31704-80-0Relevant articles and documents
THE EFFECT OF SIDE CHAIN SUBSTITUENTS ON THE INTRAMOLECULAR DIELS-ALDER REACTION OF THE FURAN DIENE: THE SYNTHESIS OF (+/-)-1,4-EPOXYCADINANE
Rogers, Christine,Keay, Brian A.
, p. 1349 - 1352 (1989)
The effect of side chain substituents on the Intramolecular Diels-Alder reaction of the Furan diene (IMDAF) is reported in which the side chain connecting the furan diene to the dienophile contain four carbon atoms.The synthesis of 1,4-epoxycadinane utili
Influence de la pression sur les reactions de substitution electrophile du furanne et de methyl-2 furanne
Jenner, Gerard,Rimmelin, Jean,Antoni, Francois,Libs, Suzanne,Schleiffer, Elisabeth
, p. 65 - 70 (2007/10/02)
We previously investigated the (4+2) cycloaddition reactions of 2-methylfuran, which are known to be very difficult, even impossible, under the usual conditions for Diels-Alder reactions.We found that the adducts are generated only at low temperatures (20-40 deg C) and high pressures (ca. 10 kbar)(Bull.Soc.Chim., 1978, p.461).However, by increasing the temperature, we have observed the alternative reaction consisting in the α-substitution of furan when furan compounds are allowed to react with α,β-unsaturated carbonyl compounds at temperatures above 100 deg C.We found that this reaction, which proceeds slowly (or not at all) at atmospheric pressure, is noticeably faster at high pressures.Having in mind a simple method for facile synthesis of mono- and disubstituted furans, we thought that pressure could be an interesting parameter in producing such compounds in high yield.Additionally, since the reaction was found some time ago to be very sensitive to acidic media (electrophilic substitution of the Friedel-Crafts type), we imagined that a possible pressure induced creation of charges in the transition state would give rise to an electrostriction contribution to the reaction rate.We first investigated the thermal synthesis without catalyst and found that only unsaturated carbonyl compounds show some reactivity, while unsaturated nitriles or esters do not react.However, the substitution reaction is considerably perturbed by the polymerisation reaction, which is also positively influenced by pressure and thus reduces drastically the yield of substituted products, except in some rare cases.The use of a suitable catalyst (AcOH-H2O) combined with pressure (3 000 bar) allows satisfactory yields of substituted furans with little formation of polymer.The pressure kinetics of two selected reactions reveals a strong pressure acceleration with activation volumes in the range (-45 to -50 cm3/mol) independent of the solvent.We suggest that starting from a neutral initial state, during the activation process there is a development of electrostriction with the possible appearance of strongly polarized species, the polarization being enhanced by pressure.However, in this case we would normally anticipate a solvent dependence of the activation volume ΔV(excit.); in fact this effect is not observed.Nevertheless, the hypothesis of electrostriction is quite plausible by the fact that, when the reaction is carried out in the presence of the catalyst (AcOH-H2O), the value ΔV(excit.) is reduced to half the former value (-24.5 cm3/mol), because the initial state is no longer neutral and charges are present along the activation process.
2,9-DIOXABICYCLONONAN-DARSTELLUNG, MASSENSPEKTROSKOPIE UND UMLAGERUNG EINES NEUEN HETEROCYCLISCHEN SYSTEMS
Francke, Wittko,Reith, Wolfgang
, p. 2029 - 2032 (2007/10/02)
Nine different methyl-substituted compounds of a new acetal system 5 are synthesized from 4-(5-methyl-2-furyl)alkanoles 1 and are rearranged to ketones 6; mass spectroscopic fragmentation patterns are described.
