Solvent-free Diels Alder Reaction Research Articles

Synthesis of woody oil-based plasticizer via solvent-free Diels-Alder reaction and its biodegradability

Woody oil is extracted from the fruits or seeds of woody plants . Preparing woody oil based and biodegradable plasticizer via solvent-free Diels-Alder reaction can reduce plasticizer enrichment and pollution, as well as dependence on petrochemical resources. Herein, woody oil based plasticizer (TOP-Ⅰ and TOP-Ⅱ) were successfully synthesized from renewable woody oil via solvent-free Diels-Alder reaction. Chemical structure of TOP-Ⅰ and TOP-Ⅱ was characterized with 1 H NMR, Biodegradation of TOP-Ⅱ was investigated in active soil and digestive system of Tenebrio molitor . Degradation products were extracted from active soil and Tenebrio molitor feces, the results showed that TOP-Ⅱ experienced biodegradation and formed degradation components with low molecular weight substances. The insect degradation of bio-based plasticizers was first reported and provided an effective way to reduce plasticizer enrichment and pollution. In addition, TOP-Ⅰ and TOP-Ⅱ was used to replace petroleum-based and non-degradable dioctyl phthalate (DOP) in plasticized poly(vinyl chloride) (PVC). The obtained plasticized PVC with TOP-Ⅰ and TOP-Ⅱ showed improved thermal stability, aging resistance, plasticization and solvent extraction resistance, the related mechanism behind these performances were also explored. • Biodegradable plasticizers could reduce plasticizer enrichment and pollution. • Woody oil based plasticizer was synthesized via solvent-free Diels-Alder reaction. • The bio-based plasticizer was degradable with active soil and Tenebrio molitor. • Plasticized PVC with woody oil based plasticizers had excellent properties. • The bio-based plasticizer might replace petro-based or non-degradable plasticizer.

Solvent-free Diels–Alder reactions catalyzed by FeCl3 on Aerosil® silica

A mild solvent-free protocol for the promotion of the Diels–Alder reactions of simple dienes and p-benzoquinones, catalyzed by a mixture of iron(III) chloride on Aerosil® silica is reported.

A solvent-free Diels-Alder reaction of graphite into functionalized graphene nanosheets.

A solvent-free Diels-Alder reaction was carried out by heating a mixture of graphite and a typical dienophile, maleic anhydride (MA) or maleimide (MI), in a sealed glass ampoule of argon. The functionalization of graphite with dienophiles was confirmed by various characterization techniques, suggesting the efficient functionalization and delamination of graphite into a few layers of graphitic nanosheets.

Mechanochemical milling promoted solvent-free imino Diels–Alder reaction catalyzed by FeCl3: diastereoselective synthesis of cis-2,4-diphenyl-1,2,3,4-tetrahydroquinolines

Cis-2,4-diphenyl-1,2,3,4-tetrahydroquinolines were diastereoselectively synthesized by FeCl3-promoted solvent-free Diels–Alder reaction of in situ generated imine with styrene under ball milling.

Synthesis of the bicyclo[6.2.1]undecane ring system by a solvent-free Diels–Alder reaction

A bicyclo[6.2.1]undecane model compound of the core structure of the biologically active furanoheliangolide sesquiterpene was synthesized. This new and short route was developed by using a solvent-free Diels–Alder reaction between cyclopentadiene and 3-nitro-2-cyclohexenone, followed by simple transformations. Theoretical calculations were performed in order to understand reactivity aspects of the cycloaddition.

Solvent-Free Diels–Alder Reaction in a Closed Batch System

Abstract Solvent-free Diels–Alder reactions were carried out by heating a mixture of a volatile diene, such as 1,3-butadiene, isoprene, or 2,3-dimethyl-1,3-butadiene, and a dienophile, such as methyl vinyl ketone, methyl acrylate, or maleic anhydride, in a closed batch reactor. High yields of Diels–Alder products were obtained without using solvents and catalysts within a short reaction time in most of the reactions. In particular, several reactions of dienophiles with 1,3-butadiene, which is known as a diene with low reactivity because of its gaseous form, also proceeded with high yields of Diels–Alder products in the closed batch reactor under conditions pressured by the reactant vapor. Solvent-free reactions provided high yields compared to reactions in solvent since the reaction heat directly resulted in increasing the reaction temperature and pressure. Energy in the exothermic reaction was used effectively in the closed batch system under solvent-free conditions.

Demonstration of a Runaway Exothermic Reaction: Diels–Alder Reaction of (2E,4E)-2,4-Hexadien-1-ol and Maleic Anhydride

In a demonstration that involves a solvent-free Diels–Alder reaction of (2E,4E)-2,4-hexadien-1-ol and maleic anhydride, one can use relatively small quantities of reactants to illustrate the process of scaling up a solvent-free reaction, including consideration of reactivity of the starting substances, scale of the reaction, and size and shape of the reaction vessel. Upon being mixed, the two solid compounds form a melt and react in the liquid phase to form a solid product. In a 50 mL beaker on a 5.00 mmol scale, the reaction was relatively uneventful. However, an increase to a 10.00 mmol scale in the same size beaker resulted in a vigorous exothermic reaction, which produced dark insoluble syrupy material. When water was added to the reaction mixture, the reaction was faster, with only a modest increase in the reaction temperature and 1,3,3a,4,5,7a-hexahydro-5-methyl-3-oxo-4-isobenzofurancarboxylic acid was obtained as a pure white solid. The demonstration may help students understand the role of solvents in organic reactions, why most reactions are carried out in solvents, as well as potential problems that may be encountered when developing solvent-free reactions.

Solvent-free Diels–Alder reactions of in situ generated cyclopentadiene

A solvent-free Diels–Alder reaction was carried out by heating a mixture of dicyclopentadiene and a dienophile. Cyclopentadiene, formed in situ, reacted with the dienophile in a thermodynamically controlled reaction. Besides being solvent-free, the described procedure allows for almost complete utilization of dicyclopentadiene and avoids handling of noxious and hazardous cyclopentadiene. The reaction worked well with dienophiles such as maleic anhydride and unsaturated esters. However, unsaturated acids were not suitable dienophiles, yielding Diels–Alder adducts in a low yield.

Entrapment of cyclopentadiene in zeolite NaY and its application for solvent-free Diels–Alder reactions in the nanosized confined environment

Nonpolar cyclopentadiene was stably entrapped as a monomer in the hydrophilic supercages of zeolite NaY. A monomer form of cyclopentadiene in the supercages was confirmed by 13C MAS NMR spectroscopy. The adsorbed cyclopentadiene in the confined cavities performed the Diels–Alder reaction with typical dienophiles under solvent-free conditions more effectively than in organic and water media.