Cyanide-Free One-Pot Synthesis of Methacrylic Esters from Acetone

Methacrylic esters, represented by methyl methacrylate (MMA), are widely used as commodity chemicals. Here, the one-pot synthesis of methacrylic esters from acetone, a haloform and alcohols in the presence of an organic base is described. Using DBU as the organic base for the reaction of acetone, chloroform and methanol in acetonitrile afforded MMA in 66 % yield. When the solvent was replaced by benzonitrile, the product MMA was successfully purified by distillation. Applicability of this process to various alcohols was also investigated to show ethyl, phenyl, CF₃CH₂, and n-C₆F₁₃CH₂CH₂ esters were obtained in moderate yields. The use of bromoform instead of chloroform resulted in the improvement of the yield, for example, methyl and n-C₆F₁₃CH₂CH₂ esters up to 81 and 70 %, respectively. The reaction with deuterated starting materials acetone-d₆ and MeOH-d₄, with DBU in acetonitrile afforded deuterated MMA (MMA-d₈) in 70 % yield.     

The Haloform Reaction in the Presence of Cyclodextrins

Cyclodextrins act as inverse phase transfer catalystsin the oxidation of methyl ketones by hypochloride(the haloform reaction). The reaction is affected by thechoice and the amount of cyclodextrin. The reactionproceeds under mild reaction conditions and itprovides only the corresponding carboxylic acid asreaction product. No organic solvent is required.     

Synthesis and characterization of carboxylic acid‐terminated polyisobutylenes

tert-Chloride-terminated polyisobutylenes (PIB) (1020 ≤ M_n ≤ 6700 g/mol) were dehydrochlorinated nonregiospecifically using basic alumina, or regiospecifically either via potassium tert-butoxide or in situ quenching of quasiliving PIB. Olefin-terminated PIBs were quantitatively ozonized at −78 °C using hexane/methylene chloride/methanol, 62/31/7 (v/v/v) cosolvents, and an ozone generator, employing pure oxygen as source gas. The primary ozonides were reduced using trimethyl phosphite to yield pure PIB methyl ketone from exo-olefin PIB, and a mixture of PIB methyl ketone and PIB aldehyde from mixed olefin-PIB. PIB methyl ketone was oxidized to carboxylate via the haloform reaction; titration revealed near-quantitative functionalization, but the reaction was slow. Tetrahalomethane oxidation was identified as a preferred alternative method, and was conducted using either CCl₄ as the reaction solvent, THF as the solvent with CCl₄ in reagent amounts, or hexane as the solvent with a phase-transfer catalyst and CCl₄ in reagent amounts. The system using hexane, with tetra-n-butyl ammonium chloride as phase-transfer catalyst, showed complete conversion in ∼ 4 h. PIB carboxylic acid was recovered by acidification and isolation. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3229–3240, 2008     

Synthesis of methyl epijasmonate and cis-3-(2-oxopropyl)-2-(pent-2Z-enyl)-cyclopentan-1-one

A novel and efficient synthesis of both (±)-methyl epijasmonate and (±)-cis-3-(2-oxopropyl)-2-(pent-2Z-enyl)-cyclopentan-1-one is described. The key step to establish the cis-stereochemistry on the 5-membered ring is an ionic Diels–Alder reaction, which is high yielding and highly regioselective. Subsequent key steps include oxidative cleavage of the six-membered ring, Wittig coupling and for the synthesis of epijasmonate, the haloform reaction.     

p-carboxylation of linear high molecular-mass polystyrene

A simple method is reported for the post-polymerization partial p-carboxylation of linear polystyrene without degradation or crosslinking of the polymer. The method is based on Friedel–Crafts acetylation of the polystyrene under mild conditions, followed by oxidation of the acetyl groups by means of a phase-transfer-catalyzed haloform reaction. The method is well suited for the synthesis of high molecular mass, monodisperse ionomers with p-carboxylate groups situated randomly along the polystyrene chain. © 1993 John Wiley & Sons, Inc.