, the primarily formed radical cation is deprotonated and the resultant α-methoxybenzyl radical reacts through two different paths to yield benzaldehydes and methyl benzoates in a ratio that depends on the ring substituent. Fluorescence quenching and quantum yield studies have pointed out that (i) the singlet-excited state of the acceptor is mainly involved and (ii) the competition between deprotonation and back electron transfer reaction is regulated by the nature of the substituent. Hydrogen peroxide, detected together with the organic products, has been suggested to be formed in the TPP+ regeneration process through the involvement of oxygen and the acidity of the medium.

Volatile components of green walnut husks.

Volatiles were isolated from whole green mature walnuts (Hartley variety) with husks still intact using dynamic headspace sweeping with trapping on Tenax. A total of 45 volatile compounds were identified by GC-MS. Major volatiles identified included (E)-4, 8-dimethyl-1,3,7-nonatriene, pinocarvone, pinocarveol, myrtenal, myrtenol, (E,E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene, caryophyllene epoxide, verbenol, verbenone, and terpinolene. Green walnuts that had been infested with codling moth showed appreciably higher amounts emitted for (E)-4,8-dimethyl-1,3,7-nonatriene, (E, E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene, alpha- and beta-pinenes, sabinene, (E)-beta-ocimene, (E,E)-alpha-farnesene, and linalool. The infested nuts also emitted benzyl methyl ether, isobutyl cyanide, and 1-nitro-3-methylbutane, compounds not found with the healthy nuts. Volatiles from uninfested green walnuts at the maturity stage where the husk was just beginning to split were also analyzed and compared.

Preparation of polyethers via proton acid catalyzed transetherification reactions

An approach for the preparation of polyethers by a transetherification route has been developed. This approach involves the melt condensation of a diol with a specifically designed diether in the presence of a catalyst to yield polyethers with the exclusion of two moles of a low boiling alcohol, in this case methanol. The diether monomers are designed so as to contain two labile benzyl methyl ether linkages that can readily undergo a transetherification process. These diether monomers (5 a and 5 b) readily undergo transetherification polycondensation with di-, tri- and tetraethylene glycols as well as with a variety of aliphatic diols to yield polymers of moderately high molecular weights. The glass transition temperatures (Tg) of the polymers decrease with increasing length of the diol. Melting transitions (Tm) are observed only in some polymers containing aliphatic units but those with the oligo(ethylene oxide) units are completely amorphous. Preliminary ionic conductivity studies indicate that the polyethers with oligo(ethylene oxide) units could serve as excellent candidates in solid polymer electrolyte applications.

Polymers Containing Etch Resistant Ether Protecting Groups for DUV Lithography.

In this paper, we have shown the importance of acid labile ether protecting groups in the design of high performance 248nm resists with significantly improved etch resistance. Using α-methylbenzyl ether protecting group, we have synthesized and studied partially protected poly(hydroxystyrene) derivative, PHS-MBE. Studies clearly pointed out that methylbenzyl ether protecting group is thermally stable and undergoes acid catalyzed deprotection leading to preferential rearranged products due to electrophilic ring substitution. Such a rearrangement is shown to provide a unique mechanism to reduce/eliminate resist shrinkage and improve lithographic performance and RIE stability.

Polymeric photoinitiators having benzoin methylether moieties connected to the main chain through the benzyl aromatic ring and their activity for ultraviolet-curable coatings

New polymeric UV photoinitiators, bearing the benzoin methyl ether moiety linked to the side chain through the 4′ position, were synthetized by radical homopolymerization of the corresponding monomers, 4′-methacryloyloxy benzoin methyl ether and 4′-methacryloyloxy α-methyl benzoin methyl ether, prepared in turn after a thorough investigation of synthetic methods. For comparison, low molecular weight structural models of the repeating co-units of the polymers having the pivaloyloxy group linked to the 4′ position of the benzoin methyl ether moiety were also prepared. All polymeric and model compounds were fully characterized and employed in the photoinitiated polymerization and crosslinking of a standard acrylic formulation for clear UV curable coatings. The photoinitiating activity of these systems, measured by microwave dielectrometry, indicates a higher cure fastness for the model compounds with respect to the corresponding polymeric derivatives, and such a behaviour is tentatively interpreted in terms of the fragmentation mechanism of the benzyl methyl ether radicals formed on α-photocleavage of the benzoin moiety.

Enantioselective carboxylation of α-methoxybenzyllithium generated via asymmetric lithiation with a t-BuLi/chiral bis(oxazoline) complex

Treatment of benzyl methyl ether with a t-BuLi/chiral bis(oxazoline) complex followed by carboxylation is shown to afford α-methoxy phenylacetic acid in high % ee (up to 95%). The asymmetric induction was proved to occur at the post-lithiation step.