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The synthetic utility of alkyl-onium salt compounds is widely recognized in the field of organic chemistry. Among the wide variety of onium salts, quaternary ammonium, phosphonium, and tertiary sulfonium salts have been the most useful compounds in organic syntheses. These compounds have been very useful reagents in the construction of organic building blocks. In addition, onium salts are known as reliable catalysts, which are used to promote important organic transformations by serving as phase-transfer and ion-pair catalysts through the activation of nucleophiles. Although phase-transfer catalysis is a major direction for onium salt catalysis, hydrogen-bonding catalysis of alkyl-onium salts, which is promoted via the activation of electrophiles, has recently become a relevant topic in the field of onium salt chemistry. This Minireview introduces new possibilities and future directions for alkyl-onium salt chemistry based on its use in hydrogen-bonding catalysis and on its overall utility.

Although cyclic diaryliodonium species have the potential to act as valuable synthons for cascade transformations, they still remain largely unexplored. The regioselectivity associated with unsymmetrical cyclic diaryliodonium species has previously been known to pose a challenge. A regioselective relayed alkynylation and olefination of unsymmetrical cyclic diaryliodonium species has been achieved by installation of a directing amido group. These relayed transformations were delayed until an oxazole ring had formed, delivering a series of unique fluorescent benzoxazoles. Moreover, some of these synthetic benzoxazoles showed apparent inhibitory activity against malignant cancer cells. Further confocal visualization revealed that benzoxazoles targeted cell nuclei. These findings might provide a novel structural scaffold to develop desirable anticancer agents.

This study probes the nature of noncovalent interactions, such as cation-π, metal ion-lone pair (M-LP), hydrogen bonding (HB), charge-assisted hydrogen bonding (CAHB), and π-π interactions, using energy decomposition schemes-density functional theory (DFT)-symmetry-adapted perturbation theory and reduced variational space. Among cation-π complexes, the polarization and electrostatic components are the major contributors to the interaction energy (IE) for metal ion-π complexes, while for onium ion-π complexes (NH4+, PH4+, OH3+, and SH3+) the dispersion component is prominent. For M-LP complexes, the electrostatic component contributes more to the IE except the dicationic metal ion complexes with H2 S and PH3 where the polarization component dominates. Although electrostatic component dominates for the HB and CAHB complexes, dispersion is predominant in π-π complexes.

The account presented here summarizes progress from the author's laboratory during the past 15 years on the application of room temperature ionic liquids (RTILs) as solvents and catalysts in electrophilic/onium ion chemistry as well as in metal-mediated bond forming reactions.

The first practical, yet simple, preparation of aryl(alkynyl)iodonium trifluoroacetate salts is described. The generic nature of this synthetic method has allowed the production of a range of aryl(alkynyl)iodonium trifluoroacetate salts with independent variation of both the alkynyl and aryliodo groups in yields of 30–85 %. Application of these new reagents to the synthesis of a series of 2-arylfuro[3,2-c]pyridines (40–64 %) highlights the potential of this class of materials as precursors to bioactive heterocyclic structures. These experiments have also demonstrated that, in this case, the effect of the aryliodo group on the reaction is negligible.

Two novel redox initiator systems have been developed for carrying out the cationic polymerizations of vinyl and heterocyclic monomers. The initiators are based on various onium salts as the oxidant together with an alkylborane or an organosilane as the reducing agent. Using both redox cationic initiator systems, the polymerizations of a wide variety of monomers can be carried out at or below room temperature in the presence or absence of unreactive solvents. Also described in this communication is the novel use of a two-component redox system in which the reducing agent, a silane, is delivered to the monomer sample in the vapor state. Optical pyrometry (infrared thermography) was employed as a convenient method with which to monitor the polymerizations in real-time. A study of the effects of variations in the structures of the onium salt, the silane and the type of noble metal catalyst were carried out. The use of these initiator systems for carrying out commercially attractive crosslinking polymerizations for coatings, composites and electronic encapsulations is discussed.

Quaternary onium salts of halides can be efficiently converted into the corresponding quaternary onium salts of various anions [NO3–, BF4–, PF6–, CF3SO3–, CH3SO3–, ClO4–, p-CH3C6H4SO3–, CF3CO2–, 2,4-(NO2)2C6H3O–] by treating the onium halide with trimethyl phosphate under neat condition in the presence of an equivalent amount of conjugate acid of the desired anion.

In this work, diversified quaternary onium salt-type triphase catalysts (TPC) were prepared based on crosslinked polystyrene (CPS) microspheres, and the relationship between their chemical structures and catalytic activities in liquid-solid-liquid reaction system were investigated in depth by using the esterification reaction of benzyl chloride with sodium acetate as a model system. The experimental results indicate that the chemical structures of the TPC affect their catalytic activity greatly and there are four basic points: (1) the quaternary phosphonium-type TPC have higher activity than quaternary ammonium-type catalyst; (2) the TPC with more lipophilic substitutes at N atom have higher catalytic activity; (3) the TPC with longer spacer arm, which links quaternary onium salt group to the matrix microsphere, have higher catalytic activity; (4) the bonding density of quaternary onium salt group on the polymeric carrier affects the hydrophilic and hydrophobic property of the TPC, and consequently, influences the catalytic activity significantly. For a given triphase catalysis system, there is an optimal bonding density of quaternary onium salt group on the solid catalysts. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

In this paper was presented an application of task specific onium salt as soluble support in multicomponent synthesis of 2-amino-3-ethoxycarbonyl-naphthopyrans. The starting task-specific onium salt was functionalized in good yield with chloroethyl alcohol, followed by three steps containing esterification, three components reaction and cleavage from onium salt to afford naphthopyrans in 60% –88% overall yields. All of the products were characterized by IR, 1H NMR, 13C NMR and MS techniques.

In this article, a new route for the synthesis of N-aryl heteroaromatic onium salts by the direct copper catalyzed arylation of pyridine, substituted pyridines, isoquinoline, and acridine with diaryliodonium salts is described. It was demonstrated that these N-aryl heteroaromatic onium salts undergo facile platinum or rhodium-catalyzed reduction by silanes bearing Si—H groups. The reduction of N-aryl heteroaromatic onium salts generates Bronsted acids. When this redox reaction was carried out in situ in the presence of an appropriate monomer, cationic polymerization was observed. Using this approach, the cationic polymerizations of epoxides, oxetanes, 1,3,5-trioxane, styrene, and vinyl ethers were carried out. The use of optical pyrometry to monitor the redox initiated cationic polymerizations of some representative multifunctional monomers is described.

This paper describes a positive resist formulation containing silylated polystyrene polymer, made photosensitive at wavelengths from 220 to 310 nm by means of an onium salt sensitizer ((C6H5)3SMXn) and at wavelengths from 360 to 450 nm by means of an onium salt and a dye photosensitizer (perylene). In the present study, we report the desilylation of acid-sensitive polymers as poly (4-trimethylsiloxystyrene) or poly [p-trimethylsiloxystyrene-co-p-(tert-butoxycarbonyl) oxystyrene]. The formed Bronsted acid which induces the cleavage of silicon - containing side groups is HMXn. The transformation reaction is followed by IR spectroscopy before and after exposure. This resist system is resistant to etching in an oxygen plasma.

Novel redox initiators for cationic polymerizations were developed consisting of an onium salt together with a SiH functional silane or siloxane. The reduction of the onium salt by the silane is catalyzed by noble metal complexes or certain transition metal compounds and takes place spontaneously at room temperature. The redox reaction of the onium salt with the silane results in the liberation of a strong Bronsted acid that can be subsequently used to initiate cationic polymerizations. Typical onium salts that have been employed in these redox initiator systems are diaryliodonium salts, triarylsulfonium salts and S,S-dialkyl-S-phenacylsulfonium salts. Studies of the effects of variations in the structures of the onium salt, the silane and the type of noble metal catalyst were carried out. In principle, the redox initiator systems are applicable to all types of cationically polymerizable monomers and oligomers, including the ring-opening polymerizations of such heterocyclic monomers as epoxides and oxetanes and, in addition, the polymerization of vinyl monomers such as vinyl ethers, N-vinylcarbazole and styrenic monomers. The use of these novel initiator systems for carrying out commercially attractive crosslinking polymerizations for coatings, composites and encapsulations is discussed. Copyright © 2009 John Wiley & Sons, Ltd.

Tin knows its oniums! An unusual nitride tetrastannylene and a stannylenated ammonium ion stabilized by a samarium tetradiazaphospholido counterion are the first examples of a tris(organostannylenyl)amine derivative and a divalent tin coordinate onium ion that incorporates 1,2,4-diazaphospholide ligand (see figure).

A new two-component system, consisting of a matrix and an onium salt as comatrix, is described for detection of sulfo-peptides in the positive mode by matrix-assisted desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). Binary iodonium salts were superior to quaternary phosphonium salts in terms of suppression of desulfation and salt formation with the carboxyl group. Of the iodonium salts examined, bis(4-tert-butylphenyl)iodonium (BTI) hexafluorophosphate and bromide were most effective in giving intensive molecular ion signals in the form of [M(BTI)+BTI]+. The conditions optimized for O-sulfated tyrosine-containing peptides could be applicable for O-sulfated serine- and threonine-containing peptides. In the case of a phospho-peptide, a molecular ion appeared more intensively as a proton adduct than as a BTI adduct. Copyright © 2006 John Wiley & Sons, Ltd.

The primary objective of this study was to improve montmorillonite clay-platelet separation in vinyl ester resin matrix by organically modifying the nanoclay platelet with a partially reactive onium salt. The reactive onium salt (ω-undecylenyl amine hydrochloride) was synthesized from commercial ω-undecylenyl alcohol through a series of synthetic conversions. Nonreactive onium salt (undecyl amine hydrochloride) was made from commercial undecyl amine. These salts were characterized with 1H and 13C NMR and Fourier transform infrared techniques. The relative amounts of exfoliated, intercalated, and as-treated clay and the size of the clay particle aggregates depended significantly on the composition of clay and the processing conditions. When the clay was ion-exchanged with a mixture of reactive and nonreactive onium salts, a partially exfoliated vinyl ester resin polymer nanocomposite was formulated. The addition of a comonomer styrene and high-intensity ultrasonic mixing produced vinyl ester nanocomposite with the highest degree of clay-platelet exfoliation. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1310–1321, 2004

To synthesize an epoxy–montmorillonite nanocomposite, the intercalation of clay layers with acid onium ions {[H3N(CH2)n−1COOH]+, [H3N(CH2)n−1CH3]+, [H3N(CH2)−NH2]+, and [H3N(CH2)nNH3]2+} by different methods were studied. The intercalated clay was characterized by XRD, ICP, and CHN elemental analysis. An acid onium ion [H3N(CH2)17CH3]+ enlarged the d-spacing of CWC–, AMS–, and Kunipia–montmorillonite to 21.6, 18.1, and 20.7 A, respectively. The results of CHN elemental analysis confirmed that onium ions were intercalated between the clay layers. Ion exchange of montmorillonite with onium ions is a better way to intercalate more onium ions. Among those onium ions mentioned above, [H3N(CH2)nNH3]2+ displaced more sodium ions from the clay layers than did the others. An epoxy–montmorillonite nanocomposite was synthesized by heating a mixture of [H3N(CH2)17CH3]+–montmorillonite (CWC) with an epoxy monomer and curing agent. The nanocomposite was characterized by XRD, TEM, DSC, UV, TGA, and Instron testing. TEM photographs showed that the spacing between the clay layers was further enlarged to about 50 A and no segregation between the clay particle and the polymer was observed. The glass transition temperature of the nanocomposite containing 20 phr of [H3N(CH2)17CH3]+–montmorillonite (CWC) increased from 108.4 to 146.1°C. Especially, the nanocomposite possesses higher water resistance than that of the epoxy resin or of the physical mixture of epoxy and montmorillonite (CWC). According to the transmittance measurement (λ = 550 nm), the nanocomposite shows good light transmittance. Although, we cannot improve the mechanical properties, improvements of other properties can be evidenced for the formation of nanoscale composites. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 414–421, 2002

The synthesis of a series of novel cationically photopolymerizable epoxide monomers bearing benzyl, allyl, and propargyl acetal and ether groups that can stabilize free radicals was carried out. These monomers display enhanced reactivity in cationic photopolymerization in the presence of certain onium salt photoinitiators. Specifically, this article describes schemes for the synthesis of cycloaliphatic epoxy monomers bearing free-radical stabilizing groups. During UV irradiation of an onium salt cationic photoinitiator, the aryl radicals that are generated abstract labile protons present in such monomers to generate the corresponding carbon-centered radicals. Subsequently, these radicals can interact with the onium salt by a redox mechanism to induce the decomposition of these salts. The overall result is that additional cationic species are generated by this mechanism that increase the rate and extent of the cationic ring-opening polymerization of the epoxide monomer. An investigation of the photopolymerizations of the monomers prepared during this work was carried out using Fourier transform real-time infrared spectroscopy, and conclusions were drawn with respect to the relationship between their structures and reactivity. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2385–2395, 2001

Phenothiazine compounds bearing a wide range of different substituents are excellent photosensitizers for onium salt cationic photoinitiators. These photosensitizers are generally operative in the mid- and long-range regions of the UV spectrum and are especially useful for enhancing the rate of photoinitiated cationic polymerization carried out utilizing both filtered and broadband UV emission sources. In this article, the syntheses of several different substituted phenothiazines are described and the ability of these compounds to photosensitize the photolysis of different onium salt photoinitiators is evaluated. Attempts were made to correlate the structure and spectral characteristics of the phenothiazines with their efficiency of photosensitization in the cationic photopolymerizations of several typical epoxide and vinyl ether monomers. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1187–1197, 2001

A new system for efficiently carrying out cationic photopolymerizations with visible and long-wavelength UV light is described. This system is based on the principle that certain onium salt cationic photoinitiators can be reduced by free radicals produced by the hydrogen abstraction reactions of photoexcited ketones. Thus, when camphorquinone, benzil, 2-isopropylthioxanthone, and 2-ethylanthraquinone are irradiated in the presence of a monomer that can serve as a hydrogen donor, the resulting monomer-bound radical rapidly reduces a diaryliodonium salt or a dialkylphenacylsulfonium salt, and the resulting monomer-centered cations initiate the polymerizations of epoxides, vinyl ethers, and heterocyclic compounds. Onium salts with high reduction potentials, such as triarylsulfonium salts, do not undergo sensitization by this new system.

The quarternary phosphonium salt Bu4PBr shows to be the most efficient catalyst for the title ring opening reaction.

Pyridinium-type salts containing an N-ethoxy group belong to the family of onium salts and are photoinitiators appropriate for the polymerization of monomers such as oxiranes and vinyl ethers which are not polymerizable by a free radical mechanism. The initiation is accomplished by direct or indirect (sensitized) photolysis of the onium ion, with the former being restricted to the wavelength range of self absorption, the latter being applicable at wavelengths of visible light, An additionally useful tool, namely free radical-mediated generation of initiating species enlarges the versatility of pyridinium salts as photoinitiators. In this connection, the oxidation of free radicals by pyridinium-type ions and the free radical-induced fragmentation of alkoxy pyridinium ions are addressed in this article. Moreover, an interesting application is noted concerning the synthesis of novel block copolymers with the aid of the onium salt-based photopolymerization technique.

EmrE is an Escherichia coli multidrug transporter that confers resistance to a variety of toxins by removing them in exchange for hydrogen ions. The detergent-solubilized protein binds tetraphenylphosphonium (TPP(+)) with a K(D) of 10 nM. One mole of ligand is bound per approximately 3 mol of EmrE, suggesting that there is one binding site per trimer. The steep pH dependence of binding suggests that one or more residues, with an apparent pK of approximately 7.5, release protons prior to ligand binding. A conservative Asp replacement (E14D) at position 14 of the only membrane-embedded charged residue shows little transport activity, but binds TPP(+) at levels similar to those of the wild-type protein. The apparent pK of the Asp shifts to5.0. The data are consistent with a mechanism requiring Glu14 for both substrate and proton recognition. We propose a model in which two of the three Glu14s in the postulated trimeric EmrE homooligomer deprotonate upon ligand binding. The ligand is released on the other face of the membrane after binding of protons to Glu14.

The story of the discovery and development of onium salt photoinitiators for cationic polymerization is chronicled. The chemistry of the synthesis of these compounds is outlined, and the mechanisms of their initiation are discussed briefly. Among the most useful of these types of photoinitiators are diaryliodonium and triarylsulfonium salts, which are used widely for photoinduced cationic crosslinking reactions. From the very beginning, onium salt photoinitiated cationic polymerizations have found use in a multitude of practical applications. Specifically discussed in this article are the use of onium salts in coatings, adhesives, printing inks, release coatings, stereolithography, holographic recording, photocurable composites, and microelectronic photoresists. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4241–4254, 1999

The addition reaction of oxiranes (15a-d) with carbon dioxide (CO2) was carried out using 1 mol % of soluble polymer-supported quaternary onium salts as catalysts under atmospheric pressure. The reaction of 15a-d with CO2 proceeded very smoothly to give the corresponding five-membered cyclic carbonates (16a-d) in high yields at 90-100°C. The catalytic activity of the soluble polymer-supported quaternary onium salts was strongly affected by the following factors: kind of reaction solvent, degree of introduction of the pendant onium salt residues in the polymer chain, and type of alkyl group on the onium salts due to the balance between lipophilicity and steric hindrance of the onium salt residue. Furthermore, these soluble polymer-supported quaternary onium salts were found ordinarily to have higher catalytic activity than low molecular weight quaternary onium salts under the same reaction conditions. It was also found that the rate of reaction was proportional both to catalyst concentration and to oxirane concentration. © 1995 John Wiley & Sons, Inc.

The synthesis of a series of monomers containing isopropenylphenoxy groups was carried out. On irradiation with UV light in the presence of onium salt photoacid generators, these monomers undergo a chain extension reaction consisting of a dimerization followed by a Friedel-Crafts ring closure which results in the formation of polymers with indane groups in the backbone. Aryl imide-containing monomers bearing isopropenylphenoxy groups were also shown to undergo facile photoinduced cationic polymerization. The resulting polymers displayed excellent thermal stability. © 1995 John Wiley & Sons, Inc.

The conversion of the onium salt (III) into the title compounds involves Knoevenagel condensation with aromatic aldehydes, Michael addition with phenylhydrazone (III) and cleavage from the support using triethylamine in ethanol.

The aim of this study was to identify the significant sites of action of cadmium on oxidative phosphorylation in potato tuber mitocondria. We simplified the system to three convenient subsystems linked via the production or consumption of a common intermediate, namely protonmotive force. The three subsystems were substrate oxidation, which produces protonmotive force, and the proton leak reactions and the phosphorylation reactions, which consume protonmotive force. By measuring the effect of cadmium on the kinetic response of each subsystem to protonmotive force (top-down elasticity analysis), we found that cadmium stimulated proton leak reactions and strongly inhibited substrate oxidation, but had no measurable effect on the phosphorylation reactions. Cadmium therefore decreases the amount of ATP produced/oxygen consumed (the effective P/O ratio) not by inhibiting the phosphorylation reactions directly, but by inhibiting the production of protonmotive force and by diverting proton flux from phosphorylation reactions to the proton leak reactions.

Fluorinated (FKM) vulcanizates were treated by immersing in an aqueous solution of triazine thiols, NaOH, and onium salts for 15–60 min at 50–95°C (W-Method). Treated FKM vulcanizates further were postcured in an air oven for 20 h at 200°C to complete the reaction. The onium salt of triazine thiols were found to be formed by a reaction among the triazine thiols, NaOH, and onium salts and to act as cross-linking agents to the surface of FKM vulcanizates. In the acetone solution of onium salts of triazine thiols, FKM vulcanizates were also treated by immersing for a few minutes at 20°C and then by heating in an air oven for 20 min at 200°C (A-Method). Triazine thiols were introduced as crosslinks onto the FKM backbone. The degree of cross-linking in the surface increased by these treatments and the depth of cross-linking reached up to about 40 μm thickness by control of treating conditions. The coefficient of friction in FKM vulcanizates decreased as a result of the surface treatment up to about 0.5 from 2.6. FKM vulcanizates decreased the tensile strength by these surface treatments because of the generation of cracks on the surface at 50% or 100% elongation. The surface treatment of FKM vulcanizates suppressed markedly the fixing between FKM vulcanizates and stainless steel at 150°C. Especially, the A-Method was very effective treating for retarding the fixing between FKM vulcanizates and metals. © 1994 John Wiley & Sons, Inc.

The compound (I) is employed successfully as soluble support for the synthesis of the naphthopyrans (IV).

An investigation of the excited state processes in a three-component initiating system based on a new ketone/amine/onium salt combination has been carried out for the first time. The results obtained through time-resolved laser spectroscopy and the data gained in radical photopolymerization experiments suggest that the addition of an onium salt to the usual ketone/amine system mostly result in a decrease of the termination reaction of the growing macromolecular chains, thus allowing an increase of the rate of polymerization. © 1993 John Wiley & Sons, Inc.

A phase-separated epoxy blend containing a sulfonium salt cationic photoinitiator was studied. The onium salt was found to be preferentially soluble in one of the resins of the system. Scanning electron microscopy and microprobe analyses were done to determine the concentration distribution in the phases and the results compared to a model based on liquid extraction distribution coefficient behavior. Finally, the photolithographic behavior of various blends of the epoxy resins is discussed and the results compared to the behavior predicted by the photoinitiator distribution. © 1993 John Wiley & Sons, Inc.

The addition reaction of oxiranes with CO 2 was performed using insoluble polystyrene beads containing pendant quaternary ammonium or phosphonium salts as catalysts under atmospheric pressure. The reaction of oxiranes with CO 2 proceeded smoothly catalyzed by 1-2 mol % of the polymer-supported quaternary onium salts to give the corresponding cyclic carbonates in high yields at 80-90°C. The catalytic activity of the polymer-supported quaternary onium salts was strongly affected by the degree of ring substitution of the onium salt residues to the polymer, the degree of crosslinking of the polystyrene beads, the hydrophobicity of of the alkyl group on the onium salts and the kind of onium salt

The primary objective of this chapter is to provide a review of the topic of photochemically stimulated electron transfer bond cleavage reactions for approximately the past ten years. PET stimulated bond cleavage reactions are an important way to initiate radical and/or ionic chemistry that can be used in synthesis, imaging, photocuring, and photoresist chemistry. Several inter- and intramolecular photochemical single electron transfer (SET) induced bond cleavage reactions will be reviewed which result from either one-electron oxidation or one-electron reduction. A discussion of onium salt systems that undergo bond cleavage as a direct result of photochemical excitation of an electron from a π highest occupied molecular orbital (HOMO) to a σ* lowest unoccupied molecular orbital (LUMO) will also be provided. Examples of intramolecular rearrangement in, for example, aryldialkylsulfonium salts systems are also discussed. Although, most photochemical SET bond cleavage reactions occur in a stepwise manner through an ion-radical intermediate, if the initial substrate is uncharged, future trends in this field involve the use of concerted bond cleavage processes to eliminate energy wasting back electron transfer.

Hydrodehalogenation of polyhalogenated aromatics with Pd/C catalyst carried out in the presence of a quaternary onium salt follows zero-order kinetics in the substrate and first-order kinetics in the Pd/C catalyst; the related rate constants were determined for o-, m- and p-bromotoluenes, o-, m- and p-chloroalkylbenzenes (methyl, ethyl, and propyl derivatives), and other aryl halides. Reaction rates, depending on the aromatic to be reduced, may be strongly enhanced by the presence of quaternary onium salts: the isomeric chloroethylbenzenes were reduced SO times faster when operating in the presence of Aliquat 336 (1). Also the hindered 2-chloro-m-xylene easily yielded m-xylene

A variety of phosphonium salts have designed as new onium salt hosts and their ability to include phenols as guests has been studied. High inclusion ability was demonstrated by the salts together with high molecular recognition ability in the inclusion complex.

The tandem Michael-aldol reaction of 1-[2-(methylsulfanyl)phenyl]prop-2-en-1-one (1) or the seleno congener 4 with p-nitrobenzaldehyde in the presence of BF3·Et2O gave the Baylis–Hillman adduct 2 or 5 and onium salt 3 or 6, respectively, and selenochromanone 7 from 4.

The principle of chemical amplification has proven to be successful for the design of highly sensitive, high resolution resist material. In many cases a strong Broensted acid, generated by photolysis of onium salt precursors, has been used to catalytically cleave an acid labile blocking moiety. A new approach to negative tone resist is based on acid catalyzed cleavage of acetal blocked aromatic aldehydes, which act as «latent electrophiles» and, under the influence of strong acid, react with the surrounding phenolic resin

t-Butyloxycarbonyl (t-BOC) blocked compounds based on the protection of phenolic groups, e.g. poly-4-hydroxystyrene derivatives, Bisphenol A type dissolution inhibitors, or onium salt photoacid generators, have found widespread research interest for photoresist systems with excellent photosensitivity and high resolution power. We have made an extension of this approach using new phenol type polymers. This contribution presents first details on the chemistry of these systems and results of their lithographic evaluation as positive tone photoresists for deep UV applications

The study of a photoresist containing poly(p-trimethylsiloxystyrene) (1, poly[1-(4-trimethyl-siloxyphenyl)ethylene]) mixed with (C6H5)3SAsF6, which could be employed in a bilevel pattern-transfer process, is reported. The onium salt undergoes efficient photolysis under UV radiation, to generate strong acids, responsible of the cleayage of the silicon-containing side groups. The first results obtained show that this kind of resist could be used in microlithography, because it displays a very good sensitivity to deep UV and an excellent resistance to oxygen plasma. The syntheses of the compounds and substances used in this work are described.

The cooperative asymmetric catalysis of chiral tetraaminophosphonium carboxylate (P,S)-1·OCOR has been established, and its synthetic utility has been successfully demonstrated by application to the highly enantioselective direct Mannich-type reaction of azlactones with N-sulfonyl imines. The present study stimulates the cultivation of the potential of the chiral quaternary onium salt catalysis by the structural modification of organic anion.

The exposure of photoinitiators contained in novolac layers, which give protonic or Lewis acids by irradiation, leads to the degradation of these resins. Benzylic carbocations are formed as intermediates, which can be detected by their long wavelength absorptions between 525 and 545 nm. These intermediates react either with nucleophiles (e.g. anions, water) to benzyl derivatives, or with phenols to novolacs (back reaction), or they yield, under abstraction of protons, ortho-quinone methides, also coloured (absorption maxima at ∼400 nm). Altogether, a complicated system of competitive reactions occurs and, therefore, kinetic calculations are very difficult. Due to changes caused in solubility, this photoinduced degradation of novolacs can be used for photolithographic purposes. But problems arise in negative working resists using novolac resins as polymeric binders. Die Belichtung von Photoinitiatoren, deren Photoreaktionen Protonen- oder Lewis-Sauren liefern, in Novolakschichten fuhrt zu einem Abbau dieser Harze. Intermediar werden benzylische Kationen gebildet, die durch ihre langwelligen Absorptionen zwischen 525 und 545 nm detektierbar sind. Diese Zwischenprodukte reagieren entweder mit Nucleophilen (z. B. Anionen, Wasser) zu Benzylderivaten, oder mit Phenolen zu Novolaken (Ruckreaktion), oder sie ergeben unter Protonenabspaltung ebenfalls gefarbte ortho-Chinonmethide (Absorptionsmaxima bei ∼ 400 nm). Insgesamt resultiert ein kompliziertes System von Konkurrenzreaktionen, so das kinetische Auswertungen erschwert werden. Infolge der damit verbundenen Loslichkeitsveranderungen kann der photoinduzierte Abbau von Novolaken fur photolithographische Anwendungen genutzt werden. In Negativ-Photoresists, die Novolake als polymere Bindemittel enthalten, wirkt sich dieser Prozes aber nachteilig aus.

By using an ammonium chloride salt as water solubilizing moiety, our onium salt supported organic synthesis strategy was extended to water as a solvent. This method allows for high loading capacities both of the supports and their solutions owing to low molecular weight of the onium salts and simplified purification steps as well.

Chiral tetraaminophosphonium salts 1 possessing the phosphorus-centered [5.5]-spirocyclic core have been designed and synthesized in a single step from l-valine-derived diamine. The three-dimensional molecular structure was successfully verified by the single-crystal X-ray diffraction analysis, which also identified a secondary interaction between the phosphonium cation and chloride ion via double hydrogen-bonding. The potential of this novel onium salt as a chiral organic molecular catalyst has been demonstrated in an application to asymmetric direct Henry reaction.

The results of high-pressure variable-temperature and variable ionizing electron energy studies of gas-phase ion-molecule reactions of dimethyl ether in krypton are presented. Near the ionization threshold a series of peaks corresponding to (CH 3 OCH 3 ) n H + (n=1−4) clusters are observed. At higher ionizing electron energies, two new series of peaks appear, corresponding to [CH 3 OCH 2 ] + (CH 3 OCH 3 ) n and [(CH 3 ) 3 O] + (CH 3 OCH 3 ) n clusters. The onium ion, [(CH 3 ) 3 O] + , has been previously reported at elevated temperatures under methane chemical ionization conditions. It was suggested that the onium ion is formed by reaction of (CH 3 ) 2 OH + with CH 3 OCH 3 with subsequent elimination of methanol, i.e. by fragmentation of an adduct ion. The present results strongly suggest that, under our conditions, [CH 3 OCH 2 ] + rather than thermal (CH 3 ) 2 OH + , is the precursor to [(CH 3 ) 3 O] +