57466-12-3Relevant academic research and scientific papers
Photochemical acetalization of carbonyl compounds in protic media using an in situ generated photocatalyst
De Lijser, H.J. Peter,Rangel, Natalie Ann
, p. 8315 - 8322 (2007/10/03)
Carbonyl compounds are conveniently converted into their corresponding dimethyl acetals in good yields and short reaction times by means of a photochemical reaction in methanol with a catalytic amount of chloranil (2,3,5,6-tetrachloro-1,4-benzoquinone, CA) as the sensitizer. Using aldehydes gives better results than using ketones, which also tend to form enol ethers as side products. These results are similar to those of simple acid-catalyzed acetalization reactions, suggesting the involvement of a photochemically generated acid. On the basis of steady state and laser flash photolysis data the reaction is proposed to involve the in situ generation of a photocatalyst (2,3,5,6-tetrachloro-1,4-hydroquinone, TCHQ) via reaction of CA with the solvent. The acetalization process is initiated by ionization of TCHQ, followed by loss of a proton to the solvent or the carbonyl, which starts a catalytic reaction. The photocatalyst is regenerated via a disproportionation reaction.
Elimination-addition mechanism for nucleophilic substitution reaction of cyclohexenyl iodonium salts and regioselectivity of nucleophilic addition to the cyclohexyne intermediate
Fujita, Morifumi,Kim, Wan Hyeok,Sakanishi, Yuichi,Fujiwara, Koji,Hirayama, Sayaka,Okuyama, Tadashi,Ohki, Yasuhiro,Tatsumi, Kazuyuki,Yoshioka, Yasunori
, p. 7548 - 7558 (2007/10/03)
The reaction of 4-substituted cyclohex-1-enyl(phenyl)iodonium tetrafluoroborate with tetrabutyl-ammonium acetate gives both the ipso and cine acetate-substitution products in aprotic solvents. The isomeric 5-substituted iodonium salt also gives the same mixture of the isomeric acetate products. The reaction is best explained by an elimination-addition mechanism with 4-substituted cyclohexyne as a common intermediate. The cyclohexyne formation was confirmed by deuterium labeling and trapping to lead to [4 + 2] cycloadducts and a platinum-cyclohexyne complex. Cyclohexyne can also be generated in the presence of some other mild bases such as fluoride ion, alkoxides, and amines, though amines are less effective bases for the elimination. Kinetic deuterium isotope effects show that the anionic bases induce the E2 elimination (k H/kD > 2), while the amines allow formation of a cyclohexenyl cation in chloroform to lead to E1 as well as SN1 reactions (k H/kD ≈ 1). Bases are much less effective in methanol, and methoxide was the only base to efficiently afford the cyclohexyne intermediate. Nucleophiles react with the cyclohexyne to give regioisomeric products in the ratio dependent on the ring substituent. The observed regioselectivity of nucleophilic addition to substituted cyclohexynes is rationalized from calculated LUMO populations, which are governed by the bond angles at the acetylenic carbons: The less deformed carbon has a higher LUMO population and is preferentially attacked by the nucleophile.
A novel electrophilic methoxylation (with a little help from F2)
Rozen, Shlomo,Mishani, Eyal,Kol, Moshe
, p. 7643 - 7645 (2007/10/02)
Methyl hypofluorite, MeOF, easily made from MeOH and F2, proved to be an excellent source for the novel electrophilic methoxylium ion "MeO+". MeOF was reacted with the enol forms of carbonyls, producing in good to excellent yields the corresponding α-methoxy carbonyl derivatives. It was found that the methoxylation is best carried out on methyl enol ethers. Silyl enol ethers and enol acetates were also tested but with limited success. The reaction proceeds through an addition elimination mechanism.
Rh(I) COMPLEXES CONTAINING FULLY ALKYLATED MONO- AND DIPHOSPHINE LIGANDS AS HIGHLY ACTIVE HYDROGENATION CATALYSTS FOR CARBONYL COMPOUNDS
Tani, Kazuhide,Suwa, Kenichi,Tanigawa, Eiji,Yoshida, Toshikatsu,Okano, Tamon,Otsuka, Sei
, p. 261 - 264 (2007/10/02)
Our search for highly active hydrogenation catalysts for carbonyl compounds, starting with neutral Rh(I) hydride complexes, (R=i-Pr, n=3; R=Cy, n=2), has led to the discovery of cationic Rh(I) complexes with fully alkylated diphosphine ligands, ClO4 (n=3,4).These compounds prove to be versatile and efficient for hydrogenation of a variety of carbonyl compounds, including aldehydes.
A FACILE PREPARATION OF METHYL ENOL ETHERS FROM ACETALS AND KETALS USING TRIMETHYLSILYL IODIDE
Miller, R.D.,McKean, D.R.
, p. 323 - 326 (2007/10/02)
Acetals and ketals are converted in high yields to the corresponding methyl vinyl ethers by treatment with trimethylsilyl iodide in the presence of hexamethyldisilazane at room temperature or below.
