Title: Formation of 3-Methylene-1,4-cyclohexadienes from<i>α</i>,<i>α</i>,<i>α</i>′,<i>α</i>′-Tetraaryl-1,4-benzenedimethanols by the Intramolecular Migration of an Aryl Group
Abstract:Abstract By reactions of diethyl p-phthalate with 2,6-dimethoxyphenyllithium, ΦLi, a tri-substituted compound, p-HOCΦ2C6H4C(O)Φ (1), or tetra-substituted 1,4-benzenedimethanol, p-HOCΦ2C6H4CΦ2OH (2a), ...Abstract By reactions of diethyl p-phthalate with 2,6-dimethoxyphenyllithium, ΦLi, a tri-substituted compound, p-HOCΦ2C6H4C(O)Φ (1), or tetra-substituted 1,4-benzenedimethanol, p-HOCΦ2C6H4CΦ2OH (2a), were obtained. Compound 1 further reacted with aryllithium, ArLi, to give the 1,4-benzenedimethanols, p-HOCΦ2C6H4CArΦOH (Ar = 4-MeC6H42b, 4-MeOC6H42c). When 2a was treated with acid in dimethyl sulfoxide, 3-(2,6-dimethoxybenzoyl)-3-(2,6-dimethoxyphenyl)-6-[bis(2,6-dimethoxyphenyl)methylene]-1,4-cyclohexadiene, (4a) was obtained in quantitative yield under a variety of conditions. The reaction is understood to involve an initial formation of carbenium ion, [p-Φ2C+–C6H4CΦ2OH] (3a), of which the positive charge must be partly shared with the other end of the p-phenylene ring, where one of the neighboring Φ-groups migrates. Reactions in acetone resulted to give 4a or dark-violet crystals of (2′,6′-dimethoxy-4-biphenylyl)bis(2,6-dimethoxyphenyl)carbenium perchlorate, [(4-ΦC6H4)CΦ2]ClO4, depending on the reaction conditions. Reactions in methanol, ethanol, or in hot 2-propanol resulted to give the reduced compound, (4-ΦC6H4)Φ2CH. The 1,4-benzenedimethanols, 2b and 2c, also reacted with perchloric acid in dimethyl sulfoxide to form the 3-methylene-1,4-cyclohexadiene derivatives, (Ar = 4-MeC6H44b, 4-MeOC6H44c), respectively. Evidence is given by the 1H NMR spectrum, which shows the formation of intermediate carbenium ions 3a—c.Read More
Publication Year: 1997
Publication Date: 1997-06-01
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 5
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