A Simple Synthesis of Stable 1,4-Diionic Pyridinium Betaines

Summary.  Protonation of the reactive intermediate produced in the reaction between pyridine and dialkyl acetylenedicarboxylates by strong CH-acids such as N,N′-dimethylbarbituric acid, Meldrum’s acid, or indane-1,3-dione leads to a vinylpyridinium cation which undergoes an addition reaction with the enolate anion of the CH-acid to produce stable 1,4-diionic pyridinium betaines in good yields. Corresponding author. E-mail: isayavar@yahoo.com Received February 5, 2002. Accepted (revised) March 12, 2002     

A Novel Three Component Reaction: The Synthesis of Stable,Highly Functionalized 1,4-Diionic Nitrogen Betaines

The protonation of a highly reactive 1,4-dipole generated in the reaction between pyridine or isoquinoline and dialkyl acetylenedicarboxylates by the acidic C-H group of (ethoxycarbonylmethyl) triphenylphosphonium bromide leads to a vinyl pyridinium cation derivatives, which undergo a carbon-centered Michael type addition with the conjugate base of the CH-acid to produce highly functionalized stable 1,4-diionic nitrogen betaines.     

Stable 1,6-Diionic Phosphorus Betaines Derived from Electron-Deficient Acetylenic Compounds

The addition of triphenylphosphine to methyl propiolate, ethyl propiolate, or ethynyl methyl ketone in the presence of a strong NH-acid, such as 5-nitro-2,4-dihydro-3 H -1,2,4-triazol-3-one, leads to stable 1,6-diionic organophosphorus compounds in excellent yields.     

Preparation and Reactions of Pyridinium Ylids via Decarboxylation of Pyridinium Betaines

Ylids are charged organic compounds with characters differ from regular organic compounds1. Nitrogen ylids, due to their instabilities, are not studied as vastly as phosphorus or sulfur ylids2. Nitrogen ylids are generally obtained by removing proton of the quaternary nitrogen salts with base3,4. In this work, we tried to study the generation of pyridinium ylids 4 via decarboxylation process in neutral condition and study the related reactions with electrophiles. The precursor of pyridiniu…     

Highly Fluorescent Pyridinium Betaines for Light Harvesting

We report the findings of our experimental and theoretical investigations into the properties of pyridinium enolates and their potential utility in light‐harvesting applications, such as in luminescent solar concentrators (LSCs). We present the synthesis, structures, photophysical characterization, and wavefunction‐based quantum‐chemical studies of five cyclobetaines. The performance of an LSC device incorporating one of these cyclobetaines is shown to be comparable to state‐of‐the‐art devices.     

A Convenient Synthesis of Aromatic Fluoride by Thermal Stable Pyridinium Phase-transfer Catalyst

Fluoroorganic compounds have been applied as useful intermediates in industry. Here, we use the PTC method for fluorination of aromatic halide by inorganic fluorides involv- ing a halogen-exchange. This is a convenient and attractive synthetic way to obtain fluoro compounds, because inorganic fluorides such as potassium fluoride is safe to be handled and cheap1. However, owing to poor solubilities of inorganic fluorides in organic solvents, the halogen-exchange fluorination often requires …     

Facile and Green Synthesis of 1,4-Dihydropyridine Derivatives in n-Butyl Pyridinium Tetrafluoroborate

l,4-Dihydropyridine derivatives were synthesized from the one-pot condensation of aldehydes, acetoacetates, and ammonium acetate in room-temperature ionic liquid n-butyl pyridinium tetrafluoroborate ([BPy][BF₄]). Compared with classical Hantzsch reaction conditions, this new method has the advantage of excellent yields, short reaction time, and easy workup. The recovered ionic liquid could be recycled for at least five runs without losing its activity.     

Stereoselective Synthesis of 1,5-Diionic Organophosphorus Compounds

The reactive 1:1 intermediate produced in the reaction between triphenylphosphine and alkyl propiolates or ethynyl phenyl ketone was trapped by isopropylidene Meldrum's acid (5-isopropylidene-2,2-dimethyl-1,3-dioxane-4,6-dione) to produce alkyl 3-(isopropylidenemalonate-5-yl-5-ylid)-3-methyl-2-triphenylphosphoniomethylidene-butanoates or 3-(isopropylidenemalonate-5-yl-5-ylid)-3-methyl-2-triphenylphosphoniomethylidene-butanone in 75-86% yield. These 1,5-diionic phosphorus betaines exist as (Z) geometrical isomer in CDCl 3 solution.     

A Simple Synthesis of Stable Phosphoranes Derived from Imidazole Derivatives

Stable crystalline phosphorus ylides were obtained in excellent yields from the 1:1:1 addition reaction between triphenylphosphine and dialkyl acetylenedicarboxylates, in the presence of strong NH-acids, such as imidazole, 2-methylimidazole, 4-methylimidazole, 2-ethylimidazole, benzimidazole, and 5,6-dimethylbezimidazole. These stable ylides exist in solution as a mixture of two geometrical isomers as a result of restricted rotation around the carbon–carbon partial double bond resulting from the conjugation of the ylide moiety with the adjacent carbonyl group.     

A Simple Synthesis of Stable Heterocyclic Phosphorus Ylides Derived from NH-Acids

Crystalline phosphorus ylides are obtained in excellent yields from the addition reaction between triphenylphosphine, dimethyl acetylenedicarboxylate and strong NH-acids, such as 2-acetylpyrrole, indole, ethyl 3-indolylglyoxalate and N -benzyl-2-pyrrolylglyoxamate. Dynamic NMR effects are observed in the 1 H NMR spectra of stabilized ylides obtained from 2-acetylpyrrole and indole ( j G p = 67.1 and 68.8 kJmol m 1 respectively) and are attributed to restricted rotation around the carbon-carbon partial double bond resulting from conjugation of the ylide moiety with the adjacent carbonyl group.     

A Simple Synthesis of Stable Phosphoranes Derived from Imides or Acetanilide Derivatives

Stable crystalline phosphorus ylides are obtained in excellent yields from the 1:1:1 addition reaction between triphenylphosphine, dialkyl acetylenedicarboxylates, and strong NH-acids, such as acetanilide, 4-methylacetanilide, 2-cyanoacetanilide, 4-bromoacetanilide, 4-methoxyacetanilide, succinimide, malimide, or phthalimide. These stabilized phosphoranes exist as a mixture of two geometrical isomers as a result of restricted rotation around the carbon-carbon partial double bond resulting from conjugation of the ylide moiety with the adjacent carbonyl group.     

A Simple Procedure for Preparing Annulated p-Benzoquinones. Improved Synthesis of 1,4-Dihydro-1,4-methanonaphthalene-5,8-dione

A simple and efficient two-step, one-pot synthesis of substituted 1,4-dihydro-1,4-methanonaphthalene-5,8-diones is reported. This synthesis, which utilizes readily available starting materials and inexpensive reagents, can be used to prepare 1a-1c in 70–90% overall yield. This procedure was extended successfully to prepare a more highly complex annulated p-benzoquinone i.e., 8.     

A Simple Synthesis of Stable Phosphorus Ylides from Indole and Some of Its Derivatives

Stable crystalline phosphorus ylides were obtained in excellent yields from the 1:1:1 addition reaction between triphenylphosphine and dialkyl acetylenedicarboxylates in the presence of strong NH acids, such as indole and 2-methyl indole, 3-methyl indole, and 5-boromo indole. These stable ylides exist in a solution as a mixture of two geometrical isomers as a result of the restricted rotation around the carbon–carbon partial double bond resulting from the conjugation of the ylide moiety with the adjacent carbonyl group.     

A Simple Synthesis of Stable Phosphorus Ylides Derived from 2-Benzoxazolinone and 2-Mercaptobenzoxazole

The reaction of triphenylphosphine with dialkyl acetylenedicarboxylates in the presence of a strong SH-acid or NH-acid, such as 2-mercaptobenzoxazole and 2-benzoxazolinone, has been studied. In some cases, stable phosphorus ylides are obtained in excellent yields. The ylide moiety of these compounds is strongly conjugated with the adjacent carbonyl group, and the rotation about the partial double bond in (E) and (Z) geometrical isomers is slow on the NMR time scale at an ambient temperature. Thus, these exist as a mixture of geometrical isomers.     

A Simple Approach to the Synthesis of 1,4-Bis(arylsulfonyl)tetrahydropyrazine-2,5-diones

Summary.  The addition of triphenylphosphine to dimethyl acetylenedicarboxylate in the presence of arylsulfonylglycyl chlorides leads to 1,4-bis-arylsulfonyl-tetrahydropyrazine-2,5-diones and dimethyl (E)-2-chloro-2-butenedioate. Corresponding author. E-mail: isayavar@yahoo.com Received June 3, 2002; accepted June 10, 2002     

Synthesis and Flocculating Power of Pyridinium Polyelectrolytes

Synthesis of poly(1,2-dimethyl-5-vinylpyridinium methyl sulfate) and its copolymers with hydrophilic monomers by (co)polymerization initiated with water-soluble peroxides is studied. The flocculating activity of polyelectrolytes is determined in aqueous kaolin suspensions and also in dewatering of an active sludge.     

A Simple Propellane Synthesis

A dianion-mediated dialkylation reaction provides ready access to a heterocyclic propellane. The methodology should provide a general entry into a variety of similar systems.