Vinyl Ether Derivatives Research Articles

Reaction of diketene-acetone adduct with enamines, ketene acetals, vinyl ethers, and .BETA.-diketones.

Diketene-acetone adduct (1) generates acetylketene (2) under heating. In order to compare the reactivity of 2 with that of diketene, the reaction of 1 with electron-rich olefins was investigated. On heating with 1, primary enamines (3a-d) produced the corresponding 3-substituted 2, 6-dimethyl-4 (1H)-pyridones (4a-d), while the tertiary enamine 3e gave the 4-pyrone derivative (7). The reaction of 1 with ketene acetals (8) gave the 2, 2-diethoxy-2, 3-dihydro-4-pyrone derivatives (9). The vinyl ether derivatives 13 similarly reacted with 1 to give the 4-pyrone derivative 15 or 16 as the major product. The result shows that both diketene and 2 react with electron-rich olefins in a similar manner.

Electrochemical oxidation of alkyl-substituted allenes in methanol

Mono-, di- and tri-alkyl-substituted allenes were potentiostatically oxidized in methanol at graphite and Pt anodes. At the former electrode, α-methoxylated ketones (due to 4F/mole electricity consumption) and esters (6F/mole) were the major products. At a Pt anode, intermediate products such as vinyl-ether derivatives (2F/mole) were characterised too. Unlike the anodic oxidation of alkenes and alkynes previously reproted in the literature, dimerisation is not a typical process in the allenes' oxidation, since of all the products obtained only a sole dimer has been observed. The mechanism for the formation of most products is discussed.

Reaction of aryl chromium carbene complexes with ethyl propiolate a versatile vinyl ether formation

Arylmethoxychromium-carbene complexes reacted with ethyl propiolate in the presence of alcohol to form and yields of aryl vinyl ether derivatives of malonate.

Aliphatic claisen rearrangement promoted by organoaluminium compounds

Treatment of allyl vinyl ether derivatives with organoaluminiumamphoteric reagent, R 3Al or R 2AlSPn, results in the title reaction at room temperature under uptake of R, H, or SPh as a nucleophile on the aldehydic carbon.

Prodrug Approach to Enhancement of Rate of Dissolution of Allopurinol

The synthesis and physicochemical characteristics of l-ethoxyethyI-4-allopurinyl ether and 2-tetrahydropyranyl-4-allo- purinyl ether are described. These compounds have lower melting points, higher solubilities, and, consequently, considerably greater rates of dissolution than does allopurinol. The rate of hydrolysis of the ethyl vinyl ether derivative was examined at 37° in 1 and 0.1 N HC1, yielding half-lives of 13sec and 7.7 min, respectively, for the pseudo-first-order hydrolysis to form allopurinol. The rate of hydrolysis of the tetrahydropyran derivative was somewhat slower; i.e., the half-lives were 35sec and 12 min, respectively, under the same conditions.

Cationic Copolymerization of 2-Chloroethyl Vinyl Ether with Styrene Derivatives. III. Solvent and Catalyst Effects on Relative Reactivity

Abstract The change in relative reactivity in the cationic copolymerization of 2-chloroethyl vinyl ether and styrene derivatives was investigated with various catalysts and solvents. p-Methoxystyrene, p-methylstyrene, and a-methyl-styrene were used as styrene derivatives. The styrene content in the co-polymer increased when a polar solvent and/or a strong catalyst was used. The change of relative reactivity in the copolymerization of 2-chloroethyl vinyl ether with styrene derivatives was much greater than that in the copolymerization between vinyl ethers or styrene derivatives. When nitro-ethane was used as a solvent, not only the polarity but also the nucleophilicity influenced the copolymer composition. The results were discussed by two energies, Eπ and Ers, which are measures of complex formation between monomer and carbonium ion, and stabilization energy in the transition state, respectively.

Cationic Copolymerization of 2-Chloroethyl Vinyl Ether with Styrene Derivatives. II. Temperature Dependence of Monomer Reactivity Ratios

Temperature dependence of monomer reactivity ratios, r1 and r2, and their product r1×r2 were studied in the cationic copolymerization of 2-chloroethyl vinyl ether (M1) with styrene derivatives (M2) (p-methoxystyrene, p-methylstyrene and α-methylstyrene). Methylene chloride, toluene and benzene were used as solvents, and SnCl4 CCI3CO2H and BF3O(C2H5)2 were used as catalysts, r1 increased and r2 decreased with increasing polymerization temperature in the copolymerization of M1 with M2 except that of Mi with p-methoxystyrene. On the other hand, r1 and r2 hardly depended on polymerization temperature in the copolymerization between vinyl ethers or styrene derivatives. On the basis of these results, the difference in the transition state of the propagation reaction of vinyl ether and styrene derivatives was discussed. Temperature dependence of the products, r1×r2, was investigated and the propagating end effect was discussed in cationic copolymerization.

Cationic polymerization of α,β‐disubstituted olefins. Part 12. Theoretical consideration of the reactivities of vinyl ethers and β‐substituted vinyl ethers

AbstractTo elucidate the propagation mechanism in the cationic polymerization of vinyl ethers and β‐substituted vinyl ethers, the electron distribution in these monomers was computed by the extended Hückel method. Propylene and styrene derivatives were also studied in comparison with the vinyl ether derivatives. Attempts were made to explain the experimental results by various calculated reactivity indices. With the unsaturated hydrocarbons, the reactivity indices on the β‐carbon parallel with the relative reactivity in the cationic polymerization or oligomerization. This agreement suggests that the transition state for the rate‐determining step of the propagation reaction is represented by a model in which the carbonium ion interacts with the β‐carbon of a monomer. On the other hand, the effect of β‐alkyl or alkoxyl groups on the reactivity of vinyl ethers could not be explained by the model in which the carbonium ion interacts with an olefinic carbon or an ether oxygen, or both with two atoms. The following model was proposed on the basis of the electronic stabilization energy due to the de‐ magnified image localization from the occupied orbital of a monomer to the vacant orbital of a carbonium ion. This model can explain reasonably the relative reactivity of vinyl ethers and β‐substituted vinyl ethers observed in the cationic copolymerization catalyzed by BF3·O(C2H5)2.

Methods and Possibilities of Nucleophilic Acylation

AbstractNucleophilic acylation is the attachment of an magnified image group to an electrophilic center. A brief discussion of the advantages offered by acylations of this type in syntheses is followed by a description of the direct methods (reactions with acylmetal compounds) and the methods proceeding via “masked” acyl anions. The latter methods are based on the use of either metalated vinyl ether derivatives or carbanions derived from acetals. Organyllithiums of sulfur‐stabilized carbanions are important reagents of this type.

Synthesis of perfluoroalkyl vinyl ether acids and derivatives

Synthesis of perfluoroalkyl vinyl ether acids and derivatives