83845-54-9Relevant academic research and scientific papers
Lithium Dialkylamide Induced 1,4-Elimination of Methyl o-Methylbenzyl Ethers: Formation and Reactions of o-Xylylenes
Tuschka, Theodore,Naito, Katsuyuki,Rickborn, Bruce
, p. 70 - 76 (2007/10/02)
Lithium dialkylamide induced 1,4-elimination is shown to be a general reaction of methyl o-methylbenzyl ethers, giving o-xylylenes as reactive intermediates.The fate of the intermediates depends on a variety of factors including the base used, the dienophile employed as solvent, or the presence of a suitable located double bond in the substrate.With lithium diisopropylamide (LDA), a significant reaction forms the amine derived from 1,4-addition to o-xylylene.The use of lithium tetramethylpiperidide (LTMP) avoids this addition and allows the study of in situ generated o-xylylene in intermolecular Diels-Alder reactions with simple olefins, where dimerization/polymerization is the major competing pathway.Yields of Diels-Alder adducts range from negligible (cyclohexene) to high (norbornene), with 1-hexene, isoprene, and cyclopentene giving intermediate values.Intramolecular Diels-Alder reactions to form six- and five-membered rings proceed well but are not observed for lower homologue.Second-order rate constants have been obtained for the elimination reaction of some of the substrate ethers, and the effects of structure and temperature on yields of cycloadduct are examined.LTMP is about twice as reactive as LDA in these 1,4-eliminations.
Photochemistry of (o-Methylphenyl)alkadienes: Attempted Intramolecular Trapping of the Resulting o-Xylylenes
Hornback, Joseph M.,Barrows, Russell D.
, p. 90 - 98 (2007/10/02)
The photochemistry of a series of o-methylphenyl dienes was investigated in order to determine if the resulting o-xylylenes could be trapped in an intramolecular Diels Alder reaction in synthetically useful yields.Irradiation of 3 gave meta-isomer 4 as the major product along with lower yields of double bond migration product 5 and the desired cycloadduct 6.The best yield of 6 (24percent) was obtained by irradiation of 3 with a low-pressure mercury vapor lamp at low temperatures.The other compounds investigated gave none of the intramolecular Diels-Alder product of the o-xylylene.Irradiation of 17 gave only double bond migration product 18.Irradiation of 22 gave an excellent yield of (2+2) cycloadduct 23.Irradiation of 26 gave meta-isomer 28, double bond migration product 27, and 29, a (2+2) cycloadduct of 28.
