- Reactions of Ethoxycarbonylmethylene(triphenyl)phosphorane with some ortho-Quinones in the Presence of Triphenylphosphine, Alcohols and Acetic Anhydride
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The reactions of ortho-quinones 1a, 1c and 1d with ylide 2 in the presence of triphenylphosphine afforded the ylides 11a, 11c and 11d and compound 12.The reactions of 1a and 1c with 2 in refluxing methanol or ethanol gave compounds 16 and 17 respectively, while the reactions of 1a-d with 2 in acetic anhydride yielded the acetates 18a, 18b, 18d and 19b, 19d, the furan derivative 24 and the ylide 25.Compounds 8 and 9 were also obtained in most of the above reactions.Wittig reactions of the ylides 11a, 11c with p-nitrobenzaldehyde and of ylide 2 with coumarins 8a and 29 resulted in compounds 14a, 14c, 26 and 30 respectively.The transformations of compounds 18, 19 into 8, 9 as well as of compound 26 into 28 were also studied.
- Nicolaides, Demetrios N.,Adamopoulos, Spyros G.,Lefkaditis, Demetrios A.,Litinas, Konstantinos E.,Tarantili, Petroula V.
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p. 283 - 290
(2007/10/02)
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- Reactions of ortho-Quinones with Ethoxycarbonylmethylene(triphenyl)phosphorane. Trapping of the ortho-Quinone Methanide Intermediates
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The reactions of the ortho-quinones (5a-d) with the phosphorus ylide (6) afforded, besides the expected coumarin derivatives (10a-d), compounds (9d), (11b and c), (13), and (14).When the reactions between compounds (5a-d) and (6) were carried out in the presence of ethyl vinyl ether (20) the pyran derivatives (21a, b, and d) and (22a, b, and d) were obtained as main products, by a trapping process of the ortho-quinone methanide intermediates (7a, b, and d) with the dienophile (20).Similarly, the reaction between compounds (5a) and (6) in the presence of α-methylstyrene afforded mainly the pyrans (23I and II).Compounds (16), (19), and (24) were also prepared and studied.
- Nicolaides, Demetrios N.,Adamopoulos, Spyros G.,Lefkaditis, Demetrios A.,Litinas, Konstantinos E.
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p. 2127 - 2132
(2007/10/02)
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- Push-Pull Substituted Allenes, IV. Synthesis and Properties of o-Quinoid Donor/Acceptor Substituted Allenes. Crystal- and Molecule Structure of E-2,2,2',2'-Tetraethoxy-Δ3,3'(2H,2'H)-bifuran>
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Reaction of the (2,2-diethoxyvinylidene)triphenylphosphorane (7) with the o-quinones 6 yields the donor/acceptor allene intermediates 9 via the oxaphosphetanes 8.The allenes 9 give the carbenes 10 which then spontaneously dimerize forming the olefins 11.T
- Saalfrank, Rolf W.,Ackermann, Erich,Winkler, Herbert,Paul, Winfried,Boehme, Reinhild
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p. 2950 - 2958
(2007/10/02)
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