- Calcined and silylated K10 montmorillonites as catalysts of pericyclic reactions of trans-anethole
-
Cation-exchanged K10 montmorillonites are calcined and silylated in order to eliminate acid sites. The solids obtained promote the Diels-Alder reaction of cyclopentadiene with trans-anethole and the cyclodimerization of trans-anethole.
- Fraile,Garcia,Mayoral,Tarnai,Alonso
-
-
Read Online
- [2+2]-cycloaddition reaction of styrene derivatives using an Fe(III) salt catalyst
-
Iron(III) perchlorate catalyzed cyclodimerization of trans-anethole gave trans,anti,trans-cyclobutane stereospecifically in good yield. Alumina supported iron(III) perchlorate was an especially efficient one-electron oxidation reagent.
- Ohara, Hiroyuki,Itoh, Toshiyuki,Nakamura, Masaharu,Nakamura, Eiichi
-
-
Read Online
- Anethole isomerization and dimerization induced by acid sites or UV irradiation
-
The formation of cis-anethole and various dimers as a result of the exposure of trans-anethole to microporous solid acids (dealuminated HY zeolites), or UV-Vis irradiation was established by means of high resolution gas chromatography coupled to mass spectrometry. 3,4-bis-(4-Methoxyphenyl)-(E)-hex- 2-ene was the most abundant compound among eight different methoxyphenyl- disubstituted hexenes produced by electrophilic addition and elimination reactions induced by HY zeolites. (1a,2a,3b,4b)-1,2-bis(4-Methoxyphenyl)-3,4- dimethylcyclobutane was the principal component in the mixture of 5 methoxyphenyl-disubstituted cyclobutanes found, together with cis-anethole, after UV-Vis irradiation of a trans-anethole solution in toluene.
- Castro, Hans T.,Martinez, Jairo Rene,Stashenko, Elena
-
experimental part
p. 5012 - 5030
(2010/10/21)
-
- 1,3-Diketonatoboron difluoride sensitized cation radical reactions
-
Dibenzoylmethanatoboron difluoride (DBMBF2) and allied BF2 complexes interact from their singlet excited state with trans-anethole (t-A), quadricyclene (QC) and norbornadiene (NBD) by electron transfer to generate the corresponding cation radicals, which undergo the reported reactions.By sensitization, t-A undergoes dimerization to form the anti head-to-head and syn head-to-head dimers with retention of stereochemistry.The formation is reversible under sensitization conditions, leading to accumulation of the more stable anti isomer.However, irradiation of the absorption band of the DBMBF2 - t-A ground state complex did not lead to dimerization of t-A.By DBMBF2 sensitization, QC is cleanly converted to NBD while NBD is not affected.The calculation shows QC+* possesses higher energy than NBD+* by 7.5 kcal/mol, hence an irreversible rearrangenment.Other sensitizers (e.g., cyanoaromatics and tetrachlorobenzoquinone) also promote these cation radical reactions but not as cleanly as DBMBF2. Key words: photosensitization by boron complexes, cation radical rearrangement, cation radical cycloaddition, electron transfer sensitization, photoreaction of ground state complexes.
- Chow, Y. L.,Cheng, Xianen
-
p. 1331 - 1336
(2007/10/02)
-
- Electron Transfer Induced Photoisomerization, Dimerization, and Oxygenation of trans- and cis-Anethole. The Role of Monomer and Dimer Cation Radicals
-
Irradiation of trans- or cis-anethole in the presence of electron acceptors results in cis,trans isomerization, cyclodimerization, and (in the presence of oxygen) oxidative cleavage.The initial step in each of these reactions is photoinduced electron transfer to yield a singlet radical ion pair.Anethole cation radicals are the initial reactive intermediates formed in each reaction.Isomerization occurs via reverse electron transfer to generate triplet anethole which decays to a mixture of cis and trans isomers.Dimerization occurs via the cycloaddition of a cation radical and a neutral which proceeds with retention of olefin configuration to yield a mixture of syn and anti head-to-head dimers.The syn/anti dimer ratio is sensitive to reaction conditions because of the lower stability of the syn vs anti dimer cation radical.Reaction of the monomer cation radical with O2- or O2 results in formation of p-anisaldehyde.It is unlikely that an acyclic 1,4-cation radical is the precursor of any of the observed products.
- Lewis, Frederick D.,Kojima, Masanobu
-
p. 8664 - 8670
(2007/10/02)
-